JPS5917906B2 - Reception frequency display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a reception frequency display device that digitally displays the reception frequency of an FM receiver.

Conventionally, as a reception frequency display method for FM receivers, a method has been known in which the oscillation frequency of a local oscillator is counted by a frequency counter preset with a value corresponding to the intermediate frequency, and this counting result is digitally displayed as the reception frequency. It is being

By the way, in this method, as is clear from the principle described above, the display frequency changes in response to the local oscillation frequency, so if a specific broadcast radio wave is received by a receiver to which this method is applied, If the tuning setting position is set slightly above or below the perfect tuning point within the reception band, the reception frequency display will change according to the change in the local oscillation frequency even though the frequency of the broadcast radio wave is fixed. It is something that will happen. In other words, in this method, the relationship between the display frequency and the local oscillation frequency + preset value is proportional as shown in Figure 1 (the frequency display in this case usually displays the first few digits). (from 80), for example, 80.

When receiving a broadcast radio wave of 0 MH2, if the tuning setting position is slightly shifted from the perfect tuning point, even though the frequency of the broadcast radio wave being received is 80.0 MH2,
For example 79, which is different from this frequency.

9MH2, 80.

This results in a frequency display such as 1MH2.

Therefore, while the display is accurate, it is a troublesome display for the recipient because unnecessary display deviations occur. In addition, in this method, since there are variations in the center frequency of the intermediate frequency filter used in the receiver, it is necessary to adjust the preset value according to the intermediate frequency filter.) At this time, the preset value is set finely. (usually at intervals of about 10KH2), resulting in a problem that the counting time of the frequency counter becomes longer. If the center frequency of the intermediate frequency filter deviates from the preset value, there will be an inconvenience that when the tuning is shifted from the perfect tuning point, the range until the frequency display changes will be unbalanced between the upper and lower frequencies. This invention was made to solve the problems of the conventional method described above.Even if the tuning setting state is slightly shifted from the perfect tuning point, the same broadcast will always be broadcast within the range where the same broadcast radio waves are being received. The object of the present invention is to provide a reception frequency display device that can display the frequency of radio waves and can do this without taking any measures such as finely setting the preset value of a frequency counter. be. In order to achieve this object, the present invention controls the displayed frequency by the DC output of a frequency detector. Embodiments of the present invention will be described below with reference to FIGS. 2 to 9.

Figure 2 shows the first example in which this invention is applied to an FM stereo receiver.
This shows an embodiment, and the tuner section 1 includes a high frequency amplification stage 2, a local oscillator 3, a mixing stage 4, an intermediate frequency amplification stage 5,
It is configured with an FM detector (frequency detector) 6 and an FM multiflex stereo demodulation circuit 7,
Since these configurations are the same as those of the conventional ones, a detailed description thereof will not be given here.

According to the present invention, a reception frequency display circuit 8 for digitally displaying the reception frequency is connected to the tuner section 1.
That is, the output of the FM detector 6 is passed through the low-pass filter 9 (
compensation control circuit) to an analog-to-digital converter (hereinafter referred to as an AD converter) 10. The output of this AD converter 10 is supplied to a frequency counter 11. The low-pass filter 9 takes out the DC output of the FM detector 6, and the AD converter 10 converts the DC output from analog to digital to create a preset signal, which will be described later. The signal is supplied to the frequency counter 11, which counts the local oscillation frequency after being preset to a predetermined value by the preset signal, and this counting result is displayed on the display 12.
are now being displayed digitally. The preset signal presets the frequency counter 11 to a predetermined value, and the preset value written to the frequency counter 11 becomes a value corresponding to the intermediate frequency of the intermediate frequency amplification stage 5 when the receiver is completely tuned. is set as,
In addition, this signal is controlled by the DC output of the FM detector 6 to correct the preset value when the tuning of the receiver is slightly shifted within the range in which a specific broadcast wave can be received. . A measurement circuit is comprised of the AD converter 10 and the frequency counter 11 having the above-described configuration. Now, assume that the local oscillation method in this receiver is a lower local oscillation method, and the intermediate frequency of the intermediate frequency amplification stage 5 is, for example, 10.70 MHz.

