[lic] Sähkötekniikan korkeakoulu / ELEC

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    Harmiton sähköisku vai pikainen kuolema
    (Aalto-yliopisto, 2024) Mäkinen, Markku; Kimmo Lehtonen; Sähkötekniikan ja automaation laitos; Department of Electrical Engineering and Automation; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Matti Lehtonen
    This licentiate thesis investigates occurred electric accidents in Finland during 1882–1932. Research covering this topic during the first 50 years of electrification in Finland has not been done previously. The central empirical material consisted of news on electric accidents published in national newspapers. This information was extended and enlarged by statistics, articles in technical journals, textbooks and references in printed items. The references gave qualitative and quantitative information. Qualitative analysis, close reading was the central method. The authors own experience and insights of the re-search topic was used as guiding theory. The total number of electric accidents was registered as well as the number of accidents among laymen and pro-fessionals. In addition, the month and the geographical location of the accidents were registered. The causes and consequences of the accidents were investigated in the qualitative analysis of the material. The most common causes of the accidents among laymen and professionals were analyzed. In the theoretical part of the thesis the concepts of electric safety and electrical work safety were investigated as well as the growing orientation towards electrical injuries and the effects of electricity on human physiology with-in medical sciences. The results indicate that electric accidents were well covered and reported in the newspapers. The majority of accidents happened on the countryside, to laymen and men. The number of accidents among laymen was nearly the double compared to that of the professionals. No electric accidents were however reported during the first decades. This can be explained by the fact that extra low voltage DC-systems were used for lighting, electrical equipment were rare and pluggable equipment were not yet available. Among the professionals the intended or unintended working in bare live part or too close to it dominated as the cause of accidents. Electrical safety as we understand it today was in many ways an unknown concept theoretical-ly as well as regarding tools, equipment, devices and working procedures. The number of electrical accidents increased considerably in the 1910s. This was caused by the electrification of Finland´s country districts and in many ways unsafe electrical installations. In addition, the laymen´s insight of the dangers of electricity was very poor. Several accidents happened because of pure playing. This thesis produces new information on the total number of electric accidents in Finland. Earlier studies have investigated the number of fatal electric accidents starting from year 1930. This study adds the information re-garding the previous 50 years. A total picture of fatal electric accidents during 1882–2022 is thus reached. In addi-tion, new information about non-fatal accidents was documented. The results can be applied and considered in future research regarding for example the electrical safety act and the statutes and guidelines given by the authorities.
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    Application Layer Network Address Translation
    (Aalto-yliopisto, 2022) Tilli, Juha-Matti; Kantola, Raimo; Tietoliikenne- ja tietoverkkotekniikan laitos; Department of Communications and Networking; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Kantola, Raimo
    The most important issues facing the Internet are lack of security and address space exhaustion. Flooding attacks are easy today due to for example the design of transmission control protocol (TCP). QUIC may offer some remedy for new applications but it is unlikely to replace TCP in all legacy applications. Most modern TCP endpoints have support for SYN cookies, but middle-points like firewalls may not be able to protect themselves. Address space of Internet protocol version 4 (IPv4) is not sufficient to give even one address to every Internet user today. At the same time, Internet of Things (IoT) is gaining foothold, meaning the device count is expected to exceed Internet user count by orders of magnitude. To counter these problems, network address translation (NAT) has emerged as a solution. However, NAT has poor characteristics when used on the server side. In this thesis, SYN cookies and their middle-point implementations within SYN proxy are refined compared to the state of the art. One result of the thesis is a multithreaded user space TCP SYN proxy that is able to protect servers and legacy firewalls against SYN flooding attacks. It is also able to act as the protecting component of a novel firewall called Realm Gateway (RGW) that uses standard domain name system (DNS) queries for NAT traversal. Additionally, an application layer NAT (AL-NAT) technique allowing NAT traversal for protocols where the client sends the first message containing host name of the server is defined and implemented. As a lightweight implementation of AL-NAT, a component supporting AL-NAT without security policy is provided. Finally, for protocols such as secure shell (SSH) that are incompatible with AL-NAT, carrier grade TCP proxy (CG-TP) is implemented to work along with AL-NAT and verified to work with OpenSSH and other applications with similar characteristics.
