A 63 dB SNR, 75-mW Bandpass RF Σ∆ ADC at 950 MHz Using 3.8-GHz Clock in 0.25-μm SiGe BiCMOS Technology

A fourth-order continuous-time LC bandpass sigma-delta ADC is designed using a new architecture with only non-return-to-zero feedback DACs to mitigate problems associated with clock jitter, along with individual control of coefficients in the noise transfer function. The ADC performs direct digitization of RF signals around 950-MHz center frequency with a 3.8-GHz clock. The operation of the proposed ADC architecture is examined in detail and extra design parameters are introduced to enhance the operating range and improve the stability of the ADC. Measurement results of the ADC, implemented in IBM 0.25-mum SiGe BiCMOS technology, show SNR of 63 dB and 59 dB in signal bandwidths of 200 kHz and 1 MHz, respectively, around 950 MHz, while consuming 75 mW of power from plusmn1.25-V supply