JP2540812B2 - Tuning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial Field B Outline of the Invention C Prior Art (Figs. 6 and 7) D Problems to be Solved by the Invention (Fig. 6) E Means for Solving Problems (Fig. 1 And FIG. 5) F action (FIGS. 1 and 5) G Embodiment (FIGS. 1 to 5) H Effect of the invention A Industrial field of application The present invention relates to a channel selection device, for example, satellite broadcasting reception. It can be applied to machines.

B. Summary of the Invention In the present invention, in the channel selection device, the center frequency in the automatic frequency adjustment operation can be arbitrarily set for each broadcasting channel, so that the channel selection center frequency is shifted in order to avoid an adverse effect due to an interference wave, for example. It is also designed to be able to perform automatic frequency adjustment operation for broadcast channels.

C Related Art For example, in satellite broadcasting, broadcast radio waves are captured by a receiving antenna installed outdoors, and then in a down converter, for example, after frequency conversion from 4 [GHz] band to 1 [GHz] band, It is designed to be given to a satellite broadcast receiver as an indoor unit via a cable, and even in the satellite broadcast receiver in the first stage, for example, 1 [GHz]
The frequency is converted from the band to the 400 [MHz] band.

The fluctuation (drift) of the local oscillation frequency in each frequency conversion stage affects the reception image quality and voice, so it is desirable to correct the fluctuation. Especially, in satellite broadcasting, a down converter is installed outdoors. However, it is desirable to correct the fluctuations because the fluctuations tend to become large. Therefore, in the conventional satellite broadcasting receiver, an automatic frequency adjustment (AFT) circuit for correcting fluctuations in the local oscillation frequency as shown in FIG. Is provided.

In FIG. 6, for example, 1 coming from an outdoor unit
The first intermediate frequency signal IF1 in the [GHz] band is the mix circuit 1
Is mixed with the local oscillation signal LOS given from the local oscillation circuit 2 in the mix circuit 1,
The signal is converted into the second intermediate frequency signal IF2 of [MHz], is applied to the detection circuit 3, is FM-detected, and the baseband signal BB is output.

From the detection circuit 3, the upper band obtained by converting the energy of the second intermediate frequency signal IF2 into the DC voltage of the energy component having the frequency component larger than the frequency f _LOS of the local oscillation signal LOS as shown in FIG. Component detection signal TU,
A lower band component detection signal TL obtained by converting the energy component of the frequency component smaller than the frequency f _LOS into a DC voltage is output.

A difference (TL-TU) is obtained in the subtracter 4 from these upper and lower band component detection signals TU and TL.
After SUB is raised by a predetermined level (for example, 2.5 [V]) REF by the level setter 6 in the offset applying circuit 5, the comparison input signal CI is sent to the window comparator circuit 7.
Given as N. The window comparator circuit 7 is
An upper threshold signal THH that is larger than a predetermined level REF by a dead band level (for example, 1 [V]), and a predetermined level REF
Lower threshold signal THL that is smaller by the dead band level
When the comparison input signal CIN is larger than the upper threshold signal THH, the down signal DW is given to the controller 8, and the comparison input signal CIN is changed to the lower threshold signal T.
When it is smaller than HL, the up signal UP is given to the controller 8.

The controller 8 has, for example, a microcomputer configuration, and when the down signal DW is applied, the controller 8 lowers the local oscillation frequency f _LOS by a unit frequency (for example, 100 [kHz]) with respect to the local oscillation circuit 2. On the contrary, when the up signal UP is given, the local oscillation circuit 2 is controlled to increase the local oscillation frequency f _LOS by a unit.

Thus, when the local oscillation frequency f _LOS is deviated and there is a difference between the upper and lower band component detection signals TU and TL, the local oscillation frequency f _LOS is made equal so that both detection signals TU and TL are equal.
Is varied so that the optimum chewing point can be obtained.

D Problem to be Solved by the Invention By the way, in the case of satellite broadcasting using the so-called C-band 4 [GHz] band, which is widely used in the North American continent, it is separated by 10 [MHz] depending on the installation location. It is known that interference waves from terrestrial microwave circuits are generated everywhere.

In order to suppress the image quality deterioration due to the ground interference wave, one method is to shift the local oscillation frequency f _LOS so that the difference becomes larger than the frequency of the ground interference wave that is generating. When applying this method, AFT
If you select a mode, it will eventually return to the normal center frequency. Therefore, in order to suppress the image quality deterioration due to the interfering wave by such a method, the operator releases the AFT mode selection switch 9 (Fig. 6) to cancel the AFT mode and manually shifts the local oscillation frequency. .

