JPS642301B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a vehicle-mounted diversity system configured to time-divisionally select an antenna with a higher reception level using one receiver so as to achieve the best diversity reception. In particular, in a strong electric field where good reception can be achieved without diversity reception, there is provided a diversity reception apparatus configured to preferentially select one antenna for reception and not perform time division. It is something to do.

2. Description of the Related Art Conventionally, a time division type diversity receiving apparatus as shown in FIG. 1 has been considered.

To explain this, 1 and 2 are a first antenna and a second antenna attached to an automobile or the like.
Reference numeral 3 denotes a changeover switch for guiding the antenna output of either the first antenna 1 or the second antenna 2 to the receiver 4, and this is constituted by, for example, a semiconductor switch. 5 is a speaker. 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. Reference numeral 7 denotes a diversity reception controller for performing diversity reception, which receives a signal from the level detection terminal 6 and controls each section by a timing circuit 8. Reference numeral 9 denotes a first sample and hold circuit for storing the reception level of the antenna 1 via the changeover switch 3 and the receiver 4. 10 is a second sample and hold circuit for storing the reception level of the 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 for driving a changeover switch 3 for selecting antenna 1 or antenna 2 in response to the result of comparison circuit 11.

The diversity receiving device shown in FIG. 1 uses a timing circuit 8 to switch between antennas 1 and 2 for a certain period of time (approximately 20 _μsec ) to receive signals, find the antenna with the higher reception level, and perform the reception for a certain period of time (about 20 μsec). approximately 7m _sec ), and time-divisionally for a certain period of time (approximately 7m sec).
This is a device that receives data by repeatedly selecting an antenna (20μ _sec ). That is, assuming that the antenna currently being received by the receiver 4 is the antenna 1, first, the timing circuit 8 stores the reception level of the antenna 1 in the first sample and hold circuit 9.
Thereafter, the timing circuit 8 switches the selector switch 3 to the 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. A comparison circuit 11 compares the stored levels of the first and second sample-and-hold circuits 9 and 10, and provides the result to a drive circuit 12 so as to select the antenna with a higher reception level.
The drive circuit 12 works in conjunction with the timing circuit 8 to set the changeover switch 3 so that when the reception level of antenna 1 is high, the connection is returned to antenna 1, and when the reception level of antenna 2 is high, the connection is returned to antenna 2. Give the control signal to be received by.
The processing time during this period is approximately 20 _μsec , which is extremely fast. Then, the signal is received for about 7 _msec , and the above operation is repeated to perform antenna selection processing. In this way, the system achieves good reception while time-divisionally selecting antennas with high reception levels.

However, since this conventional example performs antenna selection processing in a time-sharing manner, even when good reception is possible with a high reception level (strong electric field), antenna 1,
The antenna 2 is time-divisionally switched, which has the drawback that switching noise is generated from the speaker 5 via the receiver 4, although it is slight. Therefore, it is desirable to have a method that prevents switching in strong electric fields. One possible method is to compare the reception level with a reference voltage (fixed voltage) and stop the time-sharing antenna selection function in strong electric fields, but reception conditions from strong electric fields to weak electric fields vary depending on various land conditions. However, it is very difficult to set the optimum reference voltage, which poses a practical problem.

In order to solve the above-mentioned drawbacks and problems, the present invention makes the reference voltage dependent on the electric field so that stable diversity reception can be performed from a strong electric field to a weak electric field.

Hereinafter, the present invention will be explained based on illustrated embodiments. FIG. 2 is a block diagram of one embodiment.
In the figure, the constituent elements 1 to 11 are exactly the same as those explained in FIG. 1, so their explanation here will be omitted. A priority circuit 13 obtains only the reception level of the antenna 1 from the output of the first sample and hold circuit 9. Reference numeral 12' denotes a drive circuit which is almost the same as the drive circuit shown in FIG.

That is, in terms of operation, the priority circuit 13 issues a release signal only when the antenna reception level of the first sample-and-hold circuit 9 decreases, and the drive circuit 12' is released to perform diversity reception in the same way as the conventional example shown in FIG. I am learning to do this. Also, the first
Antenna 1 stored in sample hold circuit 9
When the reception level is high, the priority circuit 13 operates and fixes the drive circuit 12' to the antenna 1. An example of the configuration of the priority circuit 13 is shown in FIG. In the figure, 14 is an integrating circuit, 15 is an electric field level correction circuit, and 16 is a priority comparison circuit. That is, the output of the first sample and hold circuit 9 is input to the integration circuit 14 and also directly input to one input terminal of the priority comparison circuit 16. The integrating circuit 14 integrates the input signal so that it becomes the average electric field in the area where the vehicle is traveling, without being sensitive to electric field fluctuations caused by fading, multipath, etc. while the vehicle is traveling. Furthermore, the integrated output is applied to the electric field level correction circuit 15 to make the slope of the ratio of the antenna input electric field to the output of the electric field level correction circuit gentle.

