A complex quadrature charge-sharing (CS) technique is utilized to implement a discrete-time band-pass filter with a programmable bandwidth of 20–100 MHz. The BPF is a natural part of a cellular superheterodyne receiver and completely determines the receiver frequency selectivity. It operates at the full sampling rate (4×) (described in Chapter 2 of up to 5.2 GHz corresponding to the 1.2 GHz RF input frequency, thus making it free from any aliasing or replicas in its transfer function. Furthermore, the advantages of CS-BPFover other band-pass filters, such as N-path, active-RC, Gm-C, and biquad are described. A mathematical noise analysis of the CS-BPF and the comparison of simulations and calculations are presented. The entire 65 nm CMOS receiver, which does not include a front-end LNTA for test reasons, achieves a total gain of 35 dB, IRN of 1.5 nV/?Hz, out-of-band IIP3 of +10 dBm. It consumes 24 mA at 1.2 V power supply.

One of the main building blocks in a receiver is a low-pass filter (LPF) used at the baseband. This block is responsible for selecting the desired channel. In zero-IF receivers, this block is placed directly after the RF downconversion mixer. In a high-IF receiver,the LPF is required after a second downconversion from the IF to baseband. In addition to wireless communication applications, integrated LPFs are the key building blocks in various other types of applications, such as hard disk drive readchannels,videosignalprocessing,smoothingfilteringinaDAC,andantialiasingfilteringbeforea sampling system. The noise of these filters is one of the key system-level concerns. This noise can be usually traded off with the total filter capacitance and, consequently, total power and area. Therefore, for a given system-level noise budget, a filter with a lower noise coefficient reduces the area and power consumption. On the other hand, the linearity of the filter should be high enough to maintain the fidelity of the wanted signal.