Digital frequency discriminator(DFD) error improvement by LO leakage compensation

This paper has presented the design of some phase correlators for two digital frequency discriminators (DFDs) of which operation is over the 2.0 to 6.0 GHz, or 6.0 to 18.0 GHz frequency range in electronic warfare system. The accuracy of frequency discrimination according to the isolation of correlator mixer are analyzed, and it is shown that LO-RF isolation has much effect on frequency discrimination error by deriving some analytic equations relating the LO-RF isolation and phase performance. We propose a novel method of phase sector compensation in order to improve frequency discriminating error. The phase error of the designed phase correlator is RMS 4.57° and the frequency accuracy is 0.95 MHz over the 2.0-6.0 GHz. Over the 6.0-18.0 GHz range, the phase error is 4.81°, RMS and discrimination accuracy is 1.49 MHz, RMS.