The present invention relates to an antenna structure. In particular, the invention provides an antenna structure suitable for use on a printed circuit board for Wireless Local Area Network (WLAN) use, where the antenna radiates over multiple frequency bands corresponding to several WLAN frequency bands.
Wireless Local Area Network (WLAN) stations and access points operate in at least one of the several WLAN frequency bands centered about 2.4 GHz, 4.9 GHz, 5.2 GHz, 5.5 GHz, and 5.8 GHz. Typically, each frequency requires a separate quarter wavelength antenna structure. In free space, a quarter wavelength for each of 2.4 GHz (Low Band, referred to herein as LB), 5.07 GHz (High Band Lower, referred to herein as HB-L), and 5.57 GHz (High Band Upper, referred to herein as HB-U) is approximately 31 mm, 14.7 mm and 13.4 mm, respectively. A printed circuit substrate such as FR4 has a permittivity ∈ of 4.2 on one surface and free air on the other, so the lengths of the quarter wavelength shortens by a scaling factor of approximately
or 62% of the free space wavelength. In the prior art, each antenna structure is implemented with a separate quarter wave radiating structure implemented on a conductive pattern printed on FR4 substrate. It is desired to provide a single radiating antenna structure for use with a plurality of RF frequencies for use in a LAN.
A first object of the invention is a printed circuit antenna fed by a wideband feedline delivering to the radiating antenna multiple separate operating frequencies which the radiating antenna radiates efficiently at each separate operating frequency and presents a minimum return loss at each particular operating frequency to the feedline, the radiating frequencies including at least a Low Band (LB) frequency, High Band Lower (HB-L) frequency, and a High Band Upper (HB-U) frequency.
A second object of the invention is a printed circuit antenna formed from a two-sided circuit board having a feedline part and a radiating antenna part, the feedline part formed from conductors on an upper plane separated from an optional lower ground plane by a dielectric, the ground plane present in the feedline part and not present in the antenna part, the feedline region optionally having one or more edge-coupled ground reference structures, the radiating structure including:
a High Band Upper (HB-U) radiating part for frequencies such as 5.57 Ghz, the HB-U radiating part comprising, in sequence, a first segment coupled to the feedline, a second segment, and a third segment;
a lowband (LB) radiating part for frequencies such as 2.46 Ghz, the LB radiating part comprising in sequence, a fourth segment coupled to a fifth segment LB radiator, a fifth segment common radiator, and a sixth segment terminated to a ground reference, the fourth segment coupled through a gap to the first segment and to a first stub extended from the first segment;
a highband lower (HB-L) radiating structure for frequencies such as 5.07 GHz, the radiating part comprising, in sequence, the fourth segment for coupling HB-L RF from the first segment and first stub, the fourth segment coupled to a fifth segment LB radiator, the HB-L radiating structure comprising the sixth segment, the fifth segment common radiator, a bridge, a seventh segment HB-L radiator, and an eighth segment;
an inductive stub placed between the junction of the fifth segment LB radiator and fourth segment, and the intersection of the bridge and the seventh segment HB-L radiator, the inductive stub comprising, in series, a tenth segment, a ninth segment, and a seventh segment.
A feedline region 142 comprises a feedline 102 in a first plane which is separated from a ground plane 202 by a dielectric 204. The feedline 102 is optionally edge coupled to a left ground structure 104 or a right ground structure 106, the left ground structure 104 and right ground structure 106 formed by a conductor in the first plane which is either connected directly to the ground plane 202 or is formed by a conductive region which is at the same electrical potential as the ground plane 202, such as by a close proximity of the ground structures 104, 106 and the ground plane 202. The feedline 102, left ground structure 104, and right ground structure 106 are electrical conductors all located on the first plane of a circuit board, below which is a reference ground plane 202 which serves as a reference plane for the feedline 102 and separated by a dielectric material 204 such as FR4. The feedline and associated structures thereby provide a particular feedline 102 impedance, such as 50 ohms. Beyond the extent of the feedline 102, left ground structure 104, and right ground structure 106 is a radiating antenna region 140 which contains radiating structures formed as electrically conductive segments without a ground plane 202 below.
In one embodiment of the invention, the feedline 102 transitions over the edge 144 of a ground plane 202 to the antenna region 140 which includes a first segment 108, second segment 112, and third segment 114, which form a highband-upper HB-U RF radiator for RF delivered by the feedline in this frequency range. The first segment 108 and a first stub 110 which extends from the first segment 108 are coupled through a gap region 123, and in sequence to, a lowband (LB) radiator formed by a fourth segment 122, fifth segment LB radiator 120a, fifth segment common radiator 120b, and sixth segment 118, which is terminated in a ground reference such as left ground structure 104. The LB radiator structure thereby radiates LB RF coupled from the feedline 102 and first stub 110.
