A one-path quadrature bandpass ΣΔ modulator based on distributed resonators at 25 MHz IF

This paper presents experimental results of a quadrature bandpass sigma-delta (SigmaDelta) modulator based on distributed resonators. The modulator employs transmission lines and transconductors as main components and does not require any switches. In addition, the proposed complex modulator does not require a quadrature mixer in the receiver. As main feature, the modulator architecture introduces an innovative way to produce the I and Q outputs that is immune to path mismatch due to the sharing of all the analog circuitry for both paths. The one-bit second-order modulator chip achieves a dynamic range of 60 dB within a 1 MHz signal bandwidth at 25 MHz and at a clock frequency of 50 MHz. Furthermore, it provides an image rejection of 47 dB. The 0.35 mum BiCMOS chip consumes 28 mW at 3.3 V supply voltage.