JPH01119124A - On-vehicle radio receiver - Google Patents

Abstract

PURPOSE:To maintain stable sound quality and the static feeling of an image even at the time of switching an antenna by changing an auto gain control(AGC) characteristic corresponding to respective sensitivity of plural antennas. CONSTITUTION:A third amplifier circuit 12c having an amplification characteristic to correct the difference of gain characteristics based on the difference of the sensitivity of a pole antenna 1 and a glass antenna 2 is provided at a high frequency amplifier 12. And it is constituted so that the third amplifier circuit 12c is operated only when reception is performed by the glass antenna 2 with comparatively low sensitivity and it is not operated when the reception is performed by the pole antenna 1 with comparatively high sensitivity. Therefore, it is possible to change the AGC characteristic so as to correct the difference of a gain characteristic based on the difference of the sensitivity of the antennas 1 and 2. In such a way, it is possible to keep the level of auto tone control (ATC) and a separation level constant even at the time of switching the antennas 1 and 2 according to the generation of multipass distortion, and to obtain the stable sound quality and the static feeling of the image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vehicle radio receiver equipped with a diversity reception system.

[Prior Art] As is well known, the reception condition of a vehicle radio receiver is greatly affected by the movement of the vehicle, especially when the vehicle is traveling in a departure zone or between buildings in a city. Noise is generated due to sudden changes in the strength of radio waves.

In particular, when receiving FM broadcasting, since the radio waves travel in a straight line, the radio waves transmitted from the transmitting antenna 54 are reflected by, for example, a building 55, as shown in FIG.
The receiving antennas 51 and 52 of the vehicle 53 receive not only the direct waves from the transmitting antenna 54 but also the reflected waves. Since there is a slight difference in the arrival time to the receiving antenna 51, 52 between these reflected waves, or between the direct wave and the reflected wave, they interfere with each other, causing a phase shift in the received radio waves. There is a problem in that so-called multipath distortion occurs in the received audio, making it difficult to listen to the broadcast.

As an effective countermeasure against the problem of noise generation and multipath distortion caused by sudden changes in the strength of radio waves as described above, a radio receiver in a vehicle is equipped with a ring antenna, and the reception condition is always maintained. The so-called diversity reception system, in which the reception circuit is switched so that reception can be performed by the antenna with the better signal, is generally well known (see, for example, Japanese Utility Model Application Publication No. 58-64110).

According to this diversity reception system, if multipath distortion occurs during reception with the negative antenna, the reception circuit is immediately switched to receive with the other antenna, so the reception condition is always better. can be received using the antenna.

However, when installing multiple antennas on a vehicle, due to constraints in the design and layout of the vehicle, it is difficult to install antennas with the same sensitivity characteristics at locations where the reception conditions are the same. , a difference occurs in the receiving sensitivity of each antenna.

That is, it is common practice to provide multiple antennas by, for example, providing a ball antenna in the rear of the vehicle body while embedding a glass antenna in the front windshield, or embedding glass antennas in the front and rear windshields. However, in either case, the receiving sensitivity of each antenna differs because the receiving conditions differ depending on the sensitivity characteristics of the antenna and the mounting location.

By the way, in general, in radio receivers, etc., for the purpose of improving the sound quality of received audio, the frequency range (bass range) and higher frequency range (treble range) are lower than a predetermined frequency range (middle range). By adjusting the frequency characteristics of the audio amplifier, it is possible to perform tone control to obtain stable bass and treble sounds.Auto tone control allows this tone control to be performed automatically. (below,
This is abbreviated as ATC. ) is generally well known.

Also, when receiving stereo broadcasts, the received radio waves are
After it is converted into an audio signal, it is distributed to left and right and sent to an audio amplifier. The degree of separation of the left and right audio signals (separation level) at this time greatly affects the sound spread and three-dimensional effect when listening to stereo broadcasts. For this reason, a multiplex circuit having predetermined separation characteristics is provided in order to distribute audio signals to left and right when receiving stereo broadcasting and to control the separation level.

On the other hand, the gain of the receiver depends on the strength of the input radio wave.
Auto gain control (hereinafter referred to as AGC), which automatically controls the antenna's sensitivity to obtain a constant output level regardless of the strength of the input radio waves, is generally well known. Its control characteristics are determined according to the following.

