Antti. Raisanen

Aalto University · Department of Electronics and Nanoengineering

In this manuscript, the use of dielectric rod waveguide antenna (DRW) with an embedded planar lens is proposed as a highly directional alternative to an electrically large hyper-hemispheric silicon lens for emission at millimeter and sub-millimeter wave frequencies. DRW antennas radiate properly if only the fundamental mode is excited to the struct...

Testing of electrically large, high-gain antennas as well as that of small integrated antennas at millimeter and submillimeter wavelengths is extremely challenging. Basically, there are three methods for measuring radiation properties of an antenna: the far-field method, the near-field method, and the compact antenna test range (CATR). In case of l...

In this manuscript, the use of dielectric rod waveguide (DRW) antennas in the millimeter and sub-millimeter wave range is presented as a solution for covering two issues: getting more radiated power and filling a technological gap problem in the terahertz band, namely a fully electronic beam steering. A 4x4 element array working at 100 GHz fed by a...

A new method recently developed for planar nearfield broadband phaseless antenna measurement is adapted to work with a reduced set of points. The method is an extrapolation of the conventional off-axis holography in which a frequency sweep is made at each point of the acquisition grid, and the phase is retrieved simultaneously for all the frequenci...

A novel scheme for planar near-field phaseless antenna measurement based on off-axis holography is presented. Separation of the image terms of the hologram is artificially increased by multiplexing the measurements of two sub-sampled holograms generated with two 180° phase-shifted reference waves. Combination of both sub-sampled holograms produces...

A new efficient method for broadband antenna characterization from phaseless acquisitions in the frequency domain is presented. The phase-retrieval technique is based on an extrapolation of the off-axis indirect holography. In common with the conventional approach, the power of the interferometric field of the antenna under test and a reference ant...

The theoretical background of antenna theory, especially in relation to terahertz applications, is presented in this chapter. A general discussion of the issues of THz antennas, especially when matching the photomixer is presented. Array theory is presented, together with an exhaustive and precise analysis of one of the most promising new solutions...

In this chapter we first briefly introduce Maxwell's equations and derive the Helmholtz equation, a special case of the wave equation, and introduce its different solutions for fields that may propagate in THz waveguides. The second section describes different waveguides operating at THz frequencies. The third section is devoted to the beam wavegui...

In this letter, the design and measurement results of a millimeter-wave beam switching antenna are presented. Several antenna prototypes have been fabricated and measured in planar and conformal installations. The developed prototype consists of three antenna arrays of 16 patch elements in each array and it is operating at 61 GHz with linear polari...

We propose a dielectric rod waveguide antenna (DRW) integrated with a photomixer as a THz emitter. This represents a different approach as opposed to the classical solution of a substrate lens. Main goals are an inexpensive alternative to substrate lenses, reduction of both reflections on the semiconductor-air interface and scattering of terahertz-...

In this paper, we study the influence of the radius of a cylindrical supporting structure on radiation properties of a conformal millimeter-wave antenna array. Bent antenna array structures on cylindrical surfaces may have important applications in future mobile devices. Small radii may be needed if the antenna is printed on the edges of mobile dev...

Microelectromechanical system (MEMS) varactors based on a freestanding layer of single-walled carbon nanotube (SWCNT) films were designed, fabricated and tested. The freestanding SWCNT film was employed as a movable upper patch in the parallel plate capacitor of the MEMS. The measurements of the SWCNT varactors show very high tunability, nearly 100...

Whispering gallery mode (WGM) resonators have high Q factors and small modal volumes and can thus show strong non-linear interactions. Most of the interesting non-linear materials are crystalline and feature high refractive indices such that efficient coupling to the resonator is challenging. We present a study on high refractive index WGM resonato...

This paper describes a wideband hologram-based CATR: which can be realized by linearly adjusting the feed location. The position needs to be adjusted for approximately compensating the wave front curve of the feed, which is proportional to the operating frequency. The theory can be conformed under the paraxial condition. For the acceptable quiet-zo...

A recently proposed antenna measurement technique based on impedance or reflection coefficient measurements with varying reflective objects in front of an antenna is reviewed. The method allows radiation pattern determination without moving cables which are subject to changes in their electrical length and attenuation during conventional antenna me...

The results from our efforts to characterize propagation constant of carbon nanotube, graphene and silver nanowire layers in the frequency range of 75 to 110 GHz are presented. The method is based on measurements of propagation characteristics of a dielectric rod waveguide unloaded and loaded with the layers under study. The losses caused by carbon...

The concept of a reconfigurable patch antenna array is presented in this article. Configurability is achieved using liquid metal alloy which fills necessary milled channels in the antenna structure. A single patch antenna and three patch antenna array are simulated and measured in this work. Matching and radiation properties in the frequency range...

