Papers by Alejandro Rivera-lavado
2023 IEEE/MTT-S International Microwave Symposium - IMS 2023
Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XVI
2016 Global Symposium on Millimeter Waves (GSMM) & ESA Workshop on Millimetre-Wave Technology and Applications, 2016
Phase shifting in a dielectric rod waveguide, loaded with a carbon nanotube layer illuminated wit... more Phase shifting in a dielectric rod waveguide, loaded with a carbon nanotube layer illuminated with light from a tungsten lamp, was studied experimentally at the frequency range of 75-110 GHz. Close to a linear dependence of phase shift on the optical power intensity with almost independent behavior of the losses is observed The phase shift of 30 degrees with less than 1 dB extra loss for 1.26 mW/mm2 light intensity was achieved.
IEEE Transactions on Terahertz Science and Technology
Radiofrequency (RF) probes based on 50-Ω planar transmission lines play a key role in almost ever... more Radiofrequency (RF) probes based on 50-Ω planar transmission lines play a key role in almost every stage of RF device development, establishing the physical contact between high-end instrumentation and the device. With the continuous downscaling of semiconductor technologies to reach into the millimeter-wave (30 GHz to 300 GHz) and Terahertz (300 GHz to 3 THz) bands and devices exhibiting broader frequency response, current RF probe technology is the Achilles heel for precise and repeatable measurements. Here we propose a novel RF probe technology based on near-field coupling of single-mode dielectric waveguide structures which according to our full-wave simulations provide an extremely broad frequency range covering from 0 Hz up to 340 GHz, the largest continuous bandwidth reported to date. A concept demonstrator using this approach shows contactless RF probing on test structures which show the path towards continuous measurements across the microwave, millimeter-wave and Terahertz range.
Optical Fiber Communication Conference (OFC) 2022
A terahertz data link is presented using dielectric rod waveguide (DRW) at 300 GHz and complex mo... more A terahertz data link is presented using dielectric rod waveguide (DRW) at 300 GHz and complex modulations for speeds up to 120 Gbps. Performance comparison with WR-3 rectangular waveguide validates the low-dispersion behaviour of DRW.
2013 7th European Conference on Antennas and Propagation, 2013
We discuss two different approaches to overcome the power limitations of CW THz generation impose... more We discuss two different approaches to overcome the power limitations of CW THz generation imposed to conventional photomixers. The increase in power achievable by using arrays of AEs is studied. Then "large area emitters" are proposed as an alternate approach to overcome the power limitations. In this antenna-free new scheme of photomixing, the THz radiation originates directly from the acceleration of photoinduced charge carriers generated within a large semiconductor area. The quasi-continuous distribution of emitting elements corresponds to a high-density array and results in particularly favorable radiation profiles. I.
Sensors
The use of a low-cost split-ring resonator (SRR) passive sensor for the real-time permittivity ch... more The use of a low-cost split-ring resonator (SRR) passive sensor for the real-time permittivity characterization of hydrocarbon fluids is proposed in this paper. The characterization of the sensor is performed through both full-wave simulation and measurements. Thanks to the analysis of several crude samples, the possibility of discrimination between different types of crude and the estimation of several of their properties are demonstrated. Between them, the estimation of sulfur, aromatic hydrocarbons, and salt-water concentrations either in normal ambient conditions or in a high-pressure and high-temperature environment can be mentioned. Experiments were run both at normal ambient conditions and pressures up to 970 bar and temperatures up to 200 °C.
Sensors, 2022
In this work, the design of an integrated 183GHz radiometer frontend for earth observation applic... more In this work, the design of an integrated 183GHz radiometer frontend for earth observation applications on satellites is presented. By means of the efficient electro-optic modulation of a laser pump with the observed millimeter-wave signal followed by the detection of the generated optical sideband, a room-temperature low-noise receiver frontend alternative to conventional Low Noise Amplifiers (LNAs) or Schottky mixers is proposed. Efficient millimeter-wave to 1550 nm upconversion is realized via a nonlinear optical process in a triply resonant high-Q Lithium Niobate (LN) Whispering Gallery Mode (WGM) resonator. By engineering a micromachined millimeter-wave cavity that maximizes the overlap with the optical modes while guaranteeing phase matching, the system has a predicted normalized photon-conversion efficiency ≈10−1 per mW pump power, surpassing the state-of-the-art by around three orders of magnitude at millimeter-wave frequencies. A piezo-driven millimeter-wave tuning mechanis...
Springer Series in Optical Sciences, 2021
The 8th European Conference on Antennas and Propagation (EuCAP 2014), 2014
In this contribution, the use of Dielectric Rod Waveguide antennas integrated with a THz photomix... more In this contribution, the use of Dielectric Rod Waveguide antennas integrated with a THz photomixer-based emitter is studied. This topology presents a cost-affordable alternative to dielectric lenses for reducing losses caused by scattering into the substrate and reflection in the semiconductor-air interface. For increasing the bandwidth, the use of planar dielectric lens embedded into the rod is proposed.
The 8th European Conference on Antennas and Propagation (EuCAP 2014), 2014
A dielectric rod waveguide (DRW) made of high-dielectric-constant material such as sapphire, GaAs... more A dielectric rod waveguide (DRW) made of high-dielectric-constant material such as sapphire, GaAs or Si has in the past been shown to have low transmission loss and good matching with a rectangular metal waveguide at millimetre wavelengths. Also various passive components have been demonstrated. Recently, it has been demonstrated that a single DRW antenna works well over several rectangular waveguide bands even up to 1 THz. Also first attempts have been made to integrate a photo mixer with a DRW waveguide to produce an effective THz source.
