JPH05206726A - Composite structure radial line slot sntenna - Google Patents

Abstract

PURPOSE:To attain broad band for the antenna by reducing a feeding line length difference to each slot in a radial guide line in order to reduce the gain reduction at a frequence band end. CONSTITUTION:A slot plate 1 forming an antenna aperture with lots of slots arranged thereto is divided into 1A,1B at a position of a half of radius R, a middle plate 3 is inserted to a position corresponding to the inner side 1A to decrease a difference of a feeding line length between a slot excited at first and a slot excited finally among the slots. Since the frequency band is inversely proportional to the difference between the feeding line lengths, the frequency band is doubled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar antenna,
In particular, the present invention relates to a radial line slot antenna suitable for use in the quasi-millimeter wave band such as satellite broadcasting, satellite communication, or terrestrial communication.

[0002]

2. Description of the Related Art As shown in FIG. 8A, a radial waveguide is formed by a slot plate a made of a conductor plate having a large number of slots and a frame b made of a conductor plate facing each other. It is known that an intermediate metal plate d is provided in a similarly formed radial waveguide with a gap f for feeding power bypassing between the peripheral wall e and the peripheral wall e, as shown in FIG. 8B. ing. In the former case, the electric power supplied from the feeding part g at the center of the back surface of the frame b becomes a radial traveling wave h in the radial waveguide from the center to the peripheral edge, and the slot array formed in the slot plate moves from the central part to the peripheral edge. It is an outward traveling wave antenna that is sequentially excited (generally called a single-layer radial line slot antenna). On the other hand, in the latter, an intermediate metal plate d is provided in the radial waveguide with a gap f for feeding power bypassing between it and the peripheral wall e, and the radial waveguide is divided into spaces S ₁ and S _2. There is. Therefore, the electric power supplied from the power feeding unit at the center of the back surface of the frame becomes a radial traveling wave traveling from the center of the space S1 to the periphery, but travels from the periphery of the space S2 to the center through the feeding power bypass gap f. It becomes an inward traveling wave antenna (referred to as a two-layer radial line slot antenna with respect to the former) that sequentially becomes a wave i and excites the slot array formed on the slot plate. In each case, a slot is formed on the entire surface of the slot plate to form an antenna opening surface.

[0003]

In an array antenna in which the radiating element of the antenna is composed of a resonator such as a slot, the gain becomes maximum at the resonance frequency (usually, this is the design value), and this resonance frequency The gain decreases with increasing distance from. That is, within a constant frequency band (used frequency band) having the resonance frequency (design value) as the center frequency, the resonance characteristic is shown in FIG. 6 in which the gain decreases as the resonance frequency is increased. On the other hand, the gain is proportional to the frequency and the aperture area of the antenna. That is, when the opening area is constant, the gain is higher as the resonance frequency is higher (the wavelength is shorter), and when the resonance frequency is constant, the gain is higher as the opening area is larger.

In the array antenna, another factor that determines the frequency band is a feed line length difference for exciting each element. That is, the feed line length ρ _min to the element to be excited first and the feed line length ρ to the element to be excited last.
_It is the distance difference from _max . Letting this be L _S , the frequency band is proportional to 1 / L _S, that is, 1 / (ρ _max −ρ _min ). An array antenna having the same feed line length to each element has a large transmission loss, but L _S is 0 and theoretically the frequency band is infinite.

FIG. 7 shows the maximum gain in the used frequency band and the gain at each frequency band end with respect to the aperture diameter of the radial line slot antenna. For example, regarding a radial line slot antenna with an aperture diameter of 50 cm, the gain reduction amount at the band edge is about 0.5 dB with respect to the maximum gain in the frequency band of 300 MHz, which is not a problem. However, in the frequency bands of 500MHz and 800MHz,
The gain reduction amounts are 1.5 dB and 3.5 dB, respectively. At 800 MHz, as the aperture diameter is increased, the band edge gain is decreased. At present, the specified frequency band is divided into a number of channels for use. Therefore, if the frequency band becomes wider, the quality of the received image on the channels near the ends of the frequency band will be significantly reduced.

In recent years, the output of satellites has tended to decrease in order to prevent interference and theft. At this time, in order to maintain the quality of the received image, it is necessary to improve the performance of the antenna. As one means for this, an increase in the antenna aperture diameter can be considered. Therefore, the gain increases at the resonance frequency to increase the opening diameter, i.e. the slot plate a of the antenna shown in FIG. 8, both L _S is also large L _S for substantially equal to the radius of the slot plate a, the frequency gain The characteristics are as shown in 4 of FIG.
Since the steep resonance characteristic is exhibited, the amount of decrease in gain between the maximum gain and the end of the frequency band is further increased, which is not practical.

