Reduction of crosstalk noise in modular jack for high-speed differential signal interconnection

Crosstalk noise has become a significant problem in the design of high-spee d digital interconnections. In this paper, we demonstrate a crosstalk reduc tion method, which has been successfully applied to the design of a CAT-5E modular jack. The CAT-5E is a newly adopted cabling and connector standard for advanced cabling network systems to assure more robust, reliable and hi gh-speed operation, which is based on differential mode signal transmission using unshielded twist pair (UTP) cable. The improved design of the modular jack shows minimal crosstalk noise and r eturn loss over a wide range of manufacturing conditions. The improved cros stalk characteristics of the modular jack were accomplished by inserting em bedded capacitors on the printed circuit board (PCB) of the modular jack. T he embedded capacitors compensate for the unbalanced capacitive crosstalk t hat occurs in the plug and insert. In particular, the embedded balancing ca pacitor is designed to have maximum capacitance, with limited PCB area, by using a double-sided PCB design. Less than -45 dB near-end-crosstalk (NEXT) was achieved after the crosstalk noise compensation, satisfying the CAT-5E specification for frequencies up to 100 MHz.