JP2816455B2 - Circularly polarized microstrip antenna and its frequency adjustment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circularly polarized microstrip antenna in which a ground conductor is formed on one surface of a dielectric substrate and a radiation conductor is formed on the other surface, and a method of adjusting the frequency thereof. is there.

[0002]

2. Description of the Related Art FIG. 7 is a plan view of a conventional circularly polarized microstrip antenna. The conventional circularly polarized microstrip antenna 7 shown in FIG. 1 has a ground conductor (not shown in the drawing) formed on one entire surface of a circular dielectric substrate 4 and radiates at the center of the other surface. A conductor 8 is formed, and power is supplied from a ground conductor surface side to a feed point P of a radiation conductor 8 provided eccentrically in a radial direction from a center O by a coaxial cable (not shown).

The radiation conductor 8 has a circular shape and is inclined by ± 45 ° with respect to a straight line M connecting the center O and the feeding point P 2.
Rectangular protrusions 8a to 8d for radiating circularly polarized radio waves are formed at four outer peripheral edge portions intersecting the straight lines m and n, respectively.

Conventionally, when the lengths of the projections 8a to 8d are shortened, the axial ratio, which is the ratio between the major axis and the minor axis of the circularly polarized wave, changes, and the resonance frequency at which the axial ratio becomes minimum changes upward. It is known that the axial ratio adjustment and the resonance frequency adjustment of the circularly polarized microstrip antenna 7 are performed using this characteristic.

That is, the resonance frequency of the circularly polarized microstrip antenna 7 is generally determined by the diameter R of the radiation conductor 7, the relative permittivity ε of the dielectric substrate 4, and its thickness t. Is appropriately set to set the initial frequency (resonance frequency without adjustment) of the circularly polarized microstrip antenna 7 lower than the target frequency, and the four projections 8a to 8d are set to the same amount. The axis ratio is adjusted to the minimum by shortening the length Lt, and the resonance frequency at which the axis ratio is minimized is gradually increased to the target frequency.

[0006]

The above-mentioned conventional circularly polarized microstrip antenna 7 has a projection 8a for generating circularly polarized waves.
It is possible to adjust the resonance frequency to the target value by gradually increasing the resonance frequency by cutting ~ 8d, but since there is no adjustment unit for lowering the resonance frequency, the resonance frequency is gradually lowered. It is difficult to adjust the frequency. For this reason, the protrusions 8a to 8d
When the resonance frequency to be adjusted exceeds the target frequency, the frequency adjustment becomes poor and the yield in the manufacturing process is reduced.

Further, since the axial ratio and the resonance frequency of the circularly polarized wave are simultaneously adjusted by cutting the projections 8a to 8d, it is also difficult to adjust both of them in a well-balanced manner.

The present invention has been made in view of the above problems, and has a circularly polarized microstrip antenna capable of adjusting the resonance frequency in both the upper and lower directions without affecting other characteristics such as an axial ratio. It is an object to provide a frequency adjustment method.

[0009]

According to a first aspect of the present invention, a ground conductor is formed on one surface of a dielectric substrate, and a radiation conductor is formed on the other surface. A circularly polarized microstrip antenna that is fed to a feed point provided eccentrically to a radiation conductor, wherein the radiation conductor is an outer peripheral edge portion of the microstrip antenna, the direction connecting the radiation conductor center and the feed point. 45 × (2N + 1) as reference
A projection or a notch for adjusting the axial ratio is formed at a position of ° (N is an integer), and a protrusion or a notch for adjusting the resonance frequency in a rising direction at a position of 90 N ° (N is an integer).
Or 2 are more collision-outs formed, and a notch for adjusting the resonance frequency decreases direction projecting in the vicinity of the base end portion of the raised formation
A conductor lacking portion formed of one or two or more small holes is formed as a guide .

According to a second aspect of the present invention, an outer peripheral edge of the radiation conductor is formed by cutting a frequency adjustment protrusion formed on the radiation conductor or by using a frequency adjustment conductor cutout as a guide. The frequency of the circularly polarized microstrip antenna is adjusted by forming a slit-shaped notch in the antenna.

[0011]

According to the present invention, 0 °, 90 °, 180 ° at the outer peripheral edge of the radiation conductor of the circularly polarized microstrip antenna .
°, the position of 270 ° to form a notch for adjusting the projection and the resonance frequency for adjusting the resonance frequency guide
And a conductor missing portion formed of a small hole is formed in advance.

The above-mentioned projections are adjusting portions for adjusting the resonance frequency in the ascending direction. The projections formed at the outer peripheral edges of the four radiation conductors are cut by the same amount, and the length of each projection is reduced. By reducing the length, the resonance frequency of the circularly polarized microstrip antenna can be increased.

