Silicon carbide MESFETs performances and application in broadcast power amplifiers
2001 IEEE MTT-S International Microwave Sympsoium Digest (Cat. No.01CH37157)
PAE, and power gain according to input power levels at a V GS of Ϫ12.5 V and V DD of 35 V. From the measured results, the maximum PAE of 72.3% with a power gain of 10.27 dB is achieved at a P out of 40.27 dBm, which delivers a drain efficiency of 79.8%. Figure 7 shows measured harmonic power levels of the class-E SiC MESFET power amplifier with the output matching network using transmission lines. It is worth noting that the proposed output load network significantly suppresses second-and
... es second-and third-harmonic power levels below Ϫ58 dBc. The fourth-and fifth-harmonic power levels were maintained below measurable range. From the measured results, it is evident that the high current density and high breakdown voltage of the SiC MESFET can make the class-E switch-mode amplifier operate with high power and high efficiency over 2 GHz. CONCLUSIONS In this study, a high efficiency class-E power amplifier using a SiC MESFET was designed and implemented at 2.14 GHz for the first time. To improve output power and efficiency by suppressing harmonic powers and minimizing losses, an output matching circuit using the transmission lines was used. From measured results for a single tone, harmonic power levels were maintained below Ϫ58 dBc at a whole output power level. The peak PAE of 72.3% with a power gain of 10.27 dB was achieved at a P out of 40.27 dBm at 2.14 GHz. From the measured results, it is worth noting that SiC MESFET devices with high current density and high breakdown voltage can make the class-E switch-mode amplifier deliver high output power and high efficiency over 2 GHz. ABSTRACT: It can be shown that a hyperbolic frequency-modulated waveform is Doppler-invariant only when the Doppler factor is a constant number, i.e., the target has a constant velocity and along the direction from the radar to the target. If the target moves in an arbitrary direction, the degradation of the pulse compression caused by the mismatch between the reflected signal and the matched filter may still exist. In this paper, we demonstrate that the Doppler effect caused by the moving target in an arbitrary direction can be approximated by a target with an initial velocity and a constant acceleration along the direction from the radar to the target, which results in a frequency shift in the reflected waveform. Therefore, a bank of matched filters with preselected values of frequency shifts can be utilized to compensate for the Doppler effect. Numerical examples, with target moving in an arbitrary direction, are presented to illustrate this effect, which has been successfully compensated by shifting the frequency response of the matched filter. ABSTRACT: A narrow linewidth fiber laser based on fiber Bragg grating Fabry-Perot etalon is demonstrated. Spatial hole burning effect is restrained by fiber Faraday rotator. The short fiber Bragg grating Fabry-Perot etalon as narrow bandwidth filter discriminates and selects laser longitudinal modes efficiently. Stable single frequency 1550 nm laser is acquired. Pumped by 976 nm laser diode, the fiber laser exhibits 11 mW threshold. Output power (50 mW) is obtained upon the 200 mW pump power. Optical-optical efficiency is 25% and slope efficiency is 27%. The linewidth of laser is less than 10 kHz, measured by the delayed self-heterodyne method with 10 km single mode fiber. In addition, the lasing linewidth keeps less than 10 kHz over 1 nm tuning range in the temperature tuning experiment.