JPS63185102A - Antenna system - Google Patents

Abstract

PURPOSE:To provide a sufficient sensitivity even for a short rod antenna by using the rod antenna so as to receive the UHF and VHF band high channel and using the rod antenna and a loop antenna together for the VHF low channel. CONSTITUTION:The rod antenna 10 is excited at the reception of the UHF band. A signal receiving by the rod antenna 10 is inputted to a television tuner 14 without being given to a loop antenna 12 by the UHF choke coil 18 selected to have a sufficient inductance at the UHF band. At the reception of the VHF high channel, the rod antenna 10 is also excited. In the case of the reception by the rod antenna 10, the signal is given to the television tuner 14 without being given to the loop antenna 12 because of the presence of a filter circuit 21. At the reception of the VHF band low channel, the loop antenna 12 is excited and then the signal is received.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an antenna device used in a small portable television receiver.

[Conventional technology]

Small portable television receivers, especially liquid crystal television receivers, are expected to have a large market in the future as small portable information devices following pocket calculators, pocket translators, and the like.

Currently, liquid crystal television receivers are becoming smaller, thinner, and more sophisticated, and this trend is becoming more pronounced as IC and other circuit component technologies improve.

However, most commonly used antennas are relatively long stretchable rod antennas, and it cannot be said that they have necessarily kept pace with the miniaturization, thinness, and performance improvements of LCD television receivers. .

[Problem that the invention seeks to solve]

In order to receive television broadcasts outdoors, in a vehicle, or even indoors, an LCD television receiver must receive images using an antenna built into the LCD television receiver. It is desirable to be able to receive images with high sensitivity.

Therefore, efforts have been made to improve the performance of LCD television receivers themselves, such as the tuner itself, but due to the restrictions of reducing power consumption for portable purposes, the characteristics of active elements such as transistors are approaching their limits. There are many cases in which antennas are used, but new developments are desired in terms of smaller antennas and higher performance.

Conventionally, liquid crystal television receivers have used not only rod antennas but also so-called earphone antennas or headphone antennas that use lead wires of earphones or headphones as antennas. These earphone antennas and headphone antennas are always close to the user's body, and their directivity tends to change depending on the movement of the user's body, and the impedance of the antenna also changes significantly, so it may be affected by chaining misalignment or chiming input. This caused problems such as inconsistency. However, recently, monopole antennas called stretchable rod antennas or whip antennas have become mainstream.

Currently, television broadcasting covers a very wide frequency band from the VHF band to the UHF band, and the low channel of the VHF band is 90 to 108 MHz.

VHF band high channel is 170-220MHz, U
The HF band ranges from 470 to 770 MHz. Ideally, the length of the rod antenna is 1 wavelength of the received signal.
A length of 74 is required.

For example, the video carrier frequency of the VHFI channel is 91.2.
At 5MHz, its 1/4 wavelength is approximately 82cm, 34
The video carrier frequency of the channel is 107.75MI (in z, its 174 wavelengths are approximately 70 crn.In order to receive the low channel of the VHF band of television broadcasting with good sensitivity, the length of the rod antenna must be made too short. Currently, rod antennas of 70 to 80 cm are used as built-in antennas for LCD television receivers, and if they are made any shorter to make them more compact, this will lead to a sudden drop in sensitivity in the VHF band low channel. Ta.

Therefore, even if the main body of the LCD TV receiver excluding the antenna section becomes smaller, there are problems with the storage space for the antenna or the inability to downsize the built-in antenna itself. It is becoming difficult to miniaturize.

It is an object of the present invention to solve the above-mentioned problems and to promote miniaturization and high performance of liquid crystal television receivers.

[Means for solving problems]

A short rod antenna of approximately half or less of the conventional antenna length is used for receiving high channels in the UHF band and VHF band of television broadcast waves, and the rod antenna and a loop antenna are used together for receiving low channels in the VHF band,
This structure prevents a decrease in sensitivity when receiving VHF band low channels, and promotes miniaturization and higher performance of the entire LCD TV testing device.

[Effect]

Since liquid crystal television receivers are small, they are often placed on a desk to receive images, but there are cases in which users hold them in their hands while receiving images. In this case, the human body is particularly affected.

In other words, the proximity of the human body causes a decrease in sensitivity or a large change in sensitivity. This is due to an increase in short circuit capacity and loss due to the human body.

The human body is considered to be a lossy dielectric material for electromagnetic waves, and reflects and absorbs radio waves, but in the electromagnetic field distribution near the human body, the electric field component is weak, the magnetic field component is high in density, and its strength is extremely low. It reaches a maximum in the vicinity and then decreases again.

Therefore, when receiving an image very close to the human body, a loop antenna or ferrite antenna that is compatible with magnetic fields is more advantageous than a rod antenna that is compatible with electric fields.

However, ferrite antennas are extremely disadvantageous compared to air-core loop antennas because the ferrite core has problems in terms of weight, volume, cost, frequency loss, and damage.

Although it is possible to obtain a gain comparable to that of a rod antenna with a loop antenna if the loop area is made large, there is a restriction that the antenna is as large as the housing because it is built into a liquid crystal television receiver.

Also, compared to a rod antenna, the tuning mechanism is much more complex when it comes to wideband reception. It has already been mentioned that the frequency band of the VHF band high channel is 170 to 220 MHz, and among these, the 1/4 wavelength of the video carrier frequency of 171.25 M11z for 4 channels is about 44 Cm. This is approximately 82c of the 174 wavelengths of VHF 1 channel.
It is approximately 1/2 of m.

