CN1353877A - Patch antenna and communication device including such antenna - Google Patents

Abstract

The invention relates to an antenna (20; 80), comprising: a microstrip element (21; 83), a conductive substrate (22; 82) substantially parallel to said microstrip element, said microstrip element having at least one feeder (26; 89) for circular polarization, wherein said microstrip part has a first hole substantially centrally located in said microstrip part (21; 83), said conductive substrate has a The first hole is opposite to the corresponding second hole, and the antenna further includes a conductive wire (25; 85) connecting the perimeters of the first and second holes, thereby forming a through holes (24; 84), wherein the through holes (24; 84) are suitable for realizing at least one non-antenna function. A capacitive load may also be formed between the edge (21') of said microstrip member (21; 83) and said conductive substrate (22', 22; 82). The invention also relates to a communication device (30; 62) comprising an antenna (35; 61) as described above.

Description

Microstrip antenna and communication device comprising such antenna

Field of invention:

The invention relates to a patch antenna as claimed in the preamble of claim 1 . The invention also includes a communication device comprising such an antenna. The microstrip antenna according to the invention has substantial advantages for the integration of various products, in particular its use as a ceramic GPS antenna in mobile phones.

Background technique:

The utilization of GPS guidance systems and other related systems (Glonass, etc.) has been greatly enhanced and widely used over the past decade. Ceramic antennas are popular among antennas because of their small size and the inherent filtering necessary to protect GPS receivers.

GPS microstrip antennas can be mounted in many ways, a typical handheld GPS receiver has a flat upper surface with a display (showing maps, etc.), a keypad and a microstrip antenna that is usually pointed upwards or Slightly away from the user's face. The typical size of a flat surface of a handheld GPS is 60 ^* 150 mm, and the typical size of a microstrip antenna attached from its bottom is 25 ^* 25 mm.

A particular problem with microstrip antennas is their requirement to have a "ground plane," which is a substantially flat conductive surface. Ideally this surface should be larger, the smaller the surface the worse the performance of the antenna. For example, a 50 ^* 50 mm conductive substrate produces about 2 dB less gain for a GPS ceramic microstrip antenna than a better ground plane (large conductive substrate), and the smaller the surface of the conductive substrate, the The gain will be even lower.

For GPS systems, as well as any other satellite communication/reception system, the power headroom is usually only a few decibels, so very limited attenuation will also impair functionality. Note that there is another quadrifilar helical GPS antenna that does not require a conductive substrate, but rarely has a hand-fitting profile that retains its functionality.

Microstrip antennas typically have a narrow bandwidth, but US Patent 5,861,848 to Iwasaki describes an improved microstrip antenna that is tunable to receive two satellite communication frequencies. A ring-shaped microstrip antenna is one of the components of this antenna, and as in the cited prior art, the ring-shaped microstrip antenna is grounded through a circular grid wire. The applications cited relate only to the antennas themselves and to antennas in antenna arrays. There is no discussion to consider the installation of antennas in small devices like mobile phones.

Japanese patent application JP10247815 discloses the structure of an antenna having a microstrip antenna mounted on an insulating substrate and a ground wire mounted on the opposite side of said substrate. A vertical hole is formed in the central portion of the microstrip antenna, and the ground line and the microstrip antenna are short-circuited by a cylindrical conductor. A monopole antenna is mounted through the hole, thereby reducing interference between communication signals respectively generated by the microstrip antenna and the monopole antenna.

Invention content:

The object of the present invention is to provide a microstrip antenna whose shape will simplify its integration with a communication device, for example in a mobile phone, in which said microstrip antenna is provided with a device for placing such as a loudspeaker, A hole for a microphone or GPS amplifier.

According to the invention, this object is achieved by the features stated in the characterizing part of claim 1 .

This object is also achieved by the features stated in the characterizing part of claim 9 .

An advantage of the present invention is that the microstrip antenna can be combined with a device to integrate functions other than the antenna. In a device as small as a mobile phone it is almost impossible to combine a small conductive substrate of at least a properly designed microstrip for acceptable integration with the equipment necessary to perform the basic functions of said mobile phone.

