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A spoof surface plasmon polariton (SSPP) antenna with dual-band endfire gain and small frequency ratio (FR) is presented. It uses an asymmetric structure to support two independent surface waves with different nonlinear phase constants. Due to the different phases of the superposed $E$ -field at the terminal of the proposed structure, dual-band endfire gains and endfire radiation null are achieved. The odd- and even-mode feedings, providing additional phase differences, are also investigated. Three prototypes, with FRs of 1.06, 1.11, and 1.5, are designed, simulated, and measured, respectively. All results validate the mechanism and demonstrate that the FR of the proposed antenna can be achieved easily in the range of 1.06–1.5 by choosing different unit cells and feeding modes. Moreover, the measured endfire out-of-band gain suppression, over 17 dB, presents a good directional interference inhibition. This small-FR endfire antenna shows a broad prospect for band coverage and directional noise inhibition with very close operating frequencies. [ABSTRACT FROM AUTHOR]

A bidirectional scanning antenna (BSA) based on surface wave mode is proposed. The bidirectional scanning capacity is achieved by two back-to-back placed frequency scanning tapered slot antenna (FSTSA) elements. The corrugated slot array in inner edges enables the BSA to support two surface wave modes to propagate along the inner edges with different phase constants. Due to the dispersion characteristic of surface wave mode, the phase difference between two modes varies with frequencies, then frequency scanning is achieved at the endfire. Slot arrays are also etched on the outer edges to reduce current flowing. By separately configuring two back-to-back FSTSA elements, the BSA could form a rotationally symmetrical, mirror symmetrical, or asymmetrical bidirectional scanning pattern. Three prototypes with rotationally symmetrical, mirror symmetrical, and asymmetrical pattern are designed and fabricated to verify the principles. Since the scanning plane is parallel to antenna surface, the proposed BSA has a low cross section, which makes it suitable for wireless communication in tunnels and coal mines where good air ventilation is required. [ABSTRACT FROM AUTHOR]

An endfire frequency scanning tapered slot antenna (FSTSA) is proposed and investigated. The proposed FSTSA is a two-conductor structure with a gradient slots array etched only on one of two inner edges in the FSTAS. The asymmetrical inner edges enable the antenna to excite two modes with different phase constants simultaneously along the two inner edges. Due to dispersion characteristics of spoof surface plasmon polaritons (SSPPs), the phase difference between the EM waves along the two conductors changes versus frequencies, which enables the main lobe of the FSTSA to scan through the endfire direction. An analysis model is conceived to provide insights into the design, which accurately predicts main lobe directions and initial values of the proposed antenna. The proposed antenna is fabricated, and the measured results show that the main lobe of the antenna scans from −15° to 14° (endfire direction at 0°) from 6.60 to 7.70 GHz, with the scanning rate of 26.4°/GHz. This antenna could be suitable for radar, plane integrated communication system, and certain other beam-scanning applications. [ABSTRACT FROM AUTHOR]

A high-fidelity short-pulse monopulse antenna based on an extended Goubau line (EGL) is proposed, along with a novel time-domain analyzing and designing method. The monopulse antenna contains a simple feeding network and an EGL radiating structure, where the width of the single conductor is enlarged and a metal wall is constructed along the central line of the conductor. The antenna is actually a two-element array to form sum and difference patterns. Performances of the feeding structure and the EGL are almost independent of operating frequency, ensuring the antenna to transmit and receive short-pulse signals with high waveform fidelity. Angular information is obtained by analyzing the received pulses with the normalized Euclid distance (NED). The NED patterns are plotted to illustrate the angular information provided by the short-pulse monopulse operation. A null depth of 30 dB is obtained by the difference NED pattern for the short pulses with a spectrum from 4.2 to 11.8 GHz. The measured performance shows that the proposed short-pulse monopulse antenna has a promising prospect in directional detecting and tracking applications. [ABSTRACT FROM AUTHOR]

In this letter, an ultrawideband (UWB) antipodal tapered slot antenna with reflectionless notched band is proposed and investigated. The proposed antenna uses an integrated absorptive bandstop filter, consisting of two quarter-wavelength open-circuit stubs and a 50 Ω resistor, to form a reflectionless notched band. Consequently, the input energy at the notched frequency is absorbed by the resistor rather than reflected. An antenna prototype is designed and fabricated to validate the design. Both simulated and measured results present that the realized gain drops over 40 dB at 5.5 GHz, and the reflection coefficient is below –10 dB from 3.1 to 10.6 GHz. Besides, a low ringing level of –23.4 dB of the measured reception pulse shows a good time-domain performance. Therefore, the proposed antenna could be applied in UWB short-pulse system to inhibit the 5 GHz WLAN interference. [ABSTRACT FROM AUTHOR]

A compact decoupling structure, implemented by the postwall slotline (PWS)-based stepped impedance resonator (SIR), is proposed for enhancing the isolation between patch antennas. A pair of SIRs is placed between microstrip antennas to cut off the coupling path, which enhances the decoupling performance greatly at resonance frequency. Meanwhile, designed with a combination of conventional slotline and the PWS, the decoupling structure has a compact profile and, thus, is suitable for miniaturized element space. A two-element patch array is designed and fabricated to verify the decoupling effectiveness of the proposed structure, by providing simulated and measured results. Measured realized gain of the antenna with proposed structure is about 5.1 dBi. High isolation of 30.4 dB at 5.7 GHz is achieved, and the edge-to-edge distance is 0.059λ0 with the decoupling structure. Moreover, with the decrease of element distance, isolation improvement will be significantly enhanced. The compact size and isolation performance show the potential of the structure to be applied in antennas arrays including multi-input–multi-output systems and adaptive arrays. [ABSTRACT FROM AUTHOR]

This study presents a hybrid receiving array architecture that combines analog and digital beamforming to offer a solution for the phased-array feed and other multifunction receive-only applications. This architecture is capable of handling multiple beams forming simultaneous and precision beam steering. To further reduce the hardware counts of the online performance monitoring, a calibration method is proposed in which none of the transmitters or the dedicated distribution network are used. The hybrid architecture concept and built-in calibration are validated experimentally via a prototype. The system performance, including the statistical results of the baseband measurement, phase error, and radiation patterns under various array configurations, are illustrated. An effective phase tuning step of 0.1^\circ, as well as a steering resolution at the subdegree level, is achieved, and the measured aperture distribution is in good agreement with that derived from the proposed online calibration. [ABSTRACT FROM PUBLISHER]