Figure 6. Block diagram connectivity setup for signal generator with FES extension module.

Instrumentation for millimeter wave tests and measurements

By Tomasz Waliwander, Michael Crowley, Courage Mudzingwa (Farran Technology) There has been a vast research effort and academic development in the past three decades in millimeter wave (mm-wave) technology. Such an effort has been corresponding steadily in the growth in customer demand for mm-wave components and systems which has in turn created a need for a cost-effective test and measurement solutions for high frequency applications. There is a large number of test instrumentation already available in the field as well as new developments coming on-stream to the engineers ranging from signal generators, spectrum analyzers to network and noise figure analyzers to choose from to fulfill test and evaluation duties. The choice of instrumentation as well as ways of extending their measurement capabilities will be discussed in this article. Introduction Millimeter waves are electromagnetic signals with frequencies ranging from 30 to 300 GHz that correspond to wavelengths of 10 to 1 mm in the free space. Such signals in natural atmosphere environment are susceptible to attenuation at different rates for different wavelengths (frequencies) which makes them very useful in specific applications. The atmospheric attenuation of mm-waves is caused by gases and constituents that naturally occur in the environment. The atmospheric attenuation characteristic from 10 GHz to 1 THz under various levels of humidity [1] (large H2O droplets) and fog (small H2O droplets) is shown in Figure 1 : Figure 1. Atmospheric attenuation characteristic from 10 GHz to 1 THz. Frequencies where the average absorption of mm-waves is the lowest are called low attenuation windows and occur mainly around 35, 77 and 94, 140, 220, 340, 410, 650 and 850 GHz. The regions with highest averaged absorption levels are called attenuation lines and can be seen around 22, 60, 118, 183, 320, 380, 450, 560, 750 GHz. It is the oxygen molecules that are responsible for high attenuation at 60, 118 and 560 and 750 GHz. The rest of the attenuation lines are caused mainly by water droplets of various diameter sizes as well as other chemical species (CO2, N2O, NO, SO2 and SH2) at submillimeter wavelengths. Due to different properties of mm-waves at different frequencies and environmental conditions the applications of mm-waves vary largely from communications, imaging and security applications, radar, radiometry and atmospheric sensing. All the applications mentioned, at some stage of their development, need to employ a mm-wave measurement system for component and system level testing and evaluation. 1.1 Mm-wave Applications The mm-wave applications correlate closely with how such signals propagate in the atmosphere. The frequencies for which atmospheric attenuation is low (44, 86, 94, 140 GHz) are particularly useful in communication system operating at long ranges such as: satellite communications, backhaul mm-wave radios and point to multi-point radio links. For short range communications the 60 GHz band provides enough range where only a local area, short distance transmission is required. Other application benefiting from low atmospheric attenuation would include automotive radars at 24, 77 and 94 GHz where a long-range transmission and reception is possible [2]. Imaging and security utilize a mixture of high and low attenuations bands for passive and active systems. These use 77, 94 and 183 GHz frequencies as these signals present good properties to penetrate many materials (i.e. clothing) and see through the fog and rain. For those materials that can not be penetrated the atmospheric environment provides a good thermal contrast from which images can be synthesized at post processing level (see Figure 2). Figure 2. Typical human body image obtained with mm-wave imaging system. Other applications include scientific research as well as radiometry and ground-based astronomy. These applications would mainly concentrate at 183 and 220 GHz as well as higher frequencies. Rectangular waveguide due to its inherently low loss properties is the medium that is most frequently used in mm-wave applications. Under normal conditions the electromagnetic field propagates through the waveguide in transverse electrical dominant mode TE10 and has a cut off point below which it does not propagate in any form or mode. Millimeter wave waveguide bands are shown in Table 1 and contain band designation, internal waveguide dimensions as well as cut off frequency. 1.2 Mm-wave Frequency Extensions The mm-wave frequencies can be generated in general using two methods: up conversion by means of solid-state devices such as Schottky diodes, or down conversion using optical and quasi optical methods. It is the former method that is used predominantly in millimeter wave range and thus will be discussed here. The mm-wave signals are created with either multiplying or mixing lower frequency signals (<30 GHz). This is achieved by using active (requiring DC biasing) MMIC based multipliers or mixers at the lower end of mm-wave band (<80 GHz typically) and devices built with Schottky diode devices for higher end of mm-wave spectrum. To reach frequencies beyond 110 GHz harmonic mixers (mixers utilizing a nth harmonic of the LO signal) or chain of multipliers (lower frequency modules driving the input of higher frequency ones – i.e. a doubler driving a tripler) are most commonly used. Due to conversion efficiency constraints in general those devices would be limited to doublers and triplers only. Most commonly purchased and used test and measurements instruments operate below 20 GHz. Such operating range is adequate to fulfill the evaluation and test purposes in most cases. However, with the advent of mm-wave applications, more so than ever before, there is a need for measurement systems operating at frequencies above 20 GHz and very often beyond 110 GHz. Such systems in principle are thought to extend the range of standard instruments beyond their range by means of frequency multiplication or mixing. In general, there are 4 groups of test and measurement equipment commonly used in component and system evaluation by engineers. These include: signal generators, spectrum and signal analyzers, vector network analyzers and noise figure analyzers. 1.2.1 Signal Generators Frequency Extension Sources – FES In most cases the mm-wave users already own a microwave signal generator that are capable of supplying frequencies up to