The invention will be disclosed in more detail below by way of example with reference to the accompanying drawings.

Brief description of the drawings:

Figure 1a shows a perspective view of a microstrip antenna according to the present invention;

Fig. 1b is a diagonal sectional view along line A-A in Fig. 1;

Fig. 2 is the sectional view of another embodiment of microstrip antenna;

Figures 3a and 3b are schematic diagrams of a mobile cellular telephone with a microstrip antenna according to the present invention;

Figure 4 is a schematic diagram of a mobile phone antenna including a GPS antenna mounted on the top and including a GPS antenna according to the present invention;

Fig. 5 shows a kind of microstrip antenna filled with ceramics at a specific frequency, the relational graph of microstrip size and aperture;

Figure 6 shows a mobile phone with an integrated GPS antenna according to the invention;

Figures 7a and 7b show a microstrip antenna according to the invention mounted in said hole and having a low noise amplifier;

FIG. 8 shows another embodiment according to the invention as described in the embodiment of FIG. 2 .

Example details:

Figure 1a shows a perspective view of a typical microstrip antenna 10 according to the present invention, having a microstrip element 11 with a substantially square surface, the square's side length being λ/2. The surface area of a square at a frequency of 1575.42 MHz (GPS frequency for C/A code only) is 95 ^* 95 ^mm2 . The microstrip antenna also includes a conductive substrate 12 serving as a ground plane substantially parallel to the microstrip part, which is necessary for its functioning. Printed circuit boards, screen shields, car roofs, etc. can also be used as conductive substrates when they function as ground planes in relation to microstrip antennas.

Conductive substrates reduce antenna gain, a typical loss for this type of antenna in small devices. The space 13 between the microstrip part 11 and the conductive substrate 12 can be filled with ceramics (e.g. ε=10 or ε=36) or plastic, which will reduce the size of the microstrip to 25 ^* 25 mm or 19 ^* 19 mm respectively when filled with ceramics millimeters and only a few millimeters thick. The reduction in the physical size of the microstrip caused by the ceramic filling will seriously reduce the bandwidth, but the bandwidth may also be reduced to 2MH (plus frequency stability margin due to temperature, etc.) to maintain the simplest GPS (only C /A code) function.

The microstrip component 11 has a feeding 16 where the antenna together with the substrate serves as ground. The center and outer leads of the feeder 16 are connected to the substrate 12, usually by a coaxial cable. The thickness of the feeder wire varies with the thickness of the central conductor of the coaxial line, or the shape of the feeder wire can be improved to increase the degree of matching. The feeder is placed very close to the diagonal of the approximately square microstrip, and its distance from the central hole 14 ensures proper matching (50 ohms, etc.). The approximately square microstrip can be conceptually understood as two linearly polarized microstrips tuned to slightly different frequencies determined by the length of each side. This difference in frequency, determined by the length of each side, is of the order of one percent, or expressed in another different way, as an impedance bandwidth of the microstrip. This difference causes the currents in each of the notional microstrips to have a phase of approximately ±45 degrees, resulting in circularly polarized radiation. This is a common method for generating circular polarization, which can be called "self-polarization," but it is only applicable to very narrow bandwidths. The impedance bandwidth may be large while the polarization bandwidth is narrow. A typical ceramic microstrip antenna is made of metal-coated ceramic, and the microstrip in this antenna is slightly smaller than the microstrip in a ceramic antenna. In this case, the metallized outer layer is clearly much thinner than the microstrip shown in the figure.

As long as the size of the hole is kept below about 1/3 the size of the microstrip, the hole and conductive tube will not interfere with the half wave function. To illustrate this, the dimensions of the microstrips were calculated as a _function of the pore diameter with _Al2O3 as the dielectric.

