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Title:
OMNIDIRECTIONAL PLANAR ANTENNA
Document Type and Number:
WIPO Patent Application WO/2002/093691
Kind Code:
A1
Abstract:
A planar omni-directional antenna system including a planar antenna and a related quadrature phase shifter implemented on printed circuit boards (PCBs) having differing properties. The planar antenna includes four quarter wavelength, folded dipole sections organized in pairs and may be implemented on a single-sided inexpensive first PCB. The quadrature phase shifter is implemented on a more expensive multilayer second PCB. A radio transceiver and other electronics may be implemented on the second PCB or on a third PCB. The system reduces cost and improves system reliability because coaxial or like connectors of varying material and installation quality are not required between the planar antenna and the quadrature phase shifter. The planar antenna transmits radio frequency signals in an omni-directional pattern and is capable of receiving signals from remote dipole antennas positioned in arbitrary physical orientations. The quadrature phase shifter provides both phase shifting functions and also converts an unbalanced radio transceiver output signal into a balanced input signal to the planar antenna. The quadrature phase shifter matches and converts impedances using hybrid dividers, impedance converters and other techniques utilizing the electrical properties of PCBs.

Inventors:
PACHAL ED (CA)
SOBOTA JOHN F (CA)
Application Number:
PCT/CA2002/000496
Publication Date:
November 21, 2002
Filing Date:
April 12, 2002
Export Citation:
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Assignee:
ELEVEN ENGINEERING INC (CA)
PACHAL ED (CA)
SOBOTA JOHN F (CA)
International Classes:
H01Q9/06; H01Q9/26; H01Q21/26; H01Q23/00; (IPC1-7): H01Q21/26; H01Q9/26; H01Q9/06
Foreign References:
FR2429504A11980-01-18
US4647942A1987-03-03
US6069586A2000-05-30
Other References:
NESIC A ET AL: "Wideband printed antenna with circular polarization", ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM, 1997. IEEE., 1997 DIGEST MONTREAL, QUE., CANADA 13-18 JULY 1997, NEW YORK, NY, USA,IEEE, US, 13 July 1997 (1997-07-13), pages 1882 - 1885, XP010247203, ISBN: 0-7803-4178-3
MACDONALD J A ET AL: "Axial ratio optimization of an array of crossed-dipoles using phasing posts", DIGEST OF THE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM. SEATTLE, WA., JUNE 19 - 24, 1994, NEW YORK, IEEE, US, vol. 3, 20 June 1994 (1994-06-20), pages 1252 - 1255, XP010142261, ISBN: 0-7803-2009-3
Attorney, Agent or Firm:
Garwasiuk, Helen (Tower Two Edmonton, Alberta T5J 3R8, CA)
Download PDF:
Claims:
WHAT IS CLAIMED IS:
1. A planar, omnidirectional antenna system, comprising: a planar antenna implemented on a first printed circuit board for radiating and receiving electromagnetic signals, wherein said antenna has four quarter wavelength, folded dipole sections organized in pairs; a radio transceiver; and a quadrature phase shifter implemented on a second printed circuit board and electrically connected with both of said planar antenna and said radio transceiver, wherein said quadrature phase shifter comprises a phase shifting hybrid power divider and a plurality of transformer elements.
2. A system as recited in Claim 1 wherein the orientation of said system does not change the system ability to receive and transmit signals equally well to a remote dipole antenna.
3. A system as recited in Claim 1, further comprising at least one pair of phasor passive radiator elements associated with said folded dipole sections on the planar antenna, wherein said phasor passive radiator elements assist to shape the electromagnetic field into a substantially omnidirectional pattern.
4. A system as recited in Claim 1, wherein the second printed circuit board is mounted substantially at a right angle relative to the first printed circuit board and wherein the quadrature phase shifter conducts and modifies the signals to and from said planar antenna.
5. A system as recited in Claim 1, wherein said second printed circuit board is electrically connected with a third printed circuit board and wherein the radio transceiver is implemented on the third printed circuit board.
6. A system as recited in Claim 1, wherein the quadrature phase shifter and the radio transceiver are both implemented on the second printed circuit board.
7. A system as recited in Claim 1, wherein said quadrature phase shifter is configured to divide an input signal from the radio transceiver into four output signals and to shift the phases of the output signals by zero, ninety, one hundred eighty and two hundred seventy degrees relative to the input signal from the radio transceiver.
