One frequency repeater for a digital microwave radio system with cancellation of transmitter-to-receiver interference
First Claim
1. A one frequency repeater for a digital radio wave transmission system wherein a carrier is modulated by a digital baseband signal and is transmitted as a digital radio wave signal, said repeater comprising:
- a first digital signal source for producing a first digital baseband signal;
transmitter circuit means coupled to said first digital signal source for producing a first digital radio wave signal modulated by said first digital baseband signal, said first digital radio wave having a first carrier frequency;
transmitting antenna means for radiating said first radio frequency signal supplied from said transmitter circuit means;
receiving antenna means for receiving a second digital radio wave signal modulated by a second digital baseband signal, said second digital radio wave signal having a second carrier frequency substantially equal to said first carrier frequency, said receiving antenna means receiving said first digital radio wave signal as a transmitter-to-receiver interference signal due to coupling between said first transmitting antenna means and said first receiving antenna means;
receiver circuit means for extracting said second digital baseband signal by demodulating said second radio wave signal received at said receiving antenna, said demodulated second digital baseband signal being accompanied by a baseband interference signal derived from said transmitter-to-receiver interference signal;
means coupled to said first digital signal source for producing an estimated-interference signal corresponding to said baseband interference signal from said first digital baseband signal, said estimated-interference signal producing means comprising transversal filter means comprising a delay line with a predetermined number of tap gains; and
interference cancelling means coupled to said receiver circuit means and said estimated-interference signal producing means for cancelling said baseband interference signal from an output signal of said receiver circuit means using said estimated-interference signal to thereby produce said demodulated second digital baseband signal without said baseband interference signal;
decision circuit means for detecting said second digital baseband signal from an output of said interference cancelling means and regenerating said second digital baseband signal; and
tap gain control means for controlling said tap gains, said tap gain control means comprising first subtracting means for subtracting said regenerated second digital baseband signal from said output signal of said interference cancelling means and providing a first error signal, first multiplier means for multiplying said first digital baseband signal by said first error signal and providing a multiplied signal, and low-pass filter means for smoothing said multiplied signal, said smoothed multiplied signal being supplied to said transversal filter means to control said tap gains so that said first error signal is zero.
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Accused Products
Abstract
A digital microwave radio repeater using the same carrier frequency for the transmitter and the receiver carriers for improving the frequency utilization efficiency. The transmitter-to-receiver interference signal is cancelled by producing an estimated-interference signal of the interference signal from the digital baseband signal by the use of a transversal filter and by subtracting the estimated-interference signal from the received signal. The estimated-interference signal is also produced by frequency shifting a digital modulated signal in the transmitter. The transmitter carrier frequency is locked to the receiver carrier frequency by the use of a phase-locking technique, so that the interference signal is reduced.
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Citations
37 Claims
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1. A one frequency repeater for a digital radio wave transmission system wherein a carrier is modulated by a digital baseband signal and is transmitted as a digital radio wave signal, said repeater comprising:
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a first digital signal source for producing a first digital baseband signal; transmitter circuit means coupled to said first digital signal source for producing a first digital radio wave signal modulated by said first digital baseband signal, said first digital radio wave having a first carrier frequency; transmitting antenna means for radiating said first radio frequency signal supplied from said transmitter circuit means; receiving antenna means for receiving a second digital radio wave signal modulated by a second digital baseband signal, said second digital radio wave signal having a second carrier frequency substantially equal to said first carrier frequency, said receiving antenna means receiving said first digital radio wave signal as a transmitter-to-receiver interference signal due to coupling between said first transmitting antenna means and said first receiving antenna means; receiver circuit means for extracting said second digital baseband signal by demodulating said second radio wave signal received at said receiving antenna, said demodulated second digital baseband signal being accompanied by a baseband interference signal derived from said transmitter-to-receiver interference signal; means coupled to said first digital signal source for producing an estimated-interference signal corresponding to said baseband interference signal from said first digital baseband signal, said estimated-interference signal producing means comprising transversal filter means comprising a delay line with a predetermined number of