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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]

An extremely high scanning-rate beam-steering antenna based on coupled resonators is proposed in this communication. Coupling resonators in a controlled manner provides a sharp phase variation across a narrow frequency band, which contributes to the extremely high scanning rate. To steer the beam across broadside, alternating +90° and −90° impedance inverters are employed in the topology. Such a coupled-resonator array antenna is modeled and analyzed by coupling matrix technique, which was conventionally used in filter design. To illustrate the proposed technique, two examples with 50 and 100 MHz bandwidths are designed. Experimental validation is also provided for the 50 MHz bandwidth example, which demonstrates that the proposed antenna reaches a high relative scanning rate of $52.8^{\circ }/\%BW$ with efficiency of 75%. [ABSTRACT FROM AUTHOR]

This article presents a ${D}$ -band ${E}$ -plane 90° filtering coupler and a ${D}$ -band six-port junction (SPJ), both working at 150 GHz. The coupler is formed by ten resonators, having a fourth-order Chebyshev response. Two of the couplers were combined with a 90° 3-dB branch-line coupler to build the filtering SPJ with 20 resonators in total. Inheriting from the filtering coupler, the SPJ also has a fourth-order Chebyshev response. A coupling matrix (CM) consisting of both resonant and nonresonant nodes, based on the coupling topology, was constructed to predict the theoretical responses. Guided by this CM, the coupler and the SPJ were designed and modeled. In addition, two silicon-based absorber chips were designed and implemented as two matched loads in the filtering SPJ. The SPJ was optimized, fabricated, and tested. The center frequency of the SPJ is 150 GHz and the bandwidthis 4 GHz. Simulation shows 0.5–0.7-dB insertion loss at 150 GHz and a maximum 3° phase error in the working band. The measurement gives the same center frequency andbandwidth. The response shows 0.7–2.0-dB insertion loss at 150 GHz and a maximum 15° phase error in the working band. [ABSTRACT FROM AUTHOR]

A novel $E$ -plane filtering six-port junction (SPJ) based on waveguide is presented. Different from the traditional designs, the proposed SPJ is formed by two identical filtering 180° couplers and two waveguide couplers with 180° and 90° phase shifts. A coupling-matrix (CM) technique, combining both resonant and nonresonant structures, has been developed to represent the entire SPJ. This has been used to predict the theoretical response as well as to investigate the effect of the couplers on the performance of the SPJ. A demonstrator has been designed to work at 10 GHz with a bandwidth of 0.4 GHz. Stub-loaded waveguide resonators have been used to keep a consistent profile and ease the layout of the complicated waveguide network. A good agreement between the CM-based theoretical responses, simulations, and measurement has been achieved. The measured average insertion loss is 0.4 dB, and the maximum in-band phase error is 10°. The measured in-band isolation between two input ports is higher than 26 dB. [ABSTRACT FROM AUTHOR]

This letter presents a ring-shaped E-plane filtering coupler working at 150 GHz with high performance. The coupler is based on cavity resonators. Unlike the conventional ones, the four resonators in this coupler are all bent along their length direction and connected end to end, forming a closed circle. By adjusting the radius of the circle, three of the resonators work on TE101 mode while the other is on TE102 mode. The coupler can be split through E-plane and the measured response of the coupler has an excellent agreement with the simulation, with a low amplitude imbalance of 0.31 dB, insertion loss of 0.12–0.46 dB, and over 20-dB return loss and isolation. [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]

This article presents a 2-D near-field sensing technique using single-port (reflection-type) coupled-resonator probe arrays. It utilizes the frequency diversity exhibited by a single-port output signal to identify the perturbation information from multiple spatially isolated probes. This approach features a faster speed and simpler architecture in comparison with conventional sensing techniques based on mechanical scanning or electronic switching. The single-port topology is employed instead of the two-port topology to simplify the system architecture. An extraction technique based on a one-port coupling matrix is proposed in this work to enhance the information extraction efficiency. The proposed technique is illustrated by an experimental example implemented using substrate integrated waveguide (SIW) and complementary split-ring (CSR) slot structures. The good agreement between the reconstructed image and the real image is used to validate the proposed technique. [ABSTRACT FROM AUTHOR]