8. A system as recited in Claim 7, wherein said quadrature phase shifter is configured for a particular operating frequency range and has an input impedance for that operating frequency range that is efficiently matched to the input impedance of the radio transceiver and the input impedance for the planar antenna.
9. A system as recited in Claim 7, wherein said quadrature phase shifter is comprised of stripline segments contained on a plurality of layers of the second printed circuit board and wherein the plurality of layers are capacitively coupled.
10. A system as recited in Claim 1, wherein such planar antenna is configured for a particular operating frequency range and wherein such operating frequency range can be changed by adjusting the antenna dimensions while considering the dielectric properties of the printed circuit board.
11. A system as recited in Claim 1 wherein one or both of the printed circuit boards is constructed of a flexible material upon which conductive strips have been placed.
12. A planar, omnidirectional antenna system, comprising: a planar antenna implemented on a first printed circuit board for radiating and receiving electromagnetic signals, wherein said antenna has four quarter wavelength, folded dipole sections organized in pairs; a radio transceiver implemented on a second printed circuit board; and a quadrature phase shifter implemented on the second printed circuit board and electrically connected with both of said planar antenna and said radio transceiver, wherein said quadrature phase shifter comprises an impedance converter and a plurality of transformer elements.
13. A system as recited in Claim 12 wherein the orientation of said system does not change the system ability to receive and transmit signals equally well to a remote dipole antenna.
14. A system as recited in Claim 12, further comprising at least one pair of phasor passive radiator elements associated with said folded dipole sections on the planar antenna, wherein said phasor passive radiator elements assist to shape the electromagnetic field into a substantially omnidirectional pattern.
15. A system as recited in Claim 12, wherein the second printed circuit board is mounted substantially at a right angle relative to the first printed circuit board and wherein the quadrature phase shifter conducts and modifies the signals to and from said planar antenna.
16. A system as recited in Claim 12, wherein said second printed circuit board is electrically connected with a third printed circuit board and wherein electronics other than the radio transceiver are implemented on the third printed circuit board.
17. A system as recited in Claim 12, wherein the quadrature phase shifter, the radio transceiver and electronics other than the radio transceiver are all implemented on the second printed circuit board.
18. A system as recited in Claim 12, wherein said quadrature phase shifter is configured to divide an input signal from the radio transceiver into four output signals and to shift the phases of the output signals by zero, ninety, one hundred eighty and two hundred seventy degrees relative to the input signal from the radio transceiver.
19. A system as recited in Claim 18, wherein said quadrature phase shifter is configured for a particular operating frequency range and has an input impedance for that operating frequency range that is optimally matched to the input impedance of the radio transceiver and the input impedance for the planar antenna.
20. A system as recited in Claim 12, wherein such planar antenna is configured for a particular operating frequency range and wherein such operating frequency range can be changed by adjusting the antenna dimensions while considering the dielectric properties of the printed circuit board.
21. A system as recited in Claim 12 wherein one or both of the printed circuit boards is constructed of a flexible material upon which conductive strips have been placed.
Description:
OMNIDIRECTIONAL PLANAR ANTENNA BACKGROUND OF THE INVENTION The invention relates to the field of omni-directional, planar folded dipole antenna systems operating in defined frequency bands. More particularly, the invention relates to an innovative, low cost omni-directional planar antenna and a quadrature phase shifter implemented on separate printed circuit boards ("PCBs"). The invention is particularly useful for short range radio frequency applications such as gaming, consumer electronics and data communications.

Conventional phase shifters require additional electronic circuitry such as power dividers, resistors, inductors and capacitors. These components increase manufacturing cost and reduce system reliability. Consequently, the elimination or reduction of such components would be highly beneficial.

