Search

A high-scanning rate leaky-wave antenna (LWA) working at Ka-band with continuous backward-to-forward beam-scanning capability, good open stopband (OSB) suppression and wide scanning angle is exhibited. The proposed LWA is made by etching an array of cascaded high-Q resonators and open discontinuities on the substrate integrated waveguide (SIW). The resonator is designed by combining two symmetrically unbalance split ring resonators (USRRs) on the top surface of the SIW. The LWA's working mechanics were thoroughly investigated through band structure theory. An in-depth interpretation of the LWA's characteristics is provided by studying the surface current distribution and the equivalent circuit model of the resonator structure. The LWA's OSB is effectively alleviated by properly selecting the length of the radiation slot. Yet, the antenna scanning rate is directly improved by the oscillation quality of the resonators (i.e., USRRs), which is realized by tuning the split gap of the USRR. In the experiments, a prototype of the proposed LWA was fabricated and measured. The simulated and measured data show good agreement in terms of the antenna's scanning range and radiation gain. The measured results indicates that a continuous beam scanning from −56° to +48° is rendered over the frequency band from 32 to 36 GHz, which implies a spectral scanning rate of 8.84° per percentage. Finally, it is shown that the average gain can reach up to 9.1 dBi. [ABSTRACT FROM AUTHOR]

A novel cascaded dispersive delay structure based on a periodic glide symmetric stub-loaded microstrip transmission line is presented. Two group delay peaks are superposed to realize a group delay response that illustrates linear characteristics versus frequency. Two examples with slopes 0.83 and 2 ns/GHz, respectively, are proposed. Verified by experiments, the simulated and measured group delays show a well agreement. [ABSTRACT FROM AUTHOR]

In this article, we propose a traveling-wave endfire antenna based on the first higher-order transmission line (TL) mode, and it features wide bandwidth, high gain, and large aperture efficiency. We propose two essential conditions for the realization of the proposed wideband endfire antenna. First, the dispersion curve of the first higher-order mode should be made close to that of the air line across a wide frequency band. Second, the fundamental mode should be suppressed to allow single higher-order mode operation across a wide frequency band. Following these principles, we provide a design for an endfire antenna based on a periodically slotted parallel stripline, where the periodic meandered slots suppress the fundamental mode and hence allow single higher-order mode radiation. To verify the proposed approach, a prototype has been designed and fabricated. The antenna can achieve endfire radiation within a 1:2 frequency band (8.5–17.5 GHz), with an average gain of 10.7 dBi, and large aperture efficiency up to 6.38 dBi/ $\lambda ^{2}_{0}$. [ABSTRACT FROM AUTHOR]

A full-space scanning leaky-wave antenna featuring small aperture size and relatively stable gain is proposed in this communication. We propose three key conditions for full-space scanning capability, including single-harmonic radiation, field cancellation suppression at endfire, and open stopband suppression at broadside. Results from a prototype based on paired stubs and crossover offset parallel striplines are provided to verify the proposed principle. Experimental results show that the main beam is able to continuously scan from backfire to endfire with stable gain around 9.1 dBi within the frequency range of 4.5–10.2 GHz. The antenna aperture is $6.85\lambda _{0}\times 0.1\lambda _{0}$ only. [ABSTRACT FROM AUTHOR]

This letter presents a novel narrow-band bandpass spoof surface plasmon polarition (SSPP) filter, which has a controllable passband, good rejection, and a compact structure. It is composed of two end-extending SSPP transmission lines and a pair of L-shaped coupling branches. Both the bandwidth and the central frequency can be adjusted by changing the depth of the SSPP unit and the length of SSPP transmission line behind the coupling branches. The dispersion curves of the SSPP unit are analyzed, and the influences of some structural parameters are investigated. A SSPP band-pass filter is fabricated and measured based on the proposed method, showing a wide 3-dB fractional bandwidth of 11.2% centered at 6.25 GHz and an out-of-band rejection below −15 dB within 1–10 GHz. The measured result shows good agreement with the simulated one. [ABSTRACT FROM AUTHOR]

A planar periodic leaky-wave antenna (PLWA) with continuous backward-to-forward beam-scanning capability and consistent gain is presented. The PLWA is made of a new type of periodically arranging meander line structures, in which the capacitive coupling between neighboring units plays the key role in achieving a high scanning rate. In detail, the beam-scanning rate of the proposed PLWA is efficiently tuned by varying the gap between two adjacent units, without considerably changing the working frequency band. To mitigate the open stopband (OSB) and to improve the impedance matching, several inductive open stubs are introduced into a single meander line unit cell to enhance the radiation. In the experiment, a prototype of the proposed PLWA was fabricated and measured. The simulated and measured beams show good agreement in terms of scanning range and radiation performance. A continuous beam scanning from −60° to +58° through broadside in the frequency band of 5.95–7.1 GHz is observed, and hence, a 102.6°/GHz scanning rate is realized in practice. Besides, the PLWA shows an average gain level of 11.96 dBi with a variation lower than 2 dB and a sidelobe below −10 dB at all the measured frequencies. The proposed PLWA may have potential applications in radar, microwave imaging, and wireless communication due to its compact structure, easy to fabricate, and dispersionless performance. [ABSTRACT FROM AUTHOR]

