JPH08149059A - Diversity control circuit - Google Patents

Abstract

PURPOSE: To provide a diversity control circuit which can deal with both after- detection and antenna switching diversity systems, can automatically identify the diversity system to be adopted, and also automatically stop the supply of power to the unnecessary circuits to evade the unnecessary power consumption when the antenna switching diversity system is adopted. CONSTITUTION: The signal levels of the signal input terminals 5 and 6 provided on the preceding stages of both demodulator circuits 7 and 9 are detected by the signal level detecting circuits 8 and 10. Then the threshold level comparators 18 and 19 check whether those detected signal levels exceed or decrease the prescribed threshold value in the prescribed frequency. Based on these comparison results 21 and 22 of both comparators 18 and 19, a system deciding circuit 20 decides the diversity system to be adopted. If an antenna switching diversity system is adopted, the supply of power is cut to the unnecessary one of both circuits 7 and 8 and circuits 8 and 10 respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity control circuit capable of supporting both the diversity system after detection and the antenna switching diversity system.

[0002]

2. Description of the Related Art When a transmission wave is received at a reception point via a plurality of propagation paths or the reception point moves, the propagation conditions change and the intensities of the waves cancel each other out due to the phase of the radio waves. The received signal level fluctuates due to mutual strengthening. This phenomenon is called fading. Diversity reception is effective as a measure against such fading.
For diversity reception, multiple antennas (usually 2
When the radio wave reception condition deteriorates due to fading, an antenna with good conditions is selected and received.

[0003] Diversity has a small correlation with each other, that is, there is a small probability that the line quality will deteriorate at the same time.
This is a technique for reducing the influence of fading by preparing one or more receiving systems and selecting or combining the outputs. It is generally said that it is effective to set the antenna spacing in diversity reception to about half the carrier wavelength.

Conventionally, the diversity system includes a post-detection diversity system (also referred to as an antenna selection diversity system) and an antenna switching diversity system.
In the post-detection diversity method, one receiver is connected to each of the receiving antennas, the antenna that produces the maximum received signal strength is selected, and the received signal from the antenna is detected and output. Has become. On the other hand, in the antenna switching diversity method, only one receiver is provided, and when the received signal strength of the antenna in use falls below a preset level, or during the effective reception period. , The antenna is switched to another antenna that is estimated to have a higher received signal strength, and the received signal from the switched antenna is detected and output.

FIG. 3 is a block diagram showing an example of the configuration of a conventional receiving circuit adopting the diversity system after detection. Three
Reference numerals 1 and 32 are reception antennas, and 33 and 34 are intermediate frequency conversion circuits for converting the frequency of the antenna reception signal. Further, 35 and 37 are demodulation circuits for demodulating the reception signal converted to the intermediate frequency, and 36 and 38 are signal level detection circuits for measuring the signal level of the demodulated antenna reception signal.

Further, 39 is a signal level detecting circuit 36 and 3
Reference numeral 40 is a level comparison circuit for relatively comparing the signal levels measured in 8, and reference numeral 40 is a digital multiplexer for selecting one of the signals output from the demodulation circuits 35 and 37 according to the comparison result of the level comparison circuit 39. Then, the received data output from the demodulation circuit with the higher signal level is selected by the digital multiplexer 40 and output to the subsequent baseband signal processing unit.

Regarding the circuit block configuration on the right side of the intermediate frequency conversion circuits 33 and 34, the LS
Configured as I. The digital multiplexer 40 is used when handling a digital signal, and an analog switch is used when handling an analog signal. Further, the signal level detection circuits 36 and 38 are also called a signal strength measuring device, and are usually composed of an amplifier, an envelope detector and a low pass filter,
When handling digital signals, the signal level is measured for each burst.

According to the above circuit configuration, the antennas 31 and 3
If the cross-correlation of 2 is small, even if the reception signal of one antenna fades out (that is, the signal level with respect to the target signal decreases), the reception signal of the other antenna usually fades out. In many cases, the reception quality after antenna selection is significantly improved by always selecting an antenna with a high received signal strength. On the other hand, since two receiving circuits are required, it is more disadvantageous than the antenna switching diversity system described below in terms of downsizing and cost reduction of equipment.

