JPS59162B2 - aerial - Google Patents

Description

[Detailed Description of the Invention] When receiving television broadcasts, ghost interference may occur due to the influence of buildings, etc. When performing wireless communication, radio waves may be transmitted and received in unnecessary directions, causing radio wave interference. However, in order to prevent such problems, the present invention transmits and receives only radio waves in the desired direction (hereinafter referred to as desired waves), and transmits and receives radio waves in unnecessary directions (hereinafter referred to as unnecessary waves). The purpose of this is to suppress the transmission and reception of

Although the antenna of the present invention can be used for both transmission and reception based on the reversibility theorem, for convenience of explanation, the reception antenna will be described below.

Also, the shape of the reflector and radiator can be various, such as linear or planar, but in the following description, a linear one will be described with the main object being TV broadcast reception.

The present invention consists of two inventions, the first invention is a general invention including the second invention, and the second invention is a multi-channel (hereinafter referred to as ch) invention. It includes provisions that are limited and necessary because it is an antenna.

FIG. 1 shows an antenna according to an embodiment of the first invention with a frequency of 1c.
FIG. 2 is a diagram illustrating the operating principle of the second invention.

FIG. 1 shows that when the number of channels is large, the radiator is common and it is sufficient to arrange twice as many reflectors as the number of channels.

In Fig. 1, 1 is a radiator, 2 and 3 are reflectors, and 1.2.
3 are linear and arranged parallel to each other.

The reflectors 2 and 3 are arranged on a plane α perpendicular to the direction of propagation of radio waves, and the vertical distances A' and A between the center point A' of the radiator 1 and the plane α are r.

The reflectors 2 and 3 have the same length, thickness, and shape, and the length is t.

The reflectors 2 and 3 are placed at positions opposite to the radiator 1, with the center point of the reflectors 2 and 3 being located opposite to the radiator 1.

Let C be the intersection of the line connecting E and the line AC passing through point A on the α plane parallel to 1.

In this case, the distance between DE is S, and the reflectors 2 and 3 are arranged so as to be DC2CE.

Let h be the distance between CAs.

(hereinafter referred to as bias). F represents the direction of the desired wave, and B represents the direction of the unwanted wave. 3 If the arrangement is as shown in Figure 1, the relationship between the geometrical positions of the radiator 1 and the reflector 2 and the relationship between the radiator 1 and the reflector 3 will be Since the relationship of geometrical positions is equal, radiator 1
The mutual impedance z12 of reflector 2 and the mutual impedance ZtS of radiator 1 and reflector 3 are equal,
This value can be calculated by fixing the length and shape of the radiator and reflector.
Determined by r, h, and s.

The input impedance Z22 of the reflector 2 and the input impedance Z33 of the reflector 30 are determined by the length, shape, and thickness of the reflector, and by using reflectors with the same length, shape, and thickness, z2□2 It can be Za3.

The reflector is generally installed on the side opposite to the direction of arrival of the desired wave, so in Figure 1, F is the direction of arrival of the desired wave, and unnecessary waves are unnecessary because generally those coming from the direction opposite to the desired wave have the most influence. Let the direction of the wave be the opposite direction to F and the direction of B.

In this case, the following relational expression (1) holds true for radio waves from the F direction, and the relational expression (2) holds true for radio waves from the B direction.

In equations (1) and (2), 11, I, , I3 are radiators 1
, the current flowing through the center points of reflectors 2 and 3 is m=2
π/λ, where λ is the wavelength and the voltage at the radiator due to the received electric field is E.

shall be. Also, Zll represents the sum of the radiator 10 input impedance and the load impedance.

In equations (1) and (2), reflectors 2 and 3 are arranged at symmetrical positions with respect to radiator 1, and the length of reflector 2 and 3 is
Due to the same thickness and shape, z2□−233,z1
Since the relationships □-zta and 12-I3 hold, by rearranging equations (1) and (2), - equations (5) and (6) correspond to equations (1) and (2). Therefore, the current flowing through the radiator 1 due to the unnecessary radio waves from the B direction can be reduced to 0 by setting the term [ ] in the numerator of equation (6) to O.

That is, (z 2□+223)-2z12ejmr=0・
...(7) z2□, z23. so that equation (7) holds true. z12. r
By determining , the current flowing through the radiator 1 due to the unnecessary radio waves from direction B can be set to O.

