Zeroth-order Resonance Research Articles

Symmetric CRLH-TL filter based dual band microstrip antenna design approach

This paper presents a novel filter-based analysis for the conventional rectangular patch antenna (RPA) using the Composite Right/Left-Handed Transmission Line (CRLH-TL) theory. We introduce two circuit models for RPA, described by lumped components and transmission line (TL) elements. An RPA is considered a Symmetric CRLH-TL (SCRLH-TL). We validated the analysis by comparing the circuit model and full-wave analysis simulation results. The TL circuit model error in the full-wave analysis was less than 5%. A dual-band Zeroth-Order Resonant (ZOR) antenna is designed and manufactured based on the introduced Lumped element circuit model, which exhibits filtering characteristics in both bands. We obtain the antenna circuit model by incorporating the RPA lump circuit model with LC resonators. We implemented the antenna structure by combining the RPA and complementary split-ring resonators (CSRR) modeled by the LC resonators. We initialized the antenna center frequency bands for WiMAX 2.45 GHz and 3.60 GHz. The CSRRs control the configuration of the center frequencies. The simulation and measured results are in good agreement. The proposed antenna dimensions are 0.66×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}0.66×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}0.012 λg\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda _g$$\\end{document} at 2.45 GHz (43.22×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}43.22×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}0.81 mm3). The measured gains are 3.47 dB and 4.64 dB for 2.45 GHz and 3.60 GHz, respectively. Two radiation nulls were observed at 2.09 GHz and 2.98 GHz for the 2.45 GHz band and one radiation null at 3.45 GHz for the 3.60 GHz band. Also, the fractional bandwidth is 4.03% and 1.39%, respectively. The radiation pattern is nearly omnidirectional. The simulated efficiency is 90% for 2.45 GHz and 87% for 3.60 GHz frequency bands.

Purcell gain equalized zero-mode waveguide

We refresh the design of zero-mode waveguides (ZMWs) by introducing metamaterials that makes the zeroth order resonant mode existence. Of particular importance, the resulting electromagnetic field exhibits nearly constant distribution but not a trivial solution of Maxwell’s equation, showing great advantage to equalize the excitation rate of molecules throughout the waveguides. A closed form expression for the wave impedance is derived which is verified by the finite-difference time-domain simulations. Benefitted from the cavity Purcell effect which is lacking in existing ZMWs, fluorescence amplification and lifetime reduction are simultaneously enhanced. A practical design where the excitation volume reduced down to sub-zeptoliter and the fluorescence lifetime shortened to picosecond scale is illustrated. This result makes single molecule real time (SMRT) sensing of biochemical reactions at biophysically relevant concentrations (~ μM) possible, combining off-the-shelf ultrafast lasers.

Active Metamaterial Antenna with Tunable Zeroth-Order Resonances for Narrowband Internet of Things

With unique electromagnetic properties, metamaterials (MTMs) provide more freedom for antenna design, particularly with the combination of active-device-enabling effective tuning. By integrating the active device and the periodical cells of MTMs, the electromagnetic characteristics of individual cells can be manipulated independently, thereby realizing multiple tunable states for MTM antennas consisting of several periodical cells. In this paper, we employ active devices such as PIN diodes to each periodical cell to tune each cell independently, thereby realizing 36 tunable zeroth-order resonances (ZORs) for the metamaterial antenna with three cells in a frequency range of 4.48–5.34 GHz. Moreover, each ZOR has a bandwidth as narrow as 0.09 GHz, indicating that the tunable ZOR antenna can be potentially applied to 5G Narrowband Internet of Things (NB-IoT).

A high-gain dual-band shared-aperture array integrating zero-order-resonance patch and higher-order metasurface antenna

This letter proposes a high-gain shared-aperture array for vehicular communications which integrates the hybrid zeroth-order-resonance (ZOR) patch and the higher-order metasurface antenna (MA). In terms of each array element, four hybrid ZOR patches with shorting pins form a metasurface which is fed by slot coupling. Different from some reported designs which have more high-frequency elements than low-frequency ones, the whole array is composed of 4 times 4 hybrid ZOR patches operating in C band (4.74–5.12 GHz) and 2 times 2 MAs working in Ku band (13.0–14.0 GHz). Such a layout brings that the designed array has the benefit to reduce Ku-band loss. Measure results validate the dual-band operation and show that the antenna has its peak gains of 12.7 dBi and 17.2 dBi in these two bands, respectively, which can support vehicle-to-base station and vehicle-to-satellite communications.

