JP2785825B2 - Planar antenna - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar antenna suitable for use, for example, in receiving satellite broadcasts. [Summary of the Invention] The present invention provides a suspended line-fed planar antenna, in which a planar resonator type printed element is disposed on a substrate corresponding to a hole provided in one of a pair of metals or metallized plastics. Shape, light weight,
It is intended to reduce the cost, reduce the transmission loss and widen the bandwidth. [Prior Art] Conventionally, in a suspended line feed type planar antenna in which a substrate is sandwiched between metal or metallized plastic having a large number of holes forming a part of a radiating element, a pair of excitations orthogonal to each other corresponding to the large number of holes, respectively. A circularly polarized plane array antenna has been proposed in which probes are formed on a common plane, and a feed signal to a pair of excitation probes is phase-synthesized within a suspended line (Japanese Patent Application No. 60-163).
No. 162650). This makes it possible to reduce the thickness, simplify the mechanical structure, and use a low-cost, commonly available substrate for high-frequency use, equivalent to or more than an expensive microstrip line substrate. Antenna gain is obtained. In addition, the suspended line has an advantage that a low-loss line can be formed as a feeding circuit of a planar antenna, and it can be formed on an inexpensive film-shaped substrate.Because a circular or rectangular waveguide aperture element is used as a radiating element, An array antenna with a small gain deviation over a relatively wide band can be configured. On the other hand, a so-called patch type microstrip line antenna element can be considered as a means for reducing the thickness. FIG. 7 shows an example of a general circular patch-type microstrip line antenna. FIG. 7A is a top view and FIG. 7B is a side view. In Figure 7, (11) the base plate (12) is a dielectric having a relative dielectric constant epsilon _r, (13) is a printed element as a patch. The resonance frequency is substantially determined by the diameter D of the print element (13). In general, when the feed line and the radiating element are formed on the same plane, radiation loss in the feed line is small, and increasing the radiation efficiency of the radiating element is mutually contradictory. Therefore, the patch-type microstrip line antenna shown in FIG. In the case of, the characteristic is narrow band (gain) (IEEE Transaction on Antennas & Propagat
ion, Vol. AP-29, No. 1, Jan. '81, etc.). Also, there is an example in which the gain is broadened by adding a parasitic element or the like on a multilayer substrate (IEEE Transac).
tionon on Antennas & Propagation, Vol.AP-27, No.3,
May. '79 PP 270-273). In FIG. 8, (11)
(13) is the same as FIG. 7, (14) is air or dielectric, (15) is a printed element as a parasitic element, (16)
Is a dielectric. Furthermore, in the case of circular polarization, several elements are paired,
In some cases, the phase ratio (spatial phase and feeder phase) is changed to broaden the axial ratio. [Problems to be Solved by the Invention] By the way, in the case of the circularly polarized planar array antenna described in Japanese Patent Application No. 60-162650 or the like, the thickness of the radiating element (substantially the first metal plate and the 2).
6.5 kg when the weight of the antenna is metal because it is about 5 cm
(In case of 40cm square), even if metallized plastic is used, it will only be about 2-3kg (in case of 40cm square).