tap gains; and interference cancelling means coupled to said receiver circuit means and said estimated-interference signal producing means for cancelling said baseband interference signal from an output signal of said receiver circuit means using said estimated-interference signal to thereby produce said demodulated second digital baseband signal without said baseband interference signal; decision circuit means for detecting said second digital baseband signal from an output of said interference cancelling means and regenerating said second digital baseband signal; and tap gain control means for controlling said tap gains, said tap gain control means comprising first subtracting means for subtracting said regenerated second digital baseband signal from said output signal of said interference cancelling means and providing a first error signal, first multiplier means for multiplying said first digital baseband signal by said first error signal and providing a multiplied signal, and low-pass filter means for smoothing said multiplied signal, said smoothed multiplied signal being supplied to said transversal filter means to control said tap gains so that said first error signal is zero. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A one-frequency repeater for a digital radio wave transmission system wherein a carrier is modulated by a digital baseband signal and is transmitted as a digital radio wave signal, said repeater comprising:
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a first digital signal source for producing a first digital baseband signal; transmitter circuit means coupled to said first digital signal source for producing a first digital radio wave signal modulated by said first digital baseband signal, said first digital radio wave having a first carrier frequency; transmitting antenna means for radiating said first radio frequency signal supplied from said transmitter circuit means; receiving antenna means for receiving a second digital radio wave signal modulated by a second digital baseband signal, said second digital radio wave signal having a second carrier frequency substantially equal to said first carrier frequency, said receiving antenna means receiving said first digital radio wave signal as a transmitter-to-receiver interference signal due to coupling between said first transmitting antenna means and said first receiving antenna means; receiver circuit means for extracting said second digital baseband signal by demodulating said second radio wave signal received at said receiving antenna, said demodulated second digital baseband signal being accompanied by a baseband interference signal derived from said transmitter-to-receiver interference signal; means coupled to said first digital signal source for producing an estimated-interference signal corresponding to said baseband interference signal from said first digital baseband signal, said estimated-interference signal producing means comprising;
first local oscillator means for generating a first frequency signal;
first phase shifter means for phase-shifting by π
/2 said first frequency signal;
first multiplier means for multiplying said first digital baseband signal by said first frequency signal;
second multiplier means for multiplying said first digital baseband signal by said phase-shifted first frequency signal;
second local oscillator means for generating a second frequency signal, said first and second frequency signals having a frequency difference corresponding to a frequency difference between said first and second carrier frequencies;
second phase shifter means for phase-shifting by π
/2 said second frequency signal;
third multiplier means for multiplying an output from said first multiplier means by said second frequency signal;
fourth multiplier means for multiplying an output from said second multiplier means by said phase-shifted second frequency signal;
adder means for adding an output signal of said third multiplier means and an output signal of said fourth multiplier means;
coefficient generating means for generating a coefficient representing an amount of said transmitter-to-receiver interference; and
fifth multiplier means for multiplying an output signal of said adder means by said coefficient, said fifth multiplier means providing said estimated-interference signal; andinterference cancelling means coupled to said receiver circuit means and said estimated-interference signal producing means for cancelling said baseband interference signal from an output signal of said receiver circuit means using said estimated-interference signal to thereby produce said demodulated second digital baseband signal without said baseband interference signal. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A one-frequency two-way repeater for a digital transmission system wherein first and second digital microwave signals are received at first and second receiving antenna means and regenerated as third and fourth digital microwave signals, respectively, said third and fourth digital microwave signals being radiated from first and second transmitting antenna means, respectively, said first and second digital microwave signals carrying first and second digital baseband signals, respectively, said first, second, third and fourth digital microwave signals having a first, a second, a third and a fourth carrier frequency, respectively, said first, second, third and fourth carrier frequencies being substantially equal to one another, said repeater comprising:
