필터 설계

Discusses IIR halfband stages in multistage decimators and interpolators.

Design classic IIR filters. The example initially focuses on the scenario where critical design parameter is the cutoff frequency at which the power of the filter decays to half (–3 dB) the nominal passband value.

Design peak and notch filters. Filters that peak or notch at a certain frequency retain or eliminate a particular frequency component of a signal. The design parameters that you can set for such filters are the frequency at which you want the peak or notch and the 3-dB bandwidth or the Q factor. Using these specifications and by increasing the filter order, you can design filters that more closely approximate an ideal filter.

Design filters with customized magnitude and phase specifications. Many filter design problems focus on the magnitude response only, while assuming a linear phase response through symmetry. In some cases, however, the desired filter needs to satisfy constraints on both magnitude and phase.

Design least Pth-norm FIR filters with the firlpnorm function. This function uses a least-Pth unconstrained optimization algorithm to design FIR filters with arbitrary magnitude response.

Design optimal IIR filters with arbitrary magnitude response using the least-Pth unconstrained optimization algorithm.

Design lowpass FIR Nyquist filters. It also compares these filters with raised cosine and square root raised cosine filters. These filters are widely used in pulse-shaping for digital transmission systems. They also find application in interpolation/decimation and filter banks.

Design filters for decimation and interpolation. Typically lowpass filters are used for decimation and for interpolation. When decimating, lowpass filters are used to reduce the bandwidth of a signal prior to reducing the sampling rate. This is done to minimize aliasing due to the reduction in the sampling rate. When interpolating, lowpass filters are used to remove spectral images from the low-rate signal. For general notes on lowpass filter design see the example on Design Lowpass FIR Filters.

Design arbitrary group delay filters using the fdesign.arbgrpdelay filter designer. This designer uses a least-Pth constrained optimization algorithm to design allpass IIR filters that meet a prescribed group delay.

Use Farrow structures to design digital fractional delay filters. Digital fractional delay filters are useful tools to fine-tune the sampling instants of signals. They are typically found in the synchronization of digital modems where the delay parameter varies over time. This example illustrates why the Farrow structure is a popular method for implementing time-varying FIR fractional delay filters.

Design an implementation of fractional delay FIR filters.