Questions tagged [doppler]
The doppler tag has no usage guidance.
40
questions
2
votes
2answers
79 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:
...
0
votes
0answers
43 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 ...
0
votes
1answer
31 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 $\frac{1}{f_{Doppler}}$. ...
0
votes
0answers
14 views
Doopler spread and delay spread in an equation of channel freq response
Assumed the transmission system with channel impulse response is determined by the matrices $H(\tau_l) \in C^{N_R \times N_T}$ ( $N_R$ and $N_T$ are numbers of received and transmit antennas)
By ...
3
votes
1answer
65 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 ...
0
votes
0answers
26 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 ...
2
votes
1answer
73 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 ...
0
votes
1answer
69 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 ...
0
votes
1answer
19 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 ...
1
vote
4answers
40 views
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}...
0
votes
1answer
13 views
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 ...
0
votes
1answer
21 views
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 ...
0
votes
2answers
80 views
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 ...
3
votes
1answer
220 views
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 ...
3
votes
3answers
104 views
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 ...
-1
votes
1answer
103 views
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 ...
1
vote
2answers
171 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 ...
0
votes
0answers
131 views
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 ...
0
votes
1answer
172 views
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 ...
0
votes
0answers
23 views
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 \...
0
votes
2answers
159 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{...
2
votes
2answers
426 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 ...
0
votes
2answers
147 views
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.
0
votes
1answer
37 views
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?
0
votes
1answer
63 views
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 ...
0
votes
2answers
893 views
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.
...
1
vote
1answer
215 views
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(...
3
votes
1answer
90 views
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 ...
0
votes
1answer
173 views
Measuring Amplitude of sound wave FFT
Please, pardon my ignorance. This may be a simple question, but I am still unable to explain what is happening.
I am using a turtlebot to listen to sound emitted from a stationary sound source.
My ...
1
vote
0answers
60 views
Doppler Shift and Wireless Access Points
I am trying to design and implement a system that would calculate the velocity of a hand motion in smartwatch.
The general idea is to calculate the Doppler Shift of each access point and find ...
1
vote
1answer
320 views
Why do signal have mirror signal after pure frequency shift?
In my Matlab code I have a simple simulation of FPGA with the ability to simulate doppler shift, and after I and Q components plugged into IQmod with some carrier freq.
In my Matlab code when I ...
0
votes
1answer
956 views
Use of complex numbers to calculate Doppler effect?
First of all, I'm a beginner in this field, please tell me if any of what I'm asking is too basic / can be found with some google research.
I have a situation with a static TX and a moving RX (v is ...
1
vote
0answers
326 views
How to calculate the doppler shift?
I am writing a QPSK receiver in MATLAB. In the transmitter part, I have generated random data using randi, QPSK modulated and pulse shaped using a RRC filter.
The ...
1
vote
2answers
2k views
How to interpret an Ambiguity function
I need to evaluate several different waveforms regarding their doppler tolerance, for use in a radar application. So I came across something called the Ambiguity function.
The following picture shows ...
2
votes
0answers
216 views
Help detecting target in pulsed radar signal
This signal is from the Pasternack $2.4\textrm{ GHz}$ development kit. The saved signal appears to be the pulsed waveform. It is sampled at $20\textrm{ kHz}$ for $4130$ points. I recorded a ...
8
votes
2answers
1k views
Interpretation of Clarke's Doppler power spectral density
What I understand of Doppler spread is that the relative motion between Transmitter (TX) and Receiver (RX) change the exposing time of signal. In rapport to a constant-distance TX-RX, a moving toward ...
2
votes
1answer
874 views
Pulse Doppler Radar: how to filter its Range-Doppler matrix?
I want to simulate a Pulse Doppler Radar with medium pulse repetition frequency (PRF about $100\textrm{ kHz}$, about $500$ pulses in pulse train).
It's rather powerful, and should discriminate ...
0
votes
1answer
95 views
Correcting for Doppler shifts at the speed of sound for a 800 MHz signal
I'm working with a system which is planned to reach velocities of about 340m/s. It's likely that we'll be using a frequency around 800 MHz for rx and tx. At these speeds, supposing a fixed source, the ...
4
votes
3answers
992 views
Matched filter loss due to frequency offset
I'm working with a pulsed radar signal which uses linear chirp pulses. I perform pulse compression by applying a matched filter of the simulated chirp waveform and recording the location and power of ...
0
votes
1answer
549 views
Radar: FMCW or CW
I purchased a Doppler radar that can run in both CW and FMCW modes. I don't understand how to operate the radar in FMCW mode. I would like to understand what I need to do to get my radar to run in ...
