JPH07297771A - Receiver on vehicle - Google Patents

Abstract

PURPOSE:To provide a receiver on vehicle to which the reception signal in the optimum reception state can be always inputted even if the strength of field of the reception signal is small or strongest. CONSTITUTION:The strength of field of reception signals of a main antenna 1 and a sub-antenna 2 is obtained. The reception signal of the main antenna 1 is selected when this strength of field is weak, and the reception signal of less interference out of reception signals of the main antenna 1 and the sub- antenna 2 is selected when it is middle, and the reception signal of the sub- antenna 2 is selected when it is strong, and the selected reception signal is supplied to a front end 4. When the obtained strength of field is small, reception signals of the main antenna 1 and the sub-antenna 2 are simultaneously selected and are supplied to the front end 4; and when it is strongest, supply of reception signals of the main antenna 1 and the sub-antenna 2 to the front end 4 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted receiver, and more particularly, to calculating the electric field strengths of received signals of two or more antennas, and to calculate the electric field strengths of two or more antennas according to the strengths of the electric field strengths. The present invention relates to a vehicle-mounted receiver that selects a reception signal and supplies it to the front end.

[0002]

2. Description of the Related Art Conventionally, electric field strengths of received signals received by two or more antennas are obtained, and received signals of two or more antennas are selected and supplied to a front end according to the obtained electric field strengths. A diversity receiver is known as an on-vehicle receiver of the type.

This diversity receiver has one main antenna (for example, a rod antenna attached to a car body) and one or more sub-antennas (for example, a loop antenna embedded in a window glass of a car). Is selectively connected to the front end and always seeks the electric field strength of the received signal received by the main antenna or sub-antenna, and when the obtained electric field strength is less than the weak electric field strength, the received signal of the main antenna is received. Is selected and supplied to the front end, and when the obtained electric field strength is an intermediate electric field strength, the interference signal is less contained in the reception signal of the main antenna and the reception signal of the sub antenna. One of the received signals is selected and supplied to the front end, and the calculated electric field strength is higher than the strong electric field strength. It is one in which the received signal of the sub antenna is supplied is selected in the front end. As described above, in the diversity receiver, a reception signal in a good reception state at various points is selected from the reception signals of the plurality of antennas and is supplied to the front end. The diversity receiver is particularly suitable when used in a place where the electric field strength of the received signal is constantly fluctuated in accordance with the traveling movement of the vehicle, such as a vehicle-mounted receiver.

[0004]

By the way, in the known diversity receiver, even if the strength of the electric field strength of the received signal fluctuates greatly, the received signal in the optimum receiving state is selected at each time point when it fluctuates. However, when the strength of the electric field strength of the received signal becomes the weak electric field strength smaller than the weak electric field strength or the strongest electric field strength larger than the strong electric field strength, the optimum reception state is no longer achieved. There is a problem that a received signal cannot be obtained.

That is, in the known diversity receiver, the electric field strength of the received signal is weak (for example,
If the input converted electric field strength is 10 μV or less),
Even if the reception signal of the main antenna with relatively good reception sensitivity is selected, the reception signal supplied to the front end is in a bad reception state containing a lot of noise,
On the other hand, when the electric field strength of the received signal becomes the strongest electric field strength (for example, 100 mV or more in the input converted electric field strength),
The front end is saturated by the received signal of the strongest electric field strength, and the saturation cannot be released even by the automatic gain control (AGC). As a result, it is equivalent to the input of a received signal in a bad receiving state. There is a problem that becomes.

The present invention eliminates these problems, and an object thereof is to always input a reception signal in an optimum reception state even if the electric field strength of the reception signal is a weak electric field strength or the strongest electric field strength. An object is to provide a vehicle-mounted receiver that can be operated.

[0007]

In order to achieve the above-mentioned object, the present invention seeks the electric field strengths of received signals of a main antenna and a sub-antenna, and when the calculated electric field strength is a weak electric field strength, the main antenna Of the main antenna or the sub-antenna, the one with less interference is selected when the electric field strength is intermediate, and the sub-antenna reception signal is selected when the electric field strength is strong. In the in-vehicle receivers that are selected and supplied to the front end, respectively, when the obtained electric field strength is a weak electric field strength smaller than the weak electric field strength, the reception signals of the main antenna and the sub antenna are simultaneously selected and the front end is selected. To the front end when the strongest electric field strength is larger than the strong electric field strength. Comprises means for stopping the that.

