JPH06310991A - Tuning method and device - Google Patents

Abstract

PURPOSE:To attain automatic tuning without exerting an adverse influence on a receiving performance. CONSTITUTION:A received frequency is changed at every specified step by a frequency synthesizer 6, and the level of the detection signal of a radio circuit 21 is compared with threshold values Vth1 and Vth2 by a comparator 32. The received frequency of an actual broadcasting station is considered to be almost on the middle of a strong electric field, and a tuning point is obtained at the center of the number (n) of a point beyond the threshold value Vth2 corresponding to the strong electric field. Thus, it is not necessary to provide with an IF counter, and the generation of a noise can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tuning method and an apparatus therefor, and more particularly to a method and an apparatus for automatically tuning a frequency synthesizer type radio (for example, AM radio).

[0002]

2. Description of the Related Art Conventionally, when performing automatic tuning on a frequency synthesizer type AM radio, an intermediate frequency signal (IF signal) is added to a frequency counter, and a normal signal is received if the frequency of the received signal is near the intermediate frequency. I judge that I did.

[0003]

By the way, in the conventional automatic tuning method, since the counter is used for determining the tuning, the noise generated here may be mixed into other circuits and adversely affect the reception performance. There was a problem.

[0004] Therefore, an object of the present invention is to provide a tuning method and an apparatus therefor capable of performing automatic tuning without adversely affecting the reception performance.

[0005]

In order to achieve the above object, a tuning method according to the present invention is a tuning method in which a receiving frequency is changed at a predetermined step by a frequency synthesizer to tune to a desired frequency. The AGC signal or a signal similar thereto is compared with a plurality of thresholds having values corresponding to at least a strong electric field and a weak electric field, and the reception frequency is changed at predetermined steps by the frequency synthesizer, and the comparison is performed at that time. A at the reception frequency derived from the result
It is characterized in that the GC signal or a signal similar thereto has the tuning point at the midpoint of the frequency band larger than the threshold value.

Further, the tuning device according to the present invention is
In a tuning device for changing a receiving frequency at a predetermined step by a frequency synthesizer to tune to a desired frequency, at least two or more signals respectively corresponding to when the signal of the receiving frequency is a strong electric field and a weak electric field. A threshold value generation circuit having a threshold value of
A switching circuit for switching the plurality of threshold values, a comparison circuit for comparing the AGC signal at the reception frequency or a signal similar thereto with any one of the plurality of threshold values, and a comparison result of the comparison circuit. And a tuning point determining circuit having a tuning point at a midpoint of a frequency band in which an AGC signal or a signal similar to the AGC signal derived from the comparison result is larger than the threshold value.

[0007]

In the present invention, the reception frequency is changed by the frequency synthesizer at every predetermined step, and at this time, the AGC signal at the reception frequency or a signal similar thereto is compared with the first threshold value corresponding to the weak electric field, If the comparison result shows that the AGC signal or a signal similar thereto is large, the reception frequency is changed again at each predetermined step, and the received frequency is compared with the second threshold value corresponding to the strong electric field. When the signal or a signal similar thereto falls below the second threshold value corresponding to the strong electric field, then the frequency band in which the AGC signal or a signal similar thereto exceeds the second threshold value corresponding to the strong electric field. The midpoint of is the synchronization point.

In this case, the AGC signal or a signal similar thereto has a narrow frequency band in a weak electric field and a wide frequency band in a strong electric field. Therefore, when the broadcasting station is detected by the level judgment of this signal, it stops at a position other than the tuning point in the case of a strong electric field, but if the broadcasting station search is performed in accordance with the frequency interval of the radio station as described above, A tuning point is located at the midpoint of the frequency band in which the AGC signal or a signal similar thereto exceeds the second threshold value corresponding to the strong electric field (for example, the center of the number of points exceeding the second threshold value). There will be.
Therefore, since the IF counter is unnecessary, noise is less likely to occur, and automatic tuning can be performed while avoiding the influence on reception performance.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an AM radio of a frequency synthesizer system to which the present invention is applied. FIG. 1 is a diagram showing the entire circuit of an automatic tuning AM radio. In FIG. 1, reference numeral 1 denotes a key input unit, and the key input unit 1 is provided with an up key 2, a down key 3, and the like. The up key 2 and the down key 3 are for incrementing or decrementing the tuning data according to the local oscillation frequency currently being selected for tuning, and for instructing automatic tuning of the station immediately above or below.

The operation signal of each of the keys 2 and 3 is given to the control circuit 4, and an auto tuning process or the like is performed. The output of the control circuit 4 is given to the frequency synthesizer 6 as tuning data. The frequency synthesizer 6 generates a local oscillation signal having a frequency corresponding to the tuning data and outputs it to the mixing circuit 7.

