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Digital Notch filter

by Krishna Sankar on July 14, 2013

digital_notch_filter_frequency_phase_response

In some designs, it may be required to have a digital filter which attenuates a single frequency component with the rest of the frequencies pass through. Filtering out of the power line frequency of 50/60Hz [...]

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Bitwidth in CIC filter

by Krishna Sankar on June 13, 2013

moving_average_comb_integrator_freq_response

The previous article on Cascaded Integrator Comb (CIC) filter discussed the filter structure, the frequency response and it’s usage in upsampling and downsampling. This post will briefly go over the CIC filter, fixed point arithmetic [...]

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BER for BPSK in ISI channel with Zero Forcing equalization

by Krishna Sankar on November 29, 2009

Frequency response Zero Forcing equalizer

In the past, we had discussed BER for BPSK in flat fading Rayleigh channel. In this post, lets discuss a frequency selective channel with the use of Zero Forcing (ZF) equalization to compensate for the [...]

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Eye diagram with raised cosine filtering

by Krishna Sankar on May 1, 2008

Eye diagram following raised cosine filtering with alpha=0.5

We have discussed about probable transmit pulse shaping filter and have observed that raised cosine filtering filtering allows a simpler implementation, albeit at the cost of increased bandwidth. Let us know understand the eye diagram, [...]

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Raised cosine filter for transmit pulse shaping

by Krishna Sankar on April 22, 2008

Time domain response of raised cosine filter

In the previous post on transmit filtering using Nyquist pulse, we had briefly learned that the information symbol with a symbol period can be transmitted without inter symbol interference (ISI) by using Nyquist pulse, . [...]

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Transmit pulse shaping filter – rectangular and sinc (Nyquist)

by Krishna Sankar on April 14, 2008

Transmit spectrum with rectangular and sinc shaped filtering

In the previous post on I-Q modulator and de-modulator, we had briefly mentioned that the a baseband PAM transmission can be modelled as , where is the symbol period, is the symbol to transmit, is [...]

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Digital implementation of RC low pass filter

by Krishna Sankar on December 2, 2007

Step response of a digital RC low pass filter

Thanks to the nice article from Xilinx TechXclusives [XLNX-TECH], let us try to understand the probable digital implementation of resistor-capacitor based low pass filter. Consider a simple RC filter shown in the figure below. Assuming [...]

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Example of Cascaded Integrator Comb filter in Matlab

by Krishna Sankar on July 1, 2007

cic_filter_for_interpolation

Equivalence of Moving Average and CIC filter Let me briefly share my understanding on the cascaded integrator comb (CIC) filter, thanks to the nice article. For understanding the cascaded integrator comb (CIC) filter, firstly let [...]

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Polyphase filters for interpolation

by Krishna Sankar on May 12, 2007

In typical digital signal processing applications, there arises need to increase the sampling frequency of a signal sequence, where the higher sampling frequency is an integer multiple of the original sampling frequency i.e for a [...]

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Zero-order hold and first-order hold based interpolation

by Krishna Sankar on March 25, 2007

In problem 9.14 of DSP-Proakis, the objective is to analyze the effect of zero-order interpolation and first-order interpolation to double the number of samples in the sinusoidal while keeping the sampling frequency unchanged. My take: [...]

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