A monolithic complex sigma-delta modulator for digital radio

Abstract

II. Complex Filtering An architecture for a 1.9 GHz PCS receiver is described. This architecture uses a single IF and a Complex Bandpass Sigma-Delta Modulator (BPEAM) to digitize the signal at the IF. This demonstrates the feasibility of this type of modulator in I/Q radios. Image rejection is then done in DSI? A fourth order XA modulator has been realized in a 0.8um BiCMOS process for the receiver. The modulator is clocked at 4MHz, with a SNR of 48dB for an oversampling ratio (OSR) of 200 and has a power dissipation of 15OmW with a 5V supply. Most filters have transfer functions that contain conjugate poles and zeros because they use real coefficients. A complex filter can be designed that has non-conjugate poles and zeros which takes a complex-valued input and gives a complex-valued output [6][7][8]. This makes it particularly useful for I/Q (real/imaginary) radio applications. r i Xre(2) A re (z ) m Yre(2)