Solid-state Power Amplifier Module Research Articles

The conceptual design of the high-efficiency 400 kW solid-state power station at 352 MHz for the European spallation source

Abstract This paper introduces an innovative conceptual design of a 400 kW solid-state power amplifier (SSPA) station and presents preliminary measurements for the key components. Recent advancements and benefits of solid-state technology have made the prospect of replacing vacuum tubes increasingly appealing. Historically, a significant challenge was the limited output power capacity of individual solid-state transistors, necessitating the integration of numerous units to generate high-power microwave signals in the range of hundreds of kilowatts. However, modern transistors capable of producing over 2 kW of output power have emerged, facilitating this transition. Another weak point was low power efficiency in high-power operating mode. The advanced rugged technology (ART) of solid-state devices enables the utilization of these transistors in nonlinear and switching operating classes, thereby enabling the creation of high-efficiency high-power amplifiers. In this conceptual design, 264 SSPA modules based on ART, each with a power output of 1.6 kW, are combined. The measurements revealed a single SSPA capable of delivering up to 2 kW output power with a power efficiency of 73% at frequency of 352 MHz. Due to the minimal losses during module combination and working SSPA in Class-C operation mode, the power efficiency of the station is expected to closely mirror that of a single module.

An SIW-Based GaN Power Amplifier Module in LTCC

This article reports a solid-state power amplifier module in low-temperature cofired ceramic (LTCC) technology. For compactness and low loss, the package utilizes substrate-integrated waveguides (SIWs). To meet the thermal requirements, the amplifiers are mounted on a metallic plate that is integrated into the LTCC multilayer and transfers the heat to a spreader. Both RF and thermal measurement results for a package with two integrated 10-W gallium nitride (GaN) power amplifiers at the K-band are presented. They demonstrate the suitability of the module for highly integrated transmitters as needed for phased arrays or multiple-feed-per-beam satellite antennas.

Feedback compensated 10 kW solid-state pulsed power amplifier at 352 MHz for particle accelerators

This paper presents the first results of an in-house developed low-level radio frequency (LLRF) system and a 10 kW solid state power amplifier (SSPA). The design approach for the SSPA is based on eight resonant single-ended kilowatt modules combined using a planar Gysel combiner. Each of the single-ended modules is based on a two-stepped impedance resonant matching, allowing for harmonic suppression, simple design for massive production, and high-performance design. A design methodology to tune SSPA modules for optimum combining efficiency is presented thoroughly in the time domain. We characterize the power droop due to capacitor banks in the time domain. In open loop of compensation, it is about 1 kW within the pulse of peak value 10 kW and a duration of 3.5 ms. This may lead to the beam instability of the accelerator as particles are not provided with the same energy during the pulse. By incorporating our LLRF system, it is demonstrated that the objective of amplitude and phase stability is satisfied, as required in the European Spallation Source proton accelerator. The presented design also offers the advantages of compact form factor, low complexity, and better performance. In closed loop compensation, the variation of amplitude (pulse droop) is measured on the order of 20 W, which is equivalent to 0.2% at 10 kW peak output power.

High-power shortwave DRM transmitter in solid-state technology

ABSTRACTDesign of high-power shortwave broadcast transmitters is one among the rare areas in the field of radiofrequency (RF) electronics, where the electron tube, as the main element for amplification of RF signal, is still in active use. The first successful attempts to replace the electron tube with solid-state components, primarily in the output stage amplifier modules for the Digital Radio Mondiale (DRM) shortwave broadcast transmitters have been published only recently. With the latest technology advancements in RF power transistors, it is now possible for commercially available RF power MOSFET transistors to be used for switching purposes at shortwave frequencies. Here, an architecture of a 10 kW shortwave broadcast transmitter with solid-state power amplifier modules in the RF output stage is proposed. Different implementations of the RF output stage that include power adding network from each amplifier module and the output matching network are analysed, both analytically and numerically. After choosing the optimal architecture, a prototype of a commercial shortwave DRM broadcast transmitter was designed and constructed, measured, tuned and tested at RIZ Transmitter factory Zagreb.

(Invited) GaN High Power Devices and Their Applications

Wideband gap semiconductors, such as GaN and SiC, are called as next generation compound semiconductor platform. In material aspect, GaN has wideband gap energy(Eg=3.4eV), excellent electron transport properties, including good mobility, and high saturated drift velocity. So, GaN-based HEMT devices are attractive candidates for high-power amplifiers for communication and radar systems, and high power electronic switching devices for high efficient energy conversion systems.[1-5] We started the R&D of GaN technologies in 2010, and the progress of GaN RF device and power amplifier technologies will be presented today. Especially, I’d like to mention about recent demonstration of GaN power HEMTs developed using the ETRI’s proprietary 4-inch GaN full process for S-band and X-band ship radar systems. We are developing high power GaN devices technologies using two platforms. One is a GaN-on-Si for cost-effective power electronic device solutions and the other a GaN-on-SiC for performance-oriented power amplifier device solutions. But my presentation will be focused on the high power amplifier devices technologies and recent radar demonstration results. A 200W solid state power amplifier (SSPA) was developed using ETRI’s 100W GaN transistors and mounted it on the S-band ship radar system. We tested and successfully got good radar images. To evaluate our device performance, we made and installed two kinds of high power SSPA modules using ETRI’s and Cree’s commercial GaN HEMTs products, respectively. Using these modules, we performed comparative study on the radar images each other. This is the first demonstration of SSPA ship radar in Korea. Test results were almost same and will be presented in this conference.