Nonzero-Order Resonances in Single-Beam Spin-Exchange Relaxation-Free Magnetometers

Zero-field optically pumped magnetometers operating in the spin-exchange relaxation-free (SERF) regime have been extensively studied, and usually depend on zeroth-order parametric resonance to measure the magnetic field. However, the studies conducted on this topic lack thorough analyses and in-depth discussion of nonzero-order magnetic resonances in single-beam SERF magnetometers. In this paper, we analyzed the nonzero-order resonance, especially the first-order resonance, based on a single-beam SERF magnetometer, and discussed its various applications. A comprehensive theoretical analysis and experiments were conducted with respect to multiple functions, including nonzero finite magnetic field measurements, spin polarization measurement, and in situ coil constant calibration. The results showed that first-order resonance can be utilized for nonzerofinite magnetic field measurements, and the spin polarization of alkali-metal atoms can be determined by measuring the slowing-down factor using the resonance condition. Furthermore, acquiring the first-order resonance point at an equivalent zero pump light power through fitting offers an approach for quick and precise in situ coil constant calibration. This study contributes to the applications of SERF magnetometers in nonzero finite magnetic fields.

Channel Selectivity of Satellite Transponders with the Antenna Combined with a Size-Reduced Metallic Waveguide Bandpass Filter Having Thin Metamaterial Resonators.

Global and intercontinental networking relies on satellite communication. Its wireless communication system always has antennas and their feed assembly comprising waveguides. This makes the satellite payload heavy and costly. In this paper, a novel method is proposed to effectively reduce the size of a waveguide bandpass filter (BPF). Because the metallic cavities make the conventional waveguide end up with a large geometry, especially for high-order BPFs, very compact waveguide-type resonators having metamaterial zeroth-order resonance (WG-ZOR) are designed on the cross-section of the waveguide and substituted for the cavities. While the cavities are half-wavelength resonators, the WG-ZOR is shorter than one eighth of a wavelength. A substantial reduction in size and weight of the waveguide filter is observed as the resonators are cascaded in series through coupling elements in the X-band much longer than K- or Ka-band. An X-band of 7.25~7.75 GHz is chosen to verify the method as the passband with attenuation of 40 dB at 7.00 GHz and 8.00 GHz as the roll-off in the stopband. The BPF is manufactured using the CNC milling technique. The design is carried out with geometrical parameters, not of the level of 10 μm, but the level of 100 μm, which is good for manufacturers but a big challenge for component designers. The measurement of the manufactured metal waveguide filter reveals that the passband has about ≤1 dB and ≤-15 dB as insertion loss and reflection coefficient and the stopband has ≤-40 dB as attenuation, which are in good agreement with the results of the circuit and simulation. The proposed filter has a length of 3.5 λg as the eighth-order BPF, but the conventional waveguide is 5 λg as the seventh-order BPF for the same area of the cross-section. This metamaterial BPF is combined with a horn antenna. The filter enables the wide-band antenna to distinguish the band of transmission from that of noise suppression. This channel selectivity is obviously observed by the filter integrated antenna test.

Development of VHF-Band Conformal Antenna for UAV Mounting

In this paper, a VHF band conformal antenna for UAV mounting was developed. The proposed antenna was designed as an shape-adaptive structure by minimizing the antenna height to be advantageous in RCS reduction performance. As for the antenna radiator, the outer radiator was arranged around the inner radiator to apply the CRLH zeroth-order resonance structure. With this structure, the height of the antenna was minimized, and it was reduced by about 70 % compared to the existing blade antenna. In addition, for impedance matching, the intermediate frequency bandwidth of the VHF band was improved through the sleeve pin of the inner radiator, and the low frequency bandwidth of the VHF band was improved by applying an EMI shielding gasket to the shorting pin of the outer radiator. The proposed antenna was manufactured and measured to verify the performance of the device and the performance after UAV mounting. As a result, the standard was satisfied for the operating frequency.

