Exodus Advanced Communications

Whitepapers from Exodus Advanced Communications

Advantages of GaN RF Amplifiers with High Peak-to-Average Capability to P1dB Rated Amplifiers

This application note from Exodus Advanced Communications compares Gallium Nitride (GaN) RF amplifiers with high peak-to-average capability to traditional P1dB rated amplifiers. The paper highlights that GaN SSPAs offer superior efficiency (>40%) and power density (>8W/mm of gate periphery), particularly advantageous for wideband applications exceeding 1.0 GHz, including 5G communications, radar, EMC/EMI testing, and electronic warfare. While P1dB amplifiers provide excellent linearity up to their compression point, GaN devices maintain performance with signals exhibiting high crest factors and peak-to-average ratios – crucial for modern complex modulation schemes where peaks exceed the 1dB threshold. The analysis concludes that GaN SSPAs are a strong solution for applications needing both efficiency and robustness under dynamic signal conditions.

Gallium Nitride (GaN)Amplifiers

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Amplifier Classification A vs. AB

This application note from Exodus Advanced Communications details the differences between Class A, B, and AB amplifier designs. The paper focuses on bias characteristics affecting performance metrics like efficiency and linearity in RF & Microwave amplifiers utilizing devices such as LDMOS, MOSFETs, GaN, or GaAs. Class A amplifiers offer the best linearity (360° conduction angle) at 25-30% efficiency, while Class B achieves 70-80% efficiency but suffers from crossover distortion with a 180° conduction angle. The preferred compromise is Class AB, providing 50-70% efficiency and improved linearity by overlapping the conduction angles of paired devices in a push-pull configuration to minimize distortion. The document also clarifies that amplifier robustness isn't inherent to class but dependent on overall engineering design including heat dissipation and power supply sizing.

Amplifiers

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Impact of Drain Voltage on GaN RF Transistors and Safe Operating Area (SOA) Analysis

This application note from Exodus Advanced Communications details the challenges associated with increasing drain voltage (VDS) in Gallium Nitride (GaN) RF transistors used in high-power Solid State Power Amplifiers (SSPAs). The paper identifies key failure mechanisms resulting from higher VDS, including thermal runaway, avalanche breakdown, charge trapping, and accelerated device degradation due to hot carrier effects. It emphasizes the importance of understanding the Safe Operating Area (SOA), which is defined by limits on current, power dissipation (P = VDS × ID), and breakdown voltage – all critical for reliable operation. Mitigation strategies presented include improved thermal management, optimized biasing networks, and robust load matching techniques.

AmplifiersGallium Nitride (GaN)

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Pulse Amplifier Definitions and Terminology

This application note from Exodus Advanced Communications defines key terminology related to solid-state pulse amplifiers used in EMC and other applications. It details specifications like duty cycle (typically ≤6%, but up to 10% or 20% for some models), Pulse Repetition Rate (PRF) up to 400kHz, and rise/fall times of 15-25ns. The document highlights the importance of understanding duty cycle correction factors – a 10% duty cycle requires multiplying average power by 10 (or adding 10dB) to determine peak power—providing tables for 1kW and 4kW output levels. Exodus amplifiers include features like front panel monitoring of forward/reflected power, VSWR, module voltages/currents, and a large touchscreen display conforming to IEC-348 safety standards. The paper also contrasts the pulse response characteristics of solid-state amplifiers (SSPA) with those of traditional Traveling Wave Tube (TWT) amplifiers demonstrating lower overshoot in SSPAs.

Amplifiers

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RF Test setup for measuring Power & Harmonics

This application note from Exodus Advanced Communications details a basic RF test setup for measuring amplifier output power and harmonic performance. The method utilizes calibrated high-power couplers or attenuators connected to the amplifier’s RF output, coupled with a power meter (e.g., Anritsu ML2487A) and sensor (Anritsu MA244D) to verify rated power at 3-5 frequency points. Harmonic measurements are performed at the amplifier's P1dB rating using a spectrum analyzer (e.g., Agilent E4408B) to record the 2nd and 3rd harmonics, either directly from the output or via the RF sample port for filter verification. Alternative harmonic measurement techniques include utilizing an anechoic chamber with a broadband horn antenna. Proper calibration of all test equipment (signal source Anritsu-68369A/NV, load/attenuator Weinshel-82-30-34, coupler Werlatone-C10336-16) and accounting for insertion losses are emphasized for accurate results.

Power & Harmonics

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SSPA or Tube - TWT technology which is best?

This application note from Exodus Advanced Communications compares Solid State Power Amplifiers (SSPAs) to traditional Tube Technology (TWTs, Klystrons, Magnetrons). It details how SSPAs utilizing GaAs, LDMOS, and especially GaN semiconductors are rapidly closing the performance gap with tubes in terms of power output and bandwidth. The paper highlights SSPA achievements: >150W between 700MHz-6GHz, >80W at 6.0-18.0 GHz, >40W above 18GHz, and >20W beyond 40GHz – achieved through advancements in RF combining techniques, enabling multi-kW power levels. While tubes remain suitable for ultra-high power (>10kW) SATCOM and certain robust airborne applications, SSPAs are now preferred for a wider range of applications including CW/Pulse Radar, EMC/EMI testing, and EW/ECM systems due to improved reliability, size, cost and availability.

AmplifiersGallium Nitride (GaN)

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VSWR Conversion to Reflected Power

This application note from Exodus Advanced Communications details the relationship between Voltage Standing Wave Ratio (VSWR), Return Loss, Reflection Coefficient, Mismatch Loss and delivered power in RF systems. It explains how impedance mismatches lead to reflected power and reduced system efficiency. The document provides formulas for calculating these parameters and presents tables showing the impact of VSWR on delivered power at different forward power levels – specifically 10W, 100W, 250W, and 1000W. For example, a VSWR of 2.0 with 100W forward power results in 89W delivered and 11W reflected, while at the same VSWR but 1000W forward power delivers 890W and reflects 110W.

VSWR

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VSWR and its Effects on Power Amplifiers

This application note from Exodus Advanced Communications details the impact of Voltage Standing Wave Ratio (VSWR) on RF/Microwave power amplifiers, particularly in test applications. The paper explains VSWR as a consequence of impedance mismatch – typically between 50Ω source and load – and how this leads to reflected power reducing system efficiency. A VSWR of 2:1 corresponds to approximately 10% reflected power, which can increase total power dissipation by up to 110%. The document outlines methods for mitigating VSWR issues, including the use of attenuators (3dB provides improvement but halves output) and matching networks, as well as amplifier protection techniques like shutdown and foldback mechanisms. It emphasizes that amplifiers rated to handle 2:1 VSWR are common, but sustained higher levels—especially above 6:1 resulting in >50% reflected power—can be detrimental even if not immediately damaging.

VSWRAmplifiers

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Waveguide Insights: Understanding Rectangular and Double-Ridge Designs for Enhanced RF Systems

This application note details rectangular and double-ridge waveguides for RF system applications like communications, radar, and EMC/EMI testing. It outlines design considerations including dimensions (e.g., WR90 with a 0.90” inner width), materials (aluminum, copper, silver plating >18GHz), and operating principles—specifically the TE10 mode in rectangular waveguides and cutoff frequencies. Tables provide specifications for standard waveguides (WR4 to WR975) covering frequency ranges up to 50 GHz, power ratings (CW up to 200kW, peak up to 50000kW), and dimensions. Double-ridge designs are presented as offering wider bandwidth at the expense of insertion loss and power handling. Power handling considerations address average power dissipation through heat sinking and preventing breakdown due to peak voltages.

Waveguides

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