This situation is shown in FIG. However, since the data of this example has a negative polarity in which the output of the level detection terminal 6 of the receiver 4 decreases as the reception level increases, the input electric field level and the first sample hold level have opposite polarity. It's summery. In the figure, the output of the first sample and hold circuit 9 is shown by a solid line,
The output E _s of the electric field level correction circuit 15 is shown by a dotted line.

Therefore, the priority comparison circuit 16 compares the levels of this dotted line and the solid line, and the weak electric field is 0.
~30 μV, the output of the priority comparator 16 operates to perform time-division diversity reception to the drive circuit 12', and in strong electric fields (40 to 70 μV), the priority comparator 16 connects the drive circuit 12' to the antenna 1. Operate the selector switch 3 so that However, even in strong electric fields, fading and multipath occur while the car is running. 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. Even if the level of antenna 1 is fading,
Drive circuit 1 when there is a sudden drop due to multipath etc.
2' to perform time-division diversity reception. Therefore, good diversity reception is possible from weak electric fields to strong electric fields.

FIG. 5 shows another embodiment of the invention. Since the numbers 1 to 11 in the figure are exactly the same as 1 to 11 in the conventional example shown in FIG. 1, the explanation here will be omitted. 1
3' is a priority circuit for an antenna connected to the level detection terminal 6 of the receiver 4 and currently receiving data. This circuit configuration is shown in FIG. 3 and is the same as that in FIG. 2. 12'' is almost the same as the drive circuit 12 shown in FIG.
3', the drive circuit 12'' prioritizes and fixes the currently receiving antenna, or performs time-division diversity reception. Machine 4
Assuming that the antenna currently receiving data is antenna 2, the reception levels of antennas 1 and 2 are stored in the first sample and hold circuit 9 and the second sample and hold circuit 10 via the level detection terminal 6. ing. Then, as in the conventional case, the comparator 11 compares and selects the one with the higher reception level of the antenna. If the level of the antenna 2 currently being used is sufficiently high, the priority circuit 13' sends information to the drive circuit 12'' so that antenna switching will not be performed. Furthermore, when the reception level of the antenna 2 currently receiving drops, the current reception antenna priority circuit 13 sends information to the drive circuit 12'' to perform diversity reception by time division reception. . The internal configuration of this priority circuit is completely the same as that in FIGS. 3 and 4, so a description thereof will be omitted.

By doing this, regardless of whether the currently receiving antenna is antenna 1 or antenna 2, in a strong electric field, diversity reception by time division is stopped as is, and reception without any switching noise by time division is possible. .

FIG. 6 is a waveform diagram for explaining the operation of the priority circuits 13 and 13' having the configuration shown in FIG. 2 _and the configuration shown in FIG. b indicates the output E _s of the level correction circuit 15, and b indicates the output of the priority comparison circuit 16, that is, the priority circuit 13,
13' is shown. In the figure, the portion where time-division diversity reception is performed only when the reception level is lower than E _s is indicated by diagonal lines. Diversity processing can be performed regardless of whether the polarity of the level detection terminal 6 of the receiver 4 is negative as shown in FIG. 4 or positive. The internal processing of the diversity reception controller 7 may be performed with negative polarity or positive polarity.

FIG. 7 shows a specific configuration diagram of the priority circuit 13 shown in FIG. 3. Reference numerals 14 to 16 in the figure correspond to blocks 14 to 16 in FIG. This circuit is designed for negative polarity, so when the electric field suddenly drops in block 17, it immediately starts time-division diversity reception, and even when the electric field increases, antenna 1 is given priority or the current reception is gradually changed. I'm trying to revert to antenna priority. This is because switching between diversity reception and reception that gives priority to one antenna is audibly smoother. The characteristics are as shown in FIG. FIG. 8 shows an example of the configuration of another priority circuit. This circuit is the third
Electric field level correction circuit 15 and priority comparison circuit 1 shown in the figure
This is an example in which 6 is shared. The characteristics are the same as in FIG.

FIG. 9 shows a specific embodiment of the diversity reception controller. This is a specific example of the block diagram shown in FIG. 2, and each block is indicated by a dotted line. 18 is a buffer amplifier for the receiver 4 and the internal circuit of the controller, and 19 is a weak electric field antenna 1 priority circuit.

As described above, by attaching the antenna 1 priority circuit or the antenna priority circuit currently receiving to the time division diversity receiving device,
This solves the drawbacks of conventional time division, such as the generation of switching noise, and enables stable reception from strong to weak electric fields.

