JPS6262628A - Receiver for mobile body satellite communication - Google Patents

Abstract

PURPOSE:To prevent disabled tracking to a satellite by applying the output of the 1st frequency synthesizer tuned to a talking channel at the reception of the talking channel to a frequency conversion section and applying the output of the 2nd frequency synthesizer tuned to a control channel to the frequency conversion section at carrier interruption due to voice activation. CONSTITUTION:The signal of the 1st frequency synthesizer is inputted to a frequency converting section by a changeover switch 2 at the standby normally and a control channel is received by a demodulation section 4. When a call is generated and the state transits to talking, the switch 2 is changed over by a control signal from a control section 5, a signal of the 2nd frequency synthesizer is inputted to the frequency conversion section and the talking channel is received by the demodulation section 4. The changeover switch 2 selects the 1st frequency synthesizer to receive the control channel every time the carrier of the talking channel is interrupted due to voice activation to input the reception section always to the demodulation section 4 thereby detecting the reception level or the line quality.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a mobile satellite communication system that applies 5CPC voice activation (a communication method that transmits radio waves only during a call), and is used to control communication between a control channel and a call. The present invention relates to a mobile satellite communication receiving device that shares a demodulator with a channel.

(Prior Art) In mobile satellite communication, in order to maintain the line, it is necessary to perform satellite tracking when the mobile body is turning. For this reason,
Conventionally, tracking has been performed using tracking beacon waves and information on the reception level of normal signal waves.

In particular, in order to miniaturize mobile stations, it is desirable to use signal wave reception levels or line quality that can be configured only with a communication receiver without providing a tracking receiver. Also, generally S
In the CPC system, communication is performed by setting a communication channel for each mobile station using a control channel. In a system that uses voice activation for effective use of satellite power, when receiving a communication channel, a mobile station that uses the signal wave reception level or line quality, which can be configured only with the communication receiver described above, as tracking information uses voice activation. The drawback was that if the carrier was cut off due to a giant, it would be impossible to track the line and the line could not be maintained.

The present invention aims to improve this drawback.

(Means for Solving the Problems) A feature of the present invention for achieving the above object is that the control channel is transmitted between the mobile station that tracks the satellite and the mobile station according to the line quality or reception level of the control channel broadcast from the satellite. In a mobile satellite communication system that sets a communication channel using SCPC voice activation depending on the channel, a single frequency converter and demodulator are provided, and when receiving a communication channel, a first frequency synthesizer tuned to the communication channel is provided. supplying the output of to the frequency conversion section,
When the carrier is cut off due to voice activation, the output of the second frequency synthesizer tuned to the control channel is supplied to the frequency converter.

The demodulator is located in a mobile satellite communication receiver to which a received signal is always input.

(Function) According to the present invention, when voice activation is applied when receiving a communication channel in a mobile station that performs antenna tracking using the reception level of signal waves or line quality,
Even when the communication channel carrier is disconnected, two frequency synthesizers are prepared, one for the communication channel and one for the control channel.
By switching to the control channel that is always being transmitted and receiving it, it is possible to continuously track the antenna without interruption of the signal wave reception level or line quality information.
It becomes possible to maintain the line.

(Example) FIG. 1 shows an example of the present invention. The first frequency synthesizer IA is always tuned to the transmitted control channel, and the second frequency synthesizer IB is tuned to the speech channel. Normally, during standby, the changeover switch 2 inputs the signal from the first frequency synthesizer to the frequency converter 3, and the demodulator 4 receives the control channel. When a call occurs and transition to a conversation occurs, the changeover switch 2 is switched by a control signal from the control unit 5, and the signal from the second frequency synthesizer is input to the frequency conversion unit, and the signal from the second frequency synthesizer is input to the frequency conversion unit, and the signal from the second frequency synthesizer is input to the frequency conversion unit.
A speech channel is received. By switching to the first frequency synthesizer using the selector switch 2 and receiving the control channel each time the communication channel is carrier-disconnected due to voice activation, the received signal is always input to the demodulator 4, and the reception level or line quality can be adjusted. This information allows the antenna tracking control unit 6 to continuously track the satellite and maintain one line.

A case in which a digital modulation method is used will be specifically described below.

In this invention, the carrier is disconnected by voice activation when voice is not being transmitted, and during that time, the mobile station continuously receives signals by switching the synthesizer and receiving the constantly transmitted control channel. .

To achieve this, it is necessary for the mobile station to know the timing for switching the synthesizer. When audio is encoded and transmitted digitally, it is transmitted in a frame configuration in which a synchronization word is added to an information signal, as shown in FIG. In the control channel, the information signals are line control signals such as a calling signal, an incoming call signal, and a communication channel designation signal. In a communication channel, the information signal is normally a coded voice signal, but here, as shown in FIG. 2, in addition to this, a low-speed control signal is also transmitted simultaneously. When applying voice activation,
A control signal added to this audio signal transmits information on carrier disconnection of the communication channel, and is used as a switching timing signal. Further, when the carrier of the communication channel is interrupted, the control channel is being received, but when voice transmission is to be restarted, the ID number of the target mobile station and information on restarting voice transmission are transmitted on the control channel. Upon receiving this, the mobile station switches its synthesizer and receives the communication channel again. These controls, as well as normal line controls such as call origination and call reception, are performed by the control unit 5.

The above is an example of using a digital modulation method.
In the case of an analog modulation method, the present invention can be realized in the same manner as described above by using a call control signal transmission method using a voice lower band in one call channel.

(Effects of the Invention) As explained above, according to the present invention, even when voice activation is applied, the received signal is always input to the demodulator, so the line quality can be detected, and the beacon signal for satellite tracking can be detected. It is possible to perform antenna tracking control without using a mobile station, it is not necessary to have a beacon wave receiving device in the mobile station and it can be made smaller, and there is no need to transmit beacon waves from the satellite, so satellite power can be used effectively. can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an example of a frame structure. 3; Frequency converter, 4; Demodulator,

Claims (1)

[Claims] A mobile device that sets up a communication channel using SCPC voice activation using the control channel between a mobile station that tracks a satellite according to the line quality or reception level of a control channel broadcast from the satellite. In the satellite communication system, a single frequency converter and a demodulator are provided, and when receiving a communication channel, the output of a first frequency synthesizer tuned to the communication channel is supplied to the frequency converter, and carrier disconnection is prevented by voice activation. A mobile satellite communication receiving device, characterized in that an output of a second frequency synthesizer tuned to a control channel is supplied to the frequency conversion unit, and a received signal is always input to the demodulation unit.