WO2000051199A2

WO2000051199A2 - Systems and methods for coaxially coupling an antenna through an insulator and for amplifying signals adjacent the insulator

Info

Publication number: WO2000051199A2
Application number: PCT/US2000/002346
Authority: WO
Inventors: Gregory A. O'neill, Jr.
Original assignee: Ericsson, Inc.
Priority date: 1999-02-11
Filing date: 2000-01-31
Publication date: 2000-08-31
Also published as: WO2000051199A3; DE10084156T1; JP2002543555A; CN1340224A; AU2746900A; WO2000051199A9

Abstract

Coaxial coupling systems and methods couple a first coaxial cable that includes a first inner conductor and first shield conductor to a second coaxial cable that includes a second inner conductor and a second shield conductor, through an insulator that includes first and second insulator surfaces. A first center plate and a first surrounding plate are adapted for attachment to the first insulator surface such that the first surrounding plate surrounds the first center plate on the first insulator surface. The first center plate is electrically connected to the first inner conductor and the first surrounding plate is electrically connected to the first shield conductor. A second center plate and a second surrounding plate are adapted for attachment to the second insulator surface and for connection to the second coaxial cable in the same way.

Description

SYSTEMS AND METHODS FOR COAXIALLY COUPLING AN ANTENNA

THROUGH AN INSULATOR AND FOR AMPLIFYING SIGNALS

ADJACENT THE INSULATOR

Field of the Invention

This invention relates to coupling systems and methods and more particularly to systems and methods for coupling antennas through an insulator, for example to couple antennas to radiotelephones.

Background of the Invention Antenna coupling systems and methods are widely used to couple an antenna to a receiver through an insulator. For example, in mobile radiotelephone communications, a radiotelephone such as a cellular radiotelephone may be mounted in the interior of a vehicle. An antenna may be mounted on the exterior of the vehicle. Coupling systems and methods are used to couple the antenna to the radiotelephone through an insulator such as a window. As used herein, the term "radiotelephone" includes analog and digital radiotelephones, multiple mode radiotelephones, high function Personal Communications Systems (PCS) devices that may include large displays, scanners, full size keyboards and the like, wireless

Personal Digital Assistants (PDA) and other devices, such as personal computers that are equipped with wireless modems and other wireless electronic devices.

It will be understood by those having skill in the art that although the present application will describe the coupling of mobile radiotelephones to antennas through a vehicle window, the present invention may be applied to any radio transceiver and the insulator need not be limited to windows. Moreover, the present invention need not be used in a mobile environment but also may be used to couple an antenna outside a building to a transceiver inside a building through an insulator.

It is known to use a capacitive plate on either side of a window to capacitively couple high frequency signals through the window. See U.S. Patent 4,621,243 to Harada entitled ''''Transmission Channel Coupler for Antenna ". This patent also describes the use of loop coils and helical resonators to transmit high frequencies through a window. Multiple plates also may be used on either side of the window to capacitively couple signals therethrough. See for example, U.S. Patent 2,829,367 to Rychlik entitled "Television Lead-in Coupler" and U.S. Patent 4,764,773 to Larsen et al. entitled "Mobile Antenna and Through-the-Glass Impedance Matched Feed System ". Finally, it is also known to provide a collinear radiator mounted on one surface of a dielectric such as the window of a vehicle and a tunable coupling circuit disposed internally of a conductive housing mounted on the opposite surface of the dielectric. See U.S. Patent 4,839,662 to Hadzoglou entitled "Cellular Mobile Communication Antenna ". In providing antenna coupling systems and methods, it generally is desirable to couple the antenna to the transceiver through the insulator with low insertion loss. For example, in satellite radiotelephones which may provide low link margins, it may be desirable to maintain insertion loss through the insulator of about 0.5 dB or less. Unfortunately, many conventional coupling systems produce an insertion loss of 2 dB or more. Moreover, many high performance antennas employ two or more conductors rather than a single conductor. For example, a quadrifiler helix antenna may employ two or more conductors. Accordingly, it may be desirable to couple radio frequency signals via a coaxial cable from inside the insulator to a coaxial cable outside the insulator. It also may be increasingly difficult to efficiently couple an antenna to a radiotelephone transceiver. In particular, in many radiotelephone applications, the radiotelephone is located within an enclosure such as a vehicle or a building. However, it may be desirable to include the antenna outside the enclosure in order to provide adequate link margin. For example, in radiotelephone communications involving radio links between a mobile vehicle and a communication satellite, it is generally desirable for the antenna to be outside the vehicle. It is also generally desirable to have a radio frequency receiver unit near the antenna in order to allow an improved receiver antenna gain to receiver system temperature ratio. Moreover, as a practical matter, it also may be desirable to include a transmitter power amplifier near the antenna, to overcome transmission loss between the antenna and the transceiver. It is known to provide an external electronic package or module adjacent an antenna outside a vehicle window, to thereby improve the performance of a radiotelephone within a vehicle. Unfortunately, external electronic packages may be subject to environmental hazards and damage by vandals. Other hazard potentials include automatic car washing facilities that can damage external electronic packages.

Moreover, it may be difficult to couple an electronic package outside the window to a radiotelephone inside the vehicle. It may be unacceptable to cut holes in the widow or other parts of the vehicle body. The running of coaxial cables through doorjambs may not be acceptable. Accordingly, although outdoor antenna units that combine an antenna and an electronic package have been used in the trucking industry or in marine applications (such as the INMARSAT-C system), it may be generally undesirable for terrestrial cellular and satellite radiotelephone communications systems such as the Iridium, Globalstar and ACeS systems.

It is also known to allow a radiotelephone antenna to be used within an enclosure such as a building or a vehicle. While this solution may be acceptable for many cellular radiotelephone communications, it may not be desirable for satellite radiotelephone communications which may have low link margins and which preferably operate in a direct line of sight path between the radiotelephone and the communications satellite.

