JPH05206903A - Diversity device - Google Patents

Abstract

PURPOSE:To switch a receiving antenna when a reception level drops to a level less than a prescribed one during the reception of a reception slot. CONSTITUTION:A receiver 4 selects a desired radio wave, outputs an IF signal and generates a reception field level 12. The sample and hold circuits 6 and 7 in the reception levels of the respective antennas hold the reception levels of the respective antennas before the reception slot and a comparator 8 compares the reception levels. A control circuit 9 generates a branch control signal 11 so that branch larger than one level is selected into one frame by the output of the comparator 8 and a switch timing signal 13 generated immediately before the reception slot. A comparator 19 compares the reception field level 12 in the reception slot with reference voltage 20. When the reception field level in the reception slot becomes less than reference voltage 20, the reception level drop signal 21 is switched and the control circuit 9 switches the branch control signal 11 based on said switching and switches the receiving antenna.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity device used in a digital car telephone or the like.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional diversity apparatus. The diversity device is a device that measures reception levels of a plurality of antennas and selects an antenna having a large reception level, and since it can be configured with one receiver, it is mainly used for mobile phones and the like.

FIG. 2 shows the operation timing of diversity. Diversity in the TDMA (Time Division Multiplexing) method measures the reception levels of a plurality of antennas during a transmission slot and a reception slot, and determines the antenna to be selected during the reception slot.

In FIG. 3, reference numeral 1 denotes an antenna A, and 2
Indicates antenna B. There are multiple antennas. Reference numeral 3 denotes a switch, which switches between the radio waves received by the antenna 1 and the antenna 2. A receiver 4 selects a radio wave of a desired frequency and outputs an IF signal. It also outputs the received electric field level 12 of the radio wave of the desired frequency. A demodulator 5 detects the IF signal output from the receiver 4 and generates demodulated data. Reference numeral 6 is a sample-hold circuit for the reception level of the antenna 1, and 7 is a sample-hold circuit for the reception level of the antenna 2. Reference numerals 17 and 18 are control signals to the sample and hold circuits 6 and 7, which hold the reception level of each antenna before the reception slot. Reference numeral 8 denotes a comparator, which compares the reception levels held before the reception slot. The control circuit 9 determines the receiving antenna in the receiving slot from the comparison result of the comparator 8 and switches the branch control signal 11. 16 indicates an antenna switching signal, and during the level measurement time before the reception slot,
The control signals 14 and 15 are compulsorily switched to the antenna for measuring the reception level. In the reception slot, the branch control signal 11 determined from the reception level is output. In addition,
Reference numeral 10 is a switch, and 13 is a switching timing signal input to the control circuit 9.

Next, the operation will be described. In order to select an antenna with a high reception level in the reception slot, the sample hold circuits 6 and 7 hold the reception level of each antenna before the reception slot. The timing of holding is controlled by the control signals 17 and 18. At this time, the antenna switching signal 16 selects the antenna for holding the reception level by the control signal 15 and the control signal 14. Before the reception slot, the control circuit 9 outputs the branch control signal 11 so that the branch having the higher reception level is selected from the comparison result of the reception levels of the comparator 8 by the switching timing signal 13.

As described above, in the above-mentioned conventional diversity apparatus, the receiving level is switched to the antenna having a good receiving state for each frame by comparing the receiving levels of the plurality of antennas before the receiving slot and selecting the receiving antenna. You can

[0007]

However, in the above-mentioned conventional diversity apparatus, since only the reception level before the reception slot is judged, the reception level abruptly generated when the mobile unit moves at high speed in mobile communication. There is a problem that the antenna is not switched for such a drop and the reception is continued at a low reception level.

The present invention solves such a problem. When the reception level of the selected antenna becomes lower than a certain level during reception of the reception slot, the reception antenna is switched to a high reception level and an error occurs. It is an object of the present invention to provide an excellent diversity device capable of selecting an antenna with less generation of noise.

[0009]

In order to achieve the above object, the present invention provides a circuit for detecting a decrease in the reception level of an antenna being selected during a reception slot and a reception antenna based on the comparison result before the reception slot. A control circuit for switching the reception antenna from the level-decreasing signal during the reception slot is provided, and the reception antenna is switched when the reception level decreases during reception of the reception slot.

