JPH11243318A - Antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna structure which is suitable especially for a mobile station operating in two frequency ranges. SOLUTION: This antenna contains a dielectric plate 21 as a supporting component and also as a component that decides an electrical characteristic. A zigzag radiation element 22 exists on one surface of the plate 21 and a flat radiation element 23 exists on the opposite side surface of the plate 21. The operation in two frequency ranges is performed based on the fact that its structure has two resonance frequencies which are comparatively separated from each other. Since its strip has comparatively broad width, the antenna sufficiently operates at various positions and in the neighborhood of an object. Its parasitic element can further has a gap operating as another radiator and the antenna operates in three frequency ranges in this case. The antenna is flat and can accordingly be fixed to the back wall of a mobile station so that its distance to the head of a user may be relatively long.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an antenna structure as defined in the preamble of claim 1 and more particularly to an antenna structure which can be used for a mobile station operating in two frequency ranges.

[0002]

BACKGROUND OF THE INVENTION The development of mobile station technology has, and will continue to, introduce new, multifunctional models to the market. In that model, new requirements are placed on the antenna. That is, the antenna must operate in two frequency ranges, for example, 900 MHz and 1.8 GHz. Bandwidth must be relatively large. Radiation and reception characteristics must be relatively good regardless of whether the device and the antenna are in different orientations and at different locations with respect to external objects. Also, the antenna must be relatively small and compact.

FIG. 6 shows a conventionally known antenna structure operating in two frequency ranges.

1) Structure based on a helix: Double helix: Two helical elements 101 and 102 having different resonance frequencies are placed sandwiching each other or on top of each other. The elements have a common or separate feed.

Helical and monopolar: helical element 10
Within 3 are located rod elements 104 having different resonance frequencies. These elements have a common or separate feed.

The disadvantages of the structure based on the helical element are the relatively high production costs and the apparently poor properties when the antenna is placed on or near the frame of the device. is there.

2) Microstrip structure-Double strip: A radiating strip 105 is on the surface of the dielectric plate, and another strip 106 having a different resonance frequency is included therein. Feeding is performed, for example, to strip 105, and strip 106 is parasitic. The ground plane 107 is on the other side 108 of the plate.

[0008] strips and transmission lines: dielectric plate 1
On the surface of 11 is a strip 109 and a strip 110 acting as part of the short-circuit transmission line. The transmission line is dimensioned to radiate at one of the two desired frequencies.

A disadvantage of the above and other corresponding microstrip structures is that their bandwidth is relatively narrow. Although improvements can be obtained by adding parasitic elements to the structure, the disadvantage is that the size of the structure is large.

3) Chip structure Within the dielectric monolithic body 114 there are two meandering conductors 112 and 113 which radiate at different frequencies. The disadvantage of these structures is that the bandwidth is relatively narrow.

In addition to the structure described above, there is a double-band antenna based on a half-wave dipole. The disadvantage is that the size is relatively large.

[0012]

It is an object of the present invention to mitigate the above disadvantages associated with the prior art. The antenna according to the invention is characterized by what is stated in the independent claims. Some preferred embodiments of the invention are set out in the dependent claims.

[0013]

The basic idea of the present invention is as follows. That is, there is a conductor pattern that repeats regularly or almost regularly on one side of a small dielectric plate such as a printed circuit board, one end of which is connected to a receiving conductor and an antenna feed. On the other side of or in the plate there is a parasitically coupled conduction region, which is formed in such a way that the structure has two resonant frequencies which are relatively separated from each other.

An advantage of the present invention is that the bandwidth of each operating range is wider than that of previously known structures. This is important, especially when the device is used in various locations, and especially when the passband shifts slightly due to misalignment. Another advantage of the present invention is that when the antenna is short and flat, it can be rotated to a protective position close to the device frame and the distance from the device frame can be kept relatively large, so that That is, the electrical characteristics are sufficiently maintained. Another advantage of the present invention is that the flat shape of the antenna allows it to be placed on the back wall of the mobile phone, which minimizes the power absorbed (SAR) in the user's head. It is. Another advantage of the present invention is that the cost of the antenna is relatively low due to its simple structure.

