Contents
Which is the best filter to use for decimation?
To implement the filtering part, you can use either FIR or IIR filters. To implement the downsampling part (by a downsampling factor of “M”) simply keep every Mth sample, and throw away the M-1 samples in between. For example, to decimate by 4, keep every fourth sample, and throw three out of every four samples away.
How is decimation in frequency ( diffft ) splitted?
In DIF N Point DFT is splitted into N/2 points DFT s. X (k) is splitted with k even and k odd this is called Decimation in frequency (DIF FFT). In DIF N Point DFT is splitted into N/2 points DFT s.
What is the stopband lower frequency in decimation?
The passband lower frequency is zero; the passband upper frequency is whatever information bandwidth you want to preserve after decimating. The passband ripple is whatever your application can tolerate. The stopband lower frequency is half the output rate minus the passband upper frequency.
When to use decimation before or after downsampling?
However, since the original signal has components up to 10 kHz, you must lowpass-filter the signal prior to downsampling to remove all components above 5 kHz so that no aliasing will occur when downsampling. This combined operation of filtering and downsampling is called decimation.
Which is larger the decimation factor or savings?
Therefore, the larger the decimation factor is, the larger the savings, percentage-wise. A simple way to think of the amount of computation required to implement a FIR decimator is that it is equal to the computation required for a non-decimating N-tap filter operating at the output rate.
How are second order biquadratic filters used in IIR?
Typically second order biquadratic sections (SOS) are chosen for the low order filters and implemented using the Direct Form 1 structure shown in Figure 2. Each SOS requires 4 multiplies, 3 adds and some rounding to reduce the bit width for the next filter in the cascade.
Can a IIR Cascade take advantage of zero inputs?
The IIR filter cascade cannot take advantage of the zero inputs to reduce computation because of feedback paths in each SOS. IIR Filters for polyphase decomposition In this paper we start with an architecture that maps to a polyphase decomposition and show how this leads to very low complexity filters.
Is the decimating fir the same as the regular fir?
A decimating FIR is actually the same as a regular FIR, except that you shift M samples into the delay line for each output you calculate.