Introduction to RF Power Noise Amplifiers

By Gibin Bose, Design Engineer at Farran Technology RF power amplifiers (PA) is a type of electronic amplifier that is used to increase the power level of radio frequency signals. In a typical radio transmitter (see Figure 1), RF power amplifier is present at the final stage, its output driving the antenna, and is responsible for the crucial task of amplifying the RF signal to the required power level for free space transmission. Radio transmitters are used in transmitting information over a distance in several applications including satellites, mobile communication, collision avoidance, Internet of Things (IoT), weather forecast, radars and so on. The increasing demand to transmit more information in a limited bandwidth coupled with the requirement of high efficiency of transmitters pose a serious challenge to RF engineers. Modern communication systems mostly use signals containing both amplitude and phase modulation and linear amplification is a necessity in these systems to avoid distortion and adjacent channel interference. Power amplifiers with high saturated output power (Psat), efficiency and good linearity play a critical role in the design of radio transmitters with high efficiency, longer physical range and good linearity. RF power amplifiers are implemented using transistors that operate in the linear region and based on how much of the cycle of the sinusoidal radio signal the given transistor is conducting, they can be classified into different classes (A, B, AB, C, D, F, G, I). Additionally, in the recent years to meet the increasing demands of higher output power, efficiency, and linearity, amplifier designers are utilizing various techniques including envelope tracking, digital predistortion, load modulation and dynamic biasing. Move towards GaN technology over silicon in transistors is also serving the purpose of higher power density, efficiency, higher temperature tolerance, reduction in size and wider bandwidth capabilities. Critical Figures of Merit Saturated output power, efficiency, linearity, gain, bandwidth, return loss and heat dissipation are some of the critical parameters of an RF power amplifier. Saturated Output Power (Psat): Saturated output power of an amplifier is the maximum output power amplifier can provide under the fixed recommended operating considerations of the amplifier. Efficiency: Efficiency of a power amplifier is commonly expressed either using power added efficiency () or drain efficiency. Power added efficiency is the ratio of added RF power to DC supply power expressed in percentage, Drain efficiency is the ratio of output RF power to DC supply power expressed in percentage, Higher saturated output power and efficiency of an amplifier plays a key role in extending the maximum range of transmitters and limiting the power consumption requirements of systems where these amplifiers are used. Gain: The primary function of an amplifier is to increase the amplitude of the signal at its input and this increase in the signal amplitude is quantified by gain. Gain, usually measured as small signal gain is the ratio of the output power to input power expressed in dB in the linear region of operation and under fixed recommended operating conditions for the amplifier. Return Loss: Return Loss () of an amplifier is the measure of the ratio of the incident to reflected power at either port expressed in dB. where Pi is the incident power and is the reflected power. Linearity: An amplifier provides a constant gain until a specific input power level and then there would be drop in gain resulting in compression effect i.e. the amplifier output power starts to saturate. The one dB compression point (P1dB) is the power level (input/output) where the gain is 1dB lower than the small signal gain. Beyond the P1dB point, amplifier becomes a non-linear device and can produce distortion, harmonics and intermodulation products. Farran offers a broad range of standard and custom-built power amplifiers over the frequency range of 18 GHz – 250 GHz. Access our website for more details and to contact us