FIG. 4 is a block diagram showing a configuration example of a conventional receiving circuit adopting the antenna switching diversity system. Here, first, for example, a signal for selecting the reception antenna 41 is output from the antenna switching control circuit 48, and the reception signal by the reception antenna 41 is selected by the analog switch 43. Then, after the frequency conversion of the selected reception signal is performed by the intermediate frequency conversion circuit 44, the level of the reception signal demodulated by the signal level detection circuit 46 is measured and held.

Then, a signal for selecting the other receiving antenna 42 is output from the antenna switching control circuit 48 to the analog switch 43, and the receiving period (slot) is set.
The period other than is used to detect whether or not the receiving antenna 42 is in a good receiving state. Then, the received signal is frequency-converted by the intermediate frequency conversion circuit 44, the level of the received signal demodulated by the signal level detection circuit 46 is measured, and then the signal level and the received signal level by the previously held receiving antenna 41 are measured. And the level comparison circuit 47.

In this way, the diversity reception is executed by switching the analog switch 43 so as to select the receiving antenna with the higher signal level during the period of receiving the effective received signal. In addition,
The circuit block configuration on the right side of the intermediate frequency conversion circuit 44 is an LSI.
In addition, there is an example of the antenna switching diversity method currently adopted in a digital wireless telephone using the 800 MHz band.

According to the above circuit configuration, the antennas 41 and 4 are
If the cross-correlation of 2 is small, even if the reception signal of one antenna in use fades out, the reception signal of the other antenna often does not fade out. By switching to the antenna, the reception quality after switching is improved.

In this case, as compared with the post-detection diversity method shown in FIG.
This is advantageous in terms of device miniaturization and cost reduction. However, on the other hand, in terms of diversity improvement effect,
It does not match the above-mentioned diversity method after detection. This is because in the diversity system after detection, the receiving antenna with the higher signal level is always selected and received.
In the antenna switching diversity method, in order to determine which receiving antenna to switch to, the reception state of the radio waves transmitted from other stations rather than the opposite station is detected using the period other than the reception period (slot). In addition, since it takes a predetermined time to switch the antenna, it is not possible to cope with the signal level fluctuation during that time.

In the post-detection diversity method, the antenna itself is not switched, but a better received signal from the antenna is selected, whereas in the antenna switching diversity method, the antenna itself is switched. Therefore, when the switching frequently occurs, a so-called hunting phenomenon may occur, and the amplitude and phase at the time of reception may jump, or the waveform distortion may not be improved.

As a result, in the antenna switching diversity method, the bit error rate (BER) of the received data tends to be higher than that in the post-detection diversity method. Especially, when the 800 MHz band is used, Although it can be managed by correcting the error correction code applied to, the error correction cannot be applied when the 1.5 GHz band is used. Therefore, at present, in the 1.5 GHz band,
After detection, the diversity method is used.

[0016]

As described above, there are two diversity systems as a diversity system after detection and an antenna switching diversity system, which are used in various mobile communication fields by utilizing their respective advantages. There is. Particularly in the field of mobile phones and the like, it is important to miniaturize the circuit configuration, and for that reason, circuit elements are being integrated into LSI as much as possible. In this case, since the common circuit is configured as an LSI, the number of components can be reduced, so that the LSI circuit is very effective in dealing with the manufacture of various types of communication devices.

Regarding the above-mentioned two diversity systems,
Since there is a common circuit, it is possible to make it an LSI. In that case, in order to have a circuit configuration that can be applied to any of the systems, it is basically necessary to have a circuit configuration compatible with the diversity system after detection, that is, a configuration in which two receiving systems are provided. When the antenna switching diversity system is adopted, only one of the receiving systems is operated and used.

Therefore, when adopting such a circuit configuration, it is necessary to supply an identification signal indicating which diversity method is to be adopted from the outside of the LSI. In addition, when the antenna switching diversity method is adopted, the other one receiving system is completely unnecessary. Therefore, unless some control is performed from the outside of the LSI to prevent unnecessary current consumption, the battery life is reduced. It can also speed up.

The present invention is compatible with both post-detection diversity and antenna switching diversity, and automatically recognizes the diversity method adopted.
When the antenna switching diversity method is adopted, power supply to unnecessary circuits is automatically stopped,
An object of the present invention is to provide a diversity control circuit capable of preventing unnecessary power consumption.