For example, assume that broadcast waves with a frequency of 80,900 MHz are to be received. FIG. 3 shows the DC output of the FM detector 6 (S-curve DC output), the preset value written to the frequency counter 11, and the local oscillation frequency of the local oscillator 3 for the tuning setting position of the receiver under the above conditions. , and the count value of the frequency counter 11 (display value of the display device 12). As shown in this figure, when the receiver is completely tuned, the DC output of the FM detector 6 is zero, 1-1, and the AD converter 10 sets the frequency counter 11 to a preset value of 10, which corresponds to the intermediate frequency. Write 70. At this time, the local oscillation frequency of local oscillator 3 is 69.30MHz
It is. As a result, the frequency counter 11 is preset to 10.70 and the local oscillation frequency is 69.30MH.
Count z8 and obtain a counting result of 80.00.

This count result of 80.00 is displayed on the display 12 as the reception frequency. Further, when the tuning of the receiver is shifted by −0.1 MHz from the tuning center of 80.00 MHz, for example, the DC output +V, [V] of the FM detector 6 is supplied to the AD converter 10. The AD converter 10 creates a preset signal to be supplied to the frequency counter 11 based on the signal obtained by AD converting the DC output +V1 [V], and writes a preset value of 10.80 to the frequency counter 11. At this time, the local oscillation frequency is 69320 MHz. As a result, the frequency counter 11 is . The local oscillation frequency was preset to 10.80 and the local oscillation frequency 69.20 was counted, resulting in a count result of 80.

00 is displayed on the display 12.

Similarly, in this embodiment, when the tuning of the receiver is shifted within the range of ±0.35 MHz from the tuning center of 80.00 MHz, the frequency counter is changed according to the DC output generated in the FM detector 6 at that time. 11 is controlled, the count result of the frequency counter 11 is always 80.00, and the display 12 always displays 80.00 MHz. Furthermore, when the tuning setting is further shifted from ±0.35 MHz, the DC output of the FM detector 6 becomes zero and the preset value of the frequency counter 11 becomes 10.70. The local oscillation frequency at this time is counted based on 10.70, and the tuning center frequency of the receiver is displayed on the display 12. FIG. 4 shows the relationship between the intermediate frequency + local oscillation frequency and the value displayed on the display 12 in this embodiment. As explained above, the received frequency display for this reception is such that when a specific received radio wave is received, the resulting frequency display displayed on the display 12 is controlled by the DC output of the FM detector 6. , as long as the radio waves are being received by the receiver, the frequency of the radio waves will be displayed on display 1.
2. 5 and 6 show specific circuit examples of the AD converter 10 used in the above embodiment.

That is, the AD converter 10 shown in FIG.
For example, the DC output of 0 to 60
A frequency counter 14a that converts this frequency signal into a Hz frequency signal and counts 10 KHz digits of the tuning deviation frequency.
and a frequency counter 14b that counts the same 100KHz digit, and these frequency counters 14a, 14bVC.
Specifically, a preset value of 10.40 to 11.00 in the range of 10.7 MHz±300 KHz is obtained, converted into a binary code, and supplied to the frequency counter 11.

Further, the AD converter 10 shown in FIG.
．． Convert this 1 to a decimal number in the range of 40 to 11.00.
The decimal number output is converted into a binary code by a decimal/binary conversion circuit 16 and then supplied to the frequency counter 11.

