JPH0232824B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a channel search method in a personal radio device that makes it possible to efficiently search for a channel with less interference when searching for a channel. It is.

[Prior Art] As shown in FIG. 1, in a conventional personal radio device, when a call signal is input from an input terminal 1 at the time of making a call, a changeover switch circuit 3 is set to a threshold value by a signal from a control circuit 2. Switching to the contact 5 side of the low resistor 4 for judgment, a threshold value judgment is made and an empty channel is searched.
When an empty channel is found, the group number and empty channel data are transmitted to the other party via the transmitter 6 and antenna 7. A signal from the other party is received by an antenna 8, and further transmitted to a high frequency amplification circuit 9 and a mixing circuit 1.
0, is sent to the intermediate frequency amplifier circuit 11, the detection circuit 12, the amplifier circuit 13, the filter circuit 14, the detection circuit 15, and the level detection circuit 16, and when the received signal level is above a certain level, the detection signal from the level detection circuit 16 is The signal is input to the control circuit 2. If a match is found with the other party, the other party is also set to the corresponding empty channel. When the channel is set to an empty channel and a call operation is started, a signal from the control circuit 2 switches to the contact 18 side of the squelch judgment resistor 17, and also switches the mute circuit 19, so that the audio signal passes through the audio amplifier circuit 20 and is sent to the speaker. 21, and mutual calls are made.

[Problems to be Solved by the Invention] However, in such conventional personal radios, channel searches were performed only on the basis of a fixed level, which caused various problems. For example, when the determination level is set to 0 dBμ, an electric field of 0 dBμ or less is determined to be an empty channel, so even if a radio wave of 0 dBμ or less exists, that channel will be set. However, in many cases, the channel is in use and cannot be used, and a problem arises in that a usable channel cannot be found unless a call is made and the channel check is repeated many times. In other words, if this determination level was set too low, an empty channel could not be found and a call could not be made.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems.The present invention is made to solve the above-mentioned problems. In a personal radio device that controls a mute circuit with a control signal from a control circuit to enable mutual communication when the level is higher than the level of the threshold judgment section in the level detection circuit and the mutual empty channels match, In this method, the empty channel detection level can be switched in multiple stages by a switching control signal from the control circuit, and the empty channel is searched for by sequentially switching stepwise from a low level to a high level.

[Example] Hereinafter, an example of the present invention will be described based on FIG. 2.

Antenna 8, high frequency amplification circuit 9, mixing circuit 1
0, intermediate frequency amplification circuit 11, detection circuit 12, mute circuit 19, audio amplification circuit 20, speaker 2
1. The amplifier circuit 13, filter circuit 14, detection circuit 15, level detection circuit 16, transmitter 6, and antenna 7 are the same as the conventional configuration shown in FIG.

A feature of the present invention is that it is equipped with a changeover switch circuit for setting the empty channel detection level that can be switched in multiple stages, so that the empty channel search is performed at a low level initially, and if it is not found, it is automatically sequentially searched. The purpose is to switch to a higher level and search for empty channels.

In order to achieve this method, the level detection circuit 16 is connected to a semi-fixed resistor 23 for setting the empty channel detection level via a changeover switch circuit 22.
24 are connected. Among these, one semi-fixed resistor 23 is for low level, and the other semi-fixed resistor 24 is for high level. Further, the changeover switch circuit 22 is configured to be changed over by a changeover control signal X from the control circuit 2a. Note that if two or more switching control signals X are used and three or more semi-fixed resistors are used, the detection level can be switched to three or more levels.

The operation of the above configuration will be explained.

In FIG. 3, when stations B and C are communicating and station C is transmitting, it is assumed that station A searches for an empty channel.

First, the selector switch circuit 22 is switched to the low level semi-fixed resistor 23 side by the switching control signal X from the control circuit 2a. At this time, the electric field area becomes wide as indicated by L in FIG. Therefore, it catches that the C station is transmitting, finds out that it cannot communicate with the C station, and moves on to the next channel. In this way, empty channels are searched for by going around at a low level. In the case of FIG. 3, station D is searched as an empty channel, and communication with station D becomes possible. If an empty channel is not found after one cycle, a switching control signal X is output from the control circuit 2a to switch the switching circuit 22 to the high level semi-fixed resistor 24 side. Then, the electric field area becomes the third
The area becomes narrow as indicated by H in the figure, and the search is performed in this state. At this time, stations C and D cannot communicate with each other during a low level search, but when the search level becomes high, they can transmit as an empty channel.

[Effects of the Invention] Since the present invention uses the method described above, first, set the lowest -5 dBμ and go around the channels, and if an empty channel below that level is found, set it to that empty channel and repeat. Can communicate in good condition. Also, when the station is crowded, you can raise the search level in stages and receive radio waves even if some interference is ignored. In other words, it is possible to efficiently search for a channel with less interference.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional personal radio device, FIG. 2 is a block diagram of a personal radio device used in the method of the present invention, and FIG. 3 is an explanatory diagram of the communication status of each station. 1... Calling signal input terminal, 2a... Control circuit,
16... Level detection circuit, 19... Mute circuit, 22... Selector switch circuit, 23... Semi-fixed resistor for low level, 24... Semi-fixed resistor for high level.

Claims (1)

[Claims] 1. A signal for calling, capturing, or recalling is transmitted by a transmitter, and the level of the received signal from the other party is equal to or higher than the level of the threshold judgment section in the level detection circuit, and the mutual empty channels match. In a personal radio device that enables mutual communication by controlling a mute circuit with a control signal from a control circuit, the empty channel detection level can be switched in multiple stages by a switching control signal from the control circuit, A channel search method in a personal radio device, characterized in that an empty channel is searched for by sequentially switching from a low level to a high level. 2. A channel search method in a personal radio device according to claim 1, wherein the low level side is set to approximately -5 dBμ, and the high level side is set to approximately +5 dBμ, and switching is performed stepwise within this range.