Skip to main content
OverflowAI is here! AI power for your Stack Overflow for Teams knowledge community. Learn more
6 votes
Accepted

Interpretation of Clarke's Doppler power spectral density

A simple, "non-technical" way of thinking of it is the fact that the Doppler frequency is proportional to $\cos\theta$. The amplitudes of cosine, however, are not uniformly distributed, but are ...
Robert L.'s user avatar
  • 2,222
5 votes

Radar signal processing flow chart

Part of your misunderstanding comes from the fact that there are many ways in which the radar signal processing chain is implemented. Depending on the type of radar, targets of interest, hardware, etc....
Envidia's user avatar
  • 2,546
5 votes

Interpretation of Clarke's Doppler power spectral density

In addition to Carlos answer, I want to correct your general understanding: What I understand of Doppler spread is that the relative motion between Transmitter (TX) and Receiver (RX) change the ...
Maximilian Matthé's user avatar
5 votes
Accepted

How to remove the modulation before doing frequency offset estimation?

For lower-cardinality PSKs like the QPSK, the "classical" way is to take the signal to the $M$th power, $M$ being the number of constellation points. From the shape of an $M$-PSK modulation, ...
Marcus Müller's user avatar
4 votes
Accepted

In case of using a Doppler radar, do we have to use IQ demodulation to find the direction of a target?

Radar designer here: It sounds like you’re talking about pulse-Doppler (PD) radar systems. For PD radars, the process is essentially as you described: Generate a waveform (typically at IF) and then ...
vintagevogue's user avatar
4 votes
Accepted

Use of complex numbers to calculate Doppler effect?

Bottom Line First What you suggest will only work if your signal is at baseband and not at a carrier, which is usually the best way to do any simulation work regardless. If your signal is not at ...
Dan Boschen's user avatar
  • 51.9k
4 votes
Accepted

Matched filter loss due to frequency offset

Short answer; I'll try to come back and improve this later. Recall that a matched filter is equivalent to a sliding correlator. At each time instant, the sliding correlator multiplies the last $T$ (...
Jason R's user avatar
  • 24.6k
4 votes
Accepted

Doppler shift in satellite communication systems

I would recommend playing around with one of the predict libraries e.g. https://github.com/nsat/pypredict You can go find a TLE of a satellite you're interested in from a public database, and enter ...
user67081's user avatar
  • 723
4 votes
Accepted

Doppler Map for a beginner pulsed radar

When correlating the signals using xcor(code below) the output signal is greater then the Matrix column size. What portion of that information is needed? This is because the default parameters of <...
Envidia's user avatar
  • 2,546
3 votes

How to interpret an Ambiguity function

The ambiguity function is used in radar systems to get the distance and the relative speed of a moving object with respect to the transmitter. Is called ambiguity because it also tells about the ...
danipascual's user avatar
3 votes

Pulse Doppler Radar: how to filter its Range-Doppler matrix?

Two suggestions that may independently, or combined, help to solve your problem. Consider using a different window/weighting function for your FFT processing. There are window functions with low ...
GrapefruitIsAwesome's user avatar
3 votes
Accepted

Does Radio Communication Have to Account for the Doppler Effect?

Does radio communication have to account for the doppler effect? Yes. Would be pretty terrible if that wasn't the case: RADAR wouldn't work! Do moving objects such as planes and rockets have to ...
Marcus Müller's user avatar
3 votes

range-doppler map to range-velocity map conversion

First some background. In radar the relationship between range rate, $v$ and Doppler frequency offset, $\Delta f$ is given by: $$v = -\frac{c}{2} \frac{\Delta f}{f_c}$$ where $c$ is the speed of light ...
GrapefruitIsAwesome's user avatar
2 votes
Accepted

Correcting for Doppler shifts at the speed of sound for a 800 MHz signal

frequency shift of about 890 kHz (supposing my math is correct) $$\begin{align} \Delta f_\text{Doppler} &= f_0 \frac vc\\ &=800\cdot 10^6\,\text{Hz}\frac{3.4\cdot10^2\frac{\text m}{\text s}}{...
Marcus Müller's user avatar
2 votes

Doppler Shift of Phase Coded Pulse Compression Waveform

So this is something we run into with the radar community on a pretty regular basis. For LFMs, the solution is a bit trivial, but for coded waveforms it becomes a real issue. For us radar folk, we'...
vintagevogue's user avatar
2 votes

