There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Optimization Techniques with FORTRAN

This paper reviews and analyzes four reported low-noise amplifier (LNA) design techniques applied to the cascode topology based on CMOS technology: classical noise matching, simultaneous noise and input matching (SNIM), power-constrained noise optimization, and power-constrained simultaneous noise and input matching (PCSNIM) techniques. Very simple and insightful sets of noise parameter expressions are newly introduced for the SNIM and PCSNIM techniques. Based on the noise parameter equations, this paper provides clear understanding of the design principles, fundamental limitations, and advantages of the four reported LNA design techniques so that the designers can get the overall LNA design perspective. As a demonstration for the proposed design principle of the PCSNIM technique, a very low-power folded-cascode LNA is implemented based on 0.25-/spl mu/m CMOS technology for 900-MHz Zigbee applications. Measurement results show the noise figure of 1.35 dB, power gain of 12 dB, and input third-order intermodulation product of -4dBm while dissipating 1.6 mA from a 1.25-V supply (0.7 mA for the input NMOS transistor only). The overall behavior of the implemented LNA shows good agreement with theoretical predictions.

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CMOS low-noise amplifier design optimization techniques

We propose the concept of ultra-broadband terahertz communication, based on directed non-line-of-sight (NLOS) transmissions. Potential applications of such a system supporting multi-gigabit data rates are given, and put into the context of currently emerging WLANs/WPANs. The technology and propagation constraints serve as boundary conditions for the determination of the required antenna gain to support ultra-broadband communication. Resulting high-gain antenna requirements will necessitate highly directed transmissions. We propose the use of omni-directional dielectric mirrors to support directed NLOS paths. Their performance is investigated with ray-tracing simulations of a terahertz propagation channel in a dynamic office environment, which is calibrated with measured building-material and mirror parameters. We demonstrate that a directed NLOS path scheme will make a terahertz communication system robust to shadowing. Furthermore, we show that dielectric mirrors covering only parts of the walls will significantly enhance the signal coverage in a typical indoor scenario.

Short-Range Ultra-Broadband Terahertz Communications: Concepts and Perspectives

Terahertz fields and applications

An enhanced model for an open-ended coaxial probe used for making permittivity measurements is presented. A permittivity measurement system consisting of the coaxial probe and a network analyzer is described including details of the error correction and curve fitting techniques. Determination of the percent dissolved solids in fructose solutions from permittivity measurements is presented as example of the usefulness of the coaxial probe/network analyzer measurement system.

An improved technique for permittivity measurements using a coaxial probe

A novel planar substrate integrated waveguide cavity resonator technique for measurement of complex permittivity is described, which has applications for dielectric measurement systems in the pharmaceutical industry. The high-Q resonant structure is a modernization of well-known measurement cells where the dielectric constant is deduced by cavity perturbation from the shift in resonant frequency and the change in the Q factor. The method uses extremely small amounts of a broad range of materials for accurate characterization. The ease of fabrication, low cost, and potential for integration with many other components on the same substrate allows it to be used in a disposable manner.

Substrate Integrated Waveguide Cavity Resonators for Complex Permittivity Characterization of Materials

With the exception of predistortion, most design methods for microwave filters are based on lossless prototype networks, with the effects of loss generally being considered afterwards, by analysis rather than synthesis. This paper presents new techniques, which either utilize existing losses, or add losses, to improve the performance of microwave bandpass filters. Unlike predistortion, these new techniques result in networks with nonuniform dissipation. Experimental prototype filters have been designed and the measured results demonstrate improved performance compared with that previously reported

The Design of Microwave Bandpass Filters Using Resonators With Nonuniform $ Q$

The fabrication and characterization of micromachined reduced-height air-filled rectangular waveguide components suitable for integration is reported in this paper. The lithographic technique used permits structures with heights of up to 100 /spl mu/m to be successfully constructed in a repeatable manner. Waveguide S-parameter measurements at frequencies between 75-110 GHz using a vector network analyzer demonstrate low loss propagation in the TE/sub 10/ mode reaching 0.2 dB per wavelength. Scanning electron microscope photographs of conventional and micromachined waveguides show that the fabrication technique can provide a superior surface finish than possible with commercially available components. In order to circumvent problems in efficiently coupling free-space propagating beams to the reduced-height G-band waveguides, as well as to characterize them using quasi-optical techniques, a novel integrated micromachined slotted horn antenna has been designed and fabricated, E-, H-, and D-plane far-field antenna pattern measurements at different frequencies using a quasi-optical setup show that the fabricated structures are optimized for 180-GHz operation with an E-plane half-power beamwidth of 32/spl deg/ elevated 35/spl deg/ above the substrate, a symmetrical H-plane pattern with a half-power beamwidth of 23/spl deg/ and a maximum D-plane cross-polar level of -33 dB. Far-field pattern simulations using HFSS show good agreement with experimental results.

Fabrication and characterization of micromachined rectangular waveguide components for use at millimeter-wave and terahertz frequencies

Normal realizations of bandstop resonators with finite unloaded Q suffer from degradation of performance due dissipation loss. In this paper, it is shown theoretically that there exists a class of second-order networks which simultaneously exhibit an ideal bandstop resonance, with infinite stopband attenuation, and a perfect match at all frequencies. Theoretical analysis is backed up with experimental results for three different physical realizations.

Roger D. Pollard

Papers

An improved technique for permittivity measurements using a coaxial probe

Substrate Integrated Waveguide Cavity Resonators for Complex Permittivity Characterization of Materials

The Design of Microwave Bandpass Filters Using Resonators With Nonuniform $ Q$

Fabrication and characterization of micromachined rectangular waveguide components for use at millimeter-wave and terahertz frequencies

Perfectly-matched bandstop filters using lossy resonators