Transmitted reference spread spectrum communication using a single carrier with two mutually orthogonal modulated basis vectors
US5559828A · kind A · utility
Inventors
Key dates
| Filing date | Oct 18, 1994 |
| Grant date | Sep 24, 1996 |
| Priority date | — |
| Expiry date | Oct 18, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/18
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
The disclosed spread spectrum system has the reference transmitted on one phase (basis vector) of a .pi./2-offset QPSK signal, and the spread data signal transmitted on another phase (basis vector). The two received phases are combined to recover the baseband signal. Such a transmission system is tolerant to multipath dispersion since all delay paths carry an appropriately delayed reference and signal path induced dispersion on the spread data signal is also present on the reference. If one of the two signals is delayed by a predetermined time interval and a corresponding delay is present in each of two cross-coupled signal processing paths following a conventional I-Q demodulator, the resulting two phase quadrature baseband signals may be combined to form a replica of the original baseband signal. The resultant asynchronous demodulation eliminates the usual requirement for carrier lock at the receiver and is therefore tolerant to Doppler shifts and other frequency errors. Both the asynchronous and synchronous (coherent demodulation) embodiments offer multiple use of the same center frequency through a novel "delay division" multiplexing concept.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.