Jun H. Choi

Dual-band leaky wave antenna with filtering capability based on extended-composite right/left-handed transmission lines

In this paper, the design and implementation of a novel dual-band leaky wave antenna (LWA) with continuous backward to forward scanning capability for each band is presented. The structure is based on extended-composite right/left-handed transmission lines (E-CRLH TL) implemented in substrate integrated waveguide (SIW) technology. As compared to other reported dual-band LWAs based on E-CRLH TLs, the structure presented in this work is designed on the basis of a circuit model that predicts its behavior and allows better understanding and controllability of the dispersion diagram. In addition, the reported dual-band LWA is a multi-functional device, able to inherently filter unwanted signals lying outside the antenna operating frequency bands.

Frequency-Scanning Phased-Array Feed Network Based on Composite Right/Left-Handed Transmission Lines

This paper presents an all-passive phased-array feed network based on composite right/left handed (CRLH) transmission lines (TLs). A CRLH TL enables systematic engineering of the phase response providing phase advance in addition to phase delay. When utilized in a phased-array feed network, an all-passive 1-D frequency-scanning array can be designed with a large scanning angle range toward both positive and negative elevation angles. This unique feature cannot be realized using conventional delay lines or dispersive lines that do not contain left-handed properties. Also, unlike the previously studied CRLH-based leaky-wave antennas that provide similar 1-D continuous frequency-scanning functionality, the proposed method completely decouples the radiating antenna element from the array factor; thereby providing extra design freedom and enhanced radiation performance. To validate the added advantage, we use the proposed CRLH-based phased-array feed network to demonstrate simultaneous controllability of the radiated polarization and array current amplitude distribution.

Dual-Band Composite Right/Left-Handed (CRLH) Phased-Array Antenna

A dual-band, all-passive phased-array feed network using composite right/left-handed (CRLH) dispersive lines is presented. This single feed network provides phase advance in addition to phase delay, which allows dual-band operation capable of directing the radiated beam to arbitrary directions. A simple design guide for a dual-band CRLH-based phased array is provided, and the arrays performance is verified experimentally. The simulated and measured results show good agreement. This proposed array network is compatible with any type of conventional dual-band antennas.

Dispersion Analysis and Design of Planar Electromagnetic Bandgap Ground Plane for Broadband Common-Mode Suppression

A planar electromagnetic bandgap (EBG) structure designed for broadband common-mode suppression is proposed. A uniplanar compact photonic-bandgap (UC-PBG) structure with periodic center slots is etched on the ground plane to obtain broadband common mode suppression while minimally disturbing the differential signal within the designed bandwidth. Dispersion analysis has been conducted for both common (even) and differential (odd) mode signals. Good signal integrity is observed in both simulated and measured results. The fractional bandwidth of the proposed EBG ground plane is around 70% with common-mode suppression below -20 dB. The proposed EBG ground planes may be applicable for systems requiring low-cost and simple solutions in designing high-speed differential interlinks operating above 5 Gbps.

A Compact Single Radiator CRLH-Inspired Circularly Polarized Leaky-Wave Antenna Based on Substrate-Integrated Waveguide

A circularly polarized (CP) CRLH-inspired leaky-wave antenna (LWA) based on substrate-integrated waveguide (SIW) and microstrip delay line is presented. The unit-cell of the proposed periodic antenna consists of two conventional CRLH SIW cells and two quarterwavelength microstrip lines. The interdigital slots on the CRLH SIW are rotated at +45° and -45° with respect to the wave propagation direction and separated by 90° to create circular polarization. Utilizing the microstrip line instead of the SIW delay section, the total size of the live unit-cell antenna is reduced by 24.4% in comparison to the previous single radiator CP LWA. Furthermore, microstrip lines provide improved matching for broadside radiation as well as better CP purity. The unitcell characteristics are investigated in detail through dispersion and Bloch impedance analysis. In addition, space harmonic analysis is carried out to explain the radiation mechanism of the proposed antenna. The proposed CRLH-inspired SIW CP antenna operates from 4.2 to 4.85 GHz and frequency scans from -25° to 26° along the elevation angle. Axial ratio is maintained below 3 dB throughout the operating frequency. The measured results show good agreement with the simulated results.

