JPS5934719A - Automatic frequency controller - Google Patents

Abstract

PURPOSE:To avoid the change of channel selection state up to the outside of a pull-in range even though the received radio wave does not exist any more, by stopping an AFC operation when the shift degree of frequency is larger than a prescribed frequency. CONSTITUTION:A microcomputer 5 decides and stores the shift degree of the present frequency to the center frequency. Then the frequency dividing ratio is corrected to raise or lower the tuning frequency by 50kHz in case the AFC voltage is higher than the reference level and at the same time the shift of frequency is within 800kHz. If the frequency shift exceeds 800kHz and is outside a pull-in range of the AFC operation, no correction is given. Then the dividing ratio of a frequency divider 8 is set at the value corresponding to the center frequency of the relevant channel.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to automatic frequency control 1 (AFC) in a synthesizer type channel selection device used in a television receiver, etc.
) regarding equipment.

Conventional configuration and its problems Recently, JtQ stations have been introduced that can digitally store channel selection information in memory for each channel! −? For example, automatic frequency control ζ! By detecting the intermediate frequency converted to an intermediate frequency and checking whether the frequency W is higher or lower than the undetermined intermediate frequency, the AFC converts the frequency 1 into a voltage level. An AFC device based on a synthesizer horn type that determines whether or not it is in the optimal tuning state and digitally increases or decreases the channel selection voltage or the frequency division ratio to achieve the optimal tuning is as follows: In principle, there is no control limit, and if the frequency shifts little by little, AFC will follow (fil+) forever.

Since it operates like this, it is necessary to insert and remove the antenna':9
If radio waves are temporarily not input, use the 1-pin channel selection type: Increases or decreases depending on the AFC voltage. Also, A
F G 'f (Q pressure is unstable when there is no signal, 1-
Katasu 1: It costs. Therefore, if the AFC voltage becomes positive with no signal, the tuning voltage begins to rise to negative 2).

However, since there is no signal no matter how far the AFC voltage continues to rise, the channel selection voltage continues to rise until it reaches its maximum voltage. If this happens, even if the next signal is input, the AFC pull-in limit (usually about 1MHz) will be reached.
Since it has exceeded the limit, it can no longer be withdrawn.

In order to avoid this, conventionally the synchronizing signal is also detected and the AFC operation is stopped at the point where the synchronizing signal disappears. However, as will be explained next, this is not suitable for a television receiver having an external video input terminal. Figure 1 shows the external video input terminal AUX-I.
-C shows the AFC voltage input section and synchronization signal input section of the channel selection device of the television receiver with N and -C. As you can see from the figure, the AFC voltage is always from the received radio waves, but the synchronization signal is obtained separately for each video signal, so
When the switch is switched to external video input, the synchronization signal of the external video signal is added. In this state, if the external video signal is always present and the incoming radio waves are temporarily lost, the synchronization signal will always be present, but the AFC voltage will remain on the received signal. 'Ushitama If the received radio wave disappears and the signal f' (but j) goes up, the channel selection voltage rL will start to rise by +1.In this case, the channel selection voltage will go up +J71 as described in +ii1, and the output signal will rise. 3゜Object of the Invention The present invention eliminates such conventional inconveniences by eliminating some of the inconveniences, such as receiving 1 and radio waves, even when the electric power is manually operated. Automatic frequency control device installed at the station 1? The second objective is to provide the following.

Structure of the Invention In the present invention, automatic frequency control I'! In the device, AFC
Detects frequency deviation 111 due to operation (~, the deviation 1
By controlling the AFC operation to stop when 11 becomes close to a predetermined frequency, the frequency does not change beyond a predetermined range. I
' ? 1. Description of Embodiment Hereinafter, an embodiment in which the present invention is implemented in a frequency synthesizer type tuning device controlled using a microcomputer will be explained in detail in 1 with reference to the drawings. do. Fig. 2 shows a block diagram of its configuration, and Figs. 3 and 4 show its operation flowchart 1'. In Fig. 2, 1 is a tuner, 2 is an intermediate frequency increaser I+]
Ig3 is the video detection order, 4 is according to the amount of shift in the intermediate frequency /
The AFG voltage controller that generates the AFG voltage, 5 is a microcomputer for control, and 6 is a recorder of information for channel selection.
1 device, 7 is the channel selection voltage il/-Namekawa's low-pass filter, 8 is the iiJ variation station, 9 is the reference signal optical vibration, 10
11-1l, ζ し′ [1 ratio 1 occlusion, 11 and 12 are A
This is a comparator for detecting the FC voltage range. tuner 1
The output signals include an intermediate frequency signal and a local oscillation signal, 1)
The 11 signal is sent to the video detection circuit 3 via the intermediate 1 #1 wave increment [11 and 2, and becomes a video signal output.

A part of the intermediate frequency signal detects the shift in the intermediate frequency.
FC voltage light is applied to light at sg 4 to create an AFC voltage according to its shift foot position) 1, the A F C'Ill
fl- is reduced by the comparators 11 and 12 to the 1L pressure 8.5v and 4.5v, which are the standards for the two lower limits, and is 11.5v lower than the AFC operation upper limit of 8.5. ``The voltage is within the AFC operating range, 5 V and 4.6 V (7
) between 11: or itl, AFC operation lower limit 4
．． If the voltage is lower than 6V, it is converted into digital information such as ', 1++, and then added to the microphone II's internal circuit.

c/)k F C'1(,:IIV+;s,s V
, 1: Sl:, 1 means the highest tuning frequency; The frequency is lower than that for surface I, and the frequency is lower than 4.5V. In either case, the AFC operation is safe, and 8.
The fact that the voltage is between 5 and 4.5V means that t, j, and the maximum J-tuning frequency θ) are close to each other, so that AFC operation is not necessary.