Introduction to Low Noise Amplifiers

By Gibin Bose, Design Engineer at Farran Technology Low noise amplifier (LNA) is a critical component of radio communication systems, electronic test equipment and RF receiver systems such as those found in mobile communication, GPS systems, satellites, radars and other applications. Being the first active circuit in the receiver chain following the antenna (see Figure 1), figures of merit of LNA such as noise figure, gain, linearity and input VSWR play a crucial role in determining the noise performance, linearity and VSWR of the overall system and sensitivity of the receiver. Figure 1. A conceptual diagram of RF front end The main purpose of a low noise amplifier is to amplify the low power RF signals from the antenna to an appropriate power level required by subsequent stages while introducing minimal additive noise. It should be noted that any RF amplifier increases the power level of both the signal and noise present at its input by the same amount and also introduce some additional noise. Keeping the level of this added noise to a minimum is crucial in preserving the integrity of the received information and optimal retrieval of the desired signal in the later stages of the system. With increasing demands, more stringent constraints on performance, size and cost, development of newer technologies and push towards higher operating frequencies, LNA designs are being rolled out with higher goals as well. For example, in cellular phone designs in order to reduce the battery consumption, current drain has to be reduced as much as possible so that the standby current of the overall receiver is low. At the same time, devices must be kept small, cost effective and high performing as well, rendering the LNA design process more complicated. In addition to satisfying the demands of high gain and low noise figure, LNA’s exhibiting high dynamic range, linearity and good input and output matching are critical in modern communication systems. In communication systems using Code-Division Multiple Access (CDMA), LNA’s taking care of automatic gain control is important as well for the entire system to operate well. For instance, in mobile applications where the path loss from the base station to phone can alter, input signal strength at the receiver varies and automatic gain control becomes crucial in this kind of scenarios. Critical Figures of Merit and Functions Gain: The primary function of a low noise amplifier in the RF front end is to increase the amplitude of the low power signal at the input with minimal signal to noise ratio degradation and this increase in the signal amplitude is quantified by gain. Gain, usually measured as small signal gain is the ratio of the output power to input power expressed in dB in the linear region of operation and under fixed recommended operating conditions for the amplifier. Noise Factor, Noise Figure, Noise Temperature: In the receiver system, noise added by the amplifier degrades the received signal by degrading the signal to noise ratio. Noise factor, noise figure and noise temperature are different ways of quantifying this degradation. Low noise amplifier in the receiver system plays the crucial role of amplifying the input signal with minimal signal to noise degradation and thereby preserving the integrity of the received information. Noise Factor (F) is the ratio of signal to noise ratio at the input to the signal to noise ratio at the output, where Sin and Nin represent the input signal and noise powers respectively and Sout and Nout , output signal and noise powers respectively. The input termination here is assumed to be at standard noise temperature T0= 290 K and noise of input signal, Nin = kT0B, where k is the Boltzmann’s constant and B is the noise bandwidth. Noise Factor expressed in dB provides the Noise Figure (NF), where F is the noise factor. It should be noted that the output signal to noise ratio is never higher than the input signal to noise ratio and hence F>1 . For a noiseless system, we have, F=1 or NF=0 dB. We can also use effective input Noise Temperature (Te) to describe the noise performance of a device. If the gain of the device is denoted by G, we have Sout=GSin and Nout=Gk(T0+Te)B and from the definition of Noise Factor So, we have the effective input noise temperature (Te) related to the noise factor as below, where T0=290 K. Effective input noise temperature of an amplifier can be described as the equivalent noise temperature of a source when connected to a noise-free device that would produce the same output noise as of the amplifier when connected to a noise-free source. Return Loss: Good input and output matching is crucial in the design of LNA’s as it minimize signal loss and helps in efficient power transfer between antenna and subsequent stages. This can be quantified by the return loss of LNA which is a measure of the ratio of the incident to reflected power at either port expressed in dB. Return Loss (RL(dB)) can be expressed as below, where Pi is the incident power and Pr is the reflected power. Linearity and Dynamic Range: An amplifier provides a constant gain until a specific input power level and then there would be drop in gain resulting in compression effect i.e. the amplifier output power starts to saturate. The one dB compression point (P1dB) is the power level (input/output) where the gain is 1dB lower than the small signal gain. Beyond the P1dB point, amplifier becomes a non-linear device and can produce distortion, harmonics and intermodulation products. In the cases when a strong RF signal arrives at the antenna, in order to avoid overloading the circuit and leading to distortion, high linearity of LNA’s become crucial. Dynamic range of a device is the ratio of the highest signal level it can handle to the lowest signal level it can handle. It should be noted that the highest signal level is usually limited by distortion which can be characterised by P1dB whereas on

What is a Sub Harmonic Mixer?

