JPH0145247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a channel selection device that limits the receivable frequency range in a television receiver.

(Technical Background) In general, television receivers anticipate in advance that the upper or lower limit of receivable frequencies will change significantly due to errors in parts used in the channel selection device, changes over time, changes in temperature, etc. The frequency band (hereinafter referred to as sweep range) is set to be sufficiently wider than the actual broadcast frequency band (hereinafter referred to as stationed range).

For example, as shown in FIG. 1, a variable capacitance diode 2 is used as a tuning element of a tuner 1, and a memory 91
The channel information stored in Keyboard 9
2, the band switching signals Bl, Bh, Bu and tuning voltage Vt are read out to the control unit 3 by the switch operation in step 2.
In a so-called "voltage synthesizer type channel selection device" which receives a predetermined channel in addition to the tuner 1 by converting it into the tuner 1, when an automatic sweep channel selection operation is performed, the channel selection unit 4 outputs a signal as shown in Fig. 14. A tuning voltage (sweep signal) that changes in a sawtooth pattern and a band switching signal Bl, Bh, Bu that has a rectangular waveform as shown in Fig. 5c.
is output for each receiving band. Normally, the variable range of tuning voltage Vt, which corresponds to the sweep range, is 0.2 to
It is designed to be around 33V. Further, the variation range of the tuning voltage corresponding to the fixed station range is set to several volts to 24 volts.

In Figures 6 to 8, the horizontal axis is the tuning voltage Vt, the left vertical axis is the VHF band frequency, and the right vertical axis is the VHF band frequency.
Taking the frequency of the UHF band, channel numbers for each band are attached to both vertical axes, and VHF high band,
This is a graph of the tuner's reception characteristics in the VHF low band and UHF band. Here, FIGS. 6 and 7 show an example of the reception characteristics of the Tuner for West Germany, and FIG. 8 shows an example of the reception characteristics of the Tuner for Canada.

In West Germany, the VHF high band station coverage ranges from channels E5 to E12, as shown in Figure 6.
The VHF low band range is set to E2 to E4 channels, and the UHF band range is set to E21 to E60 channels.

Here, a signal (tuning voltage) with a peak value of 33V shown in FIG. 14 that gradually increases the voltage in a sawtooth pattern to sweep the selection range, and a band switching signal shown in FIG. 5c are applied to the tuner 1. When a sweep operation is performed over the entire area, an extra sweep operation is performed in each band as described below. In other words, as is clear from the reception characteristics in Figure 6, in the VHF low band, the tuning voltage corresponding to the upper limit channel E4 of the station range is 10V, but since it is swept beyond this to 33V, the voltage from 10V to 3V is The channel change corresponding to the change up to (corresponding to about 1.5 channels from E4 to a little over E5) becomes an extra sweep operation. Similarly, in the VHF high band, the station range has a sweep operation beyond the tuning voltage 18V corresponding to the upper channel E12 to 33V, so the range from 18V to 33V (E12
(equivalent to approximately 2.5 channels upward) is an extra sweep operation. Furthermore, in the UHF band, exceeding the tuning voltage of 23V corresponding to the upper channel E60,
Since the sweep operation is performed up to 33V, the range from 23V to 33V (corresponding to 10 channels from E60 to approximately E70 channels) is an extra sweep operation. Similarly, an extra sweep operation is performed below the lower limit channel of each band.

On the other hand, as the demand for radio waves as a means of communication increases, in order to make effective use of the available frequency bands, in recent years frequencies have been allocated for private and public communications, even close to the standard television broadcasting frequency band. As a result, even ordinary television equipment can receive some private communications without any modification, and the question of how to maintain the confidentiality of communications becomes a problem.

In order to deal with the above-mentioned problems, there is a movement in various countries to legally restrict the receivable range of television receivers to only commercial television broadcasts.

For example, the FTZ standard in West Germany or the DOC standard in Unada strictly regulate the upper and lower limits of frequency bands that can be received by television receivers.

