Analysis of an arbitrarily inclined slot on the ground plane of amicrostrip line

The analysis of an arbitrarily inclined slot on the ground plane of a microstrip line is presented using the spectral domain approach and reciprocity theorem. Comparison of numerical results for the special case of a perpendicular slot with other available computed and measured data shows a good agreement. It is found that the impedance level can be controlled over a wide range by varying inclination angle. Results should be useful in antenna and multilayer circuit integration applications     

Composite right/left handed artificial transmission line structures in CMOS for controlled insertion phase at 30 GHz

Two CMOS integrated circuits are presented that utilize metamaterial composite right/left handed (CRLH) transmission lines (TLs) for zero insertion phase at 30 GHz. Specifically, 2 and 3 unit cell structures are presented with controlled insertion phase that is achieved by cascading lumped element capacitors and spiral inductors in an LC network configuration defining the TL unit cells. Furthermore, the fixed TL structures suggest the possibility of zero, advanced or delayed insertion phases by element variation, or by the use of simple active components. Simulation and measured results are in good agreement with CRLH TL theory, and display a linear insertion phase and flat group delay values that are dependent on the number of unit cells with an insertion loss of ～0.8 dB per cell. These findings suggest that such high speed CRLH TLs structures can be implemented for linear array feeding networks and compact antenna designs in CMOS at millimeter wave frequencies. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Surface and bulk properties of ancient Egyptian mortars. Part I: X-ray diffraction studies

A series of Ancient Egyptian Mortars were extracted from the great Giza Pyramid, the second Giza Pyramid and the Sphinx and its adjoining temple. X-Ray Diffraction studies revealed the presence of gypsum, calcite and silica in most of the samples with a clearcut predominance of gypsum in the samples extracted from the Sphinx. Calcium silicates of different crystallographic modifications seem to be present in a large proportion of the samples. X-Ray studies carried out on heat-treated samples indicated the prevalence of the hemihydrate or γ-CaSO₄ modification until a temperature as high as 400°C.     

A Compact Wide-Band Rat-Race Hybrid Using Microstrip Lines

A compact microstrip rat-race hybrid with a 50% bandwidth employing space-filling curves is reported in this letter. The footprint of the proposed design occupies 31% of the area of the conventional similar design. Across the frequency bandwidth, the maximum amplitude unbalance is 0.5 dB, the phase variation is plusmn5^deg , the isolation is better than 25 dB and the return loss is greater than 10 dB. Moreover, the circuit is planar, easy to design, and consists of only one layer without requiring plated thru holes, slots or bonding wires.     

Performance of 1-10-GHz traveling wave amplifiers in 0.18-/spl mu/m CMOS

The authors present two four-stage traveling-wave amplifiers (TWA) fabricated in a 0.18-/spl mu/m CMOS process. A TWA with an internal drain bias network achieved a gain of 5 dB out to 10 GHz, and another TWA without an on-chip bias network achieved a gain of 8 dB out to 10 GHz. These are the highest frequency CMOS TWAs known to the authors.     

Comb-shaped circularly polarised dielectric resonator antenna

A new shaped circularly polarised dielectric resonator antenna is proposed. This antenna, compared to some previous investigations, is easier to implement, free from a complicated feed network and offers wider axial ratio bandwidth. About 4% AR bandwidth (<3 dB) with S/sub 11/<-10 dB and 3.5 dBi peak gain is reported.     

Theoretical considerations in the optimization of surface waves on a planar structure

The problem of optimum excitation of surface waves on a grounded dielectric slab by means of slots in the ground plane is considered. By adopting a two-dimensional (2-D) model, analysis lead to closed forms for the power launched as surface waves and power leaked as radiation. Input admittance of a single slot source and mutual admittance between two slots are derived and utilized to design a three element Yagi array of slots to achieve a prescribed ratio of forward to backward surface wave power. As a development of the 2-D model, we allow finite extent of slot excitation by assuming a Gaussian E-field distribution across the slot. The effect of the Gaussian width on the excited surface wave power is studied. The analysis is relevant to the study of surface waves on printed circuits. Specifically, it applies to the implementation of power combiners based on quasioptical slab beam that have been recently introduced in the literature for use in the millimeter wave band.     

Comprehensive study of multiband unconditional stabilization of common-source and common-gate MESFET transistors using feedback

The use of a new feedback scheme to achieve unconditionally stable MESFET transistors from 0 GHz until cutoff is presented. The methodology is applied for both common-source and common-gate MESFET transistor configurations. Analytical formulation of the stabilization methodology is presented. In addition, two coplanar-waveguide-based amplifiers were designed to operate at Ka-band, monolithically fabricated, and tested, thus, verifying the methodology. The study includes the effects of the bias change on the feedback amplifier stability performance.