High Power Amplifier Module Research Articles

Gysel combiners with high-selectivity filtering characteristics: analysis and design

Abstract This paper provides the details of a novel systematic design methodology for two-way in-phase filtering Gysel splitter/combiner networks with high selectivity, which finds application in high power amplifier modules. It simultaneously realizes a filtering function and a two-way splitter/combiner function. The proposed five-port filtering device, based on the Gysel topology, is transformed into a ring of coupled resonators. A rigorous coupling matrix describing the network is used to synthesize the integrated filtering and combining functions. This general network can be implemented in any of the available filter technologies. In this paper, a few design examples are provided, and a six-pole prototype utilizing compact combline coaxial resonators is demonstrated. The proposed design provides an integrated dual function module, reducing component counts and system complexity. A design was fabricated and tested demonstrating good experimental results.

Balancing Thermal and Electrical Packaging Requirements for GaN Microwave and Millimeter-Wave High Power Amplifier Modules

A method for balancing thermal and electrical packaging requirements for gallium nitride (GaN) high power amplifier (HPA) modules is presented. The goal is to find a design approach that minimizes the junction temperature of the GaN so that it is reliable and has interconnects that meet electrical performance requirements. One benefit of GaN is that it can simultaneously achieve high power density and operate at microwave and millimeter-wave frequencies. However, the power density can be so high that the necessary thermal solutions can have negative impact on electrical performance. This is especially a concern for the electrical interconnects required for the input/ output ports on high power amplifier devices. This is because the signal interconnects must operate at GHz frequencies, which means that special care must be taken to avoid problems such as undesired signal coupling and ground path inductance. Therefore, this work focuses on GaN packaging and its integration into a module. The results show that an optimum thickness for the GaN heat spreader exits for thermal performance but the electrical design is impacted negatively if the optimum thermal design is chosen. Therefore, a balanced design is chosen which meets overall system level requirements.

질화갈륨 소자를 이용한 DPD용 고집적 팔렛트형 고출력증폭기 모듈 설계

본 논문에서는 고출력 및 고효율 특성을 지니는 질화갈륨(gallium nitride, GaN) 고출력 트랜지스터 소자를 이용하여 WiMAX 및 LTE(long term evolution) 시스템에 사용 가능한 60watt급 고출력증폭기 모듈을 팔렛트(palette) 타입으로 개발한 결과에 대하여 기술한다. 높은 이득을 얻기 위한 라인업(lineup) 구성을 위해 저전력이면서 고이득을 지니는 전치증폭단, 8watt급의 GaN 구동증폭단, 그리고 30watt급 GaN 소자 2개를 도허티(doherty) 구조로 구성한 60watt 고출력증폭단을 사용하였으며, 이로부터 2.5~2.68GHz에서 61.4dB의 이득과 <TEX>${\pm}$</TEX>0.075dB의 우수한 이득 평탄도를 얻었다. 특히 구동단과 고출력증폭단은 고효율 및 고출력 특성의 GaN 소자를 사용하였고, 또한 추가적인 효율 개선을 위해 도허티 구조를 적용함으로써 보다 높은 효율을 가지도록 하였다. 현재 전 세계적으로 널리 사용되고 있는 WiMAX 신호를 사용하여 제작된 팔렛트 타입의 증폭기 모듈의 성능을 측정하였는데, RRH(remote radio head) 타입으로 구성된 사용 예에서 WiMAX 변조 신호 10watt 출력 기준으로 약 37~38%의 효율을 나타내었다. 제작된 증폭기 모듈을 디지털 전치왜곡기(digital predistorter, DPD)와 연동하여 시험한 결과 WiMAX 변조 신호 10watt 출력에서 ACLR은 46dBc 이상의 특성을 지닌다. This paper describes the design of a palette-type 60watt high power amplifier module using gallium nitride(GaN) devices with high power and efficiency performances for WiMAX and LTE systems. The line-up for the high gain amplifier module consists of the pre-amplifier stage with low power and high gain, 8watt GaN driving amplifier stage, and 60watt GaN high power amplifier stage of Doherty structure with two 30watt GaN devices. The obtained gain is 61.4dB with an excellent gain flatness of <TEX>${\pm}$</TEX>0.075dB over 2.5~2.68GHz. GaN devices and the Doherty structure are adopted for the improvement of high efficiency and output power. The measurement for the fabricated high power amplifier module of palette type is performed using the widely known WiMAX signal all over the world. In the example of RRH(remote radio head) application of the fabricated amplifier module, the measured efficiency is 37~38% with the 10watts of modulated output power. It is shown that when the fabricated amplifier module is activated with a digital predistorter(DPD), the measured ACLR is better than 46dBc under the 10watts of modulated output power.

