JPH0227645Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diversity reception type automotive receiver.

When a moving car receives radio waves such as FM broadcasts, periodic fading occurs due to variations in the field strength of the received radio waves in the direction of travel, and time fluctuations in multipath distortion due to movement of the receiving point. Or, the received sound quality tends to deteriorate due to causes such as changes in the reception level due to the antenna directionality when the direction of travel changes, and in particular, the received sound becomes "buzzy" and stops at short intervals, making it difficult to recognize the received content. It may become.

On the other hand, by tuning the conductor pattern of the antenna wire installed on the window glass of a car, it is possible to obtain good reception characteristics (gain, directivity, frequency characteristics) in a specific broadcast reception band. , is widely used.

However, even if the reception characteristics of the windowpane antenna are made nearly omnidirectional, it does not contribute much to improving the periodic reception interference caused by the driving of the vehicle as described above.

In addition, tuned conductor patterns are generally complex and occupy a large area, so they obstruct visibility, and when providing an anti-fog heater wire, the anti-fog area is severely limited.

Therefore, the present invention uses an antenna conductor pattern that is as simple as possible to reduce the obstruction of visibility and the reduction in the anti-fogging area, and on the other hand, compensates for the deterioration of reception characteristics by using privacy reception with complementary directivity. This allows reception disturbances such as fading to be compensated for by spatial diversity reception.

Embodiments of the present invention will be described below with reference to the drawings.

In the embodiment of the present invention, a pole antenna 1 erected on the side of an automobile is used as the first antenna. For example, a car 2 as shown in FIG.
A pillar antenna attached to a pillar, or a rod antenna erected on the side of the hood or trunk lid of an automobile 2 as shown in FIG. 2A is used. In these pillar antennas or rod antennas, as shown in the directional characteristic graph of FIG. 1B or FIG. 2B, a dip occurs on the side opposite to the mounting position due to the influence of the vehicle body.

Further, in the embodiment of the present invention, a glass antenna wire 4 provided on the front window glass or rear window glass of the automobile is used as the second antenna. For example, a folded dipole antenna wire 4 provided on a front window glass 5 as shown in FIG. 3A, or a semi-folded dipole antenna strip 4 provided on a rear window glass 6 as shown in FIG. 4A. An antenna wire 4 is used.

The antenna wire 4 shown in FIG. 3A is formed by embedding the antenna wire in a resin adhesive film between two glass plates. The antenna wire 4 shown in FIG. 4A is formed by printing and baking a conductive paste material in the same way as the heating conductive wire 7. Note that the heating conductive wires 7 are collected on the busbars 8 and 9, and are connected to the power supply lines 0 and 11.
A current is passed through the When the heating conductive wire 7 is also used as an antenna, the feed line 10,
A chiyoke coil 12 having high impedance in the radio frequency range is inserted into each of the coils 11.

Window glass antennas 4 as shown in FIGS. 3A and 4A generally have a figure-of-eight characteristic that shows strong directivity in the direction perpendicular to the element when placed in free space. Or, if it is provided at 6, a dip will occur in the front-rear direction of the vehicle due to the influence of the vehicle body, as shown in FIG. 3B or 4B.

Therefore, since the angular positions of the dip points of the pole antenna 1 and the window glass antenna wire 4 are different,
By combining these, it becomes possible to effectively perform diversity reception. Note that a combination of only pole antennas or only window glass antennas is a combination of antennas with a specific tendency of directivity, and is not effective for diversity reception. Although it is possible to obtain an antenna with directional characteristics, the pattern becomes complicated and the area is disadvantageous. In particular, in the case of a front window glass, there are restrictions on the area and number of antenna wires to ensure visibility, so it is difficult to tune the directivity characteristics. On the other hand, the present invention cleverly utilizes the difference in directivity characteristics between the pole antenna installed on the side of the car and the antenna strip attached to the window glass, and achieves good reception characteristics even with a relatively simple antenna pattern. I'm trying to get that.

FIGS. 5a to 5c show actual measurement data of the directivity characteristics of the pillar antenna 1 shown in FIG. 1A and the windshield antenna 4 shown in FIG. 3A. (a is 76MHz, b is 84M
Hz, c is 90MHz). There are significant differences in directional characteristics in all frequency bands.

FIG. 6 is a block circuit diagram of an FM receiver used in the receiving system of this embodiment. 6th
In the figure, received signals obtained from a pole antenna 1 and a glass antenna wire 4 are selected by a changeover switch circuit 17 and supplied to a front end and IF circuit 24. This front end and
The received signal that has undergone tuning amplification, intermediate frequency conversion, and FM detection in the IF circuit 24 is supplied to a multiplexer 27 via a high-frequency cut control filter 25 and a noise blanker 26, where it is stereo demodulated and output to an R channel and an L channel. is led out from the output terminal to the audio power amplification section. Note that the multiplexer 27 is supplied with a control signal c such as an automatic stereo/monaural switching signal from the IF circuit 24.

In the front end and IF circuit 24, detection of the received signal level (level detection of IF output or detection output) is performed in order to mute detuning noise between stations, and when the received signal level drops to a certain level, The detection output is muted. This received signal level detection signal a is IF
It is applied to a mute drive circuit in circuit 24 and to an automatic level setting circuit 28. This automatic level setting circuit 28 has a function of changing the threshold of the switching input level according to the switching frequency of the switch circuit 17, and generates a detection signal b when the switching input level is below this threshold. This detection signal b is sent to the antenna switching control circuit 30,
Here, a switching pulse d is generated in synchronization with the approximately 100 KHz clock output from the clock generator 29.
This switching pulse d is applied to the trigger input of the T-type flip-flop 31, thereby inverting the output (Q,) of the flip-flop 31.