[0013] The conductor lack portion consisting of the small holes is an adjustment portion for adjusting the resonance frequency in the low down,
The radiation conductor is cut in the outer peripheral direction by using the small hole of the conductor lacking portion as a guide , and the same number of slit-shaped notches are formed at the outer peripheral end portions of the four radiation conductors, so that the resonance frequency of the circularly polarized microstrip antenna Can be reduced.

Therefore, in the circularly polarized microstrip antenna, the resonance frequency is reduced by cutting each protrusion formed on the outer peripheral edge of the four radiation conductors by the same amount and shortening the length of each protrusion. gradually increased, or the adjustment of the target value of the resonance frequency gradually lowers the resonant frequency by forming the four on the outer peripheral edge of the radiating conductor suitable number of slit-shaped cutouts respectively performed .

[0015]

FIG. 1 is a plan view showing an embodiment of a circularly polarized microstrip antenna according to the present invention. FIG. 2 is a sectional view taken along line AA of FIG.

The circularly polarized microstrip antenna 1
A circular radiation conductor 2 having a diameter R sufficiently shorter than the diameter D of the dielectric substrate 4 is formed at the center of the upper surface of the circular dielectric substrate 4 having the ground conductor 3 formed on the entire lower surface. The power is supplied from the ground conductor 3 side to a feed point P provided eccentrically in the radial direction from the center O of the radiation conductor 2 by the coaxial cable 5. The outer conductor 5a of the coaxial cable 5 is connected to the ground conductor 3, and the inner conductor 5b penetrates through the dielectric substrate 4 and is connected to the radiation conductor 2 on the upper surface.

In addition, a 45 × (2N + 1) ° (N is an integer) direction at the outer peripheral edge of the radiation conductor 2 with respect to a radial direction passing from the center O of the radiation conductor 2 to the feeding point P,
That is, rectangular protrusions 23a to 23d having a width Wt and a length Lt are formed at positions in the directions of 45 °, 135 °, 225 °, and 315 °, respectively. The protrusions 21a,
The length Lt of 21c is longer than the protrusions 23b and 23d.

The projections 23a to 23d are mode degenerate separation elements for radiating circularly polarized radio waves. The projections 23a to 23d have projections at at least one of four locations on the outer peripheral edge of the radiation conductor 2. If it is formed, circular polarization can be generated.

The lengths Lt of the projections 23a to 23d can be changed to change the axial ratio, which is the ratio of the major axis to the minor axis of the circularly polarized wave.
The resonance frequency at which the axial ratio is minimized can be changed. When the length Lt of the protrusions 23a to 23d is reduced, the resonance frequency at which the axial ratio is minimized increases, and when the length Lt is increased, the resonance frequency decreases.

Accordingly, as described later, the protrusions 23a to 23a
By adjusting the length Lt of 23d, the axial ratio, which is the ratio of the major axis to the minor axis of the circularly polarized wave, is adjusted.

Further, the outer peripheral edge of the radiation conductor 2 is located at a position in the direction of 90N ° (N is an integer), that is, 0 °, 90 °, 180 °, and 270 ° with respect to the radial direction. Are projections 21a-21 for frequency adjustment, respectively.
d are formed five by five. In addition, near the base ends of the protrusions 21a to 21d on the outer peripheral portion of the radiation conductor 2, four conductor missing portions 22a to 22d for frequency adjustment are respectively formed.

The projections 21a to 21d need only be formed at least one by one, and may be formed in five or more projections. In addition, at least one of the conductor missing portions 22a to 22d only needs to be formed, and four or more conductor missing portions may be formed.

FIG. 3 is an enlarged view of a projection 21a for adjusting the frequency, a conductor missing portion 22a, and a projection 23a for adjusting the axial ratio formed on the outer peripheral edge of the radiation conductor 2. As shown in FIG.

Each of the five projections 21a has an appropriate width W and an appropriate length L, and protrudes radially from the outer periphery of the radiating conductor 2 at appropriate intervals. Also, each of the four conductor missing portions 2
2a is a circular hole having an appropriate diameter d.
1a on the line connecting the center O with the gap between
Is provided inward from the outer peripheral edge by a distance S set in advance.

Before the radiating conductor 2 is formed on the dielectric substrate 4, the four conductor missing portions 22 a are
Or, after the radiation conductor 2 is formed, on the dielectric substrate 4.

Note that the conductor missing portions 22a to 22d are
Since it is a guide for forming the notch 24 as described later, the guide may be not only a circle but also an ellipse, a rectangle, or any other shape.

The projections 21a to 21d are for adjusting the frequency upward, and are cut as the projections 21a to 21d are cut (see the dotted line portion of the projection 21a in FIG. 3) and the length L is shortened. To shorten the circumference of the radiation conductor 2
The circularly polarized microstrip antenna 1
Can be increased. In particular, when the projections 21a to 21d at the outer peripheral edge of the four radiation conductors 2 are cut by the same amount, the characteristics of the circularly polarized microstrip antenna 1, such as the input impedance and the axial ratio of the circularly polarized wave, are affected. The resonance frequency fo can be gradually increased without the need.

