JPH0410817A - Antenna switching diversity receiver - Google Patents

Abstract

PURPOSE:To obtain an effective reception characteristic by selecting a selection criterion by which so much dynamic range of a level detector is not called for and applying the changeover control of the antenna according to the selection criterion. CONSTITUTION:A reception level (envelope level) is detected from an amplified output of an intermediate frequency amplifier led to a level detector 24 and a detected output is inputted to an antenna changeover control circuit 25. The antenna changeover control circuit 25 receives the reception level detected by the level detector 24, three different predetermined levels L1-L3 and a predetermined time T1 and uses an antenna selection discriminator 29 to select an antenna in response to the reception level and to output an antenna selection signal and a mute operating signal. Thus, the level detector operating over a wide dynamic range is not required by applying changeover control of the antennas 1, 2 based on plural antenna selection criteria in response to the reception level and an effective equipment characteristic is obtained over the wide dynamic range.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a mobile communication system using a frequency division multiple access (FDMA) system, in which frequency modulation (hereinafter referred to as FM) transmitted via a high-speed fading circuit is used. , reception of analog modulated signals such as phase modulation (hereinafter referred to as PM), or reception of FM and P signals with high-speed fading in mobile devices.
The present invention relates to an antenna switching diversity receiving device for receiving analog radio broadcasts such as M.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional antenna switching diversity receiving apparatus disclosed in, for example, Japanese Patent Publication No. 64-2301. In the figure, 1 is a first antenna attached to a mobile object such as a car in order to receive analog modulated signals such as FM and PM transmitted via a high-speed fading line, and 2 is a similar second antenna. It's an antenna. Reference numeral 3 denotes a changeover switch for selecting the antenna output of either the first antenna 1 or the second antenna 2, and this may be composed of, for example, a semiconductor switch.

4 is a receiver that receives the antenna output selected by this switch 3, and 5 is a speaker that amplifies and outputs the received output from the receiver 4.

Reference numeral 6 denotes a level detection terminal that outputs a signal at a level corresponding to the high frequency input of the receiver 4.

7 is a diversity reception controller for performing diversity reception based on the signal from the level detection terminal 6. In the diversity reception controller 7, a timing circuit 8 receives a signal from the level detection terminal 6 and controls each section. Reference numeral 9 denotes a first sample and hold circuit, which switches the reception level of the first antenna 1 with a switch 3. This is for storing via the receiver 4.

Similarly, 10 is a second sample and hold circuit for storing the reception level of the second antenna 2. A comparison circuit 11 compares the level stored in the first sample and hold circuit 9 and the level stored in the second sample and hold circuit 10. Reference numeral 12 denotes a drive circuit that controls switching of the changeover switch 3 based on the comparison output of the comparison circuit 11. A priority circuit 13 controls the drive circuit 12 by obtaining information from the first sample and hold circuit.

Next, the operation will be explained. In the diversity receiving device shown in FIG. 3, when the reception level of the first antenna 1 stored in the first sample and hold circuit 9 is high, the priority circuit 13 operates and fixes the drive circuit 12 to the first antenna 1. , when the reception level is low, the priority circuit 13 is canceled,
It operates so as to repeat the operation of measuring the reception levels of the first antenna 1 and the second antenna 2, respectively, and demodulating the reception with the high-level antenna output at regular intervals.

Here, the configuration of the priority circuit 13 is shown in FIG. In the figure, 14 is an integrating circuit that integrates the signal from the first sample and hold circuit 9, 15 is an electric field level correction circuit that corrects the integrated output of this integrating circuit 14, and 16 is an electric field level correction circuit of this electric field level correction circuit 15. This is a priority comparison circuit that compares the correction output and the signal from the first sample and hold circuit 9.