A highband lower (HB-L) radiator is formed from the sixth segment 118, fifth segment common radiator 120b, a bridge 130, a seventh segment HB-L radiator 128a, and an eighth segment 132, where the HB-L radiator receives RF energy in the HB-L frequency range from the feedline 102, which couples across gap 123, through the fourth segment 122 and fifth segment LB radiator 120a, which are capacitively coupled for the HB-L frequency. An LB inductive structure (which is inductive for LB frequencies) is coupled from the intersection of the bridge 130 and the seventh segment HB-L radiator 128a to the intersection of the fifth segment LB radiator 120a and fourth segment 122, and the LB inductive structure comprises, in sequence, a seventh segment inductive 128b, a ninth segment 126, and a tenth segment 124.
When the feedline 102 is fed with a lowband (LB) frequency such as 2.46 GHz, the RF travels from the feedline 102 through first segment 108 and first stub 110, coupling through a separation gap 123 to the fourth segment 122, fifth segment LB radiator 120a, fifth segment common radiator 120b, and sixth segment 118, the terminus of which is ground referenced such as with left ground structure 104. At 2.4 GHz, an inductive stub is formed by the segments 124, 126, 128b, 128a, and 132. When the feedline 102 is fed with a highband lower (HB-L) frequency such as 5.07 GHz, the RF travels from the feedline 102 to the first segment 108 and stub 110, edge couples through gap 123 to fourth segment 122 and fifth segment LB radiator 120a to the HB-L radiating structure formed by the sequence of sixth segment 118, fifth segment common radiator 120b, bridge 130, seventh segment HB-L radiator 128a and eighth segment 132.
When the feedline 102 is fed with a highband upper (HB-U) frequency such as 5.57 GHz, the RF travels from the feedline 102 to the first segment 108, second segment 112, and third segment 114.
In the embodiment shown in
In one embodiment of the invention shown in
At the junction of fifth segment LB radiator 120a and fifth segment common radiator 120b is bridge 130, which couples HB-L RF to HB-L radiators formed by the sequence of eighth segment 132, seventh segment HB-L radiator 128a, bridge 130, fifth segment common radiator 120b, and sixth segment 118.
Bridge 130 is also connected to seventh segment inductive 128b, ninth segment 126, and tenth segment 124 connected to the junction of fifth segment LB radiator 120a and fourth segment 122. Seventh segment inductive 128b, ninth segment 126, and tenth segment 124 operate together to form an inductive stub for LB coupled to fourth segment 122, directing energy to the LB radiating structure formed by 122, 120a, 120b, and 118. Bridge 130 also forms the HB-L resonant structure which couples HB-L RF energy from first segment 108 across gap 123 to fourth segment 122, and to the HB-L resonant structure formed by fifth segment common radiator 120b, sixth segment 118, bridge 130, seventh segment HB-L radiator 128a, and eighth segment 132.
In one embodiment, the tri-band radiator is formed from segment structures which perform functions as described below:
102—feedline with broadband frequency characteristics, referenced to ground plane 202 and adjacent left and right ground structures 104 and 106, respectively. Feedline 102 carries LB, HB-U and HB-L RF.
104 and 106—left and right ground structures, respectively. These provide edge coupling to feedline 102 and also provide ground references to other structures, including the end of sixth segment 118 and ground reference segment 116.
108—first segment, part of HB-U radiating structure with second segment 112 and third segment 114. First segment 108 also couples LB and HB-L RF to fourth segment 122 through gap 123.
112—second segment, part of HB-U radiating structure.
114—third segment, part of HB-U radiating structure.
110—first stub coupling LB and HB-L to fourth segment 122.
122—fourth segment, part of LB radiating structure, which also couples HB-L RF from first segment 108 and first stub 110 across gap 123 to associated radiating structures 118, 120b, 130, 128a, and 132.
120
a—fifth segment LB radiator, part of LB radiating structure 122, 120a, 120b, and 118.
120
b—fifth segment common radiator, part of both LB and HB-L radiating structures.
118—sixth segment, part of HB-L radiating structure, grounded at terminus by left ground 104.
128
b, 126, 124—seventh segment inductive, ninth segment, and tenth segments, respectively, form an inductive stub for LB, allowing coupling of RF into the LB radiator formed by 122, 120, and 118.
The structures of
For highband upper (HB-U) RF such as 5.57 GHz, feedline 102 couples RF to the HB-U radiating elements comprising first segment 108, second segment 112, and third segment 114. Reference segment 116 provides edge coupling to the HB-U radiating elements and increases the effective bandwidth of the HB-U radiating elements. The HB-U elements 108, 112, and 114 act as a quarter wave radiator at 5.57 Ghz.
