Integrated Inverse Class-F Silicon Power Amplifiers for High Power Efficiency at Microwave and mm-Wave

Abstract

This paper presents two 2-stage inverse class-F power amplifiers (PAs) at 24 GHz and 38 GHz, integrated in $0.13~\mu \text {m}$ SiGe BiCMOS technology. The PAs are composed of an inverse class-F output stage proceeded by a class-AB driving amplifier. An inter-stage matching network between the driver and output stage delivers an optimal inter-stage power to the output stage with a maximum PAE in the driver amplifier. The output stage’s load network based on multi-resonance LC resonators terminates harmonic impedance explicitly up to the third of the fundamental signal. By leveraging a native low capacitive reactance, the class- $\text {F}^{\mathrm {-1}}$ load network shapes a quasi-rectangular current waveform that effectively contains up to the fifth harmonic spectral component. A high impedance control is limited up to the second harmonic, shaping a half-sinusoid voltage peaking induced by DC, fundamental, and the second harmonic voltage spectra. The 24 GHz PA achieves 50% peak PAE, 16 dBm $\text {OP}_{\mathrm {-1dB}}$ , 18 dBm $\text {P}_{\mathrm {sat}}$ , and 19 dB saturated power gain with 2.3 V supply voltage at 24 GHz. The 24 GHz PA can maintain >45% PAE over 23.5–25.5 GHz and 1.5–2.4 V supply voltage range, manifesting a PAE robustness to the frequency and supply variations. For 38 GHz PA, measurements show 38.5% peak PAE, 15 dBm $\text {OP}_{\mathrm {-1dB}}$ , 17 dBm $\text {P}_{\mathrm {sat}}$ with 15 dB of saturated power gain at the $\text {OP}_{\mathrm {-1dB}}$ point when 2.4 V supply voltage is applied. The 38 GHz PA can sustain >35% PAE over 36–39 GHz and 1.5–2.5 V supply variation. The PAs also are tested under the input of band-limited signals modulated by various modulation schemes including 8-PSK, QAM, 16-QAM, 64-QAM, and 128-QAM, and test results are presented in this paper. The chip size is $0.95\times 0.6$ mm2 for 24 GHz PA and $0.93\times 0.55$ mm2 for 38 GHz PA, including all pads.