This paper presents an alternative characterization method to the traditional characterization methods of the millimeter-wave and terahertz Schottky diodes. The diodes can be characterized based on the mixer operation (conversion loss and noise temperature) under comparable conditions. The tuning of the embedding impedances and the easy changing of...

The design of a dielectric rod waveguide (DRW) antenna for frequencies of 75–325 GHz is presented. The optimal broadband antenna geometry is determined using numerical simulations . A single DRW antenna is matched with metal waveguides of different sizes for different frequency bands. Measurement results agree very well with the simulation results...

Coherent detection of very weak THz signals is important in astronomy, spectroscopy, and communications. We report on coherent up-conversion of THz radiation into the optical telecommunication range. All resonant phase-matched conversion can be achieved in a whispering gallery mode (WGM) resonator. Furthermore we present first results on WGM resona...

Bloch analysis in conjunction with a full-wave simulation is used in order to design a composite right/left-handed (CRLH) transmission line (TL). We analyze the parasitic components introduced by loading elements and inter-cell coupling, and present details to the compensation required in order to maintain the balanced state of the periodic TL. The...

This paper presents a new method for antenna pattern retrieval from reflec-tion coefficient measurements. A reflective load with known reflective properties is placed close to the aperture of the antenna under test. The reflection coefficient of the antenna is measured at the antenna feed with multiple different reflective loads. The antenna patter...

This paper presents a new method for antenna pattern retrieval from reflec-tion coefficient measurements. A reflective load with known reflective properties is placed close to the aperture of the antenna under test. The reflection coefficient of the antenna is measured at the antenna feed with multiple different reflective loads. The antenna patter...

We present design and simulations of a reconfigurable reflectarray suitable for use as a sub-reflector within a confocal millimeter-wave imaging system. The performance of various reflectarray designs for use within a confocal imaging system are evaluated, e.g. phase quantization, feeding field. A quantized-particle-swarm optimization algorithm is...

Flat dielectric lens antennas for millimetre-wave beam-steering with fan-beam are studied in this paper. Two different configurations are studied: a dielectric slab waveguide (DSW) lens and a parallel plate waveguide (PPW) lens. Both lenses are made of PREPERM L450 commercial plastic developed for high frequency antenna applications. Two prototype...

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...

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 o...

This paper presents a new method for thermal characterization of THz Schottky diodes. The method is based on the transient current behavior, and it enables the extraction of thermal resistances, thermal time-constants, and peak junction temperatures of THz Schottky diodes. Many typical challenges in thermal characterization of small-area diode devi...

We have studied beam-steering radio in the E-band., e.g. for high-capacity communication links. Lens antennas provide high gain and are suitable for integration at millimeter wave frequencies, e.g., for beam-switching a planar antenna array with a switching network may be integrated to the surface of the lens; one patch is activated at a time for e...

In this paper we present simulation and measurement results of a patch antenna, working at mm-wave frequencies, printed with inkjet technology on a flexible polyethelene naphtalate (PEN) substrate. Different ground planes are investigated due to the reason that antenna can be placed on different objects with different materials. Antenna was placed...

In this paper, we present design and experimental results on reflectarrays at 120 GHz. The offset-fed reflectarrays consist of conductor-backed coplanar patch antennas with phase-shifting stubs. Three 138-mm reflectarrays are lithographically fabricated and evaluated in a near-field measurement range. Their measured beam patterns are compared to th...

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...

The aim of this work is to study dielectric properties of thin carbon nanotube and silver nanowire layers at 75-110 GHz frequency range. The method is based on S-parameter measurements of loaded and unloaded sapphire rod waveguides.

We present results of experimental characterization of static 650-GHz reflectarrays. The reflectarrays are based on 123-μm circular microstrip patch antennas with tuning stubs as phase shifters. The static reflectarrays are considered as predecessors for active reflectarrays, and therefore the reflectarray elements have two discrete phase-shift val...

The design and optimization process of reconfigurable reflectarray element with MEMS-based phase shifter at 120 GHz is presented. The dielectric properties of SU-8 substrate are characterized with on-wafer measurements. Several design parameters which affect the element efficiency are studied. Through proper design and optimization of the array ele...

The performance of mobile terminal antennas in the case of a non-planar ground plane is studied. The effects of bending are analysed using computer simulations and a resonator-based equivalent circuit model for improving the understanding of the phenomenon. Results show that bending the ground plane can have a considerable effect on the operation a...

An integrated lens antenna design for beam-steering with small scan loss is presented. The lens is based on a well known extended hemispherical lens. By placing the feed elements on a spherical bottom surface of the lens, instead of a conventional planar one, all of the feed antennas are oriented towards the collimating part of the lens. The presen...

