What is a decimation filter?

Decimation is the process of reducing the sampling frequency of a signal to a lower sampling frequency that differs from the original frequency by an integer value. This lowpass FIR filter is an anti-aliasing filter followed by an M-fold decimator. The decimator passes every Mth sample and discards the other samples.

Why do we need decimation filter?

The most immediate reason to decimate is simply to reduce the sampling rate at the output of one system so a system operating at a lower sampling rate can input the signal. For example, if you double the sample rate, an equivalent filter will require four times as many operations to implement.

What is the filter type of N stage CIC decimation filter?

FIR filters
CIC filters were invented by Eugene B. Hogenauer, and are a class of FIR filters used in multi-rate digital signal processing. The CIC filter finds applications in interpolation and decimation. Unlike most FIR filters, it has a decimator or interpolator built into the architecture.

What is interpolation and decimation filters and why we need it?

• Decimation. – Reduce the sampling rate of a discrete-time signal. – Low sampling rate reduces storage and computation requirements. • Interpolation. – Increase the sampling rate of a discrete-time signal.

What are the main characteristics of anti aliasing filter?

Ensures that bandwidth of signal to be sampled is limited to frequency range. To limit the additive noise spectrum and other interference, which corrupts the signal.

Why do we need downsampling?

Downsampling (i.e., taking a random sample without replacement) from the negative cases reduces the dataset to a more manageable size. You mentioned using a “classifier” in your question but didn’t specify which one. One classifier you may want to avoid are decision trees.

How does a CIC filter work?

An interpolating CIC filter has zeros inserted between its input samples reducing its gain by a factor of 1/R to account for the zero-valued samples, so the net gain of an interpolating CIC filter is (NR)M/R.

How does a polyphase filter work?

A polyphase quadrature filter, or PQF, is a filter bank which splits an input signal into a given number N (mostly a power of 2) of equidistant sub-bands. These sub-bands are subsampled by a factor of N, so they are critically sampled.

Why downsampling is required?

How is the output of a decimation filter converted?

The output from the discrete-time analog integrator is converted using an m-bit ADC to produce the oversampled digital signal. Finally, the decimation filter removes outband quantization noise. Further decimation processes can change the oversampling rate back to the desired sampling rate for the output digital signal w ( m ).

How is a discrete time signal subtracted in a decimation filter?

This discrete-time signal is subtracted by the analog output from the m -bit DAC, converting the m -bit oversampled digital signal y(n). Then the difference is sent to the discrete-time analog integrator, which is implemented by the switched-capacitor technique, for example.

What is the decimation factor of sigma delta ADC?

Functional diagram for the sigma-delta ADC. The chip produces a 1-bit data stream, which will be filtered by the integrated digital filter to complete ADC. The digital filter’s user-selectable decimation factor offers flexibility as conversion resolution can be reduced in exchange for a higher data rate or vice versa.

How are filters and decimation accomplished in Cascade?

The filtering and decimation in the first stage is accomplished by connecting up to five accumulators in cascade. The accumulators yield the transfer function where n is the number of accumulators. The accumulators represent first-order recursive filters. Next follows the decimation.