Therefore, an object of the present invention is to provide a radial line slot antenna in which the amount of gain reduction at the end of the used frequency band is small.

[0008]

The present invention has been made to solve the above problems, and a radial waveguide comprising a slot plate having a large number of slots and a frame arranged to face the slot plate. A radial line slot antenna comprising a power supply section for supplying electric power into the radial waveguide, wherein an inward traveling wave excitation section in which a traveling wave traveling from a peripheral edge toward the center excites the slot, and a radial direction from the center to the peripheral edge A composite structure radial line slot antenna, characterized in that an intermediate plate that divides a traveling wave traveling toward a slot into an outward traveling wave excitation portion that excites the slot is disposed in the radial waveguide.

Further, in the radial line slot antenna of the composite structure, the slot arrangement of the slot plate is different between the inward traveling wave exciting portion and the outward traveling wave exciting portion.

Further, in the radial line slot antenna having a composite structure, the spiral direction in which the slots of the slot plate are arranged is different between the inward traveling wave excitation portion and the outward traveling wave excitation portion.

[0011]

With the above-mentioned structure, the electric power supplied from the power feeding portion is divided into the inward traveling wave excitation portion and the outward traveling wave excitation portion, and the slot array is sequentially excited from this division point. , The feed line length difference between the first excited slot and the last excited slot is reduced.

That is, a case where the radius of the opening surface is divided into a: b will be described. The opening surface is divided into an inner part and an outer part at the position of a: b of the radius. An inner plate is provided inside the radial waveguide and is divided into an inner upper part and an inner lower part. The power supplied from the power supply unit is first transmitted as a radial traveling wave from the center of the inner lower portion to the periphery. Then, at the peripheral edge of the middle plate, the inner upper part is divided into a traveling wave that converges from the peripheral edge toward the center (inward traveling wave) and an outer portion is divided into a radial traveling wave (outward traveling wave) extending from the center toward the peripheral edge. It The inward traveling wave excites the inner slot array and the outward traveling wave sequentially excites the outer slot array from the division points. That is, the inner portion is the inward traveling wave excitation portion, and the outer portion is the outward traveling wave excitation portion. Therefore, the feeding line length difference L _S of the inward traveling wave excitation unit is a / (a + b), and the feeding line length difference L of the outward traveling wave excitation unit is
_S will be shortened to b / (a + b). For example, if a <b, the used frequency band is inversely proportional to the feed line length difference L _S, and thus the band is widened by (a + b) / b.

Since the directions of the traveling waves exciting the respective slot arrays are different between the inner portion and the outer portion, the inner portion has a slot of the inward traveling wave antenna in which the traveling waves converging from the peripheral edge toward the center are excited. The outer part is the same as the slot configuration of the outward traveling wave antenna in which the radial traveling wave (exciting wave) from the center to the peripheral direction is excited, so that the outer portions do not cancel each other out from the entire opening surface and are the same. Radio waves with the plane of polarization of are emitted.

Further, when the slots are arranged in a spiral, by making the directions of the spiral different in the inner part and the outer part, radio waves having the same plane of polarization without canceling each other out from the entire opening surface. Is emitted.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention.
A radial waveguide (hereinafter, simply referred to as “waveguide”) is formed by the frame 2 made of a conductor and the slot plate 1 made of a conductor provided so as to face the frame 2. The slot plate 1 has slots arranged at predetermined positions, and is divided into an inner portion A and an outer portion B at a position having a half radius (that is, a: b = 1: 1). 1 each
And _A, 1 _B. Therefore, the opening area ratio S _A : S _B of the inner portion A and the outer portion _B is 1: 3. In the inner part A in the radial waveguide, a middle plate 3 corresponding to the division of the slot plate 1 is provided, and a slow wave circuit 7 _{A made of a} low foamed dielectric material is provided on the middle plate 3.
It is inserted in parallel with the slot plate 1 with the interposition of. In the center, a radio wave absorber 10 _A lined with metal
Is installed. Corresponding to the division of the slot plate 1, the frame 2 has a concave portion 4 formed on the inner side thereof, and a terminal portion thereof forms a corner portion 6 having an edge cut. A feeding portion 5 made of a coaxial line is coupled to the center of the back surface of the frame 2. The power feeding section 5 is composed of a coaxial line having a top loading section 8 at its tip.
In addition, a spacer 7 made of a highly foamed dielectric having a dielectric constant equal to that of air is interposed in the radial waveguide constituted by the frame recess 4 and the intermediate plate 3, and the intermediate plate 3 is formed.
Are held at a predetermined interval. Further, a slow wave circuit 6 _B made of a low foaming dielectric material is interposed on the outer side portion B of the radial waveguide. The height d _A between the slot plate 1 and the intermediate plate 3 of the inner portion A, the height d _B of the slot plate 1 and frame 2 of the outer part _{B d A: d B = 1} : set to 3.