[0008]

In the above means, the electric field strengths of the reception signals of the main antenna and the sub antenna are obtained based on the output voltage of the signal meter (S meter) and the automatic gain control (AGC) voltage derived from the vehicle receiver. If the calculated electric field strength is a weak electric field strength, select the reception signal of the main antenna, and if it is an intermediate electric field strength, select the reception signal of the main antenna or the sub antenna that has less interference. However, when the electric field strength is strong, when the received signal of the sub-antenna is selected and supplied to the front end, respectively, when the obtained electric field strength is a weak electric field strength smaller than the weak electric field strength, The signals received by the antenna and the sub-antenna are simultaneously selected and supplied to the front end, and the one with the strongest electric field strength larger than the strong electric field strength. Stop selection of the received signal of the main antenna and the sub antenna when the have the stops to supply the received signal to the front-end.

As described above, according to the above-mentioned means, when the calculated electric field strength is within the range from the weak electric field strength region to the strong electric field strength region, it is similar to the known vehicle-mounted receiver (diversity receiver). In addition, even if the strength of the electric field strength of the received signal fluctuates, it is possible to select the received signal in the optimum receiving state at each time point when the electric field strength fluctuates. When the reception signal in the good reception state cannot be obtained from the main antenna, the reception signals of the main antenna and the sub antenna are power-combined to obtain the reception signal in the relatively good reception state. The calculated electric field strength increases to the area of the strongest electric field strength, and the amplification level of the received signal is automatically controlled by the automatic gain control (AG
When the front end and the like are still saturated even after being lowered by C), by separating the main antenna and the sub antenna from the front end and stopping the reception signal from being supplied to the front end, The reception condition is prevented from being deteriorated due to the saturation of the front end and the like, and the reception condition is kept relatively good.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a vehicle-mounted receiver according to the present invention.

In FIG. 1, 1 is a main antenna (for example, a rod antenna attached to a body of a car), 2
Is a sub antenna (for example, a loop antenna embedded in a window glass of a car), 3 is an antenna switching circuit, and 4 is FM.
Front end (FM F / E), 5 intermediate frequency amplification and FM demodulation circuit (IF DET), 6 noise canceller and stereo demodulation circuit (NC MPX), 7 audio signal amplification circuit (AFAMP), 8L, 8R Left and right speakers, 9 a multipath noise detection circuit, 10 a multipath noise amplification and automatic gain control (AGC) circuit, 11
Is a waveform shaping and counting circuit, 12 is a first reception mode selection circuit, 13 is a flip-flop (F / F), and 14 is a second
Reception mode selection circuit, 15 and 16 are diodes, 1
7, 18 are coupling capacitors, 19 and 20 are bias resistors, 21 is a high frequency inductor, 22, 23, 24 and 25.
Is a NAND gate, 26 and 27 are transistors, 28,
29 is a resistor, 30 and 31 are comparators, and 32 and 33 are power supplies.

From the main antenna 1 and the sub antenna 2, the antenna switching circuit 3, the FM front end 4,
The intermediate frequency amplification and FM demodulation circuit 5, the noise canceller and stereo demodulation circuit 6, the audio signal amplification circuit 7, and the reproduction circuit portion of the reception signal reaching the left and right speakers 8L and 8R are known in-vehicle receivers (diversity reception). Of the intermediate frequency amplification and FM demodulation circuit 5 to the multipath noise detection circuit 9, the multipath noise amplification and automatic gain control circuit 10, the waveform shaping and counting circuit 11, and the first reception mode. An antenna switching voltage generation circuit portion reaching the selection circuit 12 and the flip-flop 13 has the same configuration as that of a known vehicle-mounted receiver (diversity receiver). However, in a known in-vehicle receiver (diversity receiver), the two antenna switching voltages (selection voltage of the main antenna 1 and selection voltage of the sub antenna 2) obtained at the output of the flip-flop 13 are directly switched. In contrast to the configuration for supplying to the circuit 3, in the present embodiment, these two antenna switching voltages (main antenna 1 selection voltage, sub-antenna 2 selection voltage),
Also, the signal meter (S meter) output voltage and the automatic gain control (AGC) voltage are supplied to the second reception mode selection circuit 14 described later, and the second reception mode selection circuit 14 is supplied.
The configuration is adopted in which the two antenna selection voltages obtained at the outputs of the above are supplied to the antenna switching circuit 3.

By the way, the antenna switching circuit 3 includes a coupling capacitor 17 and a diode 15 connected in series between the main antenna 1 and the input of the FM front end 4.
A coupling capacitor 18 and a diode 16 connected in series between the sub antenna 2 and the input of the FM front end 4.
, A bias resistor 19 shunt-connected to the connection point of the coupling capacitor 17 and the diode 15, and a coupling capacitor 18
And a bias resistor 20 shunt-connected to the connection point of the diode 16 and a high-frequency inductor 21 shunt-connected to the output side of the diodes 15 and 16.