Summary of the Invention

The present invention can provide coaxial coupling systems and methods that couple a first coaxial cable that includes a first inner conductor and first shield conductor to a second coaxial cable that includes a second inner conductor and a second shield conductor, through an insulator that includes first and second insulator surfaces. A first center plate and a first surrounding plate are adapted for attachment to the first insulator surface such that the first surrounding plate surrounds the first center plate on the first insulator surface. The first center plate is electrically connected to the first inner conductor and the first surrounding plate is electrically connected to the first shield conductor. A second center plate and a second surrounding plate are adapted for attachment to the second insulator surface such that the second surrounding plate surrounds the second center plate on the second insulator surface, the first and second center plates are adjacent one another with the insulator therebetween and the first and second surrounding plates are adjacent one another with the insulator therebetween. The second center plate is electrically connected to the second inner conductor and the second surrounding plate is electrically connected to the second shield conductor. It has been found according to the present invention, that coaxial coupling systems and methods as described above can allow communication signals to pass with low insertion loss, over a desired frequency range, between an antenna mounted outside a window and a radio transceiver mounted inside the window. Transmission takes place via a coaxial transmission line on each side of the window. Moreover, by allowing two or more conductors to be capacitively coupled, a "single port" or "multiport" circuit may be provided for high performance antennas.

In a preferred embodiment, the first and second center plates are first and second disks and the first and second surrounding plates are first and second rings. More preferably, the first and second rings are first and second continuous rings.

Moreover, a first inductor is preferably electrically connected between the first center plate and the first surrounding plate and a second inductor is preferably electrically connected between the second center plate and the second surrounding plate. A pair of first pads may be included, a respective one of which is on the first center plate and on the first surrounding plate so that the first inductor is electrically connected between the pair of first pads. A pair of second pads also may be included, a respective one of which is on the second center plate and on the second surrounding plate so that the second inductor is electrically connected between the pair of second pads. A preferred configuration of the present invention can provide reduced insertion loss over a wide band, while reducing unwanted stray couplings. In particular, the first inner conductor is electrically connected to the first center plate at a first position thereon and the first inductor is electrically connected to the first center plate at a second position that is remote from the first position. The second inner conductor is preferably electrically connected to the second center plate at a first position thereon and is preferably electrically connected to the second center plate at a second position that is remote from the first position.

More preferably, the first position on the first center plate is adjacent the second position on the second center plate and the second position on the first center plate is adjacent the first position on the first center plate. Even more preferably, the first shield conductor is electrically connected to the first surrounding plate at a first position thereon and the second shield conductor is electrically connected to the second surrounding plate at a second position thereon that is remote from the first position on the first surrounding plate. Most preferably, the first shield conductor is also electrically connected to the first surrounding plate at a first position thereon and the second shield conductor is electrically connected to the second surrounding plate at a second position thereon that is opposite the first position on the first surrounding plate. Thus, the first and second coaxial cables preferably emerge from the coupling system in opposite directions to reduce unwanted parasitic coupling. The first and second inductors preferably also are located at opposite locations from one another to reduce mutual inductance.

In another preferred aspect of the invention, the first center plate and the first surrounding plate define a first gap therebetween and the second center plate and the second surrounding plate define a second gap therebetween. The first shield conductor preferably extends into the first gap and the second shield conductor preferably extends into the second gap. More preferably, the first shield conductor extends midway into the first gap and the second shield conductor extends midway into the second gap.

The first center plate and the surrounding plate may be contained in a first housing. The second center plate and the second surrounding plate may be contained in a second housing. An alignment key may be provided on at least one of the first and second housings to facilitate alignment of the first housing and the second housing relative to one another on the respective first and second surfaces of the insulator.

The present invention may be used to couple an antenna to a radiotelephone through a window including an outside surface and an inside surface. Thus, as described above, the first coaxial cable includes a first inner conductor and a first shield conductor that are coupled to the antenna. The second coaxial cable includes a second inner conductor and a second shield conductor that are coupled to the radiotelephone. However, as described above, the present invention may be used in other coupling applications.

Methods according to the present invention may be used for coupling a first coaxial cable that includes a first inner conductor and a first shield conductor to a second coaxial cable that includes a second inner conductor and a second shield conductor, through an insulator that includes first and second insulator surfaces. A first center plate and a first surrounding plate are attached to the first insulator surface such that the first surrounding plate surrounds the first center plate on the first surface. The first center plate is electrically connected to the first inner conductor and the first surrounding plate is electrically connected to the first shield conductor. A second center plate and a second surrounding plate are attached to the second insulator surface such that the second surrounding plate surrounds the second center plate on the second surface, the first and second center plates are adjacent one another with the insulator therebetween, and the first and second surrounding plates are adjacent one another with the insulator therebetween. The second center plate is electrically connected to the second inner conductor and the second surrounding plate is electrically connected to the second shield conductor. The first center plate also may be inductively coupled to the first surrounding plate and the second center plate also may be inductively coupled to the second surrounding plate. Coaxial coupling systems and methods may thereby be provided to couple coaxial lines through an insulator with low insertion loss over a desired frequency range.

According to another aspect of the present invention, signals from an antenna outside a window may be coaxially coupled through the window, and the signals may be amplified adjacent and inside the window. The amplified signals are then provided to a radiotelephone remote from the window. By coaxially coupling the signals from the antenna through the window, high performance coupling may be provided from outside the window to inside the window. By amplifying the signals adjacent and inside the window, high performance may be obtained in low link margin situations, without the need to expose an electronic module to external vulnerabilities.

