### Philip Oakley (@philipoakley)

Retired Engineer working in Defence Electronics, and numerous other areas. BSc (first) in Applied Physics and Electronics, Durham University 1976.

## Re: How to avoid harmonic distortions in a DAC?

The assumption about the Nyquist harmonics and sample frequency isn't quite correct, as it (harmonics etc) also depends on where the non-linearity is within the...

## Re: Sampling Rate conversion with arbitrary and variable ratios

You give a 7 digit real value (1.xx...xx) but don't give any further criteria or requirements that would allow a trade off of techniques as to, say, how long the...

## Re: fft process gain revisited

Hi Kaz,Your viewpoint is a valid one, however it is one of many 'useful' viewpoints, each embodying their own perspective as to what it is they need scaling, preferably...

## Re: mitigating phase shift

How fast do you want to track the line voltage? Is this single phase or three phase? Do you need an estimate every cycle, or half cycle, or faster (3ph)? These are...

## Re: IQ mag: Integer approximation of square root of the sum of two squares

Years ago (on a Sinclair QL IIRC) I did calcs regarding adding rms noise equal to 1/2 lsb and found that with sufficient averaging, you got at least 8 extra bits...

## Re: IQ mag: Integer approximation of square root of the sum of two squares

It is also worth reflecting on how this affects investigations of signals in noise and the apparent sharpness of the transition. In a broad band signal you can...

## Re: FFT question

I'm not familiar with 'liquid'. The fftw3 does work, but the user interfaces can make implicit assumptions that don't match what you expect (true for all implementations)One...

## Re: FFT question

Are you using a full complex fft, or one that assumes symmetry of the positive and negative spectrums. Many FFTs make the assumption of real valued inputs, such...

## Re: Applications for a new FFT algorithm

Vaguely sounds like the Lifted wavelet transforms, with the wavelet transform being seen as cascaded short ffts or FIR filters. Still sounds interesting. Definately...

## Re: Unable to monitor the speed (rpm) of motor eQEP module : TI C2000 F28069M

In line with the other replies, try explaining the code to a video recording as if you'll be publishing the explanation of how to debug to YouTube (other platforms...

## Re: How "Oversampling" works for determining max amplitude for audio applications?

While it is true that oversampling doesn't add any more data, what it does provide is extra spaces for the smooth interpolation of the spectrum to better estimate...

## Re: Very efficient (or parallel) Eigen solution for complex symmetric Matrix

Just thinking out loud here. If the matrix is split into a complex conjugate part and a residual part (which would be complex and could be off diagonal), does that...

## Re: changing FFT resolution of known sweep signal leads to unexplained spectrum

As @krasin notes the missing signal frequencies appear in the second half of the signal. That will be because it's a chirp, so the frequency changes with time (=...

## Re: changing FFT resolution of known sweep signal leads to unexplained spectrum

My impression is that 'gap' in the frequency band is, as you expect, caused by the undersampling of the signal. You will have a period where you have an almost fs/2...

## Re: Phase brake in tonal signal and frequency estimation

Notice where the nulls stay aligned and ponder why is that? Also beware using the same analysis technique as used for generating the problem (i.e. digital sampling...

## Re: Using noise to increase resolution of ADC

IIRC, I did my original calculation on a Sinclair QL to see what linearity was possible out of filtering sample noise on an ADC..A side fact is looking at the 'knee'...

## Re: Using noise to increase resolution of ADC

With ideal Gaussian noise, with rms = 0.5 bits (of the ADC), then you can gain upto 8 extra bits by averaging a long sequence of results for a constant DC level...

## Re: Modulation in laser satellite communication

Hi Adilko, It's not that it's impossible, rather it is just that you need either sneaky techniques or careful selection of the method. I don't think the laser...

## Re: Modulation in laser satellite communication

Remember that "phase" is measured in metres (or millimetres, or microns) as it is 'fractions of a wavelength'.So shifting to optical frequencies, where the wavelength...

## Re: Can you find the illegal step?

This is mathematics, not real world, isn't it? The error, if there is one ;-), is the last step where 'b' should be subtracted from both sides, resulting in the...

## Re: Recent FFT benchmarking report

Thanks, looks useful. Always like stuff on FFTs and its derivatives.

## Re: Digital IIR Parallel Implementation

Do make sure that if x[0...n] = 1, that you have stability, rather than an exponential 'explosion'. That is, don't forget the effective multiplier for the x[n]...

## Re: Overdriven Sine Wave through DSP Filter

Some quick thoughts.There are two things to consider: the amount of overdrive, i.e. just a little clipping, or large overdrive giving a trapezoid shape, or the massive...

## Re: Off by one windowing

Is there a typo here"0 2÷3 2÷3" ?Should it read"0 1÷3 2÷3", i.e. ~ "0 0.333333 0.666666" ?If not, maybe a slight expansion of the text to tease out more of the...

## Re: Recover signal from the real part of IFFT

Also, ultimately, the transmitted signal is a purely real signal, sampled in the time domain, thus all those complex parts are mathematical artefacts with various...

## Re: ADC can't perceive MLS (maximum length sequence)

Definitely start with a lower sequence rate, and lower them until you can see the sequence cleanly.Also consider doubling the 'sample/bit rate' in the sense that...

## Re: Real Numbers

You forgot the distinctions around zero.Some number systems have no zero, such as Roman numerals (and no negative).We also have the subtle distinction between additive...

## Re: phase error correction

Are you simply averaging the theta values, which have roll-over, as that roll over can cause a significant non-linearity. You could average the complex phase (i.e....

## Re: Rice channel + AWGN with lower BER than AWGN alone ??

Just a quick thought, without any real 'thinking' - do those two delayed signals simply amount to a small phase shift that effectively increase the size of the signal,...

## Re: How to test my FFT implementation?

Random noise can produce wildly random results (well, because..). It's a reasonable approximation but the statistics aren't always as good is hoped.You didn't say...

## Re: What is the maximum output amplitude of an IIR filter?

The maximum value is determined by the initial y[0] {aka y(1)} value copied from x[0] {x(1)}, so the randomised trial will get rather random results because the...

## Re: What is the maximum output amplitude of an IIR filter?

so, I think you have: y[n] = 0.98*y[n-1] + (x[n] - x[n-1])Assuming that y[-1] = 0, you have a 2% decay on any existing y[n-1] value, plus the difference between...

## Re: What is the maximum output amplitude of an IIR filter?

The Wikipedia 'Stability' section https://en.wikipedia.org/wiki/Infinite_impulse_res... maybe a useful place to start.Separating the variables will be part of the...

## Re: Matlab Basic Functions Reference (pdf)

Maybe it needs    A=[1 2 3 4 5 6]; A(:)and    B = [1 2 3; 4 5 6]; B(:)to highlight the internal ordering. (Perhaps along with sum(A) and sum (B) just to clarify..)The...

## Re: Matlab Basic Functions Reference (pdf)

It would be nice if they also included a note/clarification about the row/column, X-Y, angle conventions for 'row vectors' etc.The conventions can confuse many,...

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