System for improving the quality of a received radio signal
First Claim
1. A method of enabling frequency hopping between a signal of a first frequency and a signal of a second frequency, which method comprises:
- transmitting the signal from a first transmitting antenna;
transmitting the same signal from a second transmitting antenna after delaying the signal by a preselected time period;
processing in a receiver the received signals from the first and second transmitting antennas;
hopping the frequency of transmission from the first frequency to the second frequency; and
changing the time period of the delay at baseband as a function of the frequency of the signal to be transmitted.
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Accused Products
Abstract
A delay spread is created in a digital radio signal to reduce the coherence bandwidth and facilitate frequency hopping to reduce the effect of fading losses within an enclosed propagation environment The delay spread is introduced into the signal in several ways. One technique disclosed employs a transmitter with two separate antennas one of which transmits the digital signal and the other of which transmits the same signal after a phase delay has been introduced into the signal. The carrier frequency of the signals is hopped between at least two frequencies and the receiver processes the resulting signals. In another embodiment, a single transmit antenna is used but the signal is received by two different antennas with the output signal from one of those antennas being phase delayed before combining it with the other prior to processing by the receiver circuitry. Phase delay is also introduced at baseband into the signals to be transmitted by rotating the I and Q components of the waveforms before modulation.
128 Citations
21 Claims
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1. A method of enabling frequency hopping between a signal of a first frequency and a signal of a second frequency, which method comprises:
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transmitting the signal from a first transmitting antenna; transmitting the same signal from a second transmitting antenna after delaying the signal by a preselected time period; processing in a receiver the received signals from the first and second transmitting antennas; hopping the frequency of transmission from the first frequency to the second frequency; and changing the time period of the delay at baseband as a function of the frequency of the signal to be transmitted. - View Dependent Claims (2, 3)
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4. A system for enabling frequency hopping between a signal of a first frequency and a signal of a second frequency, comprising:
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means for transmitting the signal from a first transmitting antenna; means for transmitting the same signal from a second transmitting antenna after delaying the signal by a preselected time period; means for processing in a receiver the received signals from the first and second transmitting antennas; means for hopping the frequency of transmission from the first frequency to the second frequency; and means for changing the time period of the delay at baseband as a function of the frequency of the signal to be transmitted. - View Dependent Claims (5, 6)
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7. In a slow frequency hopped digital communication system, a transmitter comprising:
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means for generating a slow frequency hopped digital communication signal; and means for transmitting said signal on a plurality of different antennas with each signal being transmitted from each antenna separated from the other signals by phase differences that change at baseband as a function of hop frequency. - View Dependent Claims (8, 9, 10)
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11. In a slow frequency hopped digital communication system, the method which comprises:
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generating a slow frequency hopped digital communication signal; and transmitting said signal on a plurality of different antennas with each signal being transmitted from each antenna separated from the other signals by phase offsets that change at baseband as a function of hop frequency. - View Dependent Claims (12, 13, 14, 15)
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16. A method of enabling frequency hopping between a signal of a first frequency and a signal at baseband of a second frequency, which method comprises:
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transmitting the signal from a first transmitting antenna; transmitting the same signal from a second transmitting antenna after delaying at baseband the signal by a preselected time period, said delay between the signal transmitted from the first and second transmitting antennas being small relative to a symbol period of the signal; processing in a receiver the received signals from the first and second transmitting antennas; and hopping the frequency of transmission from the first frequency to the second frequency. - View Dependent Claims (17, 18)
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19. A system for enabling frequency hopping between a signal of a first frequency and a signal of a second frequency, comprising:
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means for transmitting the signal from a first transmitting antenna; means for transmitting the same signal from a second transmitting antenna after delaying the signal at baseband by a preselected time period, said delay between the signal transmitted from the first and second transmitting antennas being small relative to a symbol period of the signal; means for processing in a receiver the received signals from the first and second transmitting antennas; and means for hopping the frequency of transmission from the first frequency to the second frequency. - View Dependent Claims (20, 21)
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Specification