A 0.25-dB-Step, 68-dB-Dynamic Range Analog Baseband With Digitally Assisted DCOC and AGC for Multi-Standard TV Applications

Abstract

This brief presents a low noise, high dynamic range (DR), high linearity, and high selectivity analog baseband (BB) for multi-standard TV applications. A customized sixth-order low pass filter with two additional zeroes Chebyshev-I filter is adopted to enhance the average adjacent channel rejection (ACR) and the attenuation at 5.25 MHz, and a novel programmable gain amplifier (PGA) realizes accurate gains with a fine-tuning gain step of 0.25 dB. The digitally assisted real-time dc offset cancellation (DCOC) loop can prevent the BB chain from saturation robustly with a low residual output dc offset voltage (DCOV) and an extremely low cut-off frequency. The digitally assisted complementary cumulative distribution function (CCDF)-based on-chip automatic gain control (AGC) loop implements reliable amplitude control for digital TV signals with a large peak to average power ratio (PAPR). The BB chain fabricated in a 0.18 ${\mu }\text{m}$ CMOS process occupies an area of 1.2 mm2 and consumes a current of 21.3 mA from 1.8-V supply including the output buffer. It achieves a maximum gain of 62 dB and a DR of 68 dB with 0.25 dB minimum step. The attenuation at 5.25 MHz is 48.6 dB and the average ACR is 38.2 dB. The measured equivalent input-referred noise voltage is 22 ${\mathrm{ nV/}}\sqrt {\mathrm{ Hz}} $ , out-of-band IIP3 of 37.61 dBV, and out-of-band IIP2 of 77.19 dBV at 56 dB gain. The residual output DCOV is less than 5 mV and the minimum 3 dB cut-off frequency is 100 Hz when BB operates in the maximum gain of 62 dB.