Title:
HIGH SPEED DEMODULATOR
Document Type and Number:
Japanese Patent JPS5539494
Kind Code:
A
Abstract:
A high speed modem suitable for operating with a switched network and capable of achieving essentially 9600 bit per second information transfer rate through the switched telephone network. The high bit rate is achieved notwithstanding the variations in the characteristics of the switched telephone network by phase and amplitude modulating a plurality of sub-carriers (39) at a relatively low baud rate. Correlation detection (35) is employed at the receiver (33-38) to extract or demodulate the information contained in the various sub-carriers. To allow correlation detection with orthogonal signals, each of the sub-carriers is harmonically related to a fundamental which fundamental is, however, slightly higher than the baud rate. This allows the receiver (33-38) to delay correlation for a "gap" time, which reduces the effect of transients produced by modulation and also provides greater tolerance to inter-symbol distortion. Since the fundamental of all the sub-carriers is higher than the baud rate, the receiver "sees" orthogonal signals during the integration or correlation time which is maintained as the period of the fundamental. In addition to the information sub-carriers, a pair of unmodulated sub-carriers (36) are also transmitted to enable the receiver to maintain the correlation interval in proper synchronization with the transmitter, and to correct for phase distortion and frequency offset.
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Inventors:
UIRIAMU II KIISURAA
DONARUDO ERU BITSUTSUAA
POORU TEI TATSUKAA
DONARUDO ERU BITSUTSUAA
POORU TEI TATSUKAA
Application Number:
JP10562279A
Publication Date:
March 19, 1980
Filing Date:
August 21, 1979
Export Citation:
Assignee:
UNIV ILLINOIS
International Classes:
H04L27/34; H04L27/26; H04L27/38; (IPC1-7): H04L27/00
Domestic Patent References:
| JPS52109811A | 1977-09-14 |