An X-band high-efficiency GaN load modulated balanced amplifier monolithic microwave integrated circuit (MMIC) composed of 90 Lange Couplers at radio frequency (RF) input and output, a pair of balanced power amplifier (BPA) and a control signal (CS) PA is presented in this article. The impedance of the BPA is modulated by varying the amplitude and phase of the injected CS at same frequency. The prototype has a peak continuous wave output power of 42.5 dBm, with efficiency of 45% to 55% at peak power and 40% to 45% at 6 dB output back-off over 8 to 11 GHz. The average efficiency for the 37.2 dBm output power is 40%, with adjacent channel leakage ratio of −32 dBc without digital predistortion at 10 GHz center frequency.
In this article, a broadband single-input GaN load modulated balanced amplifier (LMBA) with prematching networks is presented. The prematching networks of main PA are set up to reduce the difficulty of load modulation caused by high power control signal. The compact phase shifter and compression characteristic of the CS PA are used to monolithically integrate a single-input LMBA. The experimental results under continuous wave demonstrate a peak output power of 43.1-43.6 dBm, with drain efficiency (DE) of 49%-54% over the band of 8-12 GHz. Moreover, the DE is in the range of 30%-37% at the 6-dB power back-off region. By introducing a 16-quadrature amplitude modulation signal with 6-dB peak-to-average power ratio, the proposed single-input LMBA monolithic microwave integrated circuit achieves better than À28-dBc adjacent channel leakage ratio and higher than 32% average DE without digital predistortion at 9 and 11 GHz.
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