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

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 plusmn1.2 dB over the 23 dB gain range, an output P1 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 mum times 1150 mum including the bondpads.