[0010]

According to the present invention, therefore, even if the reception level of the selected antenna drops sharply during the reception of the receiving slot, the circuit for detecting the drop in the reception level generates a signal for switching the antennas and controls it. Since the circuit switches the antenna, it is possible to suppress the occurrence of an error due to a decrease in the reception level.

[0011]

1 is a block diagram showing the configuration of an embodiment of the present invention.

In FIG. 1, 1 indicates an antenna A and 2
Indicates antenna B. There are multiple antennas. Reference numeral 3 is a switch for switching between the radio waves received by the antenna 1 and the antenna 2. 4 is a receiver for selecting a radio wave of a desired frequency and I
Output F signal. It also outputs the received electric field level 12 of the radio wave of the desired frequency. A demodulator 5 detects the IF signal output from the receiver 4 and generates demodulated data.
Reference numeral 6 is a sample-hold circuit for the reception level of the antenna 1, and 7 is a sample-hold circuit for the reception level of the antenna 2. Reference numerals 17 and 18 are control signals to the sample and hold circuits 6 and 7, which hold the reception level of each antenna before the reception slot. Reference numeral 8 denotes a comparator, which compares the reception levels held before the reception slot. Reference numeral 19 denotes a comparator, which compares the seismic electric field level 12 in the reception slot with the reference voltage 20 and outputs a reception level reduction signal 21. Before the receiving slot, the control circuit 9 uses the switching timing signal 13 to select a branch having a large receiving level from the comparison result of the receiving levels of the comparator 8 so that the branch control signal 1
1 is output. Further, during reception of the reception slot, the branch control signal 11 is switched when the reception level decrease signal 21 indicates a decrease in reception level. Reference numeral 16 denotes an antenna switching signal, and during the level measurement time before the reception slot,
The level measurement control signals 14 and 15 are compulsorily switched to the antenna for measuring the reception level. In the reception slot, the branch control signal 11 determined from the reception level is output.

Next, the operation will be described. An operation explanatory diagram is shown in FIG. In TDMA communication, transmission and reception are performed in a time-division manner, and are configured as reception slot-rest-transmission slot-rest-reception slot .... In the case of implementing diversity in which the receiver is configured by one system in TDMA communication, the reception levels of a plurality of antennas are compared between the transmission slot and the reception slot, and the antenna to be received in the reception slot is selected. When the reception electric field level 12 of the selected antenna drops below the reference voltage 20 during reception of the reception slot,
The comparator 19 switches the reception level lowering signal 21. The reference voltage 20 input to the comparator 19 is determined from the relationship between the error rate of the demodulated data and the received electric field level 12. The control circuit 9 switches the branch control signal 11 by the reception level lowering signal 21 and switches the receiving antenna.

By adding a circuit for detecting a decrease in the reception level during reception as described above, even if the reception level of the antenna determined before the reception slot suddenly decreases during reception, the reception antenna is instantaneously operated. Since it can be switched, it has the effect of minimizing the occurrence of errors.

In the above embodiment, assuming that there are two antennas, when switching is performed in the receiving slot, the antenna is switched to a non-selected antenna. However, when there are three or more antennas, the level is set before the receiving slot. From the comparison result,
Then select the antenna with the next highest level.

[0016]

As is apparent from the above-described embodiment, the present invention makes it possible to instantaneously turn on the receiving antenna in the diversity of TDMA communication even if the receiving level of the antenna determined before the receiving slot drops sharply during the receiving slot. Since it can be switched to, it has the effect of minimizing the occurrence of errors caused by a decrease in the reception level.

[Brief description of drawings]

FIG. 1 is a block diagram of a diversity device according to an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional diversity device.

[Explanation of symbols]

 1 antenna A 2 antenna B 3 switch (switching of receiving antenna) 4 receiver 5 demodulator 6, 7 sample hold circuit 8 comparator (comparing circuit) 9 control circuit 19 comparator (comparison result) 21 reception level drop signal

Claims (1)

[Claims] 1. A circuit for holding and comparing reception levels of a plurality of antennas before a reception slot in a TDMA data reception system including a plurality of antennas and one system of receiver-demodulator. It is equipped with a circuit that detects a reduction in the reception level of the antenna selected in the reception slot, and a control circuit that determines the reception antenna from the comparison result before the reception slot and switches the reception antenna from the level reduction signal during the reception slot. , A diversity device that switches the receiving antenna when the receiving level drops sharply and selects an antenna with a high receiving level and less error.