I'm designing a digital QPSK transmitter & receiver.
At the transmitter, i'm using xilinx spartan3smb1500 to generate the QPSK samples. A DAC follows to give me a 1Vpp 1MHz signal. To transmit on my 2.4GHz antenna, i've used an rf upconverter board.
At the receiver, the 2.4GHz antenna receives my signal and downconverts to 1Vpp 1MHz signal. An ADC samples at 50Msps, converts to 12-bit digital signal.
This 12-bit input is splitted in two channels : one is fed to multiplier on channel I & another to multiplier channel Q. The other input of multiplier is a fixed NCO running at
1MHz sine for I-channel and 1MHz cosine for Q-channel. The output of the multiplier is fed to an FIR Filter to filter out the high frequency component and reveal the DC components.For the FIR filters, i'm using an MAC FIR Filter Core by xilinx. The coefficients are obtained from matlab fdatool.
; XILINX CORE Generator(tm) Distributed Arithmetic FIR filter coefficient (.COE) File ; Generated by MATLAB(R) 7.0 and the Filter Design Toolbox 3.0. Radix = 16; Coefficient_Width = 16; CoefData = 3b32,3ce5,3e3e,3f37,3fce,4000,3fce,3f37,3e3e,3ce5,3b32;
Moving on, i need to design a Matched Filter to find the proper sampling instant for the symbols. Also, due to carrier offset, the phase is rotating. I understand that a phase detector, a loop filter and an NCO is required to recover the phase.
Going one step at a time, Would appreciate if you can direct me to articles that explain practical implementations of a Matched Filter.
Thanks, snipped-for-privacy@gmail.com