Systems according to this aspect of the invention include a through-the- window coaxial coupler that coaxially couples Radio Frequency (RF) signals between the inside and outside surfaces of the window. The through-the-window coaxial coupler includes an inside portion that mounts on the inside surface of a window, and an outside portion that mounts on the outside surface of the window and couples to an outside antenna. Preferably, coaxial couplers as were described above may be used. An inside electronic package couples to the inside portion of the through-the-window coaxial coupler, and is located adjacent the inside portion and remote from the radiotelephone. The inside electronic package includes a receive amplifier that amplifies RF signals that are received from the outside antenna via the through-the- window coaxial coupler and that provides the RF signals so amplified to the radiotelephone. In one embodiment, the electronic package also includes a transmit amplifier that amplifies second RF signals that are received from the radiotelephone and that provides the second RF signals so amplified to the antenna via the through-the- window coaxial coupler. The receive amplifier is preferably a low noise amplifier and the transmit amplifier is preferably a power amplifier. The inside electronic package may also include a switching system that switches between the receive amplifier and the transmit amplifier in response to the radiotelephone, to provide transmit and receive operations. The inside electronic package may also include a controller that controls the switching system in response to the radiotelephone. In another embodiment, the inside electronic package may include a wireless transceiver that wirelessly transmits and receives signals to and from a radiotelephone. Thus, only power may need to be supplied to the inside electronic package, but signal and/or control connections may be provided to the radiotelephone using wireless communications. One such wireless communications protocol that may be used is the well known "Bluetooth" protocol that defines a universal radio interface in the 2.45 GHz frequency band that enables wireless electronic devices to connect and communicate wirelessly via short-range, ad hoc networks. In this embodiment, some or all elements of a radiotelephone may be provided in the inside electronic package adjacent the inside portion of the coupler. Signals are then wirelessly relayed to a Bluetooth-compatible wireless electronic device that can provide a user interface.

Accordingly, signals to and from an antenna may be efficiently coupled through the window using coaxial couplers, which are coupled to an inside electronic package adjacent the window and remote from the radiotelephone. The inside electronic module may be connected to the radiotelephone using a coaxial cable and one or more control cables, or may be wirelessly connected to the radiotelephone. Accordingly, high performance systems and methods may be provided by coaxially coupling an antenna to a radiotelephone through a window and amplifying signals adjacent and inside the window.

Brief Description of the Drawings

Figure 1 illustrates systems and methods for coaxially coupling an antenna to a radiotelephone through a window by amplifying signals adjacent and inside the window according to the present invention. Figure 2 is a block diagram of an embodiment of an inside electronic package of Figure 1.

Figure 3 illustrates systems and methods according to the present invention, wherein the enclosure is a building. Figure 4 illustrates another embodiment of systems and methods that coaxially couple an outside antenna to a radiotelephone through a window according to the present invention.

Figure 5 is a block diagram of an embodiment of a wireless inside electronic package according to the present invention. Figures 6A, 6B and 6C are a top view, cross-sectional view and bottom view respectively, illustrating systems and methods for coupling an outside coaxial cable to an inside coaxial cable through a window according to the present invention.

Figures 7A-7C illustrate alternative arrangements of coaxial coupling systems and methods according to the present invention. Figures 8A-8B illustrate the use of coupling systems and methods according to the present invention to couple an antenna on the outside of a vehicle to a radiotelephone inside a vehicle.

Figure 9 graphically illustrates simulated attenuation loss for coupling systems and methods according to the present invention. Figure 10 graphically illustrates simulated return loss for coupling systems and methods according to the present invention.

Figure 11 is a Smith Chart that graphically illustrates simulated input impedance for coupling systems and methods according to the present invention.

Figure 12 is an equivalent circuit of coupling systems and methods according to the present invention.

Figure 13 graphically illustrates measured data for coupling systems and methods according to the present invention.

Detailed Description of Preferred Embodiments The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thickness of layers and regions are exaggerated for clarity. Like numbers refer to like elements throughout. It will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present.

Referring now to Figure 1 , systems and methods for coaxially coupling an antenna to a radiotelephone through a window by amplifying signals adjacent and inside the window according to the invention will now be described. As shown in Figure 1, an outside antenna 102 is provided outside an enclosure such as a vehicle 100. However, it will be understood that the enclosure may also be a building, as will be described below. It will also be understood that more than one antenna may be provided, as will be described below. The outside antenna 102 outside the vehicle 100 is coupled to a radiotelephone 114 inside the vehicle 100 using a through-the- window coaxial coupler 106 and an inside electronic package 110. The through-the- window coaxial coupler 106 coaxially couples Radio Frequency (RF) signals between the inside surface 104a and outside surface 104b of the window 104. The through- the-window coaxial coupler 106 includes an inside portion 106a that mounts on the inside surface 104a and an outside portion 106b that mounts on the outside surface 104b. The outside portion 106b is coupled to the outside antenna 102 either directly or via a coupling shaft 108 that can include a coaxial cable between the outside portion 106b and the outside antenna 102. A preferred design of a coaxial coupler 106 will be described in detail below. Still continuing with the description of Figure 1, an inside electronic package

110 couples the inside portion 106a to a radiotelephone 114, and is located adjacent the inside portion 106a and remote from the radiotelephone 114. As will be described in detail below, the electronic package preferably includes a receive amplifier that amplifies RF signals that are received from the outside antenna 102 via the through- the-window coaxial coupler 106 and that provides the RF signal so amplified to the radiotelephone 114. The electronic package also may include a transmit amplifier that amplifies RF signals from the radiotelephone 114 before being passed through the coaxial coupler. The transmit amplifier may raise the transmitted power from the outside antenna 102 to desired levels, as is well known in the art. In Figure 1, a first cable 116 is used to couple the inside portion 106a and the inside electronic package 110, and a second cable 112 is used to couple the electronic package 110 and the radiotelephone 114. The first cable 116 preferably comprises coaxial cable and the second cable 112 preferably comprises coaxial cable. It will be understood that the first cable 116 may be omitted and the internal electronic package 110 may be formed integral with the inside portion 106a. Alternatively, cables other than coaxial cable may be used to couple the inside portion 106a to the electronic module 110. Moreover, the second cable 112 may also include a control cable to couple the inside electronic package 110 and the radiotelephone 114 and/or a power cable to supply power to the inside electronic package 110. Alternatively control and/or power may be provided via the coaxial cable. In yet another alternative, described in detail below, a wireless connection may be provided between the inside electronic package 110 and the radiotelephone 114.

