This letter reports a high efficiency class-E power amplifier using a GaN high electron mobility transistor (HEMT), which is designed at WCDMA band of 2.14 GHz. To improve output power and efficiency by suppressing harmonic powers, an output network using transmission lines is used. For a single tone, the proposed output network suppresses all harmonic power levels below 60 dBc for the whole output power range. The peak power-added efficiency (PAE) of 70% with a power gain of 13 dB is achieved at an output power of 43 dBm. The broadband performance with a power gain over 12 dB and PAE over 60% is maintained through 200 MHz.Index Terms-Class-E power amplifier (PA), gallium nitride (GaN) high electron mobility transistor (HEMT), harmonic termination, power-added efficiency (PAE), switching-mode amplifier.
In this article, we propose the wideband digital predistortion (WDPD) for a highly linear and efficient GaN HEMT Doherty power amplifier (DPA). The WDPD is composed of the memory less DPD and the memory system, which compensates for the memory effects to achieve a highly linear wideband performance. The 11th-memoryless polynomial characterizes the behavioral model of the DPA. The AM/AM and AM/PM lookup tables and the coefficients of the memory system are determined by the Recursive Least Square algorithm. For a 2-FA WCDMA signal with 10 MHz carrier spacing at 2.14 GHz, the adjacent channel leakage ratio at 610 MHz offset are improved over À50 dBc without the efficiency degradation at an output power of 36 dBm.
One prototype of the bandpass filter was fabricated on 0.8-mmthick substrate dielectric with constant r ϭ 2.65. The measured results with HP8510C are illustrated in Figure 5, as well as the simulated results with HFSS, very good agreement can be observed. The maximum pass band insertion loss is less than 1.5 dB and the in-band return losses, S11, are all less than Ϫ20 dB, even reaching Ϫ37dB at the transmission pole at 5.34 GHz. It can also be observed that the rejection band extends from 6.4 GHz to 7.8 GHz, about 20% bandwidth; the maximum rejection even reaches 50 dB, implying good potential to suppress the unwanted harmonics.
CONCLUSIONSA novel bandpass filter is proposed and implemented in this letter, which is implemented with combination of two quite different electromagnetic structures-CSRR and SIW. The design strategies are discussed; one prototype was fabricated to demonstrate the validity of proposed techniques. The measured results imply good in-band behaviors with insertion loss less than 1.5 dB and good return losses all less than Ϫ20 dB. In addition, the highlight lies in the sharp out-of-band rejection; the maximum rejection almost reaches 50 dB, the stopband width is about 20% at Ϫ20 dB. plementary split ring resonators, IEEE Microwave Wireless Compon Lett 14 (2004), 280-282. 4. J. Garcia-Garcia, I. Gil, M.F. Portillo, and M. Sorolla, Equivalentcircuit models for split-ring resonators and complementary split-ring resonators coupled to planar transmission lines, IEEE Trans Microwave
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