If the ratio of the current flowing through the radiator 1 of the desired wave to the unwanted wave of the antenna according to the present invention is the F/B ratio, the value of this F/B ratio is obtained from equations (5) and (6), and (8) The term in the denominator of the equation corresponds to the left term in equation (7), so if (7) is made to hold, theoretically the F/B ratio will be infinite, and the F/B ratio will be sufficiently large.
It is possible to provide an antenna with a good IB ratio.

z2□, z23, which are related to the conditions for formula (7) to hold. z1
2°r will be explained next.

Regarding Z2□, as described above, the input impedance of the reflector is determined by the length, shape, and thickness of the reflector.

Z23 is the mutual impedance of reflector 2 and reflector 3,
In the structure shown in FIG. 1, it is determined by the distance S between them.

Regarding Z12, as described above, the mutual impedance between the radiator 1 and the reflector 2 is determined by r, h, and s in the structure of FIG. 1.

As is clear from FIG. 1, r is determined by the perpendicular distance between the α plane and the radiator 1.

As mentioned above, Z22. z23. z12. After all, r is the length shape of the reflector, the thickness and the vertical distance r between the radiator and the plane α on which each two reflectors are placed, which are the components of the thickness and the geometrical position of the radiator and the reflector, and the deviation h , is determined by the distance S between the reflectors.

In fact, z2□t z23 t z12 that satisfies equation (7)
. If the thickness, length, and shape are set so that z33 has an imaginary part of 0,
r=0.25λ, s=0.667λ, h=0.352λ
, the F/B ratio of equation (8) is 34.9 db, which is sufficient for the necessary value as a countermeasure for TV ghost (required value 25 db
(above) become something you are satisfied with.

This has also been confirmed experimentally, indicating that it is possible to determine Z22 t Z23 F z1□ for which equation (7) holds true.

To summarize the content of the present invention (first invention) detailed above,
The present invention consists of a radiator and two reflectors for each frequency band, z12-213. Satisfies the condition z2□=z33, and (Z22+223)-2ejmr, z
This is an antenna characterized by adjusting the shape and size of the reflector and the geometrical position between the radiator and the reflector so as to satisfy 1□K0.

As a result, it is possible to eliminate TV ghost interference and eliminate the transmission and reception of radio waves in unnecessary directions during wireless communication, and the effect is estimated to be extremely large.

Next, the second invention will be explained in detail.

When performing wireless communication such as television reception, it is required to provide an antenna that can be shared by multiple channels and has a high F/B ratio for any channel used.

The second invention is aimed at achieving the above object.

Since conventional reflectors have a length of λ/2 or more,
The input impedance of the reflector has a positive imaginary part (X) in addition to a real part (R).

Figure 2 shows the imaginary part (X) of the input impedance of the reflector.
It shows the characteristics with respect to the length.

The horizontal axis shows the value of the length t of the reflector, and the vertical axis shows the value of X.

The operating difference of the conventional reflector is on the right side of point H, and the value of t is set to λ/2 or more, so the value of X is set to +42.5Ω or more.

In the present invention, since the operating point of the reflector is set to point G, the value of t is λ/2 - △ (△...the length of t is many times shorter than λ/2), and That is, the imaginary part of the input impedance is set to O.

Since a multi-channel antenna is especially necessary for receiving TV broadcasts, we will consider the VHF band for receiving TV broadcasts.

When receiving television broadcasts, the channel required for listening is determined for each region, so all you need to do is consider that channel.

Chl, ah3, ah5 in the VHF band of the area
.

When channel 12 is being broadcast, the antenna according to the present invention has a radiator 1 shared by each channel and 2 reflectors for each AH.In the VHF band in this area, 2 x 4-8 reflectors are invented ( 1st
invention) satisfies the conditions and sets the imaginary part of the input impedance of the reflector to 0 near the carrier frequency of one frequency band.
The configuration is adjusted and arranged to become the following.

Next, the operation of the present invention in the case of such a configuration will be explained.

When performing wireless communication such as television broadcasting, a modulated wave is transmitted centered on a carrier wave, but the frequency band that is transmitted contains many frequency bands around the carrier wave, and the further away from that frequency band, the less energy components are contained. I'm coming.

