Questions tagged [doppler]

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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) ...
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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.
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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 ...
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3 answers
383 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 ...
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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 ...
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3 answers
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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 ...
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Unexpected spectrum in 2D FFT

In preparation to construct a Delay-Doppler (or Range-Doppler) map, I sample a signal using a micro controller-based DAQ system. The test signal is sourced from a signal generator, I and Q are ...
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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 ...
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Range-Azimuth Heat map (FFT)

I have a question regarding performing a 2D complex FFT on a 2D array of frequency information in one dimension and azimuthal change in degrees in the other dimension. That is, I ran a test with an ...
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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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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 ...
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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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1 answer
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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 ...
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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 ...
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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 ...
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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 \...
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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 ...
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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 ...
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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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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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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 ...
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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 ...
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2 votes
2 answers
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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: ...
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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 ...
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1 vote
1 answer
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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 $\frac{1}{f_{Doppler}}$. ...
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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 ...
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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 ...
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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 ...
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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 ...
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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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Doppler frequency when down-converting a receiving signal

Suppose we have a monostatic radar system, with only one target crossing at a speed $v$ at the main lobe of the antenna. The Doppler frequency for this case will be given by $ f_d = \frac{2v}{\lambda}...
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Converting PLL Discriminator into Doppler error

I'm writing a GPS receiver SDR software, and I have calculated the PLL discriminator ouptut as atan(Q_Prompt,I_Prompt) I would like to know the formula that converts the discrminator output to doppler ...
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Is it possible to detect or localize movement of objects using LPWA (or LPWAN) such as LoRa, DASH7, NB-FI?

Assume that there is a moving human in the room without any device (or receiver). Is it possible to detect or localize movement of objects using LPWA (or LPWAN) such as LoRa, DASH7, NB-FI by analyzing ...
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2 answers
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help to calculate phase shift in certain frequency(identified from FFT)

I am designing a 24ghz doppler radar, with 1TX 2RX. Four adc channel are recording at 25khz, applying 256point FFT on adc of both of RX I and Q, I could identify the target in certain doppler ...
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5 votes
1 answer
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Radar signal processing flow chart

I'm new to Radar in general, and I'm studying RADAR using online resources. I came across the following slide which shows the process flow of the Radar signal processing. The thing I don't get in ...
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3 votes
3 answers
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How to use a FIR on a signal with a drifting central frequency?

I have been working on this subject for a while and I couldn't get a proper answer. I am trying to estimate the phase of the input signal : $x(t)=Ae^{j(at^2+bt+c)}+n(t)+i(t)$ Where $n(t)$ is a ...
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Doppler effect in underwater acoustic channel

I got my BER vs SNR graph as shown. I was trying to show the difference in BER with OFDM signal transmission under Doppler effect and without Doppler effect. However, based on my understanding, the ...
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1 vote
2 answers
354 views

Doppler Shift and the Pulse Repetition Interval

Suppose that I have a signal $x(t)$ consisting of $N$ pulses at a given frequency $\omega_{c}$. I space them $T$ seconds apart, ie the Pulse Repetition Interval (PRI) for the waveform is $T$. Now ...
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Range Doppler Maps

I would like to understand from a high point of view how these maps are computed. On the y-axis we have m/s and in the x-axis the range. I read something about the Fourier transform etc, but I don't ...
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Question about FMCW range-velocity plot

I am working on plotting range-velocity heatmap of the receiving FMCW signal. I actually have already plotted. However, I do not really understand the mapping relationship between Doppler FFT bin and ...
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DOA estimation of moving, radiating source in the near-field with nonuniform Doppler shifting

I am trying to estimate the DOA of a radiating source using two passive sensors. In the case of a stationary source, I find the lag $k$ of the maximum in the sample cross-covariance sequence $E \...
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3 answers
259 views

Frequency Domain Correction of Frequency Offset or Doppler Frequency in LTE

We are working on LTE Uplink CFO Correction for 3 MHz band. The time domain CFO correction is easy, which depends on the processing of 3840 samples step by step multiply by $\exp(-j 2\pi f_\text{...
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2 votes
3 answers
851 views

Doppler Shifting A Chirp Signal

So I have a digital linear chirp signal: $$ x[n] = \sqrt{\frac{2}{N}} \cdot \cos\Big( 2 \pi \frac{f_{0}}{f_{s}}n + \pi \frac{B}{N} n^{2}\Big) $$ Where $f_{0}$ is the initial frequency, $f_{s}$ is ...
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Why having a ridge like Ambiguity Function implies lack of Doppler resolution?

I was wondering why if the AF (Ambiguity Function) has a ridge like form it has low Doppler resolution.
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Degrees rotation based on frequency offset?

What is the relationship to calculate degrees of rotation in the constellation given a baud rate and frequency offset?
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How to classify the movement type of a target into two categories(direct motion or else) by using a doppler radar?

How to classify the movement type of a target just into two categories(one is direct motion which is almost straight line movement and the other is anything else) by using a doppler radar with a ...
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In case of using a Doppler radar, do we have to use IQ demodulation to find the direction of a target?

I want to know the way to find the velocity of a target by using a doppler radar. I read some paper about it, In summary, send rf signal to a target receive the reflected signal from the target. ...
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1 vote
1 answer
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Doppler Shift of Phase Coded Pulse Compression Waveform

Suppose I want to transmit the signal: $$ x(t) = g\Big(\frac{t-t_{0}}{T}\Big) \cdot \cos(2 \pi f_{0} t + \theta_{0}) + g\Big(\frac{t-t_{1}}{T}\Big) \cdot \cos(2 \pi f_{1}t + \theta_{1}) $$ Where $g(...
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FMCW Radar Signal Processing Flowchart / Ambiguity Function

I Read many papers on signal processing for pulsed and FMCW radars, taking the FMCW type, the signal processing start after mixing the received and transmitted signal, the result of this operation is ...
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How to undo dynamic Doppler effect by software?

I have a signal affected by Doppler effect. In general, the Doppler effect changes the scale of the time and frequency domains. So, to undo this phenomenon, I am using a sampling rate converter. Two ...
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