Figure 2 is a block diagram of an embodiment of an inside electronic package 110 according to the present invention. As shown in Figure 2, the inside electronic package 110 includes a receive amplifier such as a Low Noise Amplifier (LNA) 202 that amplifies RF signals that are received from the outside antenna 102 via the through-the-window coaxial coupler 106 and the first cable 116, and provides the RF signals so amplified to the radiotelephone 114. Associated filters 204a and 204b may be provided as is well known to those having skill in the art.

The inside electronic package 110 may also include a transmit amplifier such - as an RF power amplifier 212 that amplifies second RF signals that are received from the radiotelephone 114 and that provide the second RF signals so amplified to the antenna 102 via the through-the-window coaxial coupler 106. Associated filters 214a, 214b may be provided as is well known to those skilled in the art. By including the transmit amplifier 212, precise control of transmit power may be obtained.

As also shown in Figure 2, the inside electronic package 110 may include a switching system including two switching elements 206a, 206b that switch between the low noise amplifier 202 and the power amplifier 212 to provide half duplex communications, under control of a controller 208 that is responsive to the radiotelephone 114. By including the controller 208, precise timing of transmit bursts may be obtained. Finally, as shown in Figure 2, the second cable 112 between the radiotelephone 114 and the inside electronic module 110 may include a coaxial cable 112a that carries the RF signals, one or more power cables 112b that provides power to the power consuming elements of the inside electronic package and one or more control signal cables 112c that can be applied to the controller 208.

Figure 3 illustrates systems and methods according to the present invention, wherein the enclosure is a building 300. As shown in Figure 3, a through-the-window coaxial coupler 106 coaxially couples RF signals between the inside and outside surfaces 104a and 104b respectively of a window 104. The through-the-window coaxial coupler 106 includes an inside portion 106a that mounts on the inside surface 104a, and an outside portion 106b that mounts on the outside surface 104b. In Figure 3, a duplexer 218 is included outside the window 104 so that the coaxial coupler 106 may be coupled to more than one antenna 202a, 202b via coupling shafts 208a, 208b respectively. For example, the antenna 202a may be a transmit antenna, and the antenna 202b may be a receive antenna. The design of the duplexer 208 to couple to multiple antennas 202a, 202b is well known to those having skill in the art, and need not be described further herein. The coaxial coupler can provide a single port connection that can facilitate the use of a duplexer 218 to provide a multiport connection to multiple antennas 202a, 202b.

Finally, as shown in Figure 3, an inside electronic package 110 is coupled to the inside portion 106a, and is also coupled to a radiotelephone 114 via the second cable 112. The design of the inside electronic package 110 may be similar to that of Figure 2, and need not be described again.

Referring now to Figure 4, another embodiment of systems and methods that coaxially couple an outside antenna to a radiotelephone through a window according to the present invention is illustrated. As shown in Figure 4, the link between the inside electronic package 110' and the radiotelephone 114' is a wireless link 406 using a first antenna 402 on the internal electronic package 110' and a second antenna 404 on the radiotelephone 114'. Accordingly, only a power connection may need be provided to the wireless inside electronic package 110'. Control and signal connections may be provided via the wireless link 406.

The wireless inside electronic package 110' may contain amplifiers, filters, switches and control circuits similar to that described in connection with Figure 2. However, rather than a second cable 112, a short-range radio frequency transceiver may be used. In this embodiment, the radiotelephone 114' may be a conventional cellular satellite or other radiotelephone. Alternatively, the radiotelephone 114' may be a short range radiotelephone such as a cordless radiotelephone or a short range transceiver operating under Bluetooth protocol as will be described in detail below. In a preferred aspect of the wireless inside electronic package 110', all of the mobile transceiver RF circuits, digital signal processing circuits and control processor circuits may be included in the wireless inside electronic package 110'. Then, the radiotelephone 114' may be any kind of wireless electronic device, such as a laptop computer or a fax machine, as well as a cellular telephone or a cordless telephone. The radiotelephone 114' may be a wireless input/output electronic device that includes a microphone, speaker and/or data port. It will also be understood that the wireless link 406 may use infrared or other forms of wireless links.

Figure 5 is a block diagram of an embodiment of a wireless inside electronic package 110' that uses wireless technology to transmit and receive external radiotelephone signals to and from the radiotelephone. As shown in Figure 5, the wireless inside electronic package 110' includes a cellular/satellite portion 502 and a short-range wireless portion 504.

The cellular/satellite portion 502 may include a cellular/satellite transceiver 512, a Digital Signal Processor (DSP) 514 and a controller 516, such as a microprocessor controller. The transceiver is coupled to inner portion 106a of the coaxial coupler 106 via the first cable 116. It will be understood by those having skill in the art that the cellular/satellite portion 502 preferably is compatible with the cellular/satellite system that is being interfaced to, via the outside antenna 102. The short-range wireless portion 504 can include a short-range wireless transceiver 522 and a controller 526. The short-range wireless transceiver 522 transmits and receives messages to and from the radiotelephone 114' via the first antenna 402 and the wireless link 406.