Next, the present invention will be described in detail. In the description, reference is made to the accompanying drawings.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of FIG. 6 has already been described in relation to the description of the prior art. FIG. 1 shows the structure of the invention, comprising a dielectric plate 21 and a radiating element 22 connected to a feed line 25 of the antenna.
And a parasitic element 23 for radiation.
In this example, the dielectric plate is a dielectric layer of a printed circuit board. The element 22 is a meandering rectangular conductor pattern, which is formed on the other side of the plate 21 by, for example, etching. In this connection, the term serpentine means a line without branches, in which a basic form or a modification thereof, or various basic forms, repeats in the same direction in order. An example of a winding pattern is shown in FIG. In the following description, the element 22 will be referred to as a winding element. The term parasitic element means a conductor that is insulated with respect to DC current from other conductors of the system, but is electromagnetically coupled to the other conductors. In this example, the parasitic element 23 is a conductor region formed by etching on the surface opposite the winding element, which is electromagnetically coupled to the winding element. The symbols affecting the properties of the antenna are also entered in FIG. 1: the thickness d of the dielectric layer, the height h of the meandering element 22,
The width w of the meandering element, the height s of the repeating pattern of the meandering element, the width w1 of the conductor of the meandering element, the height hp of the parasitic element 23, the width wp of the parasitic element, and the difference e1 + e2 between the heights of the meandering element and the parasitic element. Of which e1 is at the top of the structure and e2 is at the bottom. The term height direction means the direction of the largest dimension h of the meandering element in the description here and in particular in the claims.

The structure of FIG. 1 has two resonance frequencies, the lower one being mainly determined by the serpentine element 22 and the higher one being determined by the parasitic element 23. Naturally, the elements interact with each other and thus affect both resonance frequencies. The structure is
It is characterized in that the resonance frequencies are relatively far apart, one of which can be set to a frequency used by, for example, a GSM network and the other to a frequency used by a PCN network or a satellite telephone. The structure is particularly characterized by a relatively large bandwidth in both the upper and lower operating ranges. A flat parasitic element creates a wide upper band and acts to widen the lower band. The bandwidth can be adjusted by sizing. For example, when it is desirable that the upper band is as wide as possible, the parasitic element must be dimensioned as wide, and it must be placed downward so that the dimension e1 becomes relatively large.
Enlarge the space of the meandering pattern or measure the size
By increasing the heights h and hp of the radiating elements at the same time, without changing the resonance frequency,
A wider bandwidth can also be obtained. Therefore, a compromise between bandwidth and antenna size must be made. The characteristics of the antenna are affected by the dimensions of the antenna as well as by the material between the serpentine and parasitic elements: the higher the dielectric constant of the dielectric plate, the lower the upper resonance frequency.

The band characteristics of an antenna are often investigated by measuring its return loss Ar as a function of frequency. The term return loss refers to the ratio of the energy supplied to the antenna to the energy returned from it. It is the absolute value of the reciprocal of the square of the reflection coefficient, that is, the parameter S11. The greater the return loss, the greater the portion of the energy supplied to the antenna is radiated into the environment, ie the better the antenna works. In an ideal case, the return loss is infinite. When the return loss is 1, or 0 dB, the antenna does not radiate at all and all the energy supplied to it returns to the source. The reception characteristics of an antenna follow the transmission characteristics: the more efficiently the antenna transmits at a certain frequency and in a certain direction, the more efficiently the antenna receives from said direction at said frequency. The bandwidth of an antenna can be determined in various ways: it can mean the difference between frequencies where the return loss is reduced by 3 dB from its best or maximum value. Also, the bandwidth can be regarded as the difference between the frequencies at which the return loss is 10 dB or 10.
This corresponds to a value of 2 for the standing wave ratio SWR.