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said first receiving antenna means and said second transmitting antenna means being disposed side by side and directed in a common first direction, said first receiving antenna means and said second antenna means having a side-to-side antenna coupling whereby said first receiving antenna means receives said fourth digital microwave signal as a first transmitter-to-receiver interference signal; said first transmitting antenna means and said second receiving antenna means being disposed side by said and directed in a common second direction opposite to said first direction, said first transmitting antenna means and said second receiving antenna means having a side-to-side antenna coupling whereby said second receiving antenna means receives said third digital microwave signal as a second transmitter-to-receiver interference signal; first receiver circuit means connected to said first receiving antenna means for extracting said first digital baseband signal by demodulating said first digital microwave signal received at said first receiving antenna means, said demodulated first digital baseband signal being accompanied by a first baseband interference signal derived from said first transmitter-to-receiver interference signal; first decision circuit means for detecting said demodulated first digital baseband signal and regenerating said first digital baseband signal as a third digital baseband signal; first transmitter circuit means for producing said third digital microwave signal modulated by said third digital baseband signal and for supplying said third digital microwave signal to said first transmitting antenna means; second receiver circuit means connected to said second receiving antenna means and for extracting said second digital baseband signal by demodulating said second digital microwave signal received at said second receiving antenna means, said demodulated second digital baseband signal being accompanied by a second baseband interference signal derived from said second transmitter-to-receiver interference signal; second decision circuit means for detecting said demodulated second digital baseband signal and regenerating said second digital baseband signal as a fourth digital baseband signal; second transmitter circuit means for producing said fourth digital microwave signal modulated by said fourth digital baseband signal and for supplying said fourth digital microwave signal to said second transmitting antenna means; first estimated-interference signal producing means coupled to said second decision circuit means for producing a first estimated-interference signal corresponding to said first baseband interference signal from said fourth digital baseband signal, said first estimated-interference signal producing means comprising transversal filter means comprising a delay line having a predetermined number of tap gains; first interference cancelling means coupled to said first estimated-interference signal producing means for cancelling said first baseband interference signal from an output signal of said first receiver circuit means using said first estimated-interference signal, to thereby obtain said demodulated first digital baseband signal without said first baseband interference signal; second estimated-interference signal producing means coupled to said first decision circuit means for producing a second estimated-interference signal corresponding to said second baseband interference signal from said third digital baseband signal; and second interference cancelling means coupled to said second estimated-interference signal producing means for cancelling said second baseband interference signal from an output signal of said second receiver circuit means using said second estimated-interference signal, to thereby obtain said demodulated second digital baseband signal without said second baseband interference signal. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A one-frequency two-way repeater for a digital transmission system wherein first and second digital microwave signals are received at first and second receiving antenna means and regenerated as third and fourth digital microwave signals, respectively, said third and fourth digital microwave signals being radiated from first and second transmitting antenna means, respectively, said first and second digital microwave signals carrying a first and a second digital baseband signal, respectively, said first, second, third and fourth digital microwave signals having first, second, third and fourth carrier frequencies, respectively, said first, second, third and fourth carrier frequencies beinbg substantially equal to one another said repeater comprising:
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said first receiving antenna means and said second transmitting antenna means being disposed side by side and directed in a common first direction, said first receiving antenna means and said second antenna means having a side-to-side antenna coupling whereby said first receiving antenna means receives said fourth digital microwave signal as a first transmitter-to-receiver interference signal; said first transmitting antenna means and said second receiving antenna means being disposed side by side and directed in a common second direction opposite to said first direction, said first transmitting antenna means and said second receiving antenna means having a side-to-side antenna coupling whereby said second receiving antenna means receives said third digital microwave signal as a second transmitter-to-receiver interference signal; first receiver circuit means connected to said first receiving antenna means for extracting said first digital baseband signal by demodulating said first digital microwave signal received at said first receiving antenna means, said demodulated first digital baseband signal being accompanied by a first baseband interference signal derived from said transmitter-to-receiver interference signal; first decision circuit means for detecting said demodulated first digital baseband