Miguel Fernández

Design and analysis of a microwave large-range variable phase-shifter based on an injection-locked harmonic self-oscillating mixer

In this letter, a new microwave variable phase-shifter based on an injection-locked harmonic self-oscillating mixer, is presented for its application in an active microstrip phased antenna array. The circuit provides the double functionality of variable phase-shifter and down-converter. Maximum conversion gain is obtained, through the optimization of a new multi-harmonic load at the input-port of the circuit. The ranges of synchronized operation are analyzed versus the circuit parameters and the corresponding phase-shifts are calculated. The stability of the synchronized solutions is analyzed using the envelope transient simulation method. An 11.25-1.5-GHz down-converter with a 3.25-GHz free-running frequency has been designed, providing a phase-shift variation at intermediate frequency up to 540/spl deg/, with a 4.5-dB conversion gain. A good agreement between the simulated and experimental results has been found.

Submillimeter-Wave Frequency Scanning System for Imaging Applications

A new submillimeter-wave imaging system based on the frequency scanning concept is presented. Using significantly less information than beam-steering techniques, frequency scanning-based imaging systems are able to provide angular information in range-based radar systems which do not allow mechanical or electronic beam steering. Several strategies have been adopted to overcome the low dynamic range due to the propagation losses and non-specular reflection on the object-under-test. Moreover, the system is not only capable of detecting the placement of the objects, but also their profile. In this sense, an imaging application showing the system capabilities for the detection of objects concealed under clothes is presented. Results using 1-D FSAA allowing profile imaging are shown, proving the validity of the proposed system.

Receiving Phased Antenna Array Based on Injection-Locked Harmonic Self-Oscillating Mixers

A 4 times 1 element receiving phased antenna array is presented with phase-shifter elements based on injection-locked harmonic self-oscillating mixers. Each phase-shifter element provides the double functionality of variable phase-shifter and down-converter. The phase-shifts applied to the input signals coming from the different antenna patch elements can be selected by dc control signals in a continuous range of 450deg. The required dc control voltages are calculated for the different incident angles by means of harmonic balance simulations. The influences of phase-shift and conversion gain errors on the beam-steering frequency performance of the antenna are studied. Also illustrated is how the phase-shifter parameters can be optimized in order to minimize the frequency scanning. A 4 times 1 element receiving phased antenna array, with an input frequency band centered at 11.25 GHz and the output frequency band centered at 1.5 GHz, has been manufactured for the experimental validation of the simulated results. A beam scanning range from -23deg to 23deg has been experimentally obtained.

A receiving phased array antenna topology based on Mutually Coupled Harmonic Self-Oscillating Mixers

A design of a receiving 4×1 element phased antenna array based on Mutually Coupled Third Harmonic Self-Oscillating Mixers has been presented. The use of the third harmonic of the self-oscillation allows higher beam steering angles without extra circuitry showing the potential these multifunctional circuits have. The experimental behavior obtained with the receiving phased antenna array has been compared with the simulated results, at the optimum working point of the inner elements. A good agreement in the beam scanning between the simulations and measurements has been shown.

Millimetre wave imaging system for the detection of hidden elements in artwork

In this work, a millimetre/sub-millimetre wave imaging system for the analysis, characterisation and detection of hidden elements in artwork is presented. The practical implementation of the system relies on a novel generation of purpose developed frequency multiplier and mixer topologies, based on graphene non-linear devices. The proposed set-up will be experimentally validated by scanning a model painting, in order to practically illustrate the imaging capabilities of the system.

Flood Analysis: On the Automation of the Geomorphological-Historical Method

Different methods to assess the flood return period are available in the literature. The hydrological-hydraulic approaches, among the best-known quantitative methods, oversimplify the complex characteristics of the fluvial systems. Additionally, they rely on data that are usually criticized because of their low quality and representativity. In contrast, the semi-quantitative approach based on geomorphological and historical information has lead to more realistic and promising results in pilot studies. This approach is based on highly informative field data providing valuable knowledge which can be used to test the aforementioned quantitative approaches. The aim of this work is to analyze the kind of information that is required to apply the latter method and to explore the possibilities of its automation.

Submillimeter Wavelength 2-D Frequency Scanning Antenna Based on Slotted Waveguides Fed Through a Phase Shifting Network

This paper describes a 2-D frequency scanning array, operating in the 240–310-GHz frequency range, which is intended to be used in electromagnetic imaging applications. The proposed antenna combines eight slotted waveguides that are parallel fed through a frequency-dependent phase shifting network. As the working frequency is swept in the considered range, the inherent frequency-dependent behavior of the slotted waveguide causes beam scanning in one plane, while the progressive phase shift introduced by the feeding network provides beam steering in the perpendicular direction. The influence of the particular negative effects that suffer the employed structures on the array performance is carefully analyzed to determine the viability of this approach. A prototype has been implemented and experimentally characterized. The manufactured antenna presents a measured 20-dBi minimum gain and it is able to scan a

3D printed millimeter wave receiver integrating a graphene subharmonic mixer and a diagonal horn antenna

60 {^{\circ }}\times 20 {^{\circ }}

Millimetre wave receiver based on a few-layer graphene WR-5 band subharmonic mixer

space region, which would be large enough for a great number of imaging applications.

7 th order sub-millimeter wave frequency multiplier based on graphene implemented using a microstrip transition between two rectangular waveguides

This work presents a millimeter/submillimeter wave frequency receiver integrating a graphene subharmonic mixer and a diagonal horn antenna. The device receives the RF signal through the diagonal horn antenna directly connected to the WR-3 input of the mixer. The desired frequency mixing performance is obtained using the non-linear behavior of a few-layer graphene film placed on a microstrip line gap. Using the internally generated 6th, 8th and 10th harmonic components of the input signal provided by the WR-28 standard waveguide in the 26-40 GHz the downconversion operation of the RF signal to a 300 MHz intermediate frequency is performed. A prototype of the receiver has been manufactured using high precision 3D printing technology. The performance of this device is characterized taking into account the behavior of the IF power in the 220-330 GHz band. Measured radiation patterns are also included.