JPH0547127B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a receiver that prevents malfunctions during automatic channel selection and enables shortening of in-band scanning time.

[Prior Art] Conventional electronically tuned radio receivers use either a DC voltage depending on the electric field strength of the received station or a count value of an intermediate frequency alone as a stop signal during automatic tuning. It was hot.

FIGS. 3 and 4 are block diagrams showing examples of conventional receivers, respectively. Among these, first, in FIG. 3, the antenna 1 is connected to the tuner 2,
The detected signal is guided to a speaker 8 via a low frequency amplification circuit 7.

Further, the output of the tuner 2, such as a DC voltage (for example, signal meter output) corresponding to the electric field strength of the received station, is guided to the reception level determination circuit 3 and used as a stop signal.

When the automatic tuning button 51 of the tuning device 5 is pressed to enter the automatic tuning mode, the control circuit 4 checks the output of the reception level determination circuit 3 for each channel and cancels or temporarily stops the automatic tuning mode. It is determined whether this is the case, and data corresponding to the determination is outputted to the tuning voltage generation circuit 6.

Fig. 4 shows that instead of using a DC voltage according to the electric field strength of the received station as a stop signal, the intermediate frequency of the tuner 2 is counted by a frequency counter 41, and this value is used to determine whether to cancel automatic tuning mode or temporarily stop it. It is used for.

[Problem that the invention seeks to solve]

In the receiver shown in Figure 3, noise rises due to gain increase at constant temperature, harmonics of various oscillation circuits in the same receiver, or in the MW band.
The reception level judgment circuit 3 malfunctions due to the influence of the AGC time constant, modulation frequency, modulation degree, etc., and the automatic tuning mode is canceled or temporarily stopped even though no broadcast is actually being received.This is called a misstop. There were many problems.

In addition, the DC voltage that is guided from the tuner 2 to the reception level judgment circuit 3 according to the received electric field strength rises relatively slowly, and remains constant until the control circuit 4 detects the judgment output of the reception level judgment circuit 3 to prevent malfunction. Time wait time (MAIT)
It was necessary to take TIME).

As described above, since this wait time is required for each channel during automatic channel selection, there is a problem in that it takes a considerable amount of time to scan all bands.

On the other hand, as shown in Fig. 4, in a system that counts the intermediate frequency and uses it as a stop signal, if the difference in the broadcasting frequencies of two broadcasting stations is within the specified count frequency range, the beats of those two broadcasting frequencies cause There was a problem with a misstop.

The present invention has been made in order to solve these problems, and aims to provide a receiver that can reduce the number of misstops caused by malfunctions in the automatic channel selection mode and shorten the total band scanning time.

[Means for solving problems]

The receiver according to the present invention is provided with means for determining that both the DC voltage and the intermediate frequency count value corresponding to the received electric field strength are valid stations.

[Effect]

In this invention, the reception level is determined by the DC voltage according to the electric field strength from the tuner, and the intermediate frequency is counted, and the automatic tuning mode is canceled only when it is determined that both the count value and the DC voltage are valid. , or use it to stop once.

〔Example〕

Embodiments of the receiver of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment. In this Figure 1,
The same parts as in FIGS. 3 and 4 are given the same reference numerals, and explanations of their configurations are omitted.
I will mainly describe the parts that are different from the diagram.

In FIG. 1, the reception level determination circuit 3 shown in FIG. 3 is added to the configuration of FIG. The output of this reception level determination circuit 3 is sent to a control circuit 4.

Further, the intermediate frequency from the tuner 2 is counted by a frequency counter 41 in the control circuit 4, and when both this count value and the output of the reception level determination circuit 3 are determined to be a valid station by the roll circuit 4, The automatic channel selection mode can only be canceled or temporarily stopped.

Next, the operation of the receiver of the present invention will be explained with reference to the flowchart of the automatic channel selection mode shown in FIG.

When the automatic tuning button 51 of the music selection device 5 is selected to enter the automatic tuning mode, the mute output is first output (step S1), and the setting and display of the next channel frequency division ratio from the current display frequency are updated ( Step S2).

Further, inside the tuner 2, the local oscillation frequency is also updated by the tuning voltage generation circuit 6 based on the updated data from the control circuit 4.

At this time, the broadcast radio wave equal to the updated display frequency coming from the antenna 1 is converted into an intermediate frequency between the local oscillation frequency and the local oscillation frequency by the mixer circuit, and passes through the intermediate frequency amplification stage to the control circuit 4.
is input to the frequency counter 41 of. At this time,
PLL (Phase Locked Lap) is locked (step S3).