[0020]

In order to achieve the above-mentioned object, the invention according to the first aspect of the present invention provides a diversity control circuit capable of supporting both antenna switching diversity and post-detection diversity. Of the first and second demodulation circuits, and the first and second demodulation circuits provided for the first and second demodulation circuits, respectively, for detecting the respective signal levels after detection. A signal level detecting circuit, a first demodulating circuit and a first signal level detecting circuit, and a first and a second power source for supplying power to the second demodulating circuit and the second signal level detecting circuit, respectively. First and second determinations are made as to whether or not the signal levels detected by the second two power supply means and the first and second signal level detection circuits are equal to or higher than a predetermined threshold level a predetermined number of times. Signal level format Means, and based on the judgment results of the first and second signal level judging means, the diversity method judging means for judging which diversity method is adopted, and the diversity method judging means for antenna switching diversity. And a control means for controlling the power supply operation of the unnecessary one of the first or second power supply means when the system is decided to be adopted. It is characterized by being.

In the invention according to the second aspect, the diversity method determining means and the first and second signal level determining means both detect the detected signal level a predetermined number of times and a predetermined threshold value. When it is determined that the detected signal level is exceeded, it is determined that the diversity method after detection is adopted, and either one of the first or second signal level determination means determines that the detected signal level is a predetermined number of times. It is characterized that it is determined that the antenna switching diversity method is adopted when it is determined to be equal to or less than the threshold value.

[0022]

According to the structure of the invention according to the above-mentioned claim 1, the present diversity control circuit is configured so as to be compatible with any of the diversity systems of antenna switching diversity and post-detection diversity. Therefore, the first and second demodulation circuits and the first and second two signal level detection circuits for detecting the respective signal levels after detection are provided for the two demodulation circuits, respectively. It is provided. Then, to the first demodulation circuit and the first signal level detection circuit, and to the second demodulation circuit and the second signal level detection circuit, respectively, a first power supply and a second power supply, respectively. By means of the means, power is supplied.

On the other hand, whether or not each signal level detected by the first and second signal level detection circuits by the first and second signal level determination means is a predetermined number of times or more and a predetermined threshold level or more. To be judged. Then, based on the judgment results of the first and second signal level judging means, the diversity method judging means judges which of the diversity methods is adopted.

Here, when the diversity method determining means determines that the antenna switching diversity method is adopted, control is performed for the unnecessary one of the first or second power supply means. By means
It is controlled to stop the power supply operation. Also,
According to the configuration of the invention according to claim 2, the diversity system determination means determines the diversity system as follows. That is, when both the first and second signal level determining means determine that the detected signal level exceeds a predetermined threshold value a predetermined number of times, it is determined that the diversity system after detection is adopted. . Further, when either one of the first or second signal level determination means determines that the detected signal level is a predetermined number of times or less than a predetermined threshold value, the antenna switching diversity method is adopted. It is supposed to be judged.

As a result, by using the present diversity control circuit, it is possible to cope with any of the diversity systems of antenna switching diversity and post-detection diversity. It is possible to automatically judge whether to adopt the method, and when it is judged that the antenna switching diversity method is to be adopted, the power supply to unnecessary circuits is automatically stopped. ing. Therefore, without controlling from the outside, as a circuit element,
It can be used as it is.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a diversity control circuit according to the present invention. This circuit configuration (which has an internal configuration surrounded by a broken line in the drawing) basically has a post-detection diversity system configuration, and is configured as an LSI. Here, an example in which the antenna switching diversity method is adopted is shown.

Reference numerals 1 and 2 are receiving antennas, and 3 is an analog switch for switching between those two antennas. Further, 4 is an intermediate frequency conversion circuit for converting a received signal from any of the receiving antennas to an intermediate frequency,
Reference numeral 5 is a terminal connected to the demodulation circuit 7. That is, since the antenna switching diversity method is adopted here, the input terminal 5 and the demodulation circuit 7 are connected. If the post-detection diversity method is adopted, the corresponding pre-stage circuits are connected to the input terminal 5 and the input terminal 6, respectively.

