JP2000307491A - Radio broadcast receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the radio broadcast receiver, which has a one-system diversity function, to receive a broadcast wave by using an antenna in the best reception state even when reception environment is in a weak electric field area. SOLUTION: An electric filed intensity detector 28 detects the intensity of a circumferential electric field by checking the output level of an amplifier as to an intermediate frequency measured by an S meter 27. When the electric field intensity is weak, a noise switch 29 lowers the gain of a noise amplifier 29. Further, a time constant switch 30 shortens the time constant of an AGC signal generator 22. Consequently, the dynamic range of the AGC signal generator 22 is apparently expanded to quicken its response.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radio broadcast receiver having a single system diversity function.

[0002]

2. Description of the Related Art One of two antennas is selected in accordance with a reception state in order to maintain a good reception state while a broadcast wave (especially an FM wave) is moving, and broadcasting is performed using the selected antenna. In-vehicle radio receivers having a so-called one-system diversity function for receiving waves have become widespread.

FIG. 4 is a schematic block diagram of a conventional on-vehicle radio receiver with a single system diversity function.

[0004] In FIG. 4, one of the antennas 10 a and 10 b is selected by a switch 32. The radio signals received by the selected antennas 10a and 10b are high-frequency amplified by the high-frequency amplifier 11 and input to the mixer 12. Then, based on the signal of the frequency generated by the local oscillator 17, the signal is converted into an intermediate frequency signal. For example, the signal is converted into an intermediate frequency signal having a difference frequency between the frequency of the signal output from the high-frequency amplifier 11 and the frequency of the signal output from the local oscillator 17.

[0005] The frequency of the signal generated by the local oscillator 17 is determined in accordance with an instruction from the microcomputer 18. When receiving a tuning instruction from the operator via the operation panel 24, the microcomputer 18 receives a signal of a frequency necessary to extract an intermediate frequency signal having a predetermined frequency from a signal of the frequency specified by the tuning instruction. To the local oscillator 17 to generate Further, the frequency specified by the tuning instruction is displayed on the display panel 25.

Next, the intermediate frequency signal output from the mixer 12 is input to an intermediate frequency amplifier 13 via a filter 19, where the intermediate frequency component is amplified. Then, the signal is demodulated by the demodulator 14 into an audio signal.
Is amplified by the speaker 16 and output from the speaker 16 as audio.

[0007] The audio signal demodulated by the demodulator 14 is also input to a high-pass filter 20 to extract a noise component contained in the audio signal. After the extracted noise component is amplified by the noise amplifier 21, the switching controller 26
Is input to Here, the gain of the noise amplifier 21 is determined by the AGC signal device 22 that generates the AGC signal in accordance with the level of the noise component output from the noise amplifier 21 and the generated AGC signal.
Feedback control is performed by a gain controller 23 that controls the gain of the noise amplifier 21 according to the AGC signal.

Now, the switching controller 26 is provided with the noise amplifier 2
An antenna 10 has a counter that counts the number of noise components output from the antenna 10. If the counter counts a predetermined number or more within a predetermined time, the reception state is determined to be bad, and the selected antenna 10
An instruction is issued to the switch 32 to change a and 10b. In response to this, the switch 32 selects the antenna 10a to be selected,
Switch 10b.

As described above, by selecting one of the antennas 10a and 10b according to the reception state, it is possible to maintain a good reception state while moving.

However, when the reception environment is in a weak electric field region where radio waves are extremely weak, the noise component included in the audio signal demodulated by the demodulator 14 extremely increases. That is, the S / N ratio is extremely deteriorated. For this reason, the level of the noise component output from the noise amplifier 21 exceeds the dynamic range of the AGC signal generator 22, and the AGC signal generator 22 receives an abrupt increase in the noise component output from the noise amplifier 21. In some cases, the tracking cannot be performed, and the gain of the noise amplifier 21 cannot be controlled normally. In this case, a normal selection switching operation of the antennas 10a and 10b by the switching controller 26 cannot be performed, and a situation occurs in which the switching of the antennas 10a and 10b is repeatedly performed regardless of the reception state. In this case, a good reception state cannot be maintained.