In this priority circuit 13, the reception level stored in the first sample and hold circuit 9 is input to an integration circuit 14, and is also directly input to one input terminal of a priority comparison circuit 16. The integrating circuit 14 performs 7 aging while the car is running;
It does not respond to electric field fluctuations caused by multipath signals, and integrates the input signal so that it becomes the average electric field in the area where the vehicle is traveling. Furthermore, the integrated output is applied to the electric field level correction circuit 15, and the slope of the ratio of the antenna input electric field to the output of the electric field level correction circuit is made gentle.

FIG. 5 shows this situation. However, the data of this conventional example has a negative polarity in which the output of the level detection terminal 6 of the receiver 4 decreases when the reception level increases, so the input electric field level and the first sample hold level have opposite polarity. It has become.

In the figure, the output of the first sample and hold circuit 9 is shown by a solid line, and the output E8 of the electric field level correction circuit 15 is shown by a dotted line.

Therefore, in the priority comparison circuit 16, there is no need to compare the levels of this dotted line and the solid line, and the priority circuit 13
In the range of 70μ■, the drive circuit 12 is operated so as to cause the changeover switch 3 to select the first antenna 1.

In addition, in the range of weak electric field O to 30 μV, the priority circuit 13 issues a release signal, and the timing circuit 8 outputs a release signal for a certain period of time (approximately 2
0 μsec) The reception level of the first antenna 1 is stored in the first sample and hold circuit 9. Thereafter, the timing circuit 8 switches the selector switch 3 to the second antenna 2 via the drive circuit 12 so that the receiver 4 receives the signal. Then, the timing circuit 8 stores the reception level in the second sample and hold circuit 10.

The comparison circuit 11 compares the levels of the first and second sample and hold circuits 9 and 10 stored in this way,
The result is given to the drive circuit 12 so that the antenna output with the higher reception level is selectively received. The drive circuit 12 operates in conjunction with the timing circuit 8 to set the changeover switch 3 to the first
When the reception level of antenna 1 is high, the connection is returned to the first antenna 1 side, and the second antenna 2
When the reception level is high, a control signal is given so that the second antenna 2 receives the signal as it is. Then, it continues to receive data for about 7 msec, and repeats the above operation.
Select antenna processing. However, during operation, if the reception level of the first antenna 1 becomes a strong electric field in the priority comparison circuit 16, the priority circuit 13 is activated again and the drive circuit 12 is switched to the changeover switch 3 to switch the first antenna to the first antenna. Operate to select 1.

In addition, even in strong electric fields, fading occurs while the car is running.
There are level fluctuations due to multipath, etc. This information is included in the output of the first sample and hold circuit 9, but is not included in the output of the electric field level correction circuit 15 due to the integral action. When the level of the first antenna 1 suddenly decreases due to fading, multi-noise, etc., it acts on the drive circuit 12 to perform time-division diversity reception.

6 is a waveform diagram for explaining the operation of the priority circuit 13 configured as shown in FIG. 4, and (a) shows the output EO of the level detection terminal 6 and the output Es of the electric field level correction circuit 15 of FIG. (b) shows the output of the priority comparison circuit 16, that is, the output of the priority circuit 13. In the figure, the portion where time-division diversity reception is performed only when the reception level is lowered for both Es and Es is indicated by diagonal lines.

Additionally, when performing diversity reception in a weak electric field, when external noise, white Gaussian noise, etc. becomes equal to the reception level, the comparator circuit 11 randomly malfunctions and switches the antenna, which can be solved. In order to
In this conventional example, a weak electric field priority circuit is added to the output of the first sample and hold circuit 8 that stores the reception level of the first antenna 1, and as shown in FIG. A measure is taken to forcibly create a deviation in the weak electric field region between the sample and hold circuits 10 to fix the antenna and prevent malfunctions due to noise.