By Hugh Hancock, Senior Design Engineer at Farran Technology Sub Harmonic mixers (SHM) can be considered a sub-set of the Harmonic mixer category. They are designed to work using the second harmonic of the applied local oscillator (LO) to mix with the radio frequency (RF) signal to create an intermediate frequency (IF). The mixing relationship is governed by Equation 1. IF=RF±(2×LO) Eq.1 Figure 1 Sub harmonic Mixer configured as downconverter This type of mixer is commonly used in the millimeter wave region for applications such as radiometric sensors/receivers for ground-based astronomy, atmospheric sensing and imaging/radar systems [1-3]. There are currently discussions surrounding 6G and use of wide bandwidth communication systems in the sub-THz spectrum and the sub harmonic mixer has the potential to be a key enabler of this technology [4-7]. To understand the properties that the sub harmonic mixer offers it is beneficial to look at the basic diode configurations. Single-Diode Struggles Figure 2 shows the simple single Schottky diode configuration and requisite combination of bandpass (BPF) and Low-pass filters (LPF) for sub harmonic mixing. Figure 2 Downconverter SHM using single diode In the downconverter configuration the RF and LO signal are applied to the mixer. Figure 3a shows the voltage across the diode which is given by Equation 2. Of these two voltages applied to the diode, VLO will be greater in magnitude than VRF and is said to “pump” or “drive” the diodes. V=VLOsin(ωLOt) + VRFsin(ωRFt) Eq. 2 The single diode I-V characteristic is shown in Figure 3b. As the applied VLO voltage pumps the diode it drives it into forward conduction and the diode turns on. Similarly, when the applied voltage goes negative, the diode turns off. This relationship between the applied LO voltage and the diode’s I-V curve is given by the conductance in Figure 3c. Figure 3 Single Diode Mixer a) Circuit b) I-V curve c) Conductance curves. Adapted From [8] When a single diode is driven in this manner the output current, I, contains all combinations of mixing products mfLO±nfRF where m & n are integer values [8]. This indicates the single diode will work as subharmonic mixer as the 2fLO±1fRF mixing term is present. However, it is also more likely that the fundamental frequency mixing response, 1fLO±1fRF, will be more influential than that of the second harmonic and subsequently cause inteference at the IF [9]. A secondary concern of the single diode mixer is certain RF signal mixing products could appear within the LO BPF passband response. This will allow signal to propagate out of the LO port and increases conversion loss. An example of this undesirable mixing response is shown in Figure 4; the yellow mixing product are able to escape out the LO port. Figure 4 Single Diode Fundamental Interferers Double the diodes…halve the harmonics? To improve upon the single diode mixer the well-known anti-parallel pair is exploited, this is given in Figure 5a. This topology presents a symmetric I-V curve to the to the applied voltage as indicated by Figure 5b. Figure 5 Anti-Parallel Pair a) circuit b) I-V Curve c) Conductance curves. Adapted from [8] Now, irrespective of the applied voltage polarity one of the two diodes will be forward biased and conducting. When lookin at the total combined conductance of the two diodes given in Figure 5c, it is easy to see how a second harmonic response is produced from the LO. This diode configuration leads to the generation of a circulating current, IC, as indicated in Figure 5a. This circulating current is generated by the individual currents from each diode, I1 and I2. These currents have certain harmonic and frequency mixing components that are opposite in phase and will cancel when combined to generate the external current, I. These frequency components that cancel out externally are governed by relationship mfLO±nfs where m+n=even integer. These constitute the DC component, fundamental/odd harmonic mixing products and even harmonics of the LO [8]. The supression property of the anti-parallel pair is predicated on there being a good electrical property match between the diodes. As these frequency components cancel out they will be attenuated externally to the anti-parallel pair and will therefore be minimized at the outputs of the mixer. A representative example of this is shown in Figure 6; the red components indicate a signal that will be attenuated whereas the black components are not. Figure 6 Spectrum showing suppressed and unsuppressed mixing products from SHM The anti-parallel pair is therefore able to improve conversion loss of subharmonic mixing by supressessing the fundamental mixing products whilst also reducing filtering requirements at the output. This anti-parallel pair improvement brings the conversion loss of a well designed sub-harmonic mixer to a comparable value provided by fundamental mixers. There are other benefits to this topology as it can also lower the LO AM noise as well as provide protection against large peak voltages. [8,10] mmWave Sub harmonic Mixers The subharmonic mixer uses an applied LO of half the RF frequency and while this is applicable at any frequency this becomes particularly useful in the mm- and sub-THz bands; where generating an LO for a fundamental mixer is challenging. Sub harmonic mixers at mmWave frequencies will commonly utilise waveguides as they have superior performance for insertion loss over microstrip. Figure 7a and 7b show a sub harmonic mixer with a WR-12 waveguide at the RF port covering 60-90GHz and an WR-22 waveguide covering 30-45GHz for the LO port, the IF port is typically and SMA or K-type connector. Figure 7 WR-12 sub harmonic mixer a) Block diagram b) Physical unit with waveguide ports Using a waveguide to interface to the diodes is beneficial not only from an insertion loss perspective but as they also have a lower frequency cut-off, the fundamental or TE10 mode is not supported thus making them a low-pass filter. Figure 8a shows the E-fields at 30GHz in a WR-12 waveguide and it is clear that it is not

What are Communication Extenders?

By Courage Mudzingwa, Applications Engineer at Farran Technology Millimeter-wave (mm-wave) technology has emerged as a critical enabler in the evolution of wireless communication systems, particularly in the context of 5G and the forthcoming 6G networks. One of the key components driving the enhanced performance of RF signal analysis systems is the mm-wave Communication Extender (Up/Down converter). mm-Waves refer to radio waves with frequencies ranging from 30 to 300 GHz, falling within the high-frequency spectrum. Leveraging these higher frequencies provides several advantages, including increased data rates, lower latency, and the ability to support a massive number of simultaneous connections. However, the utilisation of mm-wave frequencies also poses unique challenges, such as increased atmospheric absorption and limited propagation distances. Architecture of Communication Extenders The mm-wave communication extenders serve as a crucial bridge between lower frequency signals and the higher frequency mm-wave spectrum. Communication extender architecture comprises of two main components: the up-converter, which translates lower frequency signals to the desired mm-wave frequency, and the down-converter, responsible for converting mm-wave signals back to lower frequencies for analysis and processing. These up/down converters play a pivotal role in facilitating seamless communication between the radio frequency (RF) and mm-wave domains. The architecture of mm-wave up/down converters encapsulates a sophisticated blend of amplification, mixing, filtering, and conversion technologies, as shown in Figure 1 below. Figure 1: Farran’s FEC-XX communication extender architecture (simplified). As the demand for higher data rates, lower latency, and increased spectral efficiency continues to drive the evolution of wireless communication, the refinement and innovation in the architecture of communication extenders will remain crucial for the success of future communication systems. The intricate dance of up-conversion and down-conversion within these frequency extenders exemplifies the pinnacle of engineering prowess, enabling the seamless integration of mm-wave frequencies into the fabric of modern wireless communication, particularly fortifying the foundations of 5G networks and laying the groundwork for the much-anticipated advancements in 6G communication systems. Technology Behind mm-Wave Communication Extenders The design of mm-wave communication extenders involves state-of-the-art technologies to ensure maximum performance and interoperability. Advanced semiconductor technologies, such as gallium nitride (GaN) are often employed due to their superior high-frequency characteristics. Additionally, innovative packaging techniques and advanced heat dissipation methods, are crucial to addressing the thermal challenges associated with mm-wave frequencies. Applications of Communication Extenders in 5G Communication In the realm of 5G networks, mm-wave communication extenders, featuring advanced up/down converters, are pivotal for achieving higher data rates and ultra-low latency. Deployed within mm-wave bands such as 24 GHz, 28 GHz, and 39 GHz, these extenders efficiently translate signals between RF and mm-wave frequencies, enhancing capacity and spectral efficiency for diverse 5G use cases. Beyond traditional mm-wave up/down conversion, communication extenders play key roles in: 5G network emulation/simulation, Beamforming algorithm development Antenna array verification Software-Defined Radio (SDR) applications Communication extenders facilitate realistic testing environments, optimise beamforming techniques, and serve as crucial interfaces in SDR experiments, contributing to the evolution of wireless communication. Figure 2 shows a typical setup for 5G network simulation with Farran’s FEC-XX communication extenders and SDR. Figure 2: SDR based 5G network emulation with Farran FEC -XX communication extenders Significance in 6G Communication Test-Beds Looking ahead to 6G, mm-wave communication extenders maintain their forefront position. As higher frequency bands, including terahertz (THz) frequencies, pose challenges and opportunities, communication extenders become essential in developing and testing the next generation of communication systems, acting as crucial components in 6G test-beds. Their adaptability across various 5G scenarios underscores their significance in shaping the future of wireless communication technologies. Conclusion In conclusion, the evolution of mm-wave technology, coupled with the advancements in up/down converter design, has significantly contributed to the success of 5G networks. Communication extenders not only facilitate the deployment of mm-wave frequencies but also play a vital role in reducing time to market and costs for mobile operators and system integrators. As we set our sights on 6G, the continued development and refinement of mm-wave communication extenders will be instrumental in shaping the future of wireless communication systems.

