JPS61237530A - On-vehicle diversity receiver - Google Patents

Abstract

PURPOSE:To simplify the circuit constitution by changing over an antenna to other antenna being at a higher level when a reception signal level of the former antenna is a set value or below and performing no changeover when the signal level is the setting value or over. CONSTITUTION:A comparison circuit 10 compares a reception level signal A with each voltage level of a reference voltage signal G, generates an output signal B in response to the level and outputs the signal to a changeover pulse control circuit 14 for antenna changeover. When the reception level is lower than the reference voltage VS1, the control circuit 14 outputs an antenna changeover signal E and when the level is the voltage VS1 or over, the circuit 14 gives no changeover signal. When the reception level of antennas F1, F2 is both lower than the reference voltage VS1, the antennas are changed over with a prescribed interval to select an antenna with a higher reception level. A voltage reduction circuit 16 attenuates the reference voltage G for a prescribed period when the control circuit 14 outputs the 1st changeover pulse and when the reception level of the changed-over antenna is lower than the level before the changeover, the control circuit 14 changes over again the changed-over antenna to the original antenna.

Description

[Detailed description of the invention] (a) Industrial application fields The present invention includes a plurality of antennas attached to a vehicle.

The present invention relates to a vehicle-mounted diversity receiving device configured to switch depending on the reception state.

(b) Prior Art Conventionally, it has been widely practiced to attach an FM receiver to a vehicle, and in recent years, it has also been proposed to attach a television receiver to a vehicle.

In a typical home, the positional relationship between the signal transmission source and the antenna is constant, but in a vehicle that is constantly moving, the direction of the antenna changes, so the positional relationship between the signal transmission source and the antenna is constant. The directivity with the antenna will no longer match.

Therefore, in the past, a diversity receiver was installed to deal with changes in the antenna input level.

A conventional diversity receiving device samples and holds the input level of each antenna at regular intervals, compares them, and switches to the antenna that provides the highest input level for reception (Japanese Patent Laid-Open No. 58-27444,
JP-A No. 58-198929) and another antenna that switches to the other antenna when the received signal voltage of the antenna falls below a certain value (JP-A No. 58-191539).

(c) Problems to be Solved by the Invention In the above conventional example, the former diversity receiving device has a problem that the circuit is too complicated and the cost is high, and the latter diversity receiving device has the problem that the circuit of the other antenna is too complicated. There was a problem in that the signal was switched regardless of whether the reception status was good or bad.

The present invention aims to solve the above problems and obtain better reception conditions with a simple configuration.

(d) Means for Solving the Problems The present invention searches for the input level of the other antenna when the received signal voltage level of the antenna is below a set value, switches to the antenna with a higher level, and receives the signal from the antenna. This solves the problem of the conventional example by not switching the antenna when the signal voltage level is above a set value.

(e) Examples The present invention will be described in detail below based on the drawings.

FIG. 1 is a block diagram showing a TV diversity receiving apparatus according to an embodiment of the present invention.

F□, F2 is the antenna, 2 is the antenna F, F2
This is an antenna switching circuit that selectively switches one of the antennas and outputs the signal received by the selected antenna as a received signal H.

A receiver 4 inputs the received signal H to drive the speaker 6 and the CRT 8, and includes a detection section for determining whether the received signal H is good or bad.

In order to judge the quality of this received signal H, it is possible to judge by obtaining the output voltage according to the reception level, the output voltage according to noise, the output voltage according to ghost, etc., but in this example Television's I FAG
The C voltage, the voltage applied to the level meter, etc. are taken out as the signal A indicating the reception level.

10 is a comparison circuit, and 12 is a reference voltage generator. This comparison circuit 10 compares each voltage level of the reception level signal A and the reference voltage signal G from the reference voltage generator 12, detects the level of the voltage of the reception level signal A with respect to the reference voltage, and outputs a signal B. It is something.

14 is a switching pulse control circuit which inputs a switching pulse signal C which is a pulse from the vertical synchronizing pulse generator of the receiver 4, and when the comparator circuit 10 detects that the reception level has become lower than the reference voltage, it switches. It outputs a pulse signal E. In this embodiment, a vertical synchronizing pulse is used as a means for generating this switching pulse, but the second
In the case of an FM receiver 5 as shown in the figure, it is necessary to provide a switching pulse generation circuit 15 to continuously generate pulses.

