The far field definition used by the IEEE comes from a narrow band formulation (time-harmonic fields). This paper looks at the far field definition from a broadband signal perspective. A time domain definition of far field in terms of the pulse dispersion for large, wideband phased arrays is presented. It is shown that far field in the time domain depends upon the instantaneous bandwidth of the signal.

A review of the recent advances in beam-scanning reflectarray antennas is presented in this paper. First, an overview of the two different methodologies for designing beam-scanning reflectarray antennas, namely aperture phase tuning and feed tuning techniques, is presented, and the advantages and limitations of both approaches are delineated. Next, recent developments in feed-tuned beam-scanning reflectarray antennas such as multifocal and partially illuminated apertures are reviewed and some numerical and experimental results are presented and compared. In comparison with other alternatives such as phase-tuned reflectarrays or phased array antennas, these passive beam-scanning reflectarrays are low cost and less complex, which makes them suitable choices for the new generation of high-gain beam-scanning antennas.

Since the early 1990's, printed reflectarrays antennas have emerged as the new generation of high-gain antennas, providing many advantageous features such as low-mass, low-profile, and low-cost over reflectors and printed arrays. Moreover, they are also quite suitable for applications requiring high-gain and beamscanning features. For the beam-scanning operation, one approach is to equip the reflectarray elements with a phase tuning mechanism. Another approach is to move the phase center of the feed antenna, which ultimately changes the phase on the reflectarray aperture, leading to a scanned beam. While each approach has its own advantages, the primary advantage of the later approach is the relatively low cost. The drawback however is that it suffers from poor collimating properties for scanned beams in conventional parabolic-phase reflectarrays.

A bandwidth improvement method in reflectarray antennas by using closely space elements, i.e., unit-cell sizes smaller than λ/2, has been investigated both numerically and experimentally in this paper. A new definition of phase error has been introduced to analyze the broadband mechanism of closely spaced phasing elements. Through full wave EM simulations, it is revealed that closely spaced elements achieve a smaller phase error over the band. Based on these theoretical studies two Ka-band reflectarrays were fabricated and their performance was measured across the frequency range of 30 to 34 GHz. It is demonstrated that the reflectarray designed with closely spaced elements achieves a notable improvement in gain bandwidth performance.

In the present paper the response of V transmission line to electromagnetic illumination has been obtained. Also in order to determine the VTL frequency operation band for both TE and TM modes a Gaussian pulse source has been applied to the structure. The VTL structure has received considerable attention in high frequency and microwave IC packaging. The purpose of this study is to determine high frequency design considerations in order to reduce the effects of electromagnetic interference (EMI) on the VTL structure and maintain the desired performance. It was observed that the effect of incident EM waves on the V lines performance is considerably lower than conventional microstrips, however the V lines are more sensitive to sources at close proximity. In addition, although the V lines show lower dispersion at higher frequencies, their frequency operation band is limited by a resonance like behavior which is directly related to the V groove dimensions. The full wave analysis is carried out using the Yee-cell based 2 Dimensional Finite Difference Time Domain method (2D-FDTD), while enforcing a very stable and efficient mesh truncation technique.

In this paper, a new analytical method called Staircase Approximation is presented for static analysis of structures with arbitrary shapes. As an example, this method has been used to obtain the potential distribution of V Transmission Line. The complex boundary of this structure is subdivided into an arbitrary number of uniform (or non-uniform) steps, and then 2-D Laplace's equation has been solved in each section. The Finite Element Method (FEM) is employed to achieve the best lengths of these steps. Finally, the results of the potential distributions of some layers in the V structure have been verified with an apt numerical method. Relative formulas are also described. Although, some approximations are used to convert the V-shape part to a multi step one, both results are in good agreement. The most important advantages of this method compared to its rivals are its simplicity and accuracy that comes from the ability to break down a complex structure into some simpler ones.

In this paper a new coupled transmission line is introduced which is a combination of the Circular Symmetric Multiconductor Microstrip Line (CSMSL) and the V-shaped microshield. As a result the crosstalk has been reduced greatly. A static analysis is performed using the Finite Difference method and the static parameters and coupling effects of this structure is compared with the CSMSL structure. Also the time domain response of this Multiconductor Transmission Line (MTL) is presented.