Unlocking the Potential of 5G Satellite Spectrum Monitoring

By Courage Mudzingwa, Applications Engineer at Farran Technology The escalating demand for bandwidth-intensive services underscores the urgency of maximizing spectrum efficiency while minimising interference. This is where spectrum monitoring and management step in, allowing operators and regulators to monitor signal performance and optimise spectrum utilization. Satellite operators have strategically adopted Q band (33 – 50 GHz) and V band (40 – 75 GHz) links for two key purposes: deploying Very High Throughput Satellites (VHTS) and bolstering cellular broadband networks. VHTS systems, specifically tailored for direct-to-home (DTH) internet access, make efficient use of the Q/V bands for feeder uplink and downlink communications. This reserved utilisation of the Ka band is geared toward serving end users, with the ultimate aim of substantially boosting user bandwidth, potentially by a factor of ten. The mounting congestion in traditional lower-frequency bands, combined with concerns about regulatory spectrum reallocation for 5G, has prompted a migration to higher-frequency bands like Q/V. These bands offer not only available spectrum but also significantly enhanced data throughput, presenting a promising opportunity. Figure 1: Satellite earth station Spectrum management has a clear goal: to maximize spectrum efficiency, minimize interference, and eliminate unauthorised spectrum use. Spectrum monitoring acts as a key enabler in this process. Key Objectives of Satellite Spectrum Monitoring Satellite monitoring primarily serves two critical objectives: (a) Evaluating Satellite Resource Utilization: By monitoring and analysing resource usage, satellite operators can identify opportunities for optimising their spectral efficiency, minimising interference, and ensuring the best possible service quality for end-users. (ii) Detection and Resolution of Interference: Whether it’s intentional or unintentional radio frequency interference (RFI), identifying and locating problematic sources is vital in improving the reliability of satellite communications. For years, satellite communications predominantly relied on Ku/Ka frequency bands, which are now saturated. This saturation, coupled with the complexities of frequency coordination and the insatiable need for communication capacity and bandwidth, has prompted satellite operators to venture into higher-frequency bands. The Q/V bands, in particular, provide a breath of fresh air, potentially offering more than double the available bandwidth compared to Ka-band resources. Additionally, Q/V bands present alternative gateway frequencies, relieving the pressure on existing Ka-band arrays. The satellite industry has a history of spectrum sharing, but the surging demand for broadband connectivity has magnified the challenges associated with interference mitigation and spectrum monitoring. Empowering Spectrum Monitoring with Farran To meet the demands of commercial operations in the Q and V bands, mm-wave spectrum monitoring solutions are essential. Enter Farran, a reputable Irish provider of standard and custom systems, sub-systems, and components for Test & Measurement and Research Applications. Farran’s expertise in Test & Measurement frequency extension systems, including the spectrum/signal analyser (SAE) frequency extension solutions and harmonic mixers, is invaluable for businesses operating in the satellite spectrum monitoring and management industry, whether they are in the early developmental stages or fully operational. As we navigate the complex landscape of spectrum management, satellite spectrum monitoring supported by cutting-edge technology from companies like Farran, becomes the linchpin in the quest to optimise spectrum usage, reduce interference and ensure a seamless experience for users of bandwidth-intensive services. Farran’s Spectrum Analyser Frequency Extension Solution (SAE) Farran’s SAE is a family of frequency extension modules used for extending the range of RF/Microwave spectrum and signal analysers such as PXA, MXA, UXA and EXA equipped with external mixing option, to frequencies ranging from 50 GHz to 500 GHz, in waveguide bands from WR-15 to WR-2.2. These extender modules offer a full band coverage and a very low system conversion loss, as well as an exceptional sensitivity. Depending on the type of the spectrum/signal analyser used, the SAE modules can be configured to operate with low or high LO frequency signals supplied by the analyser in an IF range of 10 to 2200 MHz Farran’s SAE come with a dedicated AC/DC power supply that provides the required voltage and meets the maximum current requirements of each extender in the SAE family. Fig 2 depicts a typical satellite monitoring system with Farran’s SAE. Figure 2: Typical satellite monitoring system block diagram SAE Modes of Operation Farran’s Spectrum Analyser frequency extension modules can also be configured to operate as block up- and down-converters. Figure 3 summarises the SAE-XX modes of operation. Figure 3: Farran’s SAE modes of operation In this mode, similar to a standard harmonic mixer but with much improved performance, the module is used to extend the operational range of commercially available spectrum/signal analysers. The analyser’s swept internal LO source is used to drive the extension module while the spectral data analysis is performed at a fixed IF frequency by the analyser. In this mode, the module requires an additional swept LO signal source that allows for down-conversion of a block of the RF signal spectrum to an intermediate frequency range within the IF bandwidth of the module. Such signal is supplied to the RF input of the analyser that performs data processing. By varying the LO signal frequency different blocks of frequencies of the RF operational bandwidth can be analysed. In this mode the unit up-converts the block of intermediate frequency IF signals to the block of RF signals in the RF operational frequency of the SAE module. The external LO synthesiser is used to drive the SAE module. The up-converted frequency block is generated at both lower- and upper-sidebands of the effective LO frequency, and external filters and amplifiers can be further used to condition such generated RF signals. mm-Wave Harmonic Mixers (WHMB) Harmonic mixing stands as the predominant technique for extending frequency coverage beyond 40 GHz in mm-Wave spectrum analysis. Most spectrum analyser manufacturers have tailored their instruments to seamlessly incorporate external mm-Wave harmonic mixers. These mixers excel at upconverting the signal by generating higher harmonics, thereby enabling the analysis of frequencies in the Q/V bands and beyond. By harnessing the capabilities of harmonic mixers, spectrum analysers can effectively evaluate the performance of Q/V band satellite transponders, gauge signal quality, and pinpoint issues like interference or signal degradation. This capacity is

