JPH0777325B2 - Dual frequency resonant printed dipole antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention aims to cause a printed dipole antenna with a reflector for a base station for land mobile communication to resonate at two frequencies so as to match the directivities in the horizontal plane in two frequency bands. The present invention relates to a two-frequency resonant printed dipole antenna in which a parasitic element is attached to the front surface of the printed dipole antenna to improve the impedance deterioration caused by matching the directivities.

[Conventional technology]

As a conventional method of resonating at two frequencies using a printed dipole antenna, there is one realized by the configuration shown in FIG.

In the figure, 1 is a radiating element of a printed dipole antenna, 2 is a parasitic element, 3 is a dielectric substrate, and 4 is a reflecting plate. The distance between the center of the radiating element of the printed dipole antenna and the reflecting plate is d0, The distance between the parasitic element and the center and the reflector is d1, the radiating element length of the printed dipole antenna is l0, and the parasitic element length is 1.

The length l0 of the radiating element 1 of the printed dipole antenna is
It is about 1/2 of the wavelength λL corresponding to the first resonance frequency.
That is, l0≈0.5λL.

The parasitic element 2 is arranged so as to overlap the radiating element 1 above the radiating element of the printed dipole antenna. Therefore, if the distance d0 from the reflector of the radiating element 1 is determined, the distance d1 from the reflector of the parasitic element 2 is also almost determined.
The element length 1 of the parasitic element 2 is about 1/2 of the wavelength λH corresponding to the second resonance frequency. That is, 1≈0.5λH. The distance k between 1 and 2 is about 4% of λL, that is,
k≈0.04λL.

FIG. 2 shows an example of measurement of return loss with respect to frequency when the distance between the reflector 4 and the radiating element 1 of the printed dipole antenna is changed. (A) is d0 = 0.15λL, (b) is d0
= 0.18λL, (c) is d0 = 0.27λL.

When the distance dt between the radiating element and the reflecting plate becomes small, the return loss becomes small and the impedance deteriorates. At this time, although the specific band at the time of resonance becomes narrow at the second resonance frequency, the deterioration of impedance is small.

[Problems to be solved by the invention]

FIG. 3 is a calculation example of the directivity in the horizontal plane at the best spacing d0 = 0.27λL in the resonance state of the conventional printed dipole antenna at the first resonance frequency, where (a) is the first resonance frequency, and (b) is ) Is at the second resonance frequency. If the second resonance frequency is 1.67 times the first resonance frequency, d1 = 0.45λH.

As described above, since d0 and d1 are set so that the radiating element 1 and the parasitic element 2 overlap with each other, the length of d1 is almost determined by determining d0. It means that As described above, the conventional printed dipole antenna has a drawback that the directivity does not match because the distance between the reflector and the radiating element is different.

[Means for solving problems]

According to the invention, the above mentioned objects are achieved by means of the patent claims.

That is, the present invention is most characterized in that the reflector and the radiating element distance between the printed dipole antenna are made close to each other in order to match the directivity, and the impedance characteristic deterioration at the first resonance frequency caused thereby is improved. However, it differs from the conventional one in that a parasitic element made of a metal conductor is attached to the front surface of the printed dipole antenna.

〔Example〕

FIG. 4 is a diagram showing an example of the configuration of a two-frequency resonant printed dipole antenna of one embodiment of the present invention, in which 1 is a radiating element of the printed dipole antenna, 2 is a parasitic element,
3 is a dielectric substrate, 4 is a reflector, and 5 is a parasitic element having a length and width different from those of the parasitic element 2.

The length relationship between the radiating element 1, the parasitic element 2 and the parasitic element 5 of the print dipole antenna is set to l0>l2> 1. That is, l2 is in the range l0 to 1.

Fig. 5 shows d0 = 0.15λL, d1 = 0.2λH, 1 = 0.34λ
L is a measurement example of the return loss with respect to frequency when the width ω of the parasitic element is changed, and (a) is ω = 0.15λL,
(B) is ω = 0.09λL, (c) is ω = 0.03λL, (d)
Is the characteristic when ω = 0.01λL, and (e) is the characteristic when ω = 0.009λL.

The distance between the radiating element 1 and the parasitic element 5 of the print dipole antenna is constant at 0.06λL.

The impedance characteristic at the first resonance frequency is improved by reducing the width of the parasitic element 5, and ω = 0.1λ
If it is larger than L, the deterioration is large.

At the second resonance frequency, the parasitic element length 1 of 2 and the mounting interval k with the printed dipole antenna are optimally designed, and are constant even if the parasitic element width ω of 5 is changed.

That is, it can be seen that the parasitic element of 5 is not related to the second resonance frequency.

FIG. 6 shows an example of calculation of directivity in the horizontal plane.
(A) is for d0 = 0.15λL, and (b) is for d1 = 0.20λH.

〔The invention's effect〕

As described above, according to the dual-frequency resonant printed dipole antenna of the present invention, the horizontal plane directivities at the respective frequencies can be substantially matched, and the impedance characteristics can be easily improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a structure of a conventional two-frequency resonant printed dipole antenna, FIG. 2 is a diagram showing an example of measurement of impedance characteristics of a conventional two-frequency resonant printed dipole antenna, and FIG. 3 is a conventional two-frequency resonant printed dipole antenna. FIG. 4 is a diagram showing a horizontal plane directivity calculation example of a resonant printed dipole antenna, FIG. 4 is a diagram showing an example of a configuration of a dual frequency resonant printed dipole antenna of one embodiment of the present invention, and FIG. 5 is a dual frequency resonant of the present invention. The figure which shows the measurement example of the impedance characteristic with respect to the parasitic element width of a printed dipole antenna, and FIG.
It is a figure which shows the example of calculation of the directivity in a horizontal plane of a frequency resonance printed dipole antenna. 1 ... Radiating element of printed dipole antenna, 2 ...
Parasitic element, 3 ... Dielectric substrate, 4 ... Reflector, 5 ...
Parasitic element

Claims (1)

[Claims] 1. A parasitic element composed of a printed dipole antenna having a first frequency resonating formed on a dielectric substrate and a metal conductor having a second frequency resonating with a radiating element of the printed dipole antenna facing each other so as to be sandwiched therebetween. A two-frequency resonant printed dipole antenna in which an element is attached to the front surface of a reflector, and in front of the radiating element of the printed dipole antenna, the length is 1/2 wavelength or less of the first resonant frequency and the width is 1/10 wavelength or less. A two-frequency resonant printed dipole antenna, characterized in that a parasitic element made of the metal conductor is attached.