Effective Size Reduction of the Metallic Waveguide Bandpass Filter with Metamaterial Resonators and Its 3D-Printed Version.

In this paper, a novel method is proposed to effectively reduce the size of a waveguide bandpass filter (BPF). Because the metallic cavities make the conventional waveguide end up with a large geometry, especially for high-order BPFs, very compact waveguide-type resonators having metamaterial zeroth-order resonance (WG ZOR) are designed on the cross section of the waveguide and substituted for the cavities. While the cavities are half-wavelength resonators, the WG ZOR is shorter than one-eighth of a wavelength. A substantial reduction in the size and weight of the waveguide filter is observed as the resonators are cascaded in series through coupling elements in the X-band that is much longer than that in K- or Ka-bands. The proposed metamaterial filter is realized as a 3D-printed structure to be lighter and thus more suitable for low earth orbit (LEO) satellites. An X-band of 7.25-7.75 GHz is chosen to verify the method as the passband with an attenuation of 40 dB at 7.00 GHz and 8.00 GHz as the roll-off in the stopband. The BPF is manufactured in two ways, namely the CNC-milling technique and metal coating-added 3D printing. The design is carried out with a geometrical parameter of not 10-2 mm but rather 10-1 mm, which is good for manufacturers but challenging for component designers. The measurement of the manufactured metal waveguide filters reveals that the passband has about ≤1 dB and ≤-15 dB as the insertion loss and the reflection coefficient, respectively, and the stopband has an attenuation of ≤-40 dB, which are in good agreement with the results of the circuit and the simulation. The proposed filter has a length of 14 cm as the eighth-order BPF, but the conventional waveguide is 20 cm as the seventh-order BPF for the same area of the cross section.

A Zeroth-Order Slot-Loaded Cap-Shaped Patch Antenna With Omnidirectional Radiation Characteristic for UHF RFID Tag Design

The zeroth-order resonance of a compact patch structure is explored for designing a metal-mountable tag antenna in the United States (US) ultrahigh-frequency (UHF) radio frequency identification (RFID) passband. This zeroth-order resonator (ZOR) structure comprises a cap-shaped patch loaded with two L-shaped slots. Also, the patch is coupled to the ground through two inductive stubs which provide enough parasitic reactance to support the zeroth-order resonance. The proposed single-element ZOR can generate sufficient antenna impedance for achieving a conjugate match with the RFID chip impedance. Good omnidirectional radiation characteristic with vertically polarized fields can be attained in the azimuth plane when the tag antenna is placed on a metallic surface. The proposed tag antenna’s realized gain at 915 MHz is −1.382 dB [effective isotropic radiated power (EIRP) 4 W]. A stable read distance of ~15 m is obtainable with even spatial coverage in the entire azimuth plane. The resonance frequency of the proposed tag does not vary much with the object being tagged.

A Coplanar Waveguide-Fed Ultra-Wideband Antenna with Single-Band Notched Characteristic Using Epsilon-Negative Loading

There is a lot of research being done on ultra-wideband antennas with band-rejection characteristics; such antennas are used in applications such as the internet of things and indoor tracking and localization. This paper presents a single-layer, Coplanar Waveguide (CPW)-fed, epsilon negative (ENG)-loaded UWB monopole with a single band-rejection characteristic. The proposed antenna comprises two unit-cells that are designed and loaded into an S-shaped monopole strip antenna, which forms an open-end ENG-TL monopole antenna. A 10-dB return loss characteristic (3.1–12 GHz) is achieved by merging five resonances: the Zeroth-Order Resonance (ZOR), the First-Positive-Order Resonance (FPOR) of ENG- Transmission Line (TL), open-slot modes (λ/4, 3λ/4) and 5λ/4 mode of a shorted monopole. A single-band notch characteristic is achieved between 3.4 and 3.8 GHz by deploying two pairs of radiating structures (two opposite open slots and two opposite L-shaped radiating strips). Opposing currents are excited in each pair, and therefore the total radiated field is cancelled at 3.5 GHz notched band. The proposed antenna is printed on a 1.6 mm thick FR4, single-sided copper substrate of dimensions 16 × 20 mm2. The fabricated prototype is tested, and both simulated and measured results showed that the proposed antenna represents a worthy state-of-the-art UWB antenna.

