Browse Prior Art Database

Reference Feedback Circuit for Phase Modulated Signal Demodulation

IP.com Disclosure Number: IPCOM000083217D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Shadden, VA: AUTHOR

Abstract

This circuit maintains zero crossing information in the presence of: (1) low-frequency crosstalk, (2) DC offset, and (3) random bias due to pattern sensitivities.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Reference Feedback Circuit for Phase Modulated Signal Demodulation

This circuit maintains zero crossing information in the presence of: (1) low- frequency crosstalk, (2) DC offset, and (3) random bias due to pattern sensitivities.

The reference feedback circuit, Fig. 2, replaces the ground reference circuit shown in Fig. 1.

The reference circuit, details shown in Fig. 3, operates as follows. Operational amplifier A1 serves as a buffer between the input signal and the reference generator. Diode D1, resistor R1, and capacitor C1 generate the positive component for the reference, whereas diode D2, resistor R2, and capacitor C2 generate the negative component. The positive and negative components are summed through resistors R3 and R4.

Potientiometer P1 is used to null any offset in the reference circuit due to component tolerance. Operational amplifier A2 is used to set the gain of the reference (gain nominally set to 1). The values of the components are determined by setting:

(Image Omitted)

Fig. 4 shows waveforms using the original method and Fig. 5 shows waveforms with the feedback reference method in the presence of crosstalk, pattern bias, and DC offset. Assuming no other types of distortion present, the latter method will run error-free while the original method will not.

1

Page 2 of 2

2

[This page contains 4 pictures or other non-text objects]