This letter proposes a compact 28-GHz front-end (FE) structure that uses a common-gate (CG) low-noise amplifier (LNA) as a transmit/receive switch. The power amplifier (PA) output shares a dc bias with the CG LNA input. When the shared dc bias is high, the state of the LNA becomes passive, and the LNA operates as a turned-off shunt switch in the transmitter (TX) mode. The proposed CG LNA switch allows high isolation and linearity with a TX path insertion loss of 0.07 dB at 28 GHz. On the contrary, when the shared dc bias is low, the state of the PA becomes passive and it results in a receiver (RX) path insertion loss of 0.51 dB at 28 GHz. The path losses of the CG LNA switch are minimized by the RF floating bodies of the PA and the CG LNA. This is implemented in a 65-nm CMOS process occupying a 0.215-mm2 core area. The measured saturation power is 15.3 dBm with 25.1% peak power-added efficiency in the TX mode, and the measured noise figure is 4.9 dB in the RX mode.

中文翻译：

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使用 CG LNA 作为开关的 28 GHz 射频前端结构

这封信提出了一种紧凑的 28GHz 前端 (FE) 结构，该结构使用共栅 (CG) 低噪声放大器 (LNA) 作为发送/接收开关。功率放大器 (PA) 输出与 CG LNA 输入共享直流偏置。当共享直流偏置为高电平时，LNA 的状态变为无源状态，并且 LNA 在发送器 (TX) 模式下用作关闭的分流开关。建议的 CG LNA 开关允许高隔离度和线性度，在 28 GHz 时 TX 路径插入损耗为 0.07 dB。相反，当共享直流偏置较低时，PA 状态变为无源状态，导致接收器 (RX) 路径插入损耗在 28 GHz 时为 0.51 dB。CG LNA 开关的路径损耗通过 PA 和 CG LNA 的 RF 浮体最小化。这是在占用 0.215 平方毫米核心面积的 65 纳米 CMOS 工艺中实现的。