The antennas installed in mobile devices are small and low-profile compared to wavelength at the operating frequency. In general, low-profile horizontal elements and short monopole antennas have low ...radiation resistance. Low radiation resistance requires matching circuit between 50 Ω feed line and decreases radiation efficiency. By using the characteristic mode, excitation of the ground plane to improve the radiation resistance has been investigated. This paper proposes the structure with the modified folded dipole antenna, which is placed close to the metal casing. The surface current on the casing is excited by modified folded dipole antenna and contributes to the radiation.
Based on the analysis of the influence of the ground electrical parameters on the short wave signal transmission, this paper studies the influence of the transmission efficiency of the whip antenna ...of the short wave small power radio station on the ground wave transmission, puts forward the basic method of selecting the working frequency band of the small power short wave radio station in the short distance communication, and verifies the feasibility of the method through the experiment.
A low profile, single layer, light weight ultra-wide band (UWB) antenna is introduced in this work. The design method depends on a main (primary) printed patch capacitively coupled to secondary ...parasitic patches. The whole design dimensions are 35 × 39.4 × 0.5 mm. The main patch is fed with coplanar waveguide (CPW). The main patch is constructed as a perforated circle with four quarter-circle sector holes over a roger RO3003 substrate with real permittivity ε r = 3 and height h = 05m 0.5 mm. The parasitic elements are six equal small circles coupled to the primary patch through a gap. The whole antenna structure and the CPW feed line are printed on the same side of the substrate and the other side has no conductor (no ground plane). The antenna is fabricated and its parameters are measured experimentally. The reflection coefficient, radiation pattern and radiation efficiency are measured within the antenna operating band 2.9 -10.7 GHz. The measurements and the electromagnetic simulations are compared showing good agreement.
In the previous chapter it became clear that although the performance of CMOS technologies has increased over the past decade, the available gain at mm-wave frequencies is still limited. To maximize ...the performance of multistage differential amplifiers in which these transistors are integrated, accurate and low loss passive impedance matching structures are required. Chapter 4 will cover the detailed analysis of the concept of impedance matching and its impact on the performance of multistage differential amplifiers. In the first part of this chapter, the analysis and design of several passive matching circuits is discussed.
The radiation characteristics of 2-D circular uniform Fabry-Perot cavity (FPC) antennas are investigated, providing theoretical references for general 2-D FPC antenna design. Based on the radial ...leaky wave theory and the transverse equivalent network (TEN) model, the gain and the aperture efficiency of the circular FPC antenna are calculated. The optimum radiation efficiency that maximizes the broadside gain is found. The bandwidth is also discussed.
In the paper, a new ultra-wideband tightly coupled antenna array (TCA) is designed. The array unit is mainly based on the traditional Vivaldi antenna structure, to which trapezoidal slots are added ...and metal vias are used to extend the radiating arms, thus forming a flat plate coupling capacitor to reduce the overall profile height of the antenna. The wide foot matching layer is placed on top of the antenna, and T-slots are added on both sides of the Vivaldi opening to increase the resonance point and widen the bandwidth. This unit is formed into an array, and the array takes the form of a uniform planar array. Based on the above improved dielectric layer loading low-profile array can achieve VSWR<2.5 at 3~18GHz with 15mm profile height, and also can achieve high radiation efficiency, which is >85% in the full band.
A general transmission line model of a lossy inverted F antenna is derived in this work to allow the study of the radiation performances of the antenna regarding the miniaturization technique. The ...model allows to assess input impedance, radiation efficiency and currents at any point of the structure. It shows high accuracy with a maximum error of 1.1% compared to CST MWS simulations. This analytical Transmission Line model will allow to study and optimize tunable miniature IFA performance as function of the loading component characteristics.
The work is devoted to studying the process of radiation of electromagnetic field UWB pulses by broadband slot antennas. The dimensions and shape of the slot radiator were determined as a result of ...the computer simulation. An antenna driving circuits for the active and passive modes of excitation are developed. The radiator is shielded. The amplitude-time characteristics of the pulsed signals radiated by both active and passive shielded slot antennas were investigated experimentally. It is shown that the use of an active mode for excitation of the slot antenna can notable (by 2.7 times or 8.6 dB) increase the amplitude of the radiated signal in comparison with the passive mode of excitation.
A circularly polarized antenna with high radiation efficiency is proposed in this paper, which is based on multilayer PCB design and suitable for 28GHz millimeter wave band. The proposed antenna ...element is composed of four groups of monopole antennas that distributed in symmetrical structure. Each group of monopole antenna includes a feeding structure, a primary radiation sheet and a parasitic radiation sheet. The four groups of monopole antennas are successively fed with equal amplitude and 90° phase difference, then form circularly polarized antenna. Integrated with feed network and coaxial cable-like structure, the proposed antenna can cover the bandwidth of 26.5~29.5GHz with VSWR<1.2, AR<1.5dB and average radiation efficiency higher than 90%.