Therefore, conventionally, the antennas 10a, 10a
As b, an S-meter 27 for measuring the output signal level of the intermediate-wave amplifier 13 and a measurement by the S-meter 27 while using a sensitive main antenna on one side and using a sub-antenna with lower sensitivity than the main antenna on the other side A main hold circuit 31 for fixing the antenna switching control by the switching controller 26 to the main antenna according to the result;
When the measurement result of the meter 27 indicates that the reception environment is in the weak electric field region, the main hold circuit 31 controls the main antenna to be selected.

[0012]

Incidentally, a printed sheet-shaped antenna is sometimes used as an antenna of an on-vehicle radio receiver. This sheet-shaped antenna is often attached to the rear glass of a vehicle. However, in some vehicles such as so-called RV vehicles, the rear pillars tend to stand up, and the area of the rear glass is smaller than vehicles such as sedans. For this reason, in consideration of the space for applying a heating wire for preventing fogging, there is a case where a space for attaching a sheet-like antenna to the rear glass cannot be secured. Therefore, in such vehicles, an example of attaching a sheet-like antenna to both left and right side glasses is increasing.

In the conventional on-vehicle radio receiver with one-system diversity function shown in FIG. 4, when one sheet is used as a main antenna and the other is used as a sub-antenna and sheet-like antennas are attached to left and right side glasses, rear glass is used. The directivity in the left-right direction is stronger than when the antenna is attached. Therefore, the following problem occurs.

That is, as shown in FIG. 5, when a broadcast wave of a broadcast station to be tuned arrives from the side where the sub-antenna is attached, the reception situation is better when the sub-antenna is used than for the main antenna. May be improved. However, in the conventional in-vehicle radio receiver with one-system diversity function shown in FIG. 4, when the reception environment is in a weak electric field region, the antenna used by the main hold circuit 31 is fixed to the main antenna. Cannot be used, and the receiving situation cannot be improved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radio broadcasting receiver having a single system diversity function, even if the reception environment is in a weak electric field region, the reception condition is the highest. Broadcast waves can be received using a good antenna.

[0016]

In order to solve the above-mentioned problems, the present invention selects one of at least two antennas according to a reception state, and receives a broadcast wave using the selected antenna. A wireless broadcast receiver having a one-system diversity function, comprising: a noise component detection unit that detects and outputs a noise component included in an audio signal obtained by demodulating a received broadcast wave; and a noise component detection unit. The number of output noise components is measured, and when a measured value per a predetermined time exceeds a predetermined threshold value, an antenna switching unit that switches an antenna to be used from the currently used antenna to another antenna, First detection for feedback-controlling the noise component detection sensitivity of the noise component detection unit in accordance with the level of the noise component output from the noise component detection unit Degree control means, electric field strength detecting means for detecting the surrounding electric field strength, and when the electric field strength detecting means detects an electric field strength equal to or less than a predetermined level, the noise component detection sensitivity of the noise component detecting means is increased. Lower second
And a detection sensitivity control means.

Here, for example, the noise component detecting means includes a high-pass filter to which an audio signal obtained by demodulating a received broadcast wave is input, and a noise amplifier that amplifies an output (noise component) of the high-pass filter. The first detection sensitivity control means comprises: an AGC signal generator for generating an AGC signal such that the level becomes constant in accordance with the level of the noise component amplified by the noise amplifier; and A gain controller for controlling the gain of the noise amplifier according to the AGC signal generated by the signal generator. Further, the second detection sensitivity control means includes: a gain switch for lowering the gain of the noise amplifier when the electric field intensity detection means detects an electric field intensity equal to or lower than a predetermined level; A response characteristic switch for increasing the response (specifically, a time constant) of the AGC signal generator when detecting an electric field intensity below the level.

