JPS5829655B2 - Television receiver tuning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television channel tuning device, particularly a frequency synthesizer.
er).

In the United States, carrier frequencies for television over-the-air (vs. cable) broadcasting for HF and UHF channels are assigned by the Federal Communications Commission (FCC).

During radio transmission (ie, while propagating through the air) these frequencies need to be maintained very precisely.

Recently, it has been proposed to use a frequency synthesizer with a phase-locked loop (PLL) to accurately generate local oscillator signals of predetermined frequencies corresponding to a number of channels selected by the viewer.

For example, a tuning device using a phase-locked loop can be found in the L-1972 CO
8/Research on MOS digital integrated circuits
Solid State Data Book (1972 RCAS
olid 5tate Databook on C0
87MO8Integrated C1rcuits)
(5SD-203)” 1-C037MO8IC
A low-power digital frequency synthesizer using
r Digital Frequency Synth
esizer Utilizing C087MO8IC
's ) Digital integrated circuit application No. 1 entitled J.
It is described in ICAN-6716.

Other types of devices for tuning television receivers to standard frequencies are also known.

In a device of the type described in U.S. Pat. No. 3,818,363, two oscillators are provided which alternately and stepwise move from a certain frequency to the radio broadcast channel local oscillator frequency. is swept over a range of .

By counting the number of oscillator sweeps and stops, it is possible to know when a preliminary local oscillator control voltage is approached, close to but slightly below the control voltage suitable for tuning to a particular channel.

After this, an auxiliary sweep circuit increases the control voltage to the proper tuning voltage.

Thus, frequency synthesizer type devices for standard frequency carriers are known.

However, not all television signals are transmitted on standard radio broadcast carriers.

In some television distribution systems, such as in apartment or motel facilities, the television signal is supplied to the receiver through a cable.

In such a cable (or microwave line) system, the modulated broadcast carrier is first demodulated and then modulated again before being delivered to the receiver, so that it is in the vicinity of the standard broadcast carrier. is carried on a different carrier wave.

Therefore, a device is needed to tune the receiver to such non-standard carriers.

The invention is a tuning device for a tuner of a television receiver capable of receiving a composite television signal corresponding to each channel; each of the composite television signals having a carrier wave, the carrier wave being The non-standard frequency carrier wave may be a standard frequency carrier wave or a non-standard frequency carrier wave, and the non-standard frequency carrier wave may be within a first predetermined range including the standard frequency carrier wave and which is wider than the frequency width between the channels. It lies within a narrow range in the vicinity of the standard frequency carrier wave.

The tuning device of the present invention further includes means for receiving a selected one of the television signals and a local oscillation signal to generate an intermediate frequency signal (for example, a mixer 16 to be described later); Automatic fine tuning circuit means (for example, AFT circuit 92 and AFT amplifier 94 described later) that receive signals and generate automatic fine tuning signals; reference oscillator means (for example, crystal an oscillator (40); local oscillator means (e.g., VCO 50, described below) for providing a variable frequency output as said local oscillation signal in response to a supplied control signal; and one of said reference oscillator means and said local oscillator means. a programmable frequency divider (e.g., frequency divider 34 described below) that has an input coupled to the output of the .38) coupled to the output of said programmable splitter and to the output of the other of said reference oscillator means and said local oscillator means for generating a control signal and transmitting said control signal to said local oscillator means; Means for supplying to the oscillator means to control its operating frequency (e.g. phase detector 36, unit 46, switch 4 to be described later)
8) coupled to an output of said automatic fine tuning circuit means and coupled to said programmable frequency divider for controlling said frequency divider to generate a predetermined signal of said automatic fine tuning signal; Control means for varying said programmable number within a second predetermined range determined by said first predetermined range in response to conditions (e.g., counter 42, units 56, 68, described below) ) and ;.

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

FIG. 1 shows the overall configuration of a television receiver included in a channel tuning device according to the present invention.

The radio frequency (RI”) received by the antenna 12
) The signal is amplified by a radio frequency amplifier 14.

The amplified RF signal is fed to mixer 16, where
As will be described later, it is combined with a local oscillation signal of an appropriate frequency extracted according to the selected channel to form an intermediate frequency (IF, ) signal.

