No abstract

A dual‐band slot antenna comprising two narrow linear slots for wireless local area network (WLAN) operations in the 2.4 GHz (2.4–2.484 GHz) and 5.2 GHz (5.15–5.35 GHz) bands is presented. The two linear slots are arranged to be close and in parallel to each other, and are easily fed by using a single 50 Ω coaxial cable to achieve two desired operating modes at about 2.4 GHz and 5.2 GHz. A prototype of the proposed antenna with a narrow width of 10 mm suitable to be placed along the perimeter of the display of a notebook computer is constructed and studied. Experimental results of the constructed prototype are presented. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 306–308, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10591

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. ...

The simulated relationship between the bandwidth versus RL differs by a few percent from the theoretical result, but follows a somewhat similar decreasing trend. One reason for the deviation obtained is due to the simple RLC circuit model used (lossless environments are assumed). The simulated results include lossy dielectric material as well as metal loss. However, the obtained result indicates that the suggested antenna has a performance that is close to the highest possible one expected from the RLC circuitmodel principle.Almost symmetrical radiation in both front and back directions is obtained, that is, the ground plane is actually a part of the structure and does not act as a reflector.The shape of the loop-antenna element is optimised and the matching line is bent in order to minimise the occupied area. This also increases the conducting material inside the minimum sphere, which lowers the Q value and thus optimises the bandwidth. For practical use, both the shape of the loop and the length of the matching line should be carefully chosen in order to obtain the best frequency (bandwidth) performance for a given application.

A multiple-input-multiple-output (MIMO) antenna with a built-in decoupling mechanism is proposed for wireless local area network (WLAN) 2.4/5 GHz dual-band operations. The antennas were printed on an FR4 substrate and were located at the top portion of the FR4 board. The size of the antenna is 20 × 11 mm. The MIMO antenna system consists of two parallel folded branch monopoles with coupled feeds configured as two sets of two off-centred circular pads; the smaller ones were connected to the feeds and the larger ones were connected to the branch antennas. The coupled feed was used to achieve broad impedance matching bands. The two coupled feeds, separated by a small gap, were found to exhibit a built-in isolation mechanism, due to the opposite currents generated at the feeds and at the edges of the circular pads. That is, no additional physical structure was necessary to facilitate the needed isolation. The measured results show that both antennas have good impedance matching and port isolation. The antenna port envelope correlation coefficient was less than about 0.2 over the dual 2.4/5 GHz bands.