[Problem to be solved by the invention]

Since the conventional antenna switching diversity receiving device is configured as described above, activation and release of the priority circuit 13 depend on the magnitude of the instantaneous received electric field (sample and hold circuit output) of the first antenna 1 and the average received electric field. Therefore, a level detector with a wide dynamic range is required. Either a level detector that allows for characteristic deterioration is used, or an antenna switching diversity reception that uses a level detector that allows for higher cost. Furthermore, since the priority circuit 13 is designed to operate over a wide dynamic range, the correction of the electric field level correction circuit 15 (reducing the slope of the graph in FIG. 5) also operates over a wide dynamic range. However, if the characteristics of the Lebel detector change over time, it is either necessary to change the correction amount of the electric field level correction circuit 15, or it is necessary to change the correction amount of the electric field level correction circuit 15. Although the design is such that the slope of the ratio of the antenna input electric field to the output of the electric field level correction circuit is gentle, and when the average received electric field is high, the priority circuit 13 is difficult to be canceled even if the reception level becomes somewhat low. Since the operation and release of the antenna are determined by the relative relationship between the average received electric field and the antenna received electric field, the drive circuit 12 may operate depending on the reception level, and the reception characteristics may deteriorate due to antenna switching noise. There were issues such as ``existence''.

This invention was made to solve the above-mentioned problems, and does not require a level detector that operates over a wide dynamic range, and can easily realize effective reception characteristics over a wide dynamic range. The purpose of this invention is to obtain a diversity receiving device that can

[Means to solve the problem]

The antenna switching diversity receiving device according to the present invention includes a level detector that detects the reception level according to the high frequency input of the receiver, and a predetermined selection standard that is selected from a plurality of selection criteria prepared according to the reception level. A selection criterion is selected by comparing the level with the detection output of the level detector, and the antenna selection signal to the selector switch that selects the output of one of the multiple antennas is based on the selected selection criterion. This is provided with an antenna switching control circuit that generates antenna switching based on the antenna.

[Effect]

The antenna switching control circuit according to the present invention takes advantage of the fact that the diversity reception effect associated with antenna switching differs depending on the input level, and uses the fact that the diversity reception effect due to antenna switching differs depending on the input level. You can maximize the expected effects in emergency situations,
In addition, by selecting selection criteria that do not require a large dynamic range of the level detector and controlling antenna switching according to each selection criteria, a wide dynamic range can be achieved. To realize an antenna switching diversity receiving device that does not require a level detector and can obtain effective reception characteristics over a wide dynamic range.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1.2 is a first antenna and a second antenna that are equivalent to the conventional ones, and 17 is a first antenna that removes unnecessary components outside the band from the antenna output of the first antenna 1.
A reception filter 18 is a second reception filter that removes unnecessary components outside the antenna output band of the second antenna 2.

3 is a changeover switch for selecting either the antenna output from which unnecessary components have been removed by the first reception filter 17 or the second reception filter 18; 4 is a changeover switch for selecting the antenna output selected by the changeover switch 3; This is a receiver that amplifies and demodulates.

Further, in this receiver 4, 19 is a high frequency amplifier that amplifies the antenna output selected by the changeover switch 3, 20 is a frequency mixer that mixes a local oscillation signal with the amplified output of this high frequency amplifier 19, and 21 is a local oscillator that generates the local oscillation signal. 22 is an intermediate frequency amplifier that amplifies the mixed output of the frequency mixer 20;
is a demodulator that demodulates the amplified output of this intermediate frequency amplifier 22. Reference numeral 5 denotes a speaker for amplifying and outputting the signal amplified and Φ demodulated by the receiver 4 configured as described above.

Reference numeral 24 denotes a level detector that detects a reception level corresponding to a high frequency input from the amplified output of the intermediate frequency amplifier 22 of the receiver 4. 25 is an antenna switching control circuit that generates an antenna selection signal to the changeover switch 3 based on the reception level detected by the level detector 24.

In this antenna switching control circuit 25, 26 is a first memory that stores the reception level detected by the level detector 24 when it is based on the antenna output of the first antenna 1; is a second memory that stores the received level when it is based on the antenna output of the second antenna 2. 28 is the cut 9
It is switched by the antenna selection signal to the switching switch 3,
The detection output of the level detector 24 is transferred to the first memory 26 and the second memory 26.
This is a switch for selecting which memory 27 to store the data in. 29 is externally provided with three predetermined levels L1 to L3 and a predetermined time T1, and the first and second memo! The reception level from J26.27 and the reception level input directly through the switch 28 are set to the predetermined levels L1 to L1.
While comparing with L3, depending on the reception level, the default time T
This antenna selection determination device generates an antenna selection signal to the selector switch 3, taking I into account, and also generates a mute (squelch) activation signal to the demodulator 23 when necessary.

