Analysis and design of antennas and radiometers for radio astronomy applications in microwave, Mm-wave, and THz Bands

Mención Internacional en el título de doctorWe are living in interesting times for astronomy science, since the birth of the radio astronomy field in the 20th century by Karl Jansky, the availability of new and better radio astronomy receivers is in increasing demand to push the human understanding of the universe. In this thesis, various components (antennas, baluns, antenna-arrays, and radiometers) are proposed for radio astronomy receivers. The proposed designs are belonging to three receiver topologies (direct detection, down-conversion, and up-conversion) that operate at different frequency bands from MHz up to a few of THz. Also, to demonstrate that the same proposed design is capable of working efficiently at different operating frequencies, multiple adjusted designs are presented for several practical radio astronomy and space applications. Firstly, a receiver based on the direct detection of the Electromagnetic (EM) radiation through a radio telescope working on cryogenic cooling conditions. In this part, the focus is on designing conical log-spiral antennas and baluns (balanced to unbalanced transformers) to be used as feeds for VLBI Global Observing System (VGOS) ground-based radio telescopes. The feeds cover the Ultrawideband (UWB) from 2 GHz to 14 GHz with Circular Polarization (CP) radiation and stable radiation patterns. After integration of the feeds to the radio telescope, the whole system operates with high aperture efficiency and high System Equivalent Flux Density (SEFD) over the whole required wide range. The fabrication, assembly, and measurements for single-element and four-elements array are provided for achieving the requirements for single CP and dual CP operation. Also, in the same first part, the proposed single-element feed (antenna + balun) is readjusted for being used for CryoRad spaceborne Earth observations. This feed has a single CP over low-frequency UWB from 400MHz to 2 GHz with low weight and physical size compared to standard horn feeds. The second part of the thesis is dedicated to a THz source to be used as a local oscillator for heterodyne radio astronomy THz receivers in which the down-conversion of the THz radiation to a lower frequency occurs. The source is based on an array of self-complementary bow-tie antennas and photomixers that lies on a dielectric lens. The source can be scaled easily to cover different UWB ranges, three ranges are analyzed from 200 GHz to 2 THz, 100 GHz to 1 THz, and 50 GHz to 0.5 THz. Additionally, in this part, a complete study for the effects of metal losses on such THz planar antennas is performed which are not well-investigated in literature yet, the physical explanations behind such effects are also provided. Although these proposed THz sources themselves can work at room temperature, the receiver probably still needs the cooling for the other receiver components (such as the mixer) to work efficiently at such high frequencies. This is the motivation for the third part of this thesis which presents a different type of radio astronomy receiver that is completely able to work without cooling. The third receiver is based on the nonlinear up-converting of the microwave radiation into the optical domain using Whispering Gallery Mode (WGM) resonators which can work at room temperature efficiently. For such advantage and since this concept is naturally narrow-band, it can be a proper candidate for Cosmic Microwave Background (CMB) spectroscopy and space applications. The system design and its performance are analyzed for Ku band at 12 GHz with proposing a novel microwave coupling scheme for enhancing the up-conversion photonic efficiency which is the main limitation for such upconversion systems. Likewise, several high gain 3D-printed Dielectric Resonator Antenna (DRA)s are proposed in both isolated and array configurations to have a direct coupling of the microwave radiation to the proposed scheme. Another practical application for such receiver is presented for CubeSat missions at the mm-wave band (183 GHz) for climate change forecasting. It is clear here that removing the cryogenic cooling conditions decreases satellite weight and cost, which in turn significantly increases its lifetime. Also, it is worth noting that besides the radio astronomy applications, the proposed receivers (and/or their antenna/components) can be used for many other applications. For example, the UWB antennas in the first part can be used as wideband scalable probes for EM compatibility testing or other wireless systems that require single or dual CP such as radar and military applications. This is because the solutions provide constant beam characteristics with good CP polarization purity and stable performance over the operating UWB. In the same way, the proposed THz source in the second part can be used in several THz applications such as very high-speed wireless communications, highresolution imaging for medical and security purposes. This is because of its key benefits as decade bandwidth, compact size, low noise, low power demand, high tunability, and the ability to work at room temperature. For the up-conversion scheme proposed in the third part, due to its high photonic efficiency, low noise level which enables it to work at room temperature, and its scalability from a few GHz up to several THz, it is suitable for low-cost and high sensitivity applications. Specifically, the ones that need to get rid of the hard cryogenic cooling conditions, or at least, relax them and allow the system to work efficiently at higher temperatures. For instance, portable mm-wave and THz systems for quality control, security, and biochemistry. Finally, in this part, the proposed DRA elements and arrays, due to their low cost, high gain, and low losses, can be used for sensing applications and 5G base station antennas.Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan CarlosPresidente: Raed Shubair.- Secretario: Adrián Amor Martín.- Vocal: José Manuel Fernández Gonzále