Further, the second reception mode selection circuit 14 is
NAND gate 22 having one input connected to one output of flip-flop 13 and NAND gate 2 having one input connected to the other output of flip-flop 13.
3, a NAND gate 24 having one input connected to the output of the NAND gate 22, a NAND gate 25 having one input connected to the output of the NAND gate 23, and a collector having the other input of the NAND gates 22 and 23. A transistor 26 having a grounded emitter and a transistor 26 having a collector connected to the other input of the NAND gates 24 and 25 and a grounded emitter, and a power supply V
The AGC voltage is supplied to the resistor 28 connected between cc and the collector of the transistor 26, the resistor 29 connected between the power supply Vcc and the collector of the transistor 27, and the inverting input (-), and the output is supplied to the base of the transistor 26. Between the connected comparator 30 and the inverting input (-) of the S meter output voltage, the output of which is connected to the base of the transistor 27, and the non-inverting input (+) of the comparator 30 and ground. And a power supply 33 connected between the non-inverting input (+) of the comparator 31 and the ground.

In this case, the power supply 32 generates a DC voltage V _{AGC (S)} corresponding to the AGC voltage V _{AGC (S)} when the received signal in the strongest electric field strength region is received, and the power supply 33 is in the weak electric field strength region. S meter output voltage V when the received signal of
_(W) corresponding to the direct current voltage V _(W) Is generated.
Also, the AG supplied to the second reception mode selection circuit 14
The C voltage is supplied to the amplification element of the high frequency amplification circuit of the FM front end 4, for example, one of the insulated gate electrodes of the double insulated gate field effect transistor, and as described later, the strength of the electric field strength of the received signal is high. When the received signal having a strong electric field strength or higher is amplified by the high frequency amplifier circuit, the amplification gain is reduced to decrease FM gradually or gradually depending on the frequency.
It has a function of lowering the level of the intermediate frequency signal output from the front end 4. Further, in the FM front end 4, in addition to controlling the gain of the amplification element of the high frequency amplification circuit by the AGC voltage, a voltage control variable resistance element, for example, a PIN diode is shunted to the input circuit of the amplification element of the high frequency amplification circuit. Connect and the second A
The GC voltage may be supplied to the PIN diode to adjust the signal level input to the amplification element of the high frequency amplification circuit. However, this second AGC voltage is
Until the electric field strength of the received signal reaches a constant value, the value is almost zero, and when it exceeds the constant value, the value rises from zero value to a certain finite value.

The vehicle-mounted receiver of this embodiment having the above-mentioned configuration operates as follows.

First, the operation of the reproducing circuit portion in this vehicle-mounted receiver will be described. However, for convenience of explanation, it is assumed that the antenna switching circuit 3 is switched to the main antenna 1 side, that is, only the diode 15 is in the conductive state.

Now, when the FM broadcast signal is received by the main antenna 1, this received signal is supplied from the main antenna 1 to the FM front end 4 via the conducting diode 15 in the antenna switching circuit 3. The FM front end 4 high-frequency amplifies the received signal, then frequency-converts it to an intermediate-frequency signal, and supplies it to the next intermediate-frequency amplification and FM demodulation circuit 5. The intermediate frequency amplification and FM demodulation circuit 5 performs intermediate frequency amplification on the intermediate frequency signal, and then
After removing the noise component, FM demodulation is performed to obtain a demodulated signal, and the next noise canceller and stereo demodulation circuit 6
Supply to. Subsequently, the noise canceller and stereo demodulation circuit 6 performs noise elimination on the demodulated signal, demodulates it into a stereo audio signal, and supplies the stereo audio signal to the next audio signal amplifier circuit 7. Further, the audio signal amplification circuit 7 amplifies the stereo audio signal and supplies it to the right and left speakers 8L and 8R, respectively, to reproduce the stereo audio signal. At this time, the S-meter output voltage representing the strength of the electric field strength of the received signal is derived from the intermediate frequency amplification and FM demodulation circuit 5, and FM
An AGC voltage that controls the gain of the high frequency amplification stage is derived from the front end 4 and is supplied to the first reception mode selection circuit 12 together.

Next, the operation of the circuit for generating the antenna switching voltage in this on-vehicle receiver will be described. However, even in this case, for convenience of explanation, the antenna switching circuit 3 is initially switched to the main antenna 1 side, that is, only the diode 15 is in the conductive state.