The short-range wireless portion 504 can control the cellular/satellite portion 502. The short-range wireless transceiver may be an infrared transceiver or a cordless RF transceiver, such as are used with cordless telephones. In a preferred embodiment, the short-range wireless portion includes a Bluetooth transceiver. As is well known to those having skill in the art, Bluetooth technology provides a universal radio interface in the 2.45 GHz frequency band that enables portable electronic devices to connect and communicate wirelessly via short-range ad hoc networks. Bluetooth technology is described for example in Haartsen, "Bluetooth-The Universal Radio Interface for Ad Hoc, Wireless Connectivity", Ericsson Review No. 3, 1998, pp. 110-117, the disclosure of which is hereby incorporated herein by reference. This type of protocol may be used for individuals in a conventional passenger vehicle, as well as taxi service, limousine service, and including bus and other multi-unit enclosures. A preferred embodiment of a through-the-window coaxial coupler 106 according to the present invention will now be described. Figures 6A, 6B and 6C are a top view, cross-sectional view and bottom view, respectively, of systems and methods for coupling a first coaxial cable to a second coaxial cable through an insulator. As shown in Figures 6A-6C, coupling systems and methods 106 couple an outside coaxial cable 12 that includes a first inner conductor 14 and a first shield conductor 16 to a first coaxial cable 116 including a second inner conductor 24 and a second shield conductor 26, through a windshield or other window 104 that includes outside and inside window surfaces 104a and 104b respectively. As is well known to those having skill in the art, each coaxial cable also may include an inner insulator and an outer jacket. A first center plate 42 and a first surrounding plate 44 are adapted for attachment to the outside window surface 104b using adhesive, fasteners and/or other conventional attaching means, such that the first surrounding plate 44 surrounds the first center plate 42 on the outside surface 104b. The first center plate 42 is electrically connected to the first inner conductor 14 using solder 34a and/or other conventional electrical connecting means. The first surrounding plate 44 is electrically connected to the first shield conductor 16 using solder 34b and/or other conventional electrical connecting means.

A second center plate 52 and a second surrounding plate 54 also are adapted for attachment to the inside window surface 104a using adhesive, fasteners and/or other conventional attaching means such that the second surrounding plate 54 surrounds the second center plate 52 on the inside window surface 104a. As shown, the first and second center plates 42 and 52 respectively are adjacent one another with the window 104 therebetween. Also, the first and second surrounding plates 44 and 54 are adjacent one another with the window 104 therebetween. The second center plate 52 is electrically connected to the second inner conductor 24 using solder 34c and/or other conventional electrical connecting means. The second surrounding plate 54 is electrically connected to the second shield conductor 26 using solder 34d and/or other electrical connecting means. As shown in Figures 6A-6C, the first and second center plates 42 and 52 respectively, preferably are first and second disks. The first and second surrounding plates 44 and 54 respectively, preferably are first and second rings. As also shown in Figures 6A-6C, the first and second rings 44 and 54 respectively, preferably are first and second continuous rings. However, polygonal shaped center plates and surrounding plates, including but not limited to square shaped center plates and surrounding plates may be used, and gaps may be present in the center plates and/or surrounding plates so that they are not continuous.

A first inductor 46 is electrically connected between the first center plate 42 and the first surrounding plate 44 using solder 44e, 44f and/or other conventional electrical connecting means. A second inductor 56 is electrically connected between the second center plate 52 and the second surrounding plate 54 using solder 54g, 54h and/or other conventional electrical connecting means. More than one inductor also may be electrically connected between a center plate and a surrounding plate as will be described below.

The coaxial cables 12 and 116 and the inductors 46 and 56 may be electrically connected to the center plates and surrounding plates at any arbitrary position thereon. However, preferably, they are connected as illustrated in Figures 6A-6C to reduce and preferably minimize unwanted couplings and parasitics. More specifically, the first inner conductor 14 preferably is electrically connected to the first center plate 42 at a first position 42a thereon and the first inductor 46 preferably is electrically connected to the first center plate 42 at a second position 42b that is remote from the first position. The second inner conductor 24 preferably is electrically connected to the second center plate 52 at a first position 52a thereon and the second inductor 56 preferably is electrically connected to the second center plate 54 at a second position 52b that is remote from the first position 52a. Moreover, the first position 42a on the first center plate 42 preferably is adjacent the second position 52b on the second center plate 52. The second position 42b on the first center plate 42 preferably is adjacent the first position 52a on the second center plate 52. The first shield conductor 16 preferably is electrically connected to the first surrounding plate 44 at a first position 44a thereon. The second shield conductor 26 preferably is electrically connected to the second surrounding plate 54 at a second position 54a thereon that is remote from, and preferably opposite, the first position 44a on the first surrounding plate 44. Moreover, the first inductor 46 preferably is electrically connected to the first surrounding plate 44 at a second position 44b that is remote from, and more preferably opposite, the first position 44a. The second inductor 56 is preferably connected to the second surrounding plate 54 at a second position 54b that is remote from, and more preferably opposite, the first position 54a. Thus, as shown, the first and second coaxial cables preferably emerge from opposite directions and the first inductors preferably are located remote from one another.

As also shown in Figures 6A-6C, the first center plate 42 and the first surrounding plate 44 preferably define a first gap 48 therebetween and the second center plate 52 and the second surrounding plate 54 preferably define a second gap 58 therebetween. The first shield conductor 16 preferably extends into the first gap and the second shield conductor 26 preferably extends into the second gap 58. More preferably, as shown, the first shield 16 preferably extends midway into the first gap 48 and the second shield 26 preferably extends midway into the second gap 58.

Still referring to Figures 6A-6C, the first and second positions on each of the first center plate 42, first surrounding plate 44, second center plate 52 and second surrounding plate 54 may be defined using a tab such as a projecting tab. The tab can facilitate solder connection at the appropriate place on the center plates and surrounding plates. The tabs may be raised and may have a shape that enhances soldering. Multiple layers may be used for the tabs. However, it will be understood that the first and second positions on each of the center plates and surrounding plates need not be defined by specific features such as tabs.

Finally, a first housing 50 contains the first center plate 42 and the first surrounding plate 44. A second housing 60 contains the second center plate 52 and the second surrounding plate 54. The first housing 50 also may contain the outside coaxial cable 12 and a first coaxial cable connector 18. Similarly, the second housing 60 may also contain the first coaxial cable 116 and a second coaxial cable connector 28. It will be understood however, that the coaxial cable connectors 18 and 28 need not be contained within or be adjacent the housings, and may be eliminated entirely. Similarly, the coaxial cables 12 and 116 themselves may be outside the housings 50 and 60.

