Conventional multi-gate pseudomorphic high-electron-mobility transistors (pHEMTs) in the off-state generate larger distortion than single-gate pHEMTs in RF switch applications. To reduce the distortion, the intergate region of multi-gate pHEMTs must be connected to the source and drain with resistors to be biased at the same DC voltage. The intergate region of multi-gate pHEMTs is too small to have an external electrical contact, so intergate-channel-connected pHEMTs (IGCC-pHEMTs) have been developed. IGCC-pHEMTs have a meander gate structure, where one side of the gate is connected to a metal wire layer, and the other is applied for an intergate region contact that does not widen the distance between the gates. A single-pole double-throw (SPDT) switch with IGCC-pHEMTs was fabricated by using a standard 0.5 µm InGaAs pHEMT process. A SPDT switch with IGCC-pHEMTs is confirmed to have almost same small-signal properties and generate lower distortions.

An RF IC for a 1.1-V VHF paging receiver is developed. In order to reduce the number of components, it employs direct-conversion frequency shift keying (FSK) architecture. The RF IC adopts two new gain control circuits so as to achieve a wide input dynamic range with only a 1.1 V power supply. One is a low-voltage, low-noise, low-distortion RF amplifier and the other is a low-voltage AGC amplifier. By applying these new circuit technologies, the RF IC achieves a voltage gain of 50.5 dB and a noise figure of 4.3 dB with only 2.0 mW power consumption. Overall, the paging receiver achieves a high sensitivity of -130 dBm and low-intermodulation sensitivity of -37 dBm with bit error rate of 310-2. This paper describes the new high-frequency low-voltage circuit technologies applied in the RF IC.