For example, in West Germany's FTZ standard, UHF
The upper limit of the sweep range for the band is restricted to 878MHz as shown in FIG. Also, Canada's DOC standards have an upper limit on the VHF high band.

A simple method to satisfy the above standards is to match the lower limit frequency of each band to the lowest value Vl (e.g. 0.2V) of the tuning voltage variable range, and match the upper limit frequency at the highest value of the variable range (e.g. 33V). It is conceivable to adjust the tuning frequency of each tuner so as to do so. However, since the variable range of the tuning voltage Vt varies depending on the tuning section 4, even if the tuning frequency is adjusted by the tuner alone, the tuning frequency will shift due to the variation in the tuning voltage. Therefore, in this case. It is necessary to adjust the receivable range after installing the tuner in the receiver, which is extremely troublesome in terms of production.

(Summary of the Invention) The present invention includes a reference voltage generating section 7 that generates a plurality of types of reference voltages set for each receiving band in order to regulate the upper limit of the sweep range for each receiving band, and A switching section 74 that can be switched in conjunction with a band switching operation is connected to the generation section, and a reference voltage for each reception band is generated by switching the switching section, and the reference voltage is made the peak value of the tuning voltage. This paper reveals a channel selection device that can regulate the upper limit of the sweep range for each reception band.

(Example) The present invention will be specifically described below based on an example shown in the drawings.

The example was written assuming the FTZ standard in West Germany and the DOC standard in Canada.
Of course, it can be implemented similarly in other standards as well.

FIG. 1 shows an example of a receiving device embodying the present invention, in which the control unit 3 Then, select "0" corresponding to the receiving frequency and band.
A channel signal 32 and a band signal 33 of a predetermined number of bits consisting of a "1" signal are formed, or the signals 32 and 33 are read out from the memory 91 and applied to the tuning voltage generation section 5 and band switching section 6 of the tuning section 4, respectively. do.

FIG. 3 shows the configuration of the channel selection section 4 that complies with the FTZ standard in West Germany.

As shown in FIG. 3, the tuning section 4 includes a bit rate multiplier 51, a voltage converter 52, a tuning voltage generating section 5, a band switching section 6, and a switching section 7.
4, the channel signal 32 and the band signal 33 are decoded, and the tuning voltage generator 5 generates a tuning voltage proportional to the value of the channel signal 32.
Vt from the band switching unit 6 to the band signal 33
A band switching signal of a predetermined voltage, for example, about 15V, is output from the output terminals 61, 62, and 63 corresponding to the numerical value of
Bl, Bh, and Bu are outputted and applied to the tuner 1, respectively.

The tuning voltage generator 5 includes a reference voltage generator 7 and a low-pass filter 53.

The bit rate multiplier 51, the voltage converter 52, and the low-pass filter 53 are connected in series, and the voltage converter 52 and the low-pass filter 53 are connected in series.
A reference voltage generating section 7 is interposed between the reference voltage generating section 3 and the reference voltage generating section 7, and a switching section 74 is connected to the reference voltage generating section 7.

The configuration of each of the above components will be described in detail below.

The bit rate multiplier 51 is constituted by a shift register or a counter as is well known, and modulates the input channel signal 32 in pulse width to obtain a duty ratio ( It outputs a pulse signal _P1 of τ/T).

The voltage converter 52 is constituted by a transistor switch, applies a reference voltage outputted from a reference voltage generation section 7 to be described later to the emitter terminal of the transistor, and has a collector grounded.
The pulse signal is applied to the base side. Therefore, the pulse signal P ₁ input to the voltage converter 52
is boosted without changing the waveform as shown in Figure 13b by turning the transistor switch ON and OFF, and the peak value becomes the reference voltage value Vs (Vs ₁ or
A pulse P ₂ is formed which corresponds to Vs ₂ ).