2013 38th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013
ABSTRACT In this manuscript, we present a new antenna topology applied to the so called THz gap, ... more ABSTRACT In this manuscript, we present a new antenna topology applied to the so called THz gap, based on using a dielectric rod antenna avoiding the use of the classical lens for collimating the emitted/received power. The scope and future perspective of the manuscript is beyond this idea: we develop this topology with the perspective of being the optimum antenna system to be coupled in a THz waveguide easy manufactured and with extremely low propagation losses, as we present here.
Arrays of coherently driven photomixers with antenna (antenna emitter arrays, AEAs) have been eva... more Arrays of coherently driven photomixers with antenna (antenna emitter arrays, AEAs) have been evaluated as a possibility to overcome the power limitations of individual conventional photomixers with antenna ("antenna emitters", AEs) for the generation of continuous-wave (CW) THz radiation. In this paper, "large area emitters" (LAEs) are proposed as an alternative approach, and compared with AEAs. In this antenna-free new scheme of photomixing, the THz radiation originates directly from the acceleration of photo-induced charge carriers generated within a large semiconductor area. The quasi-continuous distribution of emitting elements corresponds to a high-density array and results in favorable radiation profiles without side lobes. Moreover, the achievable THz power is expected to outnumber even large AEAs. Last not least, the technological challenge of fabricating LAEs appears to be significantly less demanding.
2018 IEEE MTT-S Latin America Microwave Conference (LAMC 2018), 2018
In this paper, the design of the passive network of a Single Balanced Mixer at 92 GHz is presente... more In this paper, the design of the passive network of a Single Balanced Mixer at 92 GHz is presented. It has been developed using GCPW technology working in the range of 84–96 GHz, having an IF frequency of 2 GHz. This mixer is considered as a part of the receiver system using WR-10 standard port as RF port (transition design also included), which enables an easy connection of a horn antenna. ACST gmbh diode 3DSF5 Zero-Bias Diode, suitable for a input power between −10dBm and 2dBm without DC bias, has been chosen in order to work with a low power photonic local oscillator. In cases were there are severe constrains in terms of power, this configuration offers an alternative solution to commercial mixers.
The revolution that wireless communication is suffering during the last decades has increased the... more The revolution that wireless communication is suffering during the last decades has increased the need of antennas where performances such as lightweight, rapid manufacturing and portability run in parallel with their electric performance. The maker revolution in which 3D printers can help manufacturing customized, high performance, lightweight and rapid manufacturing antennas is a fact to be explored. This paper discusses the design, simulation and 3D printing of an offaxis reflector antenna. The proposed design is composed of a parabolic reflector and an X band circular horn antenna as a feed. By adding a dielectric rod waveguide (DRW) to the feed, a rotationally symmetric radiation patter, similar to the one with a corrugated horn, is achieved.
A new topology that potentially can open new solutions for covering the new VLBI2010 configuratio... more A new topology that potentially can open new solutions for covering the new VLBI2010 configuration and its frequency bands associated is presented in this manuscript. In this approach a single band from 2 to 14 GHz is considered. A log-spiral antenna is printed on a conic surface. The whole structure is adjusted in order to obtain a pure circular polarization at broadside direction. An array of four elements is proposed for obtaining a dual-polarization feeder.
El objetivo de esta tesis es el diseno y construccion de generadores de senal de terahercios basa... more El objetivo de esta tesis es el diseno y construccion de generadores de senal de terahercios basados en fotomezcladores de bajo coste y que funcionen a temperatura ambiente. Como se explica en la introduccion, existen muchas aplicaciones potenciales a frecuencias comprendidas entre los 100 GHz y 1.000 GHz. Propuestas en el campo de la seguridad, radioastronomia y medicina, entre otros, han sido consideradas y evaluadas. Algunas de ellas han comenzado a ser explotadas comercialmente, por ejemplo, en la deteccion de armas y explosivos ocultos en puestos de control y seguridad. No obstante, todavia existe un nicho, el de la electronica de consumo (comunicaciones, entretenimiento, etc), en el que las frecuencias de esta banda no son utilizadas por su alto coste. En una primera parte, se analizan distintos tipos de antenas planares que son especialmente atractivas para ser integradas con dispositivos fotomezcladores generadores de terahercios. El efecto de los sustratos semiconductores e...
2018 25th International Conference on Telecommunications (ICT), 2018
We report on the development of a compact quasioptical zero-bias Schottky barrier diode (QO-SBD) ... more We report on the development of a compact quasioptical zero-bias Schottky barrier diode (QO-SBD) envelope detector for mmWave/sub-THz frequencies. The detector consists of a Schottky diode mounted on a self-complementary bowtie antenna mounted over a hyper-hemispherical silicon lens. The device is optimised to be used for multi-Gbps wireless communication systems. To increase the video bandwidth of the receiver, a wideband impedance matching network is designed and integrated. Measurements show that a 3-dB video bandwidth of 10GHz is realised for the proposed receiver, which is the highest value achieved for a wide-band QO-type detector.
2017 11th European Conference on Antennas and Propagation (EUCAP), 2017
This manuscript proposes a high-power terahertz source that consists on a large amount of coheren... more This manuscript proposes a high-power terahertz source that consists on a large amount of coherently driven photomixing THz sources. Each element is placed in the gap of a bow tie antenna. The resulting array defines a chessboard-like layout which maximize the density of devices. This novel concept is validated through full-wave simulations. Experimental considerations are also provided for a prototype manufactured for the 1550 nm window. Measured power level will be shown at the conference.
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Papers by Alejandro Rivera-lavado