Various planar dipole antennas and antenna systems have been developed. For example, United States Patent No. 3,813,674 to Sidford (1974) described a folded dipole antenna without radiator elements fed by a switched diode mechanism. United States Patent No. 4,083,046 to Kaloi (1978) described a planar monomicrostrip dipole antenna formed on a single side of a dielectric material that was excited in a non-quadrature manner. United States Patent No. 4,155,089 and 4,151,532 to Kaloi (1979) described twin electric microstrip dipole antennas consisting of thin electrically conducting patches formed on both sides of a dielectric substrate excited in a non-quadrature manner. United States Patent No. 4,438,437 to Burgmyer (1984) described two monopoles mounted on one side of a PCB and feed lines connected on the opposite side. United States Patent No.

4,916,457 to Foy et al. (1990) described a cross-slotted conductor fed with a quadrature

signal employing a multilayer PCB construction. United States Patent No. 4,973,972 to Huang (1990) described a circularly polarized microstrip array antenna utilizing a honeycomb substrate and a teardrop-shaped inter-layer coupling structure.

In other systems, Huang (1990) described a rudimentary phase shifting strip line feed integral to the antenna structure. United States Patent No. 5,481,272 to Yarsunas (1996) described a circularly polarized microcell antenna employing a pair of crossed, non-microstrip dipoles fed through a single feed-line. The phase shifters were integral to the antenna feed design and the entire structure was manually bolted together. United States Patent No. 5,508,710 to Wang et al. (1996) described a planar antenna having a circular folded dipole antenna. United States No. 5,539,414 to Keen (1996) and United States No. 5,821,902 to Keen (2000) described a single element folded dipole microstrip antenna fed by a coaxial cable. United States No. 5,592,182 to Yao et al. (1997) described a non-PCB dual-loop omni-directional antenna that was driven in phase quadrature.

United States No. 6,057,803 to Kane et al. (2000) described hybrid combinations of planar antenna elements.

United States Patent No. 5,268,701 to Smith et al. (1993) described a dual polarized antenna element composed of two perpendicular inter-locking elements where both the antenna and phase shifting sub-elements were incorporated into multiple layers of each sub-element so that the antenna and the phase shifting circuitry were both mounted on expensive sub-elements.

United States Patent No. 5,628,057 to Phillips et al. (1997) described a strip line transformation network capable of interfacing between an unbalanced port and a plurality of differently phased balanced ports using variable length strip lines and interconnecting vias between layers. United States Patent No. 5,832,376 to Henderson et al. (1998) shows

a hybrid RF mixer/phase shifter containing both stripline and electronic components such as diodes.

Despite the variety of systems providing an antenna for use with electronic components, a need exists for an improved antenna system providing superior manufacturing and operating efficiencies.

SUMMARY OF THE INVENTION The invention provides a planar, omni-directional antenna system for use with printed circuit boards. The system comprises a planar antenna implemented on a first printed circuit board for radiating and receiving electromagnetic signals, wherein the antenna has four quarter-wavelength, folded dipole sections organized in pairs, a radio transceiver, and a quadrature phase shifter implemented on a second printed circuit board and electrically connected with both the planar antenna and the radio transceiver, wherein the quadrature phase shifter comprises a plurality of transformer elements.

Preferably the quadrature phase shifter and the radio transceiver are integrated on a common printed circuit board. Such a configuration allows the radio transceiver electronics of a radio frequency electronics device to be completely separate from the other device electronics and more highly integrated. This approach allows for modular replacement of the radio transceiver electronics or other device electronics as new design enhancements are introduced. Electronics in addition to or instead of the radio transceiver may, however, also be integrated onto a common printed circuit board with the quadrature phase shifter, with or without the radio transceiver.

The quadrature phase shifter is implemented on one or more layers of a multilayer printed circuit board depending on the design constraints imposed by a particular system.

Layers not containing quadrature phase shifter circuitry may contain a radio transceiver or

other electronics and also provide ground plane shielding above and below the physical quadrature phase shifter location on the multilayer printed circuit board. Preferably the quadrature phase shifter is implemented on a single layer of a multilayer printed circuit board. Where the quadrature phase shifter is implemented on more than one layer of a multilayer printed circuit board, the layers may be capacitively coupled and the capacitive coupling may contribute to the phase shifting properties of the quadrature phase shifter.

The quadrature phase shifter may be comprised of a phase shifting hybrid power divider for providing capacitive coupling and phase shifting properties. Alternatively, the quadrature phase shifter may be comprised of an impedance converter.

