Composite Right/left-handed Unit Cell Research Articles

CRLH Leaky-Wave Antenna with High Gain and Wide Beam-Scanning Angle for 5G mmWave Applications

In this paper, a novel composite right-/left-handed (CRLH) leaky-wave antenna with a simple structure, low cost, high gain, and wide beam-scanning range performance for the millimeter wave (mmWave) band. The proposed antenna comprises a series-fed array of asymmetrically slotted elliptical CRLH unit cells loaded with a short-circuit stub. By optimizing the length of the stub, the condition of the CRLH structure is balanced to enable beam scanning from the backward to the forward direction within the mmWave band. The proposed antenna exhibits a wide beam-scanning angle of 112° (-60° to 52°), coupled with high gain and radiation efficiency at the designated band. Furthermore, it is fabricated on a traditional microwave substrate, Rogers RT/duroid 5880, thus offering a cost-effective approach to streamlining the manufacturing process. The measurement results confirmed a peak realized gain of 16.8 dBi. The excellent performance achieved using a low-cost design makes the proposed antenna attractive for 5G mmWave applications.

Composite Right/Left-Handed Leaky-Wave Antenna with Electrical Beam Scanning Using Thin-Film Ferroelectric Capacitors

This article presents a wide-angle-scanning leaky-wave antenna (LWA) based on a composite right/left-handed (CRLH) transmission line. In contrast to traditional semiconductor elements, thin-film ferroelectric capacitors were implemented in the CRLH unit cells to enable electric beam scanning. The proposed CRLH LWA has a single-layer design without metalized vias and is compatible with PCB and thin-film technologies. To fabricate the CRLH LWA prototype, dielectric material substrates and thin-film ferroelectric capacitors were manufactured, and their characteristics were investigated. Double-sided metalized fluoroplast-4 reinforced with fiberglass with a permittivity of 2.5 was used as a substrate for CRLH LWA prototyping. A solid solution of barium strontium titanate (BaxSr1−xTiO3) with a composition of x=0.3 was used as a ferroelectric material in electrically tunable capacitors. The characteristics of the manufactured ferroelectric thin-film capacitors were measured at a frequency of 1 GHz using the resonance method. The capacitors have a tunability of about two and a quality factor of about 50. The antenna prototype consists of ten units with a total length of 1.25 wavelengths at the operating frequency of close to 2.4 GHz. The experimental results demonstrate that the main beam can be shifted within the range of −40 to 16 degrees and has a gain of up to 3.2 dB. The simple design, low cost, and excellent wide-angle scanning make the proposed CRLH LWA viable in wireless communication systems.

Electronic Beam Steering Metamaterial Antenna with Dual-Tuned Mode of Liquid Crystal Material

In this study, a dual-tuned mode of liquid crystal (LC) material was proposed and adopted on reconfigurable metamaterial antennas to expand the fixed-frequency beam-steering range. The novel dual-tuned mode of the LC is composed of double LC layers combined with composite right/left-handed (CRLH) transmission line theory. Through a multi-separated metal layer, the double LC layers can be loaded with controllable bias voltage independently. Therefore, the LC material exhibits four extreme states, among which the permittivity of LC can be varied linearly. On the strength of the dual-tuned mode of LC, a CRLH unit cell is elaborately designed on three-layer substrates with balanced dispersion values under arbitrary LC state. Then five CRLH unit cells are cascaded to form an electronically controlled beam-steering CRLH metamaterial antenna on a downlink Ku satellite communication band with dual-tuned characteristics. The simulated results demonstrate that the metamaterial antenna features' continuous electronic beam-steering capacity from broadside to -35° at 14.4 GHz. Furthermore, the beam-steering properties are implemented in a broad frequency band from 13.8 GHz to 17 GHz, with good impedance matching. The proposed dual-tuned mode can make the regulation of LC material more flexible and enlarge the beam-steering range simultaneously.

