TABLE OF CONTENTS More than easing computational burdens, the digital computer has revolutionized the way we design filters. Any modern treatment of filter design must address strategies which have become practical including real-time tuning, statistical analysis, sensitivity analysis, design centering and optimization. It is now feasible to optimize for desired and customized characteristics while simultaneously considering component losses, parasitics and discontinuities.
Many filter synthesis theories which we use today were developed in an age when computing tools were far less sophisticated [1]. Wonderfully elegant mathematical solutions were found for a variety of filter problems, but idealized assumptions were required to make the process manageable. Today, these idealized symbolic theories form a starting point which is followed by brute force numeric techniques.
In this chapter we will discuss digital computer techniques and software programs available for the development of filters. They may be classified in two broad categories; synthesis and simulation. Synthesis is the process of designing filters by finding the topology and component values or dimensions. Simulation is a process of evaluating a design by calculation and display of the filter responses.
On the upper left in Figure 6-1 are the transmission and return loss responses on an ideal L-C 7th order Chebyshev lowpass filter with a cutoff frequency of 2250 MHz and passband ripple of 0.177 dB. The transmission is plotted on a scale of 6 dB per division and the return loss is plotted on a scale of 3 dB per division. The schematic of the L-C filter...
