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ADF5901 and ADF4159 Design FMCW Radar with High-Frequency Signal on Vt

Category: Hardware
Product Number: ADF5901

In the design of the FMCW radar using ADF5901 and ADF4159, a high-frequency signal at 300 kHz is observed on Vt. This phenomenon was present in previous designs as well. Upon inspection, it was found that only pins 14 (AVDD, RF_AHI) of ADF5901 were missing filter capacitors. However, even with these capacitors removed from the previously functional radar board, it continued to operate normally. Therefore, I would like to inquire about the cause of this issue. Is it related to the filter capacitors? The loop filtering and configuration codes have been verified for feasibility in previous designs, and there are no differences in these aspects.Vt

  • Hi BayMax,

    It seems like the loop filter is unstable. Is there a component or layout change between previous designs? 

    What is the Vtune behavior when ADF4159 and ADF5901 are configured as a single-tone rather than a ramp generation? 

    Can you send the register configurations for ADF4159 and ADISimCLK file for ramp and loop filter simulations? 

    You can post it here or send a direct message after adding me as a friend. 



  • Thank you very much. As you mentioned, during the inspection, it was found that an incorrect capacitance value selection for one of the loop filters caused instability. Now, it is working properly. I really appreciate your response!