First, when the reception signal from the main antenna 1 is supplied to the FM front end 4, the reception signal is converted into an intermediate frequency signal, and then intermediate frequency amplification and F
It is supplied to the M demodulation circuit 5. The intermediate frequency amplification and FM demodulation circuit 5 intermediate frequency amplifies and FM demodulates the intermediate frequency signal to generate an FM demodulation signal, and supplies the FM demodulation signal to the next multipath noise detection circuit 9. The multipath noise detection circuit 9 extracts multipath noise from the input FM demodulated signal and supplies it to the subsequent multipath noise amplification and automatic gain control circuit 10. The multipath noise amplification and automatic gain control circuit 10 amplifies the multipath noise with automatic gain control (AGC) and supplies the amplified multipath noise to the subsequent waveform shaping and counting circuit 11. The waveform shaping and counting circuit 11 counts the number of pulses after shaping the multipath noise into a pulse waveform. In this case, the waveform shaping and counting circuit 11 generates a signal with noise and supplies it to the subsequent first reception mode selection circuit 12 when the count value within the unit time exceeds a predetermined value during pulse counting. . The first reception mode selection circuit 12 constantly determines the strength of the electric field strength of the reception signal based on the AGC voltage supplied from the FM front end 4 and the S meter output voltage supplied from the intermediate frequency amplification / FM demodulation circuit 5. When the strength of the electric field strength obtained here is in a weak electric field strength or a region below it, a selection signal of the main antenna 1 is generated and supplied to the flip-flop 13, When it is in the area more than that, the selection signal of the sub-antenna 2 is generated and supplied to the flip-flop 13, and when it is in the intermediate electric field strength area, the selection signal of the main antenna 1 currently being received is continued. Generated and supplied to the flip-flop 13. Then, the first reception mode selection circuit 12 receives the reception signal of the main antenna 1, and when the signal with noise is supplied from the waveform shaping and counting circuit 11, the reception signal of the main antenna 1 currently being received is received. It is determined that the signal contains a lot of interference components, and the selection signal for the sub-antenna 2 is immediately generated and supplied to the flip-flop 13.
Further, when the selection signal of the main antenna 1 is supplied from the first reception mode selection circuit 12, the flip-flop 13 outputs the selection voltage (logic 1) of the main antenna 1 to the non-inverted output and the sub antenna 2 to the inverted output. When the non-selection voltage (logic 0) is generated and supplied to the next second reception mode selection circuit 14, while the selection signal of the sub antenna 2 is supplied from the first reception mode selection circuit 12, the The non-selection voltage (logic 0) of the main antenna 1 is generated at the inverting output, and the selection voltage (logic 1) of the sub-antenna 2 is generated at the inverting output, and is also supplied to the second reception mode selection circuit 14 that follows.

Then, the following operation is executed in the second reception mode selection circuit 14.

First, in the transistors 26 and 27 and the comparators 30 and 31, the inverting input (-) of the comparator 30 is used.
Is less than or equal to the DC voltage V _{AGC (S) of the} power supply 32 supplied to the non-inverting input (+),
That is, only when the electric field strength of the received signal is the strongest electric field strength larger than the strong electric field strength, a positive voltage is obtained at the output of the comparator 30, and this positive voltage turns on the transistor 26. On the other hand, when the AGC voltage supplied to the inverting input (-) of the comparator 30 is equal to or higher than the DC voltage _{VAGC (S)} supplied to the non-inverting input (+), that is, the received signal is received. When the electric field strength of is a strong electric field strength or a smaller electric field strength, a negative voltage is obtained at the output of the comparator 30, and this negative voltage turns off the transistor 26. On the other hand, when the S meter output voltage supplied to the inverting input (-) of the comparator 31 is less than or equal to the DC voltage V _(W) from the power supply 33 supplied to the non-inverting input (+), that is, the reception Only when the electric field strength of the signal is a weak electric field strength smaller than the weak electric field strength, a positive voltage is obtained at the output of the comparator 30, and this positive voltage turns on the transistor 27. In contrast, the S meter output voltage supplied to the inverting input (-) of the comparator 31 is supplied to the non-inverting input (+)
When it is more than the DC voltage V _(W) from 3, that is,
When the electric field strength of the received signal is a weak electric field strength or a larger electric field strength, a negative voltage is obtained at the output of the comparator 31, and this negative voltage turns off the transistor 27.

Next, the NAND gates 22, 23, 2
In Nos. 4 and 25, the following operations are performed according to the strength of the electric field strength of the received signal currently being received. However, for convenience of explanation, here, as shown in FIG.
One input and the other input of the NAND gate 22 are points A and B, one input and the other input of the NAND gate 23 are the point C and two points, respectively, and one input of the NAND gate 24 (the input of the NAND gate 22 Output), and the other input of NAND gate 24 to F, NAND
One input of gate 25 (output of NAND gate 23)
, The other input of NAND gate 25 is
The output of the ND gate 24 will be called the re-point, and the output of the NAND gate 25 will be called the null point.