Composite Right/Left-Handed Leaky-Wave Antenna With High Scanning Rate

The scanning rate of a composite right/left-handed (CRLH) leaky-wave antenna (LWA) is usually determined by the dispersive behavior of the corresponding CRLH unit cell. In this letter, a novel CRLH unit cell with high dispersive behavior is proposed and investigated. The unit cell is formed by four stubs embedded in a rectangular ring patch, which is grounded with several metal vias. The right-handed characteristic is enhanced by the ring patch, while the left-handed characteristic is reduced by the vias and the gaps between the patch and the stubs. Then, the unit cell is applied to design an LWA with high scanning rate. The measured result shows that the seamless scanning angle of the antenna prototype is 130° (−65° to +65°) within a frequency range from 9.3 to 9.93 GHz (i.e., 6.6% for fractional bandwidth). Therefore, the proposed LWA antenna is with a high scanning rate up to 19.7°/%BW.

A Design of Compact Meta-material CRLH Antenna for Wireless Applications

This article presents a compact design of a composite-right-left-handed (CRLH) antenna for wireless applications. The antenna is fed using a coplanar waveguide (CPW) feed structure. The CRLH-antenna is comprised of one CRLH unit cell. The CRLH unit cell has a series capacitance (interdigital capacitor) and a shunt inductor (stub meander inductor). The antenna achieves compactness with a small size of 16.5 mm × 26 mm × 1.6 mm, thanks to the CRLH features such as nonlinear phase. The proposed antenna achieves a size reduction of better than 50 % with respect to the microstrip patch antenna operated at the same frequency band. The operating frequency band of the proposed antenna is from 5.83GHz to 6.3 GHz for WLAN applications, dedicated short range communications (DSRC), and intelligent transportation systems (ITS). Also, the antenna fulfills a radiation performance of omnidirectional pattern. To confirm the antenna design performances, a prototype is fabricated, and the reflection coefficient and radiation patterns are measured. Furthermore, the measured results have a good match with the simulation results.

A modified composite right/left‐handed unit cell for multiband applications

AbstractA new planar 3‐band composite right/left‐handed (CRLH) unit cell is presented using an interdigital capacitor, two grounded stubs and etching a defected ground structure on the ground plane. A 3‐band filter is designed using this CRLH unit cell. In addition, with nonlinear dispersion relation of the 3‐band unit cell, it can be used as a hexa‐band quarter wave impedance transformer. Using this functionality, a planar hexa‐band power splitter is designed with relatively good performance. A fabricated prototype of the power divider is measured and the experimental results indicate that the power divider achieved better than 10 dB of return loss and the insertion loss is better than 6 dB over six‐frequency bands.

Wide-Angle Frequency-Scanning Array Antenna Using Dual-Layer Finger Connected Interdigital Capacitor Based CRLH Unit Cell

In this paper, a wide-angle frequency-scanning array antenna is presented for three-dimensional (3D) radar. Initially, a modified composite right/left-handed (CRLH) unit cell based on a dual-layer finger-connected interdigital capacitor (FCIDC) is analyzed. Compared with its conventional counterpart, the proposed unit cell eliminates the undesired high-order resonances and has a lower right/left-handed passband. Then, a broadband frequency-scanning feeding network, which has a large scanning angle, is designed using the proposed CRLH unit cell. The responses of the four output ports indicate that the network can offer desired amplitude and phase difference to scan towards both negative and positive elevation angles. To validate its performance, a tightly coupled planar quasi-Yagi antenna array is fed to synthesize an array antenna. The measured results show that the designed array antenna has an impedance bandwidth ($\vert \text{S}_{11}\vert <; -10$ dB) of 118.7% (2.55-10 GHz) and gains larger than 5dBi in the bulk of the band. Besides, the radiated beam can scan from -47° to 46° continuously when the frequency ranges from 3GHz to 9GHz.

A broadband and excellent flatness power amplifier with novel‐designed band‐pass filter based on composite right/left‐handed unit cell

AbstractIn this paper, a broadband and excellent flatness power amplifier (PA) with a novel‐designed band‐pass filter based on composite right/left‐handed (CRLH) unit cell structure is proposed. On studying the structure of CRLH unit cell, a way to enhance PA bandwidth, gain flatness, and power‐added efficiency (PAE) flatness is explored. The novel‐designed CRLH unit cell structure is studied and applied in PA design. The measurements show that the PA has an output power of greater than 40 dBm, a gain flatness of 0.5 dB, and a PAE flatness of 4.4% within 1.7‐3.1 GHz bandwidth.

