The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 26, 1995
Filed:
Oct. 08, 1993
Nippon Telegraph and Telephone Corporation, Tokyo, JP;
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.