As the explicit finite-difference time-domain (FDTD) method is restricted by the well-known Courant-Friedruchs-Lewy (CFL) stability condition and is inefficient for solving numerical tasks with fine structures, various implicit methods have been proposed to tackle the problem, while many of them adopt time-splitting schemes that generally need at least two sub-steps to finish update at a full time step, and the strategies used seem to be an unnatural habit of computation compared with the most widely-used one-step methods. The procedure of splitting time step also reduces computational efficiency and makes implementation of these algorithms complex. In the present paper, two novel one-step absolutely stable FDTD methods including one-step alternating-direction-implicit (ADI) and one-step locally-one-dimensional (LOD) methods are proposed. The two proposed methods are derived from the original ADI-FDTD method and LOD-FDTD method through some linear operations applied to the original methods and are algebraically equivalent to the original methods respectively, but they both avoid the appearance of intermediate fields and are one-step method just like the conventional FDTD method. Numerical experiments are carried out for validation of the two proposed methods, and from the numerical results it can be concluded that the proposed methods can solve equation correctly and are simpler than the original methods, and their computation efficiency is close to that of the existing one-step leapfrog ADI-FDTD method.
This paper discusses the design of a 6-m Cassegrain optics based multiband reflector antenna integrated with beam waveguide (BWG) optics, which consists of an ellipsoidal mirror and three plane mirrors. The presented antenna has been simulated, and 75.8% and 76.8% aperture efficiencies have been achieved at 0.225 THz and 0.338 THz, respectively. The initial design parameters of elements of BWG network are computed using fundamental Gaussian beam parameters. The simulated results of the antenna including aperture efficiency have been presented and discussed in detail. The antenna has been designed for the ground based THz telescope for radio astronomy.
This letter proposes a 2×2 surface-mount dipole antenna array based on via fence for 5G millimeter-wave applications. The dipole antenna element was first proposed, which has a compact size and low cost. Then the via fences are introduced to reduce coupling between adjacent elements and enhance isolation. In this way, compared with a 1×2 antenna array without the via fence, the isolation of a 1×2 antenna array with a via fence is improved by 12 dB at 26 GHz. The elements are extended into 2×2 arrays with and without the via fence, and their performance is evaluated by the evaluation board. The measurement results show that the -10-dB impedance bandwidth of the antenna array is 19% (24.7-29.9 GHz), and the peak gain is 9.5 dBi at 25 GHz. The proposed 2×2 array can be used in the N257 (26.5-29.5 GHz), N258 (24.25-27.5 GHz), and N261 (27.5-28.35 GHz) frequency bands. Low cost, small size, and high isolation characteristics make it one of the candidates for 5G millimeter-wave applications.
Substrate integrated E-plane waveguide (SIEW) was invented recently to design E-plane waveguide devices on printed circuit board, which cannot be achieved by using the conventional substrate integrated waveguide (SIW). This paper is the first time to present an E-plane displaced SIEW junctions bandpass filter. The proposed design is shorter than the recently published SIEW septa filter and has a smaller footprint than several other SIW filters. It is designed by mapping an equivalent E-plane waveguide filter to its SIEW implementation. A filter prototype is built and measured for validation.
A new design of broadband cavity-backed slot antenna (CBSA) based on substrate integrated waveguide (SIW) technology is presented in this paper. An entire proposed antenna is printed on a Rogers RT/Duroid 5870 substrate, which consists of the SIW cavity, bow-tie slot, microstrip line feed. The proper position and size of the bow-tie slot on top of the SIW cavity will generate the cavity modes, which can be merged to obtain the broadband response. Moreover, to understand the effects of the geometric dimensions of the broadband antenna on S11 are examined using parametric study. The final antenna configuration operates on a frequency band ranging from 9.25 GHz to 10.5 GHz with a fractional bandwidth of about 12.65% for the simulation part. The measured bandwidth for S11 is about 12.1% (9.3 GHz to 10.5 GHz). The proposed antenna has a good measured gain of 6 dBi and 6.6 dBi, at 9.55 GHz and 10.35 GHz, respectively. The gain, the reflection coefficient, and the radiation patterns of the fabricated antenna are measured and indicated a very good agreement with simulations.
This paper proposes a design method of vertically polarized VHF high-gain antenna, a four-element array form. Our design improves the overall gain of the antenna and reduces its loss. In our design, the conventional impedance conversion methods are abandoned. Instead, we directly use transmission lines for impedance match which greatly reduces the loss of the antenna in the frequency range of 150 MHz-300 MHz, ensuring that the antenna provides a higher gain, and its signal transmission efficiency is also improved.