Abstract-Tunable frequency selective surfaces (FSSs) based on split ring resonators (SRRs) are presented. Tuning performance is achieved by means of several on/off switches placed between the rings of each SRR element. The band-stop FSS response is dynamically tuned to different frequency bands at different switching states. In addition, loadings placed at the corners of outer ring elements, forming a fan-like shape, with additional switches are shown to offer rather fine-tuning capability. A dual-layer FSS is also introduced to demonstrate a filter response over a larger frequency band, and also offers tunable dualband operation via switching. By using complementary SRR elements, a tunable band-pass response instead can be obtained using a similar switching configuration. Practical switch modeling is also examined in the paper along with the scanning performance of the SRR-FSS. The numerical analysis of the FSS designs is accomplished using a fast periodic array simulator, and the measurements demonstrate preliminary validation of the proposed switching configuration.
Abstract:In this paper, an implantable microstrip antenna design is introduced to cover the Medical Implant Communications Service (MICS, 402 − 405 MHz) band for biomedical telemetry systems. The radiating layer of the antenna comprises two concentric square split-ring elements and a metallic pad placed between them. A shorting pin is also used for miniaturization purposes, directly connecting the outer ring element to the ground plane. It is numerically demonstrated that the proposed antenna offers approximately 7% impedance bandwidth and gains of 1.9 dBi at the designated frequency band. In addition, effects of some critical design parameters on the antenna performance are numerically examined in the paper, noting that the full-wave analysis of the implant antenna is carried out using CST Microwave Studio.
In this study, an implantable microstrip sandwiched (IMS) antenna for dual-band biotelemetry communication is proposed. The proposed antenna is comprised of a spiral shaped radiating element and a bended microstrip line sections. The radiating element is sandwiched between two thin substrates backed by a rectangular ground plane (GP). In addition, a shorting pin (SP) which connects radiating element to GP is used for miniaturization purpose. By optimizing the proposed antenna in terms of its size, feeding and SP position, the IMS antenna with only 10.6×10×1.27 mm 3 offers a dual band performance (VSWR<2) covering medical implant communication services (MICS) 402-405 MHz) and industrial, scientific and medical (ISM) 2.4-2.48 GHz) bands. It is numerically demonstrated that the proposed implant antenna offers 50% and 29% impedance bandwidth at the designated ISM and MICS frequency bands respectively. In the paper, numerical results for the proposed design are presented.
IntroductionCompact multi-function antennas play a major role in today's communication systems where size, weight, power consumption and cost are the main limiting factors in designing integrated transmitter/receiver circuitry. In this view, electronically reconfigurable printed antennas were previously considered to achieve multi-band applications [1−4]. In particular, printed dipole elements have been preferred in conformal arrays due to their low-profile and easy fabrication. Specifically, loaded dipole elements have recently been introduced for dualfrequency applications [4−6]. In this paper, a new loop-loaded printed dipole (LLPD) antenna design is proposed for a tunable (3 GHz or 5.2 GHz) array application. The tunable-LLPD (TLLPD) design consists of a printed dipole element and a pair of loop elements with extensions employed for tuning purposes via on/off switches in a practical realization.We note that the full-wave analysis of the proposed designs have been carried out using CST Microwave Studio, which utilizes the time-domain finite-integration method. In the paper, we present the corresponding simulation and preliminary measurement results to demonstrate the performance of the proposed LLPD designs. Antenna DesignThe LLPD design has recently been introduced in [4] aiming for a dual-band array operation. Here we present a new LLPD element with stub extensions attached to the loops to achieve a tunable antenna operation. The proposed TLLPD configuration is depicted in Fig. 1. As seen, the dipole element is placed between a pair of concentric rectangular loops with the extensions, where all are supported by a thin substrate (Rogers RT/duroid 5880) with a thickness of h 2 =0.75 mm and ε r =2.2. The substrate is placed over a vacuum-filled cavity with a height of h 1 =1.2 cm, and the dipole element is excited by a coaxial-feed placed within the cavity. In designing, the cavity height, the size of the loops, and the positions of the extensions as well as their lengths have been observed to be critical parameters to achieve desired performance in the designated frequency bands (3 GHz / 5.2 GHz). Also, each loop extension is connected to the corresponding loop via a metallic pad that represents a practical on/off switch. Note that the presence of a pad (1×1 mm 2 ) in a switch location refers to the switch being in 978-1-4244-4968-2/10/$25.00 ©2010 IEEE on-state (that is, the extension is attached to the loop), otherwise, in off-state (i.e., the extension is detached from the loop).The return loss characteristics of the TLLPD design along with that of the LLPD are displayed in Fig. 2. As seen, the LLPD provides a dual-band operation around 3 GHz and 5.5 GHz bands with respective 15% and 24% S 11 bandwidths. On the other hand, the TLLPD offers a tunable single-band operation at 3 GHz and 5.2 GHz bands, in which 23% and 17% bandwidths are observed, respectively, where |S 11 |<−10 dB criterion with 50Ω system impedance is considered.In addition, the computed radiation patterns of the TLLPD design are shown in Fig...
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