signal and regenerating said first digital baseband signal as a third digital baseband signal; first transmitter circuit means for producing said third digital microwave signal modulated by said third digital baseband signal and for supplying said third digital microwave signal to said first transmitting antenna means; second receiver circuit means connected to said second receiving antenna means for extracting said second digital baseband signal by demodulating said second digital microwave signal received by said second receiving antenna means, said demodulated second digital baseband signal being accompanied by a second baseband interference signal derived from said second transmitter-to-receiver interference signal; second decision circuit means for detecting said demodulated second digital baseband signal and regenerating said second digital baseband signal as a fourth digital baseband signal; second transmitter circuit means for producing said fourth digital microwave signal modulated by said fourth digital baseband signal and for supplying said fourth digital microwave signal to said second transmitting antenna means; first estimated-interference signal producing means coupled to said second decision circuit means for producing a first estimated-interference signal corresponding to said first baseband interference signal from said fourth digital baseband signal, said first estimated-interference signal producing means comprising;
first local oscillator means for generating a first frequency signal;
first phase shifter means for phase-shifting by π
/2 said first frequency signal;
first multiplier means for multiplying said fourth digital baseband signal by said first frequency signal;
second multiplier means for multiplying said fourth digital baseband signal by said phase-shifted first frequency signal;
second local oscillator means for generating a second frequency signal, said first and second frequency signals having a frequency difference corresponding to a frequency difference between said first and fourth carrier frequencies;
second phase shifter means for phase-shifting by π
/2 said second frequency signal;
third multiplier means for multiplying an output from said first multiplier means by said second frequency signal;
fourth multiplier means for multiplying an output from said second multiplier means by said phase-shifted second frequency signal;
first adder means for adding an output signal of said third multiplier means and an output signal of said fourth multiplier means;
first coefficient generating means for generating a first coefficient representing the amount of said first transmitter-to-receiver interference; and
fifth multiplier means for multiplying an output signal of said adder means by said first coefficient, said fifth multiplier means providing said first estimated-interference signal;first interference cancelling means coupled to said first estimated-interference signal producing means for cancelling said first baseband interference signal from an output signal of said first receiver circuit means using said first estimated-interference signal, to thereby obtain said demodulated first digital baseband signal without said first baseband interference signal; second estimated-interference signal producing means coupled to said first decision circuit means for producing a second estimated-interference signal, corresponding to said second baseband interference signal, from said third digital baseband signal; and second interference cancelling means coupled to said second estimated-interference signal producing means for cancelling said second baseband interference signal from an output signal of said second receiver circuit means using said second estimated-interference signal, to thereby obtain said demodulated second digital baseband signal without said second baseband interference signal. - View Dependent Claims (22)
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23. A one-frequency repeater for a digital radio wave transmission system wherein a carrier is modulated by a digital baseband signal and is transmitted as a digital radio wave signal, said repeater comprising:
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first transmitter circuit means comprising first modulating means for modulating a first intermediate frequency signal by a first digital baseband signal and providing a first modulated signal, and first frequency up converter means for converting a frequency of said first modulated signal to a first carrier frequency and providing a first digital radio wave signal; first transmitting antenna means for radiating said first digital radio wave signal; first receiving antenna means for receiving a second digital radio wave signal modulated by a second digital baseband signal, said second digital radio wave signal having a second carrier frequency substantially equal to said first carrier frequency, said first receiving antenna means receiving said first digital radio wave signal as a first transmitter-to-receiver interference signal due to coupling between said first transmitting antenna means and said first receiving antenna means; first receiver circuit means comprising frequency down converter means for converting a frequency of a radio wave signal received at said first receiving antenna means to a second intermediate frequency slightly different from said first intermediate frequency, said frequency down converter means providing a first digital intermediate frequency signal, said first digital intermediate frequency signal having a first signal component derived from said second digital radio wave signal and a first interference signal derived from said first transmitter-to-receiver interference signal; first frequency shifter means for frequency-shifting said first modulated signal from said first modulating means by a frequency difference of said first and second intermediate frequencies and providing a first frequency-shifted signal, said first frequency shifter means comprising;
