天線前沿技術(shù)

1、天線前沿技術(shù) Dual Frequency Double-Branch Printed Inverted-F Antenna (Have been published in IEEE AP-S 2002) Dual Frequency Double-Branch Printed Inverted-F Antenna Mingyan Fan, Zhenghe Feng, Xuexia Zhang Department of Electronic Engineering, Tsinghua University Beijing, 100084, China Introduction The ant

2、ennas with inverted-F structure are widely used for mobile handsets. Generally speaking, any radiating pole (such as conducting wire, strip, patch) with grounded point can be described as some kind of Invert F structure. This very compact and low-cost structure can be derived many type antennas for

3、wireless applications. In 12, the PIFA is printed on the circuit board. The planar structure has extremely low profile and is more conveniently to be integrated with circuit, compared with other type IFA. Recently, the double branches printed IFA structure has been presented to broaden bandwidth in

4、3, where the end of radiating arm is bifurcated. The bifurcation structure is equivalent to perturbation adding into the radiating structure. In this paper, the double branches structure is further developed and the dual frequency DB-PIFA (Double-Branch Printed Inverted-F Antenna) prototype is first

5、ly proposed. Design of DB-PIFA The geometry of the antenna is shown in Fig.1. The radiating element (within 38mm×15mm) is printed on the top layer of substrate base with relative permittivity and height . The hatched part is the conducting ground at the bottom layer. The wide strip on the left

6、side is grounded by vias. The double branches are constituted of meander-line and straight-line strips. The length of straight-line strip determines the higher resonant frequency, and the initial length of the straight-line strip can be given by (1)The Lax in Fig.1 determines the lower resonant freq

7、uency. Referring to 4, the SR (Shortening Ratio) is intended to 30%40%. Thus, the initial can be given by (2)However, the other parameters of the antenna are difficult to be given by empirical formula. The coupling effect of straight strip, the effect of finite ground at bottom layer, the equivalent

8、 self-inductance of the meander-line strip and etc should be taken into account. In actually designing, the Ls and Lax are firstly decided by (1) and (2) respectively, and then the other parameters of meander line strip are adjusted to lower resonant frequency by simulations, at last the Ls and the

9、shape of the meander-line are trimmed for the best impendence matching for dual bands. Measurement and simulation Fig.2 is a photograph of the fabricated DB-PIFA. IE3D of Zeland Company is used to simulate this structure. The measured and simulated return losses for the antenna 1# are compared in Fi

10、g3, and the agreement is satisfactory. The results in simulation and measurement are shown that there are two resonant frequency bands, of which the center frequencies are 1.2 GHz and 2.3GHz respectively. For the DB-PIFA, there are too many parameters of the DB-PIFA to be studied. In this paper, sev

11、eral key factors are discussed. The effect of ground is shown is Fig.4, where the return losses of the antenna 2# with smaller ground plane (40mm×35mm) is compared with that of antenna 1#. It is shown that with the decrease of the ground-plane dimension, the resonant frequencies for both bands

12、increase slightly. In Fig.5, the return losses of the antenna 3# with the same dimension as the antenna 1#, but higher substrate permittivity ( ) is shown. It is indicated that using higher permittivity can decrease the resonant frequency or reduce the dimension of the antenna. At last, the radiatio

13、n patterns with the frequencies at 1.2 GHz and 2.3GHz are simulated in the Fig6. and Fig7. Conclusion In this paper, the DB-PIFA is designed, fabricated and studied. The detail of trimming technology will be presented in presentation or other publication. The concept of double branches is developed

14、to realize the property of dual frequency in inverted-F radiating structures. What's more, the meander line is firstly used in the DB-PIFA structure to reduce the length of radiating arm for the low resonant frequency. The proposed antenna has inherits nearly all the advantages of traditional printed IFA. It is a good candidate