Figure 7 shows a second example in which this invention is applied to an FM stereo receiver.
This shows an embodiment, and the tuner section 1 has the same structure as that shown in FIG. In this embodiment, the reception frequency display circuit 8 is constructed as follows. That is, the output of the FM detector 6 is supplied to the voltage controlled oscillator 20 via the low pass filter 9, and the output of the voltage controlled oscillator 20 is supplied to the mixer 21. The voltage controlled oscillator 20 converts the DC output of the FM detector 6 obtained through the low-pass filter 9 into a frequency signal corresponding to this DC output. Further, the output of the local oscillator 3 is supplied to the mixer 21 via the frequency divider 22, the mixer 21 mixes the output of the frequency divider 22 and the output of the voltage controlled oscillator 20, and this mixed output is passed through the low-pass filter. 23 to a frequency counter 24, and the count result of the frequency counter 24 is digitally displayed on the display section 12. The oscillation frequency of the voltage controlled oscillator 20 is determined by the FM detector 6.
The change value of the oscillation frequency in this case is the output of the frequency divider 22 when the tuning of the receiver is shifted within the range in which a specific broadcast radio wave is being received. The frequency corresponds to the changing value. In addition, in the above-described configuration, a measurement circuit is composed of a voltage-controlled oscillator 20, a mixer 21, a frequency divider 22, a low-pass filter 23, and a frequency counter 24. Now, as in the first embodiment described above, the local oscillation method is the lower local oscillation method, the intermediate frequency is 10.70 MHz, and the oscillation frequency of the voltage controlled oscillator 20 is set with the DC output of the FM detector 6 being zero. What is the division ratio of 553KHz1 frequency divider 22? , the preset value of the frequency force counter 24 is set to 660. For example, if a broadcast radio wave with a frequency of 80.00 MHz is received, and the receiver is in a completely tuned state, the F
Since the DC output of the M detector 6 is zero, the voltage controlled oscillator 2
Since the oscillation frequency of 0 is 553KHz1 and the local oscillation frequency is 69.30MHz, the output frequency of the frequency divider 22 is 693KHz.

As a result, the mixing circuit 21 has the output frequency 69 of the frequency divider 22.
Oscillation frequency of voltage controlled oscillator 20 from 3KHz to 553K
Hz is subtracted, and the subtracted value of 140 KHz is supplied to the frequency counter 24 via the low-pass filter 23. The frequency counter 24 is given a preset value of 660 and counts a frequency of 140 KHz, obtaining a count result of 80.0. This count result of 80.0 is digitally displayed on the display 12 as a receiving frequency of 80.0 MHz. Also, tune the receiver within the range where 80.00MHz broadcast radio waves can be received, for example by -0.1 from the tuning center of 80.00MHz.
By shifting the MHz, the local oscillation frequency becomes 69.20MHz (
5, the output frequency of the frequency divider 22 becomes 692 KHz, and the DC output of the FM detector 6 is supplied to the voltage controlled oscillator 20, so that the oscillation frequency of the voltage controlled oscillator 20 becomes 552 KHz.
Hz.

As a result, the subtraction result in the mixer 21 becomes 140 KHz, and the display 12 displays 80.0 KHz as in the case of complete tuning.
MHz will be displayed. Similarly, when the tuning of the receiver is shifted to an arbitrary position within the range where broadcast waves with a frequency of 80.0 MHz can be received, the oscillation frequency of the voltage controlled oscillator 20 is controlled by the DC output of the FM detector. , the subtraction result of the mixer 21 is always 140, and the reception frequency of 80.0 MHz is always displayed on the display 12. Therefore, this embodiment also has the same effect as the first embodiment described above.
Effects can be obtained. Further, FIG. 8 shows a third embodiment in which the present invention is applied to an FM stereo receiver.

In this embodiment, in addition to the receiver having the tuner section 1 having the same configuration as that shown in FIG. A frequency counter 30 (measuring circuit) performs counting, and the counting result is displayed on a display 12. That is, in FIG. 8, the low bass filter 9,
The frequency counter 30 and the display 12 constitute a received frequency display circuit 8, and the output of the FM detector 6 is supplied to the time pace generation circuit 31 of the frequency counter 30 through the low pass filter 9, and the time of this time base generation circuit 31 is The base signal is controlled by the DC output of the FM detector 6, and the same time pace signal is supplied to the gate 32. On the other hand, the oscillation output of the local oscillator 3 is supplied to the counter 33 through the gate 32.
counts this, and the result of this count is digitally displayed on a display 12. In this configuration, the time base generation circuit 31 outputs the time base T to the gate 32 when the DC output of the FM detector 6 is zero, that is, when the receiver is completely tuned or completely detuned. give. And counter 33 is time pace TV
C} and count the tuning center frequency of the receiver.