The IP signal is amplified by the IF amplifier 18 and then
A video detector 20 is supplied with the signal.

The video detector 20 extracts a video signal containing, for example, a chrominance signal component, a luminance signal component, and a synchronization signal component from the amplified IF signal.

The video signal may include, for example, the chrominance of the video signal,
is fed to a video processing unit 22 containing processing channels for luminance and synchronization signal components, whereby the video tube 2
The image is displayed on 4.

The configurations described so far include, for example, the R.C.N.
Color television service data filter 1
The elements used in the CTC-68 type color television receiver shown in ``974.C-5'' can be used.

In the illustrated apparatus, channel selection information is entered by the viewer using a channel selection keyboard 26.

The keyboard 26 is, for example, a computer type keyboard that selects VHF or UHF channels in decimal format.

The keyboard 26 may be equipped with a matrix circuit for converting decimal information into binary coded decimal (BCD) format, for example.

A binary encoded signal representing channel information is provided to a channel number register 28 through a multi-conductor electrical path 30.

Register 28 converts the binary channel selection information to another binary signal representing the number 1-N corresponding to the currently selected channel.

For this purpose, the register 28 is filled with, for example, the keyboard 2
Read-only memo IJ (
ROM) can be provided.

A binary signal representing the number N is provided via multi-conductor path 32 to a programmable frequency divider 34 .

Frequency divider 34 is configured to divide the frequency of the incoming signal by a number N.

(Hereinafter, this frequency divider 34 may be referred to as a "1/N frequency divider."

) Frequency divider 34 includes a voltage controlled local oscillator 50, a prescaler frequency divider 52, a crystal reference oscillator 40, and a programmable rRJ divider circuit (hereinafter referred to as 1).
/R circuit) 38, a phase detector 36, and a low-pass filter/amplifier 46 to form a phase-locked loop (PLL).

This phase-locked loop configuration and channel selection device constitute a frequency synthesizer of the type described in the previously mentioned Arun-H. Application Note, which is suitable for tuning a television receiver to a standard frequency carrier. It is.

Most of the rest of the block diagram shown in FIG.
For example, it relates to devices for automatically tuning to non-standard frequency carriers, such as in CATv and MATV systems.

A more detailed logical block diagram for such an apparatus is shown in FIGS. 2 and 3.

However, detailed explanations of the specific examples shown in FIGS. 2 and 3 are not provided here.

These examples will be readily understood by those skilled in the art from the description of the receiver tuning apparatus of FIG. 1 below.

To this end, the parts of the embodiment shown in FIGS. 2 and 3 and their interconnections are indicated using the same reference numbers as used in FIG.

Also, in order to relate the embodiments of FIGS. 2 and 3 to FIG. 1, the discussion of FIG. 1 will refer to logic "1" and "0" signals associated with control signals for the tuning device.

These logic "1" and "0" signals correspond to voltages near ground potential and approximately +12 VDC in the logic circuits of FIGS. 2 and 3, respectively.

The logic circuits of FIGS. 2 and 3 can be formed, for example, in CO8/MO8 integrated circuits using such voltages.

The television receiver tuning device of FIG. 1 operates in two modes.

The first mode is non-scanning
mode of operation for tuning the receiver to the standard frequency carrier assigned to the selected channel; in this first mode the programmable
N frequency divider 34 and programmable 1/R frequency divider 38 are each set to predetermined values.

In a non-scanning mode of operation for tuning the receiver to a standard frequency carrier, the viewer-operated scanning mode enable switch 54 is placed in the open position as shown.

Therefore, "5cAN ENABLE control signal (1'-8
The absence of the "CAN ENABLE" control signal, i.e., the complement of the "5CAN ENABLE" control signal ("1") is passed through conductor 58 to switch logic unit 56 and through conductor 60 to count preset logic unit. 62 to disable devices associated with receiving non-standard carriers, as described below.

1-8 CAN ENABLE J In response to the control signal,
The switch logic unit 56 has rsTOP 5CAN (
scan stop) Nu I J control signal (logic ``0''), which is applied through conductor 90 to clock energizing unit 68 such that the clock pulse from 1/A divider 66 is applied to up/down counter 42. Clock input (conductor 1
14).

As a result, the counter 42 operates in a scanning mode (sca
1/R frequency divider 38, such as in
The number R is not changed.

