L.F. Herran

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.

Nonlinear Optimization of Wide-Band Harmonic Self-Oscillating Mixers

A new optimization method is presented for the design of wide-band harmonic self-oscillating mixers (HSOMs). High conversion gain is obtained through near-bifurcation operation and optimization of the harmonic content of the self-oscillation. Bifurcation analysis- and control-techniques are used in combination with nonlinear optimization techniques based on the use of an auxiliary generator. An 11.25-1.5 GHz third harmonic self-oscillating mixer (3HSOM) with a 2.5 dB down-conversion gain over a 1.2 GHz bandwidth has been designed. A good agreement between the simulated and experimental results has been found.

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.

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.

High-accuracy neural-network-based array synthesis including element coupling

A novel neural-network (NN)-based technique for antenna array synthesis and a prototype of antenna array designed using it are presented. This technique is able to calculate the voltages that must be applied to the radiating elements considering all the physical properties of each element of the array and the coupling effects between all of them.

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.

Neural network-based pattern synthesis of array antennas with element specification

In this paper, a neural network (NN) based solution for obtaining the electric voltages applied at every port of the array feeding network, from radiation pattern information, is proposed. This is to avoid complexity from the designers point of view, and establish a relation between the desired radiation pattern and the voltages in the real antenna. The NN training phase must be performed through antenna modeling (including the feeding network) and full-waveform analysis methods, so that the data used for training implicitly consider a realistic model with interaction between elements.

Optimization framework on antenna arrays for near field multifocusing

This paper presents a new method for focusing on multiple targets simultaneously using antenna arrays. An optimization framework based on the Levenberg-Marquardt algorithm is used to concentrate the radiated field at certain positions. The proposed synthesis technique is a flexible method that can optimize different sets of parameters in the array, i.e., the weights (phase and/or magnitude) of the elements, their positions or all these features, in order to achieve this goal. Some illustrative examples using simulated and implemented antennas are addressed to evaluate this framework.

Substrate Integrated Waveguides Structures Using Frequency Selective Surfaces Operating in Stop-Band (SBFSS-SIW)

A novel Substrate Integrated Waveguide (SIW) is proposed using Frequency Selective Surfaces (FSS) operating in Stop-Band (SBFSS-SIW) as metal conductor plates. These structures preserve the propagation properties and the dimensions of the conventional SIW, and have periodic isolated pads that could allow the direct integration of biased active and passive devices on the SIW surface. A set of SBFSS-SIW for X-band have been designed, simulated and experimentally measured to demonstrate that SBFSS-SIWs can behave similar to conventional SIW structures when FSS cells are optimized to work far from its resonance frequency.

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.