In order to facilitate alignment of the first housing 50 and the second housing 60 to one another on opposite surfaces of the window 104, an alignment key such as a pair of dimples 36a, 36b may be provided on a respective housing 50 and 60. Alternatively, alignment keys 36a, 36b may be painted or otherwise inscribed on the housings 50 and 60 and also may be provided by virtue of the overall shape of the housings 50 or 60. Alternatively, alignment keys need not be provided at all. The materials and dimensions of the center plates, surrounding plates, inductors and housings may be varied depending on a particular application. However, the center plates and surrounding plates preferably comprise stamped copper and the housing preferably comprises plastic. The surrounding plates may have an outer diameter of about 45mm and an inner diameter of about 20mm. The center plate may have a diameter of about 15mm so that a 2.5mm gap is present. The plates may be less than 1mm thick. The housings should preferably maintain a clear area above and below of about 1cm. The inductors may be meandering line inductors rather than coils.

It will be understood that more than one inductor may be used to couple a respective center plate to a respective surrounding plate. Alternative arrangements of center plates, surrounding plates, and positioning of coaxial cables and inductors are shown in Figures 7A-7C. The inductance may be distributed to reduce the difficulty of fabricating small inductor values. Thus, for example, four-20 nH coils may be used to achieve a 5 nH coil.

Figures 8A-8B illustrate the use of coupling systems and methods according to the present invention to couple an antenna on the exterior of a vehicle to a radiotelephone within a vehicle. As shown in Figure 8A, coupling 106 is used to couple a first coaxial cable 108 that is connected to an antenna such as a quadrifilar helical antenna 102 on the roof of a vehicle 100, through the rear window 104 of the vehicle 100, to a second coaxial cable 112 that itself is coupled to a radiotelephone 114 within the vehicle 100. Figure 8B illustrates a similar embodiment to Figure 8 A except that a patch antenna 102' is used on the roof of the vehicle 100. It will be understood that other antennas may be used and other mounting positions for couplers, antennas and transceivers such as radiotelephones may be used. Coupling through windows other than the rear windshield also may be used.

As described above, the present invention may be used to coaxially couple two or more conductors through a window. A two-conductor circuit can provide for signal excitation and signal return to complete a circuit. This is known as a "single- port". Components having input ports and output ports, known as "two ports" or "multiports" may be cascaded from single ports to modify the signal delivered to the output ports. Examples of such two-ports are transmission lines, duplexers, filters, as well as quadrature matching networks. A low loss, two conductor coupling according to the invention can enable these above-referred components to become part of the external network.

Additional design considerations for coupling systems and methods according to the present invention will now be provided. As was described, a center conductor capacitor plate is formed on each side of the glass together with an annular shield conductor capacitor plate around the center conductor plate. On either side of the capacitor plates, shunt inductors are placed from the center capacitor plate to the shield capacitor plate. Thus, a high-pass Pi-circuit is formed which can be equivalent to a short portion of transmission line.

There are several factors that may be considered in the design for a given frequency band. For example, for L-Band (1500-1700MHz), the capacitor plates are somewhat large at the desired wavelength and may not be considered strictly as a lumped element. That is, there is a distributed nature to the capacitor due to its size. Moreover, coaxial cable is unbalanced so the capacitance of the surrounding plates ^"rrTay^~be^~ esI eα^b^~be largerlhaiπhe^~c teFplatesr rt^~aιs^~o^~may ^~aαvahtageoύs to provide extra isolation space between the center plates and the shield plates. Further, the coaxial cables on each side of the glass should be physically isolated from each other in order to reduce extraneous conduction modes. The position of the inductors also may be selected to reduce propagation of extraneous conduction modes. Beyond these positioning guidelines, there may be relatively good tolerance to component value variations because there need not be narrowly tuned resonators in the coupler.

Couplers according to the invention can support the feed line requirements for circularly polarized antennas that use coaxial or at least two wire connections to the radiating structure. For example, an L-Band transceiver operates between 1500 and 1700 MHz. The present invention may be scaled for this frequency range. Below 1500 MHz there may be gradually increasing transmission loss due to the high-pass Pi-circuit. Above 1700 MHz the transmission loss may eventually increase due to other microwave modes that can be propagated via the structure. The invention also can be scaled to higher or lower frequency ranges. Lower frequency ranges may include cellular radiotelephone frequency bands. Higher frequency ranges may include for example the PCS ranges around 1800 and 1900 MHz. Satellite radiotelephone transceivers in the lower S band also may be used with the present invention. In order to design the circuit, an assumption may be made that the energy is to be sourced from a 50Ω coaxial transmission line and the energy is to be delivered to a 50Ω transmission line. An automotive windshield generally has a nominal dielectric of 7.5 at room temperature. Thus, a square centimeter area may have a capacitance of 1.24 pF/cm . Capacitance may be treated as part of a lumped element transmission line equivalent.

A simulation of a coupler according to the present invention was performed for L-Band. This simulation was based on the coaxial center window capacitance of 2.1 pF and shield window capacitance of 15 pF. The shunt inductors on each side of the window across the center to shield conductors had a value of 9.8 nH. In all component cases, component Q values were set at 50. The Q values contribute to a loss in the network.

Figure 9 graphically illustrates simulated attenuation loss from 1500 MHz through 1700 MHz. The network is basically a high pass structure with a shunt inductor, series capacitor and shunt inductor. The cutoff frequency of the network may be determined by the value of the series capacitor. The series capacitor was chosen with a sense of a tolerable size and in consideration of the shield capacitor that surrounds the center capacitor. In the case of the series capacitor, 2 nH of series inductance was provided for. Figure 9 illustrates that a simulated insertion loss of about -0.3 dB may be obtained for values between 1500 MHz and 1700 MHz. Figure 10 graphically illustrates return loss that shows a very good match over the frequency range of interest. Figure 11 is a Smith Chart that shows the input impedance with the network terminated at 50Ω. Accordingly, Figures 9-11 indicate that a transmission loss of less than 0.5 dB may be realized for L-Band coaxial coupling.