In either mode of operation, the viewer selects a channel by pressing or activating the appropriate key on the channel selection keyboard 26.

Channel number register 28 receives two signals representing channel selection information from keyboard 26 and retrieves from its memory two signals representing the number N corresponding to the selected channel.

The binary information representing this number N is programmable 1/N
It is input to a frequency divider 34, which divides the frequency of the incoming signal by a number N.

Regardless of non-scanning or scanning modes, channel number register 28 retrieves from memory the binary number representing the number N corresponding to that channel whenever a new channel is selected; l'
-8TART PULSE (start pulse)” control signal (
logic "1").

This rSTART PULSE J control signal is connected to conductor 7
8 to switch logic unit 56 to reset flip-flops 5612 and 5614 (FIG. 3).

The functions of these flip-flops will be described later.

In response to the 5 TART PULSEJ control signal, control latch logic unit 56 transmits the control signal (logic "O") to conductor 8.
8, which causes a combiner/AFT (automatic fine tuning) switch 48 to couple the output (conductor 122) of the low-pass filter and amplifier unit 46 via conductor 128 to the control terminal of the voltage controlled oscillator vcoso. to form the phase-locked loop configuration described above.

The rsTART PULSE J control signal is also provided to count preset logic unit 62, which unit 6 receives new information from channel number register 28.
Reset 2.

Find an appropriate number N of programmable branching units 34, and
In addition to its function of generating the 5TART PULSE J control signal, channel number register 28 generates three band switching control signals (each a logic "1").

These three signals are (1) a UHF control signal when a channel in the UHF region (for example, channels 14-83) is selected; (2) a UHF control signal when a channel in the low VHF region (for example, channels 2-6) is selected; ) is selected
OV control signal, and (3) H when a channel in the high VFF region (e.g., channels 7 to 13) is selected.
This is an IV control signal.

The band switching control signal is provided to the count control logic unit 62 along with the 5CANENABLEJ control signal;
This causes count preset logic unit 62 to select the appropriate number R.

These band switching control signals are also provided to voltage controlled tuning elements in the vcoso, e.g. baracque diodes, and prescaler 1/ to frequency divider 52 by suitable known methods (not shown). The frequency of the input signal of the /N frequency divider 34 is controlled according to the frequency band of the selected channel.

The values of N and R for tuning the receiver to the standard frequency carrier are shown in the table shown in FIG. 6 in the examples labeled "N Scan and Non-Scan" and "R Non-Scan."

The values in this table correspond to the case where the frequency of the crystal oscillator 40 is 5 MHz and the prescaler divider 52 is configured to divide the frequency of the output signal of the CO 50 by 256.

As we will see, the value of N is 45.75 MI (z
video carrier (standard IP in most U.S. receivers)
Frequency (MHz) of the local oscillation output signal of the VCO 50 necessary to generate a frequency difference IP signal with a video carrier wave)
is equal to the number representing

(For example, if the local oscillation output signal frequency of vcoso is 1
00MI (when z, N=100).

Initially, a channel is selected and a programmable 1/N divider 34 and a programmable 1/R divider 38 are selected.
When set, ■C050 oscillates at an arbitrary frequency (for example, at a certain point in the center of the selected band).

■ The operating frequency of the CO50 is low-pass filtered until the error output signal from the phase detector 36 indicates that there is no phase or frequency difference between the output signals of the 1/N frequency divider 34 and the 17R frequency divider 38. - Varies depending on the DC control signal output of the amplifier unit 46.

At this time, the prescaler divider 52 is connected to the VCO 50,1/
A phase-locked loop corresponding to a programmable 1/N divider 34, a phase detector 36, a programmable 1/R divider 38, a crystal oscillator 40, and a low-pass filter/amplifier unit 46 provides the output of the VCO 50 with crystal oscillator 4
A local oscillation signal of frequency fLO having the following relationship with respect to the frequency fXosc of the output signal of 0 is generated.

The output signal of the low-pass filter/amplifier unit 46 is
The local oscillator signal is varied sufficiently for a particular band over a frequency range that exceeds the spacing between adjacent channels, preferably wide enough to tune the receiver to all channels within that particular band. must have a reasonable amplitude range.