Therefore, in the present invention, the Ul(
The F band and VHF band high channel are received by a small rod antenna that is less than half the length of the conventionally used rod antenna, and the VHF band low channel is matched to the rod antenna and the VHF band low channel. By using a tuned loop antenna in combination, a decrease in sensitivity is prevented, and it is possible to achieve both good image reception and miniaturization.

〔Example〕

Embodiments of the present invention will be described below in detail based on the drawings. FIG. 1 shows an embodiment of the present invention, and 10 is a rod antenna;
A loop antenna 12 is tuned and matched to the VHF band low channel.

14 is a television tuner, 16 is a balun for a balanced/unbalanced conversion circuit, and also includes a matching circuit for antenna impedance and the television tuner 14.

18 is a choke coil for UHF, 20 is a coil, and 22 is a capacitor. The coil 20 and capacitor 22 form a filter circuit 24 with a resonant circuit, so that the impedance becomes extremely large in the VHF band high channel of 170 to 222 MHz. Set element constants.

In the above configuration, the rod antenna 10 is excited in the UHF band receiving element. The signal received by the rod antenna 10 is input to the television tuner 14 without flowing to the loop antenna 12 due to the UHF choke coil 18 which is selected to have sufficient inductance in the UHF band.

Vl (When receiving the F band high channel, the rod antenna 10 is also excited. When receiving with the rod antenna 10, the loop antenna 1 is excited by the filter circuit 24.
The signal is input to the television tuner 14 without being passed to the TV tuner 14.

When receiving a VHF band low channel, the loop antenna 12 is excited and a signal is received. Further, the rod antenna 10 also receives signals, although the receiving sensitivity is inferior to that of the conventional length antenna.

That is, in this case, when viewed from the input terminal of the television tuner 14, the two antennas are connected in parallel and operate.

In particular, in a frequency band similar to the low channel of the VHF band, the magnetic field near the human body is large enough for practical use, and the effect of using the rod antenna 10 and the loop antenna 12 in parallel is remarkable.

FIG. 2 is an explanatory diagram showing the arrangement relationship when the antenna shown in the embodiment of FIG. 1 is attached to the casing of a liquid crystal television receiver. 60 is a liquid crystal television receiver, 62 is a housing,
64 is a liquid crystal panel, and 50 is an input/output terminal of the loop antenna 12, which is connected to the balun 16 in FIG.

The loop antenna 12 is attached to the inside or outside of the bottom surface of the housing 62. Television radio waves are horizontally polarized except in some areas. When receiving horizontally polarized radio waves, the direction of the magnetic field is vertical.

Therefore, in this arrangement, the rod antenna 1
Since antenna 0 can be oriented in a relatively free direction, it may be horizontal, and is excited by the horizontally polarized electric field component, and the loop antenna 12 is excited by the magnetic field component.

That is, according to the present invention, when receiving a VHFHF- channel, it is sensitive to both electric field and magnetic field components, and the influence of the human body can be reduced.

FIG. 3 shows another embodiment of the present invention, in which two loop antennas are connected in parallel.

44 is a loop antenna A, 54 is a loop antenna B
It is.

FIG. 4 is an explanatory diagram showing the arrangement relationship when the antenna shown in FIG. 3 is attached to the housing of a liquid crystal television receiver.

As shown in FIG. 4, the loop antenna A44 is attached to the housing 62.
A loop antenna B54 is on the bottom of the .

It is attached to the side surface of the housing 62 at right angles to the loop antenna A44. Two loop antennas 44, 54 are attached inside or outside the housing 62.

The structure shown in FIG. 4 is particularly advantageous when radio waves are multiple-reflected indoors, and as a result, the plane of polarization is disturbed and horizontal and vertical polarization components are present.

In other words, the configuration of the present invention is sensitive to both the electric field and magnetic field components of television radio waves, and is sensitive to both the electric field and magnetic field components of television radio waves, regardless of whether the received radio waves are vertically polarized or horizontally polarized, and regardless of the position or direction in which the liquid crystal television receiver is used. However, reception is possible and the sensitivity of the receiving device is significantly reduced (relatively close to omnidirectional).
Become.

Additionally, loop antennas can generally be manufactured using printed circuit boards, in which case they can be produced at low cost and easily, have less variation in characteristics, and can be mounted with other circuit elements at the same time.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, UHF band and VHF band high channels are received by a rod antenna, and a rod antenna and a loop antenna are used together for the VHF band low channel. As a result, even a short rod antenna can have high sensitivity to light.

Additionally, it is sensitive to both electric and magnetic field components, allowing reception regardless of the position or direction in which the LCD television receiver is used. In addition, the parts used can be small and inexpensive, and there is no problem with downsizing, improving performance, and lowering prices of liquid crystal television receivers, making it extremely advantageous in practice.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a circuit diagram showing one embodiment of the present invention.
FIG. 3 is a circuit diagram showing another embodiment of the present invention; FIG. 4 is a perspective view showing the arrangement of antennas in the embodiment shown in FIG. 3. It is. 10... Rod antenna, 12... Loop antenna, 24... Filter circuit. Figure 1

Claims (2)

[Claims] (1) A stretchable rod antenna that is excited by the electric field component of television broadcast radio waves, and at least one loop antenna that is excited by the magnetic field component, and a UHF antenna is provided between the loop antenna and the television tuner. A filter circuit is provided to block high channel signals in the UHF band and VHF band, and signals in the UHF band and VHF band high channel are received by the rod antenna, and signals in the VHF band low channel are received by the rod antenna and the loop antenna. An antenna device characterized by receiving signals. (2) Claim 1, characterized in that two or more loop antennas are provided, and at least two loop antennas are formed on the casing of the small portable television receiver at right angles to each other. The antenna device described.