JPS5828932B2 - Television receiver tuning device - Google Patents

Description

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

In the United States, carrier frequencies for television over-the-air (vs. cable) broadcasting for VHF 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 accurately.

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 is the R1972 ECO, published by R.C.
8/Research on MOS digital integrated circuits
Solid State Data Book (1972 RCA
5olid 5tate Databook on
CO8/MO8Integrated C1rcuit
Low-Power Digital Frequency Synthesizer Using rCO8/MO8IC in (5SD203)J
r Digital Frequency 5y
nthesizer UtilizingCO8/MO
8IC's')J, Digital Integrated Circuit Application No. 1-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. 8,818,363, 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 present invention provides for both standard frequency carriers for regular VHF and UHF channels and non-standard frequency carriers located anywhere near these standard frequency carriers.
Relating to a device used for tuning a television receiver.

The tuning device is provided with controlled oscillator means for generating a local oscillator signal.

Mixer means combine the local oscillator signal with the modulated received carrier to generate a modulated intermediate frequency carrier.

A programmable frequency dividing means allows the frequency of the local oscillator signal to be set to the first frequency corresponding to the currently selected channel.
The frequency is divided by the number of .

Phase detection means generates a first control signal for maintaining a predetermined phase and frequency relationship between the divided local oscillation signal and the reference frequency signal.

The first control signal has an amplitude range spanning the first and second amplitudes sufficient to vary the local oscillator signal over a frequency range that exceeds the spacing between adjacent channels.

Frequency discriminator means generate a discriminator signal representative of a frequency deviation of the intermediate frequency carrier from a constant frequency (eg, the nominal frequency of the video carrier).

This discriminator signal has an amplitude range between a minimum amplitude and a maximum amplitude corresponding to a frequency deviation that is a fraction of the spacing between channels.

Means for deriving a second control signal from the discriminator signal is coupled to the frequency discriminator.

This second control signal is the first and second control signal of the first control signal.
has an amplitude range between the first and second amplitudes that is approximately the same as the amplitude of the first and second amplitudes.

The first and second amplitudes of the second control signal correspond to frequency deviations of the intermediate frequency carrier between respective frequency deviations associated with the maximum and minimum amplitudes of the discriminator signal.

The scanning means scans the local oscillation signal within a frequency range near the frequency of the selected local oscillation signal.
,) will be done.

The local oscillation signal can be scanned, for example, by increasing the frequency of the reference frequency signal by a fixed amount relative to the divided local oscillation signal.

The deviation between the frequency of the intermediate frequency carrier wave and the fixed frequency falls within a certain predetermined range, and the amplitude of the control signal is substantially equal to the amplitude of the first control signal for the currently selected channel. Means are provided for inactivating the scanning means when the scanning means is activated.

The first and second control signals are selectively coupled to the controlled oscillator means by switch means.

When the scanning means is deactivated, the switch means disconnects the first control signal from the controlled oscillation means and instead supplies a second control signal to the controlled oscillation means.

Thereafter, the second control signal controls the frequency of the local oscillator signal.

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

FIG. 1 shows the overall structure of a television receiver having a channel tuning device according to the present invention.

Radio frequency (RF) received by antenna 12
The signal is amplified by 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 IF 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-Nee Color Television Service Data File 197, published by R-C-Nee Corporation.
The elements used in the CTC-68 type color television receiver shown in 4.C-5J 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 a 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 a number "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 divider 52, a crystal reference oscillator 40, and a programmable divide by "R" 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 Arsini Application Note, which is suitable for tuning a television receiver to a standard frequency carrier. It is something.

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 CAT 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 numerals as used in FIG. 1.

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 "O" 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 17
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, the rSCAN ENAB-LEJ control signal (rs
The absence of the ckN ENABLE (scan enable) control signal, i.e., a logic "1" representing the complement of the 5CAN ENABLE J control signal) is passed through conductor 58 to switch logic unit 56 and through conductor 60 to count preset logic unit 62. and disables equipment associated with receiving non-standard carriers, as described below.

r 5CAN ENABLEJ In response to the control signal,
Switch logic unit 56 includes r 5TOP 5CAN
(Scan Stop) A1” control signal (logic “0”), which is applied through conductor 90 to the clock energizing unit 68 so that the clock pulses from the 1/A divider 66 are activated by the up/down counter 42. clock input (conductor 11
4).

