A Co-Designed Band-Pass-Filter-Based Extended Continuous Class-B/J Power Amplifier

초록

This paper presents a high-efficiency S-band power amplifier (PA) employing the extended continuous class-B/J (ECB/J) mode, co-designed with a 5th-order Chebyshev band-pass filter (BPF) for harmonic radar applications. The ECB/J mode is specifically adopted because the design parameter gamma expands the fundamental impedance solution space, accommodating the frequency-dependent impedance deviations that the BPF introduces across the operating bandwidth, a tolerance that the standard continuous class-B/J mode cannot provide. The proposed architecture employs a harmonic-controlled output matching network (HCOMN) that performs fundamental and harmonic impedance matching, while the filter's inherent transmission zeros at the second-harmonic frequency provide high spectral purity without requiring a separate filtering stage. The ECB/J mode's expanded design space is essential for this integration: while the BPF maintains impedance transparency at the center frequency, it inevitably introduces frequency-dependent impedance variations at the band edges of the fundamental band, which fall outside the standard continuous class-B/J design region but are accommodated by the ECB/J mode. Experimental results for the fabricated PA demonstrate a drain efficiency of 71.1-74.6%, a saturated output power of 39.7-40.4 dBm, and a power gain of 11.9-13.7 dB across 2.2-2.6 GHz, with second-harmonic suppression ranging from-44.9 to-68.5 dBc achieved through a BPF of physical size 13.2 & times; 35.1 mm(2).

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