The local oscillation frequency of 1-1 is added to the variable frequency divider 8 and divided by the frequency division ratio instructed by the microcomputer 6. Its output and J, 9′.

Comparison of digit 411 with oscillation signal 'A'r' = 1
The ratio is 1119 at 0, and the output is applied to the chicona 1 through the filter 7. In response to this, the frequency division ratio stored in advance in the storage device i't 6 for each channel to be selected is read out by the microphone 1 and the computer 6. By manually inputting the frequency division ratio according to the selected channel to the IIF variation frequency division section 8,
You can select the desired channel to receive it. By changing the frequency division ratio in small increments, the tuning frequency can be changed in small increments and AFC operation can be performed.

The frequency division ratio and AFC on/off information, which will be described later, are stored in advance in the storage device 6, and are read or written as necessary.

Next, the AFC operation will be explained with reference to flowcharts shown in FIGS. 3 and 4. In this case, the deciphering of human power from remote control and the associated work
Flowchart 1- is shown in which the microcomputer 10 is made to perform the AFC operation and the AFC operation.

In FIG. 3, after Star I, a check is first made to see if there is a key force (A), and if there is a key force, the key force is deciphered (B). Without key human resources,
Next, perform the remote control (No. 8 with or without human power) (G), and use that human power to draw 1 - 4 (D). Key human power or remote control 7 i I+ − /, and when the manual content is corrupted by IW, C,1, the predetermined (l ′ii (′)-ri) is performed according to the deciphered content (
E). If those JLs require human power, this device features A.
The FC operation is not active (F), and the main routine of the original 11t-gray run is working at 8 msec/1), and the key human power is remote control. 'i
), and when there is no human power, the AFC operation is executed once every amsec.

Figure 4 shows the AFC operation routine in Figure 3. 'iYJl
Flowchart 1.71 of this device! This is an assistant work with a characteristic. In the figure, A F C!
riJ+ (Determine whether or not to perform 'l (a).
Roll 61 to judge. AFC on/
1 for off marker, always AFC when switching channels
Set to on. Here, it is determined whether the AFC operation should be switched off or not, and if the AFC on/off marker is off, the process returns to the main routine. If AFC is on, determine where the AFC voltage is with respect to voltages 8.5v and 4.6v by detecting the outputs of comparators 11 and 12 (b), CO ).

Next, the receiving frequency is 71 and 8 from the center frequency (the middle frequency according to the TV channel plan).
It is determined whether the frequency is within 00 KHz (within the pull-in range of AFC operation) (li) (e). This 80
Is it within 0 KHz?It, Mike: 1.Computer 6 determines the tuning frequency by determining the division ratio, so how much does it deviate from the current middle/b frequency in the microcombi and coater 5? Then, if the AFC voltage is a6VL di1- and the frequency deviation is within 800 KHz,
Same, 7. '． 1 frequency by 50 KHz.”
: Correct the frequency division ratio (f). In addition, AFC voltage voltage 8.6V or more -1: fmona <, 4.6V ~ 8.5
When it is not within the V range (that is, when it is 4.5V or less)
, and if the frequency shift is within 800 KHz, the frequency division is corrected to lower the tuning frequency by 60 KHz (g). This is a 50KHz tuning frequency modification.'', A F C
'ILI', I+ is 4.5 to 8.5 V (7)
PC within range. 1. Ilt: A F C move a'1. However, frequency 11 is 800KHz LJ
If it is 1, it will exceed the pull range of AFG operation, so 1. 50 KHz each (1') as shown below.
≦11 & 1, (1Δ), and set the tuning frequency to 1'.1 wave I in the -1-yanonel (h
). Jl, one line is 1 &: t, the frequency division ratio of frequency division field 8 is 1 to the frequency division ratio corresponding to 411 to the center frequency of that nayano fault.
be destroyed. Then, in the main routine at the determination step a from the next routine, if
Let's make it so.

By doing this, when the tuned frequency deviates from the middle, 1] frequency by more than 80 KHz, the iLk
By setting the frequency to medium 1 without allowing the FC operation to continue any further, the deviation from the AFC pool illumination range can be reduced by 1.
<) month can be done.

Note that the above explanation has been given for the case of a frequency/sensor→noisaka type channel selection device, but the frequency/sensor→noisaka type channel selection device is used. //It can be implemented similarly in the case of a Sezaiza type channel selection device.゛Effects of the Invention As described above, according to the present invention, in the AFC device in the synthesizer type channel selection device, there is no synchronous signal. ! It is possible to prevent the deviation of the tuning frequency from deviating from the pull-in range due to the Q relationship. J

[Brief explanation of drawings]

FIG. 1 is a Zoroku diagram of an amplifier-based tuning device, FIG. 2 is a block diagram of an automatic frequency control device according to an embodiment of the present invention, and FIGS. 3 and 4 are flowcharts showing its operation. It is 1. 1...Chis, 2...Intermediate frequency increase [1] product, 4...AFC electric FF, generator, 5...
Microcomputer, 6..., i-self storage device, 7
...Low pass filter, 8...Variable frequency divider, 9...Reference signal oscillator, 10... (e
71111tIQRL i 1.12... Comparator. Name of Daikeito 1] Physician Toshi Nakao (1 person) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] The synthesizer type tuning device is provided with an automatic frequency control means that performs automatic frequency control by changing the division ratio of the frequency division filter or the tuning voltage using a separate signal according to the deviation of the intermediate frequency, 1) a detecting means for detecting the amount of deviation in frequency after the change; and 1) a detection means for detecting the amount of frequency deviation after the change; An automatic frequency control device characterized in that it includes a stopping means for stopping the frequency.