As a result, the counter 42 operates in a scanning mode (sca
1/R frequency divider 38 that performs nning mode r
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 a programmable 17N
It is input to a frequency divider 34, which divides the frequency of the incoming signal by a number N.

Regardless of the non-probe mode or scan mode, the channel number register 28 retrieves from memory the binary number representing the number N corresponding to that channel whenever a new channel is selected; rs
TART PULSE" control signal (logic "1").

This rSTART PULSE J control signal is provided via conductor 78 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 r5TART PULSEJ signal, switch logic unit 56 generates a control signal (logic "O") on conductor 88, which causes synthesizer/AFT (automatic fine tuning) switch 48 to operate as a low-pass filter amplifier. The output of unit 46 (conductor 122) is coupled to the control terminal of voltage controlled oscillator (VCO) 50 via conductor 128 to form the phase-locked loop configuration described above.

The r 5TART PULSEJ control signal is also provided to count preset logic unit 62 to reset this unit 62 before new information from channel number register 28 enters.

Take an appropriate number N of programmable frequency dividers 34 and r
5TART PULSE] In addition to its function of generating control signals, 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 region (for example, channels 2-6 is selected); LOV when selected
(3) HIV control signal when a channel in the high HF region (for example, channels 7 to 13) is selected.

The band switching control signal is provided to the counting preset logic unit 62 along with the "SC N EN BLEJ control signal, so that the counting preset logic unit 62
Select an appropriate number R.

These band switching control signals are also applied to voltage controlled tuning elements in the VCO 50, e.g. The frequency of the input signal of the 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 1/2 prescaler divider 52 is configured to divide the frequency of the output signal of the VCO 50 by 256.

As we will see, the value of N is a frequency difference IP signal having a 45.75 MHz video carrier (the standard IF video carrier in most receivers in the United States) mixed with the received respective standard frequency carrier. Frequency (MHz) of local oscillation output signal of VCO50 required to rawhide
is equal to the number representing

(For example, if the local oscillation output signal frequency of VCO 50 is 1
00MI (when z, N=10F).

Initially, a channel is selected and a programmable I/N divider 34 and a programmable 1/R divider 38 are selected.
When set, VCO 50 oscillates at an arbitrary frequency (eg, some point in the middle of the selected band).

The operating frequency of VCO 50 is low-pass until the error output signal from phase detector 36 indicates that there is no phase or frequency difference between the output signals of 1/N divider 34 and 1/R divider 38. It changes according to the DC*+leg signal output of the filter/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 frequency divider 34, a phase detector 36, a programmable 1/R frequency divider 38, a crystal oscillator 40, and a low-pass filter/amplifier unit 46 provides the output of vcoso with crystal oscillator 4
A local oscillation signal having a frequency fLO having the following relationship with respect to the frequency f 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 between the first and second voltages is provided.

The local oscillator output signal of the VCO 5,0 is fed to a mixer 16 where it is mixed with the output signal of the 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. (For example, 45.75MHz)
An IF signal is formed having a video carrier of .

The IF signal is amplified by IP amplifier 18 and then video information is extracted by 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 wishes to receive a signal from a non-standard carrier distribution system (e.g., a C-person TV or an M-person TV distribution system), the scan mode enable switch 54 is placed in the closed position and the tuning device is set to the second or scan mode. rSCA to put into operational mode
Generates the N ENABLEJ control signal (logic ``O'').

In this second or scanning mode, the programmable /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
visionratio ) or division value (in the first mode, frequency divider 38 is set to this value) and then corresponds to said associated standard frequency carrier. is incremented by a predetermined increment toward a second value greater than that value until tuning is achieved or until the second value is reached as described in more detail below.

In scanning mode, just like 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 1/N frequency divider 34.

