F. Las Heras

Design of Planar Artificial Magnetic Conductor Ground Plane Using Frequency-Selective Surfaces for Frequencies Below 1 GHz

A novel design of planar artificial magnetic conductor (AMC) based on a frequency-selective surface (FSS) for frequencies below 1 GHz is presented. A discussion about design parameters and the influence of dielectric substrate permittivity in the operating band and the operating bandwidth is presented. The discussion is supported by a finite element method (FEM) simulation.

Microwave Frequency Tripler Based on a Microstrip Gap with Graphene

In this work, a 3x frequency multiplier implemented with a microstrip gap covered with defoiled graphene is presented. The behaviour of the multiplier has been experimentally characterized for the input signal frequency band between 2.5 GHz and 5 GHz. Several graphene-based tripler devices have been implemented with different values for the line width and gap of the microstrip line in order to evaluate the influence of these parameters on the power of the output signal. The output power of the different devices has been measured in the band from 7.5 GHz to 15 GHz for different values of the input power. An almost flat frequency behaviour for the output power is observed along the whole input frequency band.

Frequency scanning probe for microwave imaging

Microwave imaging techniques have attracted considerable attention as a result of their multiple potential applications in different fields, such as industrial nondestructive testing, detection of buried or concealed objects, noninvasive medical diagnostics, etc. Different theoretical methods and measurement setups have been proposed, based on illuminating the object under investigation with single frequency [1], multi-frequency [1, 2, 3] or Ultra Wide Band (UWB) signals [4]. The scattered radiation is usually measured in different spatial directions (angular diversity), in order to increase the image resolution.

Novel polarization agile microstrip antenna

A novel agile antenna based on an injection-locked third harmonic self-oscillating mixer is presented in this paper. The phase-shift can be tuned, by varying the varactor control voltage, in range of 450deg. The active circuit allows changing the axial ratio of a dual-polarization antenna. The antenna can switch between radiating RHCP, LHCP and linear polarization with good purity.

Design of a submillimeter microstrip array for beam-scanning applications

A microstrip array antenna with beam-steering capabilities is presented for imaging applications working in the frequency range of 240–279 GHz. A 33 degrees beam-scanning range is achieved. The feeding network allows to change the beam-pointing angle from θ= −8° to θ= 25° while the frequency scanning is performed.

Receiving Polarization Agile Active Antenna Based on Injection Locked Harmonic Self Oscillating Mixers

A polarization agile active antenna with phase shifter elements based on injection locked third harmonic self oscillating mixers is presented. This phase shifting topology provides the double functionality of continuous range phase shifter and downconverter. The phase shift value introduced by each circuit can be easily tuned through a DC voltage within a theoretical continuous range of 450° . The behavior of the isolated phase shifter circuit is studied, both as a function of the control voltage and versus frequency, through harmonic balance and envelope transient simulations. The polarization tuning performance of the complete active antenna is simulated, analyzing the impact of the operating parameters of the phase shifter on the overall behavior. A receiving polarization agile antenna with an input frequency band centered at 11.25 GHz and an output frequency band centered at 1.5 GHz has been manufactured for the experimental validation of the simulated results. A continuous range of polarization tuning has been observed, including two orthogonal linear polarizations along with left hand and right hand circular polarization.

Transmitting Polarisation Agile Microstrip Antenna Based on Injection Locked Oscillators

In this work, a transmitting two port aperture coupled microstrip antenna with variable polarisation is presented using variable phase shifters based on Injection Locked Oscillators (ILO). The polarisation of the antenna can be tuned in a continuous range, enabling two orthogonal linear polarisations, and both right hand and left hand circular polarisation. The signals applied to the two antenna ports are generated by the ILO circuits and can be phase shifted in a continuous theoretical range of 180 degrees. The phase-shift versus the DC varactor control signal of the individual ILO circuits and the axial ratio of the ILO based polarisation agile antenna is studied through harmonic balance and envelope transient simulations in combination with electromagnetic simulations. A polarisation agile antenna at 10.735 GHz has been manufactured obtaining a good agreement between the simulated and experimentally obtained behaviour.

Design of a three port triple band aperture coupled microstrip antenna

A three port triple band aperture coupled microstrip antenna has been designed, manufactured and measured. Effective impedance matching has been achieved in the desired bands of operation in good agreement with the simulated results.

Terahertz frequency scanning 8×1 antenna array for imaging applications

An 8x1 frequency scanning antenna array has been presented for its operation in the 255-330 GHz frequency band. The antenna has been implemented using WR-3 rectangular waveguide structures and power combiner waveguide-structures in brass metal using mechanical micro-milling facilities. The antenna has been measured using a vector network analyzer and two 220-330 GHz frequency extender heads. The obtained steering range while varying the operation frequency in the 255-330 GHz range has exceeded successfully the required steering range of Δθ = 40°.

Transmitting polarisation agile antenna based on synchronised oscillators

A transmitting polarisation agile antenna based on injection locked oscillators has been presented. This phase shifting circuitry presents advantageous properties, such as relatively high power, ease of control and continuous phase shift range. A prototype of the system has been manufactured, providing a continuous range of polarisation variation including two linear and two circular polarisations.