Preferably, the planar antenna is further comprised of phasor passive radiator segments which are associated with the folded dipole sections of the planar antenna. More preferably, the planar antenna is comprised of at least one pair of phasor passive radiator segments. In the preferred embodiment of the invention, the planar antenna is comprised of four phasor passive radiator segments, with one such segment being associated with each of the folded dipole sections of the planar antenna.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates the physical configuration of a preferred embodiment of the invention.

Figure 2 illustrates a dimensioned planar antenna system according to the invention.

Figure 3 illustrates a side view of a planar antenna system of Figure 1 depicting the intersection of a planar antenna printed circuit board with a quadrature phase shifter printed circuit board.

Figure 4 illustrates exemplary input network characteristics of the planar folded dipole antenna including reflection, phase shift and complex impedance in and around a representative operating frequency range of 900 to 950 MHz.

Figure 5 illustrates a dimensioned superposition of the layers of a quadrature phase shifter printed circuit board according to a first preferred embodiment of the invention.

Figure 6 illustrates a decomposition of the layers of the quadrature phase shifter printed circuit board of Figure 5.

Figure 7 illustrates an exemplary transmitted omni-directional electromagnetic field of a planar antenna according to the invention.

Figure 8a illustrates a remote dipole antenna oriented parallel to the x-y plane of the planar antenna of the invention.

Figure 8b illustrates a remote dipole antenna oriented perpendicularly to the x-y plane of the planar antenna of the invention.

Figure 9 illustrates a rotational angle theta as a remote dipole antenna moves in a radial path around the planar antenna in the x-y plane.

Figure 10 illustrates a representative power plot of the received signal at the planar antenna from a remote dipole antenna.

Figure 11 illustrates a dimensioned superposition of a quadrature phase shifter layer and radio transceiver layer of a multilayer printed circuit board according to a second preferred embodiment of the invention.

Figure 12 illustrates a decomposition of the layers of the printed circuit board of Figure 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention provides an improved antenna for use with electronic components.

A planar antenna is implemented by preferably using a single layer, inexpensive first PCB having microstrips on at least one surface. A quadrature phase shifter is implemented using a more expensive multilayer second PCB. The multilayer PCB may be configured with strip lines implemented as PCB metallic traces incorporated on one or more PCB layers. Preferably the metallic traces are incorporated on one or more inner PCB layers which are surrounded on outer PCB layers by metallic ground planes. The quadrature phase shifter including phase shifting circuitry and transformer circuitry can be implemented on one or more PCB layers. Where the quadrature phase shifter is implemented on more than one PCB layer, the layers may be capacitively coupled.

Variable length strip lines are compactly configured and a PCB-strip-line-based, capacitively-coupled hybrid power divider and phase shifter can be incorporated in certain preferred embodiments of the invention. When radio frequency circuitry or other electronics circuitry are integrated onto the multilayer PCB, such circuitry can be present on one or more of any of the PCB layers including the ground plane layers and is strategically positioned so as not to affect the operation of the quadrature phase shifter.

The functional elements of the planar antenna and quadrature phase shifter are implemented using strategically configured and dimensioned microstrip and strip line segments. The planar antenna system comprises entirely passive components fashioned from printed circuit board metallic segments, thereby reducing manufacturing costs and improving repeatability and reliability with regards to mass production of the antenna system.

As shown in Figure 1, planar antenna system 10 is shown with antenna PCB 12.

System 10 comprises single layer planar antenna 14 implemented on antenna PCB 12

engaged perpendicularly through a slot in the planar antenna 14 and secured by solder or similar conductive bonding material to a quadrature phase shifter 16 contained on a second quadrature phase shifter PCB 17. The antenna PCB 12 and the quadrature phase shifter PCB 17 need not necessarily be engaged perpendicularly and may be engaged in any relative orientation which facilitates the electrical connection of the planar antenna 14 with the quadrature phase shifter 16 and which facilitates the effective operation of the planar antenna system 10. Second quadrature phase shifter PCB 17 is more expensive than antenna PCB 12 and may contain other system electronics such as a radio transceiver and/or all the remaining system electronics. The shape of quadrature phase shifter PCB 17 including the shape and configuration of one or more slots between antenna PCB 12 and quadrature phase shifter PCB 17 is representative only. Two preferred embodiments are illustrated in Figure 5 and Figure 11. Quadrature phase shifter PCB 17 may be connected to a third PCB 18 containing other electronics such as a radio transceiver or other system electronics. Alternatively, such electronics may be integrated into the quadrature phase shifter PCB 17.