In this article, two configurations of novel dual-band half-mode substrate integrated waveguide (HMSIW) leaky-wave antennas are presented. The first proposed antenna radiates linearly polarized (LP) waves in the lower band and circularly polarized waves in the upper band when the unit cells are cascaded sequentially. The second antenna, where the sidewall via of the HMSIW unit cells is connected alternatingly, provides simultaneous dual beams with different polarization in the upper operational band in addition to the LP beam in the lower operational band. The unit cells of the two antennas are analyzed in terms of their dispersion behaviors. Finally, the performance of both the antennas is experimentally verified. [ABSTRACT FROM AUTHOR]

We systematically analyze and describe a new type of traveling-wave endfire antenna based on an asymmetrically corrugated Goubau line that exhibits high efficiency and has a low profile. By proving that asymmetry is a necessary condition in addition to the Hanson–Woodyard condition for traveling-wave endfire radiation, we study the effect of asymmetric corrugation on the mode guide and coupling. We subsequently show that two different waves are independently guided along the two corrugated edges, whose phase difference leads to a transversally polarized dipole moment radiating in the endfire direction. A closed-form expression for the radiation pattern is derived based on the proposed analysis to approximately predict the antennas’ optimum length. To verify the proposed analysis and design principles, results from an experimental prototype operating at 13–15 GHz are also provided. The experimental results show that the antenna design has an average gain of 9.9 dBi and an average efficiency of 82%. The agreement between the predicted results and the final optimized results validates the proposed analysis. [ABSTRACT FROM AUTHOR]

Spoof surface plasmon polariton (SSPP) features highly confined field confinement and subwavelength operational scale. However, at the low-frequency region, SSPP usually suffers from a poorly confined field, and a relatively large loss resulted from the mode conversion. Folded substrate integrated waveguide (FSIW) is a compact version of substrate integrated waveguide. However, FSIW suffers from a large guided wavelength and hence is not preferred for compact antennas. In this letter, we propose a combination of FSIW and SSPP, which has the benefits of both FSIW and SSPP. Compared with the pure SSPP, FSIW–SSPP significantly improves the field confinement and transmission loss at the low-frequency region due to the closed structure. At the same time, FSIW–SSPP reduces the guided wavelength by 67% due to the slow-wave feature of SSPP. A prototype of FSIW–SSPP was fabricated and measured. The simulated and measured results validate the expected performance. This new structure has potential applications in the antenna miniaturization. [ABSTRACT FROM AUTHOR]

Abstract: This article proposes model analysis of a microstrip leaky‐wave antenna for forward and backward scanning. Mode coupling and dual scan concept is introduced in this article with an inverted V‐section leaky‐wave antenna. The proposed design concept has been implemented on microstrip planar structure. An inverted V‐section has been therefore implemented which resulted in frequency scanning in forward and backward directions in the right‐hand (RH) region. The phenomenon has been observed within same frequency bandwidth of leaky‐wave region which is normally difficult to see in conventional leaky‐wave antennas. The article has also provided a circuit model analysis and design implementation explained by mode coupling theory. The proposed dual scanning leaky‐wave antenna (DSLWA) design is providing a wide impedance bandwidth in the Ku‐band and K‐band with high gain, reduced side lobe levels and high radiation efficiency. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel slow-wave half-mode substrate integrated waveguide (HMSIW) combined with spoof surface plasmon polariton (SPP) structure. In this design, subwavelength corrugated grooves are etched on the up metal layer of HMSIW to support an SPP mode. The dispersion and transmission characteristics of the proposed hybrid HMSIW-SPP structure are analyzed and compared with the classic HMSIW. To experimentally validate this design, a prototype is fabricated and measured. A slow-wave effect is clearly observed in the proposed hybrid transmission line, and its wavelength is reduced by over 50% without sacrificing its transmission performance. This structure features a simple architecture and excellent slow-wave effect. [ABSTRACT FROM AUTHOR]

In this paper, spoof surface plasmon polariton (SPP) is integrated in the closed substrate integrated waveguide (SIW) structure and a novel hybrid SIW-SPP guided-wave transmission line (TL) is proposed. In this design, the surface wave mode of SPP can be excited and transmitted inside the closed structure of SIW. The dispersion property of the proposed SIW-SPP hybrid structure indicates that it has both slow wave feature of SPP and fast-wave feature of SIW. With the low-pass feature of SSP and the high-pass feature of SIW, the proposed hybrid SIW-SPP TL becomes a bandpass filter (BPF) naturally. The concept of integrating SPP and SIW opens a new way to develop novel wideband BPFs. A broadband filter is fabricated to verify the theory and the measured passband is from 16.1 to 25.4 GHz with a relative bandwidth of 43.8%. The filter bandwidth can be easily controlled by tuning parameters, thus the proposed structure is attractive and useful for the design of various BPFs. [ABSTRACT FROM AUTHOR]

