We are developing a GPR radar using the SFCW thecnic.
We want to use both channels operating in MIMO mode, connecting TX1 and RX1 to antennas to transmit and receive a signal, and connect TX2 to RX2 directly. The second connection is usefull to discover the phase difference between the emitter and the receiver. Knowing the phase difference between the channels we can calculate the phase difference introduced by reflection caused by the object we want to detect with the radar.
We have tested the MIMO mode and we are getting a significative phase difference between the results in RX1 and RX2.
It was expected a slight phase difference but the difference sometimes reaches almost 90º.
Is there any way to configure both channels to work properly for our needs that we are not seeing?
Another aspect you might consider exploring is the possibility of software-based phase correction techniques. Some software-defined radio (SDR) platforms offer features or plugins for phase alignment and compensation. By analyzing the phase differences between the received signals on RX1 and RX2, you could potentially develop algorithms or utilize existing tools to dynamically adjust the phase of one channel to match the other. This approach could help achieve better synchronization and alignment between the channels, thereby improving the accuracy of your GPR radar system. Additionally, consulting with experts in signal processing or radar engineering may provide further insights and innovative solutions tailored to your specific requirements.
Since the Receivers have the same local Oscillator and the Transmissor have the same local Oscillator too, why when i connect the Tx1 channel to the Rx1 channel and the Tx2 channel to the Rx2 channel, im getting different phase values in Rx1 and Rx2, using MIMO configuration?
Conduct a calibration fnf procedure by connecting TX1 to RX1 and TX2 to RX2 and measuring the phase difference. Use this measurement to compensate for any inherent phase differences. Double-check the MIMO synchronization settings in the bladeRF software. Ensure that the device is configured correctly for synchronized operation.
DSPavia wrote: ↑Mon May 20, 2024 8:37 am
Since the Receivers have the same local Oscillator and the Transmissor have the same local Oscillator too, why when i connect the Tx1 channel to the Rx1 channel and the Tx2 channel to the Rx2 channel, im getting different phase values in Rx1 and Rx2, using MIMO configuration?
Best regards!!
DS
I run into the same issue. In my setting, the Tx1 is connected with Rx1 using a 30cm cable plus a -20db attenuator, and then Tx2 with Rx2 using the same length cable plus a -20db attenuator. I then divide the samples received from Rx1 with the samples received from Rx2 to extract the phase difference. As the two cables are in the same length so the phase difference should be close to zero, but what I get is much larger than that. Interesting thing is that the phase difference, even not zero, but is fixed.
I then run another experiments, the cable connecting Tx2 and Rx2 are changed from 30cm to 60cm so I'm supposed to have none zero phase difference between the two paths. I then increase the central frequency by the step of 20Mhz. I was suppose to observe that the phase difference also increase the same amount every time I increase the frequency. Unfortunately it is not the case.
Have you solved the issue, and may I know how did you solved it?