Therefore, at this time, the display 12 displays the tuning center frequency of the receiver, and displays the frequency of the broadcast radio waves being received when the receiver is in a completely tuned state. Further, the time base generation circuit 31 generates the time base when the DC output is supplied from the FM detector 6, that is, when the receiver receives a specific broadcast radio wave and its tuning setting is slightly deviated from the perfect tuning point. Correct base T by ΔT. In this case ΔT
is the time required to make the count result of the counter 33 coincide with the count result at the time of perfect synchronization. Therefore, at this time, the display 12 displays the same numerical value as at the time of complete tuning, that is, the frequency of the broadcast wave being received. As described above, in this embodiment, the oscillation output of the local oscillator 3 is transmitted to the frequency counter 3.
0 with a predetermined time pace T, and the time base T is controlled by the DC output of the FM detector, and as a result, when the receiver receives a specific broadcast wave, the display 1
2 is made to match the broadcast radio waves being received.

FIG. 9 shows the time base generation circuit 31 in the above embodiment.
This is a specific circuit example.

That is, the oscillation output of the crystal oscillator 34 is divided into frequency dividers 35a,
36b . . . 35j8 to the terminal 36, and a time base signal (pulse signal) is obtained at this terminal 36. One signal period of this time base signal corresponds to the time pace T. Then, the same time base signal is added to the adder circuit 3.
7 and a differentiating circuit 38. Differential circuit 3
8 differentiates the falling edge of the time base signal and supplies it to the monostable multivibrator 39 as a trigger signal.
The output of the monostable multivibrator 39 is supplied to an adder circuit 37 and added to the time base signal. At this time, the output of the monostable multivibrator 39 is
The DC output of the M detector 6 is supplied, and the output of the monostable multivibrator 39 is pulse width modulated by the DC output. As a result, a time base signal controlled by the DC output of the FM detector 6 can be obtained at the output end of the adding circuit 37, and this signal can be supplied to the gate 32. As is clear from the above description, according to the present invention, in the reception frequency display device that displays the reception frequency based on the local oscillation frequency, the display frequency is controlled by the DC output of the FM detector. , the frequency of the received broadcast radio waves can always be displayed, not only when the receiver is in perfect synchronization, but also when the receiver is out of synchronization, as long as it is receiving a specific broadcast radio wave, unlike the conventional method. There is no need to finely set the preset value of the frequency counter.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the display frequency and the local oscillation frequency + intermediate frequency in a conventional reception frequency display device.
The figure shows the circuit configuration of a first embodiment in which the present invention is applied to an FM stereo receiver, and FIG. A diagram showing the relationship between the oscillation frequency and the count value of the frequency counter (display value on the display), and FIG. 4 is a diagram showing the relationship between the display value on the display and the intermediate frequency + local oscillation frequency in the same embodiment. , FIGS. 5 and 6 are diagrams showing specific circuit examples of the AD converter used in the same embodiment, and FIG. 7 is a diagram showing the circuit configuration of a second embodiment in which the present invention is applied to an FM stereo receiver. , FIG. 8 is a diagram showing the circuit configuration of the third embodiment, and FIG. 9 is a diagram showing a specific circuit example of the time base generation circuit used in the third embodiment. 1... tuner section, 2... high frequency amplification stage, 3...
Local oscillator, 4... Mixing stage, 5... Intermediate frequency amplification stage, 6... FM detector, 7... FM multiflex stereo demodulation circuit, 8... Reception frequency display circuit, 9.
...Compensation control circuit (low-pass filter), 10...Measuring circuit (AD converter), 11, 24, 30... Measuring circuit (frequency counter), 12...Display device, 20...
Measuring circuit (voltage controlled oscillator), 21... measuring circuit (mixer), 22... measuring circuit (frequency divider), 23... measuring circuit (low pass filter).

Claims (1)

[Claims] 1. In a reception frequency display device that displays the frequency of received radio waves based on the local oscillation frequency, there is an FM detector that outputs an S-curve DC output according to the deviation between the center frequency of the received radio waves and the tuning center, and this S-curve. a compensation control circuit that outputs a frequency compensation signal according to the DC output; and a compensation control circuit that measures the local oscillation frequency and, if there is a tuning shift and the frequency compensation signal is output, calculates a measured value based on the frequency compensation signal. It is equipped with a measurement circuit that compensates for a value corresponding to the center frequency of the receiving station, and a display that displays the measured value, and when tuned to a specific received radio wave, the center frequency of this received radio wave is displayed regardless of the tuning deviation. A received frequency display device characterized in that the received frequency display device is configured to display.