JPH0619333U - FM modulator with frequency characteristic correction circuit - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] A flat reproduction frequency characteristic can be obtained by providing a correction circuit in the FM modulator. [Structure] 1kHz as mid-range and 10 as treble
After selecting kHz, both frequencies are extracted from the output audio signal of the CD player or the like by the band pass filters 4 and 5, FM
Similarly, both frequencies are extracted by the bandpass filters 8 and 9 from the electrical output that is converted into the FM wave by the modulator 7 and passed through the circuit of the FM radio receiver 10, and both are input to the frequency characteristic detection circuit 6 for the arithmetic processing. 10 for 1 kHz
The attenuation amount of kHz is calculated, the correction control signal is output, and the frequency characteristic correction circuit 3 performs the correction.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an in-vehicle audio device, and more particularly to a device for reproducing an output of an audio reproducing device such as a CD player by converting it into an FM wave by an FM modulator and inputting the FM wave into an in-vehicle radio receiver.

[0002]

[Prior art]

 A configuration in which an FM modulator is used to input an output audio signal from a CD player or the like from an antenna circuit of a genuine radio receiver provided in a vehicle and to reproduce by using the FM receiver circuit of the radio receiver has been conventionally used. .

In this case, the influence of the audio frequency characteristic of the FM receiving circuit of the radio receiver used cannot be ignored. That is, in FM radio, the high frequency range is normally cut around 15 kHz so as not to affect the 19 kHz pilot signal of FM stereo broadcasting, so flat characteristics should be expected up to this frequency. However, there are radio receivers whose frequency characteristics are not flat even within the above range due to variations in the performance of the radio receivers and differences in the design stance.

Therefore, the output audio signal of the CD player or the like is simply converted into the FM broadcast format by the FM modulator, input from the antenna circuit of the radio receiver, and reproduced by using the FM reception circuit of the radio receiver. With such a structure, it is not possible to reproduce the high quality sound of a CD. Therefore, some FM modulators have been equipped with a circuit that corrects high frequencies, but the high frequency characteristics of the radio receiver to be used are unclear only by using this circuit. It is not something that can be done.

[0005]

[Problems to be solved by the device]

 In the present invention, the FM modulator is connected to an FM radio receiver having any frequency characteristic by improving the above-mentioned drawbacks and providing the FM modulator with a function of automatically correcting the frequency characteristic of the radio receiver. Even so, it is intended to obtain a flat frequency characteristic.

[0006]

[Means for Solving the Problems]

 In the present invention, the above-mentioned problem is solved by the present invention, in which the output signal and the respective band-pass filters for selectively extracting one characteristic frequency from the middle tone portion and the high tone portion of the output signal of the audio device to which the FM modulator is connected are respectively extracted. A band pass filter for selectively extracting the specific frequency from the mid-tone part and the treble part of the electrical output converted into the FM wave by the FM modulator included in the FM modulator and reproduced by the FM radio receiver; A frequency characteristic detecting circuit for processing the outputs of the four band-pass filters and outputting the result as a frequency characteristic correcting signal. It is configured so as to prepare for the preceding stage of the M modulation section, or is selected from the middle and treble sections respectively. An oscillator that generates two frequencies at the same level at the same level, synthesizes them, and outputs, and an electrical output regenerated by the FM radio receiver after the oscillator output is converted into an FM wave by an FM modulator included in the FM modulator. Of each of the bandpass filters for selectively extracting the two frequencies from the midtone and treble of the above, and the voltage levels of the two frequencies output by the bandpass filter are compared, and the difference is output as a frequency characteristic correction signal. Means and the frequency characteristic correction circuit that operates by the frequency characteristic correction signal is provided in the preceding stage of the FM modulator.

[0007]

[Action]

 By selecting 1 kHz as the midtone part of the audio frequency range and 10 kHz as the treble part, both frequencies are extracted from the output audio signal of the CD player or the like by a bandpass filter, and on the other hand, converted to FM waves and the circuit of the FM radio receiver is converted. Similarly, both frequencies are extracted from the passed electrical output by a bandpass filter, and both are input to the frequency characteristic detection circuit. By this circuit, arithmetic processing is performed and the attenuation amount of 10 kHz relative to 1 kHz is calculated. , The correction control signal is output, and the frequency characteristic correction circuit performs appropriate correction to obtain a flat characteristic. In another embodiment, a signal obtained by oscillating and synthesizing both frequencies of 1 kHz and 10 kHz at the same level, and using this as an FM wave, 1 kHz and 10 kHz are extracted from the output signal through the FM radio circuit, By outputting the difference as a correction control signal by the comparator, it is possible to obtain a flat frequency characteristic similar to that described above.

[0008]

【Example】

 Although the drawings are all related to the present invention, FIGS. 1 and 2 show different embodiments. The first embodiment of FIG. 1 will be described. An FM modulator 1 is a frequency characteristic correction circuit 3 that receives an audio output signal of a CD player 2 as an example of an audio device to be connected, and an FM modulation circuit that modulates the output signal into FM and outputs an FM wave. 7, a 1 kHz bandpass filter 8 connected to the electrical output of the FM radio receiver 10, a similar 10 kHz bandpass filter 9, a frequency characteristic detection circuit 6 to which the outputs of the two bandpass filters are input, and a CD player A bandpass filter 4 for extracting a frequency of 1 kHz from the audio output signal 2 and inputting it to the frequency characteristic detection circuit 6 and a 10 kHz bandpass filter 5 are also provided. The frequency characteristic detection circuit 6 calculates the input voltage data from each of the band pass filters and inputs the result to the frequency characteristic correction circuit 3 as a correction control signal. Reference numeral 11 is a speaker connected to the output of the FM radio receiver 10.