FIG. 2 shows examples of changes in the return loss Ar of the antenna of the present invention in various operating states as a function of frequency. The measurement results were obtained with antennas of the following dimensions: h = 29.3 mm; w =
5.4 mm; hp = 24.4 mm; wp = 5.4 mm;
e1 = 4.2 mm; e2 = 0 mm; s = 1.6 mm; w
1 = 0.5 mm; and d = 0.76 mm. The permittivity of the printed circuit board is εr = 2.5. The measurement range of FIG.
It is from 0 MHz to 2.2 GHz. The thin solid curve 31 corresponds to the situation in FIG. 3 (a): the antenna 61 is out and facing upwards, and there are no other objects near it. The thick solid curve 32 corresponds to the state of FIG. 3B: the human head 71 is adjacent to the mobile station 81. The dotted line 33 corresponds to the state shown in FIG. 3 (c): the antenna 61 is outside, but is in an inclined position like a multifunctional mobile station in normal operation. Dot and dash line 34
Corresponds to the state of FIG. 3D: the antenna 61 is turned to a protection position such as adjacent to the frame of the mobile station 81. Next, the band limit is that the return loss is 8 dB = 6.3 (SWR =
2.3) and a bandwidth of -3d
Determined based on point B. The curve 31 has a lower range of about 900 to 900 when the mobile station is in free space.
975MHz, upper range is about 1670-1940MH
z. The curve 32 indicates that the lower range is about 880 to 975 MHz and the upper range is about 1630 to 1920 MHz in a normal call state. The curve 33 has a lower range of approximately 885 to 975 MHz and an upper range of approximately 1690 to 975 MHz in the operating posture of the multifunctional mobile station.
2100 MHz. Curve 34
Means that the lower range is about 84 when the antenna is turned.
The upper range is about 1625 to 1890M at 5 to 955 MHz.
Hz. It can be seen that the location and width of those ranges depends on the attitude and environment of the antenna, but in all cases they encompass the ranges used by GSM and PCN networks. When the antenna is in the turned position, the average return loss in the pass band is 10 dB lower than that in the normal position.
As small. In this case, the transmission power is of course small, but still sufficient in most cases.

The antenna structure and its characteristics of the present invention have been described above. The invention is not limited to the above solution. For example, the number and shape of the radiating elements may vary. FIG. 4 shows examples of possible variations. In FIG. 4 (a), the meandering element 22 is made up of straight sections as in FIG. 1, but the angle between the conductor sections is different from a flat angle (parallel). Further, the width of the pattern increases in the downward direction. In FIG. 4 (b), the meandering elements 22 consist of straight sections, but they form a triangular wave pattern. In this example, the parasitic elements are oval rather than rectangular. FIG.
In (c), the meandering element 22 comprises an arc and a straight line. A gap 51 is formed in the parasitic element, where it radiates in a third frequency range. Such an antenna can be dimensioned to operate in the frequency range used by the three systems. With the same intent, FIG. 4 (d) has a second parasitic element 52 on the same side of the printed circuit board as the feed conductor or serpentine element. The material of the dielectric plate may also vary: in addition to the materials commonly used for printed circuit boards, it may be, for example, polytetrafluoroethylene (PTFE) or other plastic. The radiating element can also be formed on the surface of the dielectric plate by any method other than etching, for example by vapor deposition or by tooling the conductor surface of a printed circuit board: for example by vapor deposition or screen printing on the surface of the plate. Conductive material can be applied.

