KR100683991B1 - Uniplanar dual strip antenna - Google Patents

Abstract

The planar double strip antenna 400 has a two-dimensional structure. The antenna consists of first and second metal strips 404 and 408, each of which is printed or etched onto a thin planar substrate 412. The first and second strips 404, 408 are separated by a predetermined gap T and are used as two-wire transmission lines. Coplanar waveguides 416 and 1520 are coupled to planar double strip antenna 400. Coplanar waveguides 416 and 1520 are made by printing or etching metal on a substrate. The anode terminals 420 and 1522 of the waveguide are electrically connected to the first strip. The negative terminal 424, 428 of the waveguide is electrically connected to both the first and second strips. The planar double strip antenna 400 according to the present invention provides an increase in bandwidth for a typical quarter-wave or half-wave patch antenna. Experimental results show that the planar double strip antenna 400 has a bandwidth of approximately 8-20%, which is very desirable for PCS and cellular telephones.

Description

Planar Dual Strip Antenna {UNIPLANAR DUAL STRIP ANTENNA}

The present invention relates generally to antennas, in particular to planar double strip multi-frequency antennas. The present invention relates in particular to internal antennas for wireless devices, with improved bandwidth and radiation characteristics.

Antennas are an important component of wireless communication devices and systems. Although the antennas are available in many different shapes and sizes, they operate in accordance with the same basic electromagnetic laws. The antenna is a structure related to the transition region between the guided wave and the free space wave or between the free space wave and the guided wave. As a general principle, guided waves traveling along an open transmission line will radiate as free space waves, also known as electromagnetic waves.

Recently, with the increasing use of personal wireless communication devices such as portable and mobile cellular and personal communication service (PCS) phones, the need for small antennas suitable for such communication devices has increased. Recent developments in integrated circuits and battery technology have made it possible to dramatically reduce the size and weight of such communication devices over the last few years. One area where size reduction is still desirable is communication device antennas. This is due to the fact that the size of the antenna can play an important role in reducing the size of the device. In addition, antenna size and shape have a major impact on device aesthetics and manufacturing costs.

One important factor to consider in designing antennas for wireless communication devices is the antenna radiation pattern. In conventional applications, the communication device should be able to communicate with other communication devices or base stations, hubs, or satellites that may be located in either direction from the device. As a result, it is essential that the antennas for such wireless communication devices have an almost omni-directional radiation pattern.

Another important factor to consider in designing antennas for wireless communication devices is the bandwidth of the antenna. For example, wireless devices, such as telephones used in PCS communication systems, operate over the frequency band 1.85-1.99 GHz, requiring 7.29% of available bandwidth. Telephones used in conventional cellular communication systems operate over a frequency band of 824-894 MHz, which requires 8.14% bandwidth. Therefore, antennas used in these types of wireless communication devices must be designed to meet the appropriate bandwidth requirements, otherwise the communication signals are severely attenuated.

One type of antenna commonly used in wireless communication devices is a whip antenna, which normally enters the device when not in use. However, there are several disadvantages with respect to the whip antenna. Often, whip antennas are damaged by objects, people, or surfaces when they are stretched out for use or when they are in. Even if the whip antenna is designed to be able to enter to prevent such damage, the whip antenna can extend across the entire area of the device and hinder the placement of advanced shapes and circuits within some parts of the device. . In addition, the whip antenna may require a minimum device housing dimension that is larger than desired when entered. The antenna may consist of additional sections that are elastic to reduce size when entered, but it is usually less aesthetic, more fragile and unstable, or difficult for consumers to manipulate.

Moreover, the whip antenna is shaped like an empty donut in the center, and has a radiation pattern of the original annular plane. Cellular telephones or other wireless devices using such antennas have a central axis that is inclined at an angle of 90 degrees to the flat or local horizon, and an antenna perpendicular to the flat is preferred. This usually does not prevent the reception of signals since incoming signals do not necessarily reach 90 degrees with respect to the antenna. However, telephone users often tilt their cellular phones during use, tilting the associated whip antenna as well. Cellular telephone users have been known to tilt the whip antenna at a 30 degree angle, usually by tilting the phone at an angle of about 30 degrees to the horizon (60 degrees from the vertical). This results in the central axis of the blank being also directed at an angle of 30 degrees. At that angle, the void prevents the reception of incoming signals that arrive at an angle of 30 degrees. Unfortunately, signals entering the cellular communication system reach around or within a 30 degree angle, and misdirected voids increase the likelihood of blocking some signals from being received.

Another type of antenna that seems suitable for use in wireless communication devices is a conformal antenna. In general, conformal antennas follow the shape of the surface on which they are installed and have a very low profile. There are several different types of conformal antennas, such as patch, microstrip and stripline antennas. In particular microstrip antennas have recently been used in personal communication devices.

As the term suggests, a microstrip antenna includes a patch or microstrip element, commonly called a radiator patch. The length of the microstrip element is set relative to the wavelength λ ₀ associated with the resonant frequency f ₀ selected to match the associated frequency, such as 800 MHz or 1900 MHz. The length of the microstrip element generally used is a half-wavelength (λ _0/2) and quarter wavelength (λ _0/4). Although some types of microstrip antennas have recently been used in wireless communication devices, further improvements are needed in some areas. One such area that needs further improvement is the reduction in overall size. Another area where significant improvements are needed is bandwidth. Current patch or microstrip antenna designs do not appear to achieve bandwidth characteristics of greater than 7.29% to 8.14%, which is desirable for use in advanced communication systems at practical scale.

Thus, there is a need for new antenna structures and antenna fabrication techniques that achieve bandwidths that are more proportional to advanced communication system requirements. In addition, the antenna structure aids in internal installation to provide more flexible component positioning within the wireless device, which should greatly improve aesthetics and reduce antenna damage.

