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Due to the power capacity limitation of the rotary joint, mechanical scanning radars are limited to use high-power microwave sources to improve their performance furthermore. To solve this problem, an over-mode circular waveguide rotary joint with radial mutations at the rotation point is introduced in this letter. The structure of the radial mutation is optimized to suppress unwanted modes. By connecting the choke slot and the rotating part, the breakdown risks of the rotary joint can be reduced. In addition, the choke structure is connected to the inner wall of the waveguide with a gap, even the breakdown occurs in the choke, the normal modes inside the waveguide will not be affected. To verify the design, a prototype of the rotary joint is fabricated and measured with the operating band in the range of 9.5–10.5 GHz and a power capacity of 3 GW.

In this paper, decoupling of a compact isosceles triangular array is performed by a hybrid method consisting of loaded parasitic element (LPE) in combination with decoupling and matching network (DMN). By introducing a reactively loaded parasitic element at a suitable position on the axis of symmetry of the isosceles triangle, not only are the mutual couplings between the element at the vertex and the two elements on the base eliminated but also the circuit parameters of the base elements are well prepared for a DMN of a simpler form. Thus, the impedance matching of the vertex element and the decoupling and matching of the base elements can be implemented independently. The DMN of base elements comprises two impedance-transforming sections (ITS) and a $\pi $ -shaped neutralization section (NS). The ITSs inserted between the antennas and NS convert the self-conductance to the system admittance and the trans-conductance to zero. The trans-susceptance is then compensated through the main line of the NS independently, and self-susceptance is canceled out by adjusting the tapped stubs subsequently. With all the explicit formulas derived, the design is systematic and straightforward. The presented compact isosceles triangular array with element separations of $0.1\lambda $ and $0.2\lambda $ is fabricated and measured. The results show that sound isolation of 35 dB and return loss of 21 dB is obtained with ECCs less than 0.02, validating the effectiveness of the hybrid decoupling technique.

In this article, a dielectric resonator (DR) excited wideband metasurface (MTS) antenna with differential feeding is proposed, which uses two modes of the MTS and the fundamental mode of the DR to achieve multimode operation and obtain wide bandwidth. Initially, based on the characteristic mode theory, relevant modes of the MTS are analyzed. Then, a DR operating at the fundamental mode (TEδ11x) is introduced as the magnetic current source to feed the MTS, exciting the dominant mode and high order mode (HOM) of the MTS simultaneously. However, this HOM has a weak gain at the broadside direction and large side lobes. According to the superposition principle of radiation patterns, the maximum at the broadside generated by the DR is utilized to enhance the boresight gain of the HOM, thus transforming the top-weak radiation pattern of this HOM into a broadside one and improving the gain flatness. Additionally, the differential feeding technique is introduced to improve the asymmetry of radiation pattern. Furthermore, by analyzing the out-of-phase currents and the periodicity of the MTS patches, three measures -loading transverse open-ended slots, shortening periodicity and loading longitudinal slots- are introduced to reduce the high side lobe level of the HOM while preserving radiation patterns undistorted and improving the gain stability. As a result, this HOM and the dominant mode of the MTS are combined with the fundamental mode of the DR, achieving multimode operation. Finally, the proposed antenna was fabricated and measured. The measured results agree well with the simulated ones, indicating an impedance bandwidth of 51.4% (4.38-7.41 GHz), a 5-9 dBi in-band gain and a 15 dB front-to-back ratio (FBR) within the operating band.

A filtering rectangle dielectric resonator antenna (DRA) with high band-edge selectivity is proposed in this paper. The DRA is fed by a simple hybrid feeding structure consisting of a microstripcoupled slot on the bottom and a thin metallic strip on the side of DRA to excite the fundamental TEy 1δ1 mode. The feeding structure establishes a cross-coupled mechanism which includes electric and magnetic coupling. This mechanism introduces two radiation nulls at the band edge without any filtering circuits. By using the designed hybrid feeding structure, a bandpass filtering response is obtained. For enhancing band-edge selectivity, a shorted stub is introduced to weaken the coupling between the two microstrip stubs of the feeding structure. A wide impedance bandwidth of 19% and a flat gain around 5.6 dBi are realized. To validate the proposed design, a prototype is fabricated and measured, showing a favorable agreement with the simulated results. [ABSTRACT FROM AUTHOR]

