We designed a AD9364 based board and could successfully test it in Manual gain control mode i.e., rx_gc_mode = 0. The following are the design parameters.
center frequency = 4 GHz
Bandwidth = 26 MHz
sampling rate = 30.72 MHz
Mode of Operation = FDD
Frame size = 5 ms
Though it is a continuous link, we perform receiver tuning and channel estimations only on the preamble portion i.e. at the start of every 5 ms. Change in gain value within the 5 ms (after preamble) period lead to a scaling (x2, x0.5 etc) which is different from the scaling seen at preamble. This results in wrong decoding, since the demodulation threshold are fixed w.r.t the modulation (QAM ).
When slow attack agc mode is enabled, less frequent symbol errors are observed even with a constant power at the receiver input. But in fast attack mode errors are very frequent. Please suggest us the appropriate mode and corresponding parameters for the described case.
Thank in advance,