As shown in FIG. 3, the reference voltage generating section 7 includes a constant voltage diode 71 that stabilizes the input voltage Vi and generates a first reference voltage Vs ₁ , and a first reference voltage obtained from the constant voltage diode 71. It is composed of a pair of first and second resistors 72 and 73 for voltage dividing Vs ₁ , and generates a second reference voltage Vs ₂ lower than the first reference voltage Vs ₁ at the connection point of both resistors. be. The connection point between both resistors 72 and 73 is connected to the emitter end of the voltage converter 53, and the second resistor 73 is grounded via a switching section 74. Therefore, in conjunction with the on/off operation of the switching section 74, either the first reference voltage Vs ₁ or the second reference voltage Vs ₂ is applied to the emitter terminal of the voltage converter 52.

The switching section 74 is constituted by a transistor switch, and its collector/emitter end is interposed between the resistor 73 and the ground, and its base end is connected to the output terminal 63 of the band switching section 6 corresponding to the UHF band. . Therefore, when receiving the VHF band, the switching section 74 is opened and the first
The reference voltage Vs ₁ is applied to the emitter end of the voltage converter 52, the switching unit 74 is closed during UHF band reception, and the second reference voltage Vs ₂ obtained by dividing the first reference voltage Vs ₁ is applied to the emitter end of the voltage converter 52. Applied to the emitter end.

The pulse signal _P2 converted to the predetermined reference voltage level as described above is smoothed by the low-pass filter 53 and converted into DC. As a result, as shown in Figure 13c, the tuning voltage becomes Vt=(τ/T)Vs.
Vt is obtained.

Therefore, channel signal 32 and band signal 3
3 from the lower limit to the upper limit of the variable range, the duty ratio of the pulse signal _P1 increases in accordance with the change in the channel signal 32,
As a result, the level of the tuning voltage increases as shown in FIG. 5b.

Then, at the upper limit of the sweep range, that is, when the duty ratio of the pulse signal _P1 becomes 100%, the tuning voltage Vt reaches a peak as shown in FIG. 5b, and this peak value is in the VHF band. corresponds to the first reference voltage Vs ₁ and corresponds to the second reference voltage Vs ₂ in the UHF band.

A DC auxiliary power supply 8 is interposed between the low-pass filter 53 and the tuning voltage application terminal 12 of the tuner 1. The DC auxiliary power supply 8 divides the output signal Bl from the VHF low band switching terminal 61 using a variable resistor 81 and a resistor 82, and supplies the lowest tuning voltage, which is the lower limit value in the sweep range, to the sliding terminal of the variable resistor 81. It generates Vl (for example, 0.2V), and the voltage Vl is connected to the tuning voltage application terminal 12.

Therefore, even when the output voltage from the tuning voltage generator 5 decreases during VHF low band sweep, at least a voltage of Vl will be applied to the tuner as shown in FIG. 5b.

Note that in the VHF high band and UHF band, the lower limit value of the tuning voltage drops to OV without being limited by the above-mentioned Vl.

FIG. 2 shows an embodiment of the tuner 1, in which received VHF and UHF signals are each amplified by a high frequency amplifier 13, and then mixed with a signal input from a local oscillator 15 in a mixer 14. , is converted to an intermediate frequency IF. This signal is further subjected to signal processing similar to conventional methods to reproduce an image. The local oscillator 15 uses a variable capacitance diode 2 as a tuning element, and by applying the tuning voltage Vt and band switching signals Bl, Bh, and Bu output from the tuning section 4 described above to the diode 2, After selectively receiving a predetermined television signal by changing the oscillation frequency of the local oscillator 15, image reproduction is performed by performing substantially the same signal processing as in the conventional art.

Adjustment of the sweep range at the stage of assembling the channel selection device equipped with the channel selection section 4 shown in FIG. 3 is carried out as follows.