First, when the electric field strength of the received signal is in the weak electric field strength region, in the NAND gates 22 and 23, the selection voltage (logic 1) of the main antenna 1 is output from the non-inverted output of the flip-flop 13 at the point a. The non-selected voltage (logic 0) of the sub-antenna 2 is supplied to the point C from the inverted output of the flip-flop 13. At this time, since the transistor 26 is off, the voltage Vcc (logic 1) is supplied to the points B and D through the resistor 28. As a result, a low voltage (logic 0) is obtained at the point e and a high voltage (logic 1) is obtained at the point e. In the NAND gates 24 and 25, the low voltage (logic 0) is supplied to the point E, and the high voltage (logic 1) is supplied to the point E.
At this time, since the transistor 27 is off, the voltage Vcc (logic 1) is supplied to the F and H points through the resistor 29. As a result, high voltage (logic 1)
However, a low voltage (logic 0) is obtained at each point, and this high voltage (logic 1) is supplied to the diode 15 of the antenna switching circuit 3.
Is conducted to couple the reception signal of the main antenna 1 to the FM front end 4.

Next, when the electric field strength of the received signal is in the strong electric field strength region, in the NAND gates 22 and 23,
The non-inverted output of the main antenna 1 is supplied from the non-inverted output of the flip-flop 13 to the point a, and the selected voltage (logic 1) of the sub-antenna 2 is supplied from the inverted output of the flip-flop 13 to the point a. . At this time, since the transistor 26 is off, the voltage Vcc is applied to points B and D.
(Logic 1) is provided. As a result, a high voltage (logic 1) is obtained at point E and a low voltage (logic 0) is obtained at point G.
Further, in the NAND gates 24 and 25, the high voltage (logic 1) is supplied to the point E and the low voltage (logic 0) is supplied to the point E. At this time, since the transistor 27 is off, the voltage Vcc (logic 1) is applied to the F and H points.
Is supplied. As a result, a low voltage (logic 0)
A high voltage (logic 1) is obtained at each point N, and this high voltage (logic 1) causes the diode 16 of the antenna switching circuit 3 to conduct and couples the reception signal of the sub antenna 2 to the FM front end 4.

Next, when the electric field strength of the received signal is an intermediate electric field strength, in the NAND gates 22 and 23, depending on whether the main antenna 1 or the sub antenna 2 is selected, The non-inverting output of the flip-flop 13 supplies the selection voltage (logic 1) of the main antenna 1 or the non-selection voltage of the main antenna 1 (logic 0) to the point, and the inverted output of the flip-flop 13 supplies the sub antenna 2 to the point C. The non-selection voltage (logic 0) or the selection voltage of the sub-antenna 2 (logic 1) is supplied. Also at this time, since the transistor 26 is off, the voltage Vcc (logic 1) is supplied to the points B and D. As a result, a low voltage (logic 0) or a high voltage (logic 1) is obtained at the point e, and a high voltage (logic 1) or a low voltage (logic 0) is obtained at the point g. Further, in the NAND gates 24 and 25, the low voltage (logic 0) or high voltage (logic 1) is supplied to the point E, and the high voltage (logic 1) or low voltage (logic 0) is supplied to the point G. To be done. Also at this time, since the transistor 27 is off, the voltage Vc is applied to the F and C points.
c (logic 1) is provided. As a result, a high voltage (logic 1) or a low voltage (logic 0) is obtained at the re-point, and a low voltage (logic 0) or a high voltage (logic 1) is obtained at the point n, respectively.
The high voltage (logic 1) obtained at this time makes the diode 15 or the diode 16 of the antenna switching circuit 3 conductive.
The reception signal of the main antenna 1 or the reception signal of the sub antenna 2 is coupled to the FM front end 4.

If the electric field strength of the received signal becomes weaker than the weak electric field strength, the NAND gate 2
In points 2 and 23, the selection voltage (logic 1) of the main antenna 1 is supplied from the non-inverting output of the flip-flop 13 to the point a, and the non-selection voltage (logic of the sub-antenna 2 from the inverting output of the flip-flop 13 to the point c). 0) is supplied.
At this time, since the transistor 26 is still off, the voltage Vcc (logic 1) is supplied to the points B and D through the resistor 28. As a result, low voltage (logic 0)
And a high voltage (logic 1) is obtained at point g. Also,
In the NAND gates 24 and 25, the low voltage (logic 0) is supplied to the point e and the high voltage (logic 1) to the point g.
Is supplied. In this state, the transistor 27
Is turned on, the ground voltage (logic 0) is applied to the F and H points.
Is supplied. As a result, a high voltage (logic 1) is obtained at each of the L and N points, and these high voltages (logic 1) make the diodes 15 and 16 of the antenna switching circuit 3 conductive, respectively, and the received signal of the main antenna 1 and The reception signal of the sub antenna 2 is coupled to the FM front end 4.