As shown in Figure 2, planar antenna 14 consists of four folded dipole segments (22,24,26,28) where each segment is accompanied by a phasing element (19,21,23,25).

The folded dipole segments (22,24,26,28) are implemented on the front side of planar antenna 14, and the cross section of quadrature phase shifter 16 engaging with planar antenna 14 is also shown in Figure 3. The length of each folded dipole segment (22,24,26,28) is approximately one quarter wavelength of the center frequency of the desired operating frequency range. The dimensions of planar antenna 14 may vary slightly depending on the dielectric constant of the PCB material that introduces minor delays in the antenna surface currents. For a 900 to 950 MHz frequency range, the dimensions are as shown in Figure 2. For other operating frequency ranges the

dimensions will vary in proportion to the operating frequency for example such dimensions would be smaller for the 2.4 GHz ISM band.

A cross section of the PCB intersection is shown in Figure 3 wherein planar antenna microstrips 27 are preferably located on a single, front side of planar antenna 14 but may also be located on both sides of planar antenna 14 in other embodiments of the invention. Folded dipole segments (22,24,26,28) are preferably located on one side of a PCB as shown in Figure 3, however pairs of dipoles could be alternately located on opposite sides of the PCB. The input impedance across each pair of antenna leads is twenty-five ohms in one embodiment of the invention. Because planar antenna 14 is mounted separately from other system electronics, antenna PCB 12 can be made of less expensive material that does not support multilayer PCB traces, further adding to design economy. Referring to Figure 3, planar antenna PCB dielectric layer 31 is preferably made from phenolic material which is relatively inexpensive compared to other PCB dielectric materials. Associated with each folded dipole segment in the preferred embodiments is a phasor passive radiator element or phasing element (19,21,23,25).

Phasing elements (19,21,23,25) provide coupling between folded dipole segments (22,24,26,28), thereby combining fields from opposing dipole ends. This draws the electromagnetic fields together, contributing to the omni-directional radiation field pattern of antenna 14. Referring to Figure 7, the phasor passive radiator elements (19,21,23,25) may be omitted from the planar antenna 14 with some diminishment in the omni- directional performance of the planar antenna system 10.

Referring to Figure 4, planar antenna 14 has an input reflection response 30 and phase response 32 centered about or"tuned"to a desired frequency range. The magnitude 33 of the input reflection response indicates the degree to which a given frequency is reflected by antenna 14. For ideal power transfer no input signal is reflected. A

magnitude value of zero indicates perfect reflection, whereas a lower value indicates less reflection and hence higher power transfer. Power transfer in the 900 to 950 MHz range is preferred. Smith chart 34 indicates complex impedance for the analyzed operating frequency range. The width of the desired operating frequency range is determined by the "Q"value of the antenna as known in the art. The higher the Q value, the greater the signal reflection or attenuation for off-operating-frequency-range signals and the narrower the operating frequency range. The specific physical configuration and dimensions of the metallic traces and the dielectric properties of the PCB material embodied in the invention all contribute to determining the Q value of the system. The preferred planar antenna 14 configuration and dimensions for the 900 to 950 MHz frequency range are shown in Figure 2. Other frequency ranges of various sizes may be accommodated by changing the physical lengths of the metallic traces and potentially the dielectric of the PCB material chosen.

Figure 5 illustrates a first preferred embodiment of quadrature phase shifter 100 as a superposition of multiple circuit board layers that enables the phase shifting function and efficient impedance matching between input and outputs to quadrature phase shifter 100.

