Voice transmission method and apparatus in duplex radio system

• US 5,355,363 A
• Filed: 03/08/1993
• Issued: 10/11/1994
• Est. Priority Date: 03/09/1992
• Status: Expired due to Fees

• Current Assignee: Hitachi Kokusai Electric Incorporated (Hitachi, Ltd.), Tohoku Electric Power Company Incorporated
• Original Assignee: Fuji-Tekku Kabushiki Kaisha, Hitachi Denshi Kabushiki Kaisha, Tohoko Electric Power Co., Inc.
• Inventors: Takahashi, Katsumi, Kurokawa, Takashi, Isawa, Kiyoyuki, Suzuki, Kenichi, Sekiguchi, Nobuo, Ohira, Sakari, Sumi, Fujio, Suzuka, Kazuo
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US08/027,479
• Time in Patent Office: 582 Days
• Field of Search: 370/24, 370/29, 370/109, 455/73, 455/79, 455/84, 455/86, 455/87
• US Class Current: 370/280
• CPC Class Codes: H04B 1/56 with provision for simultaneous communication in two directions
• CPC Class Codes: H04B 1/662 using a time/frequency relationship, e.g. time compression or expansion

Abstract

A voice transmission method and apparatus in a duplex radio system are disclosed in which a voice signal to be transmitted in a constant period of time is subjected to 1/N time compression, N being a numeral not smaller than 2.0. The time-compressed voice signal is supplied to a transmitter as a modulating signal and a transmitting operation is performed by the transmitter in synchronism with a period of time when the modulating signal is inputted to the transmitter. A receiving operation of receiving a time-compressed and modulated signal transmitted from the transmitter to demodulate it is performed by a receiver in a period of time other than the period of time when the transmitting operation is performed. A demodulated signal is subjected to N-ple time expansion to obtain a reproduced receive voice signal, and both the transmitting operation and the receiving operation are repeated at the constant period of time. In the voice transmission method and apparatus, a predetermined band of a signal corresponding to said signal to be transmitted, which is in a voice band, is extracted with a predetermined band width. The extracted signal is shifted to any band which is in the voice band and is other than the extracted band. A signal corresponding to the shifted signal is supplied to the transmitter as the modulating signal.

Claims

1. A voice transmission method in a duplex radio system having a transmitter and a receiver and using one carrier frequency in which a voice signal to be transmitted in a constant period of time is subjected to 1/N time compression, N being a numeral equal to or greater than 2.0, the time-compressed voice signal is supplied to said transmitter as a modulating signal, a transmitting operation is performed by said transmitter in synchronism with a period of time when said signal is inputted to said transmitter, a receiving operation of receiving a time-compressed and modulated signal transmitted from an external transmitter to demodulate it is performed by said receiver in a period of time other than said period of time when said transmitting operation is performed, a demodulated signal is subjected to N-ple time expansion to obtain a reproduced receive voice signal, and both said transmitting operation and said receiving operation are repeated at said constant period of time, the method comprising the steps of:

extracting with a predetermined bandwidth a predetermined band of a signal corresponding to said signal to be transmitted which is in a voice band; and

shifting the extracted signal to the predetermined band which is in said voice band and is other than the extracted band and supplying a signal corresponding to the shifted signal to said transmitter as said signal to be modulated.

2. A voice transmission method according to claim 1, wherein said extracted predetermined width is a band between 0.6 kHz and substantially 1.9 kHz of the voice band.

3. A voice transmission apparatus in a duplex radio system having a transmitter and a receiver and using one carrier frequency in which a voice signal to be transmitted in a constant period of time is subjected to 1/N time compression, N being a numeral equal to or greater than 2.0, the time-compressed voice signal is supplied to said transmitter as a modulating signal, a transmitting operation is performed by said transmitter in synchronism with a period of time when said signal to be modulated is inputted to said transmitter, a receiving operation of receiving a time-compressed and modulated signal transmitted from an external transmitter to demodulate it is performed by said receiver in a period of time other than said period of time when said transmitting operation is performed, a demodulated signal is subjected to N-ple time expansion to obtain a reproduced receive voice signal, and both said transmitting operation and said receiving operation are repeated at said constant period of time, the apparatus comprising:

means for extracting with a predetermined bandwidth a predetermined band of said signal to be transmitted which is in a voice band and shifting the extracted signal to the predetermined band which is in said voice band and is other than the extracted band;

means for subjecting the shifted signal to said time compression to obtain said modulating signal and supplying the obtained signal to said transmitter;

means for subjecting a demodulated signal of said receiver to said time expansion; and

means for shifting the band of the time-compressed signal to said extracted band to obtain said reproduced receive voice signal.