What are the different types of frequency extenders?

By Tomasz Waliwander, Chief Executive Officer at Farran Technology In the Test & Measurement field, there are three different types of frequency extenders. These include devices such as multipliers and mixers, and systems made from a combination of both. They have been described in more detail in ‘What is a Frequency Extender’. When it comes to the type of the equipment and applications for which frequency extenders are employed, there are five different types: Signal Generator Extenders. This group of signal generator extenders relies on a frequency multiplication as a principle of frequency conversion. In such devices, the output signal frequency is an integer harmonic (multiple) of the input frequency i.e. FOUT = N x FIN. A frequency extender operating based on that principle, can extend the frequency of a signal generator or any other frequency source by a fixed multiple. This multiple is also called a multiplier number and is determined by a type and number of cascaded multiplier devices that it consists of. A typical multiplier number can be as low as 2 and as high as 30 or higher. Higher order multipliers / extenders are achieved by cascading low order multipliers such as doublers (x2), tripplers (x3), quadruplers (x4) and quintuplers (x5). Spectrum & Signal Analyser Extenders. These types of extenders operate on a principle of heterodyne mixing, in which the local oscillator signal (LO) is mixed with an input radio frequency signal (RF) to produce an intermediate frequency signal IF i.e. IF = RF ± LO, which is then used by the baseband analyser for spectrum and signal analysis. In its simplest form, a frequency extender in such an application could be a stand-alone harmonic mixer. Devices like these often operate with at a multiple of a LO signal that is supplied by the analyser to produce the IF frequency in accordance with a formula IF = RF ± N x LO, where N = 1, 2, 3 … A typical diagram of a spectrum & signal analyser extender is shown in Figure 2: Such mixers, although simple and relatively inexpensive, suffer from a high conversion loss that is associated with operating at a high number of LO harmonic. For cases and applications where combined sensitivity of the test equipment is of primary importance, more complex extender systems are required. Such extenders are aimed at achieving the lowest possible noise floor and preserving the sensitivity of the analyser, and typically are equipped with fundamental or sub-harmonic mixers which operate at the LO harmonic number of 1 and 2, respectively. These systems offer much lower conversion losses in comparison with their harmonic counterparts and are more suited to applications where the measurements require much higher order of fidelity i.e. radar signals, wireless communications etc. This is often achieved at the expense of additional LO multipliers that have to be used to provide the frequency and power for fundamental or sub-harmonic mixers. Vector Network Analyser Extenders. This type of frequency extenders is designed to work with vector network analysers (VNAs) to measure complex scattering parameters (S-parameters) at frequencies that stretch beyond the standard range of the analyser. They are aimed at preserving the measurement precision and maximising the dynamic range and stability of the test setup. When it comes to the principle of frequency extension, these systems consist of both types of devices – multipliers and mixers. The latter often operating at high LO harmonics, although sub-harmonic mixers (2nd LO harmonic) are also used in high performance extenders for applications where dynamic range is essential i.e. antenna range measurements. Typical VNA extension system comprises of two frequency extenders. Each extender consists of a multiplier chain for converting the RF signal to the required frequency range and typically two receivers / down-converters, which are driven by the LO source from the VNA, produce IF test and IF reference signals. The IF signals are fed into the VNA receivers to measure the S-parameters. While the actual RF test frequency could be in a range of several hundred gigahertz, the down-converted IF signals are in the range of tens of megahertz. The concept of the VNA extender is shown in Figure 3: Noise Figure Analyser Extenders. This group of frequency extenders is designed to extend the range of noise figure analysers and spectrum or signal analysers with a noise figure measurement option. Typically, a set of extenders would consist of two modules – a noise source and a block down-converter. The purpose of the noise source is to generate a known and stable level of a broadband noise at the frequency of interest, while the purpose of the block down-converter is to convert the high frequency noise to the low IF frequency at which the analyser can measure. Such an extension system is aimed at achieving the highest possible Excess Noise Ratio (ENR) and lowest possible noise figure, which together allow for high level of measurement accuracy. The architecture of the block-down converter is largely similar to that of a spectrum analyser extender with particular attention paid to noise performance and spurious content. Communication Extenders. Communication extenders are suited for applications that call for extremely high levels of accuracy when it comes to measuring modulation quality and performance of complex wireless devices and systems. They are designed specifically with signal fidelity in mind and to minimise the intrinsic Error Vector Magnitude (EVM) of a test system. EVM is a popular performance metric that helps to quantify a combined impact of all system impairments and present them in a form of one parameter. The system EVM value is impacted by the noise figure, third-order intercept point and signal-to-noise ratio, phase noise and nonlinearities, to name just a few parameters. Typically, communication extenders are used to generate and transmit, as well as receive and analyse modulated signals. They operate on the principle of heterodyne mixing where the fundamental or sub-harmonic mixers are setup to work in a linear region. The up- and down-converter operate as a transmit (Tx) and receive (Rx)