According to the present invention, when the electric field intensity detecting means detects the electric field intensity below a predetermined level,
When the reception environment is in the weak electric field region, the noise component detection sensitivity of the noise component detection unit is forcibly reduced by the second detection sensitivity control unit. By doing so, the dynamic range in the first detection sensitivity control means can be apparently expanded. For this reason, even in the weak electric field region where the S / N ratio of the noise component included in the audio signal sharply deteriorates, the feedback control by the first detection sensitivity control means can be performed normally, and therefore, the most significant It is possible to receive broadcast waves using a good antenna.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an in-vehicle radio receiver with a single-system diversity function will be described below as an example.

FIG. 1 is a schematic configuration diagram of an on-vehicle radio receiver with a single system diversity function to which an embodiment of the present invention is applied. In FIG. 1, components having the same functions as those of the conventional in-vehicle radio receiver with one-system diversity function shown in FIG. 4 are denoted by the same reference numerals.

In FIG. 1, one of the antennas 10a and 10b is selected by the switch 32. The radio signals received by the selected antennas 10a and 10b are high-frequency amplified by the high-frequency amplifier 11 and input to the mixer 12. Then, based on the signal of the frequency generated by the local oscillator 17, the signal is converted into an intermediate frequency signal. For example, the signal is converted into an intermediate frequency signal having a difference frequency between the frequency of the signal output from the high-frequency amplifier 11 and the frequency of the signal output from the local oscillator 17.

The frequency of the signal generated by the local oscillator 17 is determined according to an instruction from the microcomputer 18. When receiving a tuning instruction from the operator via the operation panel 24, the microcomputer 18 receives a signal of a frequency necessary to extract an intermediate frequency signal having a predetermined frequency from a signal of the frequency specified by the tuning instruction. To the local oscillator 17 to generate Further, the frequency specified by the tuning instruction is displayed on the display panel 25.

Next, the intermediate frequency signal output from the mixer 12 is input to the intermediate frequency amplifier 13 via the filter 19, where the intermediate frequency component is amplified. Then, the signal is demodulated by the demodulator 14 into an audio signal.
Is amplified by the speaker 16 and output from the speaker 16 as audio.

The audio signal demodulated by the demodulator 14 is also input to a high-pass filter 20, where noise components included in the audio signal are extracted. After the extracted noise component is amplified by the noise amplifier 21, the switching controller 26
Is input to Here, the gain of the noise amplifier 21 controls the gain of the AGC signal device 22 that generates an AGC signal in accordance with the level of the noise component output from the noise amplifier 21, and the gain of the noise amplifier 21 according to the generated AGC signal. The gain controller 23 performs feedback control so that the level of the noise component output from the noise amplifier 21 becomes constant.

The switching controller 26 includes the noise amplifier 2
An antenna 10 has a counter that counts the number of noise components output from the antenna 10. If the counter counts a predetermined number or more within a predetermined time, the reception state is determined to be bad, and the selected antenna 10
An instruction is issued to the switch 32 to change a and 10b. In response to this, the switch 32 selects the antenna 10a to be selected,
Switch 10b.

As described above, by selecting one of the antennas 10a and 10b according to the reception state, it is possible to maintain a good reception state while moving.

As described above, when the reception environment is in the weak electric field region, the S / N ratio of the noise component included in the audio signal demodulated by the demodulator 14 is extremely deteriorated. For this reason, the level of the noise component output from the noise amplifier 21 exceeds the dynamic range of the AGC signal generator 22, and the AGC signal generator 22 cannot follow, and the gain of the noise amplifier 21 cannot be controlled normally. In this case, the switching controller 2
6 cannot perform the normal selection switching operation of the antennas 10a and 10b, and the switching of the antennas 10a and 10b is repeatedly performed regardless of the reception state. In this case, a good reception state cannot be maintained.

Therefore, in the present embodiment, the output signal level of the intermediate wave amplifier 13 measured by the S meter 27 is monitored by the electric field intensity detector 28, and when the signal level is lower than a predetermined level, Is a weak electric field region, the noise sensitivity switch 29
The noise amplifier 21 is controlled so as to lower the gain of the noise amplifier 21 by a predetermined level, and the time constant for determining the responsiveness (following property) of the AGC signal generator 22 is shortened by the time constant switch 30. The AGC signal generator 22 is controlled.

