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Data Distortion Compensation with Transmission Line Termination Network

IP.com Disclosure Number: IPCOM000080351D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Walewski, LG: AUTHOR

Abstract

Adverse effects in communicating data over transmission lines are significantly reduced by parallel compensating networks at the receiver. Elimination of baseline shift following an odd number of FM "0" bits, sometimes referred to as intersymbol interference, is obtained and the 1 and 0 bit amplitude differences due to low-pass transmission line filtering is reduced. Zero-crossing detection for data recovery becomes possible for applications involving relatively long transmission lines. Low-pass filtering (LPF) effects of transmissions lines in communicating continuous-phase frequency modulated (FM) data, results in amplitude and phase or baseline distortion. LPF distortion is encountered when data is applied and recovered to and from magnetic tape, discs, drums or whatever data is sent through a transmission line.

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Data Distortion Compensation with Transmission Line Termination Network

Adverse effects in communicating data over transmission lines are significantly reduced by parallel compensating networks at the receiver. Elimination of baseline shift following an odd number of FM "0" bits, sometimes referred to as intersymbol interference, is obtained and the 1 and 0 bit amplitude differences due to low-pass transmission line filtering is reduced. Zero-crossing detection for data recovery becomes possible for applications involving relatively long transmission lines. Low-pass filtering (LPF) effects of transmissions lines in communicating continuous-phase frequency modulated (FM) data, results in amplitude and phase or baseline distortion. LPF distortion is encountered when data is applied and recovered to and from magnetic tape, discs, drums or whatever data is sent through a transmission line.

In the example shown in Fig. 1, FM is introduced by a source, not shown, to transmission line 10 with output lines 11 and 12 terminated in characteristic impedance Zo 15. The data introduced to line 10 is shown in Fig. 2A. When only Zo is used for termination of 10, the output at lines 10 and 11 is shown in Fig. 2B. Positive "0" bit 16 causes a positive baseline shift as shown generally at 17 which decays exponentially, as does a negative baseline shift such as 18 in response to a negative 0 bit 19. The time constant Tc of the baseline shift decay is dependent on the distributed ca...