The present invention relates to a planar double strip antenna having a two-dimensional structure. The planar double strip antenna includes first and second metal strips printed on a thin planar substrate, respectively. The first and second strips are separated by a predetermined gap or region of nonconductive material. According to the invention, the first and second strips are used as conductors of two-wire transmission lines. Air between the strips or the dielectric material deposited on the substrate acts as a dielectric medium between the first and second strips. In one embodiment of the invention, the length of the first strip is shorter than the length of the second strip and the width of the first strip is smaller than the width of the second strip.

A coplanar waveguide is coupled to the planar double strip antenna. Coplanar waveguides are made by etching or depositing metal on a substrate. The positive terminal of the waveguide is electrically connected to the first strip. The negative terminal of the waveguide is electrically connected to both the first strip and the second strip. Alternatively, coaxial cables can be used instead of coplanar waveguides as feeds.

In one embodiment of the present invention, the coplanar waveguide has two negative terminals and one positive terminal. The positive terminal is connected to the first strip. The negative terminal is connected to the second strip, while the other negative terminal is connected to the first strip. The negative terminals are electrically connected to each other in a convenient position.

In one embodiment of the present invention, a planar double strip antenna is made by printing, etching or depositing metal strips on a thin flexible substrate. Coplanar waveguides are also etched or deposited onto the flexible substrate. In another embodiment of the present invention, a planar double strip antenna is made by etching or depositing metal strips on a printed circuit (PC) substrate. This greatly simplifies the fabrication of the double strip antenna.

In one embodiment of the invention, the first and second strips are substantially parallel to each other. In another embodiment of the present invention, the first and second strips flare at open ends extending from where they are electrically connected to coplanar waveguides to provide improved impedance matching with atmosphere or free space. However, in another embodiment of the present invention, the first and second strips are bent. Various other forms for the first and second strips may also be used.

Planar double strip antennas according to the present invention usually provide an increase in bandwidth for quarter- or half-wavelength patch antennas. Experimental results show that planar double strip antennas have a bandwidth of about 8-20%, which is very useful for PCS and cellular telephones.

The invention is described with reference to the accompanying drawings. Like reference numerals generally indicate equivalent, functionally similar, and / or structurally similar elements, the first appearing element in the figures being indicated as the leftmost digit in the reference number, which is as follows.

1A and 1B show a portable telephone with a whip and external spiral antennas.

2 shows a conventional microstrip patch antenna.

3 illustrates a side view of the microstrip patch antenna of FIG. 2.

4 illustrates a planar double strip antenna in accordance with one embodiment of the present invention.

5A-5G show plan views of several alternative embodiments of the present invention using spherical transitions to join strips.

6A-6C show plan views of several alternative embodiments of the present invention using curved transitions to join strips.

7A-7E show plan views of yet another alternative embodiment of the present invention using a V-shaped transition to join strips.

8A-8G show plan views of additional optional embodiments of the present invention using curves, angles, and composite strip types.

9A-9B show perspective views of various other embodiments of the present invention useful for other applications.

Figure 10 shows the measured frequency response of one embodiment of the present invention suitable for use in cellular telephones.

Figure 11 shows the measured frequency response of another embodiment of the present invention suitable for use in PCS cordless telephones.

12 and 13 illustrate measured field patterns for one embodiment of the present invention.

FIG. 14 shows a plan view of one embodiment of the present invention for use with the telephone of FIG. 1.

FIG. 15 shows a top view of a signal feed used in the telephone of FIG. 1 and another embodiment of the invention.

16A and 16B show side cross-sectional bottom views of one embodiment of the present invention installed in the telephone of FIG. 1; And

17 illustrates an additional wireless device in which the present invention may be used.

1. Overview and Review of the Invention

Conventional microstrip antennas have several properties that make them suitable for use in personal communication devices, while in other areas of the microstrip antennas to be more desirable for use in wireless communication devices such as cellular and PCS telephones. Further improvement is needed. One area that needs further improvement is bandwidth. In general, PCS and cellular telephones require about 8% bandwidth to operate satisfactorily. Since the bandwidth of currently used microstrip antennas falls in the range of about 1-2%, an increase in the bandwidth of the microstrip antennas is required to make them more suitable for use in PCS and cellular telephones.

Another area that needs further improvement is the size of the microstrip antenna. For example, the reduction in the size of the microstrip antenna will make the wireless communication device in which the antenna is used more compact and aesthetic. In fact, this may even determine whether such an antenna can be used at all in a wireless communication device. In the past, reductions in the size of conventional microstrip antennas are made possible by reducing the thickness of any dielectric substrate used, or by increasing the dielectric constant. However, this has the undesirable effect of reducing the antenna bandwidth, making it unsuitable for wireless communication devices.

Moreover, the field pattern of conventional microstrip antennas, such as patch emitters, is generally directional. Most patch emitters only emit in the upper range relative to the horizon for the antenna. As previously described, this pattern can circulate or move along with the movement of the device, creating undesirable voids in the coverage area. Thus, microstrip antennas were not preferred for use in many wireless communication devices based on their radiation pattern.

The present invention provides a solution to the above and other problems. The present invention operates as a plate waveguide, having a two-dimensional structure and having expandable parallel but asymmetrical conductor ends. Planar double strip antennas provide size reduction and increased bandwidth for other antenna designs while retaining other desirable characteristics for use in wireless communication devices.

Because planar double strip antennas have a two-dimensional structure, they can be supported or conformally attached by various surfaces, such as plastic housings of cellular telephones or other wireless devices. A flat antenna can be made near the top or bottom surfaces of a wireless communication device, such as a mobile phone, or adjacent to or behind other elements such as speakers, earphones, I / O circuits, keypads, etc. in the wireless device. Can be installed. The planar antenna can also be made on or on the surface of the vehicle on which the wireless communication device can be used.

