A 4GHz 4th-Order Passive LC Bandpass Delta-Sigma Modulator with IF at 1.4GHz

A 4th-order bandpass DeltaSigma modulator utilizes a novel passive LC continuous-time DeltaSigma architecture to achieve the high IF (pass band) frequency (1.4GHz). A 3-bit quantizer is used to improve wideband performance. A novel architecture of noise-shaped quantizer is used to noise shape the DAC mismatch without introducing extra loop delay. Eight 2nd-order LC modulators are used for noise shaping with minimal transistor count and power consumption. Implemented with 5195 InP HBT transistors, this modulator achieved 76dB SNR and 90dB dynamic range in 1 MHz bandwidth at 1.4GHz with a 4GHz sample rate