A Low-Profile and Compact Multi-Functional ENG-TL Inspired Antenna with Hybrid Polarizations for LTE/UMTS, WiMAX, and WLAN Applications

A novel low-profile, compact tri-band linearly and dual-sense circularly polarized (CP) antenna realized using via-less epsilon negative transmission line (ENG-TL) is investigated in this paper. The antenna miniaturization has been achieved by the zeroth-order resonance (ZOR) property of ENG-TL, which is actuated by connecting closed-loop octagonal ring radiator to an elliptical stub through a meandered-line structure. Circular polarization is accomplished by etching an L-shaped slot in the partial ground plane. The measured S11 result demonstrates that the proposed antenna features triple-band characteristics spanning from 2.42 to 2.50 GHz, 3.29 to 3.59 GHz and 5.43 to 5.55 GHz with centre frequencies of 2.46, 3.44, and 5.49 GHz, respectively. The antenna is offering linear polarization (LP) in the first and third bands while radiates left-handed CP in the + Z direction in the second band. An exceptional axial ratio (AR) of 0.062 dB has been achieved at 3.49 GHz with 3 dB axial ratio bandwidth (ARBW) extending from 3.35 to 3.67 GHz. This antenna offers an average simulated gain of 1.7 dBi across the CP band while 2.06, 1.75 and 3.67 dBi are acquired at 2.59, 3.53 and 5.62 GHz, respectively. Beside low-profile (0.013λ0 height) and miniaturized size (0.287λ0 × 0.205 λ0 ), intended antenna exhibits extended −10 dB impedance bandwidth, wide 3 dB AR bandwidth and reasonable radiation performance. It covers relevant frequency bands; therefore, it has the potential to be employed in 2.5 GHz LTE/UMTS, 3.5 GHz WiMAX, and 5.5 GHz WLAN applications.

Resonant absorption of light by a two-dimensional imperfect lattice of spherical particles.

The light absorption and scattering by an infinite two-dimensional array with an imperfect lattice of identical spherical particles is considered based on the statistical approach to a description of electromagnetic wave interaction with particulate media. Absorption resonances due to the coherent component of scattered light (zeroth order of diffraction) and resonances arising from the excitation of a flux of incoherently scattered light (higher diffraction orders) propagating at grazing angles to the array plane are studied. The dependence of absorption on the degree of positional ordering of particles is considered. It is shown that with an increase in ordering, the spatial coherence of the light flux along the array plane increases and the absorption resonance becomes more pronounced. Data are presented for silver wavelength-sized particles for s- and p-polarized incident waves. It is shown that at small angles of incidence, the first diffraction order can arise at the wavelength of zeroth-order resonance. In this case, the contributions to absorption created by the coherent and incoherent components of scattered light are summed up. The value of the absorption coefficient can be close to 0.95. A comparison with data for a partially ordered array is carried out.

Design of an Out-Folded Patch Antenna With a Zeroth-Order Resonance for Non-Invasive Continuous Glucose Monitoring

This article proposes an out-folded patch antenna with a zeroth-order resonance (ZOR) that is robust to a high-dielectric condition of a human body for noninvasive continuous glucose monitoring (CGM). The proposed antenna has two faces of a tapered section and a rectangular patch separated by a gap, and those faces are connected through vias at two corners near the gap. Two identical antennas are fabricated on a flexible printed circuit board (FPCB), and the properties of ZOR are compared with those of the fundamental mode to demonstrate the feasibility. The ZOR of the proposed antenna exhibits a negligible frequency shift, and its quality factor is 2.9 times higher than the fundamental mode, when attached to the skin. The evaluation is further extended to a human experiment using the two antennas for real-time estimation of coupling strength according to the change in glucose concentration. The trend of measured coupling strength well describes that of the glucose concentration obtained from a glucose meter with a mean absolute relative difference of 12.23%. The results demonstrate that the proposed concept has a great potential to improve the accuracy of noninvasive estimation in microwave spectrum.