Thus, for example, in the low VHF region, the low pass filter and amplifier unit 46 controls the receiver on channels 2 and 3.
, 4.5 or 6, sufficient control voltage is provided between the first and second voltages.

The local oscillator output signal of VCO 50 is provided to mixer 16 where it is combined with the output signal of RF amplifier 14 in the usual manner to produce a frequency equal to the frequency difference between the received carrier and the local oscillator signal (e.g. 45.75MHz
) is formed into an IP multiplied signal having a video carrier wave.

The IP multiplied signal is amplified by an IF amplifier 18 and then video information is extracted by a video detector 20.

The video signal is processed by a signal processing unit 22 and an image is reproduced on the screen of a video tube 24.

If the viewer desires to receive a signal from a non-standard carrier distribution system (e.g., a CATV or MATV distribution system), the scan mode enable switch 54 is placed in the closed position, placing the tuning device in a second or scan mode of operation. “5CA” for
Generates the N ENABLEJ control signal (logic ``0'').

In this second or scanning mode, a programmable 1/N
Frequency divider 34 is again first set to a constant value corresponding to the selected channel.

However, the programmable 1/R divider 38 initially
Frequency division ratio (di
vision ratio ) or divide value (in the first mode, divider 38 is set to this value);
Incremental changes towards a second value greater than the value corresponding to said associated standard frequency carrier until tuning is achieved or until the second value is reached as detailed below. (increment)

In scanning mode (as in non-scanning mode)
The viewer selects a channel by pressing the appropriate key on the channel selection keyboard 26.

In response, binary information representing the number N is input to programmable 17N frequency divider 34.

Furthermore, the channel number register 28 is set to “5TARTPU”.
The LSEJ control signal (a logic "1" control signal is generated and is applied to switch logic unit 56 to reset flip-flops 5612 and 5614.

In response to the 5TART PULSE J control signal, switch logic unit 56 generates a control signal (logic ``0'') on conductor 88, which causes combiner/AFT switch 48 to initially - Connect the output terminal of the amplifier unit 46 to the control terminal of the VCO 50.

The l'-5 TART PULSEJ control signal also resets the meter control output logic unit 62 before new data is received from the channel number register 28.

Also, as in the non-scanning mode, the channel number register 28 generates either a UHF, LOV or HIV control signal depending on the frequency band to which the selected channel belongs.

Depending on either the HIV or LOV control signal provided by channel number register 28 and the JSCAN ENABLEJ control signal provided by switch 54, counting preset logic unit 62 determines whether the same channel is selected during the non-scanning mode. The up/down counter 42 is supplied with two signals representing a first predetermined value below the value to which the number R is set.

The first predetermined value corresponding to each channel input to the up-down counter 42 during the scan mode is shown in the table of FIG.
It is shown in the column "Start R".

The counting preset logic unit 62 also includes H■■ and L
Complementary signals HIV and LOV of the OV control signal are generated.

These complementary signals are applied through multi-conductor traces 64 to a scan stop logic unit 70 which controls the scan stop logic unit 70 (when the selected channel is in the high VHF region or low VHF region).
set to one of two predetermined values (according to whether it is in the region).

This value is greater than the value to which the number R is set during non-scanning mode.

The second predetermined value corresponds to the maximum value that the number R can increase to reach during the scanning mode.

These second predetermined values corresponding to the sixth channel are
It is shown in the "Stop R" column in the table of the figure.

In response to the 5cAN ENABLE J control signal, the switch logic unit 56 switches the JSCANSTOP No.
J control signal ("5cAN 5TOR (scan stop) N
o, I J Generates a logic "1" representing the absence of the control signal, i.e. its complement.

In response to these clock signals, up-down counter 42 changes the number R by a fixed amount in the direction of a first predetermined value toward a second predetermined value.

VCO (voltage controlled oscillator) 50.1/prescaler divider 52, programmable 1/N frequency divider 34, phase detector 36, crystal oscillator 40, programmable 1/R frequency divider 38 and low frequency The phase-locked loop consisting of the pass filter/amplifier unit 46 operates in the same way as in the non-scanning mode to calculate the frequency fLO of the local oscillator signal using equation (1).
control according to

However, when each successive clock pulse of the clock signal output of the 1/A frequency divider 66 reaches the up-down counter 42, the number R will be as shown in the "ΔR" column of the table of FIG. Continuously increased by a fixed amount.

