## Anti Aliasing of Arbitrary Waveforms

Started by in comp.dsp13 years ago 209 replies

What are the common method(s) for preventing aliasing of arbitrary waveforms generated within a DSP application? I understand that waveforms...

What are the common method(s) for preventing aliasing of arbitrary waveforms generated within a DSP application? I understand that waveforms supplied as analog signals and presented to an ADC must first be lowpass filtered to remove harmonics above the Nyquist frequency, but what about generated waveforms? I know about BLIT and it won't be appropriate for completely arbitrary waveforms. I'...

## Sampling a signal corrupted by AWGN

Started by in comp.dsp13 years ago 10 replies

Let us assume that we have a bandlimited signal (with maximum frequency f_n) corrupted by additive white Gaussian noise. Before we can sample...

Let us assume that we have a bandlimited signal (with maximum frequency f_n) corrupted by additive white Gaussian noise. Before we can sample this signal, we pass the signal through an ideal anti-alias filter with cut-off frequency f_c > =f_n to avoid noise aliasing. The output of the anti-aliasing filter is fed into a matched filter matched to the symbol rate, (1/T)> =2f_n (i used f_n here because

## Order of LPF at DAC output

Started by in comp.dsp12 years ago 3 replies

Hi, In the case of an anti-aliasing filter used prior to an ADC, the filter order is derived from the cut-off frequency being twice the...

Hi, In the case of an anti-aliasing filter used prior to an ADC, the filter order is derived from the cut-off frequency being twice the maximum frequency of the signal, stop-band attenuation and pass-band ripple defined by the ADC resolution. In the case of DAC, where LPF is basically used to smooth out the quantisation steps, how do we decide the filter order. It does seem intuitive that the be...

## Design of anti-alias filter for ADC, with oversampling and averaging

Started by in comp.dsp12 years ago 1 reply

Hi, I am trying to design proper anti-aliasing filters for a new hobby project (digital control of a quad-rotor flying robot - see...

Hi, I am trying to design proper anti-aliasing filters for a new hobby project (digital control of a quad-rotor flying robot - see previous post for more questions). Here are the specifics: * My sensors are analog MEMS accelerometers and gyroscopes. I'll have at least 6 sensors to process, at least initially. * I will be using a microcontroller with 10-12 bit built-in ADCs to process t...

## Why use an anti aliasing filter with an energy meter.?

Started by in comp.dsp12 years ago 10 replies

The following document says on page 5 an anti aliasing filter is used on the A/D input channels of an energy meter. Warning the document is 31...

The following document says on page 5 an anti aliasing filter is used on the A/D input channels of an energy meter. Warning the document is 31 pages long, only click on the link if you have a broadband internet connection. http://focus.ti.com/lit/an/slaa409a/slaa409a.pdf. My understanding is you only need an anti aliasing filter if you want to reconstruct the signal or find the frequency c...

## Anti-aliasing advice for de-interleaved signals

Started by in comp.dsp11 years ago 36 replies

Hi everyone - this is my first post here. It's about time I joined a DSP forum. I need some advice related to a measurement system. The system...

Hi everyone - this is my first post here. It's about time I joined a DSP forum. I need some advice related to a measurement system. The system samples at 1 kHz but between every sample the input to the DAQ is switched between two inputs. The result is that the acquired signal, at 1 kHz, is two interleaved signals at 500 Hz each. I would then like to go on to separate the two signals, which a...

## Anti Aliasing a NI 6259 BNC Daq System

Started by in comp.dsp10 years ago 6 replies

Hello, I am trying to record 8 channels of analog data using an NI 6259 BNC Data acquisition system. The Daq system has a built in lowpass anti...

Hello, I am trying to record 8 channels of analog data using an NI 6259 BNC Data acquisition system. The Daq system has a built in lowpass anti alias filter, but it has a much higher cut off frequency than what i need (i want a 500Hz cutoff). Does anyone know of a good 8 channel programmable/non programmable anti alias filter. I have also been suggested to use a software filter, but i though...

## using IIR or FIR to implement the lowpass filter for downsampling?

Started by in comp.dsp10 years ago 12 replies

For downsampling (decimation) one normally uses low pass filter before downsampling (anti-aliasing filter). I have thought that FIR is the...

For downsampling (decimation) one normally uses low pass filter before downsampling (anti-aliasing filter). I have thought that FIR is the best choice here for the low pass filter implementation for this case. But I was reading this page: http://www.dspguru.com/dsp/faqs/multirate/decimation and it said in 2.3.1 under "How do I implement decimation?" "To implement the filtering part...

## Anti-Aliasing filters with sigma-delta A/Ds

Started by in comp.dsp9 years ago 11 replies

Do you still require an anti-aliasing filter with sigma-delta A/D's? I am guessing yes but very low order. A/D I am testing seems to have an...

Do you still require an anti-aliasing filter with sigma-delta A/D's? I am guessing yes but very low order. A/D I am testing seems to have an excellent roll-off without any filter at all. Hardy

## How to find phase shift of signal through a system

Started by in comp.dsp9 years ago 2 replies

Hi, Signal from the sensor passes through the following blocks in my system - Ac Coupling circuit, Anti-Aliasing filter and then goes to DSP...

Hi, Signal from the sensor passes through the following blocks in my system - Ac Coupling circuit, Anti-Aliasing filter and then goes to DSP controller where it is low-pass filtered twice. I want to calculate the total phase shift introduced by the system at frequency 50Hz. Following are the required data : Phase Delay Group Delay ...

## 10MHz signal sampling - which DSP?

Started by in comp.dsp8 years ago 8 replies

Hello, i would like to process an analog signal, coming out from a photodiode with a maximum frequency content of 7-10MHz. Here my idea...i...

Hello, i would like to process an analog signal, coming out from a photodiode with a maximum frequency content of 7-10MHz. Here my idea...i don't know if it is something correct or not... i need your help... 1. A/D conversion, trying to aversampling the signal (at least 40-50MSPS) - anti aliasing filter to be evaluated (9-10 bits are enough) 2. CPLD of small FPGA after the DAC (maybe a Ma...

## software anti-aliasing filter.

Started by in comp.dsp7 years ago 27 replies

Hey guys, I designed a system to acquire certain physiological signals and recorded these signals using a data acquisition card (agilent u2531a...

Hey guys, I designed a system to acquire certain physiological signals and recorded these signals using a data acquisition card (agilent u2531a specifically). the problem is when designing the circuit i was unable to place an anti-aliasing filter before feeding the signal to the data acquisition device. The card does not have a software selectable filter at the input stage either. i