In such a configuration, the frequency components of 1 kHz and 10 kHz are extracted from the output audio signal of the CD player 2 by the bandpass filters 4 and 5. These voltages are VCD1K and VCD10K, respectively. On the other hand, also from the output of the FM radio receiver 10, frequency components of 1 kHz and 10 kHz are extracted by the bandpass filters 8 and 9. Let this voltage be VTU1K and VTU10K, respectively.

A level difference is obtained by subtracting VTU1K from VCD1K, and an attenuation amount of 10 kHz can be detected by subtracting the level difference from the difference between VCD10K and VTU10K. That is, since these voltages are respectively input to the frequency characteristic detection circuit 6, the following calculation is performed by this circuit using this. Attenuation at 10 kHz = (VCD10K-VTU10K)-(VCD1K-VTU1K)

Then, the frequency characteristic detection circuit 6 outputs a signal corresponding to the numerical value of the attenuation amount to the frequency characteristic correction circuit 3 to correct the high frequency characteristic.

FIG. 2 shows a second embodiment of the present invention. The description of the same parts as those in the first embodiment is partially omitted and the same reference numerals are used. The FM modulator 20 has a comparator 12 for inputting the outputs of the band pass filters 8 and 9 for extracting frequencies of 1 kHz and 10 kHz from the electrical output of the radio receiver 10, a latch circuit 13 connected to this output, 1 kHz and 10 kHz. It is connected to an oscillator 15 that oscillates a signal (both frequencies are at the same level) and outputs a combined signal, a controller 14 that controls the operations of the comparator 12 and the oscillator 15, and a controller 14. A frequency characteristic correction switch 16 is provided.

The operation of the circuit having the above configuration is as follows. That is, when the frequency characteristic correction switch 16 is turned on, the control section 14 operates the oscillator 15 and puts the latch circuit 13 into the stirrup state. The combined signal of 1 kHz and 10 kHz, which is the output of the oscillator 15, is uncorrected in this state, and is modulated into an FM RF signal by the FM modulation circuit 7 via the frequency characteristic correction circuit 3 and the FM radio receiver 10 Is reproduced as an audio signal. By inputting both voltages of the output V1K of 1 kHz and the output V10K of 10 kHz extracted from this signal by the bandpass filters 8 and 9 to the comparator 12, the change amount at 10 kHz is output (as described above). Since the two frequencies of the oscillator 15 are at the same level), the output thereof is held by the latch circuit 13 and is output from the same circuit as a frequency characteristic correction amount control signal.

The frequency characteristic correction amount control signal is input to the frequency characteristic correction circuit 3, and the circuit performs appropriate frequency characteristic correction. After that, the control unit 14 stops the oscillator 15 and puts the latch circuit 13 into the output hold state. The same effect can be obtained even if the latch circuit 13 is configured by a sample hold circuit.

[0015]

[Effect of device]

 As described above, according to the present invention, the frequency characteristic of the radio receiver, which is a problem when trying to reproduce a CD player or the like by the FM modulator, is provided in the FM modulator by providing the frequency characteristic correction circuit. Since it is configured to detect and correct the frequency characteristics of the radio receiver side, a flat reproduction frequency characteristic can be obtained regardless of variations in the characteristics of the radio receiver or differences in design policies. It has a great effect when it is applied to an audio device mounted on a vehicle.

[Brief description of drawings]

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

FIG. 2 is a block diagram of another embodiment of the present invention.

[Explanation of symbols]

 1 FM modulator 2 CD player 3 Frequency characteristic correction circuit 4 1 kHz bandpass filter 5 10 kHz bandpass filter 6 Frequency characteristic detection circuit 7 FM modulation circuit 8 1 kHz bandpass filter 9 10 kHz bandpass filter 10 FM radio receiver 12 Comparator 13 Latch Circuit 14 Control unit 15 Oscillator 16 Frequency characteristic correction switch 20 FM modulator

Claims (2)

[Scope of utility model registration request] 1. An apparatus for converting an audio signal into an FM wave by an FM modulator, inputting the FM signal to an FM radio receiver and reproducing the FM wave, from a middle tone portion and a high tone portion in an output signal of an audio device connected to the FM modulator. Each band pass filter for selectively extracting one specific frequency, and the output signal is converted to an FM wave by an FM modulator included in the FM modulator.
Each of the bandpass filters for selectively extracting the specific frequency from the midrange part and the high range part of the electrical output reproduced by the M radio receiver and the outputs of the four bandpass filters are arithmetically processed, and A frequency characteristic detection circuit that outputs the result as a frequency characteristic correction signal is provided,
An FM modulator characterized in that a frequency characteristic correction circuit that operates according to this frequency characteristic correction signal is provided in the preceding stage of the FM modulation section. 2. An apparatus for exchanging an audio signal into an FM wave by an FM modulator and inputting and reproducing to an FM radio student machine, wherein two frequencies selected from a middle tone portion and a high tone portion are simultaneously generated at the same level. An oscillator that synthesizes and outputs, and the oscillator output is the F
Band-pass filters for selectively extracting the two frequencies from the mid-tone part and the treble part of the electrical output converted into FM waves by the FM modulator included in the M modulator and reproduced by the FM radio receiver; A means for comparing the voltage levels of two frequencies output by the band pass filter and outputting the difference as a frequency characteristic correction signal is provided, and a frequency characteristic correction circuit which operates by this frequency characteristic correction signal is provided at the front stage of the FM modulator. An FM modulator characterized by being equipped with.