The microstrip antenna 10 of the present invention is provided with a hole 14 in the middle thereof, and a conductive tube 15 short-circuiting the microstrip component 11 and the conductive substrate 12 is arranged therein, that is, the conductive tube 15 is connected with the microstrip component and the conductive substrate 12. The conductive substrates are in electrical contact. If the antenna is filled with a solid material, the conductive tube 15 can be made by metallizing the hole 14 . The conductive tube can also be made of a metal tube inserted into the hole, which connects the microstrip part and the conductive substrate 12 . In the latter case, there is no need to fill it with solid material, so as shown in FIG. 5, the space 13 between the microstrip antenna and the conductive substrate may have no filler but only air for a particular frequency. It can be seen that a small aperture has a small effect on the resonant frequency, which can be easily compensated for by slightly increasing the side length of the microstrip.

Obviously, holes with a wide range of apertures can be utilized by adjusting the side length of the microstrip while still keeping the size of the overall antenna constant, but if considering that the practical upper limit is 20% increase in the side length of the microstrip, then for a For 25 ^* 25mm microstrips the hole size should be kept below 10-11mm. The central hole may then have a wide range of diameters, for example between 0-40% of the side length of the approximately square microstrip. In the case of limited aperture, only one wire can pass through a small hole, but a clear advantage of the invention is that it is possible to use a relatively large hole to install a device, such as a loudspeaker or microphone, or to place the hole as a voice channel. Since the hole is coated with metal plating, the interference between the device and the antenna is minimal.

Another important feature of the present invention is that the feeder 16 is designed for circular polarization, which is necessary for communication with orbiting satellites in the GPS system. For this purpose, the microstrip part 11, conductive tube 15 or feeder 16 are arranged slightly asymmetrically so that circular polarization can be provided with only one feeding point. The antenna described in the present invention can also work in a linearly polarized environment, but it is rarely used in practice.

The function of the microstrip antenna of the present invention is similar to that of the microstrip antenna generally used for circular polarization, but its advantage lies in its profile shape, ie the hole can be used for various purposes as described below.

Figure 1b shows a diagonal sectional view along the line A-A in Figure 1a.

Filling with ceramic is the preferred embodiment, but in other embodiments materials with low [epsilon] can be used while still maintaining the dimensions required for installation in a communication device such as a modern cellular telephone. The extra capacitance created by the high ε can be replaced by various lumped capacitances near the microstrip edges, one possibility is shown in Figure 2 and discussed below.

Fig. 2 shows another embodiment of the present invention, wherein the microstrip antenna 20 comprises a microstrip member 21 with a folded-down edge 21' at its outer periphery, and a conductive substrate 22 with ridges 22' for The folded down edge 21 ′ is capacitively loaded onto the base plate in region 27 . The antenna 20 also includes a hollow metal tube 25 substantially in the center of the microstrip element 21 and shorting this element to the conductive substrate 22 , thereby creating a hole 24 in the microstrip antenna 20 . A feeder 26 isolated from the conductive substrate is provided to the microstrip component 21 through the conductive substrate 22 . The feeder is usually a coaxial cable, the outer wire of which is connected to the conductive substrate 22 .

In this embodiment, there is no need to introduce highly insulating material in the space 23 between the microstrip component 21 and the conductive substrate 22, because the capacitive coupling in the region 27 reduces the required size of the microstrip component . An obvious advantage of this is that excessive weight of the ceramic material is avoided. The lumped capacitance near the perimeter can be achieved in a number of ways. The insulating material can be air or a low-ε material (for example plastic) which can be coated with a corresponding metal.

FIG. 8 shows yet another embodiment microstrip antenna 80 developed from the embodiment in FIG. 2 . A plastic body 81 is used to support conductive surfaces 82, 83, 87 made by coating metal. The plastic body 81 has a hole 84 and a conductive tube 85 located substantially in the center of the plastic body, cooperating with a groove 86 near the edge, which groove also has an internal metal plating. The outer edge 88 of the groove 86 is not coated with metal, thereby isolating the conductive substrate 82 and the microstrip component 83 . A conductive plate 87 connects an amplifier to a feed point 89, as shown in FIG. The antenna forms the shape corresponding to that shown in Fig. 2, except that the slot will have an extra length due to the current running parallel to the conductive tube, which makes the small microstrip small in size but Still easier to tune.

