JPH0521453B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an antenna booster suitable for application to, for example, a car radio.

[Prior Art] Pole-type antennas have been widely used as conventional in-vehicle radio antennas. However, this type of antenna is attached to the outside of the vehicle and generates wind noise when driving, so in recent years,
Windshield antennas embedded in window glass have become popular.

[Problems to be Solved by the Invention] According to this windshield antenna, inconveniences such as wind noise can be solved. However, the windshield antenna has a problem in that the antenna gain is reduced by more than 10 dB compared to the pole type antenna, and a sufficient S/N ratio cannot be obtained.

As a means to compensate for this, an antenna booster is known, which is disposed directly below the antenna, amplifies the received signal from the antenna, and supplies the amplified signal to the receiver.

FIG. 3 shows the configuration of this type of antenna booster 1, which consists of a broadband bandpass filter 2 that passes the entire FM frequency range, and a high frequency amplifier 3 that amplifies its output. is sent to the antenna terminal of the receiver.

According to this antenna booster 1, the inconvenience that the signal is attenuated between the antenna and the receiver and the S/N ratio is impaired can be eliminated, and good reception can be expected.

However, with conventional antenna boosters,
Since it was not possible to know the tuning frequency of the receiver, it was a non-tunable type and amplified the entire FM band, which increased distortion in the strong electric field region, which was extremely inconvenient in practice.

The present invention was made against this background, and an object of the present invention is to provide a tunable antenna booster that enables good reception both under strong electric fields and under weak electric fields.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides an antenna booster disposed directly below an antenna, which amplifies a received signal from the antenna and supplies the signal to a receiver. selection means for selecting whether to directly supply the received signal to the receiver or to amplify it and then supply it to the receiver; a tuning frequency detection circuit that detects based on a signal; a tuning circuit that tunes based on the signal from the tuning frequency detection circuit; a high frequency amplifier that amplifies the output of the tuning circuit; and a high frequency amplifier that amplifies the output of the tuning circuit; When it is selected to amplify the received signal and then supply it to the receiver, the antenna terminal is connected to the input terminal of the tuned frequency detection circuit, and after a predetermined period of time, the output terminal of the high frequency amplifier is connected to the input terminal of the tuned frequency detection circuit. It is characterized by comprising circuit connection means connected to the antenna terminal.

[Function] According to the above configuration, in a weak electric field area, when the operator selects to amplify the received signal from the antenna using the selection means and then supply it to the receiver, the circuit connection means amplifies the received signal from the antenna. Since the terminal is connected to the input end of the tuning frequency detection circuit, the tuning frequency detection circuit detects the tuning frequency of the receiver based on the local oscillation signal leaking from the antenna terminal. Thereby, the tuning circuit is tuned by the signal from the tuning frequency detection circuit, and the high frequency amplifier amplifies the output of the tuning circuit. Then, the circuit connecting means connects the output end of the high frequency amplifier to the antenna terminal after a predetermined period of time has elapsed, so in weak electric field areas,
It becomes possible to amplify only the signal being received by the receiver directly under the antenna and send it to the receiver.

As a result, the S/N ratio of the received signal can be significantly increased, and good reception can be performed in both strong and weak electric fields.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In the figure, 11 is an antenna. The signal captured by this antenna 11 is supplied to the input end of an antenna booster 12 provided directly below it. The configuration of the antenna booster 12 will be explained below.

A changeover switch 13 is connected to the input end of the antenna booster 12, and a changeover switch 14 is connected to the output end thereof. These changeover switches 13 and 14 are
Either supplying the output of the antenna 11 directly to the receiver, or
This is used to switch between amplifying and then supplying the signal. That is, when the push button switch 15 is pressed, the judgment circuit 16 is reversed each time the push button switch 15 is pressed, and the changeover switches 13 and 14 are switched to switch the antenna 11 to the direct connection side or to the amplification side. In addition,
The judgment circuit 16 is composed of a flip-flop, and its output is supplied to the LED 18 via the LED drive circuit 17, so that the LED 18 is turned on when the amplification side is selected.

The output of the judgment circuit 16 is also supplied to a timer circuit 19 for maintaining operation. This timer circuit 19 is for switching the changeover switch 20 to the lower side of the diagram, that is, to the input side of the amplifier 21, for a certain period of time when the amplification side is selected.

This amplifier 21 or voltage latch circuit 24 is
This is to detect the tuning frequency of the receiver using the local oscillation signal leaking from the antenna terminal of the receiver.

First, the amplifier 21 amplifies the local oscillation signal leaking from the antenna terminal. This signal is frequency-divided by a frequency divider 22 and then passed through an F-V converter 23.
is converted into a voltage corresponding to the frequency. This voltage is latched by a voltage latch circuit 24 and supplied to tuning circuits 25 and 27. In this way, the tuning frequency of the receiver is detected and converted into a voltage, and the tuning frequency of the tuning circuits 25 and 27 is controlled by this voltage.