When the electric field strength of the received signal becomes the strongest electric field strength larger than the strong electric field strength, in the NAND gates 22 and 23, the main antenna 1 is not selected from the non-inverted output of the flip-flop 13 at the point a. The voltage (logic 0) is supplied, and the selected voltage (logic 1) of the sub-antenna 2 is supplied to the point C from the inverted output of the flip-flop 13. In this state, since the transistor 26 is turned on, the ground voltage (logic 0) is supplied to the points B and D. As a result, a high voltage (logic 1) is obtained at each of the points E and G. Further, in the NAND gates 24 and 25, the high voltage (logic 1) is applied to each of the points E and G.
However, since the transistor 27 is off at this time, the voltage Vcc (logic 1) is also supplied to the F and H points via the resistor 29. As a result, a low voltage (logic 0) is obtained at each of the L and N points, and these low voltage (logic 0) is supplied to the diode 1 of the antenna switching circuit 3.
The signals received by the main antenna 1 and the received signal by the sub antenna 2 are FM respectively.
It will no longer be connected to the front end 4.

Here, FIG. 2 shows the operating states of the transistors 26 and 27 in the second reception mode selection circuit 14 and the voltage generated at the points A to N in accordance with the variation of the electric field strength of the received signal. It is explanatory drawing which shows a logic state, Comprising:
The above-mentioned operation in the reception mode selection circuit 14 is collectively shown.

As is apparent from FIG. 2, the second reception mode selection circuit 14 outputs the non-inverted output of the flip-flop 13 when the electric field strength of the received signal is within the range of the weak electric field strength region to the strong electric field strength region. Corresponding to the selection voltage (logic 1) of the main antenna 1 supplied from the main antenna 1
Corresponding to the selection voltage (logic 1) of the sub-antenna 2 supplied from the inverted output of the flip-flop 13 while generating a high voltage (logic 1) for selecting
A high voltage (logic 1) for selecting is generated, which is the same as the state when the second reception mode selection circuit 14 does not exist. However, when the electric field strength of the received signal becomes the weak electric field strength area weaker than the weak electric field strength or the strongest electric field strength area larger than the strong electric field strength, the second reception mode selection circuit 14 is supplied from the flip-flop 13, respectively. Regardless of the selection voltage (logic 1) of the main antenna 1 or the selection voltage (logic 1) of the sub antenna 2, a high voltage (logic 1) that selects both the main antenna 1 and the sub antenna 2 or the main antenna 1 and the sub antenna It generates a low voltage (logic 0) that does not select both of the antennas 2, and in this respect realizes a selection state different from the selection state of the antenna performed in the known vehicle receiver of this type. .

Next, FIG. 3 shows the relationship between the electric field strength of the received signal in the vehicle-mounted receiver shown in FIG. 1, the S meter output voltage, the AGC voltage (and the second AGC voltage), and the antenna selection state. It is an operation characteristic view showing an example.

In FIG. 3, the horizontal axis represents antenna input (dB).
μ) is the electric field strength of the received signal, and the vertical axis is the S meter output voltage and AG represented by the DC voltage (V).
C voltage (and second AGC voltage).

As shown in FIG. 3, when the reception signal is received by this vehicle-mounted receiver, the antenna input is 0 dBμ.
To about 20 dBμ, it is a weak electric field strength region, and at this time, both the main antenna 1 and the sub antenna 2 are selected. Antenna input is about 20 dB
In the range from μ to about 35 dBμ, it is a weak electric field strength region, and at this time, only the main antenna 1 is fixedly selected. Antenna input is about 35 dBμ to about 85
When it is within the range up to dBμ, it is in the intermediate electric field strength region, at which time the diversity operation is performed and either the main antenna 1 or the sub antenna 2 is selected. When the antenna input is within the range of about 85 dBμ to about 105 dBμ, it is in the strong electric field intensity region, and only the sub antenna 2 is fixedly selected at this time. When the antenna input exceeds the range of about 105 dBμ, it is the strongest electric field strength region, and at this time, neither the main antenna 1 nor the sub antenna 2 is selected.