first local oscillator means for generating a first local signal having a frequency equal to one of said first and second intermediate frequencies;
first phase shifter means for phase-shifting by π
/2 said first local signal;
second multiplier means for multiplying said first modulated signal by said first local signal;
third multiplier means for multiplying said first modulated signal by said phase-shifted first local signal;
first low-pass filter means connected to an output of said second multiplier means;
second low-pass filter means connected to an output of said third multiplier means;
second local oscillator means for generating a second local signal having a frequency equal to the other of said first and second intermediate frequencies;
second phase shifter means for phase-shifting by π
/2 said second local signal;
fourth multiplier means for multiplying an output from said first low-pass filter means by said second local signal;
fifth multiplier means for multiplying an output from said second low-pass filter means by said phase-shifted second local signal; and
first adder means for adding an output signal of said fourth multiplier means and an output signal of said fifth multiplier means, said first adder means providing said first frequency-shifted signal;first coefficient generating means for generating a first coefficient representing an amount of said first transmitter-to-receiver interference; sixth multiplier means coupled to said first frequency shifter means and said first coefficient generating means for multiplying said first frequency-shifted signal by said first coefficient and providing a first interference-removing signal; and first interference cancelling means coupled to said frequency down converter means and said sixth multiplier means for cancelling said first interference signal from said first digital intermediate signal using said first interference-removing signal. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31)
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32. A one-frequency repeater for a cochannel dual polarization transmission system wherein two independent digital baseband signals are carried by orthogonally related paired waves of a single carrier frequency signal, said repeater comprising:
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first and second signal sources for generating first and second digital baseband signals, respectively; first transmitter circuit means coupled to said first and second signal sources for producing a first pair of horizontally and vertically polarized waves of a first carrier frequency which carry said first and said second digital baseband signals; first transmitting antenna means for radiating said first pair of horizontally and vertically polarized waves; first receiving antenna means for receiving a second pair of horizontally and vertically polarized waves of a second carrier frequency which carry a third and a fourth digital baseband signal;
said second carrier frequency being substantially equal to said first carrier frequency means, said first pair of horizontally and vertically polarized waves being received at said first receiving antenna means as a first transmitter-to-receiver interference signal due to a coupling between said first transmitting antenna means and said second receiving antenna means;receiver circuit means comprising first and second demodulating means for independently modulating said second horizontally polarized wave signal and said second vertically polarized wave signal and extracting said third digital baseband signal and said fourth baseband signal, respectively, said extracted third digital baseband signal being accompanied by a first interference signal and a second interference signal caused by said first transmitter-to-receiver interference signal, said extracted fourth digital baseband signal being accompanied by a third interference signal and a fourth interference signal caused by said first transmitter-to-receiver interference signal; first estimated-interference signal producing means coupled to said first signal source for producing a first estimated-interference signal corresponding to said first interference signal from said first digital baseband signal; second estimated-inteference signal producing means coupled to said second signal source for producing a second estimated-interference signal corresponding to said second interference signal from second digital baseband signal; first interference cancelling means coupled to said first and second estimated-interference signal producing means for cancelling said first and second interference signal from an output of said first modulating means using said first and second estimated-interference signals; third estimated-interference signal producing means coupled to said first signal source for producing a third estimated-interference signal corresponding to said third interference signal from said first digital baseband signal; fourth estimated-interference signal producing means coupled to said second signal source for producing a fourth estimated-interference signal corresponding to said fourth interference signal from said second baseband signal; and second interference cancelling means coupled to said third and fourth estimated-interference signal producing means for cancelling said third and fourth interference signals from an output of said second demodulating means using said third and fourth estimated-interference signals. - View Dependent Claims (33, 34, 35, 36, 37)
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Specification