Next, the operation will be explained. The antenna output of the first antenna 1 has unnecessary components outside the band removed by a first reception filter 17, and is input to the changeover switch 3. Similarly, the antenna output of the second antenna 2 is filtered by the second reception filter 18, which removes unnecessary components outside the υ band.
It is input to the switching switch 3. The changeover switch 3 selects one of the antennas according to the antenna selection signal given to the antenna switching control circuit 25 and inputs it to the receiver 4.

In the receiver 4, it is amplified by a high frequency amplifier 19, and the amplified output is input to a frequency mixer 20. The frequency mixer 20 frequency-mixes this amplified output and the local oscillation signal supplied from the local oscillator 21, converts the frequency into an intermediate frequency band, and selectively amplifies it in the intermediate frequency amplifier 22.

The intermediate frequency amplifier 22 outputs amplified outputs to the demodulator 23 and level detector 24, respectively. These two amplified outputs are basically the same, but if the intermediate frequency amplifier 22 includes a limiter amplification function that keeps the envelope of the received signal constant, the level detector 24
The output to is the received intermediate frequency signal before being amplified by the limiter.

The amplified output of the intermediate frequency amplifier 22 guided to the demodulator 23 is demodulated and becomes an audio signal, which is amplified and outputted via the speaker 5.

On the other hand, an intermediate frequency amplifier 22 guided to a level detector 24
The received level (envelope level) of the amplified output is detected,
The detection output is input to the antenna switching control circuit 25. The antenna switching control circuit 25 is connected to this level detector 2.
4 detected reception levels and 3 different predetermined levels L
1-L3. and a predetermined time T1 as input, the antenna selection determiner 29 selects an antenna according to the reception level, and outputs an antenna selection signal and a mute operation signal.

Next, the operation of this antenna switching control circuit 25 will be explained. In this invention, the reception level is divided into four regions based on the reception level and the corresponding reception state, and diversity reception is performed by applying selection criteria that can maximize the expected effect in each region. There is. Table 1 shows an example of areas divided by reception level and the corresponding reception status.

The three predetermined levels L1 to L3 given to the antenna selection determiner 29 correspond to the boundaries of the respective regions.

Table 1 In Table 1, region 1 is the region where the detection level of the level detector 24 is equal to or higher than the predetermined level L1, and this level is a level that provides a good reception condition. In this area, the reception level is such that click noise does not occur, and considering the antenna switching noise, it is preferable to continue receiving the signal as it is rather than switching to an antenna with a higher reception level. This is the area of

In area 2, the detection level of the level detector 24 is the default level L.
This is a region where the value is 2 or more and less than L1. In this region, click noise occurs relatively frequently, and even if antenna switching noise is tolerated, reception level is such that reception with better characteristics can be expected if antenna switching diversity reception is performed.

Region 3 is a region in which the detection level of the level detector 24 is equal to or higher than the predetermined level 3 and lower than L2. In this region, the received electric field is at a low level, and even if you switch antennas based on level comparison, there is a high possibility that malfunctions will occur due to noise. This is a reception level region where it is desirable to use a diversity receiving tube with relatively low switching frequency from the viewpoint of preventing malfunctions and suppressing antenna switching noise.

In area 4, the detection level of the level detector 24 is the default level L.
The area is less than 3. In this area, the signal is suppressed by noise and cannot be received, and it is desirable to get out of this area as soon as possible, even if reception is to continue.