Composite Right/Left-Handed Leaky-Wave Antennas for Wide-Angle Beam Scanning With Flexibly Chosen Frequency Range

A composite right/left-handed (CRLH) leaky-wave antenna (LWA) can effectively scan the radiation beam from backward-to-forward direction. However, in most cases, a large range of frequency sweep is required to achieve a wide-angle beam scan, which could limit their applications. An in-depth study is conducted on an equivalent circuit model for a CRLH LWA unit cell to find the controlling parameters on the frequency sweeping range. A systematic design guideline is given for a CRLH LWA for a wide-angle beam scan in a flexibly chosen frequency range. It is shown that beam scanning by sweeping frequency in a target range can be achieved by systematically designing the unit cell parameters. To verify our approach, a novel CRLH unit cell is developed and used to design an LWA for a wide-angle beam scan in a narrow frequency range. Finally, the concept is validated through realization of the antenna and its measurement. The measured results show that the antenna prototype can scan its beam from −56° to +51° when frequency sweeps from 5.1 to 6.11 GHz (i.e., 18.02% of fractional bandwidth).

Approach for miniaturisation of planar antenna based on CRLH structure

The need to miniaturise antenna size comes from that most mobile platforms having limited space for all the antennas required in the constantly growing wireless systems. Metamaterial-based transmission line, commonly referred to, composite right/left-handed (CRLH) transmission line has a unique feature of supporting an infinite-wavelength wave at a finite and non-zero frequency. As a result, zero- and negative-order resonance can be achieved. This Letter investigates the application of this concept for miniaturisation of planar antenna based on CRLH structure implemented with the microstrip line technology by using zero and high negative value of the phase constant ( β ). The concept is realised by applying microstrip-bends approach in the design of the CRLH unit cell in which high reactance can be provided by the constitutive parameters of the unit cell. Analytical results have validated the design concept and the modified CRLH unit cell based microstrip-fed monopole antenna, showing a high level of miniaturisation up to 85% from the conventional half-wavelength antenna. These results were obtained by CST Microwave Studio and verified by experimental data.

Matrix Power Amplifier With Open-Circuit Composite Right-/Left-Handed Transmission Line

A distributed matrix power amplifier with open-circuit (O.C) composite right-/left-handed (CRLH) transmission line (TL) is proposed. The matrix structure along with the zero phase-shift CRLH TL and the O.C termination of TLs have led to the design of reduced size, high-gain matrix amplifier with improved power performances. A new small size planar CRLH unit cell is presented. The maximum gain of 21.5 dB at the center frequency is obtained. The measured 1-dB gain compression (P1-dB) is 26 dBm, and the maximum power added efficiency is 29%. Better gain and P1-dB are achieved compared to the previously published narrowband distributed amplifiers. The amplifier has good linearity according to the measured input intercept point (18 dBm) and the output intercept point (39 dBm).

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

A compact single-radiator circularly polarized (CP) leaky-wave antenna (LWA) based on composite right/left-handed (CRLH) transmission line is presented. The proposed antenna is based on substrate-integrated waveguide (SIW), and its unit cell consists of a T-shaped interdigital slot, which provides a CRLH property, a proper CP, and also effective compactness for the full-length LWA. The proposed LWA provides beam scanning from −19° to +84° over the frequency range of 7.35–10.15 GHz, while maintaining a good CP. By providing the balanced condition for the CRLH unit cell, a continuous backward-to-forward scanning including broadside is achieved. The maximum gain of the LWA is 8.95 dB which is satisfactory, considering the compactness of the antenna. Moreover, the radiation efficiency has an average of 85.7% over the operating frequency band. The measurement results are in good agreement with the simulation ones and show considerable advantages over the SIW-based CP LWAs proposed in the recent literature.