The power of the TEM wave supplied from the power supply section 5 is passed through the probe provided with the top loading section 8 of the coaxial line to the periphery from the center in the waveguide constituted by the frame recess 4 and the intermediate plate 3. It is transmitted as a radial traveling wave toward. This traveling wave is split into a waveguide at the outer portion B and a waveguide at the upper portion of the inner portion A at the peripheral portion of the intermediate plate 3. Here, since the corner portion 9 is formed at the terminal end of the frame concave portion 4 corresponding to the intermediate plate 3, the frame concave portion 4 is smoothly divided. The cut amount of the corner portion 9 is a value corresponding to the distance between the frame 2 and the middle plate 3. Then, the slot array is sequentially excited from this division point. The outer portion B is a waveguide constituted by the slot plate 1 _B , the slow wave circuit 6 _B , and the frame 2, and is an outward traveling wave excitation portion that excites the slot array of the slot plate 1 _B by an outward traveling wave traveling from the center toward the periphery. Become. Further, the upper portion of the inner portion A, slot plate 1A, the waveguide is constituted by the slow-wave circuit 6A, intermediate plate 3, inward traveling wave that excites the slot array of the slot plate 1 _A by inward traveling wave toward the center from the periphery It becomes an exciter.

Here, the slow wave circuit 6 made of a low foam dielectric material
_A, 6 _B, it is preferable to use a same material, the same dielectric constant. In this way, it becomes easy to divide the power supplied from the power supply unit 5 into the waveguides of the inner portion A and the outer portion B according to the opening area. Further, in order to smoothly divide the supplied power, it is preferable that the radius of the intermediate plate 3 be slightly smaller than the radius R of the dividing point and the radius of the frame recess 4 be slightly larger than R.

Residual power that cannot be radiated by the slot array of the inward traveling wave excitation part of the inner part A is absorbed and extinguished by the radio wave absorber 10A in the central part. Residual power that cannot be radiated by the slot array of the outward traveling wave excitation part 4 of the outer part B is absorbed and extinguished by a radio wave absorber (not shown) at the peripheral end. In addition, a matching element such as a matching slot or a matching spiral may be provided at this peripheral end portion to positively radiate the residual power and effectively utilize the residual power.

With this structure, the opening surface
The slot array will be excited sequentially from the division points.
Therefore, the feed line length compared to the conventional antenna shown in FIG.
Difference L _SBecomes 1/2. That is, the frequency band is L_SContrary to
For example, if the gain at the band edge is the same, the frequency
The number of bands is doubled (5 in FIG. 6). See also Microstori
Unlike the power supply by the up line, the waveguide with less loss
Since it is configured, it has a wide band and low loss.

Next, one embodiment of the slot plate of the present invention is shown in FIG. This is a case where the slot array is arranged so as to correspond to the horizontal polarized wave in the positive direction of the X axis (arrow in the figure) of the linear polarized wave. The antenna opening surface is divided into an inner part A and an outer part B at a position of radius R, and the inner part A
The inward traveling wave from the edge toward the center excites the slot array. The angle between the longitudinal direction of the two slots 11 ₁ and 11 ₂ and the Y axis on the intersection of the X axis and the angle φ on a concentric circle having a radial interval of 1/2 of the guide wavelength λ g is θ ₁ , As θ ₂ , a pair slot 11A having a relationship of θ ₁ = φ / 2 θ ₂ = φ / 2−π / 2 is used as a slot array. At this time, the combined radiation wave of the pair slot 11 _A becomes a horizontally polarized wave in the positive direction of the X axis. And
The circumferential spacing Sφ is so dense that adjacent pair slots do not mechanically interfere with each other, and are arranged on concentric circles with a radial spacing Sρ = λg.