This letter proposes a new spoof surface plasmon transmission line (SSP-TL) using capacitor loading technique. This new SSP-TL features flexible and reconfigurable dispersion control and highly selective filtering performance without resorting to configuration change. Moreover, it requires much smaller linewidth than the conventional SSP-TL for achieving an extremely slow wave (or a highly confined field), which is quite useful for a compact system. To illustrate the design principle, several examples are designed within the frequency range of 2–8 GHz. Both numerical and experimental results are given in comparison with the conventional SSP-TL. It is demonstrated that the proposed technique provides a better performance in size reduction and dispersion reconfigurability. [ABSTRACT FROM PUBLISHER]

The concept of space mapping is applied, for the first time, to the design of microwave dispersive delay structures (DDSs). DDSs are components providing specified group delay versus frequency responses for real-time radio systems. The DDSs considered in this paper are formed by cascaded coupled C-sections. It is first shown that aggressive space mapping does not provide sufficient accuracy in the synthesis of DDSs. To address this issue, we propose a predistortion space mapping technique. Compared to aggressive space mapping, this technique provides enhanced accuracy, while compared to output space mapping, it provides greater implementation simplicity. Two full-wave and one experimental examples are provided to illustrate the proposed predistortion space mapping technique. [ABSTRACT FROM AUTHOR]

Today's exploding demand for faster, more reliable, and ubiquitous radio systems in communication, instrumentation, radar, and sensors poses unprecedented challenges in microwave and millimeter-wave engineering. Recently, the predominant trend has been to place an increasing emphasis on digital signal processing (DSP). However, while offering device compactness and processing flexibility, DSP suffers fundamental drawbacks, such as high-cost analog-digital conversion, high power consumption, and poor performance at high frequencies. [ABSTRACT FROM PUBLISHER]

This paper presents a rigorous and intuitive wave-interference explanation of group-delay dispersion in resonators. It considers both one-port and two-port lossless and lossy resonators under the complementary frequency-domain and time-domain perspectives. The reasons for the group-delay dispersive nature of a resonator and for the phenomenon of negative group delay (superluminality) in a lossy resonator are clearly explained in terms of the constructive and destructive interferences of multiply reflected pulses. [ABSTRACT FROM AUTHOR]

For the first time, a systematic synthesis method for cross-coupled dispersive delay structures (DDSs) with controlled magnitude for analog signal processing applications is proposed. In this method, the transfer function is synthesized using a polynomial expansion approach, which allows to separately control the magnitude and group-delay response of the DDS. The synthesized transfer function also features a reduced order—namely, half—compared to that of previously reported synthesis techniques for linear-phase filters. Once it has been constructed, the transfer function is transferred into coupling matrices that can be implemented in arbitrary cross-coupled-resonator technologies. Several design examples are provided for different prescribed group-delay responses. An experimental waveguide prototype is demonstrated. The agreement between the measured and prescribed responses illustrates the proposed synthesis method. [ABSTRACT FROM AUTHOR]

A novel dispersive delay structure (DDS) based on a composite right/left-handed (CRLH)–CRLH coupler is proposed and demonstrated by both full-wave and experimental results. The experimental prototypes are compact and shielded multilayer DDSs implemented in low-temperature co-fired ceramics technology. Compared to the conventional all-pass C-section DDS, the proposed CRLH C-section DDS exhibit a larger group-delay swing, which leads to higher resolution in analog signal processing applications, as a result of their higher coupling capability. Moreover, they feature a larger bandwidth and a smaller size. A generalized wave-interference analysis is presented to both rigorously derive the transfer functions and group-delay characteristics of C-section DDSs and provide deeper insight into their operating mechanisms in both their left- and right-handed regimes. [ABSTRACT FROM AUTHOR]

This paper presents a dimensional synthesis method for the design of symmetric wideband waveguide cross-coupled filters without resorting to global full-wave optimization. In this method, we propose two circuit models suitable for the synthesis of wideband cross-coupled filters. Besides, we propose a novel physical realization of the cross-coupled K-inverter in the waveguide filter. As a design example, an X-band four-pole waveguide cross-coupled filter has been designed and fabricated. The results show good equal-ripple performance in the passband and improved rejection performance beyond the passband. [ABSTRACT FROM AUTHOR]

We show that a continuously nonuniform coupled-line C-section phaser, as the limiting case of the step-discontinuous coupled-line multisection commensurate and non-commensurate phasers, provides enhanced bandwidth and diversity in real-time analog signal processing (R-ASP). The phenomenology of the component is explained in comparison with the step-discontinuous using multiple-reflection theory and a simple synthesis procedure is provided. The bandwidth enhancement results from the suppression of spurious group delay harmonics or quasi-harmonics, while the diversity enhancement results from the greater level of freedom provided by the continuous nature of the nonuniform profile of the phaser. These statements are supported by theoretical and experimental results. [ABSTRACT FROM PUBLISHER]