arXiv subjects

Rasool Keshavarz

Publications and source records attributed to Rasool Keshavarz.

21 records · Page 2Linked to original sources

arXiv2024

Highly Sensitive Differential Microwave Sensor for Soil Moisture Measurement

This paper presents a highly sensitive differential soil moisture sensor (DSMS) using a microstrip line loaded with triangular two turn resonator(T2 SR) and complementary of the rectangular two turn spiral resonator(CR2 SR),simultaneously.Volumetric Water Content (VWC) or permittivity sensing is conducted by loading the T2 SR side with dielectric samples.Two transmission notches are observed for identical loads relating to T2 SR and CR2 SR.The CR2 SR notch at 4.39 GHz is used as a reference for differential permittivity measurement method.Further, the resonance frequency of T2 SR is measured relative to the reference value. Based on this frequency difference,the permittivity of soil is calculated which is related to the soil VWC.Triangular two turn resonator (T2 SR) resonance frequency changes from 4 to 2.38 GHz when VWC varies 0 percent to 30 percent.The sensor's operation principle is described through circuit model analysis and simulations.To validate the differential sensing concept, prototype of the designed 3 cell DSMS is fabricated and measured.The proposed sensor exhibits frequency shift of 110 MHz for 1 percent change at the highest soil moisture content (30 percent) for sandy type soil.This work proves the differential microwave sensing concept for precision agriculture.

physics.ins-det↗

arXiv2024

Autonomous Nonlinear Passive Transmit-Receive Switch for Compact IoT Devices: A Three-Port Agile Network

Recent advancements in RF technologies, especially Internet of Things (IoT) devices, require compact and integrated RF circulators or transmit-receive (TR) switches for efficient resource use. Although conventional techniques are crucial in managing signal flow to prevent signal interference to sensitive receiver components, they have some drawbacks, such as limited isolation, low switching speed, complex circuitry, bulkiness, and high cost. This work presents a smart, miniaturized, nonlinear TR switch capable of operating over a wide frequency range (0.8 - 1.3 GHz), making it suitable for IoT frequency bands. The switch achieves high isolation, low insertion loss, and intelligent transitions between transmitter and receiver without requiring external control or bias pins.

eess.SY↗

arXiv2024

Terahertz Digital Reconfigurable Metamaterial Array for Dynamic Beamforming Applications

A novel digital reconfigurable 2_bit metamaterial, equipped with a substrate integrated feeding system, is designed for industrial quality control applications within the terahertz frequency range. The proposed feeding mechanism facilitates azimuthal beam steering, spanning from negative 90 degree to positive 90 degree, thereby enabling the reconfiguration of beam patterns within the digital metamaterial. Utilizing the phase distribution concept and comprehensive analysis of coupling and the e_field effect on individual unit cells, the metamaterial array spacing is meticulously designed. Operational at 0.7 THz, the system offers versatile reconfigurability, supporting single, dual, and multibeam modes. Through meticulous optimization, the system demonstrates an impressive negative 138 degree to positive 138 degree beam steering capability. This dynamic beamforming ability, transitioning seamlessly from a singular beam to multibeam configurations, requires minimal software-hardware integration for scanning and inter_satellite links, thus presenting significant potential for enhancing product quality within industrial environments and satellite communication.

physics.optics↗