Hello! I am looking to get some help explaining some unusual behavior we have been seeing with the CC1110. We have it running in a custom PCB built on the TI 433 MHz HW example. We have been evaluating its sensitivity in the presence of a frequency offset, and we have been finding that for for negative offsets between the receiver and the transmitter (ftx<frx) the sensitivity is unchanged within the expected limit of the compensation algorithm (BWrx/2). However, for positive offsets between the receiver and the transmitter (ftx>frx) the sensitivity is significantly degraded, in an increasing manner as the offset increases. The only way we found to resolve this is to increase the preamble length to >4 bytes. However, I would expect the behavior to be symmetric - it should work for positive and negative offsets as well, right? We are using SmartRF 7 with the attached configurations to run the test. We keep the receiver frequency constant and change the transmit frequecny manually for each run, as shown in the table below. Can you offer any insights into why this may be happening?
TX Frequency (MHz) | RX Frequency (MHz) | RX to TX df (kHz) | Outcome |
437.059631 | 437.059631 | 0 | Pass |
437.049744 | 437.059631 | -9.887 | Pass |
437.069916 | 437.059631 | 10.285 | Pass |
437.069916 | 437.059631 | 10.285 | Pass |
437.0448 | 437.059631 | -14.831 | Pass |
437.07486 | 437.059631 | 15.229 | Fail |
437.039856 | 437.059631 | -19.775 | Pass |
437.079803 | 437.059631 | 20.172 | Fail |
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