A cylindrical microstrip array antenna with 5 pairs of coupled slotted strip framed patches is analyzed. The patches are proximity-fed by a cylindrical microstrip line. In order to extract the reflection coefficient from the standing wave pattern on the microstrip line, its length is about 5 wavelengths. To the best of the authors' knowledge proximity-fed cylindrical arrays have not been analyzed before using a rigorous MOM model that takes into account all electromagnetic couplings between patches and feeding line. The paper consists of three parts. The first part describes a plane wave excitation of the cylindrical microstrip structure. It introduces some innovating theoretical developments, like the improvement of the asymptote for the spectral Green's function and the explicit surface wave contribution. The second part calculates the radar cross section of the cylindrical microstrip structure with single and coupled slotted strip framed patches. The resonant frequencies, and the amplitude and phase of the current distribution are analysed. The third part describes a design for a proximity-fed array of 5 coupled slotted strip framed patches. It gives the reflection coefficient, current distribution on the patches, and radiation pattern. A very low level of cross polarization (< -40 dB) is achieved. It is shown that the resonant frequencies of the cylindrical array and its planar analogue lie very close to each other. This is due to the common nature of the low frequency slot resonance for the slotted strip framed patch.
In this paper, we built a free-space scattering-type scanning near-field millimeter wave microscope using two tapered dielectric probes facing each other and a sample in between based on MVNA. Nylon, Teflon and PVC dielectric tapered probes are compared in this system. We adopted a PVC probe and a Teflon probe as incident and receiving probes. The resolution is frequency dependent. In order to increase the resolution and contrast, we additionally positioned a metal probe tip between the dielectric tapered probe and the object under test. First experiment results on this signal improvement concept will be reported for a 2 mu m tungsten probe, yielding an increased field enhancement and leading to the contrast improvement.
Most MRI studies benefit from good homogeneity of the transmit magnetic field. We presented numerical investigation for a set of array/load configurations obtained by RF circuit and frequency domain 3-D EM co-simulation. This is a very powerful and fast method for array coil investigation, since one multi-port 3-D EM simulation, which can be calculated in a reasonable time, is sufficient for obtaining the array field homogeneity with any different tuning/feeding/decoupling conditions. We applied capacitor and inductor based decoupling networks and compared their array homogeneity obtained when the power reflected by the entire coil was minimized. The optimal separation between load and array giving best homogeneity without visible degradation of mean B-1+ over the center transverse slice is in the range of 30-45 mm. This result assists the design of transmit-only/receive-only (TORO) arrays, because about 40 mm separation provides adequate space for an RX-only coil.
In this paper, we present a generalized theoretical model for the angle of arrival (AOA) in wireless channels when the scattering is two-dimensional (2-D) anisotropic. This model can constitute a platform for creating new angular distributions for the propagating multipath power and as such, a new distribution accounting for multi-modal arrival will be presented. The latter will represent the case that multipath power arrives into four angular sectors being parametrically deflned with respect to the direction of the receiver motion. From the AOA, the power spectral density (PSD) of the received complex signal is analytically derived. Further generalization with multi-modal arrival into an arbitrary number of angular sectors can be treated similarly.
Among the next space missions goals the exploitation of the Moon, the natural Earth satellite, is gaining an increasing interest. Colonization of the Moon is along the usual track of human civilization and economic expansion; it is also related to a large number of scientiflc issues, including Earth Observation (EO). With respect to standard LEO satellite commonly used in remote sensing, Moon has speciflc features. In this work we analyze the potentials as well as the limitations related to active microwave remote sensing with Synthetic Aperture Radar in terms of imaging characteristics and potential applications.