Metamaterial‐based compact UWB planar monopole antennas

AbstractIn this article, novel compact UWB antennas based on loading of via less composite right/left‐handed (CRLH) unit cells are presented. Two novel metamaterials (MTM)‐based CRLH‐TL unit cells have been designed. The dispersion characteristics of the proposed unit cells are numerically calculated which follows CRLH properties. We designed a via‐free version of the CRLH unit cell by using virtual ground concept which simplifies the fabrication process and decreases the costs. The additional impedance matching network has been eliminated by using the optimum location of feed offset. The resulting double via less CRLH unit cells loaded antenna's bandwidths are improved by proper realizing the unit cell parameters and merging of ZOR mode to other lower and higher order modes. The proposed antennas have compact dimension 25 × 15 × 1.6 mm3. The two proposed antennas have UWB characteristics such as 109% and 125% fractional bandwidth, respectively. The measured gain and efficiency have been obtained with desired values for UWB applications. Good agreement has been observed between simulated and measured results.

Extended Aperture Miniature Antenna Based on CRLH Metamaterials for Wireless Communication Systems Operating Over UHF to C‐Band

AbstractThis paper presents a simple technique to extend the aperture of planar composite right/left‐handed (CRLH) metamaterial antennas with minimal impact on the antenna's dimensions. Unlike most CRLH antenna structures the proposed antenna is via‐free. The proposed antenna is shown to operate over a wideband from UHF to C‐band with good radiation characteristics. The antenna configuration consists of a vertically stacked CRLH unit cells comprising a patch and meandered lines, where the patch is engraved with an S‐shaped slot. The design uses minimal ground plane area. The meander line inductance is grounded using coplanar waveguide (CPW) ground which eliminates conventional CRLH transmission line metallic via into ground plane. The antenna is feed through a coplanar waveguide (CPW) match stub that is electromagnetically coupled to the unit cells. Antenna dimensions are 17.5 × 32.15 × 1.6 mm3, which corresponds to 0.204 λ0 × 0.375 λ0 × 0.018 λ0 where free‐space wavelength (λ0) is 3.5 GHz. Parametric study enabled the optimization of the antenna performance in terms of impedance bandwidth, radiation gain, and radiation efficiency. Measured results confirm that the antenna can operate from 850 MHz to 7.90 GHz, which is equivalent to a fractional bandwidth of 161.14%. The antenna has a maximum gain and radiation efficiency of 5.12 dBi and ~80%, respectively, at 3.5 GHz.

A Miniaturized Reconfigurable CRLH Leaky-Wave Antenna Using Complementary Split-Ring Resonators

Composite Right-/Left-Handed (CRLH) Leaky-Wave Antennas (LWAs) are a class of radiating elements characterized by an electronically steerable radiation pattern. The design is comprised of a cascade of CRLH unit cells populated with varactor diodes. By varying the voltage across the varactor diodes, the antenna can steer its directional beam from broadside to backward and forward end-fire directions. In this paper, we discuss the design and experimental analysis of a miniaturized CRLH Leaky-Wave Antenna for the 2.4 GHz WiFi band. The miniaturization is achieved by etching Complementary Split-Ring Resonator (CSRR) underneath each CRLH unit cell. As opposed to the conventional LWA designs, we take advantage of a LWA layout that does not require thin interdigital capacitors; thus we significantly reduce the PCB manufacturing constraints required to achieve size reduction. The experimental results were compared with a nonminiaturized prototype in order to evaluate the differences in impedance and radiation characteristics. The proposed antenna is a significant achievement because it will enable CRLH LWAs to be a viable technology not only for wireless access points, but also potentially for mobile devices.

CRLH structure‐based high‐impedance surface for performance enhancement of planar antennas

A composite right/left-handed (CRLH) structure-based high-impedance surface (HIS) is investigated to improve gain and front-to-back ratio of planar microstrip antennas. An unbalanced CRLH unit cell with a wide band-stop region from 2.0 to 6.44 GHz is modelled and designed for HIS to enhance the antenna performance. A novel via-less structure composed of an interdigital capacitor and four spiral arms is used for the microstrip implementation of the CRLH unit cell. The HIS is formed by the repetition of the unbalanced CRLH unit cells in two-dimensional form. The microstrip patch antennas operating at three different frequencies: 2.34, 3.77 and 5.64 GHz in the band-stop region of the HIS are designed with and without HIS to compare the antenna performances. An increase in gain of 1.91, 2.03 and 0.7 dB and an improvement in the front-to-back ratio of 4.9, 6.0 and 4.2 dB are achieved for the patch antennas operating at 2.34, 3.77 and 5.64 GHz, respectively. To demonstrate the effectiveness of HIS, a patch antenna over HIS is fabricated and measured results show good correlation with the simulated results. An overall antenna size at 2.26 GHz is 0.378λ o × 0.303λ o × 0.012λ o.

