M. Fernandez

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.

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.

Frequency Scanning Array Composed of Antipodal Linearly Tapered Slot Antennas

In this work, a frequency scanning array of antipodal linearly tapered slot antennas is presented. The system is capable of performing beam steering from –11 to 10 degrees while sweeping the frequency from 8.25 GHz to 11.5 GHz. The beam scanning is achieved by means of a specially designed feeding network that divides the power and introduces the proper phase shift for each antenna port in the frequency range of interest. Experimental results showing the full array behaviour are also presented.

Frequency scanning slotted waveguide in the sub-millimeter wave band

In this work, a waveguide slotted antenna array working in the sub-millimeter wave band is presented. The antenna performs beam tilting from 68 to 89 degrees in the H-plane while sweeping the frequency from 240 GHz to 310 GHz. Sixteen rectangular slots have been cut in the wide surface of a standard WR-3 brass metal rectangular waveguide to obtain the desired behavior. The antenna has been fabricated combining laser and mechanical prototyping machinery. Experimental results showing the main waveguide slotted antenna array characteristics are also presented.

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.

Millimetre wave textile integrated waveguide beamforming antenna for radar applications

In this work, a fully Textile Integrated Waveguide (TIW) beamforming antenna for its use in a radar system operating at 77 GHz is presented. The TIW beamforming antenna is based on a Substrate Integrated Waveguide (SIW) slot antenna array and it is designed to be manufactured completely with conductive and non-conductive threads using industrial textile machinery, avoiding subsequent sewing and adhesive processes for its integration in wearable or comformable systems. The antenna performs beam tilting from 11 to 23 degrees in the H-plane while sweeping the frequency from 70 GHz to 77 GHz. Firstly, a design of the equivalent SIW beamforming antenna structure is simulated and optimized and then, the translation into a fully woven TIW beamforming antenna structure is presented. The proposed TIW beamforming antenna design is provided with a TIW to WR10 standard rectangular waveguide transition for its experimental validation.