JPS58993Y2 - antenna device - Google Patents

Description

[Detailed description of the invention] The present invention relates to an antenna device for a television receiver using an electronically tuned tuner. The purpose is to provide a compact and inexpensive antenna device that can perform sensitive image reception.

In recent years, the size of television receivers has become smaller 75 times.
Opportunities to receive television broadcasts outdoors and elsewhere are increasing.

In such cases, it is necessary to receive the image using a circular antenna (hereinafter referred to as the built-in antenna) of the television receiver, and it is important to be able to receive the image with high sensitivity.

As is well known, the frequency of television broadcasting is a very wide frequency band ranging from the VHF band to the UHF band, as shown in Table 1.

V of television broadcasting with frequency relationship like (f)
In order to receive the HF LOW band with good sensitivity, the built-in antenna requires a certain length, and the length of this built-in antenna cannot be made very short. There was a contradiction that it was impossible to downsize.

Considering the length of the built-in antenna in an ideal state, 4
λ (here, λ is the wavelength of the image receiving signal) is required, and for example, approximately 83 FL is required for 90 MH2, and approximately 1.47 FL for 54 MH2.

For this reason, conventionally, even in such small television receivers, the length of the built-in antenna was around 1 m to prevent a decrease in sensitivity, which hindered the miniaturization of television receivers. It had been a long time coming.

In addition, as another conventional example, as shown in FIG. 1, a dummy antenna 2 is added to the ground end side of the built-in antenna 1,
The built-in antenna 1 and the dummy antenna 2 constitute an irregular doublet antenna, and the high-frequency signal induced in these is guided to the tuner 4 via a cable 3 to prevent a decrease in sensitivity. However, the dummy antenna 2 requires a certain length or a certain size, which ultimately poses a problem in reducing the size of the entire television receiver.

Furthermore, conventionally, as shown in FIG.
0 to match with the built-in antenna 1 to prevent a decrease in sensitivity, but with this method, the receiving frequency band is VHF as shown in Table 1.
Since the frequency band is wide ranging from the UHF band to the UHF band, there is a drawback that it is not possible to select the loading coil 10 that is optimal across all frequencies.

That is, in this case, if the inductance of the loading coil 10 is determined to be optimal in the VHF LOW band, the sensitivity will be extremely reduced in the VHF HIGH band or UHF band.

In an attempt to downsize television receivers, electronically tuned tuners (hereinafter referred to as electronic tuners) are being used.

It is well known that such a receiving system using an electronic tuner □ cannot continuously receive signals over a wide band from the VHF band to the UHF band as shown in Table 1 above.

Therefore, in such an electronic tuner, as shown in the example of FIG.
A voltage BS for band switching (
(hereinafter referred to as the Bs voltage) is applied to switch the reception band.

Table 2 shows an example of the required BS voltage.

In the present invention, an antenna device as shown in FIG. 4 is constructed in a television receiver using such an electronic tuner.

One embodiment will be described below based on FIG. 4.

In FIG. 4, a loading coil 10 is inserted between the antenna 1 and the high frequency signal input terminal of the electronic tuner 20,
In parallel with this loading coil 10, a capacitor 11
and switching diode 12 are connected, and this loading coil 10 and switching diode 1 are connected in series.
The connection point between the capacitor 11 and the switching diode 12 is connected to the BS terminal of the electronic tuner 20 through a resistor 13.

In the above configuration, when the BS voltage required for the BS terminal of the electronic tuner 20 is shown in Table 2 as an example, the switch S
When is on the a side, that is, in the LOW band position of vHF, the Bs voltage is applied to the BS terminal, and the BS voltage appears at the cathode terminal of the switching diode 12 through the resistor 13, keeping the switching diode 12 in the cut-off state ( However, the supply voltage ycc<Bs.

), only the loading coil 10 is inserted into the antenna circuit, and the built-in antenna 1 and electronic tuner 2
0 can be matched, and the sensitivity can be increased.

Also, switch S is b*! When on the IF or C side, that is, when receiving VHF HIGH band and UHF broadcasting, the BS terminal is grounded and the switching diode 1
2, a forward bias current flows through the resistor 14j13, and the switching diode 12 becomes conductive.

At this time, the loading coil 10 is short-terminated by the DC blocking capacitor 11 and the switching diode 12, and the high frequency signal induced in the built-in antenna 1 does not pass through the loading coil 10, but is directly applied to the electronic tuner 20, and the sensitivity This will prevent a decrease in

As explained above, according to the present invention, the electronic tuner 20
By using the receiving band switching voltage Bs to connect or disconnect the loading coil according to the receiving band, it is possible to respond to a wide range of receiving signals from the VHF band to the UHF band shown in Table 1 above. Sufficient sensitivity can be obtained with a short antenna.

In addition, by using the receiving band switching voltage in one case to control the switching diode for controlling the loading coil on and off, there is no need to install a separate switch or voltage source, or in other words, there is no need to increase costs. Can be controlled.

In addition, since the parts used are small, such as diodes and other elements, they do not interfere with the miniaturization of television receivers, unlike conventional dummy antennas, which is extremely advantageous in practical terms. It is something.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the configuration of an antenna device in each conventional example, FIG. 3 is a diagram showing the configuration of an electronically tuned tuner, and FIG. 4 is a circuit diagram of an antenna device in an embodiment of the present invention. It is. 1... Antenna, 10... Loading coil, 11... Capacitor, 12...
...Switching diode, 13.14...
Resistor, 20...Electronic tuner, S...
switch.

Claims (1)

[Scope of utility model registration request] A loading coil is inserted between the built-in antenna that receives the television signal and the high frequency signal input terminal of the electronic tuner, and a switching diode is connected in parallel with the loading coil in an alternating current manner, and the circuit is connected to the electronic tuner. One end of the switching diode is connected to a voltage source of a receiving band switching voltage to be switched via a switch for switching the receiving band of the electronic tuner, and the switching diode is controlled on/off according to the receiving band, thereby controlling the loading. An antenna device characterized in that a coil is connected to and disconnected from the built-in antenna.