Unlike whips or external spiral antennas, planar double strip antennas are not susceptible to damage to objects or surfaces. In addition, since the planar double strip antenna can be made close to or along the wall of the top surface of the wireless communication device, it will not waste the internal space required for advanced features and circuits, or if the antenna has It will not require large housing dimensions to accommodate when. The antenna of the present invention can be manufactured using automated processes that reduce the labor and cost associated with the antennas and increase their stability. Moreover, planar double strip antennas emit an almost omni-directional pattern making them suitable for many wireless communication devices.

2. Implementation environment

Prior to describing the invention in detail, it is useful to describe an implementation environment in which the invention may be practiced. In a broad sense, the invention may be practiced in any wireless device, such as personal communication devices, wireless telephones, wireless modems, facsimile devices, portable computers, pagers, message broadcast receivers, and the like. One such environment is a portable or handheld cordless phone such as used for cellular, PCS or other commercial communication services. The variety of such cordless telephones, consistent with other housing shapes and styles, is known in the art.

1A and 1B show a conventional wireless telephone 100 for use in wireless communication systems such as cellular and PCS systems discussed above. The radiotelephone shown in Fig. 1 (1A, 1B) has a "clam shell", folding body or flip-type telephone configuration for miniaturization. Other wireless devices and telephones use more typical "bar" shaped housings or configurations.

The telephone shown in FIG. 1 includes a whip antenna 104 protruding from the housing 102 and a spiral antenna 106 coaxial with the whip. The front portion of the housing is a conventional cordless phone component, which is well known in the art, such as a speaker 110, a display panel or screen 112, a keypad 114, a microphone or microphone access hole 116, an external power source connector ( 118 and battery 120. In FIG. 1A, the antenna 104 appears to be in (not visible because of the viewing angle), while in FIG. 1B, the antenna 104 appears in an extended position that generally encounters during use. This telephone is used for illustrative purposes only because of the variety of combined physical configurations and wireless devices and telephones in which the present invention may be used.

As discussed above, antenna 104 has several disadvantages. One is susceptible to damage to other objects or surfaces when the antenna extends during use, and sometimes even when in. The antenna also wastes the internal space of the phone in a manner that makes the placement of components for circuits and advanced features and circuits including power sources such as batteries more restrictive. In addition, the antenna 104 may require a minimum housing dimension that is unacceptably large when entered. The antenna 106 may also get caught in and damage other items or surfaces during use and may not be able to enter the phone housing 102.

The present invention is described in terms of this example environment. The description in this regard is provided solely for the purpose of clarity and convenience. It is not meant to limit the present invention to applications in this implementation environment. After reading the following description, those skilled in the art will clearly know how to implement the invention in alternative environments. In fact, as will be discussed further below, it will be apparent that the present invention can be used in any wireless communication device, such as a portable facsimile machine, portable computer, etc., having the possibility of wireless communication.

2 shows a conventional microstrip patch antenna 200. Antenna 200 includes microstrip element 204, dielectric substrate 208, ground plane 212, and feed point 216. Microstrip element 204 (also commonly referred to as a radiator patch) and ground plane 212 are each made from a layer of conductive material, such as a copper plate.

Although microstrip elements and associated ground planes of different shapes, such as circular, are used, the most widely used microstrip elements and associated ground planes consist of rectangular elements. Microstrip elements can be fabricated using a variety of known techniques, including ground plane photoetching on one side of a printed circuit board, while photoetching on another side or another layer of the printed circuit board. There are many other ways in which microstrip elements and ground planes can be constructed, such as selectively depositing a conductive material over a substrate, bonding the plates to a dielectric, or coating plastic with a conductive material.

3 shows a side view of a conventional microstrip antenna 200. Coaxial cable having a central conductor 220 and an external conductor 224 is connected to the antenna 200. The center conductor 220 (anode terminal) is connected to the microstrip element 204 at the feed point 216. An external connector 224 (cathode terminal) is connected to the ground plane 212. The length L of the microstrip element 204 is generally equal to one-half or one-quarter wavelength at the frequency associated with the dielectric substrate 208 (Richard C. Johnson & Henry Jasik, Antenna Engineering Handbook, 2nd Edition). See chapter 7, page 7-2).

L = 0.5λ _d = 0.5λ ₀ / √ε _r or,

L = 0.25λ _d = 0.25λ ₀ / √ε _r

Where L = length of microstrip element 204

ε _r = relative dielectric constant of dielectric substrate 208

λ ₀ = free space wavelength

λ _d = wavelength at dielectric substrate 208

Since variations in dielectric constant and feed inductance make it difficult to predict exact dimensions, test elements are usually made to determine the correct length. The thickness t is usually much smaller than the wavelength, usually on the order of 0.01λ ₀ , to prevent or minimize lateral current or mode. The t value chosen is based on the bandwidth over which the antenna should operate, which will be discussed in more detail later.

The width "w" of the microstrip element 204 should be smaller than the wavelength in the dielectric substrate material, i.e., lambda _d , so that no higher mode is stimulated. The exception to this is when multiple signal feeds are used to eliminate the higher mode.

A commonly used second microstrip antenna is a quarter wave microstrip antenna. The ground plane of a quarter-wave microstrip antenna generally has a much larger area than the wavelength of the microstrip element. The length of the microstrip element is nearly one quarter wavelength at the frequency relative to the substrate material. The length of the ground plane is nearly one-half wavelength at the frequency relative to the substrate material. One end of the microstrip element is electrically connected to the ground plane.