For a lowband (LB) radiation frequency such as 2.46 GHz, the physical dimensions of the conductor segments are selected to provide coupling of LB RF from first segment 108 and first stub 110 to the LB RF radiating structure comprising fourth segment 122, fifth segment LB radiator 120a, fifth segment common radiator 120b, and sixth segment 118. For the LB frequency, the seventh segment inductive 128b, ninth segment 126, and tenth segment 124 act as an inductive stub, shortening the length of LB radiation structure 122, 120a, 120b, 118 from its natural quarter wavelength at 2.46 Ghz.
For highband lower (HB-L) RF such as 5.07 GHz, the physical dimensions of the conductors are selected to provide a radiating structure comprising, in sequence, sixth segment 118, fifth segment common radiator 120b, bridge 130, seventh segment HB-L radiator 128a, and eighth segment 132, and these elements together form a half wavelength radiator at the HB-L frequency.
Without limitation of the scope of the invention, a series of dimensions is offered as an example, the design of which provides the return loss plot shown in
Left ground structure 104: 20 mm×5.62 mm;
Right ground structure 106: 20 mm×5.62 mm;
feedline 102: 20 mm×0.41 mm
gap between first (left) edge of feedline 102 and left ground structure 104: 0.17 mm;
gap between second (right) edge of feedline 102 and right ground structure 106: 0.17 mm
sixth segment 118: 5.35 mm×0.60 mm;
fifth segment 120 (120a+120b): 4.4 mm×0.65 mm;
fifth segment common radiator 120b 2.1 mm×0.65 mm;
bridge 130: 0.3 mm×0.3 mm;
fourth segment 122: 4.8 mm×0.6 mm;
seventh segment HB-L radiator 128a: 2.8 mm×0.5 mm;
seventh segment (128a+128b): 10.5 mm×0.5 mm;
eighth segment 132: 5.85 mm×0.35 mm;
ninth segment 126: 0.3 mm×0.5 mm;
tenth segment 124: 5.45 mm×0.5 mm;
first segment 108+first stub 110: 5 mm×0.41 mm;
second segment 112: 4.04 mm×0.7 mm;
first stub 110: 0.95 mm×0.41 mm;
third segment 114: 2.1 mm×0.5 mm;
ground reference structure 116: 2.5 mm×1.45 mm.
In the example embodiment of the invention shown in
A HB-U radiating structure is formed by first segment 502 coupled to second segment 504. The other structures third segment 510, fourth segment 512, fifth segment 514, sixth segment 516, and seventh segment 518 have inductive coupling at HB-U radiating frequencies, and have minimal effect for HB-U frequencies.
A LB radiating structure is formed by third segment 510, fourth segment 512, and fifth segment 514, which is terminated in left ground structure 104. For LB radiation, first segment 502 acts primarily to couple RF energy across gap 508 to the LB RF radiating structure, and an inductive structure for LB RF is formed by sixth segment 516 and seventh segment 518.
The HB-L radiating structure is formed by fourth segment 512, sixth segment 516, and seventh segment 518. HB-L RF is coupled to the HB-L RF structure through first segment 502 and gap 508 to third segment 510, and also through second segment 504 to seventh segment 518 to the HB-L radiating structure 512, 516 and 518.
first segment 502: 4.75 mm×1.25 mm;
second segment 504: 6.25 mm×2 mm;
third segment 510: 3.75 mm×0.75 mm;
fourth segment 512: 5 mm×0.75 mm;
fifth segment 514: 4.25 mm×0.75 mm;
sixth segment 516: 2 mm×0.75 mm;
seventh segment 518: 13 mm×0.75 mm
gap 508: 0.8 mm.
Other arrangements of the HB-U, LB, and HB-L radiators are possible, but the example embodiment of
The proceeding has been a description of the preferred embodiments of the invention. It will be appreciated that deviations and modifications can be made without departing from the scope of the invention. In particular, the following modifications may be made individually, or in combination:
a) placement of any of the radiating structures or individual segments of the radiating structures on layers other than the top layer;
b) removal of bridge 130 of
c) removal of reference ground segment 116 of
d) reduction of the length of eighth segment 132 of
e) reduction or removal of third segment 114 of
f) mirroring of one or more segments of
g) rotation of any one or more segments of a radiating structure.
Any of the above modifications may be made through compensation of the lengths or dimensions of other structures to maintain the frequency characteristics desired. Dimensions which are provided for each of the segments of the corresponding embodiments are for exemplar use with the particular frequency given, and it is understood that any dimensioned segment of the previously described radiation structures may be modified +/−20 percent and still be usable for the specified WLAN frequencies. The term “substantially” with regard to dimensions is understood to mean+/−20 percent variation, and the term “substantially” with regard to parallel or perpendicular is understood to mean within 10 degrees of true parallel or perpendicular, respectively. the term “substantially” with respect to a particular frequency is understood to mean within +/−20 percent of the particular frequency. The scope of the invention is defined by the claims which follow.
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Entry |
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Sun, Liu, Cheung, Yuk, “Dual-Band Antenna With Compact Radiator for 2.4/5.2/5.8 GHz WLAN Applications”. |