Figure 12 is an equivalent circuit of couplers according to the present invention. M indicates mutual coupling between elements. The first and second surrounding plates 44 and 54 respectively are broken into semicircles for purposes of the equivalent circuit. Actual measurements were taken on a coupler according to the present invention using the above described parameters. In these measurements, the calibration used a small connector for the through connection. In this way, the loss of an equivalent length of RG-223 coaxial cable may be subtracted from the coupling with cable measurement. The coupling loss values in the right hand column of the following table result from these measurements.

TABLE

Measured data from 1.0 to 3.0 GHz is graphically illustrated in Figure 13.

This data includes a length of coaxial cable similar to the coupling with cable loss data above. The data shows the nature of the high pass filter up to about 2 GHz. The distributed nature of the coupling tends to cause a low pass relation to the curve toward 3 GHz. A wide bandwidth was therefore obtained, with low insertion loss. Accordingly, coupling systems and methods of the present invention can allow communication signals to pass with low insertion loss, over a desired frequency range, between an antenna mounted outside a window and a radio transceiver mounted inside the window. Transmission takes place via a coaxial transmission line on each side of the window. Accordingly, single-port or multiport coupling may take place.

As also described above, the electronic package preferably contains a low noise amplifier 202. A figure of merit of a radiotelephone to receive signals from an earth orbiting satellite may be determined principally by the ratio of the antenna gain to the receiver system noise temperature. The receiver system noise temperature is the sum of the receiver noise temperature and the antenna noise temperature.

Generally, the reference point for assessing this ratio is at the input terminals of the receiver system. When the antenna is separated from the receiver by a transmission line, the transmission line losses are generally included in the antenna temperature according to known formulas, which are described for example in Chapter 17, section 3 of "Antennas, Second Edition", by John D. Kraus, McGraw-Hill, 1998. The present invention can use this theory in a manner advantageous to mobile communication transceivers used for communication with earth orbiting communication satellites to conveniently satisfy the cable routing requirements while reducing and preferably minimizing the external exposed cabling outside the vehicle. Accordingly, the present invention can provide efficient coupling from an outside antenna to an inside radiotelephone through a window. Moreover, the invention can provide enabling technology that can allow other products to be used in vehicular and/or building environments that may have been too awkward to have been used in the past.

In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims

What is Claimed is;

1. A system that couples a first coaxial cable that includes a first inner conductor and a first shield conductor to a second coaxial cable that includes a second inner conductor and a second shield conductor, through an insulator that includes first and second insulator surfaces, the system comprising: a first center plate and a first surrounding plate that are adapted for attachment to the first insulator surface such that the first surrounding plate surrounds the first center plate on the first insulator surface, the first center plate being electrically connected to the first inner conductor and the first surrounding plate being electrically connected to the first shield conductor; and a second center plate and a second surrounding plate that are adapted for attachment to the second insulator surface such that the second surrounding plate surrounds the second center plate on the second insulator surface, the first and second center plates are adjacent one another with the insulator therebetween and the first and second surrounding plates are adjacent one another with the insulator therebetween, the second center plate being electrically connected to the second inner conductor and the second surrounding plate being electrically connected to the second shield conductor.

2. A system according to Claim 1 wherein the first and second center plates are first and second disks and wherein the first and second surrounding plates are first and second rings.

3. A system according to Claim 2 wherein the first and second rings are first and second continuous rings.

4. A system according to Claim 1 further comprising a first inductor that is electrically connected between the first center plate and the first surrounding plate and a second inductor that is electrically connected between the second center plate and the second surrounding plate.

5. A system according to Claim 4: wherein the first inner conductor is electrically connected to the first center plate at a first position thereon and wherein the first inductor is electrically connected to the first center plate at a second position that is remote from the first position; and wherein the second inner conductor is electrically connected to the second center plate at a first position thereon and wherein the second inductor is electrically connected to the second center plate at a second position that is remote from the first position.

6. A system according to Claim 5 wherein the first position on the first center plate is adjacent the second position on the second center plate and wherein the second position on the first center plate is adjacent the first position on the second center plate.

7. A system according to Claim 6 wherein the first shield conductor is electrically connected to the first surrounding plate at a first position thereon and wherein the second shield conductor is electrically connected to the second surrounding plate at a second position thereon that is remote from the first position on the first surrounding plate.

8. A system according to Claim 7 wherein the first shield conductor is electrically connected to the first surrounding plate at a first position thereon and wherein the second shield conductor is electrically connected to the second surrounding plate at a second position thereon that is opposite the first position on the first surrounding plate.

9. A system according to Claim 1 wherein the first shield conductor is electrically connected to the first surrounding plate at a first position thereon and wherein the second shield conductor is electrically connected to the second surrounding plate at a second position thereon that is not adjacent the first position on the first surrounding plate.

10. A system according to Claim 1 wherein the first shield conductor is electrically connected to the first surrounding plate at a first position thereon and wherein the second shield conductor is electrically connected to the second surrounding plate at a second position thereon that is opposite the first position on the first surrounding plate.

11. A system according to Claim 1 wherein the first center plate and the first surrounding plate define a first gap therebetween, wherein the second center plate and the second surrounding plate define a second gap therebetween, wherein the first shield conductor extends into the first gap and wherein the second shield conductor extends into the second gap.

12. A system according to Claim 11 wherein the first shield conductor extends midway into the first gap and wherein the second shield conductor extends midway into the second gap.

