JPH057110A - Flat plate type slot antenna - Google Patents

Abstract

PURPOSE:To attain the excellent matching performance for a feeder or a signal conductor and to reduce an antenna input impedance so that the antenna is applied for a microwave band required for mobile body communication even for a broad band of two frequencies. CONSTITUTION:A sub slot 4 to expand a band width of a resonance frequency over a wide range is arranged longitudinally by adjusting the lengthwise size of the slot 4 to both edges of a main slot 3 in the lengthwise direction via a sub current path 5 and the main slot and a feeder 2 are provided in crossing directly or at an interval.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact and high performance flat plate type slot antenna suitable for application in the microwave band such as mobile communication such as cellular telephone.

[0002]

2. Description of the Related Art Conventionally, a conductor layer adhered to an exposed surface of a dielectric substrate is used as a signal conductor to form an elongated slot for electromagnetic coupling from a signal conductor spaced apart from the slot, or a single conductor plate. There is known a flat plate type slot antenna in which a long and narrow slot is provided and a feeding line is directly arranged.

When a dielectric substrate is used, the relative dielectric constant,
When the thickness and slot width are known, the resonance length of the antenna depends on the slot length and relative permittivity, and the characteristic impedance of the feed line is determined by the relative permittivity, thickness, and line width length. In order to match the impedance of the slot, the resistance value, which is the real part viewed from the feeding side of the slot, can be made equal to the characteristic impedance of the feeding line, or can be set to an appropriate length by selecting the offset length from the center of the slot. However, in general, the frequency band where impedance matching with the power feed line can be obtained is narrow, and when it is used in a wide band of two frequencies such as mobile communication, it cannot be put to practical use unless measures are taken for widening the band. Is.

Therefore, in the past, 1) a first feeding path in which a feeding strip line conductor (feeding line) is orthogonal to the slot at a position offset from the center of the slot to one end side, and from this tip A second feed path that is bent in parallel and faces the slot, 2) A plurality of sub-conductors parallel to the long sides of the slot are provided in the slot, 3) At least a slot is formed on one surface, and the dielectric There is one having two power supply lines and a demultiplexer on the other surface sandwiching the body.

In the above 1), since the inductance component and the capacitance component are added in parallel with the slot, it is difficult to analyze and determine the shape and characteristics of the optimum feed line, and 2) the parallel of two slots. Due to the arrangement, there is a concern that radiation from both slots may interfere with each other to deteriorate the directivity of the horizontal plane, and regarding 3), it is necessary to add a duplexer in addition to the two power supply lines. However, the power supply mechanism is complicated, and there is a drawback in that it is inevitable that the power supply will become large as a whole.

[0006]

Thus, in order to eliminate the above-mentioned drawbacks of the conventional flat plate type slot antenna, the present invention focuses on the current flow path from the feed line or the signal conductor to the conductive portion around the slot and resonates. The characteristic bandwidth can be easily adjusted to reduce the antenna input impedance, and
The purpose of the present invention is to achieve good matching with the power supply line or the signal conductor and to reduce the size as a whole.

[0007]

A sub-slot whose length in the longitudinal direction can be adjusted by mainly forming a slot opened to a ground conductor and separating a sub-conducting flow path branched from the main conductive flow path at each of both longitudinal edges thereof. Are arranged in tandem, and the feed line crossing the main slot directly or with a space is electromagnetically coupled.

[0008]

Embodiments of the present invention will be described in detail below with reference to FIGS. First, in FIG. 1, the slots 3 are opened in the conductive plate 1, and the sub-slots 4 are arranged in tandem at the end edges in the longitudinal direction with the sub-conductive channels 5 separated from each other. A signal is input from the power feeding line 2 by the conductor 2-1 with the widthwise end of the slot as a power feeding end.

In FIG. 2, the dielectric 10 is connected to the ground plate 1 and the signal conductor 2.
Similarly, the main slot and the sub-slots are arranged in tandem on the ground plate side with the sub-conducting flow paths separated from each other on both end edges, and the thickness of the main slot and the dielectric from the ground plane side. The power is supplied from the signal conductor (in this case, a microstrip line) so as to intersect with each other at a distance.

The flow of the feed current from the feed line to the main and sub slots will now be described with reference to FIG. 3 showing the upper surface of FIG. 1. A main conductive flow path C ₁ is formed around the main slot, At the same time, a conductive flow also flows in the outermost flow path C ₂ including the sub-slots formed at both ends of the slot in the direction of the arrow. Around the main slot, a conductive flow passing through the sub-conductive channel and a conductive flow flowing through the outer periphery including the sub-slot are provided.
Since the system has two resonance points due to the conductive flow of the system, it contributes to widening the frequency band and reducing the impedance of the entire antenna.

FIG. 4 is a graph showing the measurement results of the reflection characteristics of the slot antenna of the present invention and the conventional slot antenna in the 2-3 GHz band, for example. The solid line (a) shows the dot-dash line of the slot antenna of the present invention ( (B) is the voltage standing wave ratio vs. operating frequency characteristic of the conventional one.

As can be seen from FIG. 4, the voltage standing wave ratio is 2.0.
When viewed from the order of magnitude or less, the slot antenna of the present invention has a relative bandwidth (= bandwidth / f ₀ ) of 37% with the center frequency of f ₀ , whereas it has a conventional bandwidth of 30%, and has a wideband frequency characteristic. It is clear that the resonance frequency bandwidth can be easily changed by changing the length direction length d of the sub-slot.

[0013]

According to the present invention, since the sub-slots whose length can be adjusted in the longitudinal direction are arranged in series through the slots and the sub-conducting flow paths, the bandwidth of the resonance frequency can be increased by the flow of the conducting currents having different path lengths. Can be varied, which effectively reduces the input impedance of the antenna and contributes to good matching with the feed line.

Further, since a characteristic of covering a wide band can be obtained in order to have two resonance frequencies, it is not necessary to use a plurality of antennas, which eventually contributes to miniaturization of the antenna itself.

[Brief description of drawings]

FIG. 1 is an external perspective view showing an embodiment of a slot antenna of the present invention.

FIG. 2 is a perspective transparent view of a different embodiment of FIG.

FIG. 3 is an explanatory diagram of power supply flow paths to the outer circumferences of main and sub slots.

FIG. 4 is a graph showing the characteristics of the standing frequency ratio of the used frequency versus the voltage.

[Explanation of symbols]

 1 Conductive Plate (Grounding Plate) 2 Feed Line 2-1 Signal Conductor 3 Main Slot 4 Sub Slot 5 Sub Conductive Flow Path 10 Dielectric

Claims (1)

Claim: What is claimed is: 1. A conductor layer covering an exposed surface of a dielectric substrate is used as a signal conductor or a ground conductor, and a slot is formed on the side of the ground conductor or in the region of the conductor plate. In a slot antenna formed by intersecting a feed line with the longitudinal direction directly or at a space, a longitudinal direction with a sub-conductive flow path branching from a main conductive flow path separated from the main conductive flow path at each longitudinal end of the slot antenna. A flat plate type slot antenna characterized in that sub-slots whose length can be adjusted are arranged in series so as to be directly or electromagnetically coupled to a feed line intersecting with the main slot.