Furthermore, the channel number register 28 is set to “5TARTPU”.
LSE] control signal (logic ``1'' control) is generated and is applied to switch logic unit 56 to reset flip-flops 5612 and 5614.

In response to the rSTART PULSEJ control signal, switch logic unit 56 generates a control signal (logic [0'') on conductor 88 so that combiner/AFT switch 48 initially The output terminal of unit 46 is connected to the control terminal of VCO 50.

The r5TART P-ULSEJ control signal also resets count preset logic unit 62 before new data from channel number register 28 enters.

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 rSCAN ENABL-E control signal provided by switch 54, count preset logic unit 62 is selected during the non-scan mode. The up-down counter 42 is provided with two signals representing a first predetermined value below the value to which the number R is set for the same channel.

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".

Count preset logic unit 62 also includes
Generates auxiliary signals HIV and LOV for OV leg control.

These complementary signals are applied to a scan stop logic unit 70 through a multi-conductor trace 64, which controls the unit 7d to two predetermined values (depending on whether the selected channel is in the high HF or low VHF region). Set it to one side.

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 channels are shown in the "Stop R" column in the table of FIG.

r 5CAN ENABLEj In response to the control signal,
Switch logic unit 56 allows the clock signal from 1/A divider 66 to reach the clock input of up-down counter 42.
I J Control signal CC5CAN 5TOP (scanning stop)
It generates a logical ``1'' representing the absence of the ``1'' 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 variation of R for the various channels is 2.

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

The start frequency, stop frequency, and frequency change of the local oscillation signal for each channel in the case of A2 are shown in the table shown in Figure 6 for rfLO start, fLo stop, and △f
It is shown in each column of LOJ.

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 IP signal.

This IF multiplied signal carrier frequency is increased by a fixed amount in a direct relationship within a range corresponding to the frequency range of the local oscillator signal.

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

As the IP carrier decreases by a fixed amount, an automatic fine tuning (AFT) frequency discriminator unit 92 connected to the output of the IP amplifier 18 distinguishes the frequency of the IF 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 fraction (fra) of the frequency interval (6 MHz) between channels.
frequency deviation (±25 KHz'
) has an amplitude range between the minimum and maximum amplitudes corresponding to .

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

The output signal generated at the (→ output terminal) of the AFT circuit 92 is
It is provided through conductor 104 to threshold detector 82 where it is monitored.

The threshold detector 82 detects rTHR when the voltage at the ←) output terminal of the AFT circuit 92 exceeds a predetermined threshold 414 (FIG. 4).
ESHOLD" control signal (logic "1").

The THRESHOLDJ control signal is provided through conductor 106 to switch logic unit 56, which unit 5
6, flip-flop 5612 (FIG. 3) is set.

The human FT signal appearing at the ←) 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.
The amplitude range is selected to be approximately the same as the amplitude range of the output signal of the amplification 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 human FT 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 vcoso. The output signal voltage of the low pass filter and amplifier unit 46 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 ■F carrier to be incremented by a constant amount.

Comparator 84 receives the output signal (waveform 514 ) of low-pass filter amplifier unit 46 provided through conductor 100 .
) is compared with the output signal of AFT amplifier 94 (waveform 512) provided through conductor 98 to generate a JcoMp-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 performed smoothly.

Flip-flop 5612 is set in response to the rTHRESHOLDJ control signal, and flip-flop 5614 is set in response to the rTHRESHOLDJ control signal.
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 amplifier 46 to VCO 50. Separated from the control terminal, the output terminal of AFT amplifier 94 is instead coupled to the control terminal of VCO 50.

Thereafter, the amplified AFT signal controls the frequency of the local oscillation signal output of the VCO 50.

From the frequency at which the control input signal to vcoso is switched from the output signal of the low-pass filter/amplifier unit 46 to the amplified human FT signal, due to changes in temperature, changes in circuit element values, 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.

“The THRESHOLDjFilJ inhibition signal indicates that the amplified AFT signal is changing in the correct direction for performing 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 ■C050 changes in an incorrect direction, that is, along the slope 518 of the curve 512.

