Analogue realisation of integrated FIR filters

The paper presents a unified approach to the design of analogue finite impulse response (FIR) filters. As an analogue realisation the multiphase switched-capacitor technique was chosen owing to its high precision and high packing density in CMOS technology. The proposed method allows different structures of the filters containing different number of amplifiers to be controlled by different clock signals, providing the best solution taking into account the maximum frequency range and the cost of the chip. Four prototypes of the filters were designed as one integrated circuit using 2 μm double-poly CMOS technology. Measurements made on the test chip confirm the computer simulations. Implementation of interpolation units for analogue FIR filters derived from transversal direct diagram of digital FIR filters is discussed. The linear interpolator provides an improvement to the frequency characteristic of the prototype analogue FIR filter. Computer simulation of the resulting filter has been performed