However, in a vehicle radio receiver equipped with a diversity reception system, if the antenna is switched during broadcast reception due to the occurrence of multipath distortion, the ATC circuit for performing the above ATC is activated. As a result, the ATC level changes and the sound quality fluctuates, making it difficult to hear, and the operation of the multiplex circuit changes the separation level, causing problems in that the sense of sound localization is disturbed.

As a countermeasure to this problem, by installing an antenna amplifier for each antenna separately from the radio receiver, which has gain characteristics that match the sensitivity characteristics of each antenna, the ATC level and separation level can be maintained even when switching antennas. One idea is to keep it constant.

[Problems to be Solved by the Invention] However, in a vehicle interior where available space is limited, providing an antenna amplifier for each antenna separately from the radio receiver hinders the effective use of vehicle interior space. In addition, there was a problem of high cost.

[Purpose of the Invention] This invention was made to solve the above problems, and it is possible to switch between multiple antennas with different sensitivities for reception without providing an antenna amplifier separate from the radio receiver. An object of the present invention is to provide a vehicle radio receiver capable of maintaining stable sound quality and sound image localization by keeping an ATC level and a separation level constant.

[Means for Solving the Problems] Therefore, the present invention provides a radio reception for a vehicle, which is equipped with a plurality of antennas having different sensitivities, and is configured to switch among the plurality of antennas to receive reception when multipath distortion occurs. In the machine, A is set according to the sensitivity of each of the plurality of antennas mentioned above.
The GC characteristics are changed.

[Effects of the Invention] According to the present invention, since the AGC characteristics are changed in accordance with the sensitivity of each of a plurality of antennas, the ATC level remains unchanged even when antennas are switched due to occurrence of multipath distortion. and the separation level can be kept constant. As a result, stable sound quality and sound image localization can be maintained even when switching antennas without providing an antenna amplifier separate from the radio receiver for each antenna.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 3, a vehicle 3 equipped with a vehicle radio receiver (not shown) according to the present embodiment is equipped with a relatively sensitive ball that is provided at the rear of the vehicle body and can be driven to expand and contract in the vertical direction. The vehicle is equipped with an antenna l and a glass antenna 2, which is embedded in a front windshield 4 and has relatively low sensitivity.

Although the vehicle radio receiver according to this embodiment is not specifically shown, as is well known, it is attached to a dash board (not shown) provided at the front of the vehicle 3. It is being

In addition, the above two antennas 1.2 are equipped with a diversity reception system, so that if multipath distortion occurs in one antenna 1 or 2 during broadcast reception, the other antenna 2 or 1 immediately receives the broadcast. By switching the receiving circuit of the radio receiver, the radio receiver can be used in a switched manner.

That is, as shown in FIG. 1, the vehicle radio receiver 10 according to this embodiment has an antenna changeover switch 1! The ball antenna 1 and the glass antenna 2 are connected to terminals 11a and llb of the antenna changeover switch 11, respectively.

A high frequency amplifier I2 that directly amplifies the tuned high frequency signal of the desired broadcasting station is connected to the terminal 11c of the antenna changeover switch 11. An intermediate frequency amplifier 13 and a multiplex circuit 14 are sequentially connected to 2, and the multiplex circuit 14 is connected to a speaker 16 via an audio amplifier 15.

The radio waves received by the ball antenna 1 or the glass antenna 2 are selected from among the radio frequency signals of the desired broadcasting station, tuned, and then suitably amplified by the radio frequency amplifier 12, and then sent to the frequency conversion circuit. (not shown) converts the frequency into a constant intermediate frequency. After this intermediate frequency signal is appropriately amplified by the intermediate frequency amplifier 13, it is converted into an audio signal by a detector (not shown), and then, in the case of stereo broadcasting, it is distributed to left and right by the multiplex circuit 14. At the same time, the signal is sent to the audio amplifier 15 with the separation level controlled according to a predetermined separation characteristic of the multiplex circuit I4.

After being amplified by the audio amplifier 15, the sound is output as audio by the speaker 16.

Further, a multipath detection circuit 17 is connected to the intermediate frequency amplifier 13 and detects multipath distortion when it occurs in the received signal. A switch control circuit 18 is provided.

For example, as shown by the solid line in the figure, there is a ball antenna! If multipath distortion occurs during reception, the multipath detection circuit 17 detects this and sends a detection signal to the switch control circuit 18. As shown, the antenna side terminal 11a of the antenna changeover switch 11,
By switching Ilb from the terminal 11a to the terminal 11b, the antenna to be used can be switched from the ball antenna I to the glass antenna 2.

