JPH0888593A - Switching system for diversity reception - Google Patents

Abstract

PURPOSE: To provide a diversity reception switching system which simplifies the circuit constitution and doesn't repeat unnecessary switching operations by detecting the demodulated signal level by, using only the output of the antenna selected at present. CONSTITUTION: When a demodulated signal is not detected from an antenna 1a or 1b selected at present within a prescribed time, a control circuit 15 switches it to another antenna 1b or 1a. If a maximum output level is lower than a preliminarily determined reference value and is lower than the preceding detected maximum output level at the time of detecting the demodulated signal, the antenna 1a or 1b is switched. Thus, the demodulated signal level is compared with the reference value, and the antenna is not switched if the level is higher than the level measured in the preceding control step though being lower than the reference level, and therefore, diversity reception switching is possible with the reception circuit of one system. Consequently, the circuit constitution is simplified, and the antenna is switched only when switching is necessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity reception switching system used in, for example, a portable radio transceiver or the like.

[0002]

2. Description of the Related Art FIG. 4 is a diagram for explaining an example of a conventional diversity reception switching system of this type.
1a is an electric field antenna, 1b is a magnetic field antenna, and 2a and 2b.
Is a high frequency amplifier, 3a and 3b are frequency converters, 4a and 4
Reference numeral b is a demodulator, 5 is a level comparator, and 6 is a diversity switch.

Next, the operation will be described. A normal whip antenna is used as the electric field antenna 1a, and a loop antenna effective when the gain is decreased when used near the surface of the human body and when the gain is decreased due to radio wave interference caused by reflected waves, is used as the magnetic field antenna 1b, The level comparator 5 constantly monitors both demodulation outputs, and the diversity switch 6
By selecting and outputting the one with the higher demodulation output level, it is configured to maintain good reception quality even if the reception environment changes (for the characteristics of the above-mentioned antennas, refer to "Small Antennas", for example). 1987, RESEARCH
It is described in STUDIES PRESS LTD etc.). However, in the diversity reception switching system as shown in FIG.
Not only is it necessary to constantly monitor one demodulation output level, but it is also necessary to provide two series of high-frequency amplifiers, frequency modulators, and demodulators.

Further, Japanese Unexamined Patent Publication No. 6-13944 “Diversity receiver” discloses a device in which a switching circuit is placed immediately after the antenna so that the receiving circuits after that are made into one series. In this case, both output levels are constantly detected while switching by the switching device and compared by the level comparator, and the antenna with the higher received output level is selected.

[0005]

As described above, the conventional diversity reception switching system is configured to constantly monitor a plurality of reception output levels and select the one having a higher reception output level. There is a problem in that it becomes complicated and unnecessary switching operations are frequently performed.

The present invention has been made to solve the above problems, and an object thereof is to provide a diversity reception switching system in which the circuit configuration is simplified and unnecessary switching operations are not complicatedly performed. .

[0007]

A diversity reception switching system according to the present invention detects a demodulation signal from a currently selected antenna within a predetermined time in a diversity reception switching system in which a reception antenna is switched on the basis of a demodulation signal level. When it is not possible, or when the output level of the demodulated signal detected within a predetermined time is lower than a predetermined reference value and lower than the previously detected output level, it is provided with means for switching to another antenna. .

[0008]

In the conventional switching system of this type, the demodulation signal levels from the respective antennas are constantly detected and compared with each other to select the antenna having the highest demodulation signal level. The operation becomes complicated. According to the present invention, with the above-described configuration, the demodulated signal level can be detected only by the demodulated signal from the currently selected antenna, and the antenna can be switched only when the antenna needs to be switched.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a device configuration example for explaining an embodiment of a diversity reception switching system of the present invention. In the figure, 1a is an electric field antenna, 1b is a magnetic field antenna, 11 is a diversity switch, and 12 is A high frequency amplifier, 13 is a frequency converter, and 14 is a demodulator, which are almost the same as the respective devices shown in FIG. Also, 1
A control circuit 5 is composed of a detector for detecting the reception output level of the demodulated signal, a comparator for comparing the detected reception output level with a predetermined reference value, and a control device such as a memory and a microcomputer. (Not shown). 2 is a flowchart showing the operation of the control circuit 15, and FIG. 3 is a flowchart of a subroutine showing the operation of the determination process shown in steps S2 and S4 of FIG.

Next, the operation will be described. For example, when the antenna 1a is selected in step S1 of FIG. 2, the determination process is performed in the next step S2. In this determination process, as shown in FIG. 3, the control circuit 15 determines whether or not the demodulated signal is detected within a predetermined time (step S10), and if the demodulated signal is not detected within the predetermined time. , Step out of the subroutine, step S2 of FIG.
To step S3, but when a demodulated signal is detected,
It is judged whether or not the maximum output level is higher than a predetermined reference value (step S11).
repeat. The reference value is stored in the memory and may be variable.

If the maximum output level of the demodulated signal is smaller than the reference value in step S11, step S12
Then, the level is stored in the memory, and it is judged whether or not it is higher than the previous detection level stored in the memory. If it is higher than the previous detection level, it is not necessary to switch the antenna ( If it is not possible to obtain a better quality even if the switching is performed), steps S10 to S12 are repeated. However, if the level is lower than the previous level, the process exits from the subroutine shown in FIG. 3 to switch the antenna, and step S2 in FIG. To S3.

As described above, in the diversity reception switching system of the present invention, the demodulated signal level is compared with the reference value, and even if the level is lower than the reference value, if it is higher than the level measured in the previous control step. Since the antennas are not switched, the required diversity reception switching can be performed with a single receiver circuit, and the operation of simultaneously detecting and comparing the demodulated signal levels from each antenna unlike the conventional device is unnecessary. Therefore, unnecessary antenna switching is not frequently performed.

In the above embodiment, the maximum output level within the predetermined time is used for measuring the demodulated signal level, but the average output level within the predetermined time may be compared with the reference value. In the above embodiment, the reception switching system of the device having the whip antenna 1a and the loop antenna 1b has been described, but other electric field antennas or magnetic field antennas may be used, and the number of antennas that can be switched is 3 or more. Is also good.

[0014]

As described above, according to the present invention, the high frequency amplifier, the frequency converter, and the demodulator are integrated into one system, and it is not necessary to constantly detect and compare the demodulation level of each antenna. Therefore, it is possible to always obtain a good radio wave reception state, simplify the receiving device, and reduce the price.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a device configuration for explaining an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the control circuit shown in FIG.

FIG. 3 is a flowchart showing an operation of a determination process shown in FIG.

FIG. 4 is a block diagram showing an example of a conventional device configuration.

[Explanation of symbols]

 1a Electric field antenna 1b Magnetic field antenna 11 Diversity switcher 12 High frequency amplifier 13 Frequency converter 14 Demodulator 15 Control circuit

Claims (3)

[Claims] 1. In a diversity reception switching system in which a receiving antenna is switched on the basis of a demodulated signal level, when the demodulated signal cannot be detected within a predetermined time from the currently selected antenna, or the maximum of the demodulated signals detected within the predetermined time is reached. When the output level is lower than a predetermined reference value and lower than the previously detected maximum output level, a diversity reception switching system is provided with means for switching to another antenna. 2. In a diversity reception switching system in which a receiving antenna is switched based on a demodulated signal level, when the demodulated signal cannot be detected within a predetermined time from the currently selected antenna, or an average of the demodulated signals detected within the predetermined time. A diversity reception switching system comprising means for switching to another antenna when the output level is lower than a predetermined reference value and lower than the previously detected average output level. 3. The diversity reception switching system according to claim 1, further comprising means for varying the reference value.