Quadrature vestigial sideband digital communications method
AssigneeThe Aerospace Corporation
InventorsJohn J. Poklemba, Gregory S. Mitchell
Life of this patent
Estimating the term…
Abstract
A quadrature vestigial sideband (QVSB) communication system provide bandwidth efficient data transmission using cross coupled data signaling during both transmit and receive having controlled intersymbol interference. The QVSB modem includes cross coupled arm transmit and receive data filtering on both of the I&Q channels providing a bandwidth efficient QVSB spectra. A quadrature crosstalk maximum likelihood sequence estimator implements a Viterbi decoding algorithm for providing estimated data sequence outputs. The receiver is a coherently aided demodulator synchronized by a synchronization loop providing time and phase references using the estimated data sequence outputs.
Claims20
A method of modulating a carrier for transmitting a quadrature vestigial single sideband (QVSB) signal for communicating I symbols and Q symbols, the method comprising the steps of,
- cross arm filtering the I and Q symbols for generating i filter responses and iH filter responses from the I symbols and for generating qH filter responses and q filter responses from the Q symbols,
- combining the i and qH filter responses into an I channel overlapping filter signal and the q and iH filter responses into a Q channel overlapping filter signal, and
- quadrature modulating a carrier by the I and Q channel overlapping filter responses into a modulated inphase signal and a modulated quadrature signal, the Q channel overlapping filter response modulates the carrier shifted ninety degrees from the carrier modulating the I channel overlapping filter responses for modulating the carrier in quadrature,
- summing the modulated inphase signal and a modulated quadrature signal into the QVSB signal, and
- transmitting the QVSB signal for communicating the I and Q symbols over a single sideband.
A method of demodulating a transmitted quadrature vestigial sideband (QVSB) signal modulating a carrier in quadrature by I and Q overlapping filter responses respectively from I and Q symbols, the method comprising the steps of,
- receiving the transmitted QVSB signal as a received QVSB signal,
- splitting the received QVSB signal into an I channel QVSB signal and a Q channel QVSB signal,
- coherent demodulating the I channel QVSB signal by a replicated carrier and the Q channel QVSB signal by a ninety degree phase shifted replicated carrier for respectively generating the I and Q overlapping filter responses,
- cross arm filtering the I and Q overlapping filter responses for generating ĩ+{tilde over (q)}H and −{tilde over (q)}+ĩH match filter responses from the I overlapping filter responses and for generating ĩ+{tilde over (q)}H and {tilde over (q)}−ĩH matched filter responses from the Q overlapping filter responses, and
- combining both of the ĩ+{tilde over (q)}H matched filter responses into an I channel response signal and the −{tilde over (q)}+ĩH and {tilde over (q)}−ĩH matched filter responses into a Q channel response signal.
A method of communicating I and Q symbols, the method comprising the steps of,
- cross arm filtering the I and Q symbols for generating i filter responses and iH filter responses from the I symbols and for generating qH filter responses and q filter responses from the Q symbols,
- combining the i and iH filter responses into an I channel overlapping filter signal and the q and qH filter responses into a Q channel overlapping filter signal, and
- quadrature modulating a carrier by the I and Q channel overlapping filter responses into a modulated inphase signal and a modulated quadrature signal, the Q channel overlapping filter response modulates the carrier shifted ninety degrees from the carrier modulating the I channel overlapping filter responses for modulating the carrier in quadrature,
- combining the modulated inphase signal and a modulated quadrature signal into a quadrature vestigial single sideband (QVSB),
- transmitting the QVSB signal for communicating the I and Q symbols over a single sideband,
- receiving the transmitted QVSB signal as a received QVSB signal,
- splitting the received QVSB signal into an I channel QVSB signal and a Q channel QVSB signal,
- coherent demodulating the I channel QVSB signal by a replicated carrier and the Q channel QVSB signal by a ninety degree phase shifted replicated carrier for respectively generating the I and Q overlapping filter responses,
- cross arm filtering the I and Q overlapping filter responses for generating ĩ+{tilde over (q)}H and −{tilde over (q)}+ĩH match filter responses from the I overlapping filter responses and for generating ĩ+{tilde over (q)}H and {tilde over (q)}−ĩH matched filter responses from the Q overlapping filter responses, and
- combining the ĩ+{tilde over (q)}H matched filter responses into an I channel response signal and −{tilde over (q)}+ĩH and {tilde over (q)}−ĩH matched filter responses into a Q channel response signal.
Dependencies are inferred from the claim text.