CRLH unit cell loaded quad‐band monopole antenna

ABSTRACTA novel design of quad‐band monopole planar antenna has been presented in this letter. Initially, a dual‐band monopole antenna is excited at two distinct frequencies using monopoles of two different lengths in the same design. Furthermore, the longer monopole with lower operating frequency is loaded with composite right/left handed (CRLH) unit cell, due to which two additional operating narrowband frequencies are obtained. The special characteristic of the CRLH unit cell lies in the design trick of the meandered stub inductor, a significant length of which is adjusted by doubly folding it within a smaller area leading to an electrically smaller unit cell size. The resonant frequencies of the fabricated quad‐band antenna are found at 0.85, 1.61, 2.42, and 3.55 GHz. The prototype of the proposed antenna is fabricated and measured. The measured results are in good agreement with the simulated results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:653–658, 2016

A Three-Band Substrate Integrated Waveguide Leaky-Wave Antenna Based on Composite Right/Left-Handed Structure

In this communication, the design and implementation of a three-band substrate integrated waveguide (SIW) leaky-wave antenna (LWA) based on the composite right/left-handed (CRLH) structure is presented. CRLH unit cell of the proposed antenna is composed of two adjacent interdigital slots with two vias between them. Two CRLH bands along with a new right-handed (RH) band between them are achieved through this structure. The first CRLH band (7.1–10.75 GHz) is balanced and the second one (15.1–21.75 GHz) is unbalanced with 0.25-GHz stop band. Beam scan angle in the first CRLH band is from $- 78^\circ $ to $+ 78^\circ $ , in the second one from $- 40^\circ $ to $+ 20^\circ $ and in the new RH band (12.6–13.4 GHz) from $+ 22^\circ $ to $+ 54^\circ $ . Antenna radiation efficiency in the first CRLH band is about 90%. Simulated and measured results are compared and there is a good agreement between them.

High power efficiency distributed oscillator based on composite-right-/left-handed unit cells

A microwave oscillator topology based on CRLH (Composite Right-/Left-Handed) unit cells is analyzed theoretically and experimentally tested. The oscillator consists of a CRLH based distributed amplifier and a positive feedback realized by a simple transmission line. The oscillator has two output ports, where the power levels are practically the same. For this topology, we have found the oscillation condition and we demonstrate that each transistor gives the same contribution to the power delivered at the two output ports, in this way, the output power is maximized. The oscillator has been designed for a frequency of oscillation of 2.8 GHz and fabricated in hybrid technology, by using InGaAs HEMTs and microstrip lines. The measured powers at the two output ports are equal to 12.6 dBm and 10.4 dBm, the small difference between these values being given by the insertion loss of the gate line. The experimental frequency of oscillation is 2.77 GHz, with a difference of less than 1% in comparison with the expected value. Due to the frequency selectivity of the CRLH unit cells, numerical simulations predict low phase noise for this configuration of oscillator.

Multiband Printed Metamaterial Inverted-F Antenna (IFA) for USB Applications

A printed multiband coplanar waveguide (CPW)-fed inverted-F antenna (IFA) is presented in this letter. The concept of loading a printed-IFA with composite right/left-handed (CRLH) unit cells is theoretically and experimentally investigated by using electromagnetic simulators, Advanced Design System (ADS) and High Frequency Structure Simulator (HFSS), for universal serial bus (USB) applications. The proposed USB antenna structure consists of a CPW printed-IFA with two arms loaded by two CRLH unit cells to achieve two extra operating bands in addition to the two fundamental resonant frequencies of two IFA arms. The structure is designed to operate at GSM 1.8 GHz, Bluetooth 2.4 GHz, WiMAX 3.5 GHz, and WLAN 5.2 GHz. Measured and simulated results are in good agreement with the theoretical predictions.