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# Questions tagged [doppler]

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### Why is my target showing up with a non-zero centered velocity? I captured this data using the IWR6843A0P using a stationary corner reflector

I need help understanding what I should do to determine why my target is showing up in my Range doppler map with a non-zero centered velocity when I captured my measurement using a stationary corner ...
49 views

### Doppler radar. Signal to noise ratio

I'm trying to figure out how a continuous wave Doppler radar works. When moving towards the radar, the Doppler frequency should increase, and when moving away from the radar, the frequency should ...
• 95
131 views

I am developing a continuous wave Doppler radar to detect human movement at a speed of 0.2-6m/s. For a radiation frequency of 24.15 GHz, the Doppler shift during longitudinal motion will be equal to ~...
• 95
16 views

### Comparison channel impulse in DD and TF domains

How can I plot a similar comparison plot in Matlab? My attempt I have tried to create a random function like/ Matlab: rand(M, N) and then take SFFT of it ...
• 23
109 views

### Why are polyphase codes doppler tolerant in comparison to bi-phase codes?

What is the logical reason behind this? Why are P1,P2, P3, P4 codes unaffected by doppler shifts?
1 vote
270 views

### doppler tolerant phase coded waveforms

how do i conclude a waveform shows doppler tolerance, say polyphase code-frank code, without the use of ambiguity diagram? we know that it is doppler tolerant and if we check the frequency spectrum of ...
84 views

### Range Doppler Graph

The graph includes a peak at zero frequency and some other frequencies. However, my professor says that there should not be a peak at zero. I contend that he is wrong. But my graph is also not right, ...
• 11
50 views

### Can't get velocity right in the range-doppler map of a received signal from 1 target

I have written a code that simulates a target at 400 m and velocity of 100 m/s. I calculated tau_t the time delay due the the range and the velocity, then I created a received signal from the ...
• 1
29 views

### Incorrect velocity in range doppler map

I am trying to simulate tx, rx and if signals and from the if signal, compute the range and doppler of the target. In the function below, when i generate the range doppler heatmap, i am getting range ...
• 1
908 views

### unambiguous velocity $V_\max$ in radar doppler processing

In literature, $V_\max = \lambda\cdot \operatorname{PRF} / 2$; should it be $V_\max = \lambda \cdot \operatorname{PRF} / 4$, which would be consistent with FMCW $V_\max = \lambda / (4 \cdot T_c)$? ...
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164 views

221 views

### How does slow-time FFT detect velocity?

The signal processing steps for a pulsed radar are: Fast time matched filter -> Slow time FFT. I cannot understand how is the second step able to detect frequency, because the results after the ...
1 vote
372 views

### Doppler Map for a beginner pulsed radar

I have been assigned to simulate a Pulsed radar with Chirps hitting a moving target and then analyzing the data to create a Doppler-Range map. Im having trouble completing some of the "algorithm'...
1 vote
233 views

### FMCW radar IQ data constellation

I am trying to replicate the basic method of vital signal detection based on FMCW radars I found in classical literature on the subject. The issue I am facing at the moment is that of IQ data DC ...
1 vote
375 views

### range-doppler map of FMCW radar

I have created a 2D matrix with L as the number of samples and K as the number of chirps. Now I am trying to plot the Range-Doppler response which doesn't correspond to the correct range and velocity ...
1 vote
582 views

### How to estimate Range, Doppler and Angle with FMCW MIMO Radar?

I am trying to obtain the range, Doppler and angle of arrival estimation with an TDM MIMO FMCW radar. Actually, I have completed this process. In doing so, however, a few things remained unclear. ...
1 vote
920 views

### FMCW Radar Doppler Ambiguity related to Nyquist theorem or exceeding the distance frequency or both

I have been reading about doppler ambiguity and I have two explanations for its occurrence that I can't relate to each other. 1st Explanation: In the stationary case (radar and target are stationary) ...
• 125
1 vote
695 views

### Doppler shift in satellite communication systems

Does someone have a table with doppler shift range for satellite communication systems? Is it S band or X band? I have seen somewhere, but I can't find it.
• 377
239 views

### Derivation of Clarke's Doppler power spectral density

I am reading Wireless Communications by Andrea Goldsmith. I have some issues in the derivation of Clarke's Doppler power spectral density given there. 1)For beginning the autocorrelation of the in ...
1 vote
5k views

### range-doppler map to range-velocity map conversion

UPDATE 2.0 I think I've managed to produce the correct range-velocity map. I'm struggling with analytically calculating the range which I expect to see on the range-velocity map. Could someone please ...
• 113
43 views

### What does Doppler Fast/Slow Items? How do they relate to Micro-Doppler Signature?

I'm working with X4M200 respiration sensor (Sensor Output Datatypes) and in provided link on page 11 it says that it provides recordings with Movement Slow/Fast Items (slow and fast pulsedoppler ...
1k views

### Doppler shift in signals

I have started doing some reading into the effects of the doppler shift on signals. In particular, radar signals from ships moving relative to a receiver. This might seem weird but I understand why ...
1 vote
1k views

