A direct conversion receiver for W-CDMA, which consumes extremely low power, is presented. The receiver consists of a low-noise amplifier (LNA) IC, a receiver IC and other passive components such as an RF-SAW (Surface Acoustic Wave) filter. The receiver IC includes a quadrature demodulator (QDEM) with a local oscillator (LO) divider, low-pass filters (LPFs) for channel selection, variable gain amplifiers (VGAs) with dynamic range of 80 dB, and a fractional-N synthesizer. The power consumption for the entire receiver chain was only 30.8 mA at supply voltage of 2.7 V.

This paper presents a single-chip RF tuner/OFDM demodulator for a mobile digital TV application called “1-segment broadcasting.” To achieve required performances for the single-chip receiver, a tunable technique for a low-noise amplifier (LNA) and spurious suppression techniques are proposed in this paper. Firstly, to receive all channels from 470 MHz to 770 MHz and to relax distortion characteristics of following circuit blocks such as an RF variable-gain amplifier and a mixer, a tunable technique for the LNA is proposed. Then, to improve the sensitivity, spurious signal suppression techniques are also proposed. The single-chip receiver using the proposed techniques is fabricated in 90 nm CMOS technology and total die size is 3.26 mm 3.26 mm. Using the tunable LNA and suppressing undesired spurious signals, the sensitivities of less than -98.6 dBm are achieved for all the channels.

Since a receiver (RX) and a transmitter (TX) are operated simultaneously in a WCDMA transceiver, noise and intermodulation distortion performances of a low-noise amplifier (LNA) are degraded by a large leakage signal from the TX. The degradation of the distortion due to the large leakage signal from the TX has been reported in some previous works, but to our best knowledge, there are no reports about the degradation of noise figure (NF) in a LNA due to the large leakage signal from the TX. In this paper, a 900-MHz LNA for WCDMA terminal with high tolerance for a leakage signal from the TX is proposed. Suitable designs of an input matching circuit and a trap circuit are adopted to improve the tolerance for the leakage signal from the TX. The LNA using the proposed techniques is fabricated using SiGe-BiCMOS process. The measured degradation of NF due to the leakage signal from the TX is suppressed to only 0.12 dB.