JPS6138285Y2 - - Google Patents

Description

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

In general, in television receivers, the receivable frequency band is determined in advance by anticipating that the upper or lower limit of receivable frequencies may change significantly due to errors in parts used in the channel selection device, changes over time, changes in temperature, etc. is designed to be sufficiently wider than the actual broadcasting frequency band.

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 one-type channel selection device" that converts to tuner 1 and receives a predetermined channel, when the automatic sweep channel selection operation is performed, the selection is performed as shown in Figures 6a and b. A sweep signal that changes in a sawtooth shape from the local part 4 and a rectangular wave band switching signal Bl, Bh, corresponding to the signal sweep position.
Bu is output. Normally, the variable range of the tuning voltage Vt is designed to be about 0.2 to 36V, and it is set so that the upper limit of the broadcast band can be received when the tuning voltage is several volts below the upper limit voltage. As shown in FIG. 6b, the tuning voltage with a peak voltage of 36V and
When a 5V band switching signal is applied to each tuner 1, as is clear from the reception characteristics shown in Fig. 4,
Approximately 2 channels upwards in VHF low band, approximately 3 channels upwards in VHF high band, and approximately 3 channels upwards in UHF band.
You can receive extra.

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 up to the very vicinity of 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 has become 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.

Examples include the FTZ standard in West Germany and the DOC standard in Canada, both of which strictly regulate the upper and lower limits of frequency bands that can be received by television receivers.

Taking West Germany's FTZ standard as an example, it allows only one channel of margin at the upper end of the UHF band and the lower end of the VHF low band, that is, about 7 to 8 MHz.

As a simple method to satisfy the above standards, the lower limit frequency of each band is matched to the lowest value of the tuning voltage variable range, and the tuning frequency of each tuner is adjusted so that the highest value of the variable range matches the upper limit frequency. It is possible to adjust it. But the tuning voltage
Since the variable range of Vt varies depending on the tuning section 4, it is not possible to adjust the tuning frequency with the tuner alone, and it is necessary to adjust the receivable range after installing the tuner in each receiver. It's extremely troublesome.

The present invention divides the voltage stabilized by a voltage regulator diode using a resistor and regulates the upper limit of the tuning voltage, which can be implemented with minor changes to conventional equipment without degrading performance. The settings are
To provide a tuning device that can be easily and reliably adjusted since it can be performed using a tuner alone.

The present invention will be specifically described below based on embodiments shown in the drawings.

Note that although the embodiment has been described assuming the FTZ standard in West Germany, it goes without saying that it can be implemented in the same way for other standards as well.

FIG. 1 shows an example of a receiving device embodying the present invention. In 3,
Form a channel signal 32 and band signal 33 of a predetermined number of bits consisting of "0" and "1" signals corresponding to the reception frequency and band, or read out the signals 32 and 33 from the memory 91 and apply them to the tuning section 4. do.

The channel selection section 4 includes a channel selection section 5 and a band switching section 6, as shown in FIGS.
The band switching unit 6 outputs a tuning voltage Vt proportional to the value of 2, and outputs a predetermined voltage, e.g.
Band switching signals Bl, Bh, and Bu of about 15V are output and applied to tuner 1, respectively.

The channel selection section 5 includes a bit rate multiplier 51, a voltage converter 52, and a low pass filter 53.
1, the channel signal 32 is pulse width modulated and then boosted by a voltage converter 52. Voltage converter 5
2 is a transistor switch, which applies a reference voltage Vh output from a reference voltage generation section 7 (to be described later) to the collector, and at the same time applies the pulse signal to the base side, thereby maintaining the waveform of the input pulse signal. , only the peak value is used as the reference voltage Vh
rise to.

The reference voltage generating section 7 converts and stabilizes the input voltage Vi into a Zener voltage Vz using a constant voltage diode 71, and then divides the Zener voltage Vz using resistors 72 and 73 to generate a predetermined reference voltage Vh. .

