Increased Group-Delay Slope Loop System for Enhanced-Resolution Analog Signal Processing

A novel increased group-delay slope loop scheme is proposed to enhance the time-frequency resolution of dispersive delay structure (DDS) components for microwave analog signal processing systems. In this scheme, the signal at the output of the DDS is regenerated by an amplifier and reinjected via a nondispersive delay line toward its input along a loop. At each pass across the DDS, the effective group-delay slope of the system is increased so that, after n turns along the loop, the time-frequency resolution has been enhanced by a factor n. This approach provides a solution to the unpractical approach of cascading n DDS units, which would lead to excessively large device footprint, unacceptably high insertion loss, and severe signal-to-noise reduction. The proposed scheme is implemented in a proof-of-concept circuit using a C-section all-pass network DDS and demonstrated experimentally in a frequency meter and in a frequency discriminator. Possible improvements for higher performance are discussed.