4. A voice transmission apparatus in a duplex radio system using one carrier frequency according to claim 3, wherein said means for obtaining said modulating signal obtains said signal by imposing band limitation by a low-pass filter on the signal subjected to said time compression.

5. A voice transmission apparatus in a duplex radio system according to claim 3, wherein said extracted predetermined width is a band between 0.6 kHz and substantially 1.9 kHz of the voice band.

7. A voice transmission apparatus in a duplex radio system using one carrier frequency according to claim 5, wherein said means for obtaining said modulating signal obtains said signal by imposing band limitation by a low-pass filter on the signal shifted by said extracting means.

8. A voice transmission apparatus in a duplex radio system according to claims 5, wherein said extracted predetermined width is a band between 0.6 kHz and substantially 1.9 kHz of the voice band.

6. A voice transmission apparatus in a duplex radio system having a transmitter and a receiver and using one carrier frequency in which a voice signal to be transmitted in a constant period of time is subjected to 1/N time compression, N being a numeral equal to or greater than 2.0, the time-compressed voice signal is supplied to a transmitter as a modulating signal, a transmitting operation is performed by said transmitter in synchronism with a period of time when said signal is inputted to said transmitter, a receiving operation of receiving a time-compressed and modulated signal transmitted from an external transmitter to demodulate it is performed by said receiver in said period of time other than said period of time when said transmitting operation is performed, a demodulated signal is subjected to N-ple time expansion to obtain a reproduced receive voice signal, and both said transmitting operation and said receiving operation are repeated at said constant period of time, the apparatus comprising:

means for subjecting said voice signal to be transmitted to said time compression;

means for extracting with a predetermined bandwidth a predetermined band of the time-compressed signal which is in a band of N times of a voice band of said voice signal to be transmitted and shifting the extracted signal to the predetermined band which is in said band of N times and is other than the extracted band;

means for obtaining a signal from the shifted signal and supplying said signal to said transmitter;

means for shifting the band of a demodulated signal of said receiver to said extracted band; and

means for subjecting the signal shifted by said shifting means to said time expansion to obtain said reproduced receive voice signal.

9. A voice transmission apparatus in a duplex radio system having a transmitter and a receiver and using one carrier frequency in which a voice signal to be transmitted in a constant period of time is subjected to 1/N time compression, N being a numeral equal to or greater than 2.0, the time-compressed voice signal is supplied to said transmitter as a modulating signal, a transmitting operation is performed by said transmitter in synchronism with a period of time when said signal is inputted to said transmitter, a receiving operation of receiving a time-compressed and modulated signal transmitted from an external transmitter to demodulate it is performed by said receiver in a period of time other than said period of time when said transmitting operation is performed, a demodulated signal is subjected to N-ple time expansion to obtain a reproduced receive voice signal, and both said transmitting operation and said receiving operation are repeated at said constant period of time, the apparatus comprising:

a first modulator for amplitude-modulating a subcarrier signal by said voice signal to be transmitted, said subcarrier having any frequency in a voice band of said voice signal to be transmitted;

first signal extracting means for extracting a lower sideband of the modulated signal from said first modulator;

means for subjecting the extracted sideband to said time compression to obtain said modulating signal and supplying the signal to said transmitter;

means for subjecting a demodulated signal of said receiver to said time expansion;

a second modulator for amplitude-modulating a subcarrier signal having the same frequency as the first-mentioned subcarrier signal by the time-expanded signal; and

second signal extracting means for extracting a lower sideband of the modulated signal from said second modulator to obtain said reproduced receive voice signal.

10. A voice transmission method in a duplex radio system having a transmitter and a receiver and using one carrier frequency in which a voice signal to be transmitted in a constant period of time is subjected to 1/N time compression, N being a numeral equal to or greater than 2.0, the time-compressed voice signal is supplied to said transmitter as a modulating signal, a transmitting operation is performed by said transmitter in synchronism with a period of time when said signal is inputted to said transmitter, a receiving operation of receiving a time-compressed and modulated signal transmitted from an external transmitter to demodulate it is performed by said receiver in a period of time other than said period of time when said transmitting operation is performed, a demodulated signal is subjected to N-ple time expansion to obtain a reproduced receive voice signal, and both said transmitting operation and said receiving operation are repeated at said constant period of time, the method comprising the steps of:

extracting with a predetermined bandwidth a predetermined band of a signal corresponding to said signal to be transmitted which is in a voice band; and

shifting the extracted signal to the predetermined band which is in said voice band and supplying a signal corresponding to the shifted signal to said transmitter as said signal to be modulated.