However, if the local oscillation frequency is shifted in this way to prevent image deterioration due to ground interference,
Since the T mode is canceled, it is affected by the drift as it is, and when looking at such a broadcast channel, it means that the AFT function of the receiver is not effectively used.

The present invention has been made in consideration of the above points, and it is an object of the present invention to provide a channel selection device capable of performing AFT operation on all broadcasting channels including a broadcasting channel whose local oscillation frequency is shifted from the regular frequency. To do.

E Means for Solving the Problems In order to solve such problems, in the present invention, the high frequency signal IF1 received by the antenna and the local oscillation signal LOS provided from the local oscillation circuit 2 are input to the mixing circuit 1. In the channel selection device in which the output of the mixing circuit 1 is given to the detection circuit 3 to output the baseband signal BB, the local oscillation of the local oscillation circuit 2 is performed for each channel in response to the user's operation. The local oscillation frequency adjusting means 12 for adjusting the frequency f _LOS , the storage means 14 for storing the adjustment value COL adjusted by the local oscillation frequency adjusting means 12 for each channel, and the deviation of the local oscillation frequency f _LOS are detected. The detecting means 3, 4, 5 and 10 and the selected channel are channels adjusted by the local oscillation frequency adjusting means 12, and the adjustment value COL for the selected channel is stored in the memory. When stored in 14, the detection means 3,
Detection value DAT detected by 4, 5, and 10 and storage means 14
If the selected channel is not the channel adjusted by the local oscillation frequency adjusting means 12, it is detected by the detecting means 3, 4, 5, 10 in comparison with the adjustment value COL stored in. The detection value DAT and the predetermined value DO are compared with each other, and the control means 11 for controlling the local oscillation frequency f _LOS of the local oscillation circuit 2 based on the comparison result is provided.

F function The center frequency information in the AFT operation can be arbitrarily set for each broadcasting channel, the set center frequency information is stored in the memory 14, and the AFT is set so that the center frequency information is read during the AFT operation and becomes the center frequency. I tried to move.

As a result, the AFT operation can be performed even for the broadcast channel whose tuning center frequency is arbitrarily shifted by the operator.

G. Embodiment Hereinafter, an embodiment in which the present invention is applied to a satellite broadcast receiver will be described in detail with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 6 are designated by the same reference numerals, the comparison input signal CIN output from the offset applying circuit 5 is converted into digital data DAT through the analog / digital conversion circuit 10. After that, it is given to the controller 11 having, for example, a microcomputer configuration.

The controller 11 responds to an input signal from the keyboard input device 12 and, if necessary, a charactor generator.
The output signal is sent to 13 and predetermined items are displayed on the monitor screen (not shown), and the preset processing of the far inch uning point shown in FIG. 2 is executed. (Obtained as the output level of the offset applying circuit 5 and referred to as a control point level hereinafter), and stored in the broadcast channel / control point level correspondence table TAB (FIG. 3) of the memory 14.

That is, the controller 11 starts the preset processing program of the fine inch uning point in step SP1, proceeds to the next step SP2, waits for a key input, and when there is a key input, determines the content.

As a result of the determination, the controller 11 determines that the "FINE" key 12a
If it is determined that is pressed, the process proceeds to step SP3 to determine whether the control point level preset mode has been selected.If a negative result is obtained because it has not been selected until now, the process proceeds to step SP4. After setting the selected flag FLG1 of the set motor, at step SP5, the message M1 "FINE" indicating that the preset mode is selected is displayed on the pipe surface SUR (Fig. 4), and at the same time,
Initial value of deviation Δf (0.0 [MHz]) between the normal center frequency for the broadcast channel and the center frequency for the broadcast channel shifted by pressing the “UP” key 12b or “DOWN” key 12c by the operator. M2 is displayed (FIG. 4 (A)), and then the main routine is returned to at step SP6.

On the other hand, in step SP3, if a positive result is obtained because the preset mode has been selected so far, the controller 11 proceeds to step SP7 and lowers the selected flag FLG1 of the preset mode, and then proceeds to step SP3. SP8
Then, as shown in FIG. 4 (C), the display on the tube surface SUR is erased and the operator confirms the purpose of ending the preset mode processing.

After that, the controller 11 proceeds to step SP9 and while the selected flag is rising, presses the "UP" key 12b or the "DOW" key.
It is determined whether or not the "N" key 12c has been pressed at least once, and if a negative result is obtained, it is determined that the table TAB does not need to be updated, and the process immediately proceeds to step SP6 and returns to the main routine. On the other hand, if a positive result is obtained in step SP9, the operation proceeds to step SP10, in which the operator set channel flag FLG2 (FIG. 3) indicating that the broadcast channel is a broadcast channel whose control point level is arbitrarily set by the operator. ) Is started, and the control point level COL (FIG. 3), which is given through the analog / digital conversion circuit 10 at that time and stored in the register, is stored in the table TAB of the memory 14 together with the flag FLG2 in step SP11. Then, the process returns to the main routine at step SP6.

