Switched-mode high-efficiency microwave power amplifiers in a free-space power-combiner array

Abstract

A design-oriented analysis of the microwave transmission-line class-E amplifier is presented. Experiments and harmonic-balance circuit simulations verify the theoretical equations which predict class-E-amplifier output power, maximum frequency of operation, and dc-RF conversion efficiency. Experimental results at 0.5, 1, 2, and 5 GHz are presented. At 0.5 GHz, 83% drain efficiency and 80% poweradded efficiency (PAE) are measured, with an output power of 0.55 W, using the Siemens CLY5 MESFET. These results are compared to a class-A and class-F power amplifier using the same device. At 5 GHz, 81% drain efficiency and 72% PAE are measured, with an output power of 0.61 W, using the Fujitsu FLK052WG MESFET. Finally, the 5-GHz class-E power amplifier is successfully integrated into an active-antenna array, demonstrating power combining of four elements with an 85% power-combining efficiency. At 5.05 GHz, the class-E power-amplifier antenna array delivers a total of 2.4 W of output power, with a dc-RF conversion efficiency of 74% and a PAE of 64%.

Microwave class-E power amplifiers

“…MMIC class-E PAs are demonstrated in GaAs [5,15], InP [6], GaN [9] and CMOS [11,16]. In [4], a FLK052WG class-E microstrip PA that delivers 0.61W with a compressed gain of 9.8 dB, a drain efficiency of 81%, and a PAE of 72% at 5GHz is integrated in a spatial combining array. Anti-resonant slot antennas are used to present the harmonic terminations.…”

“…[4,10], show that the output power across a fixed load is proportional to the square of the drain (collector) voltage:…”

“…[4] and X-band [5][6][7][8][9][10] with GaAs FETs. MMIC class-E PAs are demonstrated in GaAs [5,15], InP [6], GaN [9] and CMOS [11,16].…”

“…At higher frequencies, it is difficult to achieve optimal class-E operation associated with soft switching, since the switching frequency in Fig.1a is at least 5 times lower than the f T of the switching device, and "on" and "off" resistances are finite, resulting in an efficiency drop [4]. Although ideally all harmonics of the switching frequency are open-circuited, it is often sufficient to terminate only the 2 nd harmonic, since device gain drops and circuit losses increase to a point of diminishing returns.…”

High-efficiency parallel-circuit class-E power amplifier with distributed T-shaped compensation circuit

“…proposed the parallel-circuit class-E PA, which exhibits a maximum operating frequency 1.4 larger than the conventional class-E PA with shunt capacitance [5]. The maximum operating frequency f max of the class-E/parallelcircuit class-E PA is the intrinsic limitation due to the transistor output capacitance C out [5,6].…”