Tunable loop-loaded printed dipole antenna design

Abstract

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...

Dual-band loop-loaded printed dipole array with a corporate balun/feed structure

“…In addition, the computed cross-polarisation levels at broadside are 220, 215 and 212 dB for the 1 × 1, 2 × 2 and 4 × 4 arrays, respectively, at 3 and 5.5 GHz. Moreover, we carried out radiation pattern measurements for the 4 × 4 LLPD array in an anechoic chamber using ETS-Lindgren 3117 DRG horn antenna (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). The corresponding measured patterns at 3 and 5.5 GHz along with the simulated data are displayed in Fig.…”

“…1, the LLPD antenna is excited by a microstrip balun-feed structure placed vertically just underneath the dipole-gap. We remark that the dipoles cannot perform in the way as predicted when they are excited directly by a coaxial feed [18], which is because of inherit unbalanced current excitation by the coax. To overcome this undesired phenomenon, a balun (balanced-to-unbalanced) structure is required in the coax-fed dipole applications in order to match the unbalanced coaxial transmission line to the balanced two-wire line, that is, the dipole in our case.…”

Switchable loop‐loaded printed dipole antenna with a balun/feed structure

“…The dipole element is excited by a balun-feed structure placed vertically underneath the dipole-gap as seen in Figure 1. We note that in practice the dipole excited directly by a coaxialfeed element would have a degraded performance due to inherent unbalanced current flow on the coax [10]. To avoid this undesired phenomenon, the balun-feed structure compatible with the dipole configuration [11,12] is considered here.…”

“…Dual bandpass filters (BPFs) have become attractive components for wireless communication in recent years. Several design approaches can be found in the literatures [1][2][3][4][5][6][7][8][9][10]. In general, a dual-band filter can be realized by cascading connection of simple BPFs with large bandwidth and one bandstop filter [1].…”

A Reconfigurable Cedar-Shaped Microstrip Antenna for Wireless Applications

“…A Vivaldi antenna is used by the authors in [11] to incorporate four pairs of p-i-n diodes. A dual frequency reconfigurable TLLPD (tunable loop-loaded printed dipole) is reported in [12]. The authors in [13] present an antenna with band notch reconfigurability based on complementary split-ring resonators (CSRRs) and split-ring resonators (SRRs).…”