In addition, the controller 11 determines that “U
If it is determined that the `` P '' key 12b has been pressed, it proceeds to step SP12 and determines whether or not the selection flag FLG1 is raised,
As a result, if a negative result is obtained, the operation proceeds to step SP6 and returns to the main routine, that is, returns to the main routine without any processing even if the "UP" key 12b is pressed. On the other hand, if a positive result is obtained, the operation proceeds to step SP13 to increase the deviation of the local oscillation frequency f _{LOS from} the normal frequency in the broadcast channel by 100 (k Hz), and then to step SP14. Then, the control point level COL at that frequency is fetched through the analog / digital conversion circuit 10 and temporarily stored in a built-in register. Then, the processing proceeds to step SP6 and returns to the main routine.

When the "DOWN" key 12c is pressed, almost the same processing is executed. That is, it proceeds to step SP15 to determine whether or not the selection flag FLG1 has risen, and as a result, if a negative result is obtained, it proceeds to step SP6 to return to the main routine, and if a positive result is obtained, Step SP16
Then, the deviation of the local oscillation frequency f _{LOS from} the normal frequency in the broadcasting channel is reduced by 100 [k Hz], and then the process proceeds to step SP14 to set the control point level at that frequency to the analog / digital conversion circuit 10. It is fetched via the, and once stored in the built-in register, the process proceeds to step SP6 and returns to the main routine.

As described above, by executing the preset mode processing program and setting the center frequency of a predetermined broadcast channel to the frequency at which the image quality is the best, the operator first selects and operates the broadcast channel. Then, press the "FINE" key 12a to confirm that the message M1 "FINE" is displayed on the surface SUR (Fig. 4 (A)), and then press the "UP" key 12b or "DOWN". "
Repeatedly press the key 12c until the image quality is best (Fig. 4 (B)), and then when it is judged to be the best, press the "FINE" key 12a again and the display disappears (Fig. 4 (C)). )) Is confirmed and the operation is completed.

At this time, in response to the first operation of the "FINE" key 12a, the controller 11 causes the steps SP1-SP2-SP3-SP4-SP5-SP6.
Is executed and the mode is selected.
E ”message M1 is displayed, and then the controller 11 responds to the operation of the“ UP ”key 12b with step SP1-SP2-SP12.
-SP13-SP14-SP6 processing is executed to increase the message content M2 representing the deviation Δf from the normal frequency, and the control point level at that time is temporarily taken in or the "DOWN" key
Steps SP1-SP2-SP15-SP16-SP6 according to the operation of 12c
Process is executed to decrease the message content M2 indicating the deviation Δf, the control point level COL at that time is temporarily taken in, and the step S is executed in response to the second operation of the “FINE” key 12a.
P1-SP2-SP3-SP7-SP8-SP9-SP10-SP11-SP6 processing is executed and the control point level CO stored in the register
The L and the flag FLG2 are stored in the table TAB, and the display of the messages M1 and M2 on the tube surface SUR disappears.

In the case of this embodiment, the controller 11 is the AF shown in FIG.
By performing the procedure of T operation, AFT operation is performed not only for the broadcast channel whose center frequency matches the regular center frequency but also for the broadcast channel whose center frequency is shifted from the regular center frequency. It is designed to get you done.

That is, after the controller 11 starts the processing program in step SP20, the controller 11 proceeds to the next step SP21 to change the local oscillation frequency, and then determines whether a set predetermined time (for example, 100 [ms]) has elapsed. Is determined, and when a predetermined time has elapsed, the process proceeds to the next step SP22.

This step SP22 is a step for judging whether or not the selected broadcast channel is the broadcast channel whose channeling point is set by the operator, and the controller 11 sets the flag FLG2 stored in the table TAB. If you get a negative result by falling below,
In step SP23, the comparison reference data VREF is set to the digital data value DO corresponding to the voltage REF by the level setter 6 regardless of the broadcasting channel. On the other hand, if the flag FLG2 is raised and a positive result is obtained in step SP22, the controller 11 advances to step SP24 and the control point level data C stored in the table TAB.
Let OL be the comparison reference data VREF.

After that, the controller 11 proceeds to step SP25 and outputs the comparison input data DAT from the analog / digital conversion circuit 10.
Is read, and in the next step SP26, the magnitude relation between the comparison input data DAT and the comparison reference data VREF is determined. As a result, when it is determined that they have the same relationship, the controller 11 proceeds to step SP27 and returns to the main routine without performing any processing. That is, assuming that the fine inch uning is obtained in the present situation, the process returns to the main routine without changing the local oscillation frequency f _LOS .

