Source: http://patents.com/us-5627551.html
Timestamp: 2018-06-25 02:48:40
Document Index: 64588697

Matched Legal Cases: ['art 11', 'art 11', 'art 11', 'art 11', 'art 11', 'art 11', 'art 11']

US Patent # 5,627,551. Antennas for surface mounting and method of adjusting frequency thereof - Patents.com
United States Patent 5,627,551
Tsuru , et al. May 6, 1997
Antennas for surface mounting and method of adjusting frequency thereof
An antenna adapted for surface mounting has a dielectric substrate on which are attached at least one primary grounding electrode and a connector electrode which together serve as a capacitor, at least one secondary grounding electrode formed adjacent to but insulated from the connector electrode, and a radiative member disposed thereover for emitting electromagnetic radiation. The resonant frequency of this antenna can be adjusted by trimming either its connector electrode or one of the secondary grounding electrode.
Inventors: Tsuru; Teruhisa (Kyoto, JP), Oida; Toshifumi (Kyoto, JP)
Appl. No.: 08/501,459
Aug 05, 1994 [JP] 6-184934
Current U.S. Class: 343/700MS ; 343/702; 343/846; 343/849
Field of Search: 343/7MS,702,829,846,849
5307556 May 1994 Kido
5510802 April 1996 Tsuru et al.
0621653 Apr., 1993 EP
61-210707 Mar., 1985 JP
1. An antenna for surface mounting, comprising:
a dielectric substrate having a top surface, a bottom surface and side surfaces therebetween;
at least one primary grounding electrode on said dielectric substrate;
a connector electrode on said dielectric substrate, said primary grounding electrode and said connector electrode together serving as a capacitor;
at least one secondary grounding electrode formed adjacent to but insulated from said connector electrode, said secondary grounding electrode and said connector electrode together serving as a second capacitor for adjusting the resonance frequency of said antenna; and
a radiative member disposed on said dielectric substrate, said radiative member having a principal surface, a first holder and a second holder, said first and second holders extending from said principal surface and supporting said dielectric substrate therebetween, said first holder having a power feed electrode and a grounding terminal formed at one end thereof, and said second holder being connected to said connector electrode on said dielectric substrate.
2. The antenna of claim 1 wherein said connector electrode is formed on at least one of said side surfaces of said dielectric substrate.
This invention relates to surface-mountable antennas usable in mobile communication apparatus and a method of adjusting the resonant frequency of such an antenna.
It is therefore an object of this invention in view of the above to provide an antenna which can be surface-mounted easily, for example, to a printed circuit board.
As shown in FIGS. 1 and 2, a surface-mountable antenna 22, serving as an example embodying the present invention, may be characterized as comprising a substantially rectangular dielectric substrate 2 and a radiative member 3 fastened to side surfaces of the dielectric substrate 2 so as to leave a space 2athereabove. The dielectric substrate 2 is formed by piling in layers a plurality of dielectric sheets made of a ceramic or resin material, having primary grounding electrodes 4a and 4b formed on side surfaces along its longer sides, connector electrodes 5a and 5b formed on side surfaces along its shorter sides, and secondary grounding electrodes 21a and 21b on opposite sides of, and insulated from, the connector electrode 5a on one of the side surfaces of the dielectric substrate 2. Inside the dielectric substrate 2, a planar conductor pattern 6 (referred to as the capacitor pattern) connected to the connector electrode 5a is formed nearer its upper surface and another planar conductor pattern 7 (referred to as the grounding pattern) connected to the primary and secondary grounding electrodes 4a, 4b, 21a and 21b is formed nearer its lower surface and parallel to the capacitor pattern 6 such that a capacitor C.sub.1 is formed between the capacitor and grounding patterns 6 and 7 and another capacitor C.sub.2 between the connector electrode 5a and the secondary grounding electrodes 21a and 21b. The radiative member 3 is made of a material with low conductor loss such as copper or a copper alloy and has a radiative part 11 having a rectangular planar shape and a pair of holders 12 and 13 formed by folding pieces protruding from the shorter sides of the radiative part 11 downward so as to be facing each other (as shown in FIG. 2). A power feed terminal 14 and a grounding terminal 15 are formed on the tip of the holder 12. Spacers 16-19 are also formed by bending small pieces protruding from the shorter sides of the radiative part 11 downward on both sides of the holders 12 and 13. The surface-mountable antenna 22 is formed by inserting the dielectric substrate 2 into the radiative member 3 such that the dielectric substrate 2 is sandwiched between the holders 12 and 13 and the spacers 16-19 touch the upper surface of the dielectric substrate 2 to make certain that a space 2a with a specified height is left between the lower surface of the radiative part 11 and the upper surface of the dielectric substrate 2. Thereafter, the connector electrodes 5a and 5b of the dielectric substrate 2 are soldered respectively to the holders 13 and 12 of the radiative member 3 to complete the antenna 22. The holder 13 is formed with a thin tip section so as to contact only a central portion of the connector electrode 5a, as shown in FIG. 1. Such an antenna 22 is adapted to be surface-mounted to a printed circuit board (not shown) having a wiring pattern thereon by soldering the power feed terminal 14 and the grounding terminals 4a and 4b to the wiring pattern.
The surface-mountable antenna 22, thus structured, has distributed capacitance C.sub.2 formed between the connector electrode 5a and each of the secondary grounding electrodes 21a and 21b between which it is sandwiched. Its equivalent circuit diagram, therefore, includes distributed capacitance C.sub.2 connected in parallel with the capacitor C.sub.1, as shown in FIG. 3. This parallel connection (of C.sub.1 and C.sub.2) is connected in series with distributed inductance L.sub.1 of the radiative part 11, and this series connection is connected in parallel with distributed inductance L.sub.2 between the power feed terminal 14 and the grounding terminal 15 of the radiative member 3. Thus, the resonant frequency f.sub.0 of this antenna 22 is expressed by:
The resonant frequency f.sub.0 of the antenna 22 can be adjusted by trimming the connector electrode 5a or the grounding electrode 21.sub.a or 21b to vary the distributed capacitance C.sub.2.
Another advantage of the antenna 22 is that, since it has both distributed inductance L.sub.1 of the radiative part 11 of the member 3 and distributed inductance L.sub.2 between the power feed terminal 14 and the grounding terminal 15, it is possible to change the distance between the power feed and grounding terminals 14 and 15 to change the distributed inductance L.sub.2 to thereby adjust the ratio between L.sub.1 and L.sub.2. The impedance of the antenna 22 can thus be changed and matched to the impedance of an external circuit. Since a metallic material is used for the radiative part 11 for radiating electromagnetic waves, the resistance of the antenna 22 is reduced and its thermal capacity is increased. This reduces its Joule heat and the gain is increased.
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