(Invited) GaN High Power Devices and Their Applications

A 100 W-class GaN transistor is developed based on the ETRI’s proprietary 4-inch AlGaN/GaN high electron mobility transistor (HEMT) process and device technologies for the high power of 200 W solid state power amplifier (SSPA) applied to S-band ship radar system. For systematically comparative study of the developed power devices, two SSPA modules based on ETRI’s and Cree’s commercial GaN HEMTs products are fabricated and tested. After a comparison of both measured module results, good radar images for both SSPAs are successfully obtained with almost the same performances. To our best knowledge, this is the first report of SSPA ship radar with GaN power devices in Korea.

System efficiency analysis for high power solid state radio frequency transmitter

This paper examines some important relationships, related with the system efficiency, for very high power, radio frequency solid-state transmitter; incorporating multiple solid-state power amplifier modules, power combiners, dividers, couplers, and control/interlock hardware. In particular, the characterization of such transmitters, at the component as well as the system level, is discussed. The analysis for studying the influence of the amplitude and phase imbalance, on useful performance parameters like system efficiency and power distribution is performed. This analysis is based on a scattering parameter model. This model serves as a template for fine-tuning the results, with the help of a system level simulator. For experimental study, this approach is applied to a recently designed modular and scalable solid-state transmitter, operating at the centre frequency of 505.8 MHz and capable of delivering a continuous power of 75 kW. Such first time presented, system level study and experimental characterization for the real time operation will be useful for the high power solid-state amplifier designs, deployed in particle accelerators.

Power Amplification at 0.65 THz Using InP HEMTs

In this paper, progress toward developing solid-state power-amplifier modules at 0.65 THz is reported. This work is enabled by a >;1 THz fMAX InP HEMT transistor with a 30-nm gate and an integrated circuit process specifically tailored for circuits operating at frequencies approaching 1 THz. The building block of the reported amplifier modules is an eight-stage terahertz monolithic integrated circuit (TMIC) amplifier. The first six stages of the TMIC use 20- transistors, while the final two output stages rely on two power-combined 20-μm transistors to increase the output power. For operation at 0.65 THz, the TMIC also relies on integrated electromagnetic transitions for direct coupling with the WR1.5 waveguide of the amplifier package. Two modules are reported, with the first module containing a single TMIC and demonstrating a peak saturated output power of 1.7 mW at 640 GHz with a measured small-signal gain ≥10 dB from 629 to 638 GHz. The second module features two power-combined TMICs to increase output power. This is done using a waveguide Y-junction as both the combiner and splitter. In test, this power-combined module reached a peak output power of 3 mW at 650 GHz and measured small-signal gain ≥10 dB from 625 to 640 GHz.

An X-band four-way combined GaN solid-state power amplifier

An X-band four-way combined GaN solid-state power amplifier module is fabricated based on a self-developed AlGaN/GaN HEMT with 2.5-mm gate width technology on SiC substrate. The module consists of an AlGaN/GaN HEMT, Wilkinson power hybrids, a DC-bias circuit and microstrip matching circuits. For the stability of the amplifier module, special RC networks at the input and output, a resistor between the DC power supply and a transistor gate at the input and 3λ/4 Wilkinson power hybrids are used for the cancellation of low frequency self-oscillation and crosstalk of each amplifier. Under Vds = 27 V, Vgs = −4.0 V, CW operating conditions at 8 GHz, the amplifier module exhibits a line gain of 5 dB with a power added efficiency of 17.9%, and an output power of 42.93 dBm; the power gain compression is 2 dB. For a four-way combined solid-state amplifier, the power combining efficiency is 67.5%. It is concluded that the reduction in combining efficiency results from the non-identical GaN HMET, the loss of the hybrid coupler and the circuit fabricating errors of each one-way amplifier.

An X-band GaN combined solid-state power amplifier

Based on a self-developed AlGaN/GaN HEMT with 2.5 mm gate width technology on a SiC substrate, an X-band GaN combined solid-state power amplifier module is fabricated. The module consists of an AlGaN/GaN HEMT, Wilkinson power couplers, DC-bias circuit and microstrip line. For each amplifier, we use a bipolar DC power source. Special RC networks at the input and output and a resistor between the DC power source and the gate of the transistor at the input are used for cancellation of self-oscillation and crosstalk of low-frequency of each amplifier. At the same time, branches of length 3λ/4 for Wilkinson power couplers are designed for the elimination of self-oscillation of the two amplifiers. Microstrip stub lines are used for input matching and output matching. Under Vds = 27 V, Vgs = –4.0 V, CW operating conditions at 8 GHz, the amplifier module exhibits a line gain of 5.6 dB with power added efficiency of 23.4%, and output power of 41.46 dBm (14 W), and the power gain compression is 3 dB. Between 8 and 8.5 GHz, the variation of output power is less than 1.5 dB.