Crosstalk characteristics for symmetrical star quad cable with unbalanced terminations

• Published in: Electronics & communications in Japan. Part 1, Communications Vol. 67; no. 11; pp. 55 - 65
• Main Authors: Tomita, Nobuo, Kawaguchi, Tokihiro, Ohmura, Makoto
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc., A Wiley Company 1984
• ISSN: 8756-6621; 1520-6424
• DOI: 10.1002/ecja.4400671108

In subscriber line signalling systems using the telephone network for selective control of specified on‐premises devices, with consideration of the exchange configuration, there are cases when the subscriber channel is used in an unbalanced condition and the channel crosstalk characteristics become a problem. Up to this time, we know of no studies which have considered the effects of subscriber line crosstalk characteristics with unbalanced terminations. In this paper, we first establish models and derive theoretical equations for two categories of line crosstalk‐the first being the case where either the disturbing or the disturbed line has an unbalanced termination, and the second being the case where both lines have unbalanced terminations. Results obtained in the theoretical analysis are verified by experiments. Next, using a theoretical expression considering the relationship between crosstalk coupling and crosstalk attenuation, it is found that, the subscriber in the low‐frequency region where the coupling impedance has no effect, the single‐circuit unbalanced termination gives about the same performance as the balanced termination, whereas the crosstalk attenuation is about 50 dB lower when both circuits have unbalanced terminations: In addition, for the case where both lines have unbalanced determinations, we present a method of specifying the signal frequency and line termination impedance, which are important parameters for the design of the above‐mentioned signalling systems from the standpoint of achieving the desired crosstalk characteristics.