The pulse signal voltage-converted as described above is smoothed by a low-pass filter 53 and converted into a direct current, thereby obtaining a tuning voltage Vt whose peak value coincides with the reference voltage Vh as shown in FIG.

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. , changed to 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.

The upper limit of the receivable frequency range of the channel selection device is adjusted as follows.

Constant voltage diode 7 included in reference voltage generator 7
Set the Zener voltage Vz of 1 to 33V, resistor 72,
73, step down the Zener voltage by 0.833 times,
Obtain a reference voltage Vh of 27.5V. Normally the zener voltage is
Since the standard variation in 33V constant voltage diodes is about ±3V, the variation range of the reference voltage Vh is 25 to 30V. As is clear from the reception characteristics shown in FIG. 4, this voltage range is E68
In addition to satisfying the new FTZ standard, the E63 channel is received at 25V, which is the lower limit of the variation range, so channels below the upper limit reception channel E60 in West Germany, which enforces the above standards, can be received without any problem.

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. FIG. 8 shows a reference voltage generator 7 used in a channel selection device that can be used in all countries including West Germany, in which one voltage dividing resistor 72 is a semi-fixed resistor 72a, and a voltage regulator diode 71 is connected to a constant voltage diode 71. Use one whose Zener voltage Vz has a variation range of 33 to 36V. A semi-fixed resistor 72 is used when manufacturing the tuning section 5 including the reference voltage generating section 7.
a to match the reference voltage Vh to 33V, and when manufacturing tuner 1, after turning the channel to its upper limit, 33V was applied to the tuning voltage application terminal, and the tuner was adjusted so that it could receive 870MHz with this voltage. Adjust the local oscillation frequency. As you can see from the reception characteristics in Figure 5, the value of 870MHz is 8MHz higher than the upper limit channel and 8MHz lower than the upper limit of the new FTZ standard, so it is caused by temperature changes, voltage changes, AFT pull-in characteristics, changes over time, etc. Even if we take into account the local oscillation frequency deviation value, ±5MHz, which occurs due to this, it satisfies the new FTZ standard and there is no problem in receiving the E69 channel.

As described above, the present invention divides the Zener voltage of the voltage regulator diode 71 using the resistors 72 and 73, sets the upper limit Vh of the tuning voltage, and regulates the upper limit of the receivable frequency, which is different from the conventional method. By only making minor changes to the device, the reception frequency band can be reliably and easily restricted without any deterioration in performance. Furthermore, since the receivable frequency range can be adjusted separately for both the tuner 1 and the tuning section 4, it has excellent effects such as easy manufacturing.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the outline of the tuning device, Fig. 2 is a block diagram of the tuner, Fig. 3 is an electric circuit diagram of the tuning device according to the present invention, and Figs. 4 and 5 are the receiver of the tuner. Graph showing the characteristics, Figure 6a,
7b and 7 are waveform diagrams showing output signals from the tuning section, and FIG. 8 is an electric circuit diagram showing another embodiment of the reference voltage generation section. 1... tuner, 2... variable capacitance diode,
4...Tuning selection section, 7...Reference voltage generation section, 71...
Constant voltage diode, 72, 73... Voltage dividing resistor.

Claims (1)

[Claims for Utility Model Registration] (1) A tuner that uses a variable capacitance diode as a tuning element, and a voltage converter that converts an input pulse signal with a pulse width corresponding to the frequency to be received into a predetermined size. In a voltage synthesizer type tuning device, the voltage stabilized by a constant voltage diode is divided by a resistor. A reference voltage generating section is provided which generates a predetermined reference voltage by using the reference voltage generating section, and the peak value of the tuning voltage is set by using the reference voltage of this reference voltage generating section as the peak value of the output obtained from the voltage converter, and the peak value of the tuning voltage can be set and received. A tuning device that determines the upper limit of the frequency range. (2) The channel selection device according to claim 1, wherein at least one of the voltage dividing resistors that divide the voltage stabilized by the voltage regulator diode is a semi-fixed resistor.