When A is set to 2, the predetermined change in H for different channels is 2.

As a result, the frequency of the local oscillation signal is decreased by a fixed amount.

In the case of A-2, the start frequency, stop frequency, and frequency change of the local oscillation signal for each channel are shown in the table shown in Figure 6, rfLo start, rfLO stop, and 1-.
It is shown in each column of ΔfLOJ.

As in the non-scanning mode, the local oscillator output signal of VCO 50 is combined with the output signal of RF amplifier 14 in mixer 16 to form a modulated IF signal.

The carrier frequency of this IP signal is increased by a constant amount within a range corresponding to the frequency range of the local oscillator signal and in direct relation.

The scanning range for each channel is such that the local oscillator signal is combined in mixer 16 with the received non-standard frequency carrier to produce a modulated IF signal having a video carrier of a predetermined frequency, e.g. 45.75 MHz. is chosen broadly to include the local oscillator signal frequencies required by the local oscillator.

When the IP carrier decreases by a certain amount, an automatic fine tuning (AFT) frequency discriminator unit 92 connected to the output of the IF amplifier 18 distinguishes the frequency of the F carrier from 45.75.
Generates a voltage related to the frequency deviation between MHz and MHz.

FIG. 4 shows the S for AFT circuit 92 with typical voltage and frequency values for the embodiments shown in FIGS. 2 and 3.
4 shows a curved frequency versus voltage characteristic curve 412;

As will be seen, the S-shaped characteristic curve 412 corresponds to a small portion (fr) of the frequency interval (6 MHz) between channels.
frequency deviation (±25KHz)
has an amplitude range between the minimum and maximum amplitudes corresponding to .

The direction in which the frequency of the modulated IP carrier is scanned is also shown in FIG.

The output signal generated at the (g) output terminal of AFT circuit 92 is provided to threshold detector 82 through conductor 104 and monitored there.

The threshold detector 82 detects 1-T when the voltage at the (g) output terminal of the AFT circuit 92 exceeds a predetermined threshold 414 (FIG. 4).
HRESHOLD (threshold)” control signal (logic 1-IJ)
occurs.

The 1'-THRESHOLDJ control signal is provided through conductor 106 to switch logic unit 56 and sets flip-flop 5612 (FIG. 3) in this unit 56.

The AFT signal appearing at the (to) terminal of AFT circuit 92 is supplied to AFT amplifier 94 via conductor 124 and amplified.

The gain of the AFT amplifier 94 is such that the amplitude range between the first and second voltages of the amplified AFT signal is determined by the low-pass filter.
It is selected to be approximately the same as the amplitude range of the output signal of amplifier unit 46.

That is, since the same VCO 50 is controlled by the output signal of the low-pass filter/amplifier unit 46 and the AFT signal, the amplitude range of the amplified output signal of the AFT amplifier 94 is limited to the range in which this output signal is applied to the VCO s o. When selected, it should be such that it provides substantially the same voltage as the output signal voltage of the low pass filter and amplifier unit 46 for the selected channel.

The first and second voltages of the amplified AFT signal are AF
Corresponding to the frequency deviations associated with the maximum and minimum voltages of the frequency discrimination characteristic associated with the T-circuit 92.

FIG. 5 shows a frequency versus voltage characteristic curve 512 of the amplified AFT output signal of AFT amplifier 94 with typical voltage and frequency values for the embodiments shown in FIGS. 2 and 3. .

Also shown is the direction in which the frequency of the modulated IP carrier is scanned.

In addition, VC corresponding to channels in the low VHF frequency range
The level of control voltage supplied to O50 is also shown approximately.

It should be understood that similar characteristic curves exist for channels in the high VHF region.

FIG. 5 also shows a low-pass filter/amplifier unit 4.
A waveform 514 that changes in a stepwise manner similar to the output signal of No. 6.
is partially shown.

This waveform 514 causes the modulated IF carrier to be incremented by a fixed amount.

Comparator 84 receives the output signal of low-pass filter and amplifier unit 46 (waveform 514
) is compared with the output signal of AFT amplifier 94 (waveform 512) provided through conductor 98 to generate a COMP-ARISON control signal (logic ``1'') when these voltages are equal.