A Sensitivity-Enhanced Sensor Based on Zeroth-Order Resonance for Liquid Characterization

A high-sensitivity planar microfluidic sensor is proposed in this paper based on composite left/right-handed transmission line (CRLH TL). By employing the series zeroth-order resonance (ZOR), the resonance of proposed sensor is only determined by surface capacitance and inductance. The short-circuit structure reduces the energy loss due to edge radiation and generates a highly concentrated electric field on the top surface of the substrate, which can be used to detect the dielectric loading samples. The presented sensor has been simulated, fabricated and tested. The sensor on the printed circuit board (PCB) is integrated with the fluidic container made of polydimethylsiloxane (PDMS) to form the test device. The water-ethanol binary mixture and sucrose solution are used to proof the concept. Finally, the prediction model for the water-ethanol mixture based on measured parameters has been established and the analysis of prediction error has been carried out. The sensor works around 4 GHz, and the maximum sensitivity reaches 1.04. Due to the high sensitivity and simple structure, the proposed structure is a competitive candidate for the applications including bio-sensing and portable biomedical device.

Improved SCRLH ZOR‐based compact microstrip bandpass filter with wide upper stopband

AbstractA novel compact microstrip bandpass filter (BPF) based on an improved simplified composite right‐/left‐handed (SCRLH) zeroth‐order resonator (ZOR) is presented in this paper. The improved SCRLH ZOR (ISZOR) can substantially simplify the filter configuration and shrink the filter size as well as ensure a wide upper stopband. A certain orientation of two ISZORs allows a larger gap to produce the specified interstage capacitive coupling, easing the requirement for fabrication precision. Starting from the purely lumped circuit model, the microstrip ISZOR is efficiently generated by utilizing the implicit space mapping technique, with which the microstrip BPF is then constructed and optimized by the Nelder–Mead simplex algorithm. A three‐pole filter with a center frequency of 3.1 GHz and a relative bandwidth of 5% is exemplified to illustrate the design process. The measurement shows that the filter is of good bandpass selectivity, with a transversal size reduction of more than 64% compared to a former counterpart and a rejection level better than 30 dB up to 11.76 GHz (close to 4f0).

Pattern Reconfigurable, Low-Profile, Vertically Polarized, ZOR-Metasurface Antenna for 5G Application

A novel miniaturized, aperture-shared, vertically polarized (VP), zeroth-order resonance (ZOR)-based, metasurface antenna with pattern reconfigurability is proposed for sub-6 GHz fifth-generation (5G) application in this article. By exploring an aperture-shared ZOR metasurface with only four p-i-n diodes, the proposed pattern reconfigurable metasurface radiator can be operated at nine radiation states (one omnidirectional beam and eight scanning beams with 45° step). This novel reconfigurable ZOR metasurface is analyzed by equivalent circuit, array theory, and field distribution. To validate the proposed working principles and design guidelines, this VP metasurface-based pattern reconfigurable antenna with a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.05\lambda _{0}$ </tex-math></inline-formula> is fabricated and measured. It exhibits an 11.5% overlapped −10 dB impedance bandwidth (3.40–3.8 GHz, well covering B42/B43 LTE bands) and a 4.5 dBi peak gain in different radiation states. With the advantages of a miniaturized size (low profile), broadband, flexible pattern switching capacity, good radiation performance, and simple design, it is well poised for space-limited sub-6 GHz microcell applications.