By setting the intermediate frequency count specification range to be much smaller than the channel space (for example, within ±40 KHz if the channel space is within 200 KHz), it can be determined whether broadcast waves equal to the display frequency are coming from antenna 1.

If the station is determined to be an invalid station by counting the intermediate frequency in step S4, the process returns to step S2 and proceeds to the next channel.Only if the station is determined to be a valid station, after a certain wait time in step S5. (Step S5) Check the output of the reception level determination circuit 3 (Step S6).

In this way, only when both the intermediate frequency count value and the output of the reception level determination circuit 3 can be considered to be valid stations, the control circuit 4 starts the automatic tuning mode after muting in step S7, and then temporarily stops it in step S8 or stops it in step S9. to cancel automatic tuning mode. Then, after stopping at step S8, only the weight is applied at step S9, that is,
ONLY WAIT and step
Return to S1.

As mentioned above, by canceling or temporarily stopping the automatic channel selection mode, even if one of the judgments is incorrect, it will not lead to an immediate malfunction (for example, a misstop).

If the automatic channel selection mode is not to be temporarily stopped, the automatic channel selection mode is canceled in step S9 and other mode processing is performed.

20 msec is sufficient for counting the intermediate frequency to cancel or temporarily stop the automatic channel selection mode (to prevent malfunctions, it usually counts about 3 times, and only when the frequency is within the specified frequency range more than 2 times) It is considered a valid station, but the total
(20 msec is sufficient), whereas the received level is checked after a wait time of about 40 to 60 msec to prevent malfunctions.

Therefore, even if the two signals are used as stop signals, the total band scanning time in areas where there are few broadcast waves entering antenna 1, or the time required for scanning effective stations during automatic tuning, will be ineffective. Since stations can be identified only by counting intermediate frequencies, the third
It can be shorter than the conventional receiver shown in the figure.

Furthermore, the switching of the stop level under a strong electric field and under a weak electric field can be achieved by making the judgment in the received level judgment circuit 3 using a DC voltage input according to the received electric field strength, as before, without requiring any special circuit. Can be configured.

Note that if the PLL is not locked in step S3, the process returns to step S3 and repeats the same loop until a lock is detected.

〔Effect of the invention〕

As explained above, this invention utilizes the DC voltage and intermediate frequency count values according to the received electric field strength, and cancels or temporarily stops the automatic tuning mode only when both are determined to be valid stations. It is possible to prevent misstops due to malfunctions during automatic channel selection, and it is possible to check the reception level judgment output, which requires a certain wait time, only when it is judged as a valid station, eliminating wasted time during scanning and reducing the time required for scanning. can be shortened.

In addition, stop level judgment under strong electric fields and weak electric fields can be determined using a conventional reception level judgment circuit that outputs a DC voltage according to the strength of the received electric field, and can be easily configured without using any special circuit. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the receiver of the present invention, FIG. 2 is a flowchart showing the flow of operation of the same receiver during automatic channel selection, and FIGS. 3 and 4 are respectively 1 is a block diagram showing the configuration of a conventional receiver. DESCRIPTION OF SYMBOLS 1...Antenna, 2...Tuner, 3...Reception level judgment circuit, 4...Control circuit, 41
... Frequency counter, 5 ... Tuning device, 51 ...
Automatic tuning button, 6...Tuning voltage generation circuit,
7...Low frequency amplifier circuit, 8...Speaker. In addition,
The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A tuner that detects a received signal, generates an intermediate frequency signal, and outputs a DC voltage according to the electric field strength of the receiving station, and a low-frequency amplification means that amplifies the signal detected by the tuner and drives a speaker. , a tuning means for setting the automatic tuning mode when the automatic tuning button is operated, a counting means for counting the intermediate frequency, and a count value of the counting means when in the automatic tuning mode is within a specified range. The first mode checks the reception level from the DC voltage according to the electric field strength of the receiving station, and if it is not within the specified range, moves to the next channel and continues the automatic tuning mode.
a determination means for temporarily stopping or canceling the automatic tuning mode if the receiving level of the receiving station is above a predetermined level, and moving to the next channel and continuing the automatic tuning mode if the reception level of the receiving station is lower than the predetermined level. 2, and tuning voltage generating means for applying a tuning voltage to the tuner based on the outputs of the first and second determining means.