Isolation analysis of correlator mixer for digital frequency discriminator error improvement

This paper has presented the design of a phase correlator for digital frequency discriminator (DFD) that operates in the 2.0 to 6.0 GHz frequency range. The frequency discrimination accuracy of the DFD with the isolation of correlator mixer is analyzed, and it is shown that LO-RF isolation has much effect on frequency discrimination error by deriving relating equations between LO-RF isolation and phase performance. More than 5.7° phase error and 1.27 MHz frequency error will be happened from less than 20 dB LO-RF isolation. The RMS phase error of the designed phase correlator is 4.57° and the frequency accuracy is 1.02 MHz.