For example, in VHF television broadcasting, the frequency band of ch 3 is 10
2 to 108 MHz, but the frequency that has the most influence on TV ghost disturbance is the carrier frequency of AH 3, which contains many frequencies around 103.25 MHz, which is the video frequency, so at frequencies around this Especially F/
If the antenna has a large B ratio, it is expected that the effect will be thicker.

If the imaginary part of the input impedance of the reflector is set to 0 in the vicinity of the carrier frequency as described above, as is clear from Fig. 2, the value of the input impedance of the reflector will be the lowest in the vicinity of the carrier frequency, and the frequency of that channel will decrease. For example, in the band 102 to 108 MHz of AH3, the value of X is not 0 in all frequency bands, but it is a relatively low value, and F
/B ratio can also be set to a certain value or more.

Since such a reflector has some influence on other channels, this will be discussed next.

For example, in VHF television broadcasting, the frequency band of ah 1 is 90M.
The frequency band of H2~96MH31ah5 is 176MH2~
The frequency band of 182MH21chi2 is 216MH2~2
22MH2, so if we consider the influence of the reflector on ch 3, △ in Fig. 2 is about a few percent, and ah 3, chi, ah 5. Since there is a difference of more than a factor of 10 from the frequency of c'h12, a reflector that sets X to O at the video frequency of ch 3 will have a considerably large value at other frequencies, (5).

Since 22□ in equation (6) is a fairly large value, (5)
, The current ■1 of the radiator 1 in equation (6) is as follows (9), which means that the reflector has no total heat in this frequency band, and has no effect.

Ch 1 and ch 3 have some influence, but r, h.

By adjusting S, it is possible to increase the F/B ratio even for channels with and.

To summarize the contents of the present invention (second invention) detailed above, in the antenna of the invention (first invention), the imaginary part of the input impedance of the reflector is set to 0 near the carrier frequency band of one frequency band. Each ah
This antenna is characterized by being placed at each location.

This makes it possible to provide antennas with a high F/B ratio for all channels of multiple AH, and is expected to be extremely effective in wireless communication.

[Brief explanation of the drawing]

FIG. 1 is a configuration example of an antenna according to an embodiment of the first invention, and FIG. 2 is a diagram illustrating the operating principle of the second invention. 1...Radiator, 2, 3...Reflector arranged on the plane α perpendicular to the direction of propagation of radio waves, F...
Direction of desired wave, B...Direction of unwanted wave, A'...
...Center point of radiator, D, E...Reflector 2
, 3 center point, C...... line connecting DE and radiator 1
The intersection with the line passing through point A on the α plane parallel to , S...
・Distance between DE, h・・・Distance between CA (bias)
, r...Distance between A and A', t...
・Reflector length, X...Imaginary part of reflector input impedance.

Claims (1)

[Claims] 1. Consists of a radiator and two reflectors for each frequency band, and the mutual impedance between the reflectors is set to 223.
, the mutual impedance between the reflector and radiator is 21□
, z13, reflector input impedance z2□, z3
3. Let r be the vertical distance between the surface where each two reflectors are placed and the reflector, and adjust the shape and dimensions of the reflector and the distance between the reflector and the radiator so that Z1□=213, Z2□2Z33. adjust the geometric position of and (z22+223)−2ej
mr, Z12f:Ol (m=2π/λ, λ...wavelength)
An antenna characterized in that it is realized by adjusting the shape and dimensions of the reflector, the radiator and the reflector, and the geometric positions between the reflectors so as to satisfy the following. 2 Consists of a radiator and two reflectors for each frequency band, and the mutual impedance between the reflectors is Z23
, the mutual impedance between the reflector and radiator is 21□
, Z13, the input impedance of the reflector is 22□, Z3
3. Let the vertical distance between the reflector and the surface on which each two reflectors are placed be r, and Z122z13 t z22"z3
Adjust the shape and dimensions of the reflector and the geometrical position between the reflector and the radiator so that
eJmr, Z12:Ol (m-2π/λ, λ...wavelength) is established by adjusting the shape and dimensions of the reflector, the radiator, the reflector, and the geometric positions between the reflectors. A multi-channel antenna characterized by arranging two reflectors for each frequency band in which the imaginary part of the input impedance of the reflector is adjusted to be 0 near the carrier frequency of one frequency band. .