Reference numeral 7 is a demodulation circuit for demodulating the received signal converted into the intermediate frequency by the intermediate frequency conversion circuit 4,
A signal level detection circuit 8 detects the level of the received signal demodulated by the demodulation circuit 7. Further, 9 is a demodulation circuit for demodulating an input signal from the input terminal 6, and 10 is a signal level detection circuit for detecting the level of the reception signal demodulated by the demodulation circuit 9. Reference numeral 11 denotes a digital multiplexer that selects either of the output signals of the demodulation circuit 7 and the demodulation circuit 9, and outputs the selected reception signal to the baseband signal processing section.

Further, 12 is a power supply for supplying power to the demodulation circuit 7 and the signal level detection circuit 8, and 13 is a power switch thereof. Further, 14 is a power supply for supplying power to the demodulation circuit 9 and the signal level detection circuit 10, and 15 is a power switch thereof. Reference numeral 16 is a level comparison circuit for comparing the signal levels of the signal level detection circuit 8 and the signal level detection circuit 10 with each other. The level comparison circuit 16 generates a switching control signal for the digital multiplexer 11 and the antenna switching control circuit 17 Output the comparison result to. An antenna switching control circuit 17 controls switching of the analog switch 3 according to the comparison result of the level comparison circuit 16.

Reference numeral 18 is a threshold level comparison circuit for comparing the signal level output from the signal level detection circuit 8 with a predetermined threshold value, and 19 is a predetermined signal level output from the signal level detection circuit 10. It is a threshold level comparison circuit for comparing with a threshold. Further, 20 is based on the control signal 21 which is the comparison result from the threshold level comparison circuit 18 and the control signal 22 which is the comparison result from the threshold level comparison circuit 19 and whether the diversity system adopted is the antenna switching diversity system. Alternatively, it is a system determination circuit that determines whether the diversity system is the post-detection diversity system.

FIG. 2 is a flow chart showing the determination control of the diversity system in the diversity control circuit shown in FIG. First, the power switches 13 and 15 are turned on (S1), and the antenna switching signal from the antenna switching control circuit 17 to the analog switch 3 is output so as to select the receiving antenna 1 (S2). At this time, the signal received by the receiving antenna 1 is the analog switch 3
It is input to the intermediate frequency conversion circuit 4 via the, is frequency-converted there, and then is input to the demodulation circuit 7 from the input terminal 5.

Therefore, the signal level detecting circuit 8 measures the signal level of the input terminal 5 (S3). Further, the measured signal level is compared with a predetermined threshold value by the threshold level comparison circuit 18 to hold comparison data (S4). When the processing from step S3 to step S4 is repeated n times (Yes in S5), it is checked whether the number of times that the measured signal level is equal to or less than the threshold value is n times (S6). Then, if it is n times (Yes in S6), it is determined that the input terminal 5 has no carrier (NC, that is, no carrier) (S7). If No in step S6, that is, if the measured signal level exceeds the threshold value n times, it is determined that the input terminal 5 is used (S8).

Next, in the same manner, the signal level detection circuit 1
The signal level of the input terminal 6 is measured at 0 (S9). Further, the measured signal level is compared with the threshold level comparison circuit 1
The comparison data is held in step 9 by comparing with a predetermined threshold value (S11). When the processing from step S9 to step S10 is repeated n times (Yes in S11), the number of times that the measured signal level is equal to or less than the threshold value is n.
It is checked whether or not it was a turn (S12). Then, if it is n times (Yes in S12), it is determined that the input terminal 6 has no carrier (NC, that is, no carrier) (S13). If No in step S12, that is, if the measured signal level exceeds the threshold value n times, it is determined that the input terminal 6 is used (S14).

Next, when it is determined that the input terminal 5 is NC and the input terminal 6 is to be used (Yes in S15), the method determination circuit 20 switches the antenna. It is judged that the diversity system is adopted (S16), the digital multiplexer 11 is fixed to the signal system of the input terminal 6 (S17), and the power switch 13 is turned off (S18). After that, reception by the antenna switching diversity method is executed.

If the input terminal 6 is NC and it is determined that the input terminal 5 is to be used (Yes in S19), the method determination circuit 20 adopts the antenna switching diversity method. Judge (S2
0), the digital multiplexer 11 is fixed to the signal system of the input terminal 5 (S21), and the power switch 15 is turned off (S22). After that, reception by the antenna switching diversity method is executed.