Reference numeral 16 denotes a voltage reduction circuit which outputs a signal F for attenuating the reference voltage for at least a period longer than the generation interval of the next switching pulse after the first switching pulse for switching the antenna is output from the switching pulse control circuit 14. This is what is output. The reason why the reference voltage is attenuated for a certain period of time in this way is that when an antenna is switched and the reception level falls below the reference voltage and the antenna is switched, the reception level of the switched antenna is lower than the reception level before switching. This is to enable switching back to the original antenna when the antenna is even lower, and the details will be described later based on an example.

Next, an outline of the operation of the diversity receiving apparatus shown in FIG. 1, FIG. 2, or FIG. 3 will be explained using a diagram showing changes in the reception level of the antenna F 5F2 and switching of antennas in FIG. 3.

If the reception level of the antenna F8 is higher than the reference voltage Vs supplied from the reference voltage generator 12, the reception level of the antenna F2 is higher than the reception level of the currently used antenna, for example, the antenna F1. It does not switch even if the temperature is high.

This reference voltage Vs is set to be approximately equal to the minimum reception level to obtain video or sound of a certain quality, and if the reception level is higher than this reference voltage Vs, either antenna There is no big difference in the quality of the video or sound even if the signal is used.

At time t, when the reception level of antenna F1 becomes lower than reference voltage Vs, comparator circuit 1o detects this and applies signal B to switching pulse control circuit 14. As a result, the switching pulse control circuit 14 applies a switching pulse to the antenna switching circuit 2 to switch to the antenna F2.

At this time, the voltage reduction circuit 16 reduces the reference voltage vS1 based on a fixed time constant. At the same time, the reception level is also changed from antenna F4 to antenna F based on a certain time constant.
2, and the reception level becomes higher than the reference voltage ■s1 in a period shorter than the switching pulse generation interval. The comparison port 1110 detects this and stops the output of the switching pulse control circuit 14, so that only one switching pulse is output and the state of switching to antenna F2 is maintained.

Thereafter, at one time L2, the reception level of the antenna F becomes higher, but since the reception level of the antenna F2 is higher than the reference voltage Vs, the antenna is not switched.

At time t. When the reception level of antenna F2 becomes lower than reference voltage Vs1, comparator circuit 10 detects this and applies signal B to switching pulse control circuit 14. As a result, a switching pulse is output from the switching pulse control circuit 14, and the antenna F2 is temporarily switched to the antenna F1. As mentioned above, the reference voltage Vs1 is reduced at the same time, but at time t, the reception level of the antenna F is lower than the reception level of the antenna F2, so the reception level changes from antenna F2 to antenna F1. This reception level and the decreasing reference voltage Vs do not intersect within the generation interval of the switching pulse, and further switching pulses are output from the switching pulse control circuit 14 and the voltage decreases again. Switch to antenna F2. When switching to antenna F2 in this way, the rising reception level and the falling reference voltage Vs□ intersect within the generation interval of the switching pulse, and the comparison circuit 1o detects that the reception level has exceeded the reference voltage Vs. Upon detection, the output of the switching pulse is stopped, and the state of switching to antenna F2 is maintained.

At time t4, the antenna is switched from F2 to Fl as at time t1.

After time t5, the reception levels of antennas F and F2 are both lower than the reference voltage Vs. Therefore, after switching from antenna F to F2 in the same way as the operation at time t3, antenna F with a higher reception level is switched again.
Switches to 1. However, at this time ts, the reception level of the antenna F1 is also lower than the reference voltage Vs1, so when the once reduced reference voltage Vs returns to the original voltage (time t6), the comparator circuit 10 When it is detected that the level has become lower than the reference voltage vS1, the antenna switching operation starts again, and this is repeated thereafter.

As described above, in this embodiment, the antenna is not switched when the reception level is equal to or higher than the reference voltage Vs, but is switched when the reception level becomes lower than the reference voltage Vs1.

Furthermore, antenna F1. When the reception levels of F and F are both lower than the reference voltage vs1, the antennas are switched at regular intervals and the antenna with the higher reception level is selected.

FIG. 4 shows the antenna switching circuit 2 shown in FIGS. 1 and 2,
Comparison circuit 10, reference voltage generator 12, switching pulse control circuit 1
4 is a diagram showing the circuit configuration of the voltage reduction circuit 16.

The antenna switching circuit 2 includes pin diodes 18 and 20 for antenna switching, choke coils 22 to 28 for blocking high frequencies, and a flip-flop 30 that inputs the signal E from the switching pulse control circuit 14 to the clock input φ. , a transistor 32.34 which is turned on and off by the outputs Q and 6 of this flip-flop 30, a resistor 31.33, and an operating antenna display which blinks in accordance with the OFF and ON of each transistor 32.34. Light emitting diodes 36 and 38 are provided.

