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Stingray loopback capability?

Category: Hardware
Product Number: ADAR1000EVAL1Z

We're getting the Stingray (part finally on order) and I'm investigating how to maintain calibration both transmit (single analog beamform) and receive (hybrid beamform to create 4-quadrant monopulse). One idea is to inject a calibration signal using a transmit path and then measuring it on the receive path(s). Is there any path with the combo XUD1A/ADAR1000EVAL1Z that allows a low-power loopback? If not, we'll have to assume a static (measured in the antenna chamber) calibration for the U/D converter and the beamformer, and just calibrate the multichannel transceiver using a separate set of cables/couplers.

miscellaneous changes
[edited by: stetz at 8:36 PM (GMT -4) on 11 Aug 2022]
  • Hello,

    There is not a path that allows for a low-power loopback. There are no internal paths to do this kind of calibration.

    You could use external equipment to inject your calibration signal from 1 subarray into the other 3 subarrays. You could also use 2 subarrays in transmit and 2 in receive and inject your calibration signal and then reverse the directionality, and the 2 former transmit subarrays are made to be receive subarrays and 2 former receive subarrays are made to be transmit subarrays.

    One suggestion would be to use the detector channel on the stingray platform to measure the interference pattern of 2 channels at a time using cables and a 2:1 combiner, 1 changing in phase while the other is constant in phase. Another suggestion would be to start off using a CW tone split by 32, going into stingray to calibrate 3 channels at a time using the 4 ADCs (keeping one channel constant). This same method could be repeated on transmit using a spectrum analyzer in IQ demodulator mode and the DMA buffer on the AD9081 MxFE to "split up" each channel in the buffer in time or using the NCOs on the AD9081 to "split up" DAC channel in frequency.

    This paper can be used as a reference, see the calibration section under measured data: