JPH09307327A - Rod antenna and antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reception sensitivity regardless of its small size while sufficiently securing the mechanical strength by adopting the configuration for the antenna system such that series connection of a plurality of ferrite core rods is contained in a pipe and the rod antenna is formed by winding a coil on the pipe. SOLUTION: A stick antenna 1 is formed by inserting series connection of a plurality of (e.g. 3 to 5) ferrite core rods 2 into a plastic-made pipe 3. A coil 4 is wound on the pipe 3 to which the ferrite core rods 2 are inserted and the pipe 3 with the coil 4 wound thereon is inserted to a case 5. Since the ferrite core 2 is made by compacting metallic powder and sintering the powder at a high temperature, the core 2 is feeble and easily folded, the folding or the like is surely prevented by inserting the core 2 into the pipe 3. Furthermore, several number of the ferrite cores 2 are connected in series, then the magnetic field is received with high sensitivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a medium-wave rod antenna and an antenna device for improving the reception sensitivity of medium-wave broadcasting.

SUMMARY OF THE INVENTION The present invention utilizes the property that when a coil is wound around a ferrite core, it can take in a magnetic field ten times as much as that of an air core.
It is a device that supplies the voltage induced in the magnetic field of the rod-shaped antenna to the receiver by a coaxial cable or a signal supply coil, and increases the induced voltage by 3 to 4 times as compared with the built-in antenna of the receiver.

Further, in an area where the radio wave is relatively weak, a wide band continuously variable matching device is used in combination with the antenna,
Further, the output voltage of the antenna can be increased about 3 to 4 times.

In a building having a reinforced structure, the electric field strength in the room is attenuated to 1/3 to 1/30 as compared with the outdoors. By retracting and supplying the received radio waves to the receiver, the induced voltage can be further increased to 3 to 30 times that in the room.

Further, by connecting and using rod-shaped ferrite cores in series, a large magnetic field can be taken in, and the antenna is easy to install because it is smaller than conventional external antennas. Less susceptible to non-magnetic materials. Moreover, since the directional characteristics are maximum in the direction perpendicular to the axis of the antenna, it is suitable for use inside windows of condominiums or on balconies.

[0006]

2. Description of the Related Art As a medium-wave antenna, a ferrite core antenna, a loop antenna, a long wire antenna, a whip antenna, etc. have been conventionally known.

Ferrite core antennas have the advantage that they can be made compact, and are widely used as built-in antennas for receivers. On the other hand, the material is brittle and fragile, so the shape cannot be increased, and it is not suitable as an external antenna.

Although the loop antenna can secure a certain amount of gain, since the directional characteristic is a figure 8 shape, the loop direction has the maximum gain, and when the loop antenna is used near a window in a building, the loop antenna direction is It becomes a right angle to the wall,
Space is required for installation near the window where the electric field received is relatively high.

The long wire antenna is used as a high-sensitivity antenna because it can secure a certain amount of gain. However, since a long wire is stretched, it is necessary to secure a wide site, and it is not easy to install the antenna. Cheap.

Since the whip antenna is omnidirectional and can be installed in a small space, it is used in a car radio or the like, but its effective length is small.

[0011]

By the way, many receivers currently on the market do not have a medium-wave antenna input terminal, and such loop antennas, long-wire antennas, whip antennas, etc. described above as household antennas are used. The use of external antennas is extremely rare.

Most of the currently used medium wave receiving antennas, except those for automobiles, are ferrite core antennas built in the receiver. This antenna is used in an area where the electric field strength is above a certain level. As far as it goes, there is no problem in practical use.

However, as described above, the ferrite core antenna has a small effective antenna length. For this reason,
In a weak electric field area, noise increases due to insufficient receiver input voltage of the receiver, and in a building with a reinforced structure,
There is a problem that radio waves from the outside are blocked and attenuated by the building, and it is difficult to hear because of the influence of noise from devices such as indoor lighting fixtures.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a rod-shaped antenna and an antenna device capable of improving the receiving sensitivity while firmly maintaining the mechanical strength. .

[0015]

In order to achieve the above object, the invention of claim 1 is a pipe for accommodating a plurality of rod-shaped ferrite cores and a ferrite core row formed by connecting the ferrite cores in series. And a coil wound around this pipe.

According to the above construction, a large magnetic field can be taken in by constructing several ferrite cores connected in series, and the mechanical strength is maintained by inserting the ferrite core into the pipe.

According to a second aspect of the present invention, in the rod-shaped antenna according to the first aspect, the coil is dense in the central portion and is roughly wound at both end portions.

According to the above structure, the coil winding method is devised, the central portion is dense and both end portions are roughly wound, so that the antenna input voltage of the receiver in the weak electric field region can be increased, A good reception condition can be obtained even with weak radio waves.

A third aspect of the present invention is a rod-shaped antenna according to the first or second aspect, a coaxial cable connected to one end of the rod-shaped antenna, and a broadband continuously variable type connected to the other end of the coaxial cable. And a matching device of 1.

According to the above-mentioned structure, the impedance matching between the antenna and the load can be achieved over the whole range of the medium wave band by the wide band continuously variable type matching device, and an even better reception condition can be obtained even with a weak radio wave. Obtainable.

According to a fourth aspect of the present invention, in the antenna device according to the third aspect, the antenna device is used between the wideband continuously variable matching device and the receiver so as to be close to the antenna built in the receiver. It is characterized in that a signal supply coil is provided.

According to the above construction, the magnetic field taken in by the rod-shaped antenna can be supplied to the built-in antenna of the receiver by bringing the signal supply coil close to the built-in antenna of the receiver. It is possible to obtain an even better reception state.

As an example of the use of the rod-shaped antenna configured as described above, in a building having a reinforced structure, the property that is not easily affected by the surroundings is effectively used, and the antenna can be easily installed outdoors by the window. It is possible to improve the sensitivity of the receiver and to make it maintenance-free by supplying the radio wave of the receiver to the receiver in the building without using electric power.

[0024]

1 shows the structure of a rod-shaped antenna (hereinafter referred to as a stick antenna) according to the present invention, and FIG. 2 shows the structure of an antenna device using this stick antenna.

<Stick Antenna><< Principle of Stick Antenna >> First, the principle of the stick antenna will be described.

The ferrite core used in the stick antenna of the present invention has the property that "if the material is fixed, the larger the cross-sectional area of the core, and the longer the core, the greater the voltage induced in the antenna" (reference). Literature: Japan Broadcasting Corporation, "New Radio Technology Textbook, Application, p385"
Published on July 15, 1964).

FIG. 3 shows experimental results of relative gains when a plurality of ferrite cores are connected in series and when they are connected in parallel.

This time, the number of ferrite cores is only one, two in series connection, three in series connection, five in series connection, three in parallel connection, and five. Experiments were performed for the case of parallel connection. As a result, as can be understood from FIG. 3, when the ferrite cores were connected in series, it was found that the relative gain increased almost in proportion to the number of the ferrite cores. Also, in the case of parallel connection, it was found that the gain cannot be increased so much even if the number of ferrite cores is increased.

<< Design of Stick Antenna >> Next, a specific design of the stick antenna based on the above principle will be described.

In the stick antenna 1 shown in FIG. 1, a plurality of, for example, three to five ferrite cores 2 are connected in series and inserted into a pipe 3 (FIG. 1 (A)), and the ferrite cores 2 are inserted. The coil 4 is wound around the pipe (FIG. 2B), and the pipe 3 on which the coil 4 is wound is inserted into the case 5 (FIG. 2C).

Since the ferrite core 2 used for the stick antenna 1 is formed by compressing metal powder and firing it at a high temperature, the material is brittle and easily broken. Therefore, in this embodiment, 3 to 5 pieces (3 pieces in the figure) of the ferrite cores 2 having a length of 18 cm and a diameter of 1.2 cm are inserted into the pipe 3 such as Bakelite and the like, and then the coil 4 is wound around. It is stored in the case 5. The outer shape of the stick antenna 1 is about 2 cm in diameter and about 50 cm to 1 m in length, and is sealed with a vinyl pipe or a plastic pipe 3 and waterproofed.

As a result, the magnetic path of the ferrite core 2 becomes long, and the radio waves can be largely captured, so that good sensitivity can be obtained even in a weak radio wave state.
Further, since the ferrite core 2 is housed in the pipe 3 and the pipe 3 is housed in the case 5, breakage of the ferrite core can be reliably prevented.

Further, the winding pitch of the coil 4 is dense at the central portion and roughly wound at both end portions. Specifically, assuming that the winding interval between both ends of the ferrite core 2 is "2", the ferrite core 2 is wound so as to have "1" at the center. As a result, the output voltage in the entire medium wave band can be made larger than that at a constant interval.

The electrical characteristics of the stick antenna 1 configured as described above are shown below. When the five ferrite cores 2 are connected, the measured value is a frequency of 1 MHz, the impedance is 0.6Ω + j70Ω, and the antenna gain is −. It was 36 dB (relative to the electric field strength).

Also, the stick antenna 1 created this time
Table 1 shows the reception test result (terminal voltage) in the field of the conventional whip antenna. However, Table 1
Is an electric field strength of 612 kHz ... 111 dBμV, 1017
The measurement result at kHz ... 108 dBμV is shown.

[0036]

[Table 1]

As can be understood from Table 1, the electric field strength 6
12 kHz ... 111 dBμV, 1017 kHz ... 108
In any case of dB μV, the stick antenna of the present invention is 7 to 9 dB as compared with the conventional whip antenna.
It was confirmed that the sensitivity was improved by about μV.

<Antenna Device> Next, an antenna device using the stick antenna 1 will be described. As shown in FIG. 2, this antenna device includes the stick antenna 1 shown in FIG.
A coaxial cable 6 connected to the cable connection end 1A of
A signal supply coil 7 connected to the other end of the coaxial cable 6 is provided. This signal supply coil 7 is connected to the receiver 8
It is used in close proximity to the ferrite bar antenna 9 incorporated in the. A broadband continuously variable matching device 12 is inserted in the coaxial cable 6 as needed. In addition, 10 in the figure
Is a speaker of the receiver 8 and 11 is a tuner unit.

The signal supply coil 7 is formed by winding a coil having a diameter of 0.5 mm around a ferrite core having a diameter of 0.6 cm and a length of 6 cm about eight times.

When this coil 7 is brought close to the ferrite bar antenna 9 built in the receiver 8, most of the antenna output voltage can be supplied to the receiver 8 by electromagnetic induction.

FIG. 4 shows the configuration of the broadband continuously variable matching box 12. A primary winding 14, a secondary winding 15, and a tertiary winding 16 are wound around the toroidal core 13 of the matching unit 12, and a variable capacitor 17 is provided between the tertiary windings 16. A parallel resonance circuit is formed by being inserted.

As shown in FIG. 1, the coaxial cable 6 is connected to the cable connecting end 1A of the stick antenna 1, the coaxial cable 6 is connected to the primary winding 14 of the matching unit 12, and the matching unit 12 When the secondary winding 15 is connected to the signal supply cable 7 through the coaxial cable 6, the parallel resonance circuit including the tertiary winding 16 and the variable capacitor 17 causes the signal from which j has been removed from the secondary winding 15 to be removed. You can take it out.

At this time, the output impedance Z ₂ is

[Formula 1] Z ₂ ∝ Q ² · Z ₁ (Ω) where Z ₁ is the input impedance and Q is the load of the parallel resonant circuit. Therefore, the primary winding 14 and the secondary winding 1
The desired impedance can be obtained by arbitrarily selecting the number of turns of each coil of the fifth winding and the tertiary winding 16.

The resonance frequency can be set so as to cover the entire medium wave band by changing the capacity of the variable capacitor 17 according to the number of turns of the tertiary winding 16.

<< Design of Wide-Band Continuously Variable Matching Device 12 >> The impedance of the stick antenna 1 alone is 0.6Ω +
Since j is 70Ω (1 MHz), j is removed in order to effectively supply the power induced in the antenna to the receiver. Set the output impedance to about 75Ω. The medium wave band (531 to 1602 kHz) can be continuously matched. It can be used at the receiver installation location (indoor). It is small and lightweight. It was designed with that in mind.