A K-Band Low-Power Miniaturized Hyperthermia System

A K-band low-power miniaturized planar-type hyperthermia system was developed to replace massive and expensive equipment. The system consists of a VCO with a buffer amplifier, a high-power amplifier module, a 20-dB-coupled line coupler, a chip circulator and two power detectors for signal generation, amplification and power monitoring. All these components have been implemented in planar form on two module blocks. The total size of the hyperthermia system was less than <TEX>$10\times6.5\times3\;cm^3$</TEX>. In order to verify the system performance, ablations were carried out on nude mice xenografted with human breast cancer. Ablation results show performance comparable to the massive components-based system. This work shows the feasibility of a low-cost miniaturized hyperthermia system for practical clinical applications.

Thermal Gain Variation Compensation Technique Using Thermistor on HPA Module for W-CDMA System

The thermal gain variation of a high-power amplifier (HPA) module for a wide-band code division multiple access (W-CDMA) system application was reduced to within ±1dB by applying a thermistor to compensate the gain variation. Two techniques for gain variation compensation with respect to temperature were investigated: base bias control according to temperature, and use of a thermistor in a matching network. Experimental comparison of two techniques indicated that the thermistor-based technique was more effective in reducing the gain variation without affecting linearity. A fabricated two-stage HPA module with a thermistor in its input matching network achieved a small gain variation within ±1dB and ±5MHz offset adjacent channel leakage power ratio (first ACLR) below -36dBc over the temperature range from -10 to +85°C, where the first ACLR was measured under a load-mismatched condition with a voltage standing wave ratio (VSWR) of 1.4 : 1.

A Hybrid Evolutionary Modeling/Optimization Technique for Collector-Up/Down HBTs in RFIC and OEIC Modules

A hybrid computer-aided design (CAD) tool for automatic simulation and characterization of advanced collector-up/down heterojunction bipolar transistors (HBTs), which are expected to be used as the high-power-amplifier (HPA) module in radio-frequency integrated circuit (RFIC) and the blue laser diode (LD)/heterojunction phototransistor (HPT) module in optoelectronic integrated circuit (OEIC), has been successfully established. By expanding the essence of reported techniques, the newly-developed equivalent-circuit modeling approach focuses on combining the genetic algorithm (GA) with refined analytical-modeling equations yielding reliable initial values of model parameters. This SPICE-like simulator reliably and efficiently relates device/circuit performances directly to the direct current/radio frequency (dc/RF) measurements since it implicitly accounts for physical correlations among model parameters and does not require ad hoc de-embedding test structures as well as special simplifying assumptions in the optimization period. Evolutionary programming is performed to achieve tedious circuit-level simulations in shortest turnaround times and the computational efficiency permits execution of an optimization involving random generation of circuit parameters. In this study, a detailed comparison of direct-measured, analytical-derived, and numerical-simulated results, for the pnp InGaAs as well as npn InGaP collector-up HBTs as the HPA module in RFIC and the npn ZnSe-Ge collector-down HBT as the blue LD/HPT module in OEIC, is presented. To further demonstrate the accuracy and robustness of this approach, the npn AlGaAs-InGaAs collector-down HBT, which can be incorporated in a preamplifier for optical communication, is investigated.