By doing so, the AGC signal generator 2
2 can be apparently expanded, and the responsiveness of the AGC signal generator 22 can be increased. Therefore, even when the S / N ratio of the noise component included in the audio signal is extremely deteriorated in the weak electric field region, the feedback control of the noise amplifier 21 by the AGC signal generator 22 and the gain controller 23 is performed normally. Therefore, it is possible to receive broadcast waves using the antennas 10a and 10b having the best reception status.

Next, a specific circuit configuration of a main part of the on-vehicle radio receiver having the one-system diversity function shown in FIG. 1 will be described. FIG. 2 is a diagram showing an example of a specific circuit configuration of a main part of the in-vehicle radio receiver with a single system diversity function shown in FIG.

Here, the tuner IC has a structure corresponding to the high frequency amplifier 11, the mixer 12, the intermediate frequency amplifier 13, the local oscillator 17, the demodulator 14, the S meter 27, etc. shown in FIG. However, parts that cannot be built into IC chips such as inductors, capacitors, and crystal oscillators are excluded). The diversity IC has a configuration corresponding to the switching controller 26, the noise amplifier 21, the AGC signal generator 22, the gain controller 23, and the like shown in FIG. 1 (however, ICs such as inductors and capacitors are included). Excluding the parts that cannot be made into chips).

In FIG. 2, A, B, C, D
The unit, the E unit, the F unit, the G unit, the H unit, and the I unit are respectively a switch 32, a switch controller 26, an AGC signal generator 22, a noise amplifier 21, a gain controller 23, a high-pass Filter 20, electric field intensity detector 28, time constant switch 30,
And a configuration corresponding to the noise sensitivity switch 29.

The signal output from the S-meter output of the tuner IC is input to the bases of the transistors in the H section and the I section after the level is controlled in the G section. Therefore, when the level of the signal output from the S-meter output of the tuner IC is low, that is, when the reception environment is in the weak electric field region, the transistors of the H part and the I part are turned off, and the time constant of the AGC is determined. The capacitance of the capacitor and the capacitor that determines the gain of the noise amplification is reduced. Thereby, the responsiveness of the AGC signal generator 22 (corresponding to the part C) is increased, and the noise amplifier 21 (corresponding to the part D) is increased.
Lower the gain at

Next, the effect of the in-vehicle radio receiver with a single system diversity function to which the present embodiment having the above configuration is applied will be described with reference to the drawings. FIG.
An example of the relationship between the movement of the vehicle (running time) and the reception status at each antenna (S-meter output voltage) when two printed sheet antennas are attached to both left and right side glasses of the vehicle is shown. Where A and B
The section indicates that the reception condition of the sub-antenna is better than that of the main antenna.

In the conventional on-vehicle radio receiver with one-system diversity function shown in FIG. 4, when the S-meter output voltage is lower than a predetermined level, that is, when the reception environment is in a weak electric field region, the antenna used is the main antenna. It is fixed to. For this reason, in the sections A and B, the use of the sub antenna cannot be used even though the reception condition is improved when the sub antenna is used.

On the other hand, in the in-vehicle radio receiver with a single-system diversity function to which the present embodiment shown in FIG. 1 is applied, as described above, even if the S-meter output voltage is lower than a predetermined level, the reception status is not changed. It is possible to select an optimal antenna according to the situation. Therefore, the sub-antenna can be used in the A section and the B section.

The embodiment of the present invention has been described above.

In this embodiment, when the reception environment is in the weak electric field region, the gain of the noise amplifier 21 is lowered by a predetermined level and the time constant of the AGC signal generator 22 is shortened by a predetermined level. By controlling the gain of the noise amplifier 21 and the time constant of the AGC signal generator 22 to other stages according to the surrounding electric field strength, the gain of the noise amplifier 21 decreases stepwise as the surrounding electric field strength decreases. In addition, the time constant of the AGC signal generator 22 may be gradually reduced.

