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A design approach of triband conformal monopolar antenna combining cavity mode and equivalent circuit (Ec) is proposed. First, based on mode analysis, two lower and closer resonant frequencies in the VHF-band are generated by introducing two slot rings and two circles of short vias to a circular parallel-plate structure. Second, its Ec is extracted and modified. Then, the geometry structure is improved accordingly. An inverted truncate cone is introduced to modify the characteristic impedance of the monolithic radial transmission line to obtain an available band in the middle frequency (UHF). Finally, a high-frequency (L) antenna is embedded into the truncate cone and excited by a novel composite feeding structure. Furthermore, the conformal performance of the triband antenna is investigated. The conformal antenna prototype is fabricated and achieves a triband within 69.3–72.5 MHz, 317–348 MHz, and 1.38–1.71 GHz with a size of $0.42\lambda _{0}\times 0.42\lambda _{0}\times 0.014\lambda _{0}$ (maximum wavelength). The realized gain in triband is −7.6 to −5.9, 4.7–5.4, and 4.7–5.9 dBi, respectively. For a 6 cm-thick FR-4 substrate combined with shorted metal columns, the triband conformal antenna has the potential on serving as a vehicle roof to bear the load, and it is attractive in vehicle communication too. [ABSTRACT FROM AUTHOR]

A novel low-profile phased antenna with dual-port and its two types of 1-D linear array to 2-D space wide-angle beam scanning are proposed. The antenna unit is composed of fishbone structure and rhombus parasitic patch, which is folded into n-shaped to low profile $0.08\lambda $. By adjusting the phase difference ($\Delta \varphi$) from 0° to 180°, the antenna working mode is changed from even mode to hybrid mode and to odd mode eventually. Therefore, the proposed antenna unit realizes wide-angle scanning characteristics and continuous switching state from broadside lobe to endfire lobe. Furthermore, the proposed phased antenna element is extended to two kinds of 1-D linear phased array (Array#1 and Array#2) based on the generalized principle of the pattern multiplication. The fabricated Array#1 can realize beam scanning range $- 116^{\circ }< \theta _{\mathrm {m}} < 0^{\circ }$ (xo z plane), $0^{\circ }< \theta _{\mathrm {m}} < 63^{\circ }$ (yo z plane), and $90^{\circ }< \Phi _{\mathrm {m}} < 169^{\circ }$ (xoy plane) and the fabricated Array#2 can achieve $0^{\circ }< \theta _{\mathrm {m}} < 60^{\circ }$ (xo z plane), $0^{\circ }< \theta _{\mathrm {m}} < 65^{\circ }$ ($\text{y}{o}\text{z}$ plane), and $90^{\circ }< \Phi _{\mathrm {m}} < 152^{\circ }$ (xoy plane). The proposed phased antenna unit and its 1-D array can realize 2-D space wide-angle scanning, improving scanning performance and expanding scanning dimensional space in phased array. [ABSTRACT FROM AUTHOR]

A novel dual-port phase antenna is proposed to realize 2-D scanning. The antenna consists of two monopoles on both sides and a fishbone structure in the middle. By changing the phase difference ${\Delta \varphi }$ between two monopoles, energy is coupled to the proposed structure, exciting different degrees of superposition of even and odd modes. The continuous switching from the broadside lobe to the end-fire lobe is realized, and it has the characteristic of 2-D scanning. Furthermore, to provide an in-depth insight into the 2-D scanning mechanism, two linear arrays (Array 2 and Array 3) based on the proposed antenna element and a generalized principle of pattern multiplication (GPPM) are developed. The fabricated Array 2 can offer scanning angles of 0°–73° along the $\theta $ -direction with the gain of 6.5–10.4 dBi and 90°–140° along the $\Phi $ -direction with the gain of 6.1–11.7 dBi. Its scanning coverage of 3 dB beamwidth is $0^{\circ } < \Phi < 140^{\circ }$ , $0^{\circ } < \theta < 90^{\circ }$. The manufactured Array 3 can scan 0°–90° along $\theta $ -direction with the gain of 8.2–11.1 dBi and 50°–90° along the $\Phi $ -direction with the gain of 6–9.36 dBi, and its 3 dB coverage of the main beam scanning is $0^{\circ } < \Phi < 180^{\circ }$ , $0^{\circ } < \theta < 90^{\circ }$. Consequently, the proposed antenna and GPPM can be readily extended to wide-angle scanning phased arrays. [ABSTRACT FROM AUTHOR]

An extremely low-frequency (ELF) magnetomechanical antenna with the size of one-millionth wavelength based on a three-phase induction motor is reported, whose working frequency is no longer limited by the resonant wavelength. The rotating three-phase induction motor with nonmagnetic material shell is just equivalent to a rotating magnetic dipole with 1.5 times magnetic dipole moment. It can transmit the modulated electromagnetic (EM) signal by modulating the rotating speed of the motor. A near-field ELF EM signal transmission experiment system is constructed based on the magnetomechanical antenna with $\Phi 10$ cm $\times50$ cm size, and the transmitted EM signals were received by a 200-turn coil, which is 10–200 m far away from the transmitter. The EM signal frequency is almost the same as the rotating speed of the motor, and it varies with the rotating speed too. With arbitrary waveform generator and variable-frequency drive (VFD) modulating the rotating speed of the motor, a near-field ELF transmitter with modulating EM signal is built, and the sawtooth wave (STW)-modulated EM signal was transmitted and received clearly during 10–200 m. The square wave (SW)-modulated EM signal was communicated too. The proposed magnetomechanical antenna has a compact size and is very suitable for ELF remote wireless communication. [ABSTRACT FROM AUTHOR]