The signal A from the receiver 4 (5) is applied to the (-) input of the comparator 40 as the comparison circuit 10, and the signal G from the reference voltage generator 12 is applied to its (+) input. There is.

The reference voltage generator 12 includes a DC power supply 42, a resistor 44, a capacitor 46 and a resistor 48 that determine the time constant when lowering the reference voltage Vs□, a switch 50 that is turned on and off by the signal F, and a Zener diode. 52 are provided.

The switching pulse control circuit 14 includes a flip-flop 54 that inputs the signal B to the data input and a pulse signal C to the clock input φ, and an AND gate that inputs the signal B and the signal from the output Q of the flip-flop 54. 56, and an ant game I-58 which inputs the output signal of the AND gate 56 and also inputs the signal C.

The voltage reduction circuit 16 is provided with resistors 64 to 72, a diode 76, a comparator 78, a capacitor 80 that determines the time constant from ON to OFF of the output signal F, and a resistor 82.

Next, the operation of the circuit shown in FIG. 4 will be explained using FIGS. 5 to 7, which are partially enlarged versions of FIG. 3 and shown together with time charts.

First, at time t1 shown in FIG.
When the received level of signal B becomes lower than the reference voltage vs1, comparator 40 detects this and sets its output signal B to H level.

When this signal B becomes H level, the flip-flop 54
The output Q of the AND gate 56 becomes H level in synchronization with the fall of the pulse signal C, and the output signal of the AND gate 56 also becomes H level.

When this signal goes high, AND gate 58 is opened and causes the next pulse generated on signal C to be generated on its output signal E.

When a pulse is generated in the signal E, the 8 output states of the flip-flop 30 are switched in synchronization with the rise of this pulse, and when the output Q is at the high and high level, it becomes high and high, respectively.
Switch to L level. This causes transistor 32
is turned on, the transistor 34 is turned off, and the resistor 33,
A current path is formed by the light emitting diode 38, the choke coil 24, the bottle diode 18, and the choke coil 28, and the light emitting diode 38 lights up.The resistance value of the pin diode 18 decreases and becomes ON, and the signal H is connected to the antenna F2. The signal received at is generated.

On the other hand, when the signal becomes H level, the voltage applied to the (+) input of the comparator 78 of the voltage reduction circuit 16 increases based on the time constant determined by the capacitor 80 and the resistor 82, and the comparator 78 compares and calculates the voltage. The output signal F becomes H level. In this way, the period T1 from when the signal becomes H level until when the signal F becomes H level is determined by the values of the capacitor 80 and the resistor 82, and is determined by the interval between the pulses generated in the signal C. It is set to be slightly longer.

When this signal F becomes H level, the switch 50 is turned on and the reference voltage Vs is reduced based on a time constant determined by the capacitor 46 and the resistor 48.

As shown in the upper part of Figure 5, when the antenna is switched from Fl to F2 due to the pulse generated in signal E, the reception level shown by the solid line increases from the reception level of antenna F1 to the higher reception level of antenna F2. Go. At this time, the reception level rises at a constant angle due to the smoothing capacitor 84 provided in the receiver 4 (5). This rising reception level intersects with the falling reference voltage Vs within the pulse generation interval of the signal C, and the output B of the comparator 40 becomes L level at this time. Therefore, the signal E also goes to the L level, the AND gate 58 is closed, and no pulse is generated in the signal E thereafter.

When signal F becomes L level, the voltage applied to the (+) input of comparator 78 gradually decreases while being affected by capacitor 80 and resistor 82, and signal F becomes L level.

When the signal F becomes L level, the switch 50 is turned off, and the reference voltage Vs□ rises again to return to the original voltage level.

Next, at time t3 shown in FIG. 6, when the reception level of the antenna F□ falls below the reference voltage V s 1, the signal B goes to the H level, and then the signal B goes to the H level, similar to the operation described above. become the level. This opens AND gate 58, and a pulse of signal C is generated in its output signal E, switching the antenna from F2 to F□. Immediately after that, the signal F becomes H level, and the reference voltage vS1 begins to fall.

At this time, the reception level is decreasing from the antenna F2 to the lower reception level of the antenna Fi while being affected by the capacitor 84 in the receiver 4 (5). Therefore, the reception level and the reference voltage Vs, which fall together, do not intersect within the interval between pulses generated in the signal C, and the signal B remains at the H level. Therefore, the signal also remains at the H level, and one more pulse is generated in the output signal E of the AND gate 58. The output of the flip-flop 30 is switched by this pulse, the antenna is switched from F to F2 again, and the reception level increases to the reception level of antenna F2, which is higher than that of antenna F1.