The bandwidth of a quarter-wave microstrip antenna depends on the thickness of the dielectric substrate. As described above, PCS and cellular radiotelephone operations require approximately 8% of bandwidth. In order for a quarter wave microstrip antenna to meet the 8% bandwidth requirement, the thickness of the dielectric substrate 208 should be approximately 1.25 inches for the cellular frequency band (824-894 MHz) and 0.5 inches for the PCS frequency band. This size thickness is obviously undesirable for small wireless or personal communication devices where a thickness of approximately 0.25 inches or smaller is desirable. Antennas of greater thickness are generally not acceptable within the available volume of most wireless communication devices.

3. The present invention

A planar double strip antenna 400 operating and made in accordance with one embodiment of the present invention is shown in FIG. In FIG. 4, the planar double strip antenna 400 includes a first strip 404 and a second strip 408, a dielectric substrate 412, and a coplanar waveguide 416. The first strip 404 is electrically connected to one end or adjacent one end of the second strip 408. This termination is referred to as the "closed termination" 406 for the antenna 400.

The first and second strips 404, 408 are printed, etched, or deposited on the dielectric substrate 412, respectively, and are made of copper, brass, aluminum, silver, gold, or other known conductivity applied to known impedance and current characteristics. Made of conductive material like materials. The first and second strips 404, 408 are spaced from each other by a predetermined gap T, which gap may be filled with a dielectric material (usually air), such as a foam, known for such use as desired. . In one embodiment of the invention, the first and second strips 404, 408 are disposed substantially parallel to each other for their respective lengths. In another embodiment (see, eg, FIGS. 5A-5C and 9B), the first and second strips flare at open ends to provide better impedance matching with air or free space.

A coplanar waveguide 416 having a positive terminal 420 and two negative terminals 424 and 428 is connected to the first and second strips 404 and 408. In one embodiment of the invention, the positive and negative terminals 420, 424, 428 are formed of three parallel metal strips. The center strip is designated as the positive terminal 420 and is electrically connected to the first strip 404. One outer strip is designated negative terminal 424 and the other outer strip is designated negative terminal 428. The negative terminal 424 is electrically connected to the first strip 404 and the negative terminal 428 is electrically connected to the second strip 408. In one embodiment of the present invention, coplanar waveguide 416 is constructed by depositing, etching, or printing a metal over dielectric substrate 412. The coplanar waveguide 416 is made of a conductive material such as copper, silver, gold, aluminum or other known conductive materials. Alternatively, coaxial cables may be used as feed instead of coplanar waveguides.

The planar double strip antenna 400 has a two-dimensional structure. The antenna can thus be attached to match many surfaces, such as plastic housings of cellular telephones. In one embodiment of the present invention, antenna 400 is deposited, printed or etched onto a flexible sheet that can function as a dielectric substrate or medium, such as Mylar, Kapton or other known flexible dielectric materials. The dual strip antenna may advantageously be installed over a thin portion of wireless devices, such as the flip, clam shell or folding portion of a wireless mobile phone, as discussed below.

The length and width of the first and second strips 404, 408 primarily determine the resonant frequency of the planar double strip antenna 400. The length and width of the first and second strips 404, 408 are approximately sized such that the first and second strips 404, 408 operate as a two-wire transmission line capable of receiving and transmitting signals having a preselected desired frequency. Is set. It is well known in the art how to select an appropriate length and width such that the first and second strips 404, 408 operate as two-wire transmission lines at the desired frequency. In brief, in order for the first and second strips 404 and 408 to operate as two-wire transmission lines, each must have a length of approximately [lambda] / 4, where [lambda] is the wavelength at a frequency related to the electromagnetic wave. Next, the bandwidth of the resulting antenna formed of a two-wire transmission line is increased. This is done by reducing the length and width of the first strip while increasing the length and width of the second strip until the desired bandwidth is achieved.

Coplanar waveguide 416 couples a signal unit (not shown) to dual strip antenna 400. Note that the signal unit is used herein to refer to the functionality provided by the signal source and / or signal receiver. The signal unit provides one or both of these functions depending on how the antenna 400 operates. Antenna 400 may be configured to operate only as a transmission element, for example when the signal unit operates as a signal source. Optionally, the signal unit operates as a signal receiver when the antenna 400 is configured to operate only as a receiving element. The signal unit provides both functions in the form of a transceiver when the antenna 400 is configured to operate as both transmitting and receiving elements.

The antenna or strip may be formed in a variety of other forms such as, but not limited to, quarter round, semicircle, semi-ellipse, parabolic, angled, round and square C, L, U, V. have. V-shaped structures can vary from less than 90 degrees to nearly 180 degrees. Curved structures can use relatively small or large radii. The widths of the conductors, i.e., the first and second strips, can be varied along their length such that the taper, curve, or others vary stepwise toward the outer end (non-feed portion). . As will be appreciated by those skilled in the art, these various effects or forms may be combined in a single antenna structure.

Several top views of alternative embodiments or forms of strips of the present invention are shown in FIGS. 5A-5G, 6A-6C, where the last digit of the reference number indicates that the item is a first strip or a second strip, ie 4 or 8, respectively. Appear in 7a-7e and 8a-8f. The first digit and the last letter indicate a diagram in which elements such as 504A for FIG. 5A and 708B for FIG. 7B appear. For clarity, the widths of the strips used in these forms are usually not comparable. However, as discussed above, as will be readily apparent, these two strips will generally have different widths to achieve the desired bandwidth.

The antenna embodiments shown in FIGS. 5A-5G illustrate alternative forms for the present invention using right angle or square transitions to connect the strips together. That is, for the closed end of the antenna in the embodiments shown in FIGS. 5A-5G, the first and second strips are connected or coupled together using vertical conductive connecting elements or transition strips 506, 506A- 506G. In addition, further change in direction with respect to the strips associated with each other is achieved with substantially square corners. Each change of direction is substantially perpendicular to the previous portion, or is involved in the positioning of a new portion of each strip at an angle of 90 degrees. Of course, these angles do not need to be accurate for most applications and other angles can be used with curved or rounded grooved corners as desired.

