Implementation of a 18 GHz bandwidth channel emulator using an FIR filter

An implementation of a broadband channel emulator is presented using a Finite Impulse Response (FIR) filter which operates up to 18 GHz (HMC6545LP5E). This integrated circuit has two differential channels, each having 9 adjustable taps and a delay between taps of 18 ps. The individual tap behaviors do not match to that of an ideal FIR filter. The response for each tap is measured to create a 'basis function'. Using these basis functions a method is presented that matches the filter response to a desired response within the limits of the filter. Two methods are used to obtain a match between the desired channel response and the simulated response: least square method (LSM) and genetic algorithm (GA). The LSM uses mapping functions which map from the obtained tap coefficients to the IC tap coefficients for each tap while GA uses exact measured data of each individual tap to achieve the best tap coefficient for a given target channel. The calculated and measurement results of these methods are presented and compared for both methods.