The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio tele...

Two different approaches for implementing the LO for a radioastronomy receiver for pumping signal up to 1 THz are presented. The devices are based on photoconductive mixers. An array of 7 pixels is presented and studied. Two different antenna topologies are presented for increasing the power emitted. One is based on the concept of the matching conj...

In this work, the design of a millimeter-wave conformal antenna array for cylindrical structure is developed. Antenna array consists of 4×4 elements and operates at 60 GHz. Different substrates and their properties are considered. Fiber Teflon substrate was chosen for the antenna structure due to its good flexibility properties and low losses. The...

In this paper the possibility of using a single dielectric rod waveguide antenna at 75 - 1100 GHz frequency is presented. The simulations of the antenna showed that DRW antenna can be well matched with standard metal waveguides. The radiation pattern of the antenna has the same shape in whole frequency range.

Imaging at submillimetre-wave frequencies is of considerable interest thanks to potentially superior performance at longer stand-off ranges in comparison to mm-wave imaging thanks to improved angular resolution. In this paper we discuss the performance of multispectral passive imaging system centred around 250, 400 and 750 GHz. Multi-band imagery i...

The aim of this work is to study dielectric properties of thin carbon nanotube layers at 75-110 GHz frequency range with S-parameter measurements of loaded sapphire rod waveguides. The results are compared with DC resistivity, high frequency resistivity, optical transparency and free-space transmission of MMW radiation through the layers.

In this paper, a calibration method of a near-field measurement for reflectarray characterization is presented. First, a waveguide calibration is performed to eliminate the influence of the directional coupler used in the measurement scheme. Second, the reflection measurement is modelled with a metal plate drawn away from the probe aperture. With t...

In this paper, a verification routine is developed for validating extremely fast pulsed I-V and transient current measurement setups. The measurements performed for the routine include pulsed I-V measurement with different pulse widths (using several voltage and current levels) as well as transient current measurement using different heating and me...

The conventional integrated lens antennas (ILAs) for beam steering suffer from internal reflections that deteriorate the scanning properties. The internal reflections are known to affect side lobes, cross-polarisation level, input impedance of the feed, and mutual coupling. In this paper, ILAs are designed to exhibit very low reflection loss, i.e.,...

Imaging at submillimetre-wave (SMMW) frequencies is of considerable interest for security applications due to potentially superior performance at longer stand-off ranges in comparison to mm-wave imaging thanks to reduced diffraction. We have demonstrated passive broad-band video rate imaging system operating at a centre frequency of about 600 GHz,...

This paper presents a novel type of RF power sensor, based on a metallic structure integrated into an mm-wave range dielectric rod waveguide made of Si. The metallic structure is employed as a bolometer. Numerical simulations of temperature distribution are shown. A prototype was tested at frequencies of 45 GHz-1 THz and a power levels from 0.1 to...

The reflection properties of the MEMS-based HIS illuminated from oblique angles of incidence have been characterized numerically, and a quasi-optical measurement setup has been built for experimental characterization. The resonance frequency and the relative bandwidth are slightly increasing with the increase of the angle of incidence. The comparis...

This paper describes the main results of the EU FP7 project TUMESA - MEMS tuneable metamaterials for smart wireless applications. In this project, we studied several reconfigurable antenna approaches that combine the new technology of MEMS with the new concept of artificial electromagnetic materials and surfaces (metamaterials and metasurfaces) for...

In this paper, we describe the near-field measurements of the surface of a 120 GHz reflectarray. The reconfigurable offset-fed reflectarray under development consist of approximately 3700 coplanar patch antenna elements which are individually controlled by 4-state micro-electro-mechanical (MEMS) phase shifters. Measurements of a static reflectarray...

This paper discusses the prospects of millimeter-wave beam steering antennas, such as tuneable high-impedance surface, dielectric rod waveguide with an integrated phase shifter, tuneable leaky-wave antenna, active reflectarray, and shaped lens antenna with an integrated switched feed array. In these antennas the necessary phase change for antenna e...

Both active and passive submillimetre-wave stand-off imaging systems are under development for security imaging applications. The drivers for operation at higher frequencies have been the desire for better image resolution, smaller optics package, reduced susceptibility to specular reflections from the human skin and capability for stand-off imager...

A method has been introduced for the phase-retrieval step in the field of holographic imaging. In contrary to the phase-retrieval methods available in the literature which are mainly implemented in the wave-number domain the method introduced here retrieves the phase directly in the spatial domain. Although, the method is applicable to holographic...

This paper presents a fast and easy to use method to determine permittivity and loss tangent in the frequency range of 75 to 325 GHz. To obtain the permittiv-ity and the loss tangent of the test material, the reflection and transmission S-parameters of a waveguide section filled with the test material are measured using a vector network analyzer an...

