Antimultipath communication by injecting tone into null in signal spectrum

Claim 3

Apparatus for radio communication of digital data with multipath fading compensation comprised of a transmitter having means for splitting said digital data into inphase and quadrature signals, means for applying balanced encoding of data for each signal to create a null at the center of a radio carrier frequency output spectrum, means for signal band limiting each of said balanced encoded signals, means for quadrature modulation of each signal with a calibration tone, and means for summing the resultant signals with said calibration tone, thereby inserting said calibration tone at said null of the balanced data encoded radio frequency spectrum, and a receiver of said radio frequency output of said transmitter having means for extracting the signal received by band pass filtering and means for band pass filtering said calibration tone from the band pass filtered signal received, means for mixing the band pass filtered calibration tone with itself, means for low pass filtering the output of said mixing means to produce a base band signal, means for threshold comparison of said base signal with a test level, and means for algebraically dividing said band pass filtered calibration tone by the output of said threshold comparison means, and means for mixing said calibration tone with said extracted signal received, thereby compensating for multipath fading, wherein said calibration tone at said transmitter coincides in phase and frequency with the transmitted radio carrier frequency signal for coherent demodulation of data at the receiver.

Claim 4

Apparatus for radio communication of digital data with multipath fading compensation comprised of a transmitter having means for splitting said digital data into inphase and quadrature signals, means for applying balanced encoding of data for each signal to create a null at the center of a radio carrier frequency output spectrum, means for signal band limiting each of said balanced encoded signals, means for quadrature modulation of each signal with a calibration tone, and means for summing the resultant signals with said calibration tone, thereby inserting said calibration tone at said null of the balanced data encoded radio frequency spectrum, and a receiver of said radio frequency output of said transmitter having means for extracting the signal received by band pass filtering and means for band pass filtering said calibration tone from the band pass filtered signal received, means for mixing the band pass filtered calibration tone with itself, means for low pass filtering the output of said mixing means to produce a base band signal, means for threshold comparison of said base signal with a test level, and means for algebraically dividing said band pass filtered calibration tone by the output of said threshold comparison means, and means for mixing said calibration tone with said extracted signal received, thereby compensating for multipath fading, wherein said calibration tone at said transmitter coincides in phase and frequency with the transmitted radio carrier frequency signal for coherent demodulation of data at the receiver.

Claim 5

Apparatus for radio communication of digital data with multipath fading compensation comprised of a transmitter having means for splitting digital data into inphase and quadrature signals, means for applying balanced encoding of data for each signal to create a null at the center of a data modulated radio frequency output spectrum, means for signal band limiting each of said balanced encoded signals, means for quadrature modulation of the two signals, and means for summing said signals with a calibration tone, thereby inserting said calibration tone at said null of the radio frequency output spectrum, and a base band receiver of said data modulated radio frequency carrier of said transmitter with said calibration tone, said receiver having means for dividing a received signal into inphase and quadrature base band signals, separate means for each of said inphase and quadrature base band signals for calibration tone detection and signal match filtering, means for mixing the detected calibration tone and match filtered signals of the inphase base band signal and separately of the quadrature phase signal, and means for summing the outputs of said separate mixing means to combine them into a signal suitable for sampling and data detection.

Claim 6

Apparatus for radio communication of digital data with multipath fading compensation comprised of a transmitter having means for splitting digital data into inphase and quadrature signals, means for applying balanced encoding of data for each signal to create a null at the center of a data modulated radio frequency output spectrum, means for signal band limiting each of said balanced encoded signals, means for quadrature modulation of the two signals, and means for summing said signals with a calibration tone, thereby inserting said calibration tone at said null of the radio frequency output spectrum, and a base band receiver of said data modulated radio frequency carrier of said transmitter with said calibration tone, said receiver having means for dividing a received signal into inphase and quadrature base band signals, separate means for each of said inphase and quadrature base band signals for calibration tone detection and signal match filtering, means for mixing the detected calibration tone and match filtered signals of the inphase base band signal and separately of the quadrature phase signal, and means for summing the outputs of said separate mixing means to combine them into a signal suitable for sampling and data detection.

Claim 7

Apparatus as defined in claim 3 including a predetection band pass filter of the signal received before dividing into inphase and quadrature base band signals for noise band limiting.