A $28-\text{GHz}$ Reconfigurable Load-Modulated Balanced Amplifier in $65-\text{nm}$ CMOS

A Ka-band reconfigurable load-modulated balanced amplifier (LMBA) with high output power and low noise figure is demonstrated in a $65-\text{nm}$ CMOS process. Based on the proposed three coupled transformer technique, the circuit matching state can be flexibly changed, thereby achieving dual working modes of power amplifier (PA) and low noise amplifier (LNA) in one chip. The LMBA consists of two balance paths and one control path. In PA mode, all three paths work normally to achieve the load modulation effect of LMBA, and achieve high output power and improved power backoff efficiency. At $27.5-\text{GHz}$, it achieved a saturated output power of $22.9-\text{dBm}$ and a peak efficiency of 23.1 %. In LNA mode, the balance path is closed, only the control path works, and the circuit implements the function of LNA. At 27.3 GHz, it achieved a peak gain of $23.6-\text{dB}$ and an in-band noise figure of $4.1-4.3 ~\text{dB}$. The circuit uses adaptive bias circuit and linearized bias circuit to achieve the improvement of AM-AM distortion in PA mode. The final circuit achieves improves the shortcoming of low output power and high noise figure of traditional bidirectional amplifier, and achieves low noise figure and excellent output power.