### Range-Doppler Matrix Cells

I am working on developing an understanding on range-gates and the size of each cell. I haven't had much luck in finding information in how the matrix in the image below is generated, so I have some ...
1 vote
348 views

### Motion detection with FMCW radar

I am studying the work of a microwave rangefinder and faced such a problem, but before that, a preface: I have a microwave module that operates at 24GHz. I use a 1kHz triangle waveform as the ...
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108 views

### Generating a 2D delay-Doppler channel matrix

I was wondering if anyone here has any idea on 2D delay-Doppler channel and how to generate the channel matrix? Even a hint or a resource would be helpful. I just want to understand and visualize the ...
131 views

### Fine frequency correction : grouping and finding max amplitude inside a group

I work on phase and frequency estimation algorithm. Currently I am working on a derivation and determination of the Doppler shift( dF – frequency step). For each dF, The following algorithm was ...
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110 views

### How does one go about choosing a Radar Cross Section for a human when modelling a Pulse micro-Doppler microwave radar?

So as part of a personal project I'm in the process of simulating and making a fall detector using a 2.7GHz microwave sensor with a range of 8m. I've been using MATLAB's example code to simulate each ...
156 views

### Beginner Educational Resources

New member here. Recently got hired into a mid level EE position. Have a BSEE but performed more radar performance analysis at a higher system level previously. In my new group we're doing a lot of ...
1 vote
565 views

### Can velocity be calculated in first stage FFT?

I understand that, For an FMCW radar, the velocity of a target is proportional to the phase changes at same time instants across the chirps. I have a MxN data cube with N chirps(columns) & M ...
• 43
60 views

### How is sampling rate affect the Doppler spectrum? Textbook attached

I am studying FWGN model, in the textbook "MIMO-OFDM wireless communication with MATLAB", it says "When oversampled by a factor of $N_OS$, the bandwidth of Doppler spectrum becomes \...
69 views

### Correcting large frequency offsets at very low data rates

Consider a typical BPSK system running at a baud rate of 1 kbaud/sec - the receiver needs to deal with severe frequency offsets, let's say up to +/- 1 MHz offset and that the frequency offset can ...
• 723
1 vote
779 views

### What is the importance of signal bandwidth in radar systems for velocity and localization estimation

So I know about the basics of doppler shift which relates the velocity of a moving object with the frequency carrier shift seen at the reciever. But, I don't understand the importance of the ...
• 267
184 views

### How to remove frequency offset with RRC as pulse shaping filter

I am working on a project with QPSK modulation format and a RRC filtering at the transmitter (TX) side. The channel introduces a constant dropper shift ($f_d$) to the received signal. To make the ...
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84 views

### How to add a frequency offset to a buffer of MPSK signal for simulation purposes?

I need to simulate some channel effect to a buffer of MPSK signal. How to add a frequency offset to a buffer of baseband MPSK signal?
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1 vote
379 views

### How to remove the modulation before doing frequency offset estimation?

To use DFT/FFT (or maximum likelihood) method to estimate the frequency offset introduced by the channel, we need to remove the modulation on the received data samples in the front. If the unknown ...
• 49
700 views

### Why is fourier analysis used in doppler effect?

I am a high school student that carried out the experiment on the Doppler effect to therefore analyze the graph but after doing some research, I saw one of the articles saying “ Fourier analysis is a ...
524 views

### Radar for Vital Signs – Matlab Simulation

Interested to design and simulate FMCW radar for Vital Signs sensing. The initial signal parameters are(1): When using the following Matlab code to generate the waveform: ...
• 113
110 views

### Sound of (sea) waves imitation

I need to create an algorithm for sound of waves. So I imagine it should be a white noise with doppler effect. However I understand doppler is just change of frequency. But white noise have all the ...
• 101
1 vote
926 views

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

In the literature I've read that fast fading happens if the bit duration is larger than the coherence time of the channel. The coherence time of a channel is proportional to $\frac{1}{f_{Doppler}}$. ...
• 11
705 views

### MTI RADAR, DSP algorithm question

Im new to RADAR signal processing. I using this doc for ref: https://www.mathworks.com/help/phased/examples/ground-clutter-mitigation-with-moving-target-indication-mti-radar.html I trying to rebuild ...
137 views

### frequency domain representation of the doppler shift sequence

This is a bit of a weird question. I have a bunch of IQ data. Its a very big file that i cant upload on here. Im working through a few exercises trying to analyse the data. I have plotted the signal ...
655 views

### Does Radio Communication Have to Account for the Doppler Effect?

I know that radio communications take place in specific frequency bands, and that the doppler effect can cause shifts in frequency when there is relative motion between the source and destination ...
355 views

### Cant find Doppler shift with LFM signal

Im stuck on this one. I hope someone helps me! Problem: I need to find Dopler shift with array of reflected chirps. I have bursts of chirps which then i sampled, and calculated fft. Im suposed to ...
52 views

### A-GPS frequency (fd) search ranges

A-GPS is able to reduce the fd search range from several kHz (GPS search range) to several hundred Hz (a-GPS search range). I know the GPS search range has a center at 0 Hz. What is the center ...
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1 vote