JPH024177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a vehicle-mounted diversity receiving device configured to switch a plurality of antennas attached to a vehicle according to their reception conditions.

(b) Prior Art 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 the 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 input level of the antenna. 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). , Japanese Patent Publication No. 1989-198929) and
An antenna that switches to the other antenna when the received signal voltage of the antenna falls below a certain value (Japanese Patent Laid-Open No. 58
−191539) was received.

(c) Problems to be Solved by the Invention In the above-mentioned conventional examples, the former diversity receiving device has a problem that the circuit is too complicated and the cost is high; There was a problem in that the antenna would switch regardless of whether the reception status of the antenna 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 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 improves the reception of 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 Examples of the present invention will be described 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 ₁ , F ₂ are antennas; 2 is antenna F ₁ ,
This is an antenna switching circuit that selects and switches one of _F2 and outputs the signal received by the selected antenna as a received signal H.

4 inputs the received signal H and outputs the speaker 6 and
This is a receiver that drives 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 In this system, the IFAGC voltage of the television, the voltage applied to the level meter, etc. are extracted as 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, and the receiver 4
A switching pulse signal C, which is a pulse from a vertical synchronizing pulse generator, is input to the comparison circuit 10, and when the comparison circuit 10 detects that the reception level has become lower than the reference voltage, it outputs a switching pulse signal E. In this embodiment, a vertical synchronizing pulse is used as a means for generating this switching pulse, but in the case of the FM receiver 5 shown in FIG. It is necessary to generate a pulse.

16 is 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 pulse after the first switching pulse for switching the antenna is output from the switching pulse control circuit 14; It is something to do. 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 overview of the operation of the diversity receiving apparatus shown in FIG. ₁ , FIG. ₂ , or FIG. 3 will be explained using the diagram shown in FIG. explain.

When the reception level of antennas F _{1 and} F 2 is higher than the reference voltage Vs ₁ supplied from the reference voltage generator 12, the reception level of antenna F ₂ is higher than that of the currently used antenna, for example, antenna F _{1 .} It does not switch even if the level is higher.

This reference voltage Vs ₁ 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 ₁ , either antenna There is no big difference in the quality of the video or sound even if the signal is used.
At time t ₁ , when the reception level of antenna F ₁ becomes lower than reference voltage Vs ₁ , comparison circuit 10 detects this and applies signal B to switching pulse control circuit 14 . This causes the switching pulse control circuit 14 to apply a switching pulse to the antenna switching circuit 2 to switch to antenna _F2 .

At this time, the voltage reduction circuit 16 reduces the reference voltage Vs ₁ based on a fixed time constant. At the same time, the reception level is also adjusted based on the antenna antenna based on a certain time constant.
The reception level increases from F ₁ to antenna F ₂ , and the reception level becomes higher than the reference voltage Vs ₁ in a period shorter than the switching pulse generation interval. The comparator circuit 10 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 time _t2 , the reception level of antenna _F1 becomes higher, but since the reception level of antenna _F2 is higher than reference voltage _Vs1 , the antennas are not switched.

At time t ₃ , when the reception level of antenna F ₂ becomes lower than reference voltage Vs ₁ , comparison 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 Vs ₁ is reduced at the same time, but at time t ₃ the reception level of the antenna F ₁ is lower than the reception level of the antenna F ₂ .
Since the reception level of antenna F 2 is lower, the reception level decreases from antenna F ₂ to the reception level of antenna F ₁ , and this reception level and the decreasing reference voltage Vs ₁ are within the generation interval of the switching pulse. The switching pulses do not intersect in the switching pulse control circuit 14.
The signal is output from antenna F2 and then switched to antenna _F2 again.
When switching to antenna F ₂ in this way, the rising reception level and the falling reference voltage Vs ₁ intersect within the generation interval of the switching pulse, and the comparator circuit 10 detects that the reception level has become equal to or higher than the reference voltage Vs ₁ . is detected, the output of the switching pulse is stopped, and the state of switching to antenna _F2 is maintained.

At time _t4 , antenna _F2 is switched to _F1 , as at time _t1 .

After time _t5 , the reception levels of antennas _F1 and _F2 are both lower than reference voltage _Vs1 . Therefore, antenna F ₁ behaves similarly to the operation at time t ₃
After switching from _F2 to F2, the antenna switches again to _F1 , which has a higher reception level. However, at this time t ₅ , the reception level of antenna F ₁ is also below the reference voltage Vs ₁ , so the once reduced reference voltage Vs ₁ is returning to the original voltage (at time t 5).
t ₆ ), the comparator circuit 10 detects that the reception level has become lower than the reference voltage Vs ₁ , and the antenna switching operation starts again, and this process is repeated thereafter.