First, to set the upper limit of the sweep range in the UHF band, set the Zener voltage Vs ₁ of the constant voltage diode 71 included in the reference voltage generator 7 to 33V,
The Zener voltage is stepped down by 0.833 times by resistors 72 and 73 to obtain a reference voltage Vs ₂ of 27.5V. Normally, the standard variation in a constant voltage diode with a Zener voltage of 33V is about ±3V, so the variation range of the reference voltage _Vs2 is 25 to 30V.

In the UHF band reception characteristics shown in Figure 6,
When the tuning voltage changes within the above variation range of 25 to 30V, at the upper limit of 30V, the E68 channel, that is, 854M
Hz reception is possible, but reception of 878MHz, which is regulated by the FTZ standard, is impossible, so FTZ
It is possible to meet the standards. Also, since it is possible to receive the E63 channel at 25V, which is the lower limit of the variation range, this is the upper limit of the station coverage in West Germany.
E60 channel can also be received without any problem.

In addition, in countries other than West Germany, the upper limit of the UHF band is the E69 channel, so there will be channels that cannot be received using the above method. Figure 10 shows
The reference voltage generator 7 used in a channel selection device that can be used in all countries including West Germany is shown, one valve pressure resistor 72 is a semi-fixed resistor 72a, and the constant voltage diode 71 has a Zener voltage Vz of 33~ Use one with a variation range of 36V. When the tuning section 4 including the reference voltage generating section 7 is manufactured, the semi-fixed resistor 72a is adjusted to make the reference voltage Vh equal to 33V, and when the tuner 1 is manufactured, after turning the channel to the full upper limit, Apply 33V to the tuning voltage application terminal, so that 870MHz can be received with this voltage.
Adjust the tuner's local oscillation frequency.

By the way, the upper limit of the West German FTZ standard is:
878MHz shown in the UHF band reception characteristics in Figure 7
Channel E69, the upper limit of the station coverage in European countries other than West Germany, has a frequency of 862M.
It is specified to be received at Hz.

The above value of 870MHz is the upper limit of E69 channel (equivalent to 862MHz) in countries other than West Germany.
This value is 8MHz higher than 8MHz, and 8MHz lower than 878MHz, which is the upper limit limit of the West German FTZ standard.
Therefore, temperature changes, voltage changes, AFT pull-in characteristics,
Even if ±5MHz, which is the deviation value of the local oscillation frequency caused by changes over time, is taken into consideration, the upper limit of the sweep range is within the range of 865MHz to 875MHz. There is no problem with reception.

Next, if you want to limit the lower limit of the VHF low band,
Taking into consideration that if the tuning voltage is lowered too much, the performance of the tuner will deteriorate, and if the voltage is raised too much, the capacity of the variable capacitance diode 2 will be insufficient in the VHF low band, the lower limit tuning voltage Vl in the VHF low band is determined. Set to around 1.5V. After that, when adjusting tuner 1, the above tuning voltage is
Set the lower limit of the sweep range under Vl to 4MHz lower than the lower limit of the stationed range (E2 channel). With this, the FTZ standard can be satisfied even if the above-mentioned error of ±5 MHz is taken into account.

On the other hand, in the tuning section 4, the variable resistor 81 is adjusted to set the voltage output from the tuning section 4 to the lower limit tuning voltage Vl.

In this way, it is possible to adjust the upper and lower ends of the receivable frequency with the tuner 1 and the tuning section 4 separated.

FIG. 4 shows the configuration of the tuning section 4 that complies with the DOC standard in Canada, in which the VHF high band switching signal Bh is used as a switching signal for the switching section 74, and the lower limit is set by the switching signal Bh. By also setting the voltage, the upper and lower limits (Vl, Vs ₂ ) of the tuning voltage Vt are regulated only during VHF high band reception, as shown in FIG. 5a.

FIG. 8 shows an example of the current reception characteristics of each band in Canada, and FIG. 9 shows the reception characteristics of the VHF high band whose upper and lower limits are regulated as described above. As shown in FIG. 9, the lower limit of the sweep range matches the I channel of the CATV band, and the upper limit of the sweep range matches the J channel of the CATV band, thus avoiding overlap with the CATV band.