Further, the conductor missing portions 22a to 22d are
The frequency is adjusted downward. As shown in FIG. 3, the radiation conductor 2
Is cut to form a slit-shaped notch 24 at the outer peripheral edge of the radiation conductor 2 , thereby increasing the perimeter of the radiation conductor 2.
And the resonance frequency fo can be reduced according to the number of the notches 24. In particular, by forming the same number of notches 24 at the outer peripheral edges of the four radiation conductors 2 without affecting the characteristics of the circularly polarized microstrip antenna 1, for example, the input impedance, the axial ratio of the circularly polarized waves, and the like. The resonance frequency fo can be gradually reduced.

FIG. 4 is a diagram showing an example of an experimental result of a change amount (increase amount) of the resonance frequency with respect to a cutting amount of the projection 21a. FIG. 5 is a diagram illustrating an example of an experimental result of a change amount (decrease amount) of the frequency with respect to the length S of the notch 24.

The amount of cutting of the projections shown in FIG. 4 is determined by the projections 21 a to 21 a formed on the outer peripheral edge of the four radiation conductors 2.
The cutting amount 1d is shown, and the notch length S shown in FIG. 5 indicates the length of the notch 24 when one notch 24 is formed at each of four outer peripheral edge portions.

The circularly polarized microstrip antenna 1 used in the experiment has a resonance frequency fo = 1.575 GHz.
z, the dimensions of each part are as follows: Dielectric substrate 4; relative permittivity ε = 21.4, diameter D = 37 m
m, thickness t = 6 mm radiation conductor 2; circular radiation conductor of diameter R = 20.6 mm projections 21a to 21d for frequency adjustment; width W = 0.4 mm,
Length L = 1 mm Conductor cutouts 22a to 22d; circular with diameter d = 0.7 mm, length S of cutable cutout 24 that can be formed = 0.25 mm to 0.25 mm.
75 mm axial ratio adjusting projections 23a, 23c; width Wt = 1 mm, length Lt = 1 mm axial ratio adjusting projections 23b, 23d; width Wt = 1 mm, length Lt = 2 mm.

As shown in FIG. 4, the resonance frequency fo
Are the projections 21a to 2a on the outer peripheral edge of the four radiation conductors 2.
It was found that each time 1d was shortened by 0.1 mm, the frequency increased by about 0.7 MHz. Accordingly, the resonance frequency fo of the circularly polarized microstrip antenna 1 is finely adjusted by cutting the projections 21a to 21d on the outer peripheral edge of the four radiation conductors 2 by an appropriate amount to gradually increase the frequency. be able to.

As shown in FIG. 5, for example, each of the four radiation conductors 2 has a length S = 0.25 on the outer peripheral edge.
mm notches 24 are formed one by one, the resonance frequency fo
Decreases by about 2.5 MHz, and the length S of the notch 24 is set to 0.3.
It has been found that the amount of decrease in the resonance frequency fo increases by about 1 MHz each time the length is increased by 1 mm. Therefore, the conductor cutout portions 22a to 22d can be formed so that the cutout 24 having an appropriate length can be formed.
The frequency is gradually reduced by increasing the number of the notches 24 formed at the outer peripheral edge of the four radiation conductors 2 to finely adjust the resonance frequency fo of the circularly polarized microstrip antenna 1. It can be carried out.

Next, the frequency adjustment of the circularly polarized microstrip antenna 1 will be described. The resonance frequency fo of the circularly polarized microstrip antenna 1 is determined mainly by parameters of the thickness t of the dielectric substrate 4, the relative permittivity ε of the dielectric substrate 4, and the diameter R of the radiation conductor. Therefore, the design values of the above three parameters are appropriately selected, and the initial frequency of the resonance frequency fo of the circularly polarized microstrip antenna 1 (the radiation conductor 2 and the ground conductor 3 on the front and back surfaces of the dielectric substrate 4).
And the resonance frequency at which the axial ratio at the time of no adjustment is minimized) is slightly lower than the target value. For example, in the example shown in FIG.
It is set to 57 GHz.

Next, when the axial ratio of the circularly polarized wave is not less than the standard value, the operation of cutting the four axial ratio adjusting projections 23a to 23d by the same amount once or several times is carried out. Adjust the wave axis ratio to the specified value or less. Next, if the resonance frequency fo at which the axial ratio after the axial ratio adjustment is minimized is equal to or lower than the target frequency, the frequency adjusting protrusions 21a to 21d are used.
Is performed once or several times to reduce the resonance frequency fo gradually and adjust it to the target frequency. For example, in the example shown in FIG. 4, the target frequency is adjusted to 1.575 GHz.

