JPH03187612A - Tuner - Google Patents

Abstract

PURPOSE:To improve the operability by selecting an optimum automatic tuning stop level based on the result of comparison between an automatic tuning stop level candidate stored in advance and a reception signal level. CONSTITUTION:Plural sets of level information being at a high level are stored in a RAM 41 built in a microcomputer 4 and plural sets of level information being at a low level are stored in a RAM 42 respectively as automatic tuning stop level candidate. A comparator 9 compares an automatic tuning stop level candidate selected by a key 8 with a reception signal level from a detector 5 by one scanning and number of obtained outputs of the comparator 9 is counted. When the count output is within a predetermined range, the signal level read from the RAM 41 or 42 is judged to be optimum as the automatic tuning stop level and the signal level is set. Thus, the automatic turning stop level is adjusted exactly with excellent operability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tuner, and particularly to a tuner that sets an optimal auto-tuning stop level for auto-tuning.

(Conventional technique tlIi) By controlling the operation of the front end and PLL circuit, it automatically and continuously scans and changes the tuning frequency, and if a radio wave of a predetermined level or higher is received midway through, it scans once again. Various tuners are equipped with so-called auto-tuning, which stops the tuning.

In this auto-tuning, a configuration is conventionally used in which a fixed value is set as the level at which scanning is stopped (auto-tuning stop level). Furthermore, a configuration is also used in which the auto-tuning stop level is set to two levels (high level and low level) and one of them is arbitrarily switched.

FIG. 3 shows an example of the configuration of an auto-tuning related section of a conventional tuner.

A reception signal that has passed through an antenna terminal is converted into an intermediate frequency (IF) by selecting a desired broadcasting station frequency at a front end 1 consisting of a high frequency amplifier, a mixer, and a local oscillator.

This selection (tuning) of the desired broadcasting station frequency is performed using a PLL (phase-locked loop) using the received signal, which is the input signal of the front end 1, and the output of the detector 5, which is the output signal (output via the microcomputer 4). In other words, the phase difference between the input and output signals is obtained by the comparator constituting the PLL circuit 3, and based on this phase difference, the local oscillator (lock loop) in the front end 1 is Normally, CO is used to control the IF corresponding to the desired broadcasting station frequency.
You're getting twice the signal.

The narrowband IF filter 2A and the wideband IF filter 2B are
The filter characteristics are an IP filter with a narrow band and an IF filter with a wide band, each having a center frequency at the above intermediate frequency (usually 10.7 MHz). These filters pass sideband components distributed in widths of about 100 KHz above and below the center frequency without missing them, and block other components.

Narrowband IF filter 2A or wideband IF filter 2B
is selected as appropriate based on the input (instruction) information from the key 8. This selection is executed by cooperatively operating the switches SWI and SW2 using a control signal from the microcomputer 4.

The detection circuit 5 includes a narrowband IF filter 2A or a wideband I
The FM signal that has passed through the F filter 2B is detected and the audio signal is extracted. This detection is performed using a method such as PLL detection or pulse count detection, for example.

The detection circuit 5 also detects the center frequency f of the bandpass signal from the narrowband IF filter 2A or the wideband filter 2B.

The S signal of the detection level signal and the M signal indicating the deviation of the receiving frequency with respect to the broadcasting station frequency are detected and output.

The comparator 9 receives the S signal output from the detection circuit 5,
An H signal indicating a high level or a signal indicating a low level of a predetermined tuning stop level is compared with the S signal, and when the signal is equal to or higher than the auto-tuning stop level, auto-tuning is temporarily stopped. Switching between the high level H signal and the low level L signal was performed by switching the switch 10 by the user, and the reception state was judged by ear to switch and set a more appropriate level.

(Problems to be Solved by the Invention) As described above, in the conventional auto-tuning circuit of a tuner, the auto-tuning stop level is set to one fixed value or two fixed values (H level and L level).

