CST – Computer Simulation Technology

Multiple Band-Notched Planar Monopole UWB Antenna

A multiple band-notched planar monopole antenna for multiband wireless systems is presented. The proposed antenna consists of a wideband planar monopole antenna and the multiple U-shape slots, producing band-notched characteristics. In order to generate two band-notched characteristics, a three U-shaped slot configuration is proposed. This technique is suitable for creating an ultra-wideband (UWB) antenna with narrow frequency notches or for creating multiband antennas. A summary of the work presented in the paper "Multiple Band-Notched Planar Monopole Antenna for Multiband Wireless Systems" [1] is given, especially with respect to the simulations using CST MICROWAVE STUDIO® (CST MWS). The excellent agreement between the measurement and simulation results in presented in the reference paper....

With courtesy and permission of Professor Yu and his colleagues at the Korea Advanced Institute of Science and Technology (KAIST), Taejon, Korea.



Figure 1: Geometry of the band-notched planar monopole antenna

Fig. 1 shows the antenna which consists of a planar monopole antenna and multiple half wavelength U-shape slots. The planar monopole antenna was initially proposed in [2] and further studied in [3] and [4]. There are a number of parameters that influence the bandwidth; these include the size of planar monopole, the feeding gap, the beveling and the size of the ground plane. Prototype antennas were fabricated and mounted on a circular finite ground plane with radius 75 mm. A 50 SMA connector, centrally mounted from the back of the ground plane, was used to excite the antenna. A copper planar element of thickness 0.2 mm, size 20-27 mm and beveling angle 12, are vertically mounted at spacing 1 mm over the circular ground plane.



Figure 2: Monpole Antenna with notch filter components

Figure 2 shows a cross-sectional view of the antenna, clearly showing the upper frequency notches (side) and lower frequency notch (center). A coax of 75 Ohms is used to feed the antenna.

The behavior of the antenna can be easily investigated using CST MWS. Three configurations were simulated: with all notches present, with only the center notch and with only the side notches.



Figure 3: S-parameters for various notch configurations

The S-parameters for the three aforementioned cases are shown in Figure 3. As expected, the side notches contribute a high frequency mode with a low frequency mode resulting from the central notch. The combined effect is shown in the complete all-notches configuration.



Figure 4: 3D Farfield plots at 4 GHz and 4.78 GHz

The 3D Farfield plots at 4 GHz and 4.78 GHz are shown in Figure 4 with the polar forms in Figure 5. These results correspond to those presented in [1] where simulated results were compared to measurements for a wide-range of antenna configurations.



Figure 5: Farfield Polar plots at 4 GHz and 4.78 GHz

This article summarizes only a fraction of the work carried out in the [1] but does demonstrate the ability of CST MWS to simulate such structures. CST MWS lends itself naturally to the simulation of UWB antennas since it enables the user to investigate their real Time Domain behavior.

For a comparison between the measurement and simulated results, the reader is advised to consult [1] where the excellent agreement is shown.

References

[1] Wang-Sang Lee, Won-Gyu Lim, and Jong-Won Yu "Multiple Band-Notched Planar Monopole Antenna for Multiband Wireless Systems", IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 15, NO. 9, SEPTEMBER 2005

[2] M. J. Ammann, “Square planar monopole antenna,” in Proc. IEE Nat. Conf. Antennas Propagation, Apr. 1999, p. 461.

[3] M. J. Ammann and Z. N. Chen, “Wideband monopole antennas for multiband wireless systems,” IEEE Antennas Propagat. Mag., vol. 45, no. 5, pp. 146–150, Oct. 2003.

[4] S.-W. Su, K.-L. Wong, T.-T. Cheng, and W.-S. Chen, “Finite-groundplane effects on the ultra-wideband monopole antenna,” Microw. Opt. Technol. Lett., vol. 43, no. 6, pp. 535–537, Dec. 20, 2004.

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