In this way, in this embodiment, when the reception level is equal to or higher than the reference voltage Vs ₁ , the antenna is not switched and the reception level is equal to or higher than the reference voltage Vs ₁ .
It is to be switched when it becomes lower than
Furthermore, if the reception levels of both antennas F ₁ and F ₂ are lower than the reference voltage Vs ₁ , the antennas are switched at regular intervals and the antenna with the higher reception level is selected. be.

FIG. 4 is a diagram showing the circuit configuration of the antenna switching circuit 2, comparison circuit 10, reference voltage 12, switching pulse control circuit 14, and voltage reduction circuit 16 shown in FIGS. 1 and 2.

The antenna switching circuit 2 includes pin diodes 18 and 20 for antenna switching, switch coils 22 to 28 for blocking high frequencies, and a flip-flop 30 for inputting the signal E from the switching pulse control circuit 14 to the clock input φ. The output Q of this flip-flop 30 turns on and off, respectively.
transistors 32, 34 and resistors 31, 3
3 and each of these transistors 32 and 34.
Light emitting diodes 36 and 38 are provided for displaying the operating antenna, which blink according to OFF/ON.
(-) of the comparator 40 as the comparison circuit 10
The signal A from the receivers 4 and 5 is applied to the input, and the signal G from the reference voltage generator 12 is applied to the (+) input.

The reference voltage generator 12 includes a DC power supply 42 and a resistor 4.
4, a capacitor 46 and a resistor 48 that determine the time constant when lowering the reference voltage Vs ₁ , a switch 50 that is turned on and off by the signal F, and a Zener diode 52.

In the switching pulse control circuit 14, the signal B is inputted to the data input D, and the pulse signal C is inputted to the clock input φ.
, an AND gate 56 that receives the signal B and the signal from the output Q of the flip-flop 54, and an AND gate 58 that receives the output signal D of the AND gate 56 and also inputs the signal C. ing.

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. 5, when the reception level of antenna _F1 falls below reference voltage _Vs1 , comparator 40 detects this and sets its output signal B to H level.

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

When this signal D goes to the H level, the AND gate 58 becomes open and causes the next pulse generated in the signal C to be generated in its output signal E.

When a pulse is generated in the signal E, the output state of the flip-flop 30 is switched in synchronization with the rising edge of this pulse, and when the output Q is at L and H levels, it is switched to H and L levels, respectively. As a result, the transistor 32 is turned on, the transistor 34 is turned off, and the resistor 33, light emitting diode 38, chiyoke coil 24, pin diode 1
8. A current path is formed by the chiyoke coil 28 and the light emitting diode 38 lights up, and the resistance value of the pin diode 18 decreases and becomes an ON state.
The signal received at antenna _F2 is generated as signal H. On the other hand, when the signal D 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,
The output signal F becomes H level. In this way, the period _T1 from when the signal D 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 τ between the pulses generated in the signal C. is also set to be slightly longer.

When this signal F becomes H level, switch 50
turns on, and the reference voltage Vs ₁ decreases based on a time constant determined by the capacitor 46 and resistor 48.

As shown in the upper part of Figure 5, when the antenna switches from F ₁ to F ₂ due to the pulse generated in signal E, the reception level shown by the solid line changes from the reception level of antenna F ₁ to the higher reception of antenna F ₂ . Go up the level. At this time, the reception level rises at a constant angle due to the smoothing capacitor 84 provided in the receivers 4 and 5. This rising reception level intersects with the falling reference voltage Vs ₁ 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 D also goes to the L level, the AND gate 58 is closed, and no pulse is generated in the signal E thereafter.

When the signal D becomes L level, the comparator 7 gradually changes under the influence of the capacitor 80 and the resistor 82.
The voltage applied to the (+) input of 8 falls and the signal F becomes L level.

When the signal F becomes L level, the switch 50
It becomes the OFF state, and the reference voltage Vs ₁ rises again to return to the original voltage level.

Next, at time t ₃ shown in FIG. 6, antenna F ₁
When the received level of drops below the reference voltage Vs ₁ ,
Similar to the operation described above, the signal B goes to H level, and then the signal D goes to H level. As a result, the AND gate 58 becomes open, and a pulse of the signal C is generated in its output signal E, which activates the antenna.
Switch from F ₂ to F ₁ . Immediately after that, signal F goes high
level, and the reference voltage Vs ₁ begins to fall.
At this time, the reception level is decreasing from the antenna F ₂ to the lower reception level of the antenna F ₁ while being affected by the capacitor 84 in the receivers 4 and 5. Therefore, the reception level and the reference voltage Vs ₁ , which both fall, do not intersect within the pulse generation interval of the signal C, and the signal B remains at the H level. Therefore, the signal D also remains at the H level, and one more pulse is generated in the output signal E of the AND gate 58. This pulse causes the output of flip-flop 30 to switch, the antenna to switch again from F ₁ to F ₂ , and the reception level to rise from antenna F ₁ to the higher reception level of antenna F ₂ .

