Hybrid digital radio-relay system
First Claim
1. A hybrid digital radio-relay system comprising:
- a transmitting terminal station having a plurality of transmitter sub-units for respective sub-system signals, each sub-unit having a modulator for modulating a signal, and a transmitter for converting frequency of the modulated signal to a radio frequency and providing high transmitting power, and a band splitting filter for combining radio signals of all the sub-units to transmit from an antenna,at least one repeater station having a band splitting filter for separating a received signal into a plurality of sub-system signals applied to respective repeater subunits, each having a first frequency converter for converting a received radio frequency to IF frequency, an auto-gain controller having an amplifier, and a second frequency converter for converting amplified IF frequency to radio frequency and providing high transmitting power, and another band splitting filter for combining radio signals of all the sub-units to transmit from an antenna,a receiving terminal station having a band splitting filter for separating a received signal into sub-system signals applied to respective receiver sub-units, each having a receiver for converting a received radio frequency into IF frequency which is subject to detection, a demodulator for demodulating the received signal, and an equalizer coupled with an output of said demodulator for equalizing waveform distortion of the received signal during propagation between said transmitting terminal station and said receiving terminal station, whereinsaid at least one repeater station is a non-regenerative repeater station which does not regenerate a digital symbol of the modulated signal,said non-regenerative repeater station has a common reference oscillator which supplies a local frequency to both said first frequency converter of all the sub-units and said second frequency converter of all the sub-units with in-phase condition, andsaid second frequency converter receives a same heterodyne, selected from an upper heterodyne and a lower heterodyne, as that of said first frequency converter, so that interference caused by an adjacent sub-system signal, which is leaked into the sub-system signal, is compensated by the equalizer in the receiving terminal station.
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Accused Products
Abstract
A digital radio-relay system has a transmitting terminal station, at least one repeater station a receiving terminal station, a non-regenerative repeater station which does not regenerate a digital signal in order to simplify and reduce cost of the system, while keeping excellent signal quality in transmission. Each repeater station has a plurality of sub-units relating to respective sub-system signals each having a plurality of carriers so that the frequency spectrum of each sub-system signal is allocated on a frequency axis based upon a frequency division multiplex system. A repeater station having a first frequency converter to convert a received radio frequency to IF frequency, bandpass filters for deriving one of the carriers in each sub-system signal, amplifiers to amplify the derived carrier on IF band stage, and a second frequency converter to convert the IF frequency to radio frequency, has a common reference oscillator which generates a reference frequency which is a common divisor of all the local frequencies for all the radio frequencies of all the sub-system signals. Only one of an upper and lower heterodyne signals is taken in all the frequency conversions, so that distortion in each relay section is added in-phase. Leaked noise caused by the bandpass filters is added to original carrier in-phase. All the distortion thus added in the relay sections can be compensated by a transversal equalizer in the receiving terminal station. Therefore, excellent signal quality is obtained although a simple non-regenerative repeater station is used.
17 Citations
12 Claims
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1. A hybrid digital radio-relay system comprising:
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a transmitting terminal station having a plurality of transmitter sub-units for respective sub-system signals, each sub-unit having a modulator for modulating a signal, and a transmitter for converting frequency of the modulated signal to a radio frequency and providing high transmitting power, and a band splitting filter for combining radio signals of all the sub-units to transmit from an antenna, at least one repeater station having a band splitting filter for separating a received signal into a plurality of sub-system signals applied to respective repeater subunits, each having a first frequency converter for converting a received radio frequency to IF frequency, an auto-gain controller having an amplifier, and a second frequency converter for converting amplified IF frequency to radio frequency and providing high transmitting power, and another band splitting filter for combining radio signals of all the sub-units to transmit from an antenna, a receiving terminal station having a band splitting filter for separating a received signal into sub-system signals applied to respective receiver sub-units, each having a receiver for converting a received radio frequency into IF frequency which is subject to detection, a demodulator for demodulating the received signal, and an equalizer coupled with an output of said demodulator for equalizing waveform distortion of the received signal during propagation between said transmitting terminal station and said receiving terminal station, wherein said at least one repeater station is a non-regenerative repeater station which does not regenerate a digital symbol of the modulated signal, said non-regenerative repeater station has a common reference oscillator which supplies a local frequency to both said first frequency converter of all the sub-units and said second frequency converter of all the sub-units with in-phase condition, and said second frequency converter receives a same heterodyne, selected from an upper heterodyne and a lower heterodyne, as that of said first frequency converter, so that interference caused by an adjacent sub-system signal, which is leaked into the sub-system signal, is compensated by the equalizer in the receiving terminal station. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A hybrid digital radio-relay system comprising:
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a transmitting terminal station having a plurality of modulators for modulating input signals, means for multiplexing modulated signals, and means for converting said modulated signals to radio frequency, at least one repeater station having a first frequency converter for converting a received radio frequency to IF frequency, means for de-multiplexing signals to each carrier, auto-gain controllers having amplifiers for amplifying each carrier at IF band, means for multiplexing each amplified carrier, and a second frequency converter for converting IF frequency to radio frequency, a receiving terminal station having means for converting a received radio frequency to IF frequency, means for de-multiplexing signals to each carrier, means for demodulating each received signal, and equalizers for equalizing each demodulated signal, wherein said at least one of the repeater stations is a non-regenerative repeater station which does not regenerate a digital symbol of a signal, said non-regenerative repeater station has a common reference oscillator which supplies a local frequency to both said first frequency converter and said second frequency converter with in-phase condition, and said second frequency converter receives a same heterodyne, selected from an upper heterodyne and a lower heterodyne, as that of said first frequency converter.
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Specification