| 摘要 |
<p>A bandwidth reduction technique for use in digital systems wherein elements of a data signal modulate quadrature-related carriers. This modulation, referred to as quadrature amplitude modulation (QAM) or phase shift keying (PSK), generates a double-sideband signal which is transmitted in a variety of communications systems. In accordance with the present invention, the above-described double-sideband signal is filtered (103) to form a single-sideband signal prior to transmission. While this use of a single-sideband signal, in lieu of a double-sideband signal, effectively doubles the system capacity by permitting the use of two communications systems in the bandwidth previously occupied by one system, the filtering process (103) contaminates the data signal elements. To recover the data signal elements at the receiver, received signal elements are formed by extracting the carrier signals (107). Next, these received signal elements are altered by preselected quantities to form estimates of each data signal element (301, 302...307). A comparison of the formed estimates (318) against the set of permissible values for each data signal element then determines which estimate is correct.</p> |