Development of a 120-GHz FMCW radar with a reflectarray as focusing element is described. The reflectarray is realized on a 150-mm silicon wafer and it has 3700 phase-modulating elements on it. The phase shifters have four discrete values to cover full phase modulation with 90° steps. The reflectarray element is realized with a conductor-backed cop...

In many emerging applications of millimeter waves, electronic focusing and beam steering is needed. We present a survey of mm-wave beam steering antennas, where the necessary phase change for antenna elements is achieved using various electronically tuneable elements, e.g. microelectromechanical systems (MEMS), such as tuneable leaky-wave antennas,...

Three-pole iris-based bandpass filters are proposed as waveguide phase shifters for automotive applications at 77 GHz. Compared to standard configurations with symmetrical irises, asymmetrical designs have been preferred here in order to minimize technological constraints in the perspective of designing beam steering transmit-array antennas. Here t...

This article presents an integrated lens antenna design that allows two-dimensional beam-steering with a non-symmetrical beam. The lens design is based on a traditional integrated lens concept. It is shown that, with a simple modification, the beam-shape can be changed without compromising the beam-steering properties. The limitations and propertie...

In this article a dielectric rod waveguide antenna for 220-325 GHz is presented. Simulations for determining antenna optimal geometry are performed. Measurement results of the radiation pattern are shown and compared with the simulation results at 310 GHz. Matching of the antenna with a metallic waveguide is experimentally studied.

Paper presents the design and fabrication steps as well as measurement results for a fixed-tuned full-waveguide band Schottky frequency doubler. The doubler consists of a GaAs MMIC chip embedded in a waveguide channel. The chip is fabricated using a commercial MMIC foundry process and two post-processing options, substrate thinning and etching arou...

In this paper, we describe the development of a millimeter-wave reflectarray intended for use in a millimeter-wave identification or imaging applications. Design, simulations, and millimeter-wave near-field measurements of the reflectarray are presented. An in-house genetic algorithm is used in determining the required phase shift by the reflectarr...

Design and measurement results of a beam-steering integrated lens antenna at 77 GHz are presented. An 8-element LTCC aperture coupled patch antenna feed array with a switching network is used to electrically steer the main beam in H-plane. A 100-mm diameter Rexolite (ε r = 2.53) lens is simulated and tested. The eccentricity of the lens is optimize...

Beam steering with a MEMS-based high impedance surface has been studied in W band. The steering mechanism is based on the principle of a phase gradient array. Reflection phase properties of a single unit cell structure are analyzed. Radiation pattern of a strip consisting of elements with different impedance is analyzed numerically for two beams of...

This paper presents an overview on novel microwave micro-electromechanical systems (MEMS) device concepts developed in our research group during the last 5 years, which are specifically designed for addressing some fundamental problems for reliable device operation and robustness to process parameter variation. In contrast to conventional solutions...

Millimeter-wave phase shifters are important components for a wide scope of applications. An analog-type phase shifter for W-band has been designed, analyzed, fabricated, and measured. The phase shifter consists of a reconfigurable high-impedance surface (HIS) controlled by micro-electromechanical system (MEMS) varactors and placed adjacent to a si...

A new method for extracting the series resistance and thermal resistance of a Schottky diode is presented. The method avoids the inaccuracies caused by the temperature dependence of the saturation current and ideality factor. These are a major concern for traditional extraction methods, especially when the diode under test has a submicrometer anode...

A study of the phase center position of dielectric rod waveguide (DRW) antennas (silicon and sapphire) for different millimeter-wave (mm-wave) frequencies is presented in this document. Phase center position is determined using data obtained by planar scanning and analyzed by means of different methods: least squares fit method with and without wei...

MEMS varactors and switchers used as a key element for the phase shifters on dielectric rod waveguides are presented. The 32 degree phase shift due to capacity change in MEMS is demonstrated in W band. New approach of the reconfigurable phase shifter with MEMS switchers is discussed in this work.

A cavity-backed antenna element is introduced and investigated for the antenna-in-package applications at 60GHz frequency band. A thin-film Silicon-based technology is used to implement the antenna element and two different configurations for 1x4 arrays of the same element. The feeding networks of the arrays are designed in such a manner that one o...

form only given, as follows. A cavity-backed antenna element is introduced and investigated for the antenna-in-package applications at 60 GHz frequency band. A thin-film silicon-based technology is used to implement the antenna element and two different configurations for 1×4 arrays of the same element. The feeding networks of the arrays are design...

This paper describes the scope and on-going activities of the ESF Research Networking Program entitled “New frontiers in mm / sub-mm waves integrated dielectric focusing systems