This rCOMPARISONJ control signal is provided through conductor 102 to switch logic unit 56 and sets its flip-flop 5614 (FIG. 3).

The reason why the control signal is generated when the output signal of the low-pass filter/amplifier unit 46 and the output signal of the AFT amplifier 94 are equal is that when switching from control using a phase-locked loop to control using an AFT signal. VCO5
This is to ensure that the operation of 0 is carried out smoothly.

Flip-flop 5612 is set in response to the THRESHOLDJ control signal, and flip-flop 5614
When rCOMPARISONJ is set in response to the rCOMPARISONJ control signal, switch logic unit 56 generates a control signal (a logic "1" on conductor 88) that connects the output terminal of low-pass filter and amplifier 46 to VCO 50. , and instead couples the output terminal of AFT amplifier 94 to the control terminal of vcoso.

Thereafter, the amplified AFT signal controls the frequency of the local oscillation signal output from the CO50.

■The frequency at which the control input signal to the CO50 is switched from the output signal of the low-pass filter/amplifier unit 46 to the amplified AFT signal may vary due to temperature changes, changes in the values of circuit elements, etc. When the frequency of the oscillation signal drifts, the AFT circuit 92 operates in a negative feedback manner and supplies an amplified AFT signal that counters the frequency change due to the drift.

rTHRESHOLDJ control signal is an amplified AFT
Indicates that the signal is changing in the correct direction for AFT control.

Threshold 414 in FIG. 4 corresponds to threshold 516 in FIG.

If the amplified AFT signal reaches threshold 516, switch 48 switches the amplified AFT signal from AFT circuit 92 to
If the FT signal were to be coupled to VCO 50, no AFT control would be performed.

This is because the control voltage applied to vcoso varies in the wrong direction, ie, along slope 518 of curve 512 instead of slope 520.

"COMPARISONJ control signal is the amplified AF
It shows that the T signal is providing the control signal given to the VCO 50.

When this control signal is given to ■CO50, VCO50
generates a local oscillator signal having a frequency sufficiently close to the frequency of the local oscillator signal associated with the selected channel.

For example, assume that the selected channel is channel 4.

The voltage of the amplified AFT signal is level 516 (Figure 5).
When the synthesizer/AFT switch 48 is activated,
When the output terminal of the AFT amplifier 94 is coupled to the control input terminal of ■C050, the control voltage given to ■αno0 is
It corresponds to a channel close to channel 2 rather than the control voltage required for channel 4.

In this way, the control of vcoso is JTHRESHOLD
When both the J control signal and the rCOMPARISONJ control signal are present, the AFT
Switched to control.

Furthermore, the "'I" HRESHOLD J control signal and rCO
When the MPARISONJ control signal is generated, switch logic unit 56 applies a STOP5CAN Nn1J control signal (logic ``0'') to conductor 90, thereby causing
This prevents the clock signal from reaching the clock input of up-down counter 42, which further causes programmable 1/R divider 38 to
ent) is prevented, thus terminating the scanning operation.

If AFT control is not performed before the number R reaches its final value (column "R Stop" in the table of FIG. 6), the scan stop logic unit 70 will
A J control signal (logic "0") is generated on conductor 108 to prevent the clock signal from reaching the clock input of up-down counter 42, thereby terminating the scan.

At this point, the video the viewer sees is of poor quality, so the viewer can either select another channel, or select another channel and take a new scan.
You can select the originally selected channel again.

The frequency of the modulated IF carrier wave is decreased by a constant amount by decreasing the frequency of the local oscillator signal by a constant amount.

This is desirable because the initially available carrier will be the desired video carrier rather than the audio carrier of the adjacent channel.

This can prevent or minimize mistuning.

When the scan mode enable switch 54 is closed and the receiver is ready to tune to a non-standard frequency carrier, the channel number register 28
If the UHF control signal is generated, switch logic unit 56 switches rscAN 5 in response to the UHF control signal.
TOP Nnl J Generates control signal and 1/A frequency divider 6
6 is prevented from reaching the clock input of the up-down counter 42 via the clock activation unit 68.

Therefore, the number R of 1/R dividers 38 is not increased quantitatively when a UHF channel is selected, regardless of whether scan mode enable switch 54 is pressed.