Forecasting of Cairo Population using ARMA Model

The problem of large population is one of the most important factors influencingthe economy and social advancement of Egypt. Population forecasts, whencarefully and intelligently made, serves a valuable purpose in helping to direct theemployment of labor and capital to places or projects where they are most needed.Firstly, the paper focuses on studying the population of the capital of Egypt (Cairo).By large numbers of sampling to the population data sequence, the increasing trendis found. Then, a time series model is given which can accurately forecast thepopulation of Cairo. Multiple Autoregressive models AR (1), AR (2) are used theforecasting of the population in the next twenty years. The parameters of the modelare calculated using the famous two methods: Yule-Walker and Burg. Before usingthe model to make predictions, the test of model response is verified, and the MSEand MAPE are measured to verify the models. The result is a scary image of thepopulation in this city. Full descriptions for the steps of selecting the suitable modeland comprehensive MATLAB simulation are presented. Secondly, the totalpopulation density of Egypt is analyzing and forecasting with using the measureddata from 1970 to 2013. The same steps of the first part are done with thepopulation density and forecasting of the increasing of the population density ofEgypt in the 20 next years is presented. The main reasons for the populationproblem are discussed and solution of this problem is presente

A miniaturized triple-band and dual-polarized monopole antenna based on a CSRR perturbed ground plane

This paper proposes a new triple-band monopole antenna based on Complementary Split Ring Resonators (CSRR) perturbing the ground plane (GND). The antenna consists of an inverted-L-shaped monopole fed by a modified microstrip line with two CSRRs cut out of the ground plane. The operational bands are independently controlled by the CSRR unit cell parameters. In addition, the antenna presents a dual-polarization performance (vertical polarization at 2.4 GHz band and horizontal polarization at both 3.6 and 5.9 GHz bands). The designed antenna is fully planar and low profile avoiding the vias with the ground plane and covering the WLAN, WiMAX, and IEEE 801.11p bands at 2.45, 3.6, and 5.8 GHz. A compact prototype ( 0.32λ0×0.32λ0 being λ0 is the wavelength corresponding to the lowest resonance frequency) has been fabricated and measured showing good agreement between simulations and measurements. The measured impedance bandwidths are 10% (2.38-2.63 GHz), 2.5% (3.54-3.63 GHz), and 20% (5.83-7.12 GHz) whereas the measured gains are 1.34, 0.68, and 2.65 dBi at 2.4, 3.6, and 5.9 GHz respectively.This work was supported by PID2019-109984RB-C41

Sensitivity and noise in THz electro-optic upconversion radiometers

This paper presents a study of noise in room-temperature THz radiometers that use THz-to-optical upconversion followed by optical detection of thermal radiation. Despite some undesired upconverted thermal noise, no noise is intrinsically introduced by efcient electro-optic modulation via a sumfrequency-generation process in high quality factor (Q) whispering-gallery mode (WGM) resonators. However, coherent and incoherent optical detection results in fundamentally diferent noise characteristics. The analysis shows that the upconversion receiver is quantum limited like conventional amplifers and mixers, only when optical homodyne or heterodyne detection is performed. However, this type of receiver shows advantages as a THz photon counter, where counting is in the optical domain. Theoretical predictions show that upconversion-based room-temperature receivers can outperform state-of-the-art cooled and room-temperature THz receivers based on low-noise amplifers and mixers, provided that a photon conversion efciency greater than 1% is realized. Although the detection bandwidth is naturally narrow due to the highly resonant electro-optic modulator, it is not fundamentally limited and can be broadened by engineering selective optical coupling mechanisms to the resonator.Ministerio de Economía y Competitividad (MINECO) (TEC2013-47753-C3); Comunidad de Madrid MARTINLARA Project (ref. P2018/NMT-4333); FUNDACION SENER; Banco Santander (TEC2016-76997- C3-2-R); 2017 UC3M-Santander Chair of Excellence