It is difficult to make thin and difficult to handle because it lacks commerciality.In addition, metallized plastic requires a molding die, so it is expensive, and mass production is poor from the viewpoint of warpage and uniformity. In the case of metal as well, a cutting step is required, so that there are disadvantages such as poor mass productivity and high cost. Further, the seventh view of such a patch-type microstrip line antenna as described above, for the broadband may reduce the relative dielectric constant epsilon _r of the dielectric (12), the substrate thickness i.e. dielectric h Conversely thickness However, in this case, the relative dielectric constant ε _r is as large as 2 to 2.5, and when the substrate thickness is increased, the radiation loss in the feeder line increases, so that it cannot be increased so much. There was a drawback that the band was narrow, about 200 MHz. In addition, in the case of FIG. 8, since a plurality of substrates are used, there is a disadvantage that the configuration becomes complicated and the cost becomes high. In any case, the microstrip line structure as shown in FIGS. 7 and 8 has a disadvantage that even if a low dielectric constant and low loss substrate is used, the transmission loss is relatively large, and the device must be designed to have a wider band. there were. The present invention has been made in view of the above point, and makes use of the features of the suspended line, and achieves high efficiency and wide band by using a thin radiating element, and at the same time, simultaneously achieves thinning and lightening. The present invention provides a planar antenna as described above. [Means for Solving the Problems] The planar antenna according to the present invention is composed of a pair of metal plates or metallized plastic plates (1), (2) provided with holding portions (4), (6) provided on a substrate (3). In the suspended line feed type planar antenna sandwiching the
A plurality of planar resonator print elements (8) arranged above and resonating at a predetermined frequency are connected to each other by a suspended line, and a cavity (7) formed in a part of the holding parts (4) and (6). A suspended line is placed inside,
The planar resonator type print element (8) has notches (8a), (8) opposed to a position at a predetermined angle with respect to the suspended line.
b), a metal plate or a metallized plastic plate (1) facing the planar resonator type printed element (8),
In (2), a hole (5) corresponding to the shape and size of the planar resonator print element (8) is provided so as to be surrounded by the holding portion (6). [Operation] A suspended line power supply type in which a substrate is sandwiched between a pair of metal plates or metallized plastic plates. By providing holes corresponding to the shape and size of the planar resonator print element in the metal plate or metallized plastic plate facing the planar resonator print element,
It is possible to achieve a reduction in thickness, weight, and cost, as well as a low transmission loss and a wide band. Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 shows the configuration of a circularly polarized radiating element according to the present invention. FIG. 1A is a top view thereof, and FIG. 1B is a sectional view taken along line II in FIG. 1A. is there. In FIG. 1, (1) is a first metal plate (or metallized plastic plate), (2) is a second metal plate (or metallized plastic plate), and (3) is first and second metal plates ( 1) A thin film substrate (film-like flexible substrate) sandwiched between (2). The first metal plate (1) has a convex holding portion (4) for holding the substrate (3),
The second metal plate (2) has, for example, a so-called slot-shaped hole (5) having a diameter of 14 mm and a convex holding portion (6) provided around the hole (5) for holding the substrate (3). Have. A substrate (3) comprising first and second metal plates (1) and (2);
Are positioned so that the holding portions (4) and (6) coincide with each other. At this time, the thicknesses of the first metal plate (1) and the second metal plate (2) are extremely thin,
For example, each is about 2 mm. When the substrate (3) is sandwiched between the first and second metal plates (1) and (2), a cavity (7) communicating with the hole (5) is formed. (8) is a hole (5) in the second metal plate (2) in the substrate (3).
A conductive foil as a so-called patch-shaped planar resonator type printed element which is concentrically attached to the hole (5), and the conductive foil (8) is provided through a hollow portion (7). To form a suspended line. In this case, the substantially circular conductor foil (8) has a diameter that resonates at a predetermined frequency, and has a notch facing a position at a predetermined angle, for example, 45 ° with respect to the suspended line for receiving or transmitting circularly polarized waves. (8a) and (8b) are provided. And in this example, when transmitting or receiving radio waves from the front side of the paper,
It is designed for right-handed circular polarization. It should be noted that notches (8a) and (8b) for left-handed circular polarization may be provided on the opposite side of the suspended line from those for 45 ° right-handed circular polarization. FIG. 2 shows a structure of a suspended line for feeding power to the planar array, and shows a state cut along a line II-II in FIG. 1B. Here, for example, a conductive foil (8) formed by etching a printed board (3) of about 25 to 100 μm is surrounded by first and second metal plates (1) and (2), and a medium cavity axial line is formed. Make up. That is, the suspended line is composed of the first and second metal plates (1) and (2).
