ANTENNA FOR PORTABLE WIRELESS COMMUNICATIONS SYSTEM AND A METHOD FOR MANUFACTURING THE SAME

Abstract: A method for manufacturing an antenna for a wireless communications system includes the steps of assembling and soldering a spring to a metal rod, insert molding a pipe and assembling the pipe with a bobbin by inserting the bobbin into the pipe, and assembling a "+" cutting under the metal rod and NI-TI wire, so that in the antenna according to the present invention, the return loss of an antenna is reduced by improving spring structure of the helical antenna part, so that the bandwidth coverage may be enlarged to maintain high communication quality and the assembling procedures may be simplified.

Description: ANTENNA FOR PORTABLE WIRELESS COMMUNICATIONS SYSTEM AND A METHOD FOR MANUFACTURING THE SAME TECHNICAL FIELD The present invention relates to a portable wireless communications system, and more particularly to, an antenna for a portable wireless communications system in which spring structure of a helical antenna is improved to make bandwidth coverage enlarged and assembling procedure simplified. BACKGROUND ART In general, wireless communications systems adopt an antenna for performing radio communications, wherein through the antenna a high frequency signal which is output from a modulation part of the wireless communication system is transmitted and radio frequency transmitted by other wireless communication systems is received by the antenna. In order to improve the transmitting and receiving characteristics of an antenna, it is necessary to match impedance of the antenna and impedance of the transmitter and/or receiver in accordance with transmitting and/or receiving frequency, thereby reducing loss due to unnecessary emission. Such an antenna is integral in it structure, so that it functions as a helical antenna when retracted and functions as a rod antenna when extracted. The antenna accommodates a spring in a lower part thereof to maintain a good receiving state. Fig. 1 is a schematic view showing a construction of a general wireless communications system, wherein the wireless communications system includes a main body part 10 and an antenna part 20. The antenna part 20 includes a handle 21 to use when extracting or retracting the antenna part 20, an insulation part 22, an helical antenna 23 which is coupled to the main body 10 and accommodating a spring 25, so as to operate when the antenna part 20 is retracted, and a rod antenna 24 which is coupled to the helical antenna 23, so as to operate when the antenna part 20 is extracted. Fig. 2 is a schematic view showing the spring 25, which is accommodated in the helical antenna 23, and a metal rod 26, which is to be coupled to the spring 25, wherein the metal rod 26 is inserted in the spring 25 by 1 turn and fixed together by closing the coupled spring part. Furthermore, since the conventional antenna as constructed above has reflection loss of 7.5dB and narrow bandwidth coverage, it has a disadvantage that the communications quality is apt to be influenced when users touch it or movement occurs in communication frequency. The conventional antenna has still another problem that mismatching is apt to occur since impedance is of 23.0, less than a set reference specification of 50_2. Since the standing wave ratio is of 2.3, which is larger than a reference value of 1, power reflection is high about 15.5% so that loss of power becomes increased. DISCLOSURE OF INVENTION Therefore, the present invention is derived to resolve the disadvantages of the conventional techniques and it is an object of the present invention to provide an antenna for portable wireless communications system, in which a spring which is installed in a helical antenna is improved, so that return loss becomes small and bandwidth coverage becomes wider, thereby communications quality is less influenced even when it is touched by the user and/or movement occurs in the communication frequency. In order to achieve the above object of the present invention, it is derived that an antenna for portable wireless communications system characterized in that a spring, which is installed in a helical antenna, is a plate spring having a predetermined thickness . BRIEF DESCRIPTION OF DRAWINGS The present invention will become more fully understood from the detailed description given hereinafter accompanying drawings, which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: Fig. 1 is a schematic view showing a conventional antenna for wireless communications systems; Fig. 2 is a schematic cross-sectional view showing the construction of a spring of Fig. 1; Fig. 3 is a disassembled view showing an antenna for wireless communications systems according to an embodiment of the present invention; Fig. 4 is an assembled view showing the antenna of Fig. 3; Fig. 5 is a perspective view showing the antenna of Fig. 3; Fig. 6A to Fig. 6F are views for explaining assembling procedure of the antenna according to the present invention; Fig. 7 to Fig. 10 show a first test result of the antenna according to the present invention, wherein Fig. 7 is a graph showing return loss characteristics, Fig. 8 is a Smith chart, Fig. 9 is a graph for comparing standing wave ratio characteristics, and Fig. 10 is a view showing emission patterns at 900MHz; Fig. 11 to Fig. 15 show a second test result of the antenna according to the present invention, wherein Fig. 11 is a graph showing return loss characteristics, Fig. 12 is a Smith chart, Fig. 13 is a graph for comparing standing wave ratio characteristics, Fig. 14 is a view showing emission patterns at 836MHz, and Fig. 15 is a view showing emission patterns at 88lMHz; Fig. 16 to Fig. 20 show a third test result of the antenna according to the present invention, wherein Fig. 16 is a graph showing return