How does a Frequency Extender work?

By Tomasz Waliwander, Chief Executive Officer at Farran Technology In the Test & Measurement field, a frequency extender is an electronic device that extends the frequency range of the equipment that it is used with. It is designed to use and convert the excitation signals provided by the test equipment, and seamlessly extend its standard frequency range to the required band. Conversion of the frequencies supplied by the T&M equipment can be achieved by means of frequency multiplying, mixing or combination of both, which is the case in more complex frequency extension systems. To learn more about the various types of frequency extenders please refer to ‘What are the different types of frequency extenders?’ A harmonic mixer is an example a frequency extender, that can effectively extend the coverage of a spectrum or a signal analyser by means of using a low frequency LO signal supplied by the analyser and performing down-conversion at a harmonic this frequency. In this case the mixing occurs in accordance with a formula IF = RF ± Nx LO, where N is a harmonic number. The IF signal is supplied back into the analyser for analysis. This way a high frequency RF signal that lies far beyond the standard frequency range of the analyser can be detected and down-converted by a frequency extender to an intermediate frequency that the analyser can work at. A frequency extender can also be used to help generate high frequency signals and in such applications, it can be interfaced with a signal source or a signal generator. In this case, the extender multiplies the input signal supplied by the generator to a frequency that the extender is intended to work at, which happens in accordance to a formula FOUT = N x FIN, where N is multiplier factor. Typically, that means that the output frequency is a fixed multiple (i.e. 2, 3, 6, 12, 18 etc.) of the input frequency. For more complex Test & Measurement systems where there is a need for signal generation as well as analysis, more sophisticated extension systems are required that use a combination of both mixers and multipliers to provide the required functionality. Regardless of the type of frequency conversion and the level of complexity, frequency extenders are intended to interface seamlessly with the dedicated T&M equipment by being compliant with the frequencies and signal levels that such equipment supplies. In many instances, the equipment itself is intended to work in a frequency extension mode and is fitted with the required hardware and software options, and can be easily configured via the user interface. Click here to learn more about the different types of frequency extenders

What is a Frequency Extender?

By Tomasz Waliwander, Chief Executive Officer at Farran Technology In the Test & Measurement field a frequency extender is defined as an electronic device that allows for extending the frequency coverage of the equipment that it is intended to work with. A frequency extender performs frequency conversion, either by multiplication or by heterodyne mixing, or by a combination of both. Frequency multiplication is realised by a device in which its output frequency is the harmonic (multiple) of the input frequency i.e. FOUT = N x FIN. A frequency multiplier typically uses nonlinear semiconductor circuits to generate harmonics of the input signal. Typically, we see such devices with multiplier factors of 2, 3, 4 and 5, however 6 and beyond are also possible in a multistage or cascaded circuit configurations. Heterodyne mixing is achieved in a device called a mixer, which operates on a principle of mixing one of the two signals, either radio frequency (RF) or intermediate frequency (IF), with a local oscillator (LO) frequency to produce new frequencies. In its most common application, the mixer produces a sum and a difference of the two signals applied to its inputs i.e. IF = RF ± LO for a mixer operating as a down-converter, or RF = LO ± IF in case of an up-converter. Other more complex scenarios, in which mixing of signals’ harmonics is considered, are also possible. In principle, a relatively simple device such as a mixer or a multiplier, can be considered a frequency extender. In practice however, extending the range of a modern electronic equipment requires more complex solutions. In such cases, frequency extension is achieved by a combination of both frequency multiplication and heterodyne mixing, and aims to extend the frequency coverage of the equipment without deteriorating its other key parameters – for example output power, stability and/or dynamic range. There are various types of test & measurement equipment for which frequency extenders are designed and manufactured, with vector network analysers, spectrum & signal analysers, noise figure analysers, signal generators to name just a few. Such frequency extension systems are used in applications that require high frequency operation such as radar testing, antenna measurements, on-wafer measurements, wireless communication and material characterisation. Click here to learn more about how frequency extenders work Click here to learn more about the different types of frequency extenders

THz – To be or not to be in 6G?