The antenna 80 is preferably secured to a large conductive surface 90 by, for example, an adhesive to improve the ground plane of the antenna. Such a microstrip antenna can have the same size as a ceramic microstrip antenna and possess excellent mechanical stability. Apparently, this antenna can be combined with a fixed part inside the phone, as shown in FIG. 6 , or can be combined with an integrated amplifier, as shown in FIG. 7 .

Figures 3a and 3b show a communication device 30, such as a mobile cellular telephone, having a first antenna for GPS according to the present invention and a conventional antenna for receiving and transmitting at a frequency different from that of GPS the second antenna for signals in the frequency band.

Figure 3a shows a mobile telephone 30 in a first position for receiving and transmitting radio signals in a cellular telephone system such as GSM, AMPS, PCS or the like. The radio signals are received/transmitted via a second antenna 31 (eg microstrip antenna, monopole antenna, helical antenna, etc. for GSM frequencies). The mobile phone 30 comprises a housing 32, a microphone 33, a loudspeaker 34 and a microstrip antenna 35 for GPS frequencies. The speaker 34 is located in the aperture 36 of the microstrip antenna 35, thereby making the integrated GPS/GSM communication device compact while still maintaining a usable ground plane around the GPS microstrip. There is also a display 37 for providing information during operation of the telephone.

Figure 3b shows the communication device in a second position receiving GPS signals via the microstrip antenna 35 for GPS. The communication device also has a display 3 for providing information (maps, etc.) at the second location.

As mentioned above, since most telephones have a flat, or slightly curved surface that connects acoustically to the ear, the hole 36 in the microstrip antenna 35 can be used to hold the speaker 34 or to transmit the signal from the speaker. The sound transmission channel of the sound. Preferably, the speaker 34 is fed from the rear, and the speaker need not be integrated with the microstrip antenna 35 . A microphone or an acoustic channel for transmitting sound to the microphone can also be used to replace a speaker and be fixed in the hole. At this time, it is better to feed signals from the rear to the microphone, and the microphone does not need to be integrated with the microstrip antenna 35 together.

Larger holes can be utilized in different applications to simplify the integration of the various parts. One of these is a compact-sized roof antenna for automobiles, where size and symmetry are exploited to form a practical solution.

FIG. 4 shows an application of an automotive antenna 40 with a first antenna for GPS communication and a second antenna 42 operating in the mobile cellular communication (eg GSM, PCS, etc.) frequency band. Aperture 43 can be used to provide a telephone antenna (whip antenna, stub antenna, helical antenna, etc.) for the cellular telephone system where symmetry does not interfere with GPS functionality. On the other hand, the microstrip antenna 41 does not interfere with the telephone antenna 42 because of a very different operating frequency and a different type of symmetry. Such an antenna including a GPS antenna is geometrically very similar to a conventional antenna without a GPS antenna. The conductive substrate 44 of the antenna 41 is usually not in direct contact with the grounded part of the vehicle, such as the roof. Magnetic coupling between the antenna 41 and the roof of the vehicle is widely used to secure the antenna to the vehicle.

Most of the time a LNA will be installed close to the GPS antenna. Another function of the hole is to install the low noise amplifier and its related circuits into the hole 72 of the microstrip antenna 70, as shown in Figures 7a and 7b. In this example the microstrip component 73 has a smaller surface area than the ceramic filler 74, as is usually the case when mounting a microstrip component to a ceramic filler. Conductive substrate 75 may be of any suitable size.