5B shows that the strip can be folded to maintain the overall desired length for the antenna structure to accommodate the longer second strip. 5C shows that the first strip can be folded towards or away from the plane on which it is laid. 5D shows that the second strip can be folded partially or completely surrounding the first strip. 5E shows the expansion of the first strip over the folded structure. 5F shows that the change in direction for the first and second strips is achieved in a smaller "step". Optionally, the end portion of each strip may be bent at some angle or directed at an angle to form a Y-shape as a whole, as shown in FIG. 5G. Generally, the separation angle is a 90 degree angle where a blunt Y-shaped termination structure is allowed, although not required.

The antenna embodiments shown in FIGS. 6A-6C illustrate alternative forms for the present invention using curved or curved transitions to connect the strips together. That is, in the embodiments shown in FIGS. 6A-6C, the first and second strips are connected or coupled together to a closed end using curved conductive connection elements or transition strips 1606 (1606A-1606C). The strips 1606 (1606A-1606C) can have a variety of shapes including quarter, semi-circle, semi-ellipse, or parabola or combinations thereof. Curved structures can use relatively small or large radii that are desirable for a particular application. In addition, each strip may be folded to maintain the overall desired length for the antenna structure, as shown in FIGS. 5A-5G. FIG. 6A generally shows a curved semicircle, FIG. 6B generally shows a quarter-circle, elliptical, curved transition, and FIG. 6C generally shows a transition of a parabolic curve. These forms of transitions can also be used in combination.

The antenna embodiments shown in FIGS. 7A-7E illustrate alternative forms of the present invention using a V-shaped transition to connect the strips together. That is, in the embodiments shown in FIGS. 7A-7E, the first and second strips are connected or coupled together at the closed end without using separate conductive connecting elements or transition strips, or by using very small ones. Instead, the first and second strips extend from the common coupling in an external separation or flare configuration. In addition, as before, each strip may be folded to maintain the overall desired length for the antenna structure, as shown in FIGS. 5A-5H.

7A and 7B generally illustrate a vertical V-shaped or acute transition that couples together. In FIG. 7B, the two strips are generally bent back to form parallel strips or to provide reduced angular tilt with respect to each other. In Figures 7C-7E, at least one of the two strips is bent after the first V-shaped bond. In FIG. 7C, both strips bend as if in accordance with an exponential or parabolic curve function. In FIG. 7D only one strip is bent and in FIG. 7E both strips are bent but folded into a vertical section. Previously, this type of transition can also be used in combination, preferably for a particular application.

8A-8G illustrate various alternative embodiments or forms for strips of the present invention using curved, angled and composite strips. Here, the strips are arranged almost parallel to each other for their respective lengths, but the strips are circular or elliptical in FIG. 8G using conductive connecting elements or transition strips 806 (806A-806F) or without strips being used. Follow a circular, sigmoidal, or V-shaped path that extends outward from where they are connected or joined together at the closed end. The use of the composite form also allows the formation of an antenna structure on the support substrate to support circuitry or discrete components and devices, or to allow gap passages around other devices within the target wireless device.

This antenna structure is a two-dimensional structure that exists in a single plane, which is a conformal or suitable structure in which the plane does not have to be flat. That is, by bending or shaping the supporting substrate, the shape of the planar antenna can also be effectively varied in three dimensions. A pair of strips appearing in a flat plane surface in two dimensions can be bent along an arc in three dimensions (where z) or bend at an angle. Various embodiments of the present invention in which a pair of strips bend or bend in the z direction are shown in FIGS. 9A-9C. These embodiments are very useful when it is desirable to place the antenna in any space of the wireless device where the antenna needs to be "fit" to any component or structure within the wireless device.

FIG. 9A shows first and second strips as shown in FIG. 4, curved along each length in three dimensions, using a simple curve. FIG. 9B shows the first and second strips as shown in FIG. 7A, which are connected together in a V-shaped or acute transition, but shown in a three-dimensional V-shaped offset. More complex sets of curves or folds are used to form the plane in which the strips are present in FIG. 9C.

The dual strip antenna 400 may be constructed by etching or depositing a metal strip on opposite sides of the dielectric substrate and electrically connecting the metal strips together at one end using one or more plated through vias, jumpers, connectors or wires. have. In this form, antenna 400 utilizes a portion of the substrate material as a dielectric disposed between two strips. This is considered in designing the antenna in terms of bandwidth and other characteristics as is well known. The dual strip antenna 400 also emulates or forms a plastic or other known insulating or dielectric material with a support substrate of the desired shape (U-, V-, C, or curved, rectangular, etc.), It can be constructed by plating or covering the plastic with a conductive material comprising a conductive material in liquid form on the appropriate portions using well known methods.

The dielectric substrate may be secured in portions of the wireless device housing using posts, ridges, channels, etc. formed in the material used to fabricate the housing. That is, such supports are shaped or formed on the wall of the device housing when manufactured by a method such as molding injection. These support elements can hold the substrate in place during insertion of the phone, when inserted into or over them. Other techniques include the use of a layer of adhesive material to secure the assembly in the device housing or the use of some form of fastener or preservative that interacts with the edges or holes of the substrate.

As described above, according to the present invention, the first and second strips 404, 408; 504, 508; 604, 608; 704, 708; 804, 808, etc. operate as two-wire transmission lines. One advantage of two-wire transmission lines is that they do not require a ground plane. This causes the antenna 400 to be a two-dimensional structure having a negligible thickness. Most of the thickness of the antenna 400 is determined by the thickness of the dielectric substrate 412. For example, a thin Mylar or Kapton sheet having a thickness in the range of 0.0005 inches to 0.002 inches can be used as the dielectric substrate. In contrast, conventional microstrip antennas designed for cellular frequency band operation require a dielectric substrate having a thickness of 1.25 inches, whereas microstrip antennas for the PCS frequency band require a dielectric substrate having a thickness of 0.5 inches. . The present invention thus allows for a substantial reduction in the overall thickness of the antenna, which makes it more desirable for personal communication devices such as PCS or cellular telephones. However, those skilled in the art will readily appreciate that other thicknesses may be used, including thicker materials, to maintain the desired structural integrity for the antenna when the antenna is used or during the manufacture or service of a wireless device.

