Patent Grant
7605769
This application claims the benefit of Korean Patent Application No. 2006-35340 filed on Apr. 19, 2006 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a multi-band U-slot antenna, more particularly, which has a plurality of frequency notch filters to operate in a multi-band frequency as a single antenna.
2. Description of the Related Art
With a variety of systems incorporated together lately, an antenna has been required to possess higher capabilities. The antenna needs to function not only in a single narrow frequency band but also in a multiple narrow frequency band or a broad frequency band. Thus, the antenna should be designed to achieve multi-band performance. The multi-band can be attained by two methods of combining narrow bands together or embedding a frequency notch filter in a broad band. The former entails a complicated design and a time-consuming tuning caused by undesired results from design or during manufacturing. Therefore, recently, the latter has gained a spotlight. That is, a slot functioning as a notch filter has been inserted into a broadband antenna. This method involves simple designing and does not require a separate tuning after manufacturing, thereby simplifying a process.
As shown, a single U-slot microstrip patch antenna has a U-slot 13 formed in a patch 12. Although not illustrated, a dielectric body 12 and a ground substrate are stacked sequentially under the patch 12. Also, a coaxial line extends through the ground substrate and the dielectric body 11 onto the patch 12.
The U-slot located adjacent to radiating edges of the patch 12 disturbs distribution of current which generates fundamental resonance mode, thereby generating another resonance in its near-by frequency. This resonance characteristic, in combination with resonance of a square microstrip patch, beneficially assures dual resonance characteristics. That is, primary resonance is generated by the microstrip patch 12 and secondary resonance is generated by the U-slot 13. In
The two resonance frequencies, when spaced apart from each other, realize a dual resonance antenna, i.e., with a single notch filter. Meanwhile, the resonance frequencies, when located substantially identically, provide a broadband antenna. In general, the dual resonance antenna exhibits a big loop and a small loop on an impedance trajectory of a smith chart. Notably, position and size of the small loop within the big loop determines a bandwidth of impedance of the antenna. Parameters for varying the small loop on the smith chart include width and length of a square patch (bottom of the U-slot), length and shape of the U-slot, thickness and relative permittivity of the substrate.
Conventionally, attention was drawn only to a single notch filter, which was thus embedded in an antenna to achieve multi-band performance. However, little consideration was given to a method for embedding the notch filter to implement dual or more bands. The conventional single notch filter, when adopted for such multi band performance, is accompanied by great problems.
The present invention has been made to solve the foregoing problems of the prior art and therefore an aspect of the present invention is to provide a planar monopole antenna which has a plurality of U-slots with a symmetrical configuration disposed in a radiation device to act as a plurality of notch filters, thereby operating in a multi-band frequency.
According to an aspect of the invention, the multi-band U-slot planar antenna includes a limited ground plane; a connector having a ground terminal connected to the ground plane and a feeding terminal for feeding a signal; and a planar radiation device including a feeding point connected to the feeding terminal, a central U-slot having a symmetrical configuration about a central axis thereof, the central axis extending vertically from the feeding point, and at least one pair of auxiliary U-slots symmetrical with each other about the central axis.
The auxiliary U-slots comprise a pair of U-slots to act as a double notch filter. Alternatively, the auxiliary U-slots comprise two pairs of U-slots to act as a triple notch filter
According to an aspect of the invention, the multi-band U-slot planar antenna includes a limited ground plane; a connector having a ground terminal connected to the ground plane and a feeding terminal for feeding a signal; and a planar radiation device including a feeding point connected to the feeding terminal, a central U-slot having a symmetrical configuration about a central axis thereof, the central axis extending vertically from the feeding point, and at least one auxiliary U-slot having a symmetrical configuration about the central axis.
The auxiliary U-slot comprises one U-slot to act as a double notch filter.
The auxiliary U-slot has a central point located identical to that of the central U-slot.
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Here, a plurality of U-slots may be configured and arranged variously.
Referring to
A through hole 26 is perforated in a central portion of the limited ground plane 25 to connect a feeding point 24 of the radiation device 22 to the feeding terminal of the connector 27.
Preferably, the feeding point 24 is centered in a side portion of the planar radiation device 22.
A plurality of U-slots 23 are formed in the radiation device 22. Here, current flows in opposite directions inside and outside of the U-slots 23. If a total length of the U-slots corresponds to a half wavelength of a notch central frequency, the frequency has a return loss of almost 0 dB. Thus, the notch central frequency is determined by adjusting the length of the U-slots.
The U-slots 23 formed in a planar surface of the radiation device 22 are preferably arranged to be vertically symmetrical with each other about a central axis, which is an extended line 24a of the feeding point 24. This ensures the U-slots 23 to act as a notch filter with superior characteristics. Surely, the U-slots, with either a symmetrical or asymmetrical configuration, can function as a notch filter. However, the symmetrical configuration allows the notch filter to achieve better blocking characteristics. Moreover, a notch frequency band is decided by the width of the U-slots.
In
In
The central U-slot 23a has a symmetrical configuration about the extended line 24a of the feeding point. The auxiliary U-slots 23b are symmetrical with each other about the extended line 24a of the feeding point.
