Hi ADI Team,
We are debugging a custom AD9364 hardware platform and would like guidance on why our custom board behaves differently from the EVM despite using the same intended configuration.
We are comparing two AD9364-based platforms: (1) an ADRV9364-Z7020 EVM using the Zynq PS-based ADI reference API, where the HDL QPSK design output works correctly, and (2) a custom AD9364 board using a MicroBlaze-based API ported from the KC705/reference design, where the same HDL QPSK design shows distortion in the TX spectrum.
Both boards have been matched for reference clock frequency, nominal API initialization, LO settings, and sample rate. Digital loopback checks and FPGA waveform generation appear correct on both platforms.
We can observe some differences in the output spectrum for the EVM board to Custom board
After full register comparison, multiple calibration-related registers differ between EVM and the custom board, including:
TX Quadrature / IQ Correction:
- 0x08F (QUAD gain correction)
- 0x092 (TX I offset)
- 0x093 (TX Q offset)
- 0x0A7 (TX Quad Cal Status)
RX/TX Calibration:
- 0x170 / 0x171 (Rx Phase/Gain Correction)
- 0x174–0x17F (RX IQ DC offsets)
- 0x19B–0x19D (RX BB DC IQ Offset)
Calibration / Filter:
- 0x140 / 0x141 (Calibration Table)
- 0x0C7–0x0C9 (TX BBF)
- 0x1E8–0x1EC (RX BBF)
- Whether the observed difference between the EVM and custom board indicates what kind of issue, either in PCB layout or signal integrity issue, power supply noise or grounding problem, clock quality or jitter issue, TX output path overload or gain mismatch, RF matching differences, or calibration convergence differences caused by board-level electrical behavior? Below, we are adding the image of the spectrum output. Sampling rate is 7.68MHz on both cards.
- BW = Rs * (1 + 0.5) = 2.88MHz
- Rs = Fs/4
- EVM Board results
- Custom Board Results
- Condition 1: We have 2 EVM boards, one as QPSK TX and another one as QPSK RX. It's working fine, we can successfully demodulate the bits which we where transmited.
- Condition 2: one EVM board as RX and your custom board as QPSK TX, we cant able to demodulate the data correctly. We suspect there is a spectral difference in EVM vs custome board. what will be the issue could be either in hardware or API configuration. We checked both BIST loopback and digital loopback, and also corrected the data and clock delay settings on the custom board. Since the issue still persists, this suggests the problem may be occurring after RF upconversion, likely in the RF hardware path.