In addition, in the vehicle radio receiver IO, an ATC circuit 2I that automatically obtains stable bass and treble sounds is connected to an intermediate frequency amplifier 13 and an audio amplifier 15 for the purpose of improving the sound quality of received audio. is established between.

On the other hand, in the vehicle radio receiver IO according to this embodiment, an AGC circuit 22 having predetermined control characteristics is provided between the high frequency amplifier 12 and the intermediate frequency amplifier 13.

According to this AGC circuit 22, when receiving with the ball antenna 1 and when receiving with the glass antenna 2, there is a difference in gain obtained for the same electric field strength depending on the difference in sensitivity between the two antennas.

In other words, as shown in Fig. 2, the gain characteristic of the glass antenna 2, which has relatively low sensitivity, is different from the gain characteristic curve (see the solid line in Fig. 2) of the ball antenna l, which has relatively high sensitivity, on the side where the gain decreases. (in the lower part of FIG. 2), it is shown by a curve (see the broken line in FIG. 2) obtained by parallel movement according to the difference in sensitivity.

By the way, in the vehicle radio receiver 10 according to the present embodiment, the high frequency amplifier 12 includes a plurality of, for example, three amplifier circuits (the amplifier circuit 12a in FIG. 1, the second amplifier circuit 12b, and the third amplifier circuit 12c). Of these, the first amplifier circuit 12
a and the second amplification circuit 12b always perform an amplification action,
Only the third amplifier circuit 12c is connected to the switch control circuit 18, and only when the antenna changeover switch 11 is switched to the terminal 11b side by a signal from the switch control circuit 18, that is, the glass antenna 2 with low sensitivity It is designed to operate and amplify only when receiving data.

The amplification characteristics of the third amplifier circuit 12c are set to be equal to the difference in gain characteristics between the ball antenna l and the glass antenna 2, so that the difference in gain characteristics based on the difference in sensitivity between the ball antenna l and the glass antenna 2 can be corrected.

Therefore, for example, when the receiving antenna is switched from the ball antenna 1 to the glass antenna 2, the third amplification circuit 12c of the high frequency amplifier 12 is simultaneously operated to correct the sensitivity difference between the antennas 1 and 2. When switching the antenna 1.2, the ATC level and the separation level will not be affected since the characteristics will be changed.

As described above, according to this embodiment, the high frequency amplifier 12 includes the third amplifier circuit 12c having an amplification characteristic that corrects the difference in gain characteristics based on the sensitivity difference between the ball antenna 1 and the glass antenna 2. provided, the third amplifier circuit 12c
is activated only when receiving with glass antenna 2, which has relatively low sensitivity, and is inactive when receiving with ball antenna 1, which has relatively high sensitivity, so antenna 1
The AGC characteristics can be changed to correct the difference in gain characteristics based on the sensitivity difference of .degree.2.

Therefore, even when the antennas 1.2 are switched due to the occurrence of multipath distortion, the ATC level and separation level can be kept constant.

As a result, it is possible to obtain stable sound quality and sound image localization even when switching antennas without providing an antenna amplifier separate from the radio receiver 10 for each antenna 1.2.

The above embodiment is an l-tuner type vehicle radio receiver! However, the present invention is applicable not only to the 1-tuner system described above, but also to 2-tuner system vehicle radio receivers by adjusting the control characteristics of each AGC circuit to the sensitivity of each antenna. It can be applied by correspondingly setting appropriately.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit configuration of a vehicle radio receiver according to an embodiment of the present invention, FIG. 2 is a graph showing gain characteristics of a ball antenna and a second glass antenna according to an embodiment of the present invention, and FIG. FIG. 3 is an overall perspective view of a vehicle equipped with a ball antenna and a glass antenna according to an embodiment of the present invention;
FIG. 4 is an overall perspective view of the vehicle showing a state during broadcast reception to explain multipath distortion. 1... Ball antenna, 2... Glass antenna, I
O...Vehicle radio receiver, 2...Antenna selection switch, 12...High frequency amplifier, +2c...Third amplifier circuit, 18...Switch control circuit, 22...AGC circuit.

Claims (1)

[Claims] (1) In a vehicle radio receiver that is equipped with a plurality of antennas with different sensitivities and is configured to switch among the plurality of antennas for reception in response to the occurrence of multipath distortion, A vehicle radio receiver characterized in that control characteristics of auto gain control are changed.