Passive Radar Sensor with IQ Signal

I am trying to model a passive radar model scenario (Multiple UAVs passively tracking ground-based radars) and I need waveform-level (or physics-based) modeling solution, such that I can return IQ signals at each UAV. I am using a radarTransceiver object for the ground-based radars for IQ by setting the sampling rate of the receiver object within radarTransceiver. However, it doesn’t appear as though I can use the radarTransceiver object on the UAVs because it doesn’t have a passive mode. (I tried to remove the transmitter or set the transmit power to 0 and it gives me an error). If I try to use a radarDataGenerator object in ESM mode and then use the receive function, it returns IQ but I can’t set the sampling rate (it always comes back as 1001 samples). I have even used the radarDataGenerator object in ESM mode as an input to radarTransceiver to return IQ but Matlab is still requiring a transmitter/transmit power, despite the ESM designation.

Is there any way for me to solve this issue in Matlab? I need a passive radar sensor that returns IQ signals with a designated sample rate for a signal processing application.

Answer 1

[Ayush Anand]

Hi Aaron,

I understand that you want to model a passive Radar Model scenario involving multiple UAVs and want to return the IQ signals at each UAV.

As correctly mentioned by you, the “radarTransceiver” object in MATLAB is designated to simulate only active Radar scenarios. However, for your scenario where you require only reception, you can use a combination of objects to obtain the IQ signals at each UAV like a passive model scenario. In this case, you can follow the steps below:

1.Use “phased.RadarTarget” to model the ground-based radars. This object allows you to specify the radar waveform, target properties, and simulate the received signals:

radar = phased.RadarTarget('OperatingFrequency', 10e9, ...)

2.Create a separate “phased.RadarTarget” object for each UAV. You can set the target properties for each UAV according to your requirements.

uav1 = phased.RadarTarget('OperatingFrequency', 10e9, ...);
uav2 = phased.RadarTarget('OperatingFrequency', 10e9, ...);

3.Use the “step” method of the “phased.RadarTarget” objects to simulate the received the IQ signals at each UAV.

iqSignalUAV1 = step(uav1, radar(x1, y1)); % x1, y1 represent the position of UAV1
iqSignalUAV2 = step(uav2, radar(x2, y2)); %x2, y2 represent the position of UAV2

Please know that you cannot use the “radarDataGenerator” object as it is primarily designed for synthetic data generation and does not provide the flexibility to set the sampling rate directly.

Please refer the following page for more information on “phased.RadarTarget” object and it’s use case scenarios:

https://in.mathworks.com/help/phased/ref/phased.radartarget-system-object.html

I hope this helps!

[Aaron]

Hello Ayush! Thanks for taking the time to respond to my question! After doing some research and work in Matlab, I found that using a phased.RadarTarget object wouldn't really work for my application. I couldn't figure out how to attach a waveform, etc. to it as you suggested and it is meant for reflecting signals given an RCS, polarization, etc., which is not my intention since I am entirely passive.

For now, I have constructed a scenario using individual Matlab objects. It appears to give me accurate results, although I am still confused by the output of a few objects, mainly the receiver.Preamp, which calls for an uncharacteristically high noise figure to see any significant noise. I'll keep exploring this application space but if you or anyone else has any suggestions, feel free to let me know. Thanks!