A scalable multiple-probe near-field sensing technique using coupled resonators is presented. The technique captures perturbation information about metal scatterers near each probe and exactly distinguishes the contribution of each probe to the variations of the scattering parameters. The multiple-probe structure can be utilized to save scanning time compared with single-probe designs. A systematic extraction approach based on a coupling matrix theory and a vector fitting algorithm is employed. A design principle that provides stable structures utilizing the concept of condition number is also presented so that better calculation stability can be achieved under noisy conditions. The proposed technique is illustrated by an inline three-probe implementation with three numerical examples and two experimental validations, in which both single and multiple metal scatterers are used. The agreement between the predicted results and the extraction results validates the proposed technique. [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]

A stopband-extended sixth-order balanced bandpass filter with switchable passband function and stopband response is proposed in this paper. Based on the use of asymmetric coupled stepped-impedance resonators, the upper differential-mode stopband can be extended, and high common-mode suppression can be performed within passband. By means of high-order structure and cross coupling, which introduce transmission zeros closely around the passband, high selectivity is attained. The configuration utilizing switchable cross coupling is eventually employed in the balanced filter to perform either Elliptic function with steep passband edge or Chebyshev function with flat and deep stopband. The circuit is fabricated in high-temperature superconducting technique on an MgO substrate with YBCO thin films, which can result in relatively low insertion losses. Experiment at the temperature of 77 K was carried out to validate the design concept. The results attain good agreement with the predicted ones in simulation. [ABSTRACT FROM AUTHOR]

A coupling matrix technique is presented for the synthesis of nonreciprocal lossless two-port networks. This technique introduces complex inverters to build the nonreciprocal transversal network corresponding to the nonreciprocal coupling matrix. It subsequently transforms this matrix into canonical topologies through complex similarity transformations. The complex inverters in the final topology are transformed into real inverters and gyrators for implementation simplicity. A second-order network example and a fourth-order network example, as well as an experimental validation, are then provided to illustrate the proposed technique. Finally, other possible implementations of the nonreciprocal gyrators are discussed. [ABSTRACT FROM PUBLISHER]

Generalized coupled-line all-pass phasers, based on cascaded C-sections (CCSs), cascaded coupled-lines (CCLs), and hybrid-cascaded (HC) coupled transmission-line sections, are presented and demonstrated using analytical, full-wave, and experimental results. It is shown that for N commensurate coupled-line sections, CCL and HC phasers exhibit N group-delay peaks per coupled-line section harmonic frequency band, in contrast to the CCS configuration, which exhibits only one peak within this band. It is also shown that for a given maximum achievable coupling-coefficient, the HC configuration provides the largest group-delay swing. A wave-interference analysis is finally applied to the various coupled-line phasers, explaining their unique group-delay characteristics based on physical wave-propagation mechanisms. [ABSTRACT FROM PUBLISHER]

This letter presents a new design of microwave differentiators using coupled-resonator network. It is synthesized using coupling matrix techniques in the low-pass domain and subsequently transformed and implemented in the bandpass domain. Two numerical examples and one experimental validation are provided to illustrate the approach, which finally validates the proposed approach. [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]

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]

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]

A compact reflection-type phaser composed of quarter-wavelength transmission line resonators interconnected by alternating K- and J-inverters is proposed. A design method is also presented. To validate this method, a fourth-order example is designed and fabricated. The proposed phaser is shown to exhibit the benefits of smaller size, easier fabrication and suppressed even-order harmonics compared with previously reported half-wavelength phasers. [ABSTRACT FROM PUBLISHER]

An alternative method is proposed for constructing the coupling matrix of a filter having a transfer function with non-paraconjugate transmission zeros. The conversion formulas from the scattering matrix to the admittance matrix are derived under the only conditions of passiveness, losslessness and reciprocity. The main benefit of this method is that it allows, for the first time, to design all-pass filters using the coupling matrix technique. [ABSTRACT FROM PUBLISHER]