However, if the auto-tuning stop level is set to a fixed value, it often cannot respond appropriately to reception conditions that vary depending on the region. For example, if the auto-tuning stop level is set too high in an area where many broadcast stations can be received, On the other hand, if the auto-tuning level is set too low, the frequency of auto-tuning stops will become too high, making it difficult to receive the desired broadcast station.

Further, the above-mentioned conventional auto-tuning stop level "H" and L'' switching setting is performed by a separately provided switch 10, but from the viewpoint of simplifying the circuit fiI command, this switch 10 is The software configuration is not desirable.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a tuner that can accurately adjust an auto-tuning stop level, has good operability, and has a simplified hardware configuration.

(Means for Solving the Problems) In order to solve the above-mentioned problems, a tuner according to the present invention includes an auto-tuning means that auto-tunes the received tuning frequency in a predetermined frequency range, and a plurality of predetermined level information. A memory means for storing as an auto-tuning stop level candidate, a DC voltage detection means for detecting a received signal and detecting a DC voltage corresponding to the received signal strength, and each level information read from the memory means and the DC voltage detection. Comparing means for comparing the DC voltage detected by the means and outputting an output when the DC voltage is larger than the level information; and when the comparing means has an output, temporarily stopping the auto-tuning and then performing the auto-tuning. and a control means for continuing the auto-tuning when there is no output from the comparing means, and counting the number of outputs from the comparing means when auto-tuning is performed in a predetermined frequency range for each level information, and setting means for setting the level information when the counting output is within a predetermined range as an auto-tuning stop level.

<Example) Next, the present invention will be explained with reference to the drawings.

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

The reception signal sent out through the antenna terminal is tuned by the front end 1 and the PLL circuit 3, and is sent to the narrowband IF selected by the changeover switches SW1 and SW2.
The signal is input to the detection circuit 5 through the filter 2A or the wideband IF filter 2B, and the detection circuit B5 detects the reception tuning signal and outputs the S signal and the M signal.

The audio signal (composite signal) obtained by the detection circuit 5 is separated and outputted by a multiplex decoder 6 into an L signal and an R signal as stereo signals.

In FIG. 1, blocks given the same reference numerals as those in FIG. 3 have the same functions as the blocks in FIG. 3, so a detailed explanation thereof will be omitted.

Now, the comparator 9 compares the S signal from the detection circuit 5 with the auto-tuning stop level, but in the present invention, generation and adjustment of the auto-tuning stop level differ from conventional tuners as follows.

That is, the microcomputer 4 includes a RAM (random access memory) 41 and a RAM 42. The RAM 41 stores a plurality of level information (for example, H1 to H) corresponding to a high level as auto-tuning stop level candidates, and the RAM 42 stores a plurality of level information (for example, Ll to L-3) corresponding to a low level as auto-tuning stop level candidates.
) are memorized as the same candidate.

High (H) auto-tuning stop level candidate or low (L) selected by the user using key 8
RAM according to auto tuning stop level candidate
1 or RAM2 is selected by the switch 43. Here, the switch 43 is built in as a function of the microcomputer 4, and is not separately added as hardware.

Further, a plurality of pieces of level information stored in the selected RAM are sequentially read out and supplied to the D/A converter 11.

The D/A converter 11 connects the RAM via the switch 43.
The automatic tuning stop level candidate, which is a digital signal supplied from 41 or RAM 42, is converted into an analog signal.

Comparator 9 compares the H or L auto-tuning stop level candidate selected with key 8 and the S signal level from detector 5, and stops auto-tuning when the S signal level is higher. After pausing at the tuning frequency of the time, further scanning of the tuning frequency is performed.
On the other hand, when the S signal level is smaller, the tuning frequency is further scanned and the same operation is performed.

In this way, the signal level read from either RAM 41 or RAM 42 is compared with the S signal level from the detector 5 (a predetermined tuning frequency range corresponding to -scan), and the resulting number of outputs from the comparator 9 is counted. do.

When this count output is within a predetermined range, it is determined that the signal level read from the RAM 41 or RAM 42 is optimal as the auto-tuning stop level, and that signal level is set.

