I'm trying to design an equalizer for spectral flatness over a 100MHz signal for an LTE channel emulator. A channel emulator simply multiples channel coefficients with an external signal from a signal generator in baseband and converts it to RF frequency.
The following figure shows the frequency response of the system measured with single tones(0dB power) at 100 KHz intervals over 120 MHz range with a center frequency of 3.8 GHz, measured at the RF end of the channel emulator.
Our region of interest is the central 100 MHz which is shown in the following figure.
In the above case, the channel is bypassed i.e. the channel coefficients simply represents unit gain and no frequency/phase translation. The unevenness in the frequency response is due to gain roll-off in the D/A converter and other RF components in the channel emulator. My questions are as follows,
Say I design an N tap LMS equalizer and obtain the filter coefficients. How to apply the coefficients from frequency domain equalizer to the time domain signal?
Does the frequency response have to be measured at a finer granularity than 100 KHz for constructing an equalizer with a smooth frequency response?