In the above-mentioned cutting operation, the projections 21a to 21d may be cut one by one in one operation, or a part of the projections 21a to 21d may be cut in one operation and several times. When the first projection is eliminated by the above operation, the second projections 21a to 21d may be cut.

If the above-mentioned protrusions 21a to 21d are excessively cut off and the resonance frequency fo exceeds the target frequency, the outer peripheral edges of the four radiating conductors 2 are guided by the conductor missing portions 22a to 22d in one operation. One notch 24 at each end
Is performed once or several times to form the resonance frequency f
o is gradually reduced and set to the target frequency.

On the other hand, if the resonance frequency fo after the axial ratio adjustment is already equal to or higher than the target frequency, the above-described conductor missing portions 22a to 22a-2
When the resonance frequency fo is gradually lowered by the operation of forming the notch 24 guided by 2d and set to the target frequency, and the resonance frequency fo falls below the target frequency in this operation,
Further, the resonance frequency fo is gradually increased by the above-described cutting operation of the projections 21a to 21d and set to the target frequency.

In the above embodiment, the circular radiation conductor 2
The present invention has been described with reference to a circularly polarized microstrip antenna 1 having a radiating conductor 2 'having a rectangular shape as shown in FIG. It can be applied to the strip antenna 1.

[0040]

As described above, according to the first aspect of the present invention, in the circularly polarized microstrip antenna in which the ground conductor and the radiation conductor are formed on the front and back surfaces of the dielectric substrate, the radiation conductor Projections for adjusting the resonance frequency in a rising direction at positions 90 N ° (N is an integer) with respect to a direction connecting the center of the radiation conductor and the feeding point. the resonance frequency since the form and the conductor lack portion consisting of pores of a guide forming a notch for adjusting the reduction direction, to adjust the length of the collision force
Sri more Moshiku is formed a guide body lack portion as a guide
By adjusting the number of cutouts , the axial ratio of circularly polarized
The resonance frequency can be easily adjusted without affecting other characteristics such as input impedance .

Further, according to the second aspect of the invention, circular polarization 90 N ° of the peripheral edge portion of the radiation conductor of the microstrip antenna (N is an integer) co previously formed in the position in the direction
By cutting a protrusion for adjusting the vibration frequency in the upward direction or by forming a slit-shaped notch for adjusting the resonance frequency in the downward direction by using the conductor lacking portion consisting of a small hole as a guide Since the resonance frequency is adjusted to the target value, the axial ratio of circularly polarized waves, input impedance, etc.
The resonance frequency can be easily adjusted without affecting other characteristics.

Further, even when the frequency exceeds the target frequency in the frequency adjustment operation, the frequency can be readjusted in the reverse direction, and the frequency adjustment failure can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a circularly polarized microstrip antenna according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged view of a protrusion for frequency adjustment, a conductor missing portion, and a protrusion for axial ratio adjustment formed on the outer peripheral edge of the radiation conductor.

FIG. 4 is a diagram illustrating a change amount of a frequency with respect to a cutting amount of a frequency adjustment protrusion.

FIG. 5 is a diagram illustrating a change amount of a frequency with respect to a length of a notch;

FIG. 6 is a view showing the shape of a radiation conductor of a circularly polarized microstrip antenna according to a second embodiment of the present invention.

FIG. 7 is a plan view showing an embodiment of a conventional circularly polarized microstrip antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circularly polarized microstrip antenna 2, 2 'Radiation conductor 3 Ground conductor 4 Dielectric substrate 5 Coaxial cable for feeding 21a to 21d, 23a to 23d Projection 22a to 22d Conductor lacking part P Feeding point

Claims (2)

(57) [Claims] 1. A circularly polarized microstrip in which a ground conductor is formed on one surface of a dielectric substrate and a radiation conductor is formed on the other surface, and a feeding point is provided eccentrically to the radiation conductor. In the antenna, the radiation conductor is an outer peripheral edge thereof, and the axial ratio is adjusted to a position of 45 × (2N + 1) ° (N is an integer) with respect to a direction connecting the radiation conductor center and the feeding point. And one or two or more for adjusting the resonance frequency in the ascending direction at a position of 90 N ° (N is an integer).
Is butt-outs formed, and resonance circumferential protruding the base end portion vicinity of the electromotive
Guide forming a notch for adjusting the wave number in a downward direction
One or more circular polarized microstrip antennas, characterized in that the conductor lack portion consisting of small holes are formed as. 2. A slit-shaped notch is formed at an outer peripheral edge of the radiation conductor by cutting a projection for frequency adjustment formed on the radiation conductor, or by using a conductor lacking portion for frequency adjustment as a guide. 2. The frequency adjustment method for a circularly polarized microstrip antenna according to claim 1, wherein the frequency is adjusted by performing the adjustment.