Noise Optimized Channel Selection Filter Design for WCDMA

A low noise 6th-order elliptic low-pass filter is proposed and implemented. For the high level integration of multi-standard wireless terminal at low cost, the direct conversion architecture is favored for the RF transceiver, and a low noise channel selection filter with enough out-of-band suppression takes a critical role for the direct conversion receiver. For the noise optimized filter design, a noise analysis, design procedure and techniques are described for a biquad circuit and the 6th-order elliptic filter. The filter is implemented in a 0.35μm BiCMOS technology and has the 3dB cutoff frequency of 2.3MHz. The chip size is 1.0×1.15mm 2 . The measurement results show that the noise characteristics are optimized by proper allocation of the biquad circuit component values and biquad placement as proposed. And also, the filter shows good linearity. The filter consumes 3.8mA current at 1.8V supply and provides about 60dB