AWR1843AOP: Understanding HPF Behavior in AWR1843AOP for Ghost Object Mitigation

Tool/software:

Hi all,

We recently tested the AWR1843AOP board in an anechoic chamber and observed constant ghost objects at two ranges: one at 5 m and the other at 140 m.

We were using the MRR lab with a 120 m chirp configuration (ramp slope: 4 MHz/µs). Backtracking the frequency values corresponding to these distances using the formula IF=S⋅2d/c​, we found frequencies of approximately 133 kHz and 3.8 MHz.

I have a few questions:

1. Possible Sources of Noise:

   • What could be the potential sources of noise in the IF stage causing these ghost objects?

2. High-Pass Filters and Noise Passing Through:

   • While inspecting the code, I noticed that two HPFs (with corner frequencies of 175 kHz and 350 kHz) are enabled. Why might noise at 133 kHz have passed through these filters?

3. HPF Specifications from Datasheet:

   • The datasheet mentions:
     • "Less than ±0.5 dB pass-band ripple/droop"
     • "Better than 60 dB anti-aliasing attenuation for any frequency that can alias back into the pass-band."
       Could you explain these specifications in detail and how these HPFs function in the digital baseband chain?

Regards

Tanoop