By Tomasz Waliwander, Chief Executive Officer at Farran Technology Introduction While the story is still being written for 5G as the networks are being deployed in many parts of the world, this fifth-generation communication technology is already conditioning the path for what follows – 6G. With 5G still to deliver on its promises, and mm-wave bands largely underutilized in comparison with the Sub-7GHz range, the research community is already investigating the next generation of communication technology. The 6G specifications are expected to be developed and released around 2026-2027 and at the moment it is challenging to provide a clear and concise vision for 6G. However, three things about 6G appear to be certain: 6G is expected to be more capable, intelligent, reliable, scalable and power efficient, satisfying all the requirements that cannot be realized at present with 5G [5]. 6G will employ a combination of technologies already used in 5G and other previous generation wireless networks, as well as new technologies that were either deemed too immature for 5G or will be adopted or developed specifically for 6G [1]. 6G will most likely continue the trend of using higher and higher carrier frequencies beyond the mm-waves through THz bands and up to visible light to provide high-capacity point-to-point communication with an aim to achieve spectral efficiency 5 times greater than 5G [6]. 6G will inevitably continue the expansion into higher frequencies, with a 100 – 300 GHz range being considered as the first opportunity window where a number of services for radio astronomy, satellite earth exploration, mobile satellite and inter-satellite already allocated between in the 141.8 – 275 GHz band [6]. Federal Communication Commission (FCC10) has designated 21.2 GHz of spectrum for unlicensed use in the 116-123 GHz, 174.8-182 GHz, 185-190 GHz and the 244-246 GHz bands [7]. KPIs of 6G The basic 6G requirements for peak data rate are expected to be 50x that of 5G, with the user data speed experience at least 10 times better than that with 5G networks. Additionally, 6G is to offer much higher area traffic capacity and connect even greater number of devices than 5G. With even lower latency and much improved reliability, 6G will truly address the needs of autonomous mobility, industrial automation and robotics. A detailed comparison of current 5G and expected 6G KPIs is provided in the table below. KPI 5G 6G Peak data rate 20 Gb/s 1 Tb/s Experience data rate 0.1 Gb/s 1 Gb/s Peak spectral efficiency 30 b/s/Hz 60 b/s/Hz Experience spectral efficiency 0.3 b/s/Hz 3 b/s/Hz Maximum bandwidth 1 GHz 100 GHz Area traffic capacity 10 Mb/s/m2 1 Gb/s/m2 Connection density 106 devices/km2 107 devices/km2 Energy efficiency – 1 Tb/J Latency 1 ms 100 us Reliability 10-5 10-9 Jitter – 1 us Mobility 500 km/h 1000 km/h Table 1: KPI comparison of 5G and 6G [1]. THz as a key enabler of 6G Achieving this next step in wireless communications evolution will require much better understanding of technology limitations compared to previous generations – 3G, 4G and 5G. There are a number of key enablers that the success of 6G will rely on. For the purpose of this article, we will concentrate only on the enablers that expand and unlock additional spectrum bands for the purpose of wireless communications. While there are already plans to extend the upper limit of 5G to 71 GHz, the studies of 6G focus on upper millimeter wave bands (mm-waves), also known as sub-THz, with frequencies ranging from 100 to 300 GHz. This band will most likely be the most interesting band for research on new wireless communication systems [3]. One thing to note however is that 6G will not go about providing enhancements over 5G by just employing new parts of the spectrum, it will do so by utilizing legacy and new bands in a seamless and dynamic way to provide the required quality of service for the given use cases. RF engineering and device physics The development of 6G and utilization of sub- and THz bands will be met with even greater challenges than has been the case for 5G, where RF engineering and device physics is concerned [1]. Generation, modulation, detection and demodulation of THz signals in an energy efficient manner has always been very difficult and progress in this field over the last few decades has been relatively slow. In the last decade however, we have seen a number of new technologies, in particular III-V InP devices and Schottky diodes reaching the 1 THz mark. The technology readiness levels will have a significant influence and impact on the timeline of 6G adoption, with its roll out expected to start in 2028-2030. 6G devices will require very high levels of integration and ultra-low energy consumption, and extensive capability for energy conservation and harvesting to maintain long periods of stand-by activity especially in case of IoT devices [5]. 6G in sub-THz range will face challenges due to available transistor speeds in CMOS, SiGe, HBT and degradation of available gain, output power and noise figure that are required to overcome the path loss [3], [9]. The integrated circuit technologies currently available are not yet sufficiently mature or economical for Tbps data transfers over and up to 1km distance. The data transfer speeds of a few tens of Gbps have been reported at frequencies below 120 GHz and within 10m range using CMOS, while using InP semiconductors and high directivity antennas allows to achieve comparable speeds of up to 1km range [10]. Therefore, there is a stringent requirement to develop semiconductor technology and devices that could supply enough RF power that will allow for implementation of large array antenna systems and overcome path loss. The larger the antenna array the more output power is required, for example a 45 dBm EIRP required from a handset equipped with 16 element array requires a power amplifier (PA) that delivers 16-20 dBm, while to achieve 75 dBm EIRP from a 256-element array at the base station requires an output power

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