13. A system according to Claim 4 further comprising: a pair of first pads, a respective one of which is on the first center plate and on the first surrounding plate, the first inductor being electrically connected between the pair of first pads; and a pair of second pads, a respective one of which is on the second center plate and on the second surrounding plate, the second inductor being electrically connected between the pair of second pads.

14. A system according to Claim 1 further comprising: a first housing that contains the first center plate and the first surrounding plate; a second housing that contains the second center plate and the second surrounding plate; and an alignment key on at least one of the first and second housings that facilitates alignment of the first housing and the second housing relative to one another on the respective first and second surfaces of the insulator.

15. A system according to Claim 1 wherein the insulator is a window, wherein the first insulator surface is an outside surface and wherein the second insulator surface is an inside surface, the system further comprising: an inside electronic package that couples the second inner conductor and the second shield conductor to a radiotelephone, the inside electronic package being located adjacent the inside surface and remote from the radiotelephone, the inside electronic package comprising a receive amplifier that amplifies RF signals that are received from an outside antenna that is coupled to the first inner conductor and the first shield conductor, and that provides the RF signals so amplified to the radiotelephone.

16. A system according to Claim 15 wherein the inside electronic package further comprises a transmit amplifier that amplifies second RF signals that are received from the radiotelephone and that provides the second RF signals so amplified to the second inner conductor and the second shield conductor.

17. A system according to Claim 16 wherein the inside electronic package further comprises a switching system that switches between the receive amplifier and the transmit amplifier in response to the radiotelephone.

18. A system according to Claim 17 wherein the inside electronic package further comprises a controller that controls the switching system in response to the radiotelephone.

19. A system according to Claim 15 further comprising a duplexer that is coupled to the first inner conductor and the first shield conductor and that couples to the outside antenna and at least a second outside antenna.

20. A system according to Claim 16 wherein the inside electronic package comprises a first wireless transceiver and a second wireless transceiver that are coupled to one another, the first wireless transceiver comprising the transmit amplifier and the receive amplifier, the first wireless transceiver wirelessly transmitting and receiving external radiotelephone signals using the outside antenna, the second wireless transceiver wirelessly transmitting and receiving internal radiotelephone signals to and from the radiotelephone.

21. A system according to Claim 16 wherein the inside electronic package comprises a wireless transceiver including the transmit amplifier and the receive amplifier, that wirelessly transmits and receives external radiotelephone signals using the outside antenna, and that wirelessly transmits and receives internal radiotelephone signals to and from the radiotelephone.

22. A system according to Claim 20 wherein the second wireless transceiver comprises a short-range wireless transceiver operating under Bluetooth protocol.

23. A system according to Claim 15 further comprising a third coaxial cable that couples the inside electronic package to the radiotelephone.

24. A system according to Claim 15 further comprising a third coaxial cable and a control cable that couple the inside electronic package to the radiotelephone.

25. A method for coupling a first coaxial cable that includes a first inner conductor and a first shield conductor to a second coaxial cable that includes a second inner conductor and a second shield conductor, through an insulator that includes first and second insulator surfaces, the method comprising the steps of: attaching a first center plate and a first surrounding plate to the first insulator surface such that the first surrounding plate surrounds the first center plate on the first insulator surface; electrically connecting the first center plate to the first inner conductor and the first surrounding plate to the first shield conductor; attaching a second center plate and a second surrounding plate to the second insulator surface such that the second surrounding plate surrounds the second center plate on the second insulator surface, the first and second center plates are adjacent one another with the insulator therebetween and the first and second surrounding plates are adjacent one another with the insulator therebetween; and electrically connecting the second center plate to the second inner conductor and the second surrounding plate to the second shield conductor.

26. A method according to Claim 25 further comprising the steps of: inductively coupling the first center plate to the first surrounding plate; and inductively coupling the second center plate to the second surrounding plate.

27. A method according to Claim 25 wherein the first shield conductor is electrically connected to the first surrounding plate at a first position thereon and wherein the second shield conductor is electrically connected to the second surrounding plate at a second position thereon, and wherein the step of attaching a second center plate and a second surrounding plate to the second insulator surface comprises the step of attaching the second center plate and the second surrounding plate to the second insulator surface such that the second position is not adjacent the first position on the first surrounding plate.

28. A method according to Claim 25 wherein the first shield conductor is electrically connected to the first surrounding plate at a first position thereon and wherein the second shield conductor is electrically connected to the second surrounding plate at a second position thereon, and wherein the step of attaching a second center plate and a second surrounding plate to the second insulator surface comprises the step of attaching the second center plate and the second surrounding plate to the second insulator surface such that the second position is opposite the first position on the first surrounding plate.

29. A method according to Claim 25: wherein the step of attaching a first center plate and a first surrounding plate to the first insulator surface comprises the step of attaching a first housing that contains the first center plate and the first surrounding plate to the first surface such that the first surrounding plate surrounds the first center plate on the first insulator surface; wherein the step of attaching a second center plate and a second surrounding plate to the second insulator surface comprises the step of attaching a second housing that contains the second center plate and the second surrounding plate to the second insulator surface such that the second surrounding plate surrounds the second center plate on the second insulator surface; and wherein at least one of the steps of attaching is preceded by the step of aligning the first housing and the second housing relative to one another on the respective first and second surfaces of the insulator.

30. A method according to Claim 25 further comprising the step of coupling at least two ports to at least one of the first and second coaxial cables.

31. A method according to Claim 25 further comprising the steps of: connecting the second inner conductor and the second shield conductor to an amplifier adj acent the insulator; and coupling the amplifier to a radiotelephone remote from the insulator.

32. A method according to Claim 31 wherein the coupling step comprises the step of coupling the amplifier to a radiotelephone remote from the insulator via a third coaxial cable.

33. A method according to Claim 31 wherein the coupling step comprises the step of wirelessly coupling the amplifier to a radiotelephone remote from the insulator.

34. A method according to Claim 33 wherein the wirelessly coupling step is performed using Bluetooth protocol.