Quadrature phase shifter 100 has a"strip line"format in that the metallic traces for carrying signals are primarily sandwiched between metallic ground planes 136 and 138 as shown in Figure 6. The input between the quadrature phase shifter 100 and the radio transceiver 101 is shown as 116. Signals to and from the radio transceiver 101 pass through metallic strip line 110. Ninety degree hybrid power divider 114 in Figure 5 is composed of layer two and layer three strip line curved sections 120 and 122 (Figure 6, Layers B and C) sandwiched between metal ground planes 136 and 138 (Figure 6, Layers A and D). Strip line curved sections 120 and 122 are not physically connected but are

capacitively coupled. Hybrid power divider 114 splits the signal from radio transceiver 101 evenly and introduces phase shift while introducing negligible power loss.

As shown in Figure 6, on Layer C a zero degree phase shifted (relative to the input of 114), unbalanced output 124 from hybrid divider 114 enters transformer portion 112 section (Figure 5) of quadrature phase shifter circuit 100. This signal passes through transformer element 128 and then transformer element 130 to produce output 102 and output 108 respectively (Figure 5). Outputs 102 and 108 are balanced and 180 degrees out of phase with each other. Outputs 102 and 108 on Layer C are connected to connector pads 140 and 144 and pads 150 and 148 respectively on Layer A and Layer D by vias 141 and 143 that pass through all layers of the quadrature phase shifter 100 PCB as shown in Figure 6. These pads are used as solder points 29 (Figure 3) to connect quadrature phase shifter 100 to the planar antenna 14 folded dipole segments (22,24). On Layer B as shown in Figure 6, a 90 degree phase shifted (relative to the input of 114), unbalanced output 126 from the hybrid divider 114 enters the transformer 112 section (Figure 5) of the quadrature phase shifter 100. This signal passes through transformer element 132 and then transformer element 134 to produce output 104 and output 106 respectively (see Figure 5).

Outputs 104 and 106 are balanced and 180 degrees out of phase with each other. Outputs 102 to 108 are phase shifted from input 116. Outputs 104 and 106 on Layer B are connected to connector pads 146 and 142 respectively on Layer D and Layer A by vias 145 and 147 that pass through layers B, C, D and layers B and A of the quadrature phase shifter circuit 100 PCB as shown in Figure 6. These pads are used as solder points 29 (see Figure 3) to connect quadrature phase shifter 100 to the planar antenna 14 folded dipole segments (26,28). If output 102 is defined at being at an output phase reference of zero degrees, outputs 104,106 and 108 are at relative phase angles of ninety, two hundred seventy and one hundred eighty degrees with respect to output 102. The zig-zag shape of

folded strip line sections of transformer sections 128,130,132 and 134 contribute to the quadrature phase shifter circuit's 100 compactness. Quadrature phase shifter 100 thus produces the signal that drives planar antenna 14 in a quadrature phase shifted fashion resulting in a circularly polarized output signal from planar antenna 14. Similarly horizontal and vertical polarized signals received by planar antenna 14 pass in the reverse direction and are combined into a composite signal which emerges from the output 116 before being fed to radio transceiver 101.

Due to the design configuration, the input and output impedance to quadrature phase shifter 100 are both fifty ohms. This impedance matching ensures efficient power transfer between planar antenna 14 and the radio transceiver 101. The impedance value is a function of the physical dimensions and configuration of the system and is designed to be substantially at this value for the entire operating frequency range of antenna system 10.

Figure 11 illustrates a second preferred embodiment of quadrature phase shifter 180 with an integrated radio transceiver 186 on the quadrature phase shifter PCB 17. It has a"strip line"format in that the metallic traces for carrying signals are primarily sandwiched between metallic ground planes 200 and 202 as shown in Figure 12 (Layer B and layer D). Figure 11 is a superposition of the phase shifter circuit 182 and radio transceiver 186 circuitry which are on different layers of the quadrature phase shifter PCB 17. The quadrature phase shifter 180 is composed of several main components including the phase shifter circuit 182, transformer elements (212,214,216), an impedance converter 184, and the radio transceiver 186. Signals pass between the third PCB 18 (unless all electronics have been integrated into quadrature phase shifter PCB 17, in which case third PCB 18 may be omitted) and radio transceiver 186 through interface 188 through connector leads 256 and 258 (Figure 12) on both sides of quadrature phase shifter PCB 17.