On the other hand, in the outer portion B, an outward traveling wave traveling from the center toward the peripheral edge excites the slot array, and the radial distance between the X axis and the angle φ on a concentric circle of 1/2 of the guide wavelength λ _g . Letting θ ₃ and θ _{4 be the} respective angles between the longitudinal directions of the two slots 11 ₃ and 11 ₄ on the intersection and the Y axis, θ 3 = φ / 2−π / 2 θ ₄ = φ / 2−π The related pair slot 11 _B is used as a slot array. At this time, the combined radiation wave of the pair slot 11 _B becomes a horizontally polarized wave that extends in the positive direction of the X axis. The circumferential spacing Sφ is set so dense that adjacent pair slots do not mechanically interfere with each other, and the radial spacing Sρ = λg
Are arranged in concentric circles.

By arranging the slot arrays in this way, all the radio waves radiated from the aperture plane have the same polarization, and the radiated power has a uniform distribution over the aperture plane.

FIG. 5 is a diagram showing another embodiment of the slot array. This shows a right-handed circularly polarized wave corresponding to BS. The inner portion A is an inward traveling wave excitation portion, and the outer portion B is an outward traveling wave excitation portion. Also, these are composed of the same conductor disk.

First, the inner portion A will be described. Assuming that the wavelength used is λ, and the guide wavelength of the waveguide (incoming traveling wave excitation part) is λg, the slot length is λ / 2, the longitudinal directions of the slots are orthogonal to each other, and the center distance is λg / 4. _A pair of letters is used as a pair slot 12 _A so that the composite wave is circularly polarized. Further, in order to cancel the reflected waves from the pair slots 12 _A to the waveguides, pair slots are arranged on the spiral of Archimedes to form a slot array. The archimedean spiral turns clockwise when viewed in the clockwise direction when facing the slot plate.

Next, assuming that the used wavelength is λ and the guide wavelength of the waveguide (outgoing traveling wave excitation part) is λg, the outer portion B similarly has a slot length of λ / 2 and a longitudinal direction of the slots. orthogonal, and center distance is paired slot 12 _B of the pair of shaped Ha is a lambda] g / 4. Moreover, in order to cancel the reflected waves from the pair slots 12 _B to the waveguides, the pair slots are arranged on the spiral of Archimedes to form a slot array. The direction of the spiral of Archimedes is opposite to that of the inner part A because the outward travel excites the slot array. In other words, by setting the counterclockwise direction when facing the slot plate, a right-handed circularly polarized wave is obtained.

Here, the performance improvement of the antenna is to make the amplitude and phase of the radiated power uniform in the entire aperture plane. In the inward traveling wave excitation portion (inner portion A), the slots are sequentially excited from the peripheral edge toward the center. The attenuation of the traveling wave in the radial waveguide is proportional to 1 / √ρ, where ρ is the radial length, but the number of slots decreases sharply from the periphery toward the center, so paired slots are arranged. Sρ is the radial distance of the spiral, Sφ is the circumferential distance of the paired slot, and l is the slot length.
Even if all of g, Sφ = λ / 2, and l = λ / 2 are constant, the radiated power has a substantially uniform distribution. Moreover, since the supplied power is almost radiated from the pair slot, the residual power that converges to the center becomes extremely small. High efficiency can be achieved by absorbing and extinguishing this small amount of residual power by the radio wave absorber backed by the central metal.

On the other hand, in the outward traveling wave excitation portion (outer portion B), the traveling wave in the waveguide is directed from the center toward the peripheral edge,
Similarly, it attenuates in proportion to 1 / √ρ. Moreover, since the number of slots rapidly increases from the center toward the peripheral direction,
Considering the radiated power from the pair slot and the wavelength shortening effect of the slow wave circuit in the waveguide, Sρ is gradually decreased with respect to λ and Sφ is set to 0.35 in the peripheral portion.
Gradually increase from λ to 0.5λ so that the paired slots are close to each other so that they do not mechanically interfere with each other. Slot length is the inner circumferential side l _1, the central portion when the peripheral edge side and l ₂ is set to l ₁ <λ / 2 in order to suppress radiation, l ₂ ≒ 1.2 l gradually increases toward the periphery _By setting the slot to ₁ and increasing the radiation rate by increasing the coupling rate of the slots, the radiation power on the aperture plane is made uniform.

However, in the case of such a slot array, about 20% of the excitation wave propagates to the peripheral portion as residual power. By making effective use of this residual power, higher performance can be achieved. That is, the coupling ratio of the slots is made constant from the position inside the second roll from the circumferential end. That is, if Sρ, Sφ, and l in this portion are made constant, the traveling wave is attenuated and the radiant energy has a non-uniform distribution, but the residual power can be reduced to several percent, so that the total radiated power is increased and high performance is achieved. ..

