Sequential Load-Modulated Balanced Amplifier Using Harmonic Suppression Coupler

This article develops a sequential load-modulated balanced amplifier (SLMBA) with harmonic suppression couplers (HSCs). A T-shaped structure is utilized to design the HSC, which is smaller than the conventional coupler. The HSC can provide transmission zeros (TZs), which not only improve out-of-band rejection but also enhance the performance of the harmonic-tuned SLMBA. Then, the proposed broadband harmonic-tuned SLMBA can maintain high efficiency over a larger output back-off (OBO) range with a more compact size. To verify the proposed method, an SLMBA operating in the frequency range from 1.6 to 2.3 GHz is designed and measured. At the designed frequency band, drain efficiency (DE) is 53%–63% at saturation and 44.5%–61.8%/50.3%–56.5% at 8/10-dB OBO.