Based on the above, we prepared three types of antenna selection criteria according to regions 1 to 3, and in region 4, we repeated the reception level comparison.
It can be seen that high-quality diversity reception characteristics can be achieved over a wide dynamic range by performing antenna switching control for transition to other areas. In this invention, from this viewpoint, three selection criteria are prepared.

Note that the default level L1. L2. Since the specific reception level of L3 varies depending on the modulation index of FM or PM and the demodulation method, it is not specified in the present invention, but the reception state of the reproduced audio of the applied system is the reception state shown in Table 1. It is sufficient if the default setting corresponds to .

FIG. 2 shows a state transition diagram showing the antenna selection diversity reception state, the three level comparison states, and the state transition relationship between each state based on the selection criteria of these three cases. In the figure, A-F represent the states, (101) to (1
11) represents a state transition. Further, A, C, and E each indicate diversity reception modes based on three selection criteria, and B, D, and F indicate level comparison modes (transient states). That is, A, C, and E correspond to diversity reception modes corresponding to the reception states of regions 1 to 3, respectively.

Furthermore, F corresponds to a continuous level comparison (alternate observation) mode for extracting data from region 4. And B, D
is a transient state, and corresponds to the receiving level comparison mode of each receiving antenna for determining the diversity receiving mode to which the next transition will be made.

Antenna selection criteria of A, C, and E above, and B.

Table 2 shows how to compare the levels of D and F.

Table 2 Furthermore, Table 3 shows the transition conditions from the previous state and the antenna selection method after the state transition regarding the state transitions corresponding to the numbers (101) to (111).

Table 3 In Table 3, the default time T1 in the transition condition of (105)
may be approximately the fading correlation time or several times that, and is not particularly limited in this invention. This condition is given to perform more effective diversity reception, taking into consideration that the reception level of the antenna that is not currently receiving reception may exceed the reception level of the antenna that is currently receiving reception. It is.

In addition, since reception is not possible when the level observation mode F is in the state, the antenna switching control circuit 25
3 to prevent unnecessary noise from being generated from the speaker.

In the above embodiment, two antennas are used, but the number of antennas may be three or more.

Further, in the above embodiment, a case has been described in which the first memory and the second memory are separated from the functions of the antenna selection determiner, but these functions may be provided together in the antenna selection determiner. , the same effect as the above embodiment is achieved.

〔Effect of the invention〕

As described above, according to the present invention, antenna switching is controlled using a plurality of antenna selection criteria depending on the reception level by utilizing the fact that the effect of diversity reception accompanying antenna switching differs depending on the input level. Since the level detector is configured to operate accurately only in region 2, in other regions it only needs to be able to determine whether the level is above the predetermined level L1 or below L3, and it can operate over a wide dynamic range. The present invention has the advantage that an antenna switching diversity receiving apparatus can be obtained which eliminates the need for a level detector and which can realize effective reception characteristics over a wide dynamic range.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an antenna switching diversity receiving device according to an embodiment of the present invention, FIG. 2 is a state transition diagram for explaining its operation, and FIG. 3 is a block diagram showing a conventional antenna switching diversity receiving device. 4 is a block diagram showing the configuration of the priority circuit, FIG. 5 is a characteristic diagram for explaining the operation of this priority circuit, and FIGS. 6 and 7 are operation of a conventional antenna switching diversity receiving device. FIG. 2 is a waveform diagram and a characteristic diagram for explaining. 1 is the antenna (first antenna), 2 is the antenna (second antenna)
antenna), 3 is a changeover switch, 4 is a receiver, 2
4 is a level detector, and 25 is an antenna cut/switch control circuit. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] a plurality of antennas that receive analog modulated signals transmitted via a high-speed fading line; a changeover switch that selects an antenna output of any one of the plurality of antennas according to an antenna selection signal; a receiver that amplifies and demodulates the antenna output; a level detector that detects the reception level according to the high frequency input of the receiver; An antenna switching control circuit that selects the selection criteria by comparing the level with the detection output of the level detector, generates the antenna selection signal based on the selected selection criteria, and outputs it to the changeover switch. Antenna switching diversity receiving device.