A broadcasting signal received by an antenna 8 and amplified by a high frequency amplifier circuit 9 is given to the mixing circuit 7, and this broadcasting signal is mixed with a local oscillation signal from the frequency synthesizer 6 to obtain an intermediate frequency signal. Is taken out, amplified by the intermediate frequency amplifier circuit 10 and detected by the detector circuit 11, then amplified by the low frequency amplifier circuit 12 and emitted from the speaker 13.

The intermediate frequency signal amplified by the intermediate frequency amplifier circuit 10 is also given to the voltage comparison circuit 14 as an IFAGC voltage. The voltage comparison circuit 14 compares the threshold value (Vth1 or Vth2) corresponding to the threshold value switching signal output from the control circuit 4 with the IFAGC voltage, and outputs a [signal present] signal according to the comparison result. Alternatively, the process of stopping the output is performed. The control circuit 4 outputs tuning data for changing the reception frequency every 9 KHz depending on whether or not the [signal present] signal is output from the voltage comparison circuit 14.

The characteristic part of the present invention is shown in an easy-to-understand manner.
It becomes like FIG. In FIG. 2, 21 is an antenna 8,
High frequency amplifier circuit 9, mixing circuit 7, medium frequency amplifier circuit 10,
Detection circuit 11, low frequency amplification circuit 12 and speaker 13
It is a radio circuit consisting of. The control circuit 4 is composed of a microcomputer. The voltage comparison circuit 14 includes a comparator 32, an analog switch 33 and a threshold value V.
voltage sources 34 and 35 for supplying th1 and Vth2, respectively.
It is composed of

The analog switch (switching circuit) 33 has one of the threshold values Vth1 and Vth2 supplied from the voltage sources (threshold value generating circuits) 34 and 35 based on the threshold value switching signal output from the microcomputer 31. One of them is selected and supplied to the comparator 32. An IFAGC voltage signal as an intermediate frequency signal is given from the radio circuit 21 to the comparator (comparison circuit) 32,
The C voltage signal is compared with the threshold value (Vth1 or Vth2) selected by the analog switch 33, and the [signal present] signal is output to the control circuit (tuning point determination circuit) 4 according to the comparison result, Alternatively, the process of stopping the output is performed. The control circuit 4 performs a process of determining the tuning point based on the comparison result of the comparator 32.

Next, the operation will be described. FIG. 3 shows the control circuit 4
6 is a flow chart showing a program for automatic tuning control executed by. First, in step S10, the analog switch 33 is switched based on the threshold switching signal output from the control circuit 4, and the threshold Vth1 supplied from the voltage source 34 is set. This threshold value Vth1
As shown in FIG. 4, corresponds to a weak electric field, and the frequency band of the broadcasting station is narrowed in this weak electric field.

Next, in step S12, the reception frequency is set to 9
Raise only KHz. This is because in Japan, the frequency interval of AM radio stations is 9 KHz, and the station search by the synthesizer type receiver is performed at that interval. Next, in step S14, it is determined whether or not the [signal present] signal is output. In this case, the comparator 32 compares the IFAGC voltage signal as the intermediate frequency signal of the radio circuit 21 with the threshold value Vth1 and controls the [signal present] signal when the detection signal is larger than the threshold value Vth1 from the comparison result. Output to circuit 4. That is, this is the case when the level of the received signal is higher than the threshold value Vth1.

If the [signal present] signal is not output,
Returning to step S12, the same processing is repeated. Therefore, the process is performed until the level of the received signal becomes higher than the threshold value Vth1. Then, when the level of the received signal becomes larger than the threshold value Vth1 and the [signal present] signal is output, the process proceeds to the subsequent step S16, and the threshold value switching signal is output from the control circuit 4 to the analog switch 33 to output the voltage. The threshold value Vth2 supplied by the source 35 is set. This threshold value Vth2 corresponds to a strong electric field, as shown in FIG.
In this strong electric field, the frequency band of broadcasting stations is wide.

Threshold value Vth2 corresponding to a strong electric field
In order to count the number n set in step S
In 16, n = 1 is set. This is to count the number of searches when the station search is performed at intervals of 9 KHz when the level of the received signal is higher than the threshold value Vth2, so that the actual reception frequency of the broadcasting station is approximately in the center of the strong electric field. Therefore, in order to set the received frequency in the middle of the search frequency later, first, n = 1 is set in the first search processing.

Then, in step S18, the reception frequency is set to 9
The frequency is increased by KHz, and similarly, station search by a synthesizer type receiver is performed at intervals of 9 KHz. Then, step S
At 20, it is determined whether or not the [signal present] signal is output.
In this case, the comparator 32 compares the detection signal of the radio circuit 21 (that is, the IFAGC voltage signal as the intermediate frequency signal) with the threshold value Vth2, and when the detection signal is larger than the threshold value Vth2 from the comparison result, Signal present] The signal is output to the microcomputer 31. That is, when the level of the received signal is higher than the threshold value Vth2, the determination result of step S20 is YES. When the electric field is weak, the level of the received signal is the threshold value Vth2.
Since it does not become larger, it becomes NO and step S22.
Go to.