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    Advanced scanning techniques for field synthesis and near-field antenna measurements
    (2012) Khatun, Afroza; Laitinen, Tommi; Sierra Castaner, Manuel; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Vainikainen, Pertti
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    Integration of low-voltage CMOS analogue-to-digital converters
    (2012) Nieminen, Tero; Åberg, Markku; Mikro- ja nanotekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Halonen, Kari
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    Electrical modeling of large lithium-ion batteries for use in dynamic simulations of electric vehicles
    (2012) Hentunen, Ari; Suomela, Jussi; Sähkötekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Ovaska, Seppo
    During the development of electric vehicles and non-road mobile machinery (NRMM), dynamic system-level simulations are utilized to validate the design and the sizing of components as well as to validate the control software. The model of a battery needs to predict e.g. the open-circuit voltage, terminal voltage, and state-of-charge under various load profiles. Electrical battery models are commonly used, because they are simple and computationally light but still provide good accuracy. Despite the simplicity and low number of parameters, the complex behaviour of electrochemical batteries still makes the parameter extraction a tedious process. This thesis presents a versatile electrical battery model for large lithium-ion (Li-ion) batteries that can be used in dynamic simulations of electric vehicles and NRMM. A set of experiments and a methodology to extract the parameters of the model are described in detail. The parameters are extracted using data from pulse-discharge and pulse-charge experiments, which can be made with a battery cell, module or pack. The presented model can be used for any Li-ion chemistry. The model predicts accurately the state-of-charge, terminal voltage, open-circuit voltage, state-of-health, and power losses for arbitrary discharge and charge current profiles. It also takes temperature, current-rate, calendar-life, and cycle-life effects into account in an easy and intuitive manner. A commercial Li-ion polymer battery with lithium-nickel-manganese-cobalt-oxide cathode and graphite anode is used in the experiments. Model parameters are extracted from the experimental data. The model is validated with independent experiments by using a more realistic hybrid electric NRMM current profile, which is formed from a measured power profile of a real underground mining loader under a typical duty cycle in a test mine. The simulation results show very good agreement with the experiments.
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    Integral equation methods for extreme materials and surfaces
    (2012) Markkanen, Johannes; Ylä-Oijala, Pasi; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Sihvola, Ari
    Various electromagnetic problems can be formulated as boundary value problems for Maxwell's equations m which the solution must satisfy both Maxwell's equations and given boundary conditions. This thesis investigates electromagnetic properties of recently introduced DB and D'B' boundary conditions and their material realizations. The DB boundary condition requires that normal components of the electric and magnetic flux densities vanish at the boundary, and their normal derivatives vanish at the D'B' boundary. Computational methods, based on integral equations, for analysing electromagnetic properties of extreme boundary conditions and their material realizations have been developed. In surface integral equation methods the boundary conditions are enforced by expanding the unknown surface current densities with proper sets of basis functions which satisfy the boundary conditions. The realizations of the DB and D'B' boundaries require extremely anisotropic materials. For analysing highly anisotropic media, a stable volume integral equation method is developed, and applied to study scattering properties of the realizations of the DB and D'B' boundaries.
