A Ka-Band Low-Power Ultra-Compact Reconfigurable Amplifier with Reverse Bypass Mode for Multi-Element Phased Array Transceivers

This paper proposes a Ka-band low-power ultra-compact reconfigurable amplifier with a reverse bypass mode for multi-element phased array transceivers. In phased array systems, an amplifier is required to compensate for division loss in a transmit (TX) mode, and a bypass mode is necessary for a high dynamic range of the systems due to a high combined power in a receive (RX) mode. The proposed circuit is based on a differential common source amplifier using capacitive cross-coupling neutralization. The cross-coupled capacitance is implemented with a parasitic capacitance of a turned-off series transistor switch, which operates as the bypass mode in the RX mode. By configuring the series transistor switch as the capacitive cross-coupling neutralization for the TX mode, two single-pole double-through (SPDT) switches are eliminated, which ensures an ultra-compact size and prevents additional losses. Measured gain and $\mathbf{OP}_{1dB}$ in the TX mode are 10.3 dB with about a 12 GHz 3-dB bandwidth and -2.5 dBm at 28 GHz, respectively, with a power consumption of 14.6 mW. Measured insertion loss and $\mathbf{IP}_{1dB}$ in the RX mode are 4.5 dB and 8.7 dBm at 28 GHz, respectively. To the best of our knowledge, this is the first demonstration of the reconfigurable amplifier for the optimal TRX signal distributions in the phased array systems.