Although the present embodiment has been described with respect to the case where there are two antennas, it is needless to say that the present invention can be similarly applied to a case where there are three or more antennas.

Furthermore, in the present embodiment, the case where the present invention is applied to an in-vehicle radio receiver with a single system diversity function has been described, but the present invention is not limited to this. As long as it has a single-system diversity function, it can be widely applied to various on-vehicle or indoor radio broadcast receivers such as television receivers.

[0041]

As described above, according to the present invention,
In a wireless broadcasting receiver having a one-system diversity function, a broadcast wave can be received using an antenna having the best reception status even when the reception environment is in a weak electric field region.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an in-vehicle radio receiver with a single system diversity function to which an embodiment of the present invention is applied.

FIG. 2 is a diagram showing an example of a specific circuit configuration of a main part of the in-vehicle radio receiver with a one-system diversity function of the embodiment shown in FIG. 1;

FIG. 3 shows an example of the relationship between vehicle movement (running time) and reception conditions at each antenna (S-meter output voltage) when two printed sheet antennas are attached to both left and right side glasses of the vehicle. FIG.

FIG. 4 is a schematic configuration diagram of an in-vehicle radio receiver with a single system diversity function conventionally used.

FIG. 5 shows a problem in the case where the main antenna and the sub-antenna are attached as printed sheet antennas to both right and left side glasses of the vehicle in the conventional on-vehicle radio receiver with one-system diversity function shown in FIG. It is a figure for explaining.

[Explanation of symbols]

10a, 10b: antenna, 11: high frequency amplifier,
12: mixer 13: intermediate frequency amplifier, 14: demodulator, 15: amplifier, 16: speaker 17: local oscillator, 18: microcomputer, 19: filter 20: high-pass filter, 21: noise amplifier, 2
2: AGC signal generator 23: Gain controller, 24: Operation panel, 25: Display panel 26: Switching controller, 27: S meter, 28: Electric field strength detector 29: Noise sensitivity switcher, 30: Time constant switch Bowl, 3
2: Switch

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takayuki Hirota 2-4991 Hironodai, Zama-shi, Kanagawa F-term in Xanavi Informatics Co., Ltd. 5K059 CC03 DD03 DD09 DD12 DD16 DD22 DD27 EE03

Claims (2)

[Claims] 1. A radio broadcast receiver having a single-system diversity function for selecting one of at least two antennas according to a reception state and receiving a broadcast wave using the selected antenna. A noise component detection unit that detects and outputs a noise component included in an audio signal obtained by demodulating a broadcast wave; and measures a number of noise components output from the noise component detection unit, and performs measurement per predetermined time. When the value exceeds a predetermined threshold, the antenna switching means for switching the antenna to be used from the currently used antenna to another antenna, and according to the level of the noise component output from the noise component detection means, First detection sensitivity control means for feedback-controlling the noise component detection sensitivity of the noise component detection means, and an electric field strength detection means for detecting a surrounding electric field strength. Output means, and second detection sensitivity control means for lowering the noise component detection sensitivity of the noise component detection means when the electric field strength detection means detects an electric field strength of a predetermined level or less. A radio broadcast receiver characterized by the following. 2. The radio broadcast receiver according to claim 1, wherein said noise component detection means is a high-pass filter to which an audio signal obtained by demodulating a received broadcast wave is inputted.
A noise amplifier for amplifying an output (noise component) of the high-pass filter, wherein the first detection sensitivity control means makes the level constant in accordance with the level of the noise component amplified by the noise amplifier. An AGC signal generator that generates an AGC signal as described above,
A gain controller for controlling the gain of the noise amplifier in accordance with the AGC signal generated by the AGC signal generator, wherein the second detection sensitivity control means is configured such that the electric field strength detection means A gain switch for lowering the gain of the noise amplifier when detecting the intensity; and increasing the response of the AGC signal generator when the electric field intensity detecting means detects an electric field intensity equal to or lower than a predetermined level. And a response characteristic switch.