Questions tagged [dsp-puzzle]
21 questions
15
votes
2 answers
How to build a phase shifter with arbitrary phase shift
Fred, a DSP engineer, goes to his favorite DSP store to do some shopping.
Fred: Hi, I'd like to buy a phase shifter.
Shop assistant: Hmm, what exactly do you mean?
Fred: Well, you know, if you put in a sinusoid like $x(t)=\sin(\omega_0t)$ you get…
Matt L.
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12
votes
9 answers
Where is the flaw in this derivation of the DTFT of the unit step sequence $u[n]$?
This question is related to this other question of mine where I ask for derivations of the discrete-time Fourier transform (DTFT) of the unit step sequence $u[n]$. During my search for derivations I found one which is amazingly simple. I first saw…
Matt L.
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8
votes
2 answers
Gaussian FIR filter with no multipliers?
What is the simplest way to implement a Gaussian FIR filter with unity gain coefficients and no multipliers?
Please preface your answer with spoiler notation by typing the following two characters first ">!"
Note: A Gaussian FIR filter is an FIR…
Dan Boschen
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7
votes
3 answers
Nyquist's Stability Criterion and Cauchy's Argument Principle
Background:
Nyquist's Stability Criterion for linear-time-invariant systems makes use of Cauchy's argument principle to determine if any zeros in the characteristic equation are in the right-half plane (positive real roots), given a closed loop…
Dan Boschen
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6
votes
1 answer
2nd Order Type 2 PLL for Tracking Frequency Error
This is a "DSP Puzzle", Please preface your answer with spoiler notation by typing the following two characters first ">!" as the intention is for readers to think through what the solution might be first (the ones that want to participate, others…
Dan Boschen
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6
votes
1 answer
Simplest All Digital GMSK Modulator
What is the simplest way to implement an all digital GMSK modulator with no multipliers? The implementation approach should be applicable to GMSK modulation with BT=0.5 or less (where intentional ISI is introduced to obtain higher spectral…
Dan Boschen
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6
votes
3 answers
More Simultaneous Dynamic Range with Fixed Point or Floating Point?
What data path would have more simultaneous dynamic range: 32 bit fixed-point or 32 bit floating-point? Why?
To clarify "simultaneous dynamic range": This is the ability to discern strong and weak signals at the same time, while dynamic range is…
Dan Boschen
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5
votes
2 answers
Double the "speed", double the frequency?
Usually, when some sample is played-back at twice the rate it was recorded, the pitch of the recording sounds an octave higher.
For example: $g(t) = \sin(2 \pi f t)$ and $g(2t) = \sin(2 \pi f 2 t) \implies \sin(4 \pi ft)$. Where $f$ is a given…
A_A
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4
votes
1 answer
Convert a Park McClellan FIR Solution to Achieve Stop-band Roll-off
Often it is more desirable to have a roll-off versus frequency of the rejection in the stopband; for example resampling filters where all the alias image locations fold into the first Nyquist Zone. What is a VERY simple change you can make to the…
Dan Boschen
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4
votes
1 answer
How do you simultaneously undersample and oversample?
"Undersampling" and "Oversampling" are common terms when referring to the choice of sampling frequency for analog to digital data conversion. Is it possible to Undersample and Oversample a waveform at the same time? Examples showing why or why not…
Dan Boschen
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4
votes
1 answer
Simulation of a Frequency ramp
This might be an easy one!
Please preface your answer with spoiler notation by typing the following two characters first ">!"
Given the following equation that describes a cosine wave as a function of time:
$$m(t) = \cos(2\pi f t) $$
We know that…
Dan Boschen
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3
votes
1 answer
Algorithm to Count Zeros Outside Unit Circle for FIR Filter
As detailed in this post Can I set a constraint on the first tap of an FIR filter such that its inverse is stable? I show how Cauchy's Argument Principle can be used to easily confirm if an FIR filter is minimum phase, meaning all zeros are inside…
Dan Boschen
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3
votes
2 answers
Minimum Output Samples needed to crack a "Gold Code" Generator (Dual LFSR)
Please preface your answer with spoiler notation by typing the following two characters first ">!"
Below is an implementation of a "Gold Code" Generator formed by adding (in $GF(2)$) the outputs from two linear feedback shift registers (LFSRs). This…
Dan Boschen
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2
votes
0 answers
How to demodulate DominoEx-like signal with liquid dsp?
I found a proprietary protocol that is used on ham radio bands. The author have published details,claiming that it's a version of DominoEX with slightly different baud rate and FEC.
I want to try to write a free demodulator for that mode beacuse i…
Albert DeVasques
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2
votes
3 answers
$9\rm V$ Battery with $45^\circ$ phase
How can you implement a $9\rm V$ battery with a phase of $45^\circ$? (As a black box with a DC Voltage of $9\rm V$ and a phase of $45^\circ$)
Please preface your answer with spoiler notation by typing the following two characters first ">!"
Dan Boschen
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