Above, we have explained that as a countermeasure against strong electric fields during time-division diversity reception, diversity reception is stopped in strong electric fields and fixed to one antenna preferentially, but another problem is that in weak electric fields. In diversity reception, the RF signal level and the level of external noise, white noise, etc. are almost the same, so the receiver 4 receives a signal containing many random noise components, and the first one in the diversity reception controller 7 sample hold circuit 9,
The magnitude of the level is randomly stored in the output of the second sample and hold circuit 10 depending on the timing at which the signal level is taken into the sample and hold circuit. Therefore, when this information is applied to comparator 11, comparator 11 randomly malfunctions and switches antennas. For this reason, in a weak electric field, switching noise may be more aurally noticeable in diversity reception. Therefore, it is desirable to fix the antenna. The present invention also solves this problem by adding a priority circuit for fixing the antenna. To explain this with reference to FIG. 9, point A in the circuit diagram, that is, antenna 1
A weak electric field priority circuit 19 is added to the output of the first sample and hold circuit 9 that stores the received level of the signal. This is the resistor R, diode D _i and volume VR
When the level at point A exceeds the voltage set by the volume VR, diode D _i becomes conductive and A
It operates in such a way that the voltage at the point does not rise too much.
This characteristic is shown in FIG.

That is, on the first sample hold side, as shown by the dotted line, even if the reception level (input electric field) decreases, the voltage does not increase much. Therefore, since the comparator 11 outputs information so as to receive the one with a larger electric field, in this case, priority is given to the first sample and hold side (antenna 1) shown by the dotted line. Therefore, even if there is noise in a weak electric field, one antenna can be fixed preferentially and good reception can be achieved without malfunctioning. If there is a difference in sensitivity between antennas, giving priority to the antenna with higher sensitivity can have a significant effect.

As described above, the present invention enables good diversity reception by fixing the receiving antenna to one side in a strong electric field or a weak electric field, and the effect is extremely large.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional diversity receiving device, Fig. 2 is a block diagram of an embodiment of the diversity receiving device of the present invention, and Fig. 3 is a block diagram showing an example of a priority circuit used in the present invention. , FIG. 4 is a characteristic diagram of the priority circuit, FIG. 5 is a block diagram of another embodiment of the present invention, FIGS. 6a and b are waveform diagrams for explaining the operation of the priority circuit in the present invention, and FIG. 7 and 8 are wiring diagrams showing a specific example of a priority circuit that can be used in the present invention, FIG. 9 is a wiring diagram showing a specific circuit example of the main part of the present invention, and FIG. 10 is a wiring diagram showing a specific example of a priority circuit that can be used in the present invention. FIG. 3 is a characteristic diagram for explaining the operation of the priority circuit of FIG. 1, 2... Antenna, 3... Selector switch, 4
... Receiver, 6 ... Level detection terminal, 7 ... Diversity reception controller, 8 ... Timing circuit, 9, 10 ... Sample hold circuit, 11
... Comparison circuit, 12', 12'' ... Drive circuit, 1
3, 13'...Priority circuit, 14...Integrator circuit, 1
5...Electric field level correction circuit, 16...Priority comparison circuit, 19...Weak electric field priority circuit.

Claims (1)

[Claims] 1. A first antenna and a second antenna for diversity reception, and a first antenna and a second antenna for diversity reception.
a selector switch unit that switches to select one of the antennas; a receiver to which the antenna output from the selector switch unit is applied; and a diversity reception controller that controls the switching unit, and the diversity reception controller includes a drive circuit that drives the changeover switch section, a first sample and hold circuit that stores the reception level of the first antenna, and a diversity reception controller that controls the switching unit. a second sample and hold circuit that stores reception levels of two antennas, and a comparison circuit that compares output levels of the first and second sample and hold circuits and controls switching of the drive circuit to the antenna with a higher reception level; a timing circuit that causes the drive circuit and the first and second sample and hold circuits to operate in a related manner; and fixed control of the drive circuit so that reception is performed by one of the antennas when the input level of the receiver is high. A diversity receiving device characterized in that the diversity receiving device is configured to include a priority circuit for 2 The priority circuit divides the output of the first sample and hold circuit or the output of the reception level detection terminal into two, one of the signals is input to the integration circuit that averages the level, and the output signal of the integration circuit is based on changes in the output voltage. is input to the electric field level correction circuit that corrects
A patent characterized in that a priority comparison circuit that compares the level of the other divided signal and the output signal of the electric field level correction circuit is configured to fixedly control the drive circuit when the reception level is high in a strong electric field. A diversity receiving device according to claim 1. 3 Between the output terminal of the first or second sample and hold circuit and the midpoint of the power supply voltage dividing resistor,
Claim 1 characterized in that a series circuit of a resistor and a diode is connected to correct one voltage input to the comparator so that one antenna operates preferentially in a weak electric field. Diversity receiving device as described in section.