Farshid Ghasemi

Propagation Engineering in Wireless Communications

Propagation Engineering in Wireless Communications covers the basic principles needed for understanding of radiowaves propagation for common frequency bands used in radio-communications. This book includes descriptions of new achievements and new developements in propagation models for wireless communication. The book is intended to bridge the gap between the theoretical calculations and approaches to the applied procedures needed for radio links design in a proper manner. The authors intention is to emphasize propagation engineering by giving sufficient fundamental information and then going on to explain the use of basic principles together with technical achievements in this field.

Self-referenced silicon nitride array microring biosensor for toxin detection using glycans at visible wavelength

We report on application of on-chip referencing to improve the limit-of-detection (LOD) in compact silicon nitride (SiN) microring arrays. Microring resonators, fabricated by e-beam lithography and fluorine-based etching, are designed for visible wavelengths (656nm) and have a footprint of 20 x 20 μm. GM1 ganglioside is used as the specific ligand for recognition of Cholera Toxin Subunit B (CTB), with Ricinus Communis Agglutinin I (RCA I) as a negative control. Using micro-cantilever based printing less than 10 pL of glycan solution is consumed per microring. Real-time data on analyte binding is extracted from the shifts in resonance wavelengths of the microrings.

Propagation Engineering in Radio Links Design

This book addresses propagation phenomena in satellite, radar, broadcasting, short range , trans-horizon and several recent modes of communications in radio links. Also, it includes some topics on antennas , radio noises and improvement techniques. The book provides the necessary basic matters, as well as experimental results and calculation procedures for radio link design.

Closed-Form Relations for Resonance Detection Error Using Statistical Analysis of Amplitude Noise

The optimization of resonance-tracking sensors relies critically on proper estimation of resonance detection error. We study this error in two common resonance detection algorithms: the absolute minimum method and the linear regression method. Closed-form relations for the error originating from additive noise are presented. The formulation accommodates the majority of lineshapes of practical interest and a wide variety of noise statistics. Lorentzian and Fano line shapes are studied here with further detail for their practical importance. It is discussed that while the performance of the absolute minimum method depends on the tail of the noise probability distribution function, for the linear regression method the total noise power is the determining characteristic of the noise. This fact is explained for the specific case of quantization noise. The results of this study enable a quantitative comparison of the performance of resonance-based sensors, which is a center piece in the optimization of their limit of detection.

Compact fluorescence sensor using on-chip silicon nitride microdisk

We demonstrate a compact on-chip fluorescence sensor using small silicon nitride microdisk resonators, designed to enhance the pump, collect fluorescence emission, and suppress the pump at the collection port with 53dB extinction.

Basic Principles in Radiowave Propagation

This chapter is dedicated to basic principles commonly used in radiowaves propagation and will be frequently referred to in succeeding chapters. Due to the variety of topics to be discussed, only brief and general descriptions and formulas are given. The details can be found in more specialized references.

Multiplexed detection of lectins using integrated glycan-coated microring resonators

We present the systematic design, fabrication, and characterization of a multiplexed label-free lab-on-a-chip biosensor using silicon nitride (SiN) microring resonators. Sensor design is addressed through a systematic approach that enables optimizing the sensor according to the specific noise characteristics of the setup. We find that an optimal 6 dB undercoupled resonator consumes 40% less power in our platform to achieve the same limit-of-detection as the conventional designs using critically coupled resonators that have the maximum light-matter interaction. We lay out an optimization framework that enables the generalization of our method for any type of optical resonator and noise characteristics. The device is fabricated using a CMOS-compatible process, and an efficient swabbing lift-off technique is introduced for the deposition of the protective oxide layer. This technique increases the lift-off quality and yield compared to common lift-off methods based on agitation. The complete sensor system, including microfluidic flow cell and surface functionalization with glycan receptors, is tested for the multiplexed detection of Aleuria Aurantia Lectin (AAL) and Sambucus Nigra Lectin (SNA). Further analysis shows that the sensor limit of detection is 2 × 10(-6) RIU for bulk refractive index, 1 pg/mm(2) for surface-adsorbed mass, and ∼ 10 pM for the glycan/lectins studied here.

Propagation in 3 kHz to 30 MHz Band

In the previous chapters, we considered the general concepts of radiowave propagation, especially in the troposphere and ionosphere. This chapter is dedicated to study of wave propagation in 3 kHz to 30 MHz frequency range, which is classified by ITU as VLF, LF, MF, and HF frequency bands.

Radiowave Propagation in Ionosphere

In Chap.3, the fundamental phenomena of troposphere were investigated and their effects on radiowaves propagation were explained. This chapter is dedicated to study the main phenomena of radiowave propagation in the ionosphere. As shown in Fig.4.1, this layer basically starts from the height of 50 km above the Earth and extends up to the height of 600 km. Although, in some references it is addressed up to the height of 1,000km, but the main effects of these phenomena appear at heights up to 600 km.

Introduction to Radiowaves

In 1865, James Clerk Maxwell introduced the notion of electromagnetic (EM) waves propagating with constant speed in homogenous media, based on relations between varying electric and magnetic fields. The speed of EM waves in free space corresponds to the speed of light and is equal to 3 ×108 m/s. Several years later, a German scientist named Hertz found out that radiowaves have a nature similar to EM waves but they are invisible.