Radio transceiver 186 converts the third PCB 18 digital signals to and from radio frequency signals that emerge at connection point 194. Radio transceiver 186 electronic components are primarily located on Layer A in Figure 12, however vias and interconnection metallic traces are found on other layers B, C and D (250,252,254). The output 190 of the phase shifter circuit 182 connects the quadrature phase shifter 180 to the planar antenna 14 and stubs 192 provide mechanical strength between planar antenna PCB 12 and quadrature phase shifter PCB 17.

The impedance between the quadrature phase shifter 180 main components is matched. Impedance converter 184 matches the impedance between phase shifter circuit 182 and the radio transceiver 186. At point 198 the impedance looking back to radio transceiver 186 and looking into impedance converter 184 is 50 ohms. At point 199 the impedance looking in either direction is 6.25 ohms. The phase shifter circuit 182 electrical properties alter the impedance between point 199 and the output 190 of phase shifter circuit 182. At the output 190 of phase shifter circuit 182 the impedance is a balanced 25 ohms across planar antenna 14 inputs. This is optimally matched to the planar antenna 14 input impedance of 25 ohms. The impedance converter 184 compensates for impedance changes introduced by the phase shifter circuit 182 and matches the output impedance of the phase shifter circuit 182 with the input impedance of the radio transceiver 186. This impedance matching ensures optimal power transfer between the radio transceiver 186 and the phase shifter circuit 182 and between phase shifter circuit 182 and planar antenna 14. The impedance value is a function of the physical dimensions and configuration of the system and is designed to be substantially at this value for the entire operating frequency range of antenna system 10.

System operation during radio frequency signal transmission is described below.

The signal direction is reversed during the reception of radio frequency signals from

planar antenna 14. With reference to Figure 11, during transmission a radio frequency signal passes from radio transceiver 186 from Layer A, through Layer B to connection point 194 on Layer C by way of vias 193. On Layer C, the signal then passes through metallic trace 196, impedance converter 184, metallic trace 210 (Figure 12), and then to output 218. The signal branches and continues on through transformer element 212 that introduces 180 degrees of phase shift and emerges at output 220. Outputs 218 and 220 are balanced and 180 degrees out of phase with respect to each other. Outputs 218 and 220 on Layer C are connected to connector pads 242 and 244 on Layer A by vias 234 and 236 that pass through all layers of quadrature phase shifter circuit 180 as shown in Figure 12.

Connector pads could also be implemented on Layer D at the point where vias 234 and 236 emerge on that layer. These pads are used as solder points 29 (Figure 3) to connect quadrature phase shifter 180 to the planar antenna 14 folded dipole segments (22,24). On another path on Layer C the radio frequency signal continues on from just before output 220 through transformer element 214 and then transformer element 216 to produce output 222 and output 224 respectively (see Figure 12). Outputs 222 and 224 are balanced and 180 degrees out of phase with each other. Outputs 220 to 224 are phase shifted from connection point 194. Outputs 222 and 224 are connected to connector pads 246 and 248 by metallic traces 238 (Layer D) and 240 (Layer A) respectively and by vias 232 and 230 respectively that pass through all layers of quadrature phase shifter circuit 180 as shown in Figure 12. These pads are used as solder points 29 (see Figure 3) to connect quadrature phase shifter 180 to the planar antenna 14 folded dipole segments (26,28). If output 218 is defined at being at an output phase reference of zero degrees, outputs 224,222 and 220 are at relative phase angles of ninety (360 degrees plus 90 degree or 450 degrees shifted with respect to output 218), two hundred seventy and one hundred eighty degrees with respect to output 218. The zig-zag shape of folded strip line sections of transformer sections 212,

214 and 216 contribute to the quadrature phase shifter circuit 180 compactness. The quadrature phase shifter circuit 180 thus produces the signal that drive planar antenna 14 in a quadrature phase shifted fashion resulting in a circularly polarized output signal from planar antenna 14. Similarly horizontal and vertical polarized signals received by planar antenna 14 pass in the reverse direction and are combined into a composite signal which emerges from the connection point 194 before being fed to radio transceiver 186.