An Integrated Millimeter-Wave Satellite Radiometer Working at Room-Temperature with High Photon Conversion Efficiency

In this work, the design of an integrated 183 GHz radiometer frontend for earth observation applications on satellites is presented. By means of the efficient electro-optic modulation of a laser pump with the observed millimeter-wave signal followed by the detection of the generated optical sideband, a room-temperature low-noise receiver frontend alternative to conventional Low Noise Amplifiers (LNAs) or Schottky mixers is proposed. Efficient millimeter-wave to 1550 nm upconversion is realized via a nonlinear optical process in a triply resonant high-Q Lithium Niobate (LN) Whispering Gallery Mode (WGM) resonator. By engineering a micromachined millimeter-wave cavity that maximizes the overlap with the optical modes while guaranteeing phase matching, the system has a predicted normalized photon-conversion efficiency = 10-1 per mW pump power, surpassing the state-of-the-art by around three orders of magnitude at millimeter-wave frequencies. A piezo-driven millimeter-wave tuning mechanism is designed to compensate for the fabrication and assembly tolerances and reduces the complexity of the manufacturing process.This research was funded by Fundación SENER (REFTA), Comunidad de Madrid MARTINLARA-CM (P2018/NMT-4333), Agencia Estatal de Investigacion (PID2019-109984RBC41), and RTC2017-6394-7 projects

3-D-Printed dielectric resonator antenna arrays based on standing-wave feeding approach

A novel feeding method for a dielectric resonator array antenna is introduced. Unlike in a corporate feed network, power dividers or quarter-wave transformers are not needed in the new feeding scheme as the design is based on the standing-wave concept. Consequently, the feed network is greatly simplified, and undesired spurious radiation in the feeding network is minimized. The simulated and measured results are in good agreement. A 3-D printer is utilized where the entire array structure is fabricated as a single piece with a dielectric material of polylactic acid. The 3-D printer provides a cost-efficient, simple, and rapid manufacturing process.This work was supported by Comunidad de Madrid under Projects S2018/NMT-4333 MARTINLARA-CM and TEC2016-80386-P.Publicad

Standing-Wave Feeding for High-Gain Linear Dielectric Resonator Antenna (DRA) Array

A novel feeding method for linear DRA arrays is presented, illuminating the use of the power divider, transitions, and launchers, and keeping uniform excitation to array elements. This results in a high-gain DRA array with low losses with a design that is simple, compact and inexpensive. The proposed feeding method is based on exciting standing waves using discrete metallic patches in a simple design procedure. Two arrays with two and four DRA elements are presented as a proof of concept, which provide high gains of 12 and 15 dBi, respectively, which are close to the theoretical limit based on array theory. The radiation efficiency for both arrays is about 93%, which is equal to the array element efficiency, confirming that the feeding method does not add losses as in the case of standard methods. To facilitate the fabrication process, the entire array structure is 3D-printed, which significantly decreases the complexity of fabrication and alignment. Compared to state-of-the-art feeding techniques, the proposed method provides higher gain and higher efficiency with a smaller electrical size.This research was funded by Fundación SENER (REFTA), Comunidad de Madrid MARTINLARA-CM (P2018/NMT-4333), Agencia Estatal de Investigacion (PID2019-109984RB-C41), and RTC2017-6394-7 projects

Maximization of the optical intra-cavity power of whispering-gallery mode resonators via coupling prism