When it is determined that both the input terminal 5 and the input terminal 6 are used (Yes in S23), the system determination circuit 20 determines that the post-detection diversity system is used (S24). ), Power switch 1
3 and the power switch 15 remain ON (S2)
5). After that, reception by the antenna switching diversity method is executed. In addition, in the case of No in step S23, it is determined that none of the input terminals are used, and thus the series of processes is ended.

Specifically, in the example shown in FIG. 1, since the input terminal 5 and the demodulation circuit 7 are connected, the level of the received signal input to the input terminal 5 is measured by the signal level detection circuit 8. To be done. Then, the measurement result is compared with a predetermined threshold value by the threshold level comparison circuit 18, but a control signal 21 that the received signal level is equal to or higher than the threshold value is output to the system determination circuit 20.

The level of the signal at the input terminal 6 is measured by the signal level detection circuit 10. Then, the measurement result is compared with a predetermined threshold value in the threshold level comparison circuit 19. In this case, since the input terminal 6 is an open terminal, the control signal 22 below the threshold value is sent to the system determination circuit 20. Is output. Therefore, the system determination circuit 2
0, the control signal 21 is greater than or equal to the threshold value, and the control signal 22
Is less than or equal to the threshold, it is determined that the antenna switching diversity method using the input terminal 5 is selected, and the power switch 15 is turned off. As a result, the power supply to the demodulation circuit 9 and the signal level detection circuit 10 supplied from the power supply 14 is stopped, no current flows in the signal system of the input terminal 6, and the power consumption is eliminated.

[0039]

As described above, according to the present invention, the diversity control circuit capable of supporting two types of diversity systems, that is, the diversity system after detection and the antenna switching diversity system is used.
When configured as SI, it is possible to automatically determine the diversity method without externally providing identification information as to which diversity method is adopted. Furthermore, when the antenna switching diversity method is adopted, unnecessary power consumption can be prevented by cutting off the power supply to the unnecessary demodulation circuit and signal level detection circuit.

Therefore, in manufacturing various types of communication equipment, the present diversity control circuit is provided as a very easy-to-use circuit element that can flexibly cope with any diversity method as it is. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a diversity control circuit according to the present invention.

FIG. 2 is a flowchart showing diversity system determination control in the diversity control circuit shown in FIG.

FIG. 3 is a block diagram showing an example of a configuration of a conventional receiving circuit adopting a post-detection diversity method.

FIG. 4 is a block diagram showing an example of a configuration of a conventional receiving circuit adopting a conventional antenna switching diversity method.

[Explanation of symbols]

 1, 2 Reception antenna 3 Analog switch 4 Intermediate frequency conversion circuit 5, 6 Input terminal 7, 9 Demodulation circuit 8, 10 Signal level detection circuit 11 Digital multiplexer 12 14 Power supply 13, 15 Power switch 16 Level comparison circuit 17 Antenna switching control circuit 18, 19 Threshold level comparison circuit

Claims (2)

[Claims] 1. A diversity control circuit capable of supporting both antenna switching diversity and post-detection diversity methods, including first and second demodulation circuits, and first and second demodulation circuits. Provided for each of the demodulation circuits of
First and second two signal level detection circuits for detecting the respective signal levels after detection, the first demodulation circuit and the first signal level detection circuit, and the second demodulation circuit and the second First and second power supply means for supplying power to each of the signal level detection circuits, and the respective signal levels detected by the first and second signal level detection circuits are set a predetermined number of times. The first and second signal level determining means for determining whether or not the threshold level is equal to or higher than the threshold level, and which of the diversity methods is used based on the determination results of the first and second signal level determining means. If the diversity method determining means for determining whether or not there is an antenna switching diversity method is adopted by the diversity method determining means, it is determined that the first or second power supply means A diversity control circuit, comprising: a control means for controlling the operation of stopping the power supply operation of the essential elements. 2. The diversity method determining means detects the detected signal level when both the first and second signal level determining means determine that the detected signal level exceeds a predetermined threshold value a predetermined number of times. If it is determined that the post-diversity method is adopted, and one of the first or second signal level determination means determines that the detected signal level is a predetermined number of times or less than a predetermined threshold value, 2. The diversity control circuit according to claim 1, wherein it is determined that the antenna switching diversity system is adopted.