This configuration is provided because most television distribution systems separate the frequency of the UHF carrier from another UHF carrier.
There is no reconversion for distribution at HF frequencies, so no scan mode operation is required when a UHF channel is selected.

However, the tuning device of the present invention can be modified to scan non-standard frequency UHF carriers.

Although the examples shown in FIGS. 2 and 3 are not explained in detail for the reasons mentioned above, the following can be understood regarding the logic circuit shown in FIG.

The CD4027 integrated circuit included as part of the programmable 1/R divider 38 is a flip-flop that divides the frequency of the output signal of the CD4059 integrated circuit, also included in the divider 38, by two. .

As a result, the CD 40 forming an up-down counter 42
The number set in the 29 integrated circuit counter will be a percentage of the corresponding value of H shown in the table of FIG.

Furthermore, in order to form the number of most significant digits (MSD) corresponding to the 100th position and the number of least significant digits (LSD) corresponding to the 1st position of the number corresponding to the value of "Stop R", "8" is not required, so these "Stop R" MSD and LSD
Only binary signals representing rlJ, r2J and "4" are provided to scan stop logic unit 70 to form .

Also, the number 1 supplied by the up-down counter 42
No binary signal is provided to the scan stop logic unit 10 to form the 00 position.

This is because the number in the 100th place is high VHF even in the low VHF region.
The same is true in the HF region, and it cannot be increased.

In FIG. 1, the incrementing of the modulated IF carrier causes the programmable 1/R divider 38 to
ing), the frequency of the F carrier is divided by 17N, as shown by multiconductor trace 126 coupled between up-down counter 42 and programmable 1/N frequency divider 34. It is also possible to make a quantitative decrease by decreasing the value input to the device 34 by a constant amount.

Furthermore, in the tuning device of FIG. 1, in order to prevent the receiver from tuning to the audio carrier of an adjacent channel,
Although the frequency of the carrier wave has been described as being changed by a quantitative decrease, it will be understood that the frequency of the carrier wave may be changed by a quantitative increase.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a channel tuning device according to the present invention used in a television receiver, FIG. 2 is a logic diagram of a specific example of a part of the tuning device shown in FIG. 1, and FIG. FIGS. 4 and 5 show specific examples of other parts of the tuning device in FIG. 1, partly schematically and partly in logical diagrams; FIGS. FIG. 6, a diagram showing characteristic curves, is a chart for explaining the operation of the tuning device of FIG. 1. 34.38... Frequency divider, 36, 46, 48...
. . . Phase detector, low-pass filter/amplifier unit, synthesizer/AFT switch (operating frequency control means of local oscillator means), 40 . . . Crystal oscillator (reference oscillator means), 42, 56 .68...Up-down counter, switch logic unit, clock activation unit (programmable number change control means), 50...
...voltage controlled oscillator (local oscillator means), 92...
...AFT circuit (automatic fine tuning circuit means).

Claims (1)

Claims: 1. A tuning device for a tuner of a television receiver capable of receiving composite television signals corresponding to each channel, wherein each of the composite television signals has a carrier wave; The carrier wave may be a standard frequency carrier wave or a non-standard frequency carrier wave, and the non-standard frequency carrier wave may be a frequency within a first predetermined range including the standard frequency carrier wave and between the channels. means for receiving a selected one of the television signals and a local oscillator signal to generate an intermediate frequency signal; automatic fine tuning circuit means for receiving the signal and generating an automatic fine tuning signal; reference oscillator means for generating a reference signal of a predetermined frequency; local oscillator means for supplying as an oscillating signal; an input coupled to the output of one of said reference oscillator means and said local oscillator means, the frequency of the signal supplied to said input being programmable; a programmable frequency divider for producing an output signal having a divided frequency; an output of the programmable frequency divider and an output of the other of the reference oscillator means and the local oscillator means; means for generating a control signal and providing the control signal to said local oscillator means to control its operating frequency; - coupled to an output of said automatic fine tuning circuit means and said programmable frequency divider; and controlling the frequency divider to control a second predetermined range determined by the first predetermined range in response to a predetermined signal condition of the automatic fine tuning signal. A tuning device for a television receiver, comprising: control means for varying the programmable number within a range.