If the [signal present] signal is output, it is determined that the level of the received signal is higher than the threshold value Vth2,
At this time, n is incremented (n = n + 1), the process returns to step S18 and the same loop is repeated. And
When the [signal present] signal is not output in step S20, the level of the received signal becomes smaller than the threshold value Vth2, so station search is stopped at intervals of 9 KHz, and the process proceeds to step S22. In step S22, the frequency (reception frequency) is set to the center value (center frequency) of the number n of station searches at intervals of 9 KHz.

In this case, in the loop of step S18 and step S20, the level of the received signal is the threshold value Vt.
The station search when the frequency is larger than h2 is performed at an interval of 9 KHz, and if the number of times n of the search is counted, it is considered that the actual reception frequency of the broadcasting station is approximately in the center of the strong electric field. Setting the reception frequency in the middle will tune to the desired station.

That is, in Japan, the frequency interval of the AM radio station is 9 KHz, and the station search in the synthesizer type receiver is performed at that interval. If the detection signal of the radio circuit 21 is symmetric with respect to the station frequency, as a result of adding the detection signal to the comparator 32, the frequency point when the [signal present] signal is output becomes an odd number, and the station aimed at the center thereof. There is. Therefore, as shown in FIG. 4, the tuning point is at the center of the number n of points where the detection signal of the radio circuit 21 exceeds the second threshold value Vth2 corresponding to the strong electric field.

Since the actual detection signal is asymmetric at the skirt portion, at least two threshold values for the weak electric field and the strong electric field are provided to make the above determination. From the above, in the method of the present embodiment, since the IF counter is not required, noise is less generated, and automatic tuning can be performed while avoiding the influence on reception performance.

In the present embodiment, the plurality of threshold values have values corresponding to the strong electric field and the weak electric field, respectively, but the number is not limited to two, and for example, the strong electric field may be further divided into a plurality of, or You may make it have three threshold values in total. By doing so, even if the actual detection signal becomes asymmetric at the skirt portion, it can be set at the tuning point with high accuracy.

The present invention can be applied not only to AM radio but also to FM radio, for example.

[0026]

According to the present invention, the received frequency is changed by the frequency synthesizer at each prescribed step, and the midpoint of the frequency band in which the level of the received signal is at least larger than the threshold value corresponding to the strong electric field is used as the tuning point. Since it can be tuned to an accurate point in consideration of the electric field strength of the reception frequency, the IF counter is not required, noise is less generated, and it is possible to perform automatic tuning while avoiding the influence on reception performance. .

[Brief description of drawings]

FIG. 1 is a frequency synthesizer system A to which the present invention is applied.
It is a figure which shows one Example of M radio.

FIG. 2 is a block diagram illustrating a configuration of a control circuit of the same embodiment.

FIG. 3 is a flowchart showing a program for automatic tuning control according to the same embodiment.

FIG. 4 is a diagram for explaining station search in the receiver of the synthesizer system of the same embodiment.

[Explanation of symbols]

 1 1 is a key input unit 4 Control circuit (tuning point determination circuit) 6 Frequency synthesizer 7 Mixing circuit 9 High frequency amplification circuit 10 Intermediate frequency amplification circuit 11 Detection circuit 14 Voltage comparison circuit 21 Radio circuit 32 Comparator (comparison circuit) 33 Analog switch (Switching circuit) 34, 35 Voltage source (threshold generating circuit)

Claims (2)

[Claims] 1. A tuning method for changing a reception frequency at a predetermined step by a frequency synthesizer to tune to a desired frequency, wherein an AGC signal at the reception frequency or a signal similar thereto is respectively converted into at least a strong electric field and a weak electric field. Compared with a plurality of threshold values of corresponding values, the reception frequency is changed by the frequency synthesizer at every predetermined step, and the AGC signal at the reception frequency derived from the comparison result at that time or a signal similar thereto is A tuning method characterized in that a midpoint of a frequency band larger than a threshold is set as a tuning point. 2. A tuning device for changing a reception frequency at a predetermined step by a frequency synthesizer to tune to a desired frequency, wherein the reception frequency signal corresponds to a strong electric field and a weak electric field, respectively. A threshold value generating circuit having at least two threshold values, a switching circuit for switching the plurality of threshold values, an AGC signal at the reception frequency or a signal similar thereto, and the plurality of threshold values. A comparison circuit for comparing any one of the above and a comparison result of the comparison circuit and an AGC signal at a reception frequency derived from the comparison result or a signal similar thereto is a tuning point at a midpoint of a frequency band larger than the threshold value. And a tuning point determining circuit, and a tuning device.