Is located in the cavity (7) formed by In this case, since the substrate (3) is thin and functions only as a supporting member, a feed line with little transmission loss can be provided even if it is not a low-loss substrate. For example, the transmission loss of an open strip line using a Teflon glass substrate is 4 to 6 dB / m at 126 Hz, but about 2.5 to 3 dB with a 25 μm film substrate for a suspended line.
/ m. The flexible substrate in the form of a film is inexpensive as compared with the Teflon glass substrate, and thus has an advantage including the configuration (characteristics). FIG. 3 shows the characteristics of the circularly polarized wave radiating element according to the present invention.
It is -14 dB or less (VSWR <1.5) in a 900 MHz bandwidth, and the gain is relatively wide. This is because the height h from the upper surface of the first metal plate (1) to the upper surface of the substrate (3) is h1 mm, while the air between the first metal plate (1) and the substrate (3) has This is because the equivalent relative permittivity _{er er,} which is the relative permittivity of the substrate (3), can be reduced to ε _er 1.05. FIG. 4 shows an example of the measurement of the axial ratio of circularly polarized waves. For example, the allowable range is about 1 dB at a frequency of 12 GHz. It can be seen that the planar antenna according to the present invention satisfies this sufficiently. FIG. 5 shows a circuit configuration in which a plurality of circularly polarized radiating elements as shown in FIG. 1 are co-phase-fed with suspended lines, thereby forming an array. The solid line portion in FIG. 6 shows a state cut along the line III-III in FIG. 5, and the broken line portion in FIG. 6 covers the state shown in FIG. 5 with the second metal plate (2) from above. It shows the state where it was turned on. Here, the first metal plate (1) is provided with a holding portion (4) for holding the substrate (3) corresponding to the periphery of the hole (5) formed in the second metal plate (2). . In addition, metal plate (1)
A holding portion (4) for holding the substrate (3) is also provided around a power feeding portion (9) penetrating through the substrate. Further, a holding portion (4) is provided also on the outer peripheral portion of the array. Other parts constitute the cavity (7). As a result, a plurality of conductor foils (8) may pass through the same cavity (7), and there is a concern about mutual coupling. However, the interval between the conductor foils (8) and the upper and lower walls of the cavity (7) are different. By properly selecting the interval, necessary isolation can be obtained, and there is no problem. At this time, the lines of electric force are concentrated on the upper and lower walls of the cavity (7), so that the electric field along the supporting substrate (3) almost disappears, thereby reducing the dielectric loss and consequently the line loss. Transmission loss will be reduced. Further, a holding portion and a hollow portion are also formed on the second metal plate (2) corresponding to the first metal plate (1). That is, the holding portion (6) is provided around the hole (5) drilled in the second metal plate (2), around the power supply portion (the upper surface is closed), and around the array outer periphery. The portion is a cavity (7) (see FIG. 6). Since the substrate (3) is uniformly held by the holding portions (4) and (6) provided in this manner, the substrate (3) does not sag, and the surroundings of each radiating element, the feeding portion, and the like are formed of the same metal as the conventional one. Since the plates (1) and (2) are brought into close contact with each other, resonance at a specific frequency does not occur. In FIG. 5, the 16 radiating elements are divided into _four groups G _{1 to} G ₄ with _four as one set. Connection point P _{1 of} each group
Is shifted from the center by λg / 2 (λg is the line wavelength at the center frequency), and the connection points P ₂ and P ₃ are connected by being shifted by λg / 4. Thus, in each group, the lower right radiating element is 90 ° with respect to the upper right radiating element, and the lower left radiating element is 18 °.