Said low-noise amplifier 71 is installed through hole 72, and said amplifier has a housing that is preferably made of metal, and for grounding purpose, preferably this amplifier is pressed into the hole 72 that is coated with metal, and said amplifier also has Cable 76 for feeding it. A coaxial cable could be used instead of the cable 76 as shown. The amplifier also has a contact insulated from the housing and connected to the feed point 77 via a conductive plate 78 on the top surface of the microstrip element 73 . The conductive plate 78 is insulated from the microstrip component 73 . The feed point 77 is also connected to the conductive substrate via a ground wire 79 . It does not matter whether the feed point 77 is connected from the top or the bottom 75, but in this case the feed point is preferably at the top.

In all the examples discussed are flat, substantially square microstrips. All those skilled in the art understand that small changes in the shape of the microstrip can be achieved by appropriately changing its size and thickness. Many microstrip antennas have indentations or short slots in the sidewalls, or have one or more cut corners. In terms of such an antenna's ability to generate circular polarization, etc., what is really important is to be able to find two linear, quadrature resonant frequencies at a suitable phase-to-phase frequency in order to produce a ±45 degree phase shift of the two currents in the quadrature direction . Many shapes, such as approximate rectangles and ellipses, are suitable for use as a profile for such antennas.

To integrate the antenna in a mobile phone, the surface can for example be slightly curved to fit the design of the phone, and the corners of the antenna can be cut out within considerable limits (assuming all other dimensions are changed to maintain the resonant frequency). This situation is illustrated in FIG. 6 , where a slightly bent microstrip antenna 61 is mounted on a telephone 62 . A speaker 63 is installed in a hole in the middle of the microstrip antenna 61 . Obviously, the ceramic material can be formed into virtually any shape by conventional forming methods or by injection molding a ceramic/plastic mixture.

The word "communication device" as used in this specification and claims should be understood to mean any device capable of receiving and/or transmitting wireless signals, such as GPS receivers, mobile phones and pagers.

Claims (12)

1. An antenna, comprising: a microstrip component (21; 83); a conductive substrate (22; 82) substantially parallel to said microstrip member; said microstrip part has at least one feeder (26; 89) to produce circular polarization; said microstrip member (21; 83) has a first hole disposed substantially in the center of said microstrip member; said conductive substrate (22; 82) has a corresponding second hole disposed opposite said first hole; and said antenna further comprising an electrically conductive link (25; 85) between said first and second holes, thereby creating a through hole (24; 84) through said antenna; It is characterized in that the through hole is suitable for realizing at least one non-antenna function. 2. The antenna of claim 1, wherein said at least one function relates to: installing a speaker (34; 63) or a microphone (33) in said through hole; or using said through hole as an acoustic channel for transmitting sound to a microphone (33) or from a speaker (34); or Install an amplifier or other electronic circuit. 3. The antenna according to claim 1 or 2, wherein a capacitance is provided between the edge (21') of said microstrip member (21; 83) and said conductive substrate (22', 22'; 82). sex load. 4. The antenna according to claim 3, wherein said microstrip member (83) is arranged on a support (81) having a groove (86), said groove (86) being coated with metal to produce the capacitive load. 5. An antenna as claimed in claim 4, wherein said support (81) is made of plastic material. 6. An antenna as claimed in any one of claims 1 to 5, wherein said conductive link is a conductive tube (25; 85). 7. Antenna as claimed in any one of the preceding claims, wherein the diameter of said through hole (24; 84) is at least 10% of that of said microstrip member (21; 83). 8. An antenna as claimed in any preceding claim, wherein the antenna is adapted to receive GPS signals. 9. A communication device (30; 62), characterized in that said device (30; 62) comprises a first antenna (35; 61) as claimed in any one of claims 1 to 8. 10. The communication device of claim 9, wherein: a speaker (34; 63) or a microphone (33) is arranged in said through hole; or The through hole serves as an acoustic channel for transmitting sound to a microphone (33) or from a speaker (34); An amplifier or other electronic circuit is disposed in the through hole. 11. A communication device as claimed in any one of claims 9 to 10, wherein said communication device is a mobile telephone (30; 62). 12. The communication device according to any one of claims 9 to 11, wherein the first antenna (61) is slightly curved to match the design of the communication device (62).

Images