Andrés Felipe Betancur Pérez

The usefulness of smart antennas lies in enhancing the received signal from a particular direction while suppressing unwanted interfering signals and noise from other directions. This process is known as beamforming. In this paper, we study beamforming using different antenna array geometries to improve performance. We explore sparse arrays, including coprime and nested arrays, and employ a beamforming technique. The design of the antenna elements includes a half‐wavelength dipole and a rectangular patch antenna. Crucial array parameters such as the envelope correlation coefficient, spatial gain diversity, and mutual coupling are evaluated. The array pattern after beamforming is presented for each array antenna, and it was demonstrated that the sparse array achieves superior results compared to the uniform linear array. This work contributes to the intelligent management of the wireless channel, addressing requirements such as higher capacity, frequency reuse, low delay, and reliability in new mobile technologies such as 5G and beyond.

En este trabajo implementamos un sistema de comunicación por luz visible con modulación externa a través de una válvula de luz de $1.5 USD, un sensor de luz analógico de escala logarítmica, un lente de Fresnel de $5 USD, un LED de 12 V operando de forma continua, y 2 Raspberry Pi 3. Este trabajo es una iniciativa para explotar de manera directa la luz solar como fuente de radiación para complementar los sistemas VLC con un bajo costo de implementación. La válvula de luz permitió transmitir datos a una velocidad de 100 bps que sugiere un escenario de aplicación como las redes de sensores inalámbricos y en general para la Internet de las Cosas (IoT). Dado que no hay mucho espacio en el espectro radioeléctrico para dar lugar a nuevos servicios y tecnologías de comunicación inalámbrica, los sistemas VLC prometen ser un gran complemento a las redes de acceso inalámbricas convencionales, para balancear la carga del tráfico presente cuando exista una conexión masiva de dispositivos en el paradigma de IoT

In this research, we present an analysis of a photonic integrated frequency shifter as a stage for a THz dual comb generator. We studied the performance of the PIC by simulating it with standard building blocks, and aimed toward an improvement of the output signal quality. We revised two approaches of the PIC by simulating two modes of generating a double side band modulation suppressed carrier (DSB-SC) with a Mach Zehnder modulator structure (MZM). One approach was using a single Electro-Optic Phase Modulator (EOPM) on an MZM structure (SE-MZM), and the other one was using Double EOPM (DE-MZM). We found a cleaner spectrum with the DE-MZM, since this structure is usually applied to reduce the chirp effect in optical communication systems. We obtained 23 dB of side mode suppression ratio SMSR with one filter, and 44 dB of SMSR with a two-stage filter. In the case of DE-MZM, we obtained a clean tone on intermediate frequency (IF) free of spurious sidebands and comb in IF frequency with 10 dB more power compared to SE-MZM.

In this work, we present a multipurpose photonic integrated circuit capable of generating multiheterodyne complex Dual-Combs (DC) THz signals. Our work focuses on translating the functionality of an electro-optic tunable DC system into a photonic chip employing standard building blocks to ensure the scalability and cost efficiency of the integrated device. The architecture we analyze for integration is based on three stages: a seed comb, a mode selection stage and a DC stage. This final DC stage includes a frequency shifter, a key element to improve the final detection of the THz signals and obtain real-time operation. This investigation covers three key aspects: (1) a solution for comb line selection on GHz spaced combs using OIL or OPLL on photonic chips is studied and evaluated, (2) a simple and versatile scheme to produce a frequency shift using the double sideband suppressed carrier modulation technique and an asymmetric Mach Zehnder Interferometer to filter one of the sidebands is proposed, and (3) a multipurpose architecture that can offer a versatile effective device, moving from application-specific PICs to general-purpose PICs. Using the building blocks (BBs) available from an InP-based foundry, we obtained simulations that offer a high-quality Dual-Comb frequency shifted signal with a side mode suppression ratio around 21 dB, and 41 dB after photodetection with an intermediate frequency of 1 MHz. We tested our system to generate a Dual-Comb with 10 kHz of frequency spacing and an OOK modulation with 5 Gbps which can be down-converted to the THz range by a square law detector. It is also important to note that the presented architecture is multipurpose and can also be applied to THz communications. This design is a step to enable a commercial THz photonic chip for multiple applications such as THz spectroscopy, THz multispectral imaging and THz telecommunications and offers the possibility of being fabricated in a multi-project wafer.

An absolute-frequency terahertz (THz) dual-frequency comb spectrometer based on electro-optic modulators for tunable, high-resolution, and real-time rapid acquisition is presented. An optical line of a master frequency comb (filtered via optical injection locking) serves as the seed to electro-optically generate a pair of new frequency combs (probe and local oscillator). Photomixing both combs with another coherent line from the same original master comb generates a narrow linewidth THz dual-comb with teeth frequencies that can be referenced to a radio-frequency standard. The system is validated with a proof-of-principle measurement of a microwave filter in the W-band.

We present a compact and robust absolute-frequency THz dual-comb spectrometer based on electro-optic modulators that provides ultra-narrow linewidth teeth, a total control over both central and repetition frequencies and a high measurement speed.

PIN (positive intrinsic negative) photodiodes and analog-to-digital converters (ADC) are commonly used on visible light communication (VLC) receivers in order to retrieve the data on detected signals. In this paper, a visible light communication receiver based on a light to frequency converter (LTF) is proposed. We characterized the LTF and derived an equation for signal-to-noise ratio (SNR) estimation in terms of its input optical power, and the frequency of the output periodic signal. The experiments show that the periodic signal of the LTF converter has a maximum output frequency of 600 kHz at a distance of 6.2 cm. In this setup, measured SNR reached 18.75 dB, while the lowest obtained SNR with 1.1 m length was roughly −35.1 dB. The results obtained suggest that a bit rate of 150 kbps can be achieved with an on-off keying (OOK) modulation format. We analyzed the results and discuss the advantages and limitations of the LTF converter for optical wireless communication purposes.

Our first and very recent results on a new approach to obtain compact and practical, multi-octave spanning, absolute frequency and high accuracy THz dual-comb spectrometers based on Electro-Optic modulators (EOMs) are reported. Two different schemes are described and evaluated with the final objective of obtaining a practical solution for THz spectroscopy and other applications in such frequency range.