## Forums comp.dsp

## Math is Weird

inYes, weird! Three lines can not all be perpendicular to each other, but signals can all be orthogonal. What's up with that? Why doesn't...

Yes, weird! Three lines can not all be perpendicular to each other, but signals can all be orthogonal. What's up with that? Why doesn't someone fix geometry? -- Rick

## LTE, FFT, OFDM

inHello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth...

Hello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth of 1.4/3/5/10/15/20 MHz. I don't know how these N point FFT are selected for OFDM implementation. Let us take 1.4 MHz and 128 point FFT for example. 128 point FFT has N value of (2^N = 128) of 7. With a sub-carrier spacing of 15 KHz, this covers = 7*15 KH...

## Orthogonol signals

inHello, I would like to know definition of orthogonal signals and why they are significant in communication? Thanks,...

Hello, I would like to know definition of orthogonal signals and why they are significant in communication? Thanks, --------------------------------------- Posted through http://www.DSPRelated.com

## Most commonly used window functions

inThe window functions that I generally see are: Hamming, Hann (why call it Hanning?), Blackman, and Blackman-Harris (feel free to add...

The window functions that I generally see are: Hamming, Hann (why call it Hanning?), Blackman, and Blackman-Harris (feel free to add your favorite here). Obviously they're all still around because they're useful somewhere. But I'm curious about which is good for what application. The thing that prompted this question:..I just saw an app that had hard-coded Blackman-Harris for doing a STFT...

## Shannon's channel capacity equation

inHello, Probably a very fundamental question. The channel capacity is given by, C = BW . log2(1+S/N) Here, for a given bandwidth, I can...

Hello, Probably a very fundamental question. The channel capacity is given by, C = BW . log2(1+S/N) Here, for a given bandwidth, I can increase the rate of data transfer by different encoding schemes. QAM64,256 etc. being some of them. So, where is the encoding method taking into account in the above equation? Thanks, --------------------------------------- Posted through http://www.D...

## DSP - a reprise

inAlimentary Fourier Anal-ysis ---------------------------- (C) Copyright 1997 Gareth Alun Evans...

Alimentary Fourier Anal-ysis ---------------------------- (C) Copyright 1997 Gareth Alun Evans G4SDW The Fourier Transform is rather like the Human Alimentary canal.... The Alimentary Canal takes food, and then transforms it into something that is a function of the rear end, and hence may be referred to as, "The Food-Rear Transform". T...

## IIR filter and intermittent 50 Hz noise

Hi all, I'm trying to filter out 50 Hz noise which intermitelly appears on the input signal, I've been trying to use a 6th order IIR filter but...

Hi all, I'm trying to filter out 50 Hz noise which intermitelly appears on the input signal, I've been trying to use a 6th order IIR filter but results are unsatisfied: http://www.jrdltd.co.uk/data/noise.png Is there any way to filter out such intermittent noise correctly without massive oscillation at transitions, please? Can you please point me to the resource where I could read about t...

## Frequency domain (DFT) vs. (finite) impulse response

inHi, From a physical, continuous-time system I obtain the following frequency response by sweeping frequencies up to...

Hi, From a physical, continuous-time system I obtain the following frequency response by sweeping frequencies up to fs/2=100MHz: http://snag.gy/jo8kM.jpg To my understanding, the impulse response is given the IDTFT which is approximately the IDFT (if the swept input signals are long enough/the frequency resolution is sufficiently high): http://snag.gy/weTTz.jpg http://snag.gy/wIgmX...

## Baseband Bandwidth

inHello, With respect to wireless communication, I have a question I would like to clarify. I have some trouble conceptually appreciating the...

Hello, With respect to wireless communication, I have a question I would like to clarify. I have some trouble conceptually appreciating the bandwidth on the baseband side. For example, if the baseband bandwidths available are 5 & 10 MHz then does it mean that one can transmit with double rate on 10 MHz signal compared to 5 MHz signal? In other words, is the user data carried out at the ...

## De Emphasis FIR Filter

inHi all, do you know if there is a way to make a de-emphasis filter a FIR filter. I already have a FIR filter implemented and I would like to...

Hi all, do you know if there is a way to make a de-emphasis filter a FIR filter. I already have a FIR filter implemented and I would like to just load it with coefficients of de-emphasis FIR. Can approximation of IIR filter be done with FIR filter? If I had an impulse and let it throught IIR filter and took the output, could that output be a FIR filter coefficients? Thank you in adv...