In the broadband continuously variable matching device 12, the primary winding 14 is connected to the toroidal core 13 having a relative dielectric constant of about 125.
The secondary winding 15 is wound 4 times, the tertiary winding 16 is wound 70 times, and the variable capacitor 17 is connected to the tertiary winding 16. By changing the variable capacitor 17, the impedance of the antenna and the impedance of the load are matched over the entire medium wave band,
It can be increased about 3 to 4 times as compared with the case where there is no input signal voltage.

FIG. 5 compares the gain of the stick antenna (antenna length 90 cm) of the present invention between the case of direct without the wideband continuously variable matching device 12 and the case of using the wideband continuously variable matching device 12. It has been shown. It was confirmed that when the wideband continuously variable matching device 12 is used, the gain of 10 dB is improved as compared with the case of using the direct type.

As described above, according to the antenna device of this embodiment, the circuit configuration is simple, and therefore the manufacture can be facilitated. Further, since no amplifier or the like is used, the battery can be eliminated and the manufacturing cost can be reduced. Further, since it is lightweight and small, it can be easily installed in a house having a reinforced structure such as a condominium, and can be used outdoors for portable use or for car radios.
Further, since the sensitivity of the receiver can be improved without using electric power, it can be maintenance-free.

Further, according to this embodiment, the following interference preventing effect is exhibited.

That is, since the stick antenna 1 has a directional characteristic of a figure 8, it is possible to reduce interference by changing the direction of the stick antenna and dropping interference waves, noise radio waves, etc. in the radio wave insensitive direction.

Further, when the wideband continuously variable matching device 12 is also used, since the selectivity characteristic of the resonance circuit is added, the interference due to the interfering wave of the adjacent frequency can be further reduced.

[0052]

As described above, according to the first aspect of the present invention, it is possible to greatly improve the receiving sensitivity while sufficiently securing the mechanical strength while being small in size.

According to the second aspect of the invention, since the winding method of the coil is devised, the antenna input voltage of the receiver in the weak electric field area can be increased, and good reception is possible even with weak radio waves. You can get the status.

According to the third aspect of the present invention, the broadband continuously variable type matching device can perform impedance matching between the antenna and the load over the entire medium-wave band, and is even better for weak radio waves. The reception status can be obtained.

According to the invention of claim 4, since the magnetic field taken in by the rod-shaped antenna can be supplied to the built-in antenna of the receiver by bringing the signal supply coil close to the antenna of the built-in receiver, a weak radio wave can be supplied. Even in this case, a better reception state can be obtained.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a rod-shaped antenna (stick antenna) according to the present invention.

FIG. 2 is a structural explanatory view of an antenna device using a rod-shaped antenna (stick antenna) according to the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a relative gain and the number of ferrite cores in a rod-shaped antenna (stick antenna) according to the present invention.

FIG. 4 is a diagram illustrating the configuration of a wideband continuously variable matching device.

FIG. 5 is an explanatory diagram showing characteristics of a rod-shaped antenna (stick antenna) according to the present invention in comparison between a case where a wideband continuously variable matching device is used and a case where it is not used.

[Explanation of symbols]

 1 Stick antenna (bar-shaped antenna) 2 Ferrite core 3 Pipe 4 Coil 5 Case 6 Coaxial cable 7 Signal supply coil 8 Receiver 9 Ferrite bar antenna 12 Wideband continuous variable type matching box

Claims (4)

[Claims] 1. A rod-shaped ferrite core, a pipe accommodating a ferrite core row formed by connecting the ferrite cores in series, and a coil wound around the pipe. Stick antenna. 2. The rod-shaped antenna according to claim 1, wherein the coil has a dense central portion and coarsely wound end portions. 3. The rod-shaped antenna according to claim 1 or 2, a coaxial cable connected to one end of the rod-shaped antenna, and a broadband continuously variable matching device connected to the other end of the coaxial cable. An antenna device comprising: 4. The antenna device according to claim 3, wherein a signal supply coil used near the antenna incorporated in the receiver is provided between the wideband continuously variable matching device and the receiver. An antenna device characterized by being provided.