Hybrid digital radio-relay system

Details Hybrid digital radio-relay system Hybrid digital radio-relay system

1993-10-08

1995-12-26

Chin, Stephen

Pulse or digital communications

Repeaters

455 131, 455 23, 370 75, 375349, H04B 7165, H04B 717, H04J 110

Patent

active

054794439

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.

REFERENCES:
patent: 4132952 (1979-01-01), Hange et al.
patent: 4606054 (1986-08-01), Amitay et al.
patent: 4742530 (1988-05-01), Kawai
patent: 4789993 (1988-12-01), Ryu
"Development of NNI Digital Radio", Murase et al., NTT Review, vol. 1, No. 3, Sep. 1989, pp. 77-83.
"Performance of a Transversal Equalizer for Self-Interference Passing Adjacent Channels", Kagami et al., JP Electronics, Information and Communication Institute, B-II, vol. J 75-B-II, No. 8, Aug. 1992, p. 508-514.
"Coherent Non-Regenerative Repeater Digital Microwave Radio System Field Test", Watanabe et al., IEEE Communications Society, IEEE Global Telecommunications Conference, Dec. 6-9, 1992, pp. 1846-1850.

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