On the other hand, when the counted output number of the comparator 9 is outside the predetermined range, the level candidate (for example, Hl
) is determined to be inappropriate, and other level candidates (for example, H
2) and perform the same process.

That is, when the number of counted outputs is large, the auto-tuning level is too low, and a higher level is newly set as the auto-tuning stop level, assuming that a broadcast station frequency signal with poor S/N conditions is also being received. In addition, when the number of counted outputs is small, it is determined that the set auto-tuning level is too high and the broadcast station frequency signal that can originally be received and listened to is not auto-tuned, and a lower level is set as the auto-tuning stop level. do.

In this way, the optimum auto-tuning stop level is selected and set from H1 to H5 or -L, depending on the high level or low level set by the user.

In the embodiment shown in FIG. 1, a plurality of levels are stored in the RAM as auto-tuning stop level candidates, and the levels read from the RAM and the detector 5 provided separately from the microcomputer 4 are A comparison with the S signal level is performed by a comparator, the number of comparison layer outputs is counted, and a level at which a counted output within a predetermined range is obtained is set as an auto-tuning stop level.

FIG. 2 shows an embodiment in which the comparator 9 in FIG. 1 is also incorporated as a function of the microcomputer 4.

That is, in the embodiment shown in FIG. 2, the S signal, which is an analog signal, from the detector 5 is converted into a digital signal by the A/D converter 12 and supplied to the microcomputer 4.

In the microcomputer 4, the level read from the RAM 41 or RAM 42 selected by the switch using the key 8 is compared with the digital signal from the A/D converter 12. This comparison process is the same as the comparison process of the comparator 9 in FIG. 1, and the subsequent selection of the I&appropriate auto-tuning stop level is also the same.

In the above embodiment, a plurality of pieces of level information are prepared and stored for each of the high level and the low level, but the information is stored from the beginning from the high level to the low level without clearly dividing it into high level and low level. It is also possible to prepare a plurality of pieces of level information and select one of them as the auto-tuning stop level.

(Effects of the Invention) As explained above, in the present invention, a plurality of predetermined level information are stored as auto-tuning stop level candidates in the memory (RAM) built into the microcomputer, and the level information is detected by the detector. The optimum auto-tuning stop level is selected based on the result of comparison with the S signal level of the received signal.Therefore, operability is significantly improved.

Furthermore, in the present invention, the hardware necessary for processing is basically a microcomputer, and compared to conventional tuners, a separate switch part is not required, so the circuit configuration is simplified.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the tuner according to the present invention, FIG. 2 is a block diagram showing another embodiment of the tuner according to the present invention, and FIG. 3 is a block diagram showing the tank bottom of a conventional tuner. It is a diagram. 1... Front end, 2A... Narrowband IF filter, 2B... Wideband IF filter, 3... PLL circuit,
4... Microcomputer, 5... Detection circuit, 6
...Multiplex decoder, 7...Display device, 8
...Key, 9...Comparator, 10...Switch, 1
1... D/A converter, 12... A/D converter, 41° 43... Switch, 44... Comparator. 42...RAM,

Claims (1)

[Scope of Claims] Auto-tuning means for auto-tuning a reception tuning frequency in a predetermined frequency range; memory means for storing a plurality of predetermined level information as auto-tuning stop level candidates; and a memory means for detecting a received signal. DC voltage detection means detects a DC voltage corresponding to the signal strength received by the DC voltage detection means, and compares each level information read from the memory means with the DC voltage detected by the DC voltage detection means, and determines whether the DC voltage is at the level. a comparison means that outputs an output when the comparison means has an output, and a control means that performs the auto-tuning after temporarily stopping the auto-tuning when the comparison means has an output, and continues the auto-tuning when there is no output from the comparison means. , Count the number of outputs from the comparing means when auto-tuning is performed in a predetermined frequency range for each of the level information, and when the counted output is within the predetermined range, the level information is used to stop the auto-tuning. A tuner comprising: a setting means for setting a level;