Next, regarding the S meter output voltage, when the antenna input is within the range of 0 dBμ to about 60 dBμ, that is, until the antenna reaches the middle of the weak electric field strength region to the middle electric field strength region, the antenna input increases. It increases linearly in proportion and has a characteristic that when the antenna input exceeds the range of about 60 dBμ, that is, from the middle of the intermediate electric field strength region to the strongest electric field strength region, it becomes almost constant regardless of the antenna input. Furthermore, the AGC voltage is almost constant regardless of the antenna input when the antenna input is within the range of 0 dBμ to about 60 dBμ, that is, until the middle of the weak electric field strength region is reached. When the input is within the range of about 60 dBμ to about 85 dBμ, that is, from the middle of the intermediate electric field strength region to the beginning of the strong electric field strength region, the input power decreases slightly as the antenna input increases, In the range of 85 dBμ to about 105 dBμ, that is, in the strong electric field strength region, it sharply decreases in accordance with the increase of the antenna input, and when the antenna input exceeds the range of about 105 dBμ, that is, in the strongest electric field strength region. , The characteristic is such that it gradually decreases in proportion to the increase in the antenna input. In addition, regarding the above-mentioned second AGC voltage, when the antenna input is in the range of 0 dBμ to about 60 dBμ, that is, until the middle of the weak electric field strength region to the middle electric field strength region is reached, It becomes almost zero value and the antenna input is about 6
In the range of 0 dBμ to about 85 dBμ, that is, from the middle of the intermediate electric field strength region to the beginning of the strong electric field strength region, the value is almost constant regardless of the antenna input, and the antenna input exceeds about 85 dBμ. When in range,
That is, in the strong electric field strength region and the strongest strength region, the characteristic becomes a constant value that is slightly larger than the constant value.

Further, FIG. 4 shows a state in which the main antenna 1 and the sub-antenna 2 are selected when a reception signal whose electric field strength sequentially changes with time is input to the vehicle-mounted receiver shown in FIG. It is a timing chart shown.

In FIG. 4, the horizontal axis is the time expressed in seconds (S), and the vertical axis is the electric field strength expressed in antenna input (dBμ).

As shown in FIG. 4, first, when the electric field strength of the reception signal of this vehicle-mounted receiver is in the intermediate electric field strength area (diversity operation area), that is, at time t.
During the period from ₀ to time t _5, one of the main antenna 1 or the sub-antenna 2 is selected, but in which the received signal of the selected antenna is supplied to the vehicle-mounted receiver, the time t ₁ , Time t ₂ , time t ₃ , and time t _4, when a predetermined number or more of multipath noises per unit time are detected in the received signal, the antenna selected at that time is selected. Instead, another antenna is selected. For example, although between the time t ₀ of time t ₁ the main antenna 1 is selected, the multipath noise is detected in the time t _1, between the time t ₁ of time t ₂ is selected sub antenna 2 To be done. Then, at time t ₂ , since multipath noise is detected again, time t ₂
In the intermediate electric field strength region (diversity operation region), such that the main antenna 1 is selected again from the time t ₃ to the time t ₃ , every time multipath noise is detected, the main antenna 1 and the sub antenna are 2 and are selected alternately.

Next, when the electric field strength of the received signal drops from the intermediate electric field strength area to the weak electric field strength area, that is, during the period from time t ₅ to time t ₆ , only the main antenna 1 is fixed. The reception signal selected and received with high sensitivity by the main antenna 1 is supplied to the vehicle-mounted receiver.

Then, when the electric field strength of the received signal decreases from the weak electric field strength area to the weak electric field strength area, that is,
The period from the time t ₆ to time t _7, both of the main antenna 1 and the sub antenna 2 is selected, the reception signal selected by the antennas 1 and 2 are power combining, it is supplied to the vehicle-mounted receiver .

Next, when the electric field strength of the received signal rises from the weak electric field strength area to the weak electric field strength area, that is, during the period from time t ₇ to time t ₈ , as described above, only the main antenna 1 is operated. The reception signal that is fixedly selected and received by the main antenna 1 with high sensitivity is supplied to the vehicle-mounted receiver.

Further, when the electric field strength of the received signal rises from the weak electric field strength area to the intermediate electric field strength area (diversity operation area), that is, in the period from time ₈ to time t ₁₀ , the main antenna 1 or One of the sub antennas 2 is selected, and the reception signal of the selected antenna is supplied to the vehicle-mounted receiver. At this time, since multipath noise was detected at time t ₉ , the main antenna until then was selected. The point that the selection is changed from the selection of 1 to the selection of the sub-antenna 2 is the same as the above-mentioned case.

Subsequently, when the electric field strength of the received signal rises from the intermediate electric field strength area (diversity operation area) to the strong electric field strength area, that is, in the period from time t ₁₀ to time t ₁₁ , the sub antenna Only 2 is fixedly selected,
The reception signal received by the sub antenna 2 with low sensitivity is supplied to the vehicle-mounted receiver.

