Millimeter waves, corresponding to the frequency range 30 to 300 GHz, have characteristics which make them ideal for many applications. Antennas at these frequencies have the advantage of reduced size and weight and can be fabricated as an integral part of the system they are used in. Millimeter wave microstrip antennas have been extensively researched over the past decade. The purposed of this report was to build and test 35 GHz microstrip antennas as well as put into operation a high voltage klystron power supply, Micro-Now Model 756. The antennas were fabricated and tested in the lab and the results obtained are reported. The operation of the Model 756 power supply is also outlined in detail.

This thesis discusses the theory and limitations of a system that has been designed and constructed for the purpose of measuring the phase shift and attenuation of high-frequency (15 MHZ) electromagnetic waves propagating between two insulated antennas that have been lowered down air-filled boreholes (cased with PVC pipe) at San Xavier Mine, Pima County, Arizona. Both the transmitting and receiving antennas are center-fed, sleeve dipoles that have been tuned to approximately their resonant lengths. The insulated-sleeve dipole antenna is modelled as the inner conductor of a radiating, coaxial transmission-line, which allows simple transmission-line formulas to be used in approximating the antenna impedance and current distribution along the antenna. Experimental results at the San Xavier Mine indicate the analogy is valid. Consequently, the most easily interpreted and repeatable measurements have been made with the antennas centered in the borehole.

International Telemetering Conference Proceedings / October 28-31, 1985 / Riviera Hotel, Las Vegas, Nevada / PSL is developing a telemetry antenna intended to avoid the mechanical complexity of traditional parabolic passive monopulse trackers. For a considerable range of reception scenarios, a stationary non-tracking antenna will fill the reception requirement while greatly simplyfing the antenna hardware as compared to mechanical passive trackers. A single, phi-symmetric, shaped-beam antenna provides proper coverage of the test range for multiple airborne targets. This system is not time shared and requires no acquisition time. Approximate azimuth to the target is displayed on a CRT. This paper examines the applicable test scenario and the resulting hardware.

No description available.

No description available.

Electromagnetic shielding by thin, perfectly conducting, two dimensional cylindrical shells over a lossy earth is investigated. The temporal frequency response of the exterior field due to a line source within the shell is computed for a shell described by a three sided, rectilinear structure whose opening faces the earth. The formulation allows shells of arbitrary cross-sectional shape to be analyzed. The earth is modeled as a homogeneous half-space with a planar boundary and frequency dependent electromagnetic properties. Two solution techniques are presented. In the first, the induced current is obtained through a numerical solution of the electric field integral equation (EFIE) at many discrete frequencies. It is found that the applicability of this formulation is limited since in the case of effective shielding, fields calculated from the EFIE are very sensitive to numerical errors. In the second technique the EFIE is again solved for the currents induced on the shell. The induced currents are used to calculate the electric field in the aperture which is used to solve a combined-source integral equation (CSIE) for the external fields. It is found that the CSIE does not suffer from the numerical ill-conditioning that plagues the EFIE, and is well behaved at all frequencies. Numerical results are presented which indicate that the shell-earth combination is very effective in shielding the internal source. Interior modes are weakly transmitted to the interior for the case of a purely dielectric earth. For a lossy half-space the resonances of the closed shell are enhanced. The related topic of scattering by perfectly conducting objects over a lossy earth is addressed. Numerical formulations for the solution of the integral equations are presented which deal with several troublesome aspects of the problem, including the incorporation of the correct edge singularities.

No description available.

No description available.

With the current scenario of development of antennas in the wireless communication field, the need of compact multiband, multifunctional and cost effective antenna is on the rise. The objective of this thesis is to present fixed and reconfigurable techniques and methods for small and slim multiband antennas, which are applicable to serve modern small and slime wireless, mobile and cognitive radio applications. In the fixed designs, independent control of the operating frequencies is investigated to enhance the antennas capabilities and to give the designer an additional level of freedom to design the antenna for other bands easily without altering the shape or the size of the antenna. In addition, for mobile phone antenna, the effect of user’s hand and mobile phone housing are studied to be with minimum effect. Although fixed multiband antennas can widely be used in many different systems or devices, they lack flexibility to accommodate new services compared with reconfigurable antennas. A reconfigurable antenna can be considered as one of the key advances for future wireless communication transceivers. The advantage of using a reconfigurable antenna is to operate in multiband where the total antenna volume can be reused and therefore the overall size can be reduced. Moreover, the future of cell phones and other personal mobile devices require compact multiband antennas and smart antennas with reconfigurable features. Two different types of frequency reconfigurability are investigated in this thesis: switchable and tunable. In the switchable reconfigurability, PIN diodes have been used so the antenna’s operating frequencies can hop between different services whereas varactor diode with variable capacitance allow the antenna’s operating frequencies to be fine-tuned over the operating bands. With this in mind, firstly, a switchable compact and slim antenna with two patch elements is presented for cognitive radio applications where the antenna is capable of operating in wideband and narrow bands depending on the states of the switches. In addition to this, a switchable design is proposed to switch between single, dual and tri bands applications (using a single varactor diode to act as a switch at lower capacitance values) with some fine tuning capabilities for the first and third bands when the capacitance of the diode is further increased. Secondly, the earlier designed fixed antennas are modified to be reconfigurable with fine-tuning so that they can be used for more applications in both wireless and mobile applications with the ability to control the bands simultaneously or independently over a wide range. Both analytical and numerical methods are used to implement a realistic and functional design. Parametric analyses using simulation tools are performed to study critical parameters that may affect the designs. Finally, the simulated designs are fabricated, and measured results are presented that validate the design approaches.

Fundamental TM11 mode of circular microstrip antennas has a limitation of low broadside gain. This thesis explores and investigates the possibility of designing high gain circular microstrip antennas by using higher zeros of the first order mode, or the TM1m modes. Deficiencies in the existing methods of gain enhancement, motivates the need to look for new methods. This is done by first investigating the radiation characteristics of TM1m modes, and then providing techniques for sidelobe suppression in their radiation patterns. Several approaches are proposed and corresponding to each developed technique, an example of high gain antenna is designed, fabricated and experimentally evaluated. First, through the radiation characteristics of a magnetic loop over an infinite ground plane, we explain the occurrence of high sidelobes in the E-plane radiation patterns of the TM1m modes. By noting the peak directivity and sidelobe variation with loop size, we propose, investigate and demonstrate the use of high permittivity substrates to reduce the sidelobes in the TM12 mode. Second, to remove the dependence of the radiation characteristics on high permittivity substrates, another technique to suppress the high sidelobes of TM12 mode, is presented. It is found that introducing a narrow nonresonant rectangular slot at the patch center, sidelobes of the TM12 mode can be effectively suppressed. Sidelobe level (SLL) suppression is demonstrated by both simulation and measurement, using various configurations. Third, it is proposed that linearly superimposing the radiation fields of either odd or even zeros of the first order mode, can achieve both high gain and low sidelobes. To show this, stacked antenna configurations of TM11 and TM13 modes are thoroughly investigated and SLL suppression is demonstrated. Finally, to leverage further advantage of the linear superposition of modes, a single layer annular slot loaded antenna configuration is proposed. The proposed new configurations are based on higher order TM1m modes, which, for excitation, requires electrically large conducting discs. This property offers one more advantage at high frequencies, where antenna size becomes too small for the fundamental mode to fabricate and feed. The proposed electrically large antennas eliminate these problems, and become more practical to fabricate. / February 2017