Pulse or digital communications – Transceivers
Patent
1991-03-28
1996-02-06
Chin, Stephen
Pulse or digital communications
Transceivers
375240, 375364, 370 24, 370109, 381 34, H04B 138, H04L 514
Patent
active
054901677
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a duplex voice communication radio transmitter-receiver for transmission and reception of voice message with the use of radio waves having a single frequency or two adjacent frequencies.
It is known in common duplex operating radio communication that radio waves to be used should be of two sufficiently separated frequencies for stable and consistent transmission.
However, the duplex operation becomes possible with lower but acceptable effectiveness through the use of one frequency or two closely separated frequencies. FIG. 20 shows the schematic arrangement of "a narrow-band voice communication transmitter-receiver capable of simultaneously transmitting and receiving voice information with the use of radio waves of a single frequency".
As illustrated in FIG. 20, a couple of narrow-band voice transmitter-receiver B1 and B2 are identical in the construction employing one carrier frequency f for transmission and reception. Each transmitter-receiver contains a transmitter T, a receiver R, a control switch SW for selecting and activating either the transmitter or the receiver at intervals of a given time, a sync generator SYCGEN for controlling the intervals and synchronizing the control switch with a control switch of the other station, a loud-speaker SP, a microphone MIC, and an antenna coupler AT. Also, denoted by ANT is an antenna. (In FIG. 20, like components in the transmitter-receivers B1 and B2 are identified by the subscript numerals 1 and 2 respectively.)
The two transmitter-receivers are controlled with timing by their respective sync generators SYCGEN for transmission and reception in the alternate relationship with each other.
FIG. 21 illustrates a time chart showing the exchange of voice signals between the two narrow-band voice communication transmitter-receivers B1 and B2 portrayed in FIG. 20. Without regard to the subscript numerals, represented by VM is a transmitting voice signal, SWT is a shift pulse for transmission and reception generated by the control switch SW, and VSP is a received voice signal. Also, T is a transmission period of time, R is a reception period, and T0 is a cycle of transmission and reception. (Hence, the reciprocal of T0 or a repeat frequency is denoted by F0.)
In the operation between the two transmitter-receivers, the transmitting voice signal VM is sampled at intervals of time so that about a half of the same is received as the received voice signal VSP. This results in intermittent transmission of a signal from one station to the other. Fortunately, a voice sound of speech is redundant and the transmission of speaking sounds becomes possible if the repeat frequency F0 is appropriately predetermined. The received voice sounds are yet unfavorable to human ears and somewhat less audible.
For improvement, a method has been introduced in which the blank portions C0 of a signal resulting from time sampling are compensated. However, the result is still unsatisfactory and can hardly be appropriate for practical use.
Also, another type of duplex operating radio transmitter-receiver has been developed in which the transmitter delivers intermittent radio signals on a modulated carrier through time dividing an original voice signal and compressing a talk duration and the receiver, upon receiving and detecting the transmitting radio signals, demodulates them to the original voice signal by time expanding and rebinding the intermittent signals in synchronism with the action of the transmitter. The synchronizing action is controlled by one of the two transmitter-receivers which serves as a "master station" and is arranged to determine the time allocation of time divided segments of a modulated signal during transmission so that the other transmitter-receiver which serves as a "slave station" can be actuated in synchronism.
This transmitter-receiver will now be explained in more detail referring to the drawings.
FIG. 10 shows an arrangement of the transmitter-receiver, as compared to the arrangement shown in FIG. 20. Th
REFERENCES:
patent: 4893339 (1990-01-01), Bright et al.
patent: 5159596 (1992-10-01), Itoh
patent: 5355363 (1994-10-01), Takahashi et al.
patent: 5396484 (1995-03-01), Itoh
Ishikawa Kouichi
Nakabayashi Susumu
Ohira Sakari
Sumi Fujio
Bocure Tesfaldet
Chin Stephen
Fuji-Tekku Kabushiki Kaisha
Touhoku-Denryoku Kabushiki Kaisha
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