This rising received level is equal to the falling reference voltage.
Vs ₁ and signal C intersect within the pulse generation interval, so that signal B becomes L level and signal D also becomes L level. Therefore, the AND gate 58 is closed and no pulse is generated in the signal. Further, similarly to the operation described above, the signal F becomes L level after that, and the reference voltage _Vs1 also returns to its original voltage level.

At time t ₅ shown in FIG. 7, when the reception level of antenna F ₁ falls below the reference voltage Vs ₁ , the reception level of antennas F ₁ to F ₂ changes due to the pulse generated in signal E, similar to the operation described above. Switch,
Since the reception level of antenna F ₂ is lower than that of antenna F ₁ , one more pulse occurs in the signal to switch the antenna from F ₂ to F ₁ .

Then, the reduced reference voltage Vs ₁ as described above
increases and returns to the original voltage level, but if the reception levels of antennas F ₁ and F ₂ are both lower than the reference voltage Vs ₁ , the voltage will rise again when the reference voltage Vs ₁ returns to the original voltage level. This reference voltage Vs ₁ and the reception level shown by the solid line intersect at time t ₆ . At time t ₆ , when the reception level becomes lower than the rising reference voltage Vs ₁ , signal B becomes H level again, and as in the operation described above, two pulses are generated in signal E and the antenna changes from F ₁ to F ₂ . Then switch to _F1 .

The reception levels of antennas F ₁ and F ₂ are both reference voltage
If it is lower than Vs ₁ , this operation is repeated, but the repetition interval T ₃ varies somewhat depending on the change in the reception level. That is, when the reception level rises rapidly, it takes time to cross the rising reference voltage Vs ₁ , and when it falls rapidly, the time it takes to cross the reference voltage Vs ₁ becomes short.
However, in a minute time, there is no such sudden change in the reception level, and the time is approximately equal to the rise time of the reference voltage Vs ₁ , and when the reception level of antennas F ₁ and F ₂ is lower than the reference voltage, Antenna switching takes place at regular intervals T ₃ .

Note that even if the receiving levels of antennas F ₁ and F ₂ are both lower than the reference voltage Vs ₁ , the operation when switching to the higher receiving level is the same as the operation at time t ₁ , in which a pulse is applied to signal E. As soon as one signal occurs, the rising reception level and the falling reference voltage Vs ₁ intersect, and the signal goes to L level.
Even during the period T ₂ to _{T 3} in the diagram, even if the reception level suddenly drops due to some influence and the signal A drops below the reference voltage Vs ₁ , the antenna will not be switched according to any of the operations described above. Needless to say, it is done.

As described above, in the present invention, the reference voltage Vs ₁
When the reception level is higher than the reference voltage Vs 1, the antenna is not switched, and when the reception level is lower than the reference voltage Vs ₁ , the antenna is switched to a higher reception level, and both antennas F ₁ and F ₂ are lower than the reference voltage Vs ₁ . In some cases, the antenna is configured to switch to an antenna with a higher reception level at regular intervals.

(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 drawings]

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, and FIG. 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. Figures 5 to 7 showing the circuit configuration are partially enlarged views of Figure 3, together with a time chart of the circuit shown in Figure 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] 1. A plurality of antennas, an antenna switching circuit that selectively switches any one of the plurality of antennas, and a switching circuit that continuously generates switching pulses for operating the antenna switching circuit. A pulse generating means, a receiver receiving signals from a selected antenna, a detecting means outputting a signal having a voltage level corresponding to the receiving level of the receiver, and a power source voltage capable of generating a power supply voltage having a constant voltage level. a reference voltage generator; a comparison circuit that compares the voltage level from the detection means with the voltage level from the reference voltage generator; and the comparison circuit causes the switching pulse to be applied only when the voltage level from the detection means is lower. a switching pulse control circuit that supplies the switching pulse to the antenna switching circuit; and gradually attenuating and then increasing the reference voltage for a period longer than at least the interval between occurrences of the switching pulse from when the switching pulse is first supplied to the antenna switching circuit. An in-vehicle diversity receiving device comprising: a reference voltage reduction circuit for reducing the voltage;