The planar double strip antenna 400 according to the present invention provides an increase in bandwidth compared to conventional quarter wavelength or half wavelength patch antennas. Experimental results have shown that antenna 400 has a bandwidth of approximately 8-20%, which is very desirable for PCS and cellular telephones. As described above, conventional microstrip antennas have a very narrow bandwidth, making them less desirable for use in personal communication devices.

In the present invention, the increase in bandwidth is mainly enabled by operating the antenna 400 with a two-wire transmission line rather than as a conventional microstrip patch antenna. Unlike conventional microstrip patch antennas with radiator patches and ground planes, in antenna 400, both first strip 404 and second strip 408 operate as active radiators. In other words, the length and width of the first strip and the second strip are carefully set such that the first strip 404 and the second strip 408 act as active radiators, at the relevant frequency or wavelength. During operation of the antenna 400, surface current is induced in the first strip as well as in the second strip. Initially, the inventors selected the appropriate dimensions, namely length and width, of the first and second strips using analytical methods and EM simulation software well known in the art. Thereafter, the inventors demonstrated the simulation results by experimental methods known in the art.

In order to enhance the radiator or antenna bandwidth, in the preferred embodiment the dimensions of each strip are chosen to set different center frequencies relative to one another in a preselected manner. For example, f ₀ refers to the preferred center frequency of the antenna. Shorter strip lengths may be selected so that the center frequency is at or near f ₀ + Δf, and longer strip lengths are selected so that the center frequency is at or near f ₀ −Δf. This gives the antenna a wide bandwidth on the order of 3Δf / f ₀ to 4Δf / f ₀ . That is, the antenna radiator bandwidth is enhanced as a result of using the +/- frequency offset related to f ₀ . In this configuration, Δf is chosen to be much smaller in size than f ₀ (Δf << f ₀ ), so the resonant frequency spacing of the two strips is small. It is believed that if Δf is chosen as large as f _{0, the} antenna will not operate satisfactorily. In other words, it is not used as a dual band antenna by each strip operating as an independent antenna radiator.

In the present invention, an increase in bandwidth is achieved without corresponding increase in antenna size. This is in contrast to the features of conventional patch antennas, which generally increase the bandwidth by increasing the thickness of the patch antennas, thereby increasing the overall size of the patch antennas.

In one embodiment of the present invention, antenna 400 is sized appropriately for the cellular frequency band, i.e., 824-894 MHz. The dimensions of the antenna 400 for the cellular frequency band are given in Table 1 below.

Table 1

Length L1 of the first strip 404 2.4 inch Length L2 of second strip 408 4.53 in Width W1 of the first strip 404 0.062 in Width W2 of the second strip 408 0.125 in Gap t between first strip 404 and second strip 408 0.125 in

In the typical embodiment above, 1 oz of copper was used to make the first strip 404 and the second strip 408, and 0.031 inch thick FR4 (a well known commercially available printed circuit board (PCB) material) is a dielectric. It was used as the substrate 412. Also, the positive terminal of the coplanar waveguide 416 was connected to the first strip 404 at a distance of 0.330 inches from the closed end of the antenna 400.

10 illustrates a measured frequency response of one embodiment of an antenna 400 sized to operate over a cellular frequency band. 10 shows that the antenna has a frequency response of -15.01 dB at 825 MHz and a frequency response of -17.38 dB at 895.0 MHz. Thus the antenna has a bandwidth of 8.14%.

In another exemplary embodiment of the invention, the antenna 400 is sized to operate over the PCS frequency band, i.e., 1.85-1.99 GHz. The dimensions of the antenna 400 for the PCS frequency band are given in Table 2 below.

TABLE 2

Length L1 of the first strip 404 0.89 in Length L2 of second strip 408 2.10 in Width W1 of the first strip 404 0.062 in Width W2 of the second strip 408 0.125 in Gap t between first strip 404 and second strip 408 0.125 in

In the typical embodiment above, 1 oz copper was used again to make the first strip 404 and the second strip 408, and 0.031 inch thick FR4 (PCB material) was used as the dielectric substrate 412. Also, the positive terminal of the coplanar waveguide 416 was connected to the first strip 404 at a distance of 0.2 inches from the closed end of the antenna 400.

11 shows the measured frequency response of one embodiment of an antenna 400 sized to operate over a PCS frequency band. 11 shows that the antenna has a -9.92 dB response at 1.79 GHz and a -10.18 dB response at 2.16 GHz. Thus, in this embodiment, the antenna 400 has 18.8% bandwidth.

12 and 13 show measured field patterns of one embodiment of an antenna 400 operating over a PCS frequency band. In particular, FIG. 12 shows a plot of the size of the field pattern in the azimuth plane, while FIG. 13 shows a plot of the size of the field pattern in the altitude plane. 12 and 13 show that the dual strip antenna has an approximately omni-directional radiation pattern, thereby making it suitable for use in personal communication devices.

As long as the second strip is much longer than the first strip, generally using an "D" shaped emitter strip arrangement that extends "inside" and folds away from the first strip, and preferably even into the second strip itself. Examples have been developed. This antenna structure is shown in FIG. 14 in which antenna 1400 is formed using strips 1404 and 1408 overlying or disposed on substrate 1412. The top portion of the antenna is formed by the first conductive strip 1404 which appears to be slightly curved to the "C" shape (or the leading edge of D). This curvature is used to enable placement of the antenna 1400 adjacent to or on the side of the device housing with curved sidewalls. The second strip is wider than the first strip to improve bandwidth, as discussed above.