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    On developments in submillimeter-wavelenght imaging
    (2011) Tamminen, Aleksi; Ala-Laurinaho, Juha; Viikari, Ville; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Räisänen, Antti
    This licentiate thesis covers various technical aspects of sub-millimetre-wavelength (SMMW) imaging. The thesis includes an overview of imaging techniques and lays down parameters for image quality evaluation: point spread function (PSF), resolution, image signal-to-noise ratio (SNR) , and noise-equivalent reflectivity difference (NEΔR). In the literature review, phenomenology of SMMW propagation and interaction with matter as well s different imaging modalities are introduced. Different imaging techniques reported in the literature are compared. In the experimental part of the thesis, image quality of SMMW images is evaluated quantitatively based on the above-mentioned parameters. The images are acquired with a 310-GHz active imaging system based on indirect holographic method and computational back propagation. Advantageously, only amplitude detection is required in the method. The slanted-edge method is applied, and the point spread function of the system is estimated. Imager cross-range resolution is found to be close to theory, 0.18°. The resulting image SNR and NEΔR are evaluated at different SNR of the measurement system -setting requirement for the imaging system receiver SNR. The NEΔR is found to be 0.002 down to a system SNR of 26 dBs Antenna-coupled micro bolometers - used in a passive SMMW imaging system - are characterized at 325-782 GHz at room temperature. The bolometer detectors consist of transition-edge bolometers contacted to an equiangular spiral antenna and coupled to a 2-mm Si substrate lens. The beam width of the bolometer detectors is found to follow an 8.5°/THz -relation. The directional pattern becomes more Gaussian as the frequency is increased towards the high end of the SMMW range. The bolometer-to-bolometer gain difference is found to be 2 dB at maximum. The axial ratio of the bolometer detectors is close to unity. Reflection-and transmission-type phase holograms are used to create a planar wave front, the quiet zone (QZ), at 310 GHz and at 650 GHz. The QZ is measured to have a ripple of ±1.5 dB and ±5° at 310 GHz and ±3 dB and ±25° at 650 GHz, respectively. The holograms are suitable for use in compact antenna test ranges (CATR) or in radar-cross-section (RCS) measurements. The RCS range is used to measure reflectivity of different radar-absorbing materials (RAM) at 310 GHz and at 650 GHz. It is found that every-day materials, such as carpets, can also be used as RAM since they can have reflectivity level comparable to commercial RAM. Finally, infrared detectors are studied for use at SMMW. Pyro electric detectors can have nearly constant response and sensitivity as high as 1500 V/W at the SMMW range is measured.
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    Effect of focus of light and scene contents on perceived restoration, fear, and preference in nightscapes
    (2011) Nikunen, Heli; Korpela, Kalevi; Elektroniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Halonen, Liisa
    Nightscapes have been seen primarily as sources of fear and insecurity. This thesis puts focus on the positive side of environmental experience during night time and explores the role lighting has in this experience. Thesis consists of 3 studies. Studies 1 and 3 examine how changes in the focus of light (focusing lights on urban vs. natural scene contents) affect perceived restoration, fear, and preference during dark hours. Study 2 examines how different scene contents (urban vs. natural) affect these same variables. Simulated views were rated by participants using the Perceived Restorativeness Scale (PRS), the Restoration Outcome Scale (ROS), and measurements of fear and preference. The results of all studies indicate that natural scenes are perceived more restorative, more preferred, and less fearful than urban scenes during the hours of darkness. Changes in the focus of light and in the actual scene contents caused analogous effects. The results are consistent with the daytime findings and suggest that lighting can be used to enhance the perceived restoration and preference and reduce fear of night time environments. Current practice is that lighting is almost solely focused on the most disliked scene contents i.e. roads, car parks and signs that are also the less restorative features of urban environments. This study suggests that this has an effect on the perceived restoration, preference and fear. These factors may have considerable effect on the use of urban spaces during the hours of darkness. This thesis presents that the possibilities to gain positive experiences in nightscapes should receive more attention.