This rising reception level intersects with the falling reference voltage Vs within the pulse generation interval of the signal C, so that the signal B becomes L level and the signal also becomes L level. Therefore, the AND gate 58 is closed and no pulse is generated in the signal E. Also, similar to the operation described above, the signal F becomes L level after that, and the reference voltage Vs,
Return to the original voltage level.

At time t shown in FIG. 7, when the reception level of antenna F1 falls below reference voltage vS1, a pulse generated in signal E causes antenna F1 to
Since the reception level of antenna F2 is lower than that of antenna F1, one more pulse is generated in the signal, and the reception level of antenna F2 is switched to F2.
Switch from to F work.

After that, the reduced reference voltage Vs□ rises as described above and returns to the original voltage level, but the antenna F and F2
When the reception level of Vs is lower than the reference voltage Vs□, when the reference voltage Vs returns to the original voltage level, the reference voltage vS1 and the reception level shown by the solid line are again at time t.
They will intersect at 6. At time t6, when the reception level becomes lower than the rising reference voltage Vs, the signal B becomes H level again, and as in the operation described above, two pulses are generated in the signal E, and the antenna is switched from Fl to F2. Switch to engineering.

The reception levels of antennas F1 and F2 are both reference voltage Vs1
If the signal level is lower than , this operation is repeated, but the repetition interval T varies somewhat depending on the change in the reception level. That is, when the reception level rises rapidly, it takes time to cross the reference voltage Vs which is in the middle of rising, and when it falls rapidly, the time it takes to cross the reference voltage vS1 becomes short. However, in a very short period of time, there is no such sudden change in the reception level, and the reference voltage Vs remains constant.

If the reception level of the antennas F1 and F2 is lower than the reference voltage, the antennas are switched at approximately constant intervals T3.

In addition, the reception level of antenna F and F2 are both reference voltage V.
Even if the signal E
When one pulse occurs in , the rapidly rising reception level intersects with the falling reference voltage Vs□, and the signal goes to L level. Of course, during the period from T2 to T in Fig. 5, the reception level also changes. Even if the signal A suddenly decreases due to some influence and becomes lower than the reference voltage Vs1, the above-mentioned ν1
Antenna switching is performed according to either operation.tt
Needless to say.

As described above, in the present invention, the reference voltage Vs.

When the reception level is higher than the reference voltage Vsi, the antenna is not switched, and when the reception level is lower than the reference voltage Vsi, the antenna is switched to the antenna with the higher reception level, and both antennas F1 and F2 are set to the reference voltage Vs.

If the receiving level is lower, the antenna is configured to switch at regular intervals to an antenna with a higher νλ reception level b).

(f) Effects of the Invention According to the present invention, there is no need for a circuit for sampling and holding the reception level of each antenna, and diversity reception can be performed with a simple configuration.

Furthermore, even with a simple configuration, better reception conditions can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a configuration when an embodiment of the present invention is applied to a TV receiver. FIG. 2 is a block diagram showing a configuration when an embodiment of the present invention is applied to an FM receiver. FIG. 3 is a diagram showing an overview of the operation of the embodiment of the present invention, and FIG. 4 is a diagram showing the antenna switching circuit, comparator circuit, reference voltage generator, switching pulse control circuit, and voltage reduction circuit of the antenna shown in FIGS. 1 and 2. A diagram showing a circuit configuration. 5 to 7 are partially enlarged views of FIG. 3, together with a time chart of the circuit shown in FIG. 4. 2... Antenna switching circuit 4, 5... Receiver 10.
... Comparison circuit 12 ... Reference voltage generator 14 ...
・Switching pulse control circuit 16...voltage reduction circuit

Claims (1)

[Scope of Claims] A plurality of antennas, an antenna switching circuit that selectively switches any one of the plurality of antennas, and a switching pulse that continuously generates switching pulses for operating the antenna switching circuit. A generating means, a receiver that receives signals from a selected antenna, a detecting means that outputs a signal having a voltage level corresponding to the reception level of the receiver, and a standard capable of generating a power supply voltage having a constant voltage level. a voltage generator; a comparison circuit for comparing the voltage level from the detection means with the voltage level from the reference voltage generator; a switching pulse control circuit for supplying the antenna switching circuit; and gradually attenuating and later increasing the reference voltage for a period longer than at least the interval between occurrences of the switching pulses from the time the switching pulses are first supplied to the antenna switching circuit. An in-vehicle diversity receiving device comprising: a reference voltage reduction circuit;