11 and 12 show other embodiments of the reference voltage generating section 7. In FIG. 11, a constant voltage diode 75 with a Zener voltage of Vs ₂ is used instead of the resistor 73. In FIG. 12, two sets of constant voltage diodes 71 and 75 with Zener voltages of Vs ₁ and Vs ₂ are connected in parallel and used.
By switching alternately in the channel section 74,
Two types of reference voltages can be generated.

As described above, the present invention generates two types of reference voltages by interposing the reference voltage generating section 7, which has a simple configuration consisting of a constant voltage diode and a resistor, between the voltage converter 52 and the low-pass filter 53. At the same time, the reference voltage is appropriately switched in conjunction with the band switching operation to regulate the upper limit of the tuning voltage,
This limits the upper limit of the receivable frequency range, making it possible to reliably and easily limit the receivable frequency band without degrading performance by making only minor changes to conventional equipment. . Of course,
Adjustment of the receivable frequency range can be performed independently for both the tuner 1 and the tuning section 4.
It has extremely excellent effects such as easy assembly and adjustment process.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a channel selection device, FIG. 2 is a block diagram of a tuner, FIG. 3 is an electric circuit diagram of the channel selection device according to the present invention, and FIG. 4 is another embodiment of the channel selection device. An electric circuit diagram showing an example; FIGS. 5a to 5c are waveform diagrams showing the output signals of the tuning section during sweep; FIGS. 6 to 9 are graphs showing the receiving characteristics of the tuner; FIGS. 10 and 11. 12 and 12 are electric circuit diagrams showing other embodiments of the reference voltage generating section, FIGS. 13 a to 13 c are signal waveform diagrams until the input pulse signal in the tuning section is converted into a tuning voltage, and FIG.
The figure is a waveform diagram of a sweep signal in a conventional device. 1... tuner, 2... variable capacitance diode,
7... Reference voltage generating section, 71... Constant voltage diode, 72, 73... Resistor, 74... Switching section.

Claims (1)

[Claims] 1 Consists of a tuner 1 using a variable capacitance diode 2 as a tuning element, and a tuning section 4 that supplies a tuning voltage to the variable capacitance diode 2, and the tuning section 4 is configured to tune at the peak of the tuning voltage. a reference voltage generator 7 that generates a reference voltage that corresponds to the reference voltage value; and a voltage converter 52 that processes an input pulse signal having a duty ratio corresponding to the frequency to be received and boosts the level of the pulse signal to the reference voltage value. In the voltage synthesizer type tuning device, which includes a low-pass filter 53 that smoothes the output of the voltage converter 52 and converts it into a tuning voltage, the reference voltage generator 7 has a voltage that is connected to the band switching operation. By switching the switching unit 74, a plurality of reference voltages Vs ₁ or Vs ₂ are switched and output according to the reception band, and the input pulse signal is switched by the sweep channel selection operation. A tuning device characterized in that a tuning voltage when a duty ratio reaches a maximum value is regulated to a reference voltage corresponding to a reception band among the plurality of reference voltage values Vs ₁ or Vs ₂ . 2 The reference voltage generator 7 includes a voltage regulator diode 71 that stabilizes the input voltage to a first reference voltage Vs ₁ , and a voltage regulator diode 71 that is connected in series with each other and has one end connected to the voltage regulator diode 71.
A pair of voltage dividing resistors 72 and 73 connected to the output terminal of
and a switching section 74 connected to the other end of the series connection of the voltage dividing resistors 72, 73 and grounded in a switchable manner. 2. The channel selection device according to claim 1, which switches the voltage generated at the connection point between the first reference voltage Vs ₁ and the second reference voltage Vs ₂ lowered by the voltage dividing resistor 72. 3. The reference voltage generating section 7 includes a plurality of constant voltage diodes connected in parallel, and a switching section 74 switches and outputs a plurality of different reference voltages generated by each constant voltage diode. channel selection device.