Microwave sensor for liquid mixture identification based on composite right left hand ‐ zero‐order resonator for sensitivity improvement

This work aims to present an improved version of the liquid mixture identification sensor, the proposed sensor is tested experimentally on mixture of water ethanol, the identification of liquid is based on the measurement of frequency displacement, and comparison with reference values of water ethanol. This device is based on metamaterial structure which is a composite right left hand (CRLH) resonator with zero-order resonator (ZOR). The CRLH in addition to its property of miniaturization effect, when combined with ZOR, the resonant frequency of various volume fraction are extended, which make the sensitivity higher. The high sensitivity of the sensor is obtained by an optimum choice of the CRLH components. The geometrical size of the sensor is 20 mm by 11 mm. It was printed on a RT/Duroid 5880 substrate with a very short testing surface area of 4 mm by 8 mm, the liquid is placed on the top side of the sensor, exactly on the CRLH structure. Three prototypes of sensors operating from 1 to 3 GHz are proposed, designed and simulated using the commercial software high-frequency structural simulator (HFSS). The main advantages of this work is first miaturization effect, second high sensitivity and finally a wide range of liquid can be tested with this sensor. To prove the working principle, ethanol with different volume fractions was adopted as a liquid under test, the obtained results present very good agreement with the literature and suggested that it is a miniaturized and high sensitive candidate (better than 1.38%) for liquid mixture identification.

An asymmetric CPW-fed ultra miniaturized epsilon negative triple-band antenna with improved gain using complimentary closed ring resonators

In this paper, an ultra-miniaturized triple-band antenna based on an epsilon negative transmission line (ENG-TL) approach is presented. The proposed antenna has a miniaturized electrical size of 0.247λ0×0.185λ0×0.019λ0 at 3.71 GHz which has been achieved by means of zeroth-order resonance (ZOR). This is recognized as an attractive technique to achieve compactness. It is observed from measured results that the proposed antenna is performing well over 3.63–3.81, 5.21–5.33, and 6.79–7.09 GHz. The novelty of this work lies in the fact that the peak gain has been improved by 1.73 dBi at the lowest order resonant mode. The antenna is able to exhibit measured peak gain of 1.97, 1.09, and 3.42 dBi in the broadside direction at 3.72, 5.27, and 6.92 GHz, respectively. Hence proposed antenna is suitable to work for Wi-MAX 3.5 GHz (3.4–3.8 GHz), WLAN/Wi-Fi 5.2 GHz (5.15–5.35 GHz), mobile/satellite (E-S) (6.875–7.075 GHz) applications.

Selective Microwave Zeroth-Order Resonator Sensor Aided by Machine Learning.

Microwave sensors are principally sensitive to effective permittivity, and hence not selective to a specific material under test (MUT). In this work, a highly compact microwave planar sensor based on zeroth-order resonance is designed to operate at three distant frequencies of 3.5, 4.3, and 5 GHz, with the size of only per resonator. This resonator is deployed to characterize liquid mixtures with one desired MUT (here water) combined with an interfering material (e.g., methanol, ethanol, or acetone) with various concentrations (0%:10%:100%). To achieve a sensor with selectivity to water, a convolutional neural network (CNN) is used to recognize different concentrations of water regardless of the host medium. To obtain a high accuracy of this classification, Style-GAN is utilized to generate a reliable sensor response for concentrations between water and the host medium (methanol, ethanol, and acetone). A high accuracy of 90.7% is achieved using CNN for selectively discriminating water concentrations.

Self-Oscillating Circularly Polarized Active Integrated Antenna Using Zeroth-Order Resonators With Boosted Conversion Efficiency

A new self-oscillating circularly polarized active integrated antenna (CPAIA) featuring boosted dc-to-RF conversion efficiency is proposed and demonstrated in this letter. The conversion efficiency, 40% better than the second best design in the literature, is achieved by innovative integration of a CP exciter with a pair of anti-symmetrically arranged parasitic radiators. The CP exciter is a linearly polarized self-oscillating active dipole antenna consisting of zeroth-order resonators and a crosscoupled pair oscillator. In addition to oscillate and radiate a linearly polarized electrical field into space, it is responsible for coupling half of the oscillating power into the pair of parasitic radiators to excite another linearly polarized electric field spatially and temporally orthogonal to the original one for CP operation. The proposed CPAIA is fabricated and tested at 879 MHz, and is compared with the state-of-the-arts in the literature. Good agreement between the simulated and measured results validates the design concept, and the performance summary table highlights the advantages of the proposed design.