Meie Chen

RCS Reduction of Patch Array Antenna by Electromagnetic Band-Gap Structure

In this letter, electromagnetic band-gap (EBG) structure is used to reduce the radar cross section (RCS) of the patch array antenna. The proposition of this method is based on the high impedance characteristic of the mushroom-like EBG structure. The basic patch array antenna is designed with a central frequency of 5.0 GHz while replacing the substrate of the array with the mushroom-like EBG structure. The frequency band in which RCS of the patch array antenna reduced significantly can be adjusted by parameters of the EBG. The backward RCS of the patch array antenna with EBG can be reduced as much as 10 dB compared to that of the conventional array antenna, and the degradation of the antenna performance is not significant.

A Novel Microstrip Antenna With Composite Patch Structure for Reduction of In-Band RCS

A novel kind of composite patch antenna is proposed, in which the mushroom-like electromagnetic band-gap (EBG) structure is integrated onto the conventional patch. Due to the high impedance property of the EBG structure, the scattering fields from EBG structure and the rest of antenna can be out of phase and cancel each other. The composite patch antenna exhibits a natural low in-band radar cross section (RCS) property and keeps the compact planar size as the conventional patch antenna. When radiating, the composite patch as a whole acts as the radiating part of the antenna; while scattering, the composite patch antenna can significantly reduce the in-band RCS within the main scattering beam direction, and the maximum reduction can reach 8 dBsm when plane wave is impinging from normal direction.

A Novel Compact MIM CRLH Transmission Line and Its Application to Leaky-Wave Antenna

A novel kind of compact composite right/left-handed (CRLH) transmission line (TL) is proposed in this paper. The unit cell of this structure consists of a novel metal-insulator-metal (MIM) parallel plates and a meander line shorted to the ground. The left-handed (LH) series capacitance per-unit-area of the novel MIM capacitor can be four times as much as that of the existing MIM, and this property shows high capability of compactness. As an application example of this novel design, a leaky-wave antenna (LWA) is presented, which has the capability of continuous frequency scanning. Full-wave method is employed to simulate the structure, and the equivalent-circuit model is applied to achieve basic insight into the behavior of the structure. The experimental results are presented for validation of the proposed structures. This novel kind of MIM exhibits great potential for the minimization of microwave devices and antennas constructed by the CRLH structures.

A New Insight into the Radiation Mechanism of Fast and Slow Traveling Waves

In this paper, a new explanation on the radiation mechanisms of slow and fast traveling waves is presented. The effective radiation sections that give rise to the far-field radiation of the traveling-wave structure are found and studied for the cases of slow and fast waves, respectively. A composite right/left-handed transmission line that can support both of the slow and fast waves in left- and right-handed regions is employed as an example. Based on the uniform line-source assumption, an ideal model of traveling-wave current with the same dispersion behavior as that of the CRLH structure is proposed and used to demonstrate the radiations of slow and fast waves in physical sense. This new understanding of the radiation mechanism of traveling-wave structures is useful to the applications of traveling-wave antennas.

Far Field Computation of the Traveling Wave Structures and a New Approach for Suppressing the Sidelobe Levels

The effective radiation section (ERS) proposed for studying the radiation of traveling-wave structure is further studied in this communication. The formulas for computing the radiation pattern of traveling-wave structure using the newly defined ERSs is derived. The effect of the attenuation constant on the computation of radiation pattern is discussed. A new idea for reducing the sidelobe level (SLL) of the traveling-wave structure is proposed by suppressing the emissions from the corresponding ERSs. It is found that the ERSs are not always located at the ends of the traveling-wave structure, this is quite different from the conventional viewpoint concerning the fast-and slow-wave radiations, and the reason is explained in detail. A line-source model corresponding to a 70-cell composite right/left handed (CRLH) traveling-wave structure is employed in the analysis, and the results are verified by full-wave method.

Radiation Characteristic of the Leaky Circular Waveguide With Periodic Slots

Transmission loss of the leaky coaxial cable (LCX) is increasing with the operating frequency. In order to avoid the large transmission attenuation of LCX at higher frequency, the proposition of replacing the coaxial cable with circular waveguide to construct leaky waveguide is put forward in this letter. The spatial harmonics and their radiation conditions of the proposed dielectric-filled leaky circular waveguide are analyzed. The near field and the radiation patterns of the waveguide are simulated and analyzed, from which the cutoff frequency of the leaky waveguide is extracted. This kind of leaky circular waveguide is desired to generate uniform radio wave coverage and to replace the leaky coaxial cable in the applications where the wireless systems working at higher frequencies are used.

Radiation characteristics of rectangular leaky waveguide under high speed railway environments

The radiation characteristics of rectangular leaky waveguide with transverse slots cut in the broadside wall are studied, the effect of the high speed railway environment on the radiation property is analyzed. The equivalent magnetic current method and the method based on Loves field equivalent principle are used to simplify the calculation of radiation field of leaky waveguide. The results are in coherent agreement with those obtained by commercial software HFSS. The thickness of the waveguide has been taken into account.

New Approach of Radiation Pattern Control for Leaky-Wave Antennas Based on the Effective Radiation Sections

In this paper, a new radiation pattern-control approach for leaky-wave antenna designs is proposed based on the theory of effective radiation sections. This approach can be used to generate radiation null regions around desired direction or to reduce the side lobe levels of leaky-wave antennas in a simple and efficient way, i.e., by controlling the radiation from the effective radiation sections. The traveling-wave line-source model is employed for simplifying the analysis at first. Then, the approach is implemented in the sub strate integrated waveguide (SIW) long-straight slot Leaky-wave antennas (LWA) by changing the slot width at the locations corresponding to the effective radiation sections (ERSs). The simulation results show that the radiation null region can be introduced around the desired direction, and the side lobe level can be reduced. Furthermore, the cross-polar level can be controlled to a very low level. Experimental results are also given as verification. In addition, the proposed method still has some limitations, which are discussed in detail and will be improved in the future.

Analysis and Design of Leaky-Wave Antenna with Low SLL Based on Half-Mode SIW Structure

This paper presents a novel leaky-wave antenna based on the Half-Mode Substrate Integrated Waveguide (HMSIW) structure with low side lobe level. The effect of the structural parameters of the LWAs on the radiation performances is studied. Using beam-forming technique, the leakage loss factor α along the radiation aperture is designed in a tapered way by controlling the aperture depth along the structure. This controls the radiated power along the antenna aperture and finally achieves the radiation pattern with low SLL. Furthermore, the antenna structure is optimized to get an even lower SLL.

A New Kind of Circular Polarization Leaky-Wave Antenna Based on Substrate Integrated Waveguide

A new kind of circular polarization leaky-wave antenna with N-shaped slots cut in the upper side of substrate integrated waveguide (SIW) is investigated and presented. The radiation pattern and polarization axial ratio of the leaky-wave antenna are studied. The results show that the width of N-shaped slots has significant effect on the circular polarization property of the antenna. By properly choosing structural parameters, the SIW based leaky-wave antenna can realize circular polarization with excellent axial ratio in 8 GHz satellite band.