FIG. 5 is a block diagram of a digital mobile communication means according to a preferred embodiment of the present invention. The mobile communication means includes a microphone 301, a keyboard 307, a display 306, a receiver (earphone) 314,
It has an antenna duplexer or switch 308 and a control unit 305, all of which are typical components of conventional mobile communication means. Further, the mobile communication means includes a typical transmitting block 304 and a receiving block 311. Transmit block 304 includes the necessary functions for voice and channel coding, encryption, and modulation, and the required RF circuitry to amplify the signal for transmission. The receiving block 311 includes a required amplification circuit and functions necessary for demodulating and decrypting a signal and removing a channel and voice coding. The signal produced by microphone 301 is
The signal is amplified by an amplification stage 302 and converted into a digital form by an A / D converter 303.
04. The transmission block encodes the digital signal to produce a modulated and amplified RF signal,
The RF signal is then transmitted to a duplexer or switch 3
08 to the antenna 309. A receiving block 311 demodulates the received signal and removes encryption and channel coding. The resulting audio signal is converted to analog form by a D / A converter 312, and the output signal is amplified by an amplifier stage 313, after which the amplified signal is sent to an earpiece 314. The control unit 305 controls the function of the mobile communication means,
07, read the command given by the user via
A message is displayed to the user via the display 307. The mobile communication means further has an antenna structure 309. The antenna structure 309 preferably has a structure corresponding to any of the above-described antenna structures of the present invention or an equivalent antenna structure.

From the above description, it will be apparent to those skilled in the art that various modifications may be made within the scope of the present invention. Although the preferred embodiment of the invention has been described in detail, it is evident that many modifications and variations are possible, all of which fall within the scope of the invention.

[0023]

According to the present invention, the disadvantages of the conventionally known spiral-based antenna structure are that the manufacturing cost is high,
Further, it is possible to reduce disadvantages such as deterioration of characteristics when the antenna is placed on the frame of the device or when the antenna is pointed near the frame.

Further, it is possible to reduce the drawbacks of the conventionally known microstrip structure, such as a narrow bandwidth and a large structure size.

Further, it is possible to reduce the drawbacks of the conventionally known chip structures, such as a narrow bandwidth and a relatively large size.

[Brief description of the drawings]

FIG. 1 shows a representative antenna of the present invention.

FIG. 2 shows the band characteristics of the antenna of the present invention.

FIG. 3 shows an antenna mounted in a mobile station in various states.

FIG. 4 shows some variations of the antenna of the present invention.

FIG. 5 shows a mobile communication means of the present invention.

FIG. 6 shows a prior art dual band antenna.

[Explanation of symbols]

 Reference Signs List 21 dielectric plate 22 meandering element 23 parasitic element

Claims (9)

[Claims] A first element (22) connected to a feed line and at least one parasitic element (2).
3) the antenna comprising:-the first element (22) is a serpentine element;-the parasitic element (23) is a flat conductor region;-the serpentine element (22) and the parasitic element. The support structure for (23) is a dielectric plate (21)
Antenna. 2. The structure according to claim 1, wherein the width (w) of the serpentine element at a first point in the height direction is different from the width at a second point in the height direction. 3. The height (h) of the parasitic element (23).
p) is the height (h) of the meandering element (22)
2. The structure of claim 1 that is smaller. 4. The structure according to claim 1, wherein the width (wp) of the parasitic element at a first point in the height direction is different from the width at a second point in the height direction. 5. The structure according to claim 1, wherein said dielectric plate is a dielectric part of a printed circuit board. 6. The meandering element (22) is a conductor area on a first surface of the printed circuit board, and the parasitic element (23) is a conductor area on a second, opposing surface of the printed circuit board. 6. The structure according to claim 5, which is an area. 7. The structure according to claim 1, wherein the parasitic element has a radiation gap. And a second parasitic element (52) having a first parasitic element and a second parasitic element (52).
2. The structure according to claim 1, wherein 2) is a conductor region on the same side of the dielectric plate as the parasitic element. 9. A mobile station having an antenna structure consisting of a feed line, a first element (22) connected to the feed line, and at least one parasitic element (23):-the first element; (22) a serpentine element;-the parasitic element (23) is a flat conductor region;-the antenna structure comprises a serpentine element (2).
Mobile station further comprising 2) and a support structure (21) for said parasitic element (23), said support structure being a dielectric plate.