loss characteristics, Fig. 17 is a Smith chart, Fig. 18 is a graph for comparing standing wave ratio characteristics, Fig. 19 is a view showing emission patterns at 836MHz, and Fig. 20 is a view showing emission patterns at 88lMHz; Fig. 21 to Fig. 25 show a fourth test result of the antenna according to the present invention, wherein Fig. 21 is a graph showing return loss characteristics, Fig. 22 is a Smith chart, Fig. 23 is a graph for comparing standing wave ratio characteristics, Fig. 24 is a view showing emission patterns at 836MHz, and Fig. 25 is a view showing emission patterns at 88lMHz; and Fig. 26 to Fig. 30 show a fifth test result of the antenna according to the present invention, wherein Fig. 26 is a graph showing return loss characteristics, Fig.27 is a Smith chart, Fig. 28 is a graph for comparing standing wave ratio characteristics, Fig. 29 is a view showing emission patterns at 836MHz, and Fig. 30 is a view showing emission patterns at 88lMHz. BEST MODE FOR CARRYING OUT THE INVENTION An antenna for a portable wireless communications system and a method for manufacturing the same, according to preferred embodiments of the present invention will now be explained with reference to the accompanying drawings. Fig. 3 is a disassembled view showing parts and accessories of an antenna for wireless communications systems according to an embodiment of the present invention. In Fig. 3, a bobbin 31 is positioned under a top 30 and a pipe 32, which is formed by insert molding, is positioned under rhe bobbin 31. A rolled spring 33 which has a thickness of Φ0.7 and is fixed on a metal rod 34, is coupled under the pipe 32 and a "+" cutting 35 is positioned under the metal rod 34, followed by a stopper 37 via a Ni-Ti wire 36. Fig. 4 is an assembled view showing the antenna of Fig. 3. A rod antenna part and a helical antenna part are respectively fixed on a main body of a cellular phone, wherein the rod antenna part includes a knob 30 and the Ni-Ti wire 36, and the helical antenna part includes the bobbin 31 which is inserted into the pipe 32, the spring 33, the metal rod 34, the "+" cutting 35 and the stopper 37. Fig. 5 is a perspective view of the antenna of Fig. 3, which shows coupling of the spring 30 to the metal rod 34. The spring 30 is rolled and has a thickness of Φ θ . 7 . Now, the operation of the antenna constructed as above will be described in detail. Fig. 6A to Fig. 6F are views for explaining assembling procedure of the antenna according to the present invention. The spring 33 is coupled with the metal rod 34 as shown in Fig. 6A and soldered as shown in Fig. 6B. The pipe 32 is insert-molded covering the spring 33, which is fixed on the metal rod 34, as shown in Fig. 6C, and the bobbin 31 is inserted into the pipe 32, as shown in Fig. 6D. In this state, the "+" cutting 35 is assembled under the metal rod 34 and then the Ni-Ti wire 36 is coupled under the Ni-Ti wire 36, thereby finishing the assembling of the antenna according to the present invention. Fig. 7 to Fig. 10 show a first test result of the antenna according to the present invention. Fig.7 is a graph showing return loss characteristics at 900MHz, wherein a represents a return loss characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 8 is a Smith chart at 900MHz, wherein a represents impedance of prior art, and b represents that of the antenna according to the present invention. Fig. 9 is a graph for comparing standing wave ratio characteristics at 900MHz, wherein a represents standing wave ratio characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 10 is a view showing emission patterns at 900MHz, wherein the test was performed for the helical antenna part with a network transmission ratio at 3m distance, a representing emission pattern of prior art, and b representing that of the antenna according to the present invention. Fig. 11 to Fig. 15 show a second test result of the antenna according to the present invention, wherein the test was performed in the state that the antenna is installed in a cellular phone and is inserted into a main body of the cellular phone, which is not grasped by a user. Fig. 11 is a graph showing return loss characteristics at 849MHz, a represents a return loss characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 12 is a graph for comparing standing wave ratio characteristics at 849MHz, wherein a represents standing wave ratio characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 13 is a Smith chart at 849MHz, wherein a represents impedance of prior art, and b represents that of the antenna according to the present invention. Fig. 14 is a view showing emission patterns at 836MHz, wherein the test was performed in the state that the antenna is installed in a cellular phone and is inserted into a main body of the cellular phone, which is not grasped by a user. In Fig. 14, a represents emission pattern of prior art, which indicates -39.46dB at an angle 48.00 and b represents that of the antenna according to the present invention, which indicates -39.42dB at an angle 50.00. Fig. 15 is a view showing emission patterns at 88lMHz, wherein the test was performed in the state that the antenna is installed in a cellular phone and is inserted into a main body of the cellular phone, which is not grasped by a user. In Fig. 15, a represents emission pattern of prior art and b represents that of the antenna according to the present invention, which indicates -41.76dB at an angle 30.00. Fig. 16 to Fig. 20 show a third test result of the antenna according to the present invention, wherein the test was performed in the state that the antenna is installed in the cellular phone and the rod antenna part is drawn out of the main body of the cellular phone . Fig. 16 is a graph showing return loss characteristics at 849MHz, wherein the