Further, at the boundary point between the inner side portion A and the outer side portion B, the spiral direction is reversed and the paired slots are overlapped with each other, so that this is avoided and the end point of the inner side portion A is arranged so as to be densely arranged in the opening surface. By arranging the starting point of the outer side portion B at a symmetrical position with respect to the center of the spiral, it is possible to effectively utilize the entire opening surface. Therefore, the partition wall is composed of a semicircle with radii R ₁ and R ₂ , and is (R ₁ + R ₂ ) / 2 = (ρ _max −ρ _min ) / 2.
The end portion of the middle plate has a shape that is slightly smaller than the partition wall with a predetermined distance. Further, in the present embodiment, the slot arrangement has been described for the right-handed circularly polarized wave corresponding to the BS, but if it is turned over, it becomes the left-handed circularly polarized wave.

By arranging the slot arrays in this way, the radio waves radiated from the aperture plane are all the same polarization in both circular polarization and linear polarization, and the radiated power is uniform over the entire aperture plane. It becomes a high-performance antenna that is distributed.

As described above, in the radial line slot antenna of this embodiment, the inner portion A satisfies the condition of the inward traveling wave antenna, and the outer portion B satisfies the condition of the outward traveling wave antenna. In other words, it is a composite structure radial line slot antenna that combines these. Therefore, with respect to the power distribution of the traveling wave that excites the slot array shown in 2 of FIG. 3, radio waves having the same polarization plane are radiated from the full aperture plane without canceling each other, and the radiated power is As shown in No. 3-3, it becomes a high-performance antenna with a uniform distribution over the entire aperture surface. Moreover, if the amount of gain reduction at the end of the frequency band is constant, the frequency band is doubled.

In this embodiment, the case where the antenna aperture plane is divided into two has been described, but the case where the antenna aperture plane is divided into three or more can be similarly configured. In this case, a wider band can be obtained.

[0033]

As described above, according to the present invention, the longest difference of the feed line length of each element forming the array antenna is reduced by dividing the antenna aperture plane and feeding the power. A wideband antenna with a small amount of gain reduction can be provided. Moreover, unlike the power feeding by the microstrip line, since the radial waveguide has a small loss, a high-performance antenna with a wide band and low loss can be obtained.

Further, since the slots are arranged in accordance with the direction of the traveling wave that excites the slot array on each of the division planes of the aperture plane, radio waves having the same polarization plane are radiated from the entire aperture plane without canceling each other. The radiated power has a uniform distribution over the aperture surface.

Further, when the slots are arranged on a spiral, the spiral directions are made different between the inner part and the outer part, so that the slots do not cancel each other out from the entire aperture plane and have the same polarization plane. Radio waves are radiated, and the radiated power has a uniform distribution over the entire aperture surface.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing power supply power of the embodiment.

FIG. 3 is a diagram showing a relationship between an aperture diameter of an array antenna and radiated power and fed power.

FIG. 4 is a diagram showing an embodiment of the slot plate of the present invention.

FIG. 5 is a view showing another embodiment of the slot plate of the present invention.

FIG. 6 is a diagram showing a relationship between a gain of an array antenna and a frequency band.

FIG. 7 is a diagram showing the relationship between the aperture diameter of the array antenna and the maximum gain and frequency band edge gain.

FIG. 8 is a diagram showing a conventional radial line slot antenna.

[Explanation of symbols]

 1 Slot plate 2 Frame 3 Middle plate 4 Recessed part 5 Feed part 6 Slow wave circuit 7 Spacer 8 Top loading part 9 Corner part 10 Electromagnetic wave absorber 11, 12 Pair slot

Claims (3)

[Claims] 1. A radial waveguide comprising a slot plate having a large number of slots and a frame arranged so as to face the slot plate, and a power feeding section for supplying electric power to the radial waveguide. In a radial line slot antenna, a traveling wave traveling from the peripheral edge toward the center is divided into an inward traveling wave excitation portion that excites the slot, and a traveling wave traveling from the center toward the peripheral edge is divided into an outward traveling wave excitation portion that excites the slot. A composite structure radial line slot antenna, wherein an intermediate plate is provided in the radial waveguide. 2. The composite structure radial line slot antenna according to claim 1, wherein the arrangement of the slot array of the slot plate is different between the inward traveling wave excitation portion and the outward traveling wave excitation portion. 3. The composite structure radial according to claim 1, wherein the spiral direction in which the slots of the slot plate are arranged is different between the inward traveling wave excitation portion and the outward traveling wave excitation portion. Line slot antenna.