Hi, I am currently using the ADF5901, ADF5904, ADF4159, and ADRF5300 to design a 4T8R MIMO radar system. Previously, I successfully verified the feasibility of a 2T4R system without using the ADRF5300. In this design, I utilized a Wilkinson power splitter to distribute the LO signal to two ADF5904 chips for achieving 8RX. Two ADRF5300 switches allow one ADF5901 to control four channels in a time-division manner.
During the design and testing phase, I found that the quality of the IF signals for all channels was acceptable; however, there were issues with angle-of-arrival estimation. After extensive validation, I suspect that the four signals generated by the ADF5901 may be problematic. Theoretically, for a 4T8R array, the phase trends of the 8-channel data obtained from each TX transmission should be consistent. However, testing revealed significant issues with this consistency. It’s not that a specific TX channel is unstable; rather, the phase trends from different TXs exhibit variations across different data collection sessions.
I would like to inquire about the potential causes of this issue. Below are the phase results from three signal acquisitions, where 1 to 8 represent the 8 RX channels, and different curves indicate the phase changes of the received signals corresponding to different TX transmissions. In the embedded control system, both RX and LO are continuously active. TX is controlled through register 0 of the ADF5901, switching channels 1 and 2, while each channel is managed by the ADRF5300 for switching to form four transmit paths, with a channel switch occurring every ten chirps. This part of the embedded control is illustrated in the diagram. The STM32 is used for control, and the history represents the ramp output from the technical ADF4159's MUXOUT. The high and low levels of PA11 and PA10 are used to control the two ADRF5300 switches.
I would appreciate your assistance in understanding why different TXs produce varying phase trends. Thank you!
