Type-Based Group Delay Equalization Technique

This paper presents a patented type-based group- delay equalization technique to compensate for in-band group- delay distortion typically existing in analog/RF filter circuits. The underlining principle is that for a given modulation scheme and pulse-shaping function, the modulated signal has a unique statistical distribution, and that when the modulated signal passes through a circuit, any in-band group-delay distortion in the circuit distorts its output statistical distribution. The technique employs an equalization filter to minimize the in-band group-delay distortion, with the filter coefficients derived from a measure of the distortion in the output statistical distribution using a weighted nonlinear least square algorithm. It requires simple analog and digital hardware and firmware to implement, and its implementation is inherently adaptive, capable of tracking and compensating for any variation in the group-delay distortion characteristic due to component aging and temperature variation. Computer simulations have been performed to show that an accurate equalization filter can be obtained to effectively compensate for the group-delay distortion, achieving significant performance improvements.