Miguel Fernandez-Garcia

MICROSTRIP ANTENNA DESIGN BASED ON STACKED PATCHES FOR RECONFIGURABLE TWO DIMENSIONAL PLANAR ARRAY TOPOLOGIES

In this work, a probe fed microstrip antenna design for the implementation of two dimensional arrays with individually fed radiating elements is presented. The performance of the antenna element, both isolated and in a 4 £ 4 flxed array topology, is analysed using ADS and HFSS simulation software. Prototypes of the antenna element and of the array are manufactured and measured for the experimental validation of the design.

MILLIMETER WAVE MICROSTRIP MIXER BASED ON GRAPHENE

In this work, a millimeter wave microstrip frequency-mixer design based on graphene is presented. The desired frequency mixing behavior is obtained using a nonlinear component consisting in a microstrip line gap covered by a graphene layer. The circuit includes microstrip fllters that have been designed to obtain a high isolation between the input and output ports. The nonlinear behavior of the frequency mixer has been experimentally evaluated in the 38.6{40GHz input signal frequency range, for difierent values of the input power and local oscillator power.

Multi-Harmonic DC-Bias Network Based on Arbitrarily Width Modulated Microstrip Line

In this work, we present a novel DC-bias network for multi- harmonic microwave circuits based on an arbitrarily width-modulated microstrip line. The arbitrary shape of the width-modulated microstrip line is obtained by using multiple microstrip taper sections. The method is illustrated through the design of four difierent DC-bias networks blocking from 1 to 4 harmonic components of a 2.5GHz signal. The designs with an optimum shape for the arbitrarily width- modulated microstrip line have been manufactured and measured, obtaining a good agreement between the simulated and measured behavior.

Optimization of the Synchronization Bandwidth of Rationally Synchronized Oscillators Based on Bifurcation Control

In this work, a nonlinear technique for the optimization of the synchronization bandwidth of Rationally Synchronized Oscillators (RSO) is presented. The circuit is forced to operate near a Hopf bifurcation point which is created around the frequency of the input reference signal. Under this operating regime, the reference signal is strongly amplified and the synchronization bandwidth of the circuit is considerably improved. A 5–3GHz rationally synchronized oscillator has been optimized using the proposed method. The manufactured RSO provides a 5 MHz synchronization bandwidth with a reference signal power of −22 dBm, in good agreement with simulation results.

A novel phaseless frequency scanning based on indirect holography

A phase retrieval technique for multifrequency scattered field acquisition is presented in this paper. The proposed setup is based on indirect holography schemes so that it combines the desired signal with a known reference signal. The setup is used together with a two-dimensional frequency scanning (FS) antenna and, therefore, the positions of scatterers can be retrieved without the need of moving either the antenna or the objects.

Design and Analysis of a Multi-Carrier Tx-Rx System Based on Rationally Synchronized Oscillators for Localization Applications

In this work, a novel multi-carrier Tx-Rx system based on rationally synchronized oscillators to be used in RF-source localization applications is presented. The Tx subsystem is composed by two rationally synchronized oscillators, with different operation frequency, which share the reference signal. This signal is transmitted together with the one generated by the oscillators. In the Rx subsystem, the reference signal is provided by an oscillator which is synchronized with the received reference signal. According to the simulation results, with the proposed approach, the determination of the relative phase variation suffered by the transmitted signals, due to the propagation channel, can be achieved with an error less than 0.6◦. It is also shown that the dynamic response of the system can be optimized by properly selecting the operation point of all oscillators.

Millimeter Wave Subharmonic Mixer Implementation Using Graphene Film Coating

In this work, a subharmonic frequency mixer for millimeter wave applications has been designed. The mixing and multiplication phenomena are simultaneously achieved via a nonlinear component consisting in a microstrip line gap covered by a graphene fllm coating. The circuit structure is made up of various fllters, which have been optimized to ensure high port-to-port isolation. The nonlinear behavior of the subharmonic frequency mixer has been experimentally evaluated within the 39{40.5GHz RF frequency band. The frequency downconversion is achieved by mixing the RF signal with the second harmonic component of a 17.9GHz LO signal. Conversion losses are minimized by generating a return path for IF, through the use of a quarter wavelength open-ended stub.

Non Linear Optimization Technique for the Reduction of the Frequency Scanning Effect in a Phased Array Based on Broadband Injection-Locked Third Harmonic Self-Oscillating Mixers

In this work, an electronically tunable large range phase shifter based on a broadband Injection-Locked Third Harmonic Self- Oscillating Mixer (IL3HSOM) is designed and analyzed. This multi- functional circuit generates a down-converted Intermediate Frequency (IF) signal and provides a theoretical 540 - continuous phase shift range. The conversion gain and the bandwidth of the circuit are optimized through bifurcation control techniques. The IL3HSOM will be used as the core of a broadband phased antenna array with electronic beam-steering capabilities. The use of a multi-harmonic load based on an arbitrarily width modulated transmission line allows the nonlinear optimization of the circuit phase shift frequency response to compensate the frequency scanning efiect, which negatively in∞uences the performance of broadband antenna arrays.

New Non-Linear Approach for the Evaluation of the Linearity of High Gain Harmonic Self Oscillating Mixers

In this work, the linearity of a high gain Harmonic Self Oscillating Mixer (HSOM) is analyzed. In order to obtain high conversion gain, the working point of the HSOM is established close to a Hopf bifurcation point. The traditional flgures of merit used to characterize the linearity of conventional mixers cannot be directly applied to characterize the behavior of autonomous circuits, because of the in∞uence of the input RF signal power on the autonomous signal parameters. The 1dB compression point and the third order distortion will be analyzed as a function of the harmonic content and maximum gain of the circuit. From the collected data, the optimum harmonic content and the maximum conversion gain of the HSOM can be selected, for a particular application, in order to minimize the output IF signal distortion. Modern microwave communication systems, and specially wireless and portable implementations, have to comply with strict requirements about size, weight, power comsumption and cost. These goals can be achieved by using multi-functional circuits, which enable the implementation of several blocks of the communication system using a reduced number of components. From this point of view, the Harmonic Self Oscillating Mixer (HSOM) is a multi-functional circuit which results an attractive option to be used in front-end stages of microwave

ANALYSIS OF THE PERFORMANCE OF INJECTION LOCKED OSCILLATORS IN A DATA TRANSMITTING POLARISATION AGILE ANTENNA APPLICATION

In this work, a polarisation agile antenna based on an array of two injection locked oscillators is presented. The proposed topology provides a theoretical relative phase shift range of 360degrees between the output signals, which can be easily controlled through two DC voltages. The behaviour of the system is studied, both through simulations and measurements of the manufactured prototype, focusing on the joint performance of the oscillators. The data transmission capabilities of the system are analysed, proposing a solution for phase modulated signals.