Models of such antennas have been tested and constructed to have overall dimensions on the order of 37.59 mm (Y) versus 51.89 mm (X) roughly matching the internal size of the flip-top portion of the clamshell type cordless phone on which the antenna is placed.

Antenna 1400 is connected to appropriate transceiver circuitry within the wireless device using feed section 1416. The device 1420 may be configured to describe how various known circuit components or devices may be installed on the substrate 1412, or optionally how the passages or holes 1422 may preferably extend through the various components or cables. Explain whether it can be formed.

A preferred embodiment has been developed which uses a D-shaped emitter strip arrangement in which the second strip is much longer and wider than the first strip, and generally extends to "surround" the first strip. Such an antenna structure is shown in FIG. 15 in which antenna 1500 is formed using strips 1504 and 1508 overlying or disposed over substrate 1512. Again, the top portion of the antenna 1500 formed by the second strip appears to be slightly curved to allow for improved placement of the antenna 1500 in the wireless device.

This type of antenna can be formed in a combined structure with conductors used to supply signals. The coaxial feed structure may be formed over the same flexible substrate 1512 as the conductors forming the antenna. For example, Mylar, Kapton, or Teflon based thin sheets are all well known in the art. An example of how this is achieved is shown in FIG. 15 in which a long flexible signal feed structure or section 1520 is shown in the form of a "coplanar waveguide." Waveguide 1520 contacts or defines one end to cathode feed strips 1524 and 1528 that form part of the ground portion of the coplanar waveguide. The feed strip 1524 is connected or coupled to the connecting element 1506, while the other feed strip 1528 is connected to the second strip 1508. The center of the positive feed strip 1522 or feed structure 1520 is directly connected to the first strip 1504. The spacing between the connection and strip 1528 for this feed strip is selected to provide a predetermined impedance depending on the frequency and length used, and other dimensions of the conductive material 1506, as is known.

The positive feed 1522 is shown to define a short distance along the material 1512 and is generally connected to or coupled to the conductors 1524 and 1528, or a third central conductor similar to the conductors 1524 and 1528. 1526). Conductor 1526 extends along connector length 1530 along the length of material 1512 to form the center or anode portion of the coplanar waveguide.

However, other configurations may be used, including placing one or more feed strip conductors on opposite sides of the substrate. For example, an anode feed conductor may be formed on one side of the material 1512 and cathode feeds may be formed on the other side. Where appropriate, conductive vias are used to transmit signals through the material. Other combinations of conductors and vias may be used to realize signal transmission as is known in the art.

The antenna 1500 is thus formed as one unitary structure with these conductors 1522, 1524, 1528, providing an improvement in cost efficiency, stability and manufacturing efficiency. The conductors 1524, 1526, 1528 of the feed section 1520 are typically limited to small connectors 1532 or conductive pads that are used to load connectors or connect various spring operations onto a circuit board to which the antenna is coupled.

The configuration or overall configuration of the waveguide or feed portion 1520 and the substrate 1512 used in FIG. 15 is for illustration only and to be very effectively adapted within the wireless device 100 as shown. However, those skilled in the art will readily understand that other configurations may be useful and are within the nature of the present invention. For example, instead of angled bends along the length of waveguide 1520 at approximately 45 degree angles, a series of 90 degree bends, folds, turns can be used for the conductors. Obviously, if small cables are used, various bends and turns can be used. Such folding and rotation is used to minimize the path length of the conductors while accepting the physical constraints imposed on the substrate or antenna. In addition, conductors 1524, 1526, and 1528 are generally narrow at one or more points along waveguide 1520, and such locations may also vary depending on the particular application. The small air bridges shown in FIG. 15 for electrically coupling conductors 1524 and 1528 are useful but not required by the present invention.

When the feed structure or waveguide 1520 is disposed inside a wireless device such as a wireless telephone 100, efficient signal transmission between the antenna 1500 and the various receiving and transmitting elements and components used within the wireless device. To make it possible. By forming the antenna and coplanar waveguide on a common, but thin, flexible dielectric substrate, the antenna occupies very little space and can be installed in many parts of a device because it can be formed around many other discrete components such as speakers. have. Feed conductors can form connections around flexible loops or collapsing joints such as those found in many wireless devices (telephones, computers).

Alternatively, small coaxial lines may be used instead of waveguide (feed) 1520 to achieve similar results. For example, it has been shown that known types of coaxial lines or cables having a diameter of 0.8 mm or 1.2 mm may be useful for transmitting signals between the antenna 1500 and the corresponding or appropriate circuit elements. Other styles and types of conductors may be used for specific applications, depending on signal transmission characteristics, as is known.

16A and 16B show cutaway side views, respectively, of the side and back of one embodiment of the present invention installed within the telephone 100 of FIG. Such telephones generally have a variety of internal components that are generally supported on one or more circuit boards to perform various required or desirable functions. The circuit board 1602 has a housing 102 that supports various components such as discrete components 1606, such as resistors and capacitors, integrated circuits such as various connectors 1608, and chips 1604 in FIGS. 16A and 16B. Appears inside of. Panel displays and keyboards are installed on opposite sides of the board 1602, and typically interface various other components, such as batteries, external power supplies, speakers, microphones, or other well-known elements, to circuitry on the board 1602. The wire, conductor, and connector (not shown) face the front of the phone housing 102.

