H - Electricity – 04 – L
Patent
H - Electricity
04
L
340/205, 329/3,
H04L 25/49 (2006.01)
Patent
CA 1137571
1 PHN. 9386. ABSTRACT: A method of demodulating a quadphase coded data signal and a receiver for carrying out the method. A quadphase code comprises four elementary waveforms 1,1; 0,1; 0,0; and 1,0, each waveform repre- senting two bits of an original non-coded binary sig- nal. Each elementary waveform consists of four half bit intervals, the signal corresponding to the first and the second bit, respectively, being transmitted in the first and the second half bit intervals and the signal corresponding to the inverted values of the first and the second bit, respectively, being trans- mitted in the third and the fourth half bit intervals. In a receiver such a signal at an input terminal is sampled in each of the four half bit intervals by means of two sample-and-hold circuits and two sampling switches. In principle, all informa- tion is already available after the sampling operations in the first and the second half bit intervals, by the circuits but by utilizing all four samples a proper protection from noise, interference and zero level shifts is obtained. Comparators 6 and 7 determine, respectively, the difference of the samples taken is the first and the third half bit intervals and the difference of the samples taken in the second and the fourth bit intervals. A positive difference represents a logic 1, a negative difference a logic 0. A combin- ing circuit interleaves the two difference signals obtained, the signal from comparator being delayed half a bit interval by a delay circuit, to produce the decoded original signal at the output terminal 18. A clock synchronization device controls the timing. The method and the receiver have applica- tion in the field of data transmission over physical wire pairs and in the field of magnetic and optical recording.
347980
Carasso Marino G.
de Jager Frank
Van Doorn Rudolf A.
Verboom Johannes J.
N.v. Philips Gloeilampenfabrieken
Van Steinburg C.e.
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