FMCW Radar Signal Processing Flowchart / Ambiguity Function

The Ambiguity Function is just a name for 2D Correlator. It is known that given a shifted 1D Signal the optimal estimator for the shift (Range in RADAR / LIDAR, etc...) it the correlation with the ...
Royi's user avatar
  • 19.7k
2 votes

How to interpret an Ambiguity function

I refer to the graph you presented at your original post. The interpretation of the graph is as follows: the wider the yellow part of the graph, the more immune to Doppler your system is. Normally it ...
luciano kruk's user avatar
2 votes

How to use a FIR on a signal with a drifting central frequency?

This is what I would try: Ignore the $n(t)$ and $i(t)$ since you know nothing about them. I am assuming that $x$ is complex and the rest of the variables are all real. Take the complex natural log ...
Cedron Dawg's user avatar
  • 7,560
2 votes

How to use a FIR on a signal with a drifting central frequency?

Without understanding more detailed results on what i(t) is, one solution is to estimate either the phase or frequency first, and then pass that result through a filter. An approach to do the ...
Dan Boschen's user avatar
  • 51.9k
2 votes

Doppler Shift and the Pulse Repetition Interval

Actually the PRI also changes. There is a complete explanation about this topic in "Cobbold - Foundations of Biomedical Ultrasound" chapter 10 (Pulsed Methods for Flow Velocity Estimation and Imaging)....
Mohammad M's user avatar
  • 1,327
2 votes

Doppler frequency when down-converting a receiving signal

When there is relative motion between the transmitter and receiver the frequency seen by the receiver is not $F_c$, so let's say you incur a Doppler shift of $\Delta_f$, then the shifted signal ...
Dsp guy sam's user avatar
  • 2,620
2 votes

Doppler frequency when down-converting a receiving signal

The simple answer is down-conversion is just a frequency translation. Consider the downcoversion explained by the cosine product rule: $$\cos(\alpha)\cos(\beta) = \frac{1}{2}\cos(\alpha+\beta) + \...
Dan Boschen's user avatar
  • 51.9k
2 votes
Accepted

MTI RADAR, DSP algorithm question

The second way is how it is done. In the fast-time (or range-bin dimension) you are right to perform the matched filter. However, Doppler information is gathered from sampling pulse-to-pulse. The MTI ...
Envidia's user avatar
  • 2,546
2 votes

Fast/Slow Fading: How are doppler shift and coherence time related?

Here's an intuitive explanation. Imagine a communication system (wireless) in a static environment (maybe picture the inside of a closed warehouse). There will be an amount of fading, but it is static:...
MBaz's user avatar
  • 15.3k
2 votes

Doppler shift in signals

It is well-known that Doppler effect shifts the received frequencies compared with the emitting frequencies. On the other hand, the time period of the sound signal is often ignored. Say a sound source ...
ZR Han's user avatar
  • 3,248
2 votes
Accepted

range-doppler map to range-velocity map conversion

In a range-Doppler map (RDM), you actually have two sample rates that define the two dimensions of the matrix: Fast-time dimension. This is usually established by the ADC to sample the pulse return. ...
Envidia's user avatar
  • 2,546
2 votes
Accepted

unambiguous velocity $V_\max$ in radar doppler processing

Both are actually correct, but it depends on what Doppler $f_D$ frequencies we want to observe. If we only want to observe positive Doppler frequencies, that is, targets with closing (approaching) ...
Envidia's user avatar
  • 2,546
2 votes
Accepted

doppler tolerant phase coded waveforms

You should really read this paper, Phase Coded Waveforms for Radar, on doppler tolerance and phase coded waveforms. I'll summarize section 5 on doppler intolerance for phase coded waveforms. PC ...
Baddioes's user avatar
  • 1,030
2 votes

doppler tolerant phase coded waveforms

The ambiguity diagram is used to analyze the result of pulse compression when receiving a Doppler-shifted version of the original waveform. I am not sure why you want to avoid the ambiguity diagram ...
Envidia's user avatar
  • 2,546
2 votes

Continuous wave Doppler radar

It's a little confusing what you mean by "longitudinal" and "transversely" in this context. You stated that In transverse motion, the Doppler shift will depend on the angle at ...
Envidia's user avatar
  • 2,546

Only top scored, non community-wiki answers of a minimum length are eligible