The radiating elements at 0 ° and at the upper left will be out of phase with each other by 270 °, which improves the axial ratio. That is,
By changing the spatial phase and the feeder phase, the axial ratio is broadened. The connection point P ₁ and P ₄ to P ₆ for each group are interconnected so as to be equidistant with respect to the feeding of the feed section (9) (10). In such a configuration, the connection points P ₁ and P ₄
It is possible to obtain various directivity characteristics by changing the position of the to P ₆ changing the feeding phase and the power distribution ratio. That is, the phase is changed by changing the distance from the feed point (10) to the connection point P ₁ and P ₄ to P _6, also, or, or thicker thin line where branches of the suspended line By changing the impedance ratio, the amplitude changes, whereby the directional characteristics can be changed arbitrarily. As described above, in this embodiment, the thickness of the radiating element (the thickness of the first metal plate and the second metal plate) is about 4 mm, so that the weight of the antenna is about 1.1 kg (in the case of a 40 cm square). ,
In the case of metallized plastic, it becomes 0.3-0.5kg (in the case of 40cm square), and it is lighter and thinner. In addition, since the thickness is small, metal pressing can be performed, mass productivity is improved, and cost reduction and commercialization can be achieved by combining weight reduction and thinning. Also, the equivalent relative permittivity ε _er
Can be reduced to 1.05, so that the gain can be broadened. Further, a suspended line is used as a power supply line, and a hole (5) provided in the second metal plate (2) is formed in a so-called slot shape, and its diameter is reduced to about 14 mm. Since the feeder line can be made thicker, transmission loss can be reduced. Further, the gain (efficiency) of the antenna can be increased by widening the gain and reducing the transmission loss. Although the radiating element has been mainly described in the above-described embodiment, the radiating element (or an antenna formed by an array of radiating elements) can be used as a receiving element (receiving antenna) without any change in characteristics due to the reversible principle of the antenna. Of course). Further, in the above-described embodiment, the case where the shape of the planar resonator type print element is circular has been described as an example. However, the present invention is not limited to this, and other shapes may be used. Further, in the above-described embodiment, the case where the present invention is applied to the frequency band of 12 GHz is applicable to other frequency bands by changing the dimensions of the element. [Effects of the Invention] As described above, according to the present invention, a plurality of planar resonator type print elements that resonate at a predetermined frequency are connected to each other by a suspended line, and the suspended line is formed in a cavity formed in a part of the holding unit. The planar resonator type print element is provided with a notch at a predetermined angle position with respect to the suspended line, and the planar resonator type print element is formed on a metal plate or a metallized plastic plate facing the planar resonator type print element. Since the holes corresponding to the shape and size of the print element are provided so as to be surrounded by the holding part, weight reduction,
The antenna can be made thinner, the cost can be reduced, the mass productivity and the commercialization can be improved, and the gain (efficiency) of the antenna can be improved by widening the gain and reducing the transmission loss in the feed line.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view and a sectional view showing one embodiment of the present invention;
FIG. 2 is a sectional view of a main part of the present invention, FIG. 3 and FIG. 4 are characteristic diagrams of a circularly polarized wave radiating element according to the present invention, FIG. FIG. 6 is a cross-sectional view taken along line III-III of FIG. 5, and FIGS. 7 and 8 are each a configuration diagram of a conventional example. (1) is a first metal plate (or metallized plastic plate), (2) is a second metal plate (or metallized plastic plate), (3) is a substrate, (4) and (6) are holding portions,
(5) is a hole, (7) is a cavity, and (8) is a conductor foil.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Fumihiro Ito               6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo So               Knee Co., Ltd.                (56) References JP-A-62-23209 (JP, A)                 JP-A-61-281704 (JP, A)

Claims (1)

(57) [Claims] In a suspended line-feeding planar antenna sandwiching a substrate between holding members provided on a pair of metal plates or metallized plastic plates, a plurality of planar resonator-type printed elements having a shape and size resonating at a predetermined frequency are provided on the substrate. The plurality of planar resonator print elements are connected to each other by a suspended line disposed on a substrate, a cavity is formed in a part of the holding unit, and the suspended line is disposed in the cavity. Wherein each of the plurality of planar resonator print elements is provided with a notch at a predetermined angle with respect to the suspended line, and a front surface of the substrate facing the planar resonator print element. On the metal plate or metallized plastic plate on the side,
A planar antenna, characterized in that holes corresponding to the shape and size of the planar resonator print element are provided so as to be surrounded by the holding portion.