JPH0213974B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a diversity receiver, and particularly to a diversity receiver suitable for use in vehicle-mounted reception.

BACKGROUND ART As schematically shown in FIG. 1, in a conventional diversity receiver, received signals from a plurality of antennas 1 to 3 are selectively derived by a switching circuit 4 and sent to a receiving circuit 5.
is applied to. The field strength of this received output is detected by a field strength detection circuit 6, and a detection signal corresponding to the instantaneous value of the received signal is generated. This instantaneous value becomes the positive phase input of the comparator 8, and a signal corresponding to the moving average value from the moving average value detection circuit 7 is applied to its negative phase input. This comparison output is supplied to the counter 9 and becomes a count signal for the counter 9. A sequential circuit 10 is provided that determines the count contents of this counter and generates a switching signal according to the contents, and switches the selection of received signals of antennas 1 to 3 in this order every time the contents of the counter 9 change. It is now possible to generate a signal like this.

That is, for example, if the output of antenna 1 is currently selected, and the instantaneous value of the received signal falls below the moving average value, the output of comparator 8 will undergo a level transition, triggering counter 9, and the count contents will be A signal that changes from antenna 1 to antenna 2 is generated from sequential circuit 10.

FIG. 2 shows the antenna switching state of the device shown in FIG. 1. A solid line 11 shows the change in the reception level of antenna 1, a solid line 12 shows the change in the reception level of antenna 2, and a dashed line 13 shows the reception level of antenna 3. Each shows a level change. As shown in Figure 2, when switching from antenna 1 to antenna 2, antenna 2
If the level of antenna 1 is even lower than that of antenna 1, the switching to antenna 3 is not instantaneous, but the comparison operation between the two starts after the instantaneous value becomes larger than the moving average value. If the received signal is degraded, it will generate noise.

Summary of the Invention The present invention has been made to eliminate the drawbacks of the above-mentioned conventional products, and its purpose is to:
A diversity receiver that can suppress noise generation in any case by forcibly applying a signal whose instantaneous value is larger than a moving average value to the input of a comparator for a predetermined period when switching antennas. The goal is to provide the following.

The diversity receiver according to the present invention compares the moving average value and the instantaneous value of the received electric field strength using a comparison means, and selectively selects one of the reception outputs of the plurality of antennas according to the comparison result. the diversity receiver, in which a control signal is forcibly applied to the input of the comparison means such that the instantaneous value of the received signal is larger than the moving average value for a predetermined period of time after the antenna switching command signal is generated; It is characterized by having a means.

Examples Examples of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram of an embodiment of the present invention, and parts equivalent to those in FIG. 1 are designated by the same reference numerals. Connect the output of the comparator 8 to the trigger input of an MMV (monostable multivibrator) 20 via a unidirectional diode 21.
The output of the MMV 20 is used as the positive phase input of the comparator 8 via the diode 22. The other configurations are the same as those shown in FIG. 1, and their explanation will be omitted.

Suppose now that the instantaneous value of antenna 1 is below the moving average value and reaches point A in FIG. At this time, the comparator 8 compares the moving average value with the instantaneous value, and its output becomes a low level. In response to this transition of the comparison output, the contents of the counter 9 are incremented by 1, and a signal for switching from the antenna 1 to the antenna 2 is generated from the sequential circuit 10.

Therefore, we move from point A to point B in FIG. 2, where MMV 20 is triggered by the output transition of comparator 8 and generates a high level signal for a certain period of time.
Since this signal is forcibly applied to the positive phase input of comparator 8, the output of comparator 8 returns to its original state, and thereafter the instantaneous value of the received signal of antenna 2 is smaller than the moving average value. Since the process moves on to a comparison operation to determine that , a signal to be switched to the antenna 3 is generated from the sequential circuit 10 . Therefore, it moves instantaneously from point B to B' in FIG.

In the conventional method, the order of antenna switching is
Changes from A-B-C-D in the diagram to B-C as described above.
However, in the present invention, noise occurs between A-B-
Switching like B'-C'-D'-E'-F'-C-D,
An antenna with higher field strength can be selected.

Effects According to the present invention, the comparison operation of the comparator can be put into a standby state for a certain period of time each time the antenna is switched, so it is possible to always select an antenna with a higher electric field strength, resulting in good diversity reception. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of conventional diversity reception, FIG. 2 is a diagram illustrating diversity reception operation, and FIG. 3 is a block diagram of an embodiment of the present invention. Explanation of symbols of main parts, 1 to 3...Antenna,
4... Antenna switching circuit, 6... Received signal instantaneous value detection circuit, 7... Received signal moving average value detection circuit, 8... Comparator, 10... Sequential circuit.

[Claims]

1. A pager that is activated by dialing a telephone device, and a conversion means that is installed in close proximity to a conductor through which current flows in the pager while it is in operation, and that detects the magnetic flux generated by the conductor and converts it into an electrical signal; An incoming call detection device for a pager, comprising switching means for controlling the driving state of an electric device by detecting an electric signal from the converting means and opening or closing the page.