test was performed in the state that a user holds the cellular phone, perpendicularly to the ground at a 30cm high from the ground. In Fig. 16, a represents a return loss characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 17 is a Smith chart at 849MHz, wherein a represents impedance of prior arc, and b represents that of the antenna according to the present invention. Fig. 18 is a graph for comparing standing wave ratio characteristics at 849MHz, wherein a represents standing wave ratio characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 19 is a view showing emission patterns at 836MHz, wherein the test was performed in the state that the cellular phone is not grasped by the user and the rod antenna part is drawn out of the cellular phone . In Fig. 19, a represents emission pattern of prior art, which indicates -39.17dB at an angle 45.00 and b represents that of the antenna according to the present invention, which indicates -38.87dB at an angle 42.00. Fig. 20 is a view showing emission patterns at 88lMHz, wherein the test was performed in the state that the cellular phone is not grasped by the user and the rod antenna part is drawn out of the cellular phone . In Fig.20, a represents emission pattern of prior art, which indicates -41.01dB at an angle 24.14 and b represents that of the antenna according to the present invention, which indicates -41.03dB at an angle 22.00. Fig. 21 to Fig. 25 show a fourth test result of the antenna according to the present invention, wherein the test was performed in the same condition as the third test except that a user holds the cellular phone to his right ear. At this time, the rod antenna is inserted in the cellular phone. Fig. 21 is a graph showing return loss characteristics at 849MHz, wherein a represents a return loss characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 22 is a Smith chart at 849MHz, wherein a represents impedance of prior art, and b represents that of the antenna according to the present invention. Fig. 23 is a graph for comparing standing wave ratio characteristics at 849MHz, wherein a represents standing wave ratio characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 24 is a view showing emission patterns at 836MHz, wherein the test was performed in the state that a user holds the cellular phone, which is inserted with the antenna, to his ear. In Fig. 24, a represents emission pattern of prior art, which indicates -49.35dB at an angle 45.06 and b represents that of the antenna according to the present invention, which indicates -49.22dB at an angle 47.00. Fig. 25 is a view showing emission patterns at 881MHz,. wherein the test was performed in the state that a user holds the cellular phone, which is inserted with the antenna, to his ear. In Fig. 25, a represents emission pattern of prior art, which indicates -46.61dB at an angle 68.00 and b represents that of the antenna according to the present invention, which indicates -46.49dB at an angle 67.00. Fig. 26 to Fig. 30 show a fifth test result of the antenna according to the present invention, wherein the test was performed in the same condition as the fourth test except that the rod antenna is drawn out from the main body of the cellular phone. Fig. 26 is a graph showing return loss characteristics at 849MHz, wherein a represents a return loss characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 27 is a Smith chart at 849MHz, wherein a represents impedance of prior art, and b represents that of the antenna according to the present invention. Fig. 28 is a graph for comparing standing wave ratio characteristics at 849MHz, wherein a represents standing wave ratio characteristic of prior art, and b represents that of the antenna according to the present invention. Fig. 29 is a view showing emission patterns at 836MHz, wherein the test was performed in the state that a user holds the cellular phone, from which the rod antenna is drawn out, to his ear. In Fig.29, a represents emission pattern of prior art, which indicates -47.18dB at an angle 60.00 and b represents that of the antenna according to the present invention, which indicates -47.12dB at an angle 61.00. Fig. 30 is a view showing emission patterns at 88lMHz, wherein the test was performed in the state that a user holds the cellular phone, from which the rod antenna is drawn out, to his ear. In Fig.30, a represents emission pattern of prior art , which indicates -44.24dB at an angle 79.00 and b represents that of the antenna according to the present invention, which indicates -44.23dB at an angle 77.00. INDUSTRIAL APPLICABILITY As described hereinabove, according to the present invention, the return loss of an antenna is reduced by making the spring with a steel wire having a predetermined width to improve spring structure, so that the bandwidth coverage may be enlarged to maintain high communication quality even in case of human touch and/or frequency movement during communications.

Claims: CLAIMS 1. An antenna for a portable wireless communications system which is operating as a helical antenna in case of retraction and as a rod antenna in case of extension by integrating the helical antenna and the rod antenna, characterized by that a spring is rolled into Φ O . l in thickness to be accommodated in the helical antenna . 2. A method for manufacturing an antenna characterized by comprising the steps of: a first step of assembling and soldering a spring to a metal rod, a second step of insert molding a pipe and assembling the pipe with a bobbin by inserting the bobbin into the pipe; and a third step of assembling a "+" cutting under the metal rod and NI-TI wire.

Inventors: CHANG EUNG-SOON, CHANG, EUNG-SOON
Applicants: CHANG EUNG SOON, CHANG, EUNG-SOON
Application year: 1999
Main classification: H01Q1
IPC codes: H01P11, H01Q1, H01Q3, H01Q9