The rCOMPARISONJ signal indicates that the amplified control T signal is providing the control signal given to the CO50.

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 AFT amplifier 94 is coupled to the control input terminal of vcoso, the control voltage provided to vcoso corresponds to a channel near channel 2, rather than the control voltage required for channel 4.

In this way, the control of the VCO 50 is performed by rTH'RE-8H
When both the OLDJ and rCOMPARISONJ control signals are present, from control by the phase-locked loop,
Switched to AFT control.

Furthermore, the rTHRESHOLDj control signal and the rcOMPA
When the RIsON control signal is generated, the switch unit 56 outputs rSTOP 5CAN, /! 6. lJ control signal (logic ``0'') on conductor 90, which prevents the clock signal from reaching the clock input of up-down counter 42, and which further The frequency circuit 38 increases further (incre
ment) is prevented, thus terminating the scanning operation.

If the AFT crawler is not controlled before the number R reaches its final value (column "R Stop" in the table of FIG. A logic "0") is generated on conductor 108 to prevent the clock signal from reaching the clock power 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, the switch logic unit 56 switches the rSCAN 5
TOP 16. The IJ control signal is generated to prevent the clock signal from the 1/A divider 66 from reaching the clock input of the up-down counter 42 via the clock enable 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 1/2 of the corresponding value of H shown in the table of FIG.

Furthermore, 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"? Ma,"
Since "8" is not required, only binary signals representing Ill, r2J and "4" are provided to scan stop logic unit 70 to form these "stop R" MSDs and LSDs.

Also, the number 1 supplied by the up-down counter 42
No binary signal is provided to the scan stop logic unit 70 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 IP carrier causes the programmable 1/R divider 38 to be incremented by the decrementing of the modulated IP carrier.
ting), but the frequency of the IP carrier is controlled by an up/down counter 42 and a programmable 1/2
As shown by the multi-conductor circuit 126 coupled between the 1/N frequency divider 34 and the 1/N frequency divider 34, the value input to the 1/N frequency divider 34 can also be decreased by a fixed 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 table for explaining the operation of the tuning device of FIG. 1. 16...Mixer (mixer means), 26,28゜42...Channel selection keyboard, channel number register, up/down counter (frequency division control means)
, 34, 38...- Frequency divider (frequency division means), 364
6, 48... phase detector, low pass filter/amplifier unit, synthesizer/AFT switch (first control means), 40... crystal oscillator (stable frequency signal source), 42, 48, 56, 92...up/down counter, combiner/AFT switch, switch logic unit, AFT circuit (second control means), 50...
...Voltage controlled oscillator (controllable oscillation means).

Claims (1)

[Scope of Claims] 1. The radio frequency carrier has a standard frequency, or the radio frequency carrier has a non-standard frequency lying near the standard frequency. An apparatus for tuning a receiver to: a controllable oscillator means for generating a local oscillation signal; a source of a relatively stable frequency signal; and between the local oscillation signal and the stable frequency signal. frequency dividing means for dividing the frequency of at least one of the local oscillation signal and the stable frequency signal by a controllable number in response to at least one of the local oscillation signal and the stable frequency signal to establish a predetermined frequency proportional relationship; a first control means coupled between said frequency dividing means and said controllable oscillation means for controlling the frequency of said local oscillation signal in accordance with said predetermined frequency proportionality relationship; mixer means for generating an intermediate frequency signal comprising at least one information-bearing carrier wave in combination with said local oscillator signal; the frequency of said information-bearing carrier wave being such that the frequency of said radio frequency carrier wave is said standard frequency; and a frequency division control means coupled to the frequency division means for determining a controllable proportionality factor between the frequency of the local oscillator signal and the frequency of the stable frequency signal; The controllable proportionality coefficient has a predetermined value when the frequency of the radio frequency carrier wave is the standard frequency; controlling the frequency of said local oscillator signal by varying it by an amount within a predetermined range determined by an expected deviation from a standard frequency; A tuning device for a television receiver, comprising second control means for reducing the difference.