Magnetic-Current-Loop-Induced Electric Dipole Antenna Based on Substrate Integrated Waveguide Cavity

In this letter, a novel dipole antenna based on substrate integrated waveguides (SIWs) is presented. The dipole antenna radiates through the equivalent magnetic current loops on the top and bottom annular ring slot that is excited by the fundamental mode of the SIW cavity. Therefore, the proposed dipole possesses a vertical polarization perpendicular to the metallic plane. Moreover, thanks to normal electric field, the proposed dipole is less affected by the ground plane size and surrounding metal. The proposed antenna topology provides a very easy way to realize vertical dipole antenna by just using planar circuits and is promising to be used as a fundamental element to realize antenna arrays.

A circularly polarized single radiator Leaky-wave antenna based on CRLH-inspired substrate integrated waveguide

A novel circularly polarized (CP) composite right/left-handed (CRLH) inspired substrate integrated waveguide (SIW) Leaky-wave antenna (LWA) is presented. A circularly polarized wave is created by adjacently placing two linearly polarized intergidital slots in an orthogonal direction with respect to each other with 90° phase difference. The proposed antenna provides circular polarized waves in addition to the unique frequency scanning property of CRLH SIW antenna, using a single radiating element. To verify the proposed method, the prototype of the antenna is designed and fabricated.

Bi-directional active and passive meandered circularly polarized CRLH-inspired leaky-wave antennas based on substrate integrated waveguide

Bi-directional active and passive meandered circularly polarized (CP) composite right/left-handed (CRLH) inspired substrate integrated waveguide (SIW) based leaky-wave antennas (LWAs) are presented. By meandering the microstrip line, the dimension of the proposed five-cell antenna along the scanning plane is reduced by 33.5% compared to the original CP CRLH LWA based on SIW [1]. Furthermore, incorporating the bi-directional amplifiers, the current distribution of the antenna is manipulated to control the radiation characteristics. The proposed active meandered CP CRLH LWA supports both transmitting and receiving operation while delivering enhanced spatial resolution.

Folded Strip/Slot Antenna with Extended Bandwidth for WLAN Application

A compact and novel printed antenna for 2.4-GHz WLAN/Zigbee/Bluetooth applications is proposed in this letter. To extend the bandwidth, a strip mode and a slot mode are combined together, which generate a dual-mode response inside the radiating band. To miniaturize the overall size, the structure is folded in order to fully utilize the available antenna space. The antenna is fabricated on a 1-mm FR4 board and excited by an SMA connector using a short microstrip line. It achieves a –10-dB bandwidth of 5.09% with a compact size of 0.073 <italic> λ</italic>₀ × 0.052 <italic>λ</italic>₀ × 0.008 <italic>λ </italic>₀ (9.2 × 6.5 × 1 mm³) and an in-band radiation efficiency above 73%. It is small and low-profile, which can be fabricated at a low cost using the standard printed circuit board (PCB) process. It shows good radiation performance and therefore is suitable for applications in Internet of Things and smart home devices.

High directivity negative-resistance composite right/left-handed leaky-wave antenna

A novel negative-resistance composite right/left-handed (NR-CRLH) leaky-wave antenna (LWA) is presented. The conventional CRLH unit cell is made configurable by using the negative resistance (NR) circuit. An LWA constituted by the proposed unit cells allows manipulation of the current distributions over the radiating surface of the antenna. Consequently, the radiation pattern, and directivity can be adjusted to the desired values. The fabricated prototype of the proposed NR-CRLH LWA demonstrates enhanced directivity compared to the conventional all passive CRLH LWA. The proposed method provides simple current amplitude control while minimally influencing the desired dispersive/transmission characteristics of the LWA.