In this paper, a detailed description of the optical coupling into a Whispering Gallery Mode (WGM) resonator through a prism via frustrated total internal reflection (FTIR) is presented. The problem is modeled as three media with planar interfaces and closed expressions for FTIR are given. Then, the curvature of the resonator is taken into account and the mode overlap is theoretically studied. A new analytical expression giving the optimal geometry of a disc-shaped or ring-shaped resonator for maximizing the intra-cavity circulating power is presented. Such expression takes into consideration the spatial distribution of the WGM at the surface of the resonator, thus being more accurate than the currently used expressions. It also takes into account the geometry of the prism. It is shown an improvement in the geometry values used with the current expressions of about 30%. The reason why the pump laser signal can be seen in experiments under critical coupling is explained on this basis. Then, the conditions required for exciting the highest possible optical power inside the resonator are obtained. The aim is to achieve a highly-efficient up-conversion of a THz signal into the optical domain via the second-order nonlinearity of the resonator material.This work has been financially supported by "DiDaCTIC: Desarrollo de un sistema de comunicaciones inalámbrico en rango THz integrado de alta tasa de datos", TEC2013-47753-C3, CAM S2013/ICE-3004 "DIFRAGEOS" projects, "Proyecto realizado con la Ayuda Fundación BBVA a Investigadores y Creadores Culturales 2016" and "Estancias de movilidad de profesores PRX16/00021"

Photonic-based integrated sources and antenna arrays for broadband wireless links in terahertz communications

This paper analyzes integrated components for ultra-broadband millimeter-wave wireless transmitters enabling the 5 G objective to increase the wireless data rates 10x to 100x . We have pursued the photonic-based approach to generate the millimeter-wave carrier (approximate to 97GHz in this paper) through photomixing. We have achieved up to 10 Gb s(-1) data rate using an OOK modulation format (to reduce latency) and either direct detection (DD) or coherent detection. We show that coherent detection enables a sensitivity improvement of 17 dB over DD. We also demonstrate in this work that such improvement can be achieved using as the transmitter a novel integrated antenna array-the self-complementary chessboard array. This avoids the use of complex coherent schemes at the receiver, enabling simple DD for ultra-broadband links.The authors acknowledge Dr David Gonzalez Ovejero for fruitful discussions on antenna simulation. This work has been financially supported by Ministerio de Economia, Industria y Competitividad iTWIT Proyect with references TEC2016-76 997-C3-2-R and TEC2016-76 997-C3-3-R. Authors also acknowledge Ayuda Fundacion BBVA a Investigadores y Creadores Culturales 2016' and 'Estancias de movilidad de profesores PRX16/00 021'

Enhancement of a text-independent speaker verification system by using feature combination and parallel structure classifiers

Speaker verification (SV) systems involve mainly two individual stages: feature extraction and classification. In this paper, we explore these two modules with the aim of improving the performance of a speaker verification system under noisy conditions. On the one hand, the choice of the most appropriate acoustic features is a crucial factor for performing robust speaker verification. The acoustic parameters used in the proposed system are: Mel Frequency Cepstral Coefficients, their first and second derivatives (Deltas and Delta-Deltas), Bark Frequency Cepstral Coefficients, Perceptual Linear Predictive, and Relative Spectral Transform Perceptual Linear Predictive. In this paper, a complete comparison of different combinations of the previous features is discussed. On the other hand, the major weakness of a conventional support vector machine (SVM) classifier is the use of generic traditional kernel functions to compute the distances among data points. However, the kernel function of an SVM has great influence on its performance. In this work, we propose the combination of two SVM-based classifiers with different kernel functions: linear kernel and Gaussian radial basis function kernel with a logistic regression classifier. The combination is carried out by means of a parallel structure approach, in which different voting rules to take the final decision are considered. Results show that significant improvement in the performance of the SV system is achieved by using the combined features with the combined classifiers either with clean speech or in the presence of noise. Finally, to enhance the system more in noisy environments, the inclusion of the multiband noise removal technique as a preprocessing stage is proposed.The authors want to thank Erasmus Mundus 3Green-IT ́ program for its grant for providing the funding for this work. This work has also been partially supported by the Spanish Government Grant TEC2014-53390-P and by the Regional Government of Madrid S2013/ICE-2845-CASI-CAM±CM project