Sher Azam

Designing, Fabrication and Characterization of Power Amplifiers Based on 10-Watt SiC MESFET & GaN HEMT at Microwave Frequencies

This paper describes the design, fabrication and measurement of two single-stage class-AB power amplifiers covering the frequency band from 0.7-1.8 GHz using a SiC MESFET and a GaN HEMT. The measured maximum output power for the SiC amplifier at Vd = 48 V was 41.3 dBm (~13.7 W), with a PAE of 32% and a power gain above 10 dB. At a drain bias of Vd= 66 V at 700 MHz the Pmax was 42.2 dBm (~16.6 W) with a PAE of 34.4%. The measured results for GaN amplifier are; maximum output power at Vd = 48 V is 40 dBm (~10 W), with a PAE of 34% and a power gain above 10 dB. The results for SiC amplifier are better than for GaN amplifier for the same 10-W transistor.

Single-stage, high efficiency, 26-watt power amplifier using SiC LE-MESFET

This paper describes a single-stage 26 W negative feedback power amplifier, covering the frequency range 200-500 MHz using a 6 mm gate width SiC lateral epitaxy MESFET. Typical results at 50 V drain bias for the whole band are, around 22 dB power gain, around 43 dBm output power, minimum power added efficiency at P1 dB is 47% at 200 MHz and maximum 60% at 500 MHz and the IMD3 level at 10 dB back-off from P1 dB is below -45 dBc. The results at 60 V drain bias at 500 MHz are, 24.9 dB power gain, 44.15 dBm output power (26 W) and 66% PAE.

High performance GaN HEMT class-AB RF power amplifier for L-band applications

This paper presents the design and characterization of a GaN HEMT based class-AB power amplifier (PA) for L-band radar applications at 1.3 GHz. The aim of this paper is to design and develop a 30 Watt PA together with high efficiency, small in size and low-cost solution. The source and load impedances have been extracted by performing source and load-pull for attaining an optimal performance of class-AB PA. The fabricated PA provides an RF power of 45.5 dBm at 1-dB compression point. The power added efficiency (PAE) of 63% is achieved together with power gain of 13.5 dB at desired frequency.

Design and fabrication of a GaN HEMT based amplifier for wideband applications

This paper reports design, fabrication and measurements of a wideband amplifier for UHF applications. A technology based on Gallium Nitride (GaN) transistor is used to design a class- AB amplifier with compact dimensions which can be employed as a driver stage for many UHF applications with wideband requirements. Wideband impedance transformers at input and output of the amplifier are implemented to achieve the wideband features including higher gain and efficiency. The designed amplifier is fabricated and then characterized to verify the design parameters and it has been observed that the simulated results are in agreement with the measured ones. Maximum RF output of 5W (37dBm) is demonstrated over frequencies ranging from 150-500 MHz with gain flatness of 2.5dB. Flatness of ±0.5dB is shown within 220-500MHz. The measured power gain is found to be above 17dB for the entire band.

Switching behavior of RF-LDMOS for class-F power amplifier in TCAD

Nowadays the characterization of RF devices under large signal is performed in TCAD by using computational load-pull (CLP) simulation technique. In this paper, we modified the CLP simulation technique further to study the switching response of RF-LDMOS transistor for high efficiency switching power amplifier (e.g. class-F). In class-F PA operation, we achieved 85 % power added efficiency (PAE) together with 1.0 W/mm RF power density on the basis of finite harmonics. By this CLP technique, we can study the switching response of intrinsic RF-devices directly under large signal operation prior to fabrication or non-linear model of RF-transistor without including any external lumped matching networks.

Designing of High Efficiency Power Amplifier Based on Physical Model of SiC MESFET in TCAD

The pulse input Class C power amplifier response of an enhanced version of a previously fabricated and tested SiC MESFET 11 are studied using a new technique to its physical model in TCAD. The device is simulated at 5% duty cycle pulse for Gain (dB), Power density (W/mm), power loss and power added efficiency (PAE %) at 500 MHz and 1 GHz. The results are then correlated to the device features in DC and RF I-V characteristics. A maximum PAE of 80% at 500 MHz with 36.9 dB power gain and power density of 1.07 W/mm is achieved.

Two-stage GaN HEMT based class-C pulsed amplifier for S-band radar applications

High performance amplifiers are always demanding in wireless communication. To amplify RF signal, power amplifier is considered as a heart source of the system. We have designed and developed a high performance two-stage pulsed class-C broadband PA for moderate range surveillance radar applications in the frequency range from 2.45 - 2.75 GHz. A common source configuration is used to deliver peak RF output power above 38 dBm. Hence, this amplifier can be used as driver amplifier for high power surveillance radar applications etc. The measured RF peak power of the amplifier is ~ 39 dBm.

Design and implementation of bias sequence circuits for GaN HEMT amplifiers both pulsed and CW applications

GaN HEMT with silicon substrate is famous and considered as the next generation of RF power transistor technology. It has major advantages of high power, low cost and reliability etc., GaN HEMT requires special attention in bias circuit to avoid the instability of the device. Sequence circuit is required to supply voltages in order. In this paper, we have design and implemented the sequential circuits in bias network for pulsed and CW applications. MAX881R is used in power supply for pulsed while LTI1964ES5-BYP with R2D Recon 2405 is used for high current application in CW. For pulsed applications in ON sequence the gate is turned-on ~ 220 ms before the drain, while in OFF sequence the drain is turned-off ~ 1.7 s before the gate. While in CW applications in ON sequence the gate is turned-on ~ 130ms before the drain and in OFF sequence, the drain is turned-off ~ 633ms before the gate.

10 Watts UHF broadband GaN based power amplifier for multi-band applications

The demand of broadband amplifier has been boosted to meet the requirements of multi-mode and multi-band wireless applications. GaN HEMT is the next generation of RF power transistor technology. In this paper, we have designed a 10W UHF broadband class-AB Power Amplifier (PA) based on GaN HEMT. The proposed amplifier has been designed and developed in the frequency range from 200-500 MHz. A maximum drain efficiency of 71% is achieved.

Advantage of TCAD to analyze RF-LDMOS for the broadband power amplifier

Technology Computer Aided Design (TCAD) provides an alternate method to study the power amplifier (PA) design prior to fabrication and is very useful for the extraction of an accurate large signal model. This paper presents a design approach from device to circuit level to study the performance of a broadband PA based on computational load-pull (CLP) analysis. To validate TCAD approach, we have designed a broadband (1.9 - 2.5 GHz) class AB PA with an output matching network. The large signal simulation results verify the optimum impedance value (Zf) by providing a desired RF output power of 30.8 dBm.