On the other hand, the comparison input data DAT is the comparison reference data V
If it is greater than REF, controller 11 goes to step SP2.
At 8, the local oscillation circuit 2 is controlled so that the local oscillation frequency f _LOS is reduced by 100 [k Hz], and conversely, when the comparison input data DAT is smaller than the comparison reference data VREF, the controller 11 proceeds to step SP29. Local oscillation frequency f
Local oscillator circuit 2 to increase _LOS by 100 [k Hz]
Control. After that, the controller 11 sets the time required for the local oscillation frequency f _LOS to finish changing in step SP30 (see step SP21), proceeds to step SP27, and returns to the main routine.

Therefore, by executing the AFT operation processing procedure shown in FIG. 5, the broadcast channel whose center frequency is shifted by the operator or the normal frequency of the broadcast channel is used as it is as the center frequency of the AFT operation. It is possible to determine whether the channel is a broadcasting channel, and if any of the broadcasting channels has a current tuning frequency deviating from the center frequency, an AFT operation can be performed so as to pull it to the center frequency.

In the case of this embodiment, the level change corresponding to one bit in the analog / digital conversion circuit 10, that is, the width of 1 LSB constitutes a dead zone in which the local oscillation frequency f _LOS cannot be varied.

According to the above-described embodiment, for example, even if the operator shifts the center frequency of the tuning from the normal frequency for the broadcast channel in order to avoid the image quality deterioration due to the interfering wave, it is pulled into the shifted frequency.
It is possible to perform AFT operation, and it is possible to effectively avoid adverse effects such as drift on such a broadcast channel.

In the above embodiments, the channel selection device of the present invention is applied to a satellite broadcast receiver, but the present invention is not limited to this, and is widely applied to a receiver having an AFT circuit as needed. can do.

Further, in the above-described embodiment, the local oscillation frequency is varied in units of 100 [kHz] regardless of the deviation between the comparison input data and the comparison reference data (see steps SP28 and 29). However, the local oscillation frequency may be varied when the deviation amount is large and small when the deviation amount is small. If you do this,
In particular, the pull-in time when the power is turned on can be shortened.

Further, in the above-mentioned embodiment, the one in which the output signal to the local oscillation circuit 2 is controlled to perform the AFT operation is shown, but it is possible to perform the AFT operation by changing other characteristic values in the AFT loop. May be. For example, the predetermined level applied by the offset applying circuit 5 may be varied, and a window comparator circuit is used.
In the AFT circuit, the upper and lower threshold level signals of the window comparator circuit may be made variable.

H Effect of the Invention As described above, according to the present invention, a channel selection device capable of arbitrarily setting the center frequency of the AFT operation for each broadcasting channel and performing the AFT operation at the center frequency that provides the best image quality is provided. Can be easily obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a channel selection apparatus according to the present invention, FIG. 2 is a flow chart showing a preset processing procedure of a center frequency of AFT operation, and FIG. 3 is a broadcast channel /
FIG. 4 is a schematic diagram showing a control point level correspondence table, FIG. 4 is a schematic diagram showing a display on a pipe surface for the purpose of explaining an operation procedure of an operator, FIG. 5 is a flow chart showing an AFT operation procedure, FIG. FIG. 7 is a block diagram showing a conventional device, and FIG. 7 is a spectrum diagram used to explain the operation of the conventional device. 1 ... Mix circuit, 2 ... Local oscillator circuit, 3 ... Detection circuit, 4 ... Subtractor, 5 ... Offset applying circuit, 10 ...
… Analog / digital conversion circuit, 11 …… Controller, 12 …… Keyboard input device, 14 …… Memory.

Claims (1)

(57) [Claims] 1. A high frequency signal received by an antenna and a local oscillation signal supplied from a local oscillation circuit are input to a mixing circuit, and the output of the mixing circuit is applied to a detection circuit to output a baseband signal. In the tuning device, the local oscillation frequency adjusting means for adjusting the local oscillation frequency of the local oscillation circuit for each channel in response to the user's operation and the local oscillation frequency adjusting means are used for adjustment. Storage means for storing the adjustment value for each of the channels, detection means for detecting the deviation of the local oscillation frequency, and the selected channel is the channel adjusted by the local oscillation frequency adjusting means, When the adjustment value for the selected channel is stored in the storage means, the detection value detected by the detection means and the storage means are stored in the storage means. The stored adjustment value is compared, and if the selected channel is not the channel adjusted by the local oscillation frequency adjusting means, the detected value detected by the detecting means and the predetermined value. And compare
And a control means for controlling a local oscillation frequency of the local oscillation circuit based on a comparison result.