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A dual band receiver IC for digital audio broadcasting (DAB) is described in this paper. The chip integrates most of the functions necessary to receive and down convert DAB L-Band (1452 ∼ 1492MHz) and Band3 (174-240 MHz) signals for further baseband processing, including two variable gain LNAs, mixers, VGA, IF amplifiers, L-Band PLL, and Band3 VCO. The overall Band3 receiver gain is 92dB and NF is 4.5dB. L-Band receiver gain is 91dB and NF is 8.9dB. In both bands, gain control ranges are over 84dB and THD remains above 30dBc up to input levels of -14dBm. The linearity and dynamic range of this system can be improved by using an external attenuator that has 20dB variable attenuation. Two AGC stages are implemented in this receiver. With the reference-current-based, programmable AGC design, this receiver provides 8dB range to optimize output level to match the dynamic range of the following A/D converter. The prescalar used in L-band PLL realizes a programmable divide-by-multi-divisor function, 2n - 2, 2n - 1, 2n, and 2n + 1, by utilizing conventional divide-by-4/5 stage with slow and simple logic timing. This circuit was fabricated in TSMC 0.35 μm SiGe process with 3.3V power supply. It consumes 88mA and 65mA for L-Band and Band3 mode, respectively.
Date of Conference: 12-17 June 2005