Printed filtering antenna
A printed filtering antenna is provided. This filtering antenna comprises an antenna part and a coupled line resonator. The antenna part is directly connected to a coupled line resonator and occupies an antenna area. The coupled line resonator provides a filtering mechanism together with the antenna part. The coupled line resonator comprises a short-circuited stub and an open-circuited stub. The short-circuited stub comprises an open-circuited end and a short-circuited end connected to ground. The open-circuited stub is parallel to the short-circuited stub. The open-circuited stub comprises a first end and a second end. The first end is connected to the feed point and is corresponding to the open-circuited end of the short-circuited stub such that the open-circuited stub is coupled to the short-circuited stub.
1. A printed filtering antenna, comprising:
an antenna part; and
a coupled line resonator connected to the antenna part to provide a filtering mechanism together with the antenna part, wherein the coupled line resonator comprises:
a short-circuited stub comprising an open-circuited end and a short-circuited end connected to ground; and
an open-circuited stub parallel to the short-circuited stub wherein a gap is formed between the open-circuited stub and the short-circuited stub, and the open-circuited stub comprises a first end and a second end in which the first end is connected to the antenna part and is corresponding to the open-circuited end of the short-circuited stub such that the open-circuited stub is coupled to the short-circuited stub.
2. The printed filtering antenna of claim 1 , wherein an equivalent circuit of the short-circuited stub and the open-circuited stub comprises two groups of series-connected inductor-capacitor (LC) resonators that are connected in parallel.
3. The printed filtering antenna of claim 2 , wherein the two groups of series-connected LC resonators generate two transmission zeros at a band edge of the printed filtering antenna.
4. The printed filtering antenna of claim 3 , wherein the two groups of series-connected LC resonators are equivalent to a single parallel-connected LC resonator at a resonant frequency of the printed filtering antenna to generate a transmission pole.
5. The printed filtering antenna of claim 4 , wherein when a first electric length of the open-circuited stub and a second electric length of the short-circuited stub are equal to π/2 at the resonant frequency or each of the open-circuited stub and the short-circuited stub is a quarter-wavelength circuit, and the two transmission zeros are symmetric with respect to the transmission pole.
6. The printed filtering antenna of claim 4 , wherein when a first electric length of the open-circuited stub and a second electric length of the short-circuited stub are not equal, the two transmission zeros are asymmetric with respect to the transmission pole.
7. The printed filtering antenna of claim 1 , wherein the short-circuited stub and the open-circuited stub are two micro-strips disposed on the same plane.
8. The printed filtering antenna of claim 1 , wherein the short-circuited stub is a coplanar waveguide (CPW) and the open-circuited stub is a micro-strip, and a substrate is formed in the gap between the short-circuited stub and the open-circuited stub such that the short-circuited stub and the open-circuited stub are on opposite sides of the substrate.
9. The printed filtering antenna of claim 8 , wherein the short-circuited stub is an extension of a ground surface.
10. The printed filtering antenna of claim 1 , wherein the short-circuited stub and the open-circuited stub are a slot line or a coplanar stripline (CPS) respectively.
11. The printed filtering antenna of claim 1 , wherein the antenna part occupies an antenna area and the coupled line resonator is formed in the antenna area.
12. The printed filtering antenna of claim 1 , wherein the antenna part is a monopole antenna, an F antenna or an inverted-F antenna.
13. The printed filtering antenna of claim 1 , wherein the coupled line resonator has an N-1 order such that the antenna part is an Nth-order antenna, in which each order of the coupled line resonator is coupled to each other and one order of the coupled line resonator is connected to the antenna part directly.