Such a configuration leads to change in a length of a current path where current flows, thereby altering a wavelength that generates resonance. In
The connector 27 is configured as a coaxial cable with an internal terminal acting as a feeding terminal to feed a signal to the radiation device, and connected to the feeding point 24 of the radiation device. An external terminal is connected to the ground plane 25.
a to 3c illustrate an embodiment of the invention in which a central slot is formed in a central area of a radiation device and a pair of auxiliary U-slots are disposed at both sides about the central U-slot, as shown in
Referring to
The central U-slot 33a has a central point located on an extended line 34a of the feeding point of the radiation device, and has a symmetrical configuration about the extended line 34a.
The central U-slot 33a is formed in an inverse direction so as to have an opening located adjacent to the feeding point.
The auxiliary U-slots 33b are formed in a forward direction at both sides about the central U-slot 33a. Preferably, the auxiliary U-slots 33b are symmetrical with each other about a central axis, i.e., the extended line 34a of the feeding point.
As described above, the U-slots have two pairs of symmetrical slot configurations about the extended line 34a of the feeding point of the radiation device, thereby enabling an antenna with two notch filters, i.e., a triple band antenna.
Referring to
In
a to 7d are graphs illustrating return losses of the antennas having the U-slots shown in
Referring to the graphs, frequency and return loss vary depending on arrangement of the U-slots, but the type of a notch filter is determined by the number of the slots which are symmetrical about the extended line of the feeding point.
Therefore, at a return loss of 10 dB, notch characteristics are plotted at frequencies of 3 GHz and 5 GHz, thereby producing three frequency bandwidths.
Referring to
Here, the ground plate is a metal layer for grounding.
The dielectric substrate 41 is interposed between the ground plate 45 and the radiation device 42 to provide uniform medium between the ground plate 45 and the radiation device 42 so that a signal is stored, and transmitted to an electromagnetic wave field.
Referring to
The central U-slot 43a and the auxiliary U-slot 43b have a vertically symmetrical configuration about the central line, i.e., the extended line 44a of the feeding point. Also, as described above, the central U-slot 43a has a central point identical to that of the auxiliary U-slot 43b.
In this arrangement, the U-slots have two pairs of symmetrical configurations about the central axis to act as a double notch filter, thereby operating in a triple frequency.
a to 5c illustrate an embodiment of the invention in which a central U-slot is formed in a central area of a radiation device, as shown in
Referring to
The central U-slot 53a has a central point located on an extended line 54 of the feeding point of the radiation device, and is vertically symmetrical about the extended line 54a.
The auxiliary U-slot 53b also has a central point located on the extended line 54a of the feeding point of the radiation device, and is vertically symmetrical about the extended line 54a.
As described above, the U-slots have two pairs of symmetrical slot configurations about the central axis, i.e., the extended line 54a of the feeding point of the radiation device, thereby producing an antenna with double notch filters, i.e., an antenna with triple bandwidths.
Referring to
Referring to
e and 7f are graphs illustrating return losses of the antennas shown in
Referring to the graphs, frequency and return loss vary depending on arrangement of the U-slots, but the type of a notch filter is determined by the number of the U-slots which are symmetrical about the central axis, i.e., the extended line of the radiation device.
Therefore, at a return loss of 10 dB, notch characteristics are plotted at frequencies of 3 GHz and 5 GHz, thereby producing three frequency bandwidths.
a to 6h are front elevation views illustrating various arrangements of U-slots to act as a triple notch filter according to further another embodiment of the invention.
Referring to
The central U-slot 63a has a central point located on an extended line 64a of a feeding point of a radiation device, and is vertically symmetrical about the extended line 64a.
A pair of first auxiliary U-slots 63b are formed in a forward direction to oppose each other about the central U-slot 63a, respectively, preferably to be symmetrical about the extended line 64a of the feeding point of the radiation device.
A pair of second auxiliary U-slots 63c are formed in a forward direction next to each of the first auxiliary U-slots 63b, preferably to be symmetrical about the extended line 64a of the feeding point of the radiation device.
As described above, the U-slots have three pairs of symmetrical slot configurations about the extended line 64a of the feeding point of the radiation device, thereby ensuring an antenna with three notch filters, i.e., a quadruple band antenna.
Referring to
Referring to
Here, the central U-slot 63a and the second auxiliary U-slot 63c have a vertical symmetrical configuration about the extended line 64a of the feeding point. The first auxiliary U-slots 63b are symmetrical with each other about the central axis, i.e., the extended line 64a, achieving an antenna with triple notch filters.
Referring to
Referring to
Here, the U-slots each have a symmetrical configuration about the central axis, i.e., the extended line 64a of the feeding point, thus achieving an antenna with triple notch filters.
Referring to
Referring to
Referring to
That is, at a return loss of 10 dB, four notch frequency bands are plotted at 2.0 GHz to 2.8 GHz, 3.1 GHz to 3.3 GHz, 4.0 GHz to 4.5 GHz, and 4.9 GHz to 5.7 GHz.
Here, the type, number and arrangement of U-slots can be variously modified in accordance with a necessary frequency band.
As set forth above, according to exemplary embodiments of the invention, a multi-band U-slot antenna can act as multiple notch filters depending on configuration and arrangement of U-slots formed in a planar radiation device. This allows transmission and reception of a multi-band frequency through a single antenna.
While the present invention has been shown and described in connection with the preferred embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0035340 | Apr 2006 | KR | national |
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| Number | Date | Country |
|---|---|---|
| WO 2006042562 | Apr 2006 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20070247386 A1 | Oct 2007 | US |
