A Temperature-Independent Transmitter IC for 5.8-GHz DSRC Applications

Abstract

This paper describes a transmitter integrated circuit (IC) for 5.8-GHz dedicated short-range communication applications. It consists of a baseband variable-gain amplifier (VGA) and an amplitude-shift-keying (ASK) modulator with an output amplifier. The VGA has exponential gain control characteristics. The proposed temperature-independent exponential gain control is realized with a voltage-to-current converter and n-p-n bipolar transistors. The VGA is powered by 3.3 V with 5 mA. The ASK modulator utilizes the Gilbert topology and consumes 32 mA of current with 3.3-V supply. The conversion gain (in decibels) of the transmitter IC is varied linearly from +5.3 dB to -17.7 dB with respect to the control voltage from 0.5 V to 2.5 V. It achieves gain errors of less than +/- 1.2 dB over the 23 dB gain range, an output PI dB of 3.5 dBm at the maximum gain of 5.3 dB, and an adjacent channel power lower than -45 dBc. It occupies an area of 1770 mu m x 1150 mu m including the bondpads.