In this embodiment, a slide-in or plug-in connector 1610 is installed at the bottom of the substrate, near the front of the phone, to accommodate the connection end of the feeder section 1520 to the antenna 1500. It is composed. Optionally, one or more known spring contacts or clips may be used to contact the conductive pads to the termination 1530 and electrically couple or connect the antenna 1500 to the substrate 1602. Such spring contacts or clips are mounted on the circuit board 1602 using well known techniques such as soldering or conductive attachments, and electrically connected to conductors suitable for transmitting signals to and from the desired transmit and receive circuits. Connected. However, other forms of connection technology, including the use of solder or the use of small coaxial connectors (when small cables are used) are also known to be useful. Well known and preferred impedance matching elements and circuits used within the wireless device to interconnect with the feed structure can be characterized.

In the side view of FIG. 16B, the circuit board 1602 appears to include multiple layers of conductive and dielectric materials attached together to form what are referred to in the art as multiple layers or printed circuit boards (PCBs). Such substrates are well known and known in the art. This appears to be after the metal conductor layer 1618 is placed or supported with a layer of dielectric material 1616, followed by a layer of metal conductor 1614, followed by a layer of dielectric material 1612. Conductive vias (not shown) are used to interconnect the various conductors over other layers or levels having components on the outer surfaces. The patterns etched on any given layer determine the interconnection patterns for that layer. In such a configuration, layer 1614 or layer 1618 may form a ground layer or ground plane, as is generally referred to substrate 1602, as is known in the art.

Generally, a series of support posts, stands, or ridges 1620 are used to install circuit boards or other components within the housing. These may be formed as part of the housing, such as formed by mold plastic injection or fixed in place using attachment or other well known mechanisms. In addition, there is one or more securing posts 1622 that are used to receive fasteners that secure portions such as removable covers of the housing 102 relative to each other.

As previously reviewed, antenna 1500 may be secured within portions of housing 102 using various known techniques, such as adhesives, glues, tapes, potting compounds, bonding compounds, etc., which are known to be useful for this function. . For example, antenna 1500 may be supported against elements, sidewalls, or other portions of a wireless device using an adhesive layer or strip 1630 adhered to substrate 1512. The antenna is generally fixed relative to the housing face, preferably on an insulating material or against a bracket assembly that can be installed in place using brackets, screws or similar fastening elements.

Alternative mechanisms are known for securing or installing the antenna in place. For example, ridges, channels, etc. formed in the materials used to make the housing can be used to physically hold the substrate in place. A series of protrusions or bumps may also be used to support the antenna and may have a variety of forms suitable for the desired application.

As shown in FIG. 16B, the substrate 1512 may be bent or bent to closely match the shape of the housing or to accommodate other elements, features, components within the wireless device. In the figure, speaker 1632 appears to be disposed with a portion of which is " enclosed " with antenna radiators or strips.

The substrate may be manufactured in a curved or folded form or warped during installation. The use of thin substrates allows the substrate to be held in place generally without the need for fasteners when the substrate is installed, sometimes providing tension or pressure against a fixed or curved adjacent surface. Several forms of capture are simply achieved by installing adjacent housing parts or covers and circuit boards, adjacent devices or components in place. However, it is not necessary to bend or warp the substrate during manufacture or installation to properly operate the present invention.

FIG. 17 illustrates additional wireless devices in which the present invention may be used, such as but not limited to portable computers, modems, data terminals, facsimile machines or similar portable electronic devices. In FIG. 17, a wireless device or equipment using the wireless device 1700 appears to have a main housing or body 1702 having an upper corner section 1704. In the cutaway view of FIG. 17, antenna 500 is fixed in place at upper corner 1704, and a cable or conductor set 1708 is used to connect antenna feed 516 to appropriate circuitry within the wireless device. Those skilled in the art will readily appreciate that other configurations and orientations are possible for the antenna within the nature of the invention.

While various embodiments of the invention have been described above, it should be understood that the embodiments are illustrative only and not limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims (19)

A planar double strip antenna comprising a first electrically conductive metal strip and a second electrically conductive metal strip mounted on a single side of a dielectric substrate, the antenna comprising: The first and second strips are spaced apart from each other by a selected constant gap, and the length and width of the first and second strips form a two-wire transmission line for the first and second strips to receive and transmit electromagnetic energy. Is selected to; The planar double strip antenna further comprises a coplanar waveguide having a positive terminal and a negative terminal, wherein the coplanar waveguide is formed by depositing a metal on the same side of the substrate, the positive terminal being connected to the first strip. Is electrically connected, and the negative terminal is electrically connected to the first and second strips, and the first and second strips when the planar double strip antenna is energized by an electrical signal through the coplanar waveguide. A planar double strip antenna on which surface current is formed. 2. The planar double strip antenna of claim 1 wherein the first and second strips comprise metal strips printed on the same side of the dielectric substrate. 2. The planar double strip antenna of claim 1 wherein the first and second strips comprise metal strips deposited on the same side of the dielectric substrate. 2. The planar double strip antenna of claim 1 wherein the first strip is substantially parallel to the second strip. 2. The planar double strip antenna of claim 1 wherein the length of the first strip is shorter than the length of the second strip. 2. The planar double strip antenna of claim 1 wherein the length of the first strip is equal to the length of the second strip. 2. The planar double strip antenna of claim 1 wherein the width of the first strip is narrower than the width of the second strip. 2. The planar double strip antenna of claim 1 wherein the width of the first strip is equal to the width of the second strip. The planar double strip antenna of claim 1, wherein the dielectric substrate is a flexible sheet capable of operating as a dielectric medium. The plane of claim 1, wherein the length and width of the first and second strips are set to a size such that the plane dual strip antenna can receive and transmit signals having a frequency range of 1.85-1.99 GHz. Double strip antenna. 2. The plane of claim 1 wherein the length and width of the first and second strips are set to a size such that the plane dual strip antenna can receive and transmit signals having a frequency range of 824-894 MHz. Double strip antenna. delete delete delete delete delete delete delete delete

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