The tuning circuits 25 and 27 are electronic tuning circuits constructed of varicaps or the like. Tuned circuit 2
5 selects a received signal from the signals sent from the antenna 11 through the changeover switch 13 and supplies it to the high frequency amplifier 26 . The high frequency amplifier 26 amplifies this received signal, and the tuning circuit 27
supply to. The tuning circuit 27 supplies this received signal to the antenna terminal of the receiver via the changeover switches 20 and 14. Note that the timer circuit 19 only switches the switch 20 to the amplifier 21 side for a certain short period of time, so when the reception frequency detection is finished, the switch 20 switches to the tuned circuit 27 side, and the signal from the tuned circuit 27 to the switch 14 is switched to the tuned circuit 27 side. Form a passage.

Next, the operation of this embodiment will be explained.

Normally, the flip-flop of the judgment circuit 16 is in a reset state, and the changeover switches 13 and 14 are
It is connected to the direct connection side, that is, the side where the output of the antenna 11 is directly connected to the receiver.

In this reception state, when the vehicle enters a weak electric field area and the reception state deteriorates, the driver presses the push button switch 15. As a result, the judgment circuit 16 is inverted, and the switches 13 and 14 are switched to the amplification side. Further, the changeover switch 20 is briefly switched to the amplifier 21 side, that is, to the receiving frequency detection side, through the operation holding timer circuit 19.

In this state, the amplifier 21 is supplied with a leakage signal from the antenna terminal of the receiver, that is, a leakage signal from the local oscillator. After this is amplified and frequency-divided, it is converted into a voltage corresponding to the local oscillation frequency, that is, the reception frequency, and is latched by the voltage latch circuit 24. This voltage is supplied to tuning circuits 25 and 27.

The tuning circuits 25 and 27 are tuned to the reception frequency of the receiver by the above voltage. Therefore, the received signal from the antenna 11 is tuned by the tuning circuit 25, amplified by the high frequency amplifier 26, further tuned by the tuning circuit 27, and sent to the antenna terminal of the receiver.

On the other hand, if you enter a strong electric field area and the received sound is distorted, press the push button switch 15, the judgment circuit 16 will be reversed again, and the changeover switch 13,
14 is returned to the direct connection side, and reception is performed with the antenna 11 directly connected to the antenna terminal of the receiver.

In this way, in this embodiment, since only the signal tuned to the reception frequency is selected and amplified directly under the antenna, it is possible to increase the S/N ratio of the reception signal, and it is good even under a weak electric field or a strong electric field. reception becomes possible.

Next, a modification of this invention will be explained.

FIG. 2 is a block diagram showing the configuration of a modified example. This modification is applicable to a device in which a level meter output terminal, an AGC output terminal, and a local oscillation signal output terminal are provided on the receiver side. This modification differs from the above-described embodiment in the following points.

The input of the amplifier 21 is directly supplied with a signal from the local oscillator of the receiver.

The high frequency amplifier 26 is supplied with an AGC signal.

The determination circuit 16 is supplied with a signal from the level meter output terminal, and when the level falls below a certain value, the changeover switches 13 and 14 are switched to the amplification side.

The timer circuit 19 for maintaining operation and the changeover switch 20 shown in FIG. 1 are removed.

In this modification, when the reception level falls below a certain value, the system is automatically switched to the amplification side and the booster is activated. Furthermore, since AGC can be applied to the high frequency amplifier 26, it is possible to prevent the signal from being distorted under a strong electric field. However, unlike one embodiment, it cannot be applied to any receiver.

[Effects of the Invention] As explained above, the present invention provides an antenna booster that is installed directly below the antenna.
Since a tuning circuit and a high frequency amplifier are provided, good reception is always possible in both weak and strong electric field regions.

In addition, the tuning frequency of the receiver is detected using the local oscillation signal leaking from the antenna terminal of the receiver, so it can be used with any type of receiver.
The advantage is that it can be applied as is.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams showing the configuration of an embodiment and a modified example of the present invention, respectively, and FIG. 3 is a block diagram showing the configuration of a conventional antenna booster. 11... Antenna, 12... Antenna booster, 13, 14, 20... Changeover switch, 15...
...Push button switch (selection means), 19... Timer circuit for holding operation (circuit connection means), 21...
Amplifier, 22...Frequency divider, 23...F/V
Converter, 24... Voltage latch circuit (21 to 2 above)
4 is a tuning frequency detection circuit), 25, 27...tuning circuit, 26...high frequency amplifier.

Claims (1)

[Scope of Claims] 1. An antenna booster disposed directly below an antenna that amplifies a received signal from the antenna and supplies the amplified signal to a receiver, which supplies the received signal from the antenna directly to the receiver, or a selection means for selecting whether to amplify and then supply to the receiver; a tuning frequency detection circuit that detects a tuning frequency of the receiver based on a local oscillation signal leaking from an antenna terminal of the receiver; a tuning circuit that tunes using a signal from a detection circuit; a high-frequency amplifier that amplifies the output of the tuning circuit; and a high-frequency amplifier that amplifies the received signal from the antenna by the selection means and then supplies the signal to the receiver. An antenna characterized by comprising circuit connection means for connecting the antenna terminal to the tuning frequency detection circuit when selected, and connecting the output end of the high frequency amplifier to the antenna terminal after a predetermined time has elapsed. booster.