The Q output and output of the flip-flop 31 are used as switching control signals for the switch circuit 17,
For example, when the received signal level of pole antenna 1 drops below the set reference value, flip-flop 3
1 is inverted, its Q output becomes a low level, and its output becomes a high level and is switched to the receiving output of the glass antenna wire 4. The output of flip-flop 31 is also applied to automatic level setting circuit 28, and its operating mode is switched so that this circuit detects a decrease in the reception level of antenna wire 4. Therefore, next time the reception level of the glass antenna wire 4 falls below the set reference level, the automatic level setting circuit 28 detects this, and the antenna switching control circuit 30 switches the switching pulse d again based on the detection output b. This pulse d inverts the flip-flop 31. Therefore, the switch circuit 17 is switched to the pole antenna 1 side.

As a result, diversity reception is performed in which the antenna output is always switched to a higher antenna output than the set reception level.

Furthermore, in the embodiment shown in FIG. 6, variations in multipath distortion are detected and reception can be performed by switching to the reception output with less distortion. In other words, the output of the front end and IF circuit 24 is 19K.
It is also supplied to a Hz bandpass filter 32, where the stereo pilot signal is extracted. This pilot signal is applied to a level fluctuation detection circuit 33. If the received signal is distorted by multipath, the pilot signal will also be distorted, so by detecting the level variation (distortion component variation),
It is possible to detect increases and decreases in multipath distortion due to movement of the receiving point.

When the multipath distortion increases by more than a certain amount, the high-frequency cut control filter 25 is operated on the output e of the level fluctuation detection circuit 33, and the high-frequency distortion component of the detection output is cut and given to the multiplexer 27. In addition, the level fluctuation detection circuit 33
The output e is also sent to the antenna switching control circuit 30, where a switching pulse d is formed as described above, and the output is switched to the other reception output in the same way as in the case of reception level fluctuation. As a result, a received signal with less multipath distortion can be obtained. Note that the antenna switching control circuit 30 forms a switching pulse d when either one of the outputs b and e of the automatic level setting circuit 28 and the level fluctuation detection circuit 33 is input.
In other words, the switching pulse d is determined by the OR logic of the signals b and e.
is created. In addition, in order to prevent input switching due to reception level fluctuations during tuning, the reception level detection signal a obtained from the front end and IF circuit 24 is given to the antenna switching control circuit 28 as an operation prohibition signal. Therefore, the formation of the switching pulse d is prohibited in the weak electric field between stations during channel selection.

In order to make the diversity receiving circuit shown in FIG. 6 work effectively, it is desirable to insert an amplifier or an attenuator into one or both of the output circuits of the pole antenna and the glass antenna wire to adjust the gain. Preferably, the gain is adjusted so that the average receiving sensitivity of the pole antenna and the glass antenna is within 6 dB.

As mentioned above, this invention uses a pole antenna erected on the side of the car and an antenna wire attached to the window glass to perform diversity reception. Even if there are fluctuations in the reception level (fading, etc.) or fluctuations in the reception level (directional characteristics) due to changes in the reception direction, it is possible to select the better reception output and obtain a high-quality reception signal. In particular, since the angular positions of the dip points of the directional characteristics of the pole antenna and the glass antenna wire are greatly different, directional diversity reception can be performed effectively, and the effect of spatial diversity reception due to the difference in antenna position can also be achieved. can get.

In addition, the antenna wire provided on the window glass uses a very simple conductor pattern with a figure-eight directional pattern that is complementary to that of the pole antenna, which reduces visibility obstruction caused by the conductor and prevents fogging. When a heater wire is installed, a sufficient anti-fog area can be secured, and a simple combination of a glass antenna and one pole antenna can be used.
Extremely good reception performance can be obtained.

[Brief explanation of the drawing]

Figures 1A and 2A are side views of a car using a pole antenna, Figures 1B and 2B are directional characteristic graphs of the antennas in Figures 1A and 2A, respectively, and Figures 3A and 3B are 3B and 4B are front views of the front window glass and rear window glass of an automobile to which antenna wires are attached, respectively, and the directional characteristic graphs of the glass antenna of FIGS. 3A and 4A are shown in FIGS. 5a-5. c is a graph showing the measured data of the directivity characteristics of the pillar antenna in Fig. 1A and the windshield antenna in Fig. 3A, respectively;
The figure is a block circuit diagram of an FM receiver used in the receiving system of the present invention. In addition, in the symbols used in the drawings, 1...
...Pole antenna, 4...Glass antenna wire,
17... changeover switch circuit, 28... automatic level setting circuit, 30... antenna switching control circuit.

Claims (1)

[Scope of utility model registration request] A pole antenna erected upward on the side of a car, an antenna wire provided on a window glass and having a figure-8 directivity characteristic that produces a gain dip in the front-rear direction of the car, and the above-mentioned pole antenna and antenna wire. 1. A receiver for an automobile, comprising means for detecting a radio wave reception state of the detector, and a changeover switch means for selecting and receiving the output of the pole antenna or the antenna wire according to the output of the detecting means.