A compact wideband high gain directional antenna is proposed in this paper for marine communications. The antenna consists of a back plane (reflector), a slot-loop antenna (driven element), and a director of rod. Based on the current distribution, the slot-loop antenna is equivalent to an array of three linear current dipoles. The dipole acts as an element of the director, which provides a high efficient director for slot-loop antenna according to theoretical analysis. Both the impedance bandwidth and the 1 dB gain bandwidth are 45% covering 1.7–2.7 GHz in this design. A gain of 11.2 to 12.2 dBi is obtained in the working band with only one set of directors. The directors have a dimension less than the antenna aperture in the H-plane, which can be seen as one director in the end-fire direction. Compared with the classic Yagi antenna with the same gain level, the newly proposed antenna is only half of the size in radiation direction, which is a breakthrough for the Yagi antenna design. This size reduction can significantly minimize the interference between ship-borne antennas. The antenna is fabricated using only metal of low cost, which is useful for the ship-to-shore/ship communicating applications and desirable for the large-scale deployment. [ABSTRACT FROM AUTHOR]

A compact, wideband, omnidirectional, vertically polarised antenna without electrostatic discharge problems is proposed in this study for 4G long-term evolution applications. The proposed antenna is composed of three identical basic radiators separated by an angle of 120°. The basic radiator is based on a slot loop which is a wideband and DC ground structure. By bending the basic radiators, the antenna achieves better impedance matching and lower gain variation in the horizontal plane in a compact size. The proposed antenna reaches a fractional bandwidth of 45.5% for the voltage standing wave ratio (VSWR) <1.5, a peak gain from 2.4 to 3.8 dBi with a gain ripple around 2 dB in the omnidirectional plane. It operates from 1700 to 2700 MHz, covering most 4G long-term evolution frequency bands. Both simulation and measurement of a prototype is done in this study to verify the antenna performance. [ABSTRACT FROM AUTHOR]

A 3-dB branch-line hybrid coupler with wide stopband responses is presented in this letter. An equivalent K-inverter with bandpass function is used instead of one quarter-wavelength transmission line, which will realize size reduction and wide stopband characteristic of the coupler. Prototype of a branch-line hybrid coupler, which divides the power equally with 90± phase di®erence between the output ports, is also fabricated and tested. Both the simulation and measurement results show that such a hybrid coupler exhibits an 83.2% size reduction and has transmission suppression of ¡20 dB or less within five-fold bandwidth. [ABSTRACT FROM AUTHOR]

A low-profile dual-polarized omnidirectional antenna is presented. The antenna is a combination of a vertically-polarized (VP) antenna and a horizontally-polarized (HP) antenna. The VP antenna is composed of a circular ground plane, a cross-shaped metal patch with four shorted legs and a top-loading circular ring. The printed dipoles of the HP antenna are fed through a three-way power divider etched on an FR4 substrate. To maintain stable radiation and reflection characteristics, the HP feed coaxial cable is soldered on one patch of the VP antenna to reduce the parasitic current on the feed cable. The VP antenna covers the frequency bands for GSM/2G/3G/4G LTE, and the HP antenna works in an overlapping frequency bands for 3G and 4G LTE communication systems with high isolation. The VP antenna achieves a wide bandwidth of 108% from 800MHz to 2700 MHz, and its gains are larger than 2 dBi in 800~960 MHz band and greater than 4 dBi in 1710~2700 MHz band, respectively. The HP antenna works in the frequency band from 1700 MHz to 2700 MHz, and its gains are greater than 3 dBi. The proposed dual-polarized antenna is simulated, fabricated and measured. Measured results are in good agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

A wideband omnidirectional antenna is presented in this letter. The proposed antenna consists of three radiators over a ground plane, a monopole composed of three patches fed by a coaxial line, a coupling patch with three shorting legs above the monopole to extend the lowest frequencies of operation, and a top-loading disk located on the top of the coupling patch for further decreasing the lowest frequencies of operation. An enhanced impedance bandwidth of 9.23:1 ranging from 650 MHz to 6 GHz with S11 -13.9 dB (for SWR ⩽ 1.5 ) is achieved. The antenna meets network operator's requirements for cellular bands and has good radiation efficiency in the WiFi bands. The proposed antenna can be widely used in indoor distributed antenna systems, such as 3G, 4G LTE, and WiFi (2.4 and 5.8 GHz) bands. The antenna is simulated by ANSYS HFSS and measured in a microwave anechoic chamber. The simulated and measured results show good agreement. [ABSTRACT FROM AUTHOR]