Next, when the electric field strength of the received signal rises from the strong electric field strength area to the strongest electric field strength area, that is,
In the period after time t _11, the selection of both the main antenna 1 and the sub antenna 2 is stopped, the reception signal of the strongest electric field strength is directly supplied to the vehicle-mounted receiver, and the FM front end 4 and the like are saturated. It is preventing.

As described above, according to this embodiment, even if the electric field strength of the received signal is reduced to a weak electric field strength smaller than the weak electric field strength, the received signals of the main antenna 1 and the sub antenna 2 are power-combined. A reception signal in a relatively good reception state can be obtained, and the main antenna 1 and the sub-antenna 2 are isolated from the front end 3 even if the electric field strength of the reception signal increases to the strongest electric field strength larger than the strong electric field strength. By stopping the supply of the reception signal to the front end 4, deterioration of the reception state due to saturation of the front end 4 and the like can be prevented, and a relatively good reception state can be maintained.

[0046]

As described above, according to the present invention,
When the electric field strength of the received signal is within the range from the weak electric field strength area to the strong electric field strength area, even if the electric field strength of the received signal fluctuates, it does It is possible to select the reception signal in the optimum reception state at the time point, and the electric field strength of the reception signal decreases to a weak electric field strength region smaller than the weak electric field strength, and the reception signal in the good reception state is received from the main antenna. When it is no longer available, there is an effect that a reception signal in a relatively good reception state can be obtained by power combining the reception signals of the main antenna and the sub-antenna. When the field strength increases to the strongest field strength region that is larger than the strong field strength and the front end etc. becomes saturated, place the main antenna and sub antenna at the front end. Was isolated by stops the reception signal is supplied to the front end, to prevent the deterioration of the receiving state based on the saturation of such front-end, there is an effect that it is possible to maintain a relatively good receiving condition.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a configuration of an embodiment of an in-vehicle receiver according to the present invention.

FIG. 2 is an explanatory diagram showing an operating state of a transistor of a second reception mode selection circuit and a logic state of a voltage generated at each point in accordance with a change in electric field strength of a reception signal.

FIG. 3 is an operational characteristic diagram showing an example of the relationship between the electric field strength of a received signal, the S meter output voltage, the AGC voltage, and the antenna selection state in the vehicle-mounted receiver shown in FIG.

4 is a timing chart showing selection states of a main antenna and a sub-antenna when a reception signal with varying electric field strength is input to the vehicle-mounted receiver shown in FIG. 1. FIG.

[Explanation of symbols]

1 Main Antenna 2 Sub Antenna 3 Antenna Switching Circuit 4 FM Front End (FM F / E) 5 Intermediate Frequency Amplification and FM Demodulation Circuit (IF DET) 6 Noise Canceller and Stereo Demodulation Circuit (NC)
MPX) 7 Audio signal amplification circuit (AF AMP) 8L, 8R Left and right speakers 9 Multipath noise detection circuit 10 Multipath noise amplification and automatic gain control (AG
C) Circuit 11 Waveform shaping and counting circuit 12 First reception mode selection circuit 13 Flip-flop (F / F) 14 Second reception mode selection circuit 15, 16 Diode 17, 18 Coupling capacitor 19, 20 Bias resistor 21 High frequency inductor 22, 23, 24, 25 NAND gate 26, 27 transistor 28, 29 resistor 30, 31 comparator 32, 33 power supply

Claims (3)

[Claims] 1. The electric field strengths of the received signals of the main antenna and the sub antenna are calculated, the received signal of the main antenna is selected when the calculated electric field strength is a weak electric field strength, and the main electric field is selected when the electric field strength is an intermediate electric field strength. In the in-vehicle receiver that selects the reception signal with less interference among the reception signals of the antenna or sub-antenna and selects the reception signal of the sub-antenna when the electric field strength is strong, and supplies it to the front end respectively, When the calculated electric field strength is a weak electric field strength that is smaller than the weak electric field strength, the received signals of the main antenna and the sub antenna are simultaneously selected and supplied to the front end, and when the strongest electric field strength is larger than the strong electric field strength. Is an on-vehicle receiver characterized in that it stops supplying the reception signals of the main antenna and the sub antenna to the front end. 2. The reception signals of the main antenna and the sub antenna are selected by an antenna switching circuit including a PIN diode connected between the main antenna and the sub antenna and the front end, a signal meter output voltage and automatic gain control. 2. A vehicle-mounted vehicle according to claim 1, wherein an operation state is controlled by a voltage, and a reception mode selection circuit that generates an antenna selection voltage that selectively makes the PIN diode conductive and / or non-conductive. Receiving machine. 3. The weak electric field strength has an input converted electric field strength of about 10 μV or less, and the strongest electric field strength has an input converted electric field strength of about 100 mV or more. In-vehicle receiver.