Figures 7 through 10 illustrate various attributes of the electromagnetic field for antenna system 10. Due to the quadrature nature of the system, planar antenna 14 has a transmit far electromagnetic field which is substantially omni-directional in nature as shown in Figure 7. The receive capability of the planar antenna 14 is horizontally omni- directional in directions substantially perpendicular to its flat surface. Figures 8a and 8b show the planar antenna and a basic remote dipole antenna (160,162) typically located in a portable radio frequency device. While remote dipole antenna (160,162) is substantially in the x-y plane as shown in Figures 8a and 8b, planar antenna 14 receives the transmit signals from the remote dipole antenna (160,162) to planar antenna 14 equally well regardless of its rotational orientation. Two examples of such orientation are shown in Figure 8a and Figure 8b in 160 and 162 respectively. This is true since the sum of the induced voltages in planar antenna 14 as collected from its four dipole segments (22,24,26,28) and combined by quadrature phase shifter circuit 100 is essentially the same regardless of the rotational orientation of remote dipole antenna (160,162). Figure 9 illustrates a top view of the same system with an angle theta 164 defined. When remote dipole antenna 160 is perpendicular to the flat surface of planar antenna 166, theta 164 is zero degrees (in front) or plus or minus one hundred eighty degrees (in back).

Figure 10 illustrates a representative receive power plot of planar antenna 14 as angle theta 164 is varied. Horizontal axis 168 shows theta 164 and vertical axis 170 shows

the magnitude of the received power. When theta 164 is plus or minus ninety degrees from the positive y axis, the composite received power by antenna system 10 is at a minimum. This occurs since in this case remote dipole antenna 160 is located to the side of the thin edge of planar antenna 14. At almost all other angles in front or back of planar antenna 14 the power is essentially constant. Combining this attribute with the independence of signal strength regardless of the rotational orientation, the invention has substantial advantages. When a user is holding a device containing the remote dipole antenna 160, the user can be in numerous locations in front or back of planar antenna 14 in the x-y plane and regardless of the device rotational orientation, the received signal at planar antenna 14 from remote dipole antenna 160 is essentially the same.

Another embodiment of the invention may be constructed in which one or more of the printed circuit boards may be constructed using any material upon which conductive strips are deposited and wherein multiple layers of said material with conductive inter- layer connections are laid upon each other. For example such a device or portions of such a device might be constructed upon layers of plastic or similar flexible film upon which conductive strips may be deposited or printed.

The invention provides an omni-directional, planar folded dipole antenna and related quadrature phase shifter implemented on PCBs having differing properties. The planar antenna may be implemented on a single-sided inexpensive PCB whereas quadrature phase shifter and possibly other system electronics are implemented on more expensive multilayer PCBs. The invention reduces cost and improves system reliability because coaxial or other connectors of varying material and installation quality are not required between planar antenna and quadrature phase shifter. Planar antenna transmits radio frequency signals in an omni-directional pattern and is capable of receiving signals from remote dipole antennas positioned in arbitrary physical orientations. Quadrature

phase shifter provides both phase shifting functions and also converts an unbalanced radio transceiver output signal into a balanced input signal to planar antenna. The invention is preferably configured for use in low power, short range radio systems such as consumer electronics, gaming, computer and local area networking but can also be used for other applications where severe cost constraints require a highly integrated, effective and consistently reproducible antenna system design.

The invention provides a simple and effective two piece circularly polarized antenna system consisting of a planar antenna and a quadrature phase shifter which are implemented using printed circuit boards of differing properties and costs. The antenna system produces a substantially omni-directional field using a reliably and consistently manufacturable design. Despite the simplicity of the design, a remote dipole antenna, connected to a radio transceiver sending and receiving radio frequency signals to the antenna system, may be configured in an arbitrary physical orientation. This greatly increases the utility because the end user does not have to be concerned about how the device is oriented or where the device is located to get optimal and reliable signal transmissions. The invention substantially provides antenna system efficiencies for extremely cost constrained radio frequency applications.

Although the invention has been described in terms of certain preferred embodiments, it will become apparent to those of ordinary skill in the art that modifications and improvements can be made to the ordinary scope of the invention concepts herein without departing from the scope of the invention. The embodiments shown herein are merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the invention.