Band‐notched ultra‐wideband circular‐disk monopole antenna with an arc‐shaped slot

Abstract

method proposed can be very successful. As an illustrative example, we consider a quasi-optical resonator with twin-shaped metal mesh [Fig. 2(b)] denoted as R 1 , placed inside the Talbot reflector (see Fig. 6). The mesh is illuminated by a Gaussian beam splitter inside the Talbot splitter. Element R 2 is a short with a hole in the center to allow transport of an electron beam, since the resonator is part of a free-electron maser. The total resonator length determining its resonance frequencies is L ϭ 1.31 m. The resonator is excited by a rectangular horn antenna. A scalar network analyzer HP-8757D measures the input reflection coefficient (return loss). Figure 7 shows the measured results (dotted line) and reconstructed data (solid line), based on the method suggested, for the grid dimensions considered in the previous section. The power reflectance of this grid is R P ϭ 0.9414 at the frequency 99.938 GHz, which is very close to the data reported in Table 1 for a rectangular grid with the same cell dimensions.The stability of the solution of the system of the two nonlinear equations of Eq. (7) has also been investigated in the case discussed. The following range of guessed values, which provide the same solutions of Eq. CONCLUSIONA model linking the reflectivity of metal meshes and grids and used as a coupling element of a quasi-optical resonator has been presented. Based on this model, the reflectance measurements of rectangular and twin-shaped meshes have been done by applying reconstruction algorithms. The measurements were based on an asymmetrical resonance curve and their validity was demonstrated. ACKNOWLEDGMENTThis work was done at the Israeli FEL Knowledge Center with partial support from the Israeli Ministry of Science. The authors would like to thank A. Faingersh for useful discussions and advice, as well as students Abby Anaton and Ofer Markish for modeling and plotting of the Talbot effect (Fig. 5) Circular-disk monopole antennas have a simple geometry and yet provide a very wide impedance bandwidth [1, 2]. Simply by adjusting the feed gap between the monopole antenna and the ground plane, the obtained impedance bandwidth can easily cover the recently proposed UWB communication systems over the frequency band of 3.1-10.6 GHz [3]. In this paper, we demonstrate that by embedding a simple arc-shaped slot close to and along the boundary of the circular-disk monopole, a notched frequency band in the UWB operating bandwidth can be obtained and easily controlled. This kind of band-notched UWB antenna requires no external filters and thus greatly simplifies the circuit design of the communication system. In this study, the proposed slotted circular-disk monopole antenna having an impedance bandwidth covering the frequency band of 3.1-10.6 GHz with a notched frequency band for rejecting the existing wireless local area network (WLAN) band, such as the 5.8-GHz band (5725-5875 MHz) [4], is implemented first. This band-notching property can avoid the possible interference of the UWB and existing WLAN systems. ...

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