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    Efficient baseband security
    (2011) Ekberg, Jan-Erik; Nyberg, Kaisa; Tietoliikenne- ja tietoverkkotekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Kantola, Raimo
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    Development of a unit level quality system for engineering education
    (2011) Schrey-Niemenmaa, Katriina; Jokinen, Tapani; Sähkötekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Arkkio, Antero
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    Mixer test jig for millimeter wave Schottky diodes
    (2010) Dahlberg, Krista; Mallat, Juha; Louhi, Jyrki; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Räisänen, Antti
    In this Licentiate's thesis, a mixer test jig for millimetre wave Schottky diodes has been designed, fabricated, and tested. With the mixer test jig different Schottky diodes can be tested and compared in the actual operating environment at the nominal design frequency of 183 GHz. The diode under test is mounted on a substrate and radio frequency (RF) and local oscillator (LO) impedance matching is performed with an integrated low-loss EH-tuner. The structure is simple, and the substrate with the diode can be easily changed. The performance of the mixer test jig is tested with a commercial Schottky diode (VDISC2T6). Single sideband (SSB) conversion loss measurement and noise measurement based determination of double sideband (DSB) conversion loss and mixer DSB noise o temperature are carried out. The measured SSB conversion loss at the signal frequency of. 183 GHz is 7.8 dB and at the image frequency of 181.04 GHz it is 8.5 dB with 2.3 mW LO power at 182.02 GHz. The measured SSB conversion loss at the signal frequency is 6.8 dB, when at the intermediate frequency the matching is optimized with an impedance tuner. In the noise-based measurements a diplexer is needed for LO source noise filtering. The measured DSB conversion loss is 4.9 dB and the mixer DSB noise temperature is 780 K with 2.1 mW LO power at 182.6 GHz with the intermediate frequency of 1.05 GHz. The measured SSB conversion losses are comparable to the best published results of fundamental mixers at 183 GHz. The noise measurement results are slightly worse because the instability of the LO source and the need of noise filtering.
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    Characterization of LED luminous flux and photometer spectral responsivity
    (2010) Poikonen, Tuomas Heikki Johannes; Ikonen, Erkki; Signaalinkäsittelyn ja akustiikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Kärhä, Petri
    LEDs are widely used in electronic equipment and different applications of lighting, The optical properties of LEDs differ from incandescent lamps in several ways making photometric measurements challenging. In this thesis, a multifunctional setup based on an integrating sphere has been developed for luminous flux measurements of LEDs. The port design of the setup allows the total and partial luminous flux of low- and high-power LEDs to be measured using a single 30-cm integrating sphere. The light beams of the calibration source and the test LEDs illuminate the sphere in the same direction in all measurement modes. The integrating sphere was thoroughly characterized including spectral throughput measurements in all measurement geometries and spatial scanning of the sphere with a rotating stage and a collimated LED. The luminous flux responsively of the sphere was calibrated against a standard photometer by producing an external luminous flux using a stable incandescent lamp. The expanded uncertainty (k = 2) of the measurement setup varies between 1.2 - 4.6 % depending on the measurement mode, colour and the angular intensity distribution of the test LED. The quality of photometer spectral matching with the spectral luminous efficiency function V(lambda) was studied. The CIE quality factor f1' gives information on the errors introduced, when measuring ordinary broadband light sources with different spectral power distributions. The wavelength uncertainty of the spectral responsivity measurement of filtered detectors may cause a large biased contribution to the measured spectral responsivity. The relative spectral responsivities of two photometers were measured to estimate the uncertainties of their f1' values. By combining random and biased error models in the Monte Carlo analysis, it can be seen that the biased uncertainty components dominate the total uncertainty of the spectral quality factor. If the random error model is used alone, the uncertainty of f1' is underestimated even by an order of magnitude.
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    Wideband radio channel measurements and antennas for millimeter wave communications
    (2010) Kyrö, Mikko; Kolmonen, Veli-Matti; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Vainikainen, Pertti
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    Partitioning and macromodel-based model-order reduction for RLC circuits
    (2010) Miettinen, Pekka; Roos, Janne; Honkala, Mikko; Elektroniikan, tietoliikenteen ja automaation tiedekunta; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Valtonen, Martti
    This thesis details research and development of partitioning-based model-order reduction (MOR) for linear RLC circuits. Additionally, nonlinear circuits can be processed by extracting the linear RLC parts from the complete circuit. By using reduction, large circuits can be approximated with smaller circuits to speed up and help their simulation. Using partitioning in MOR to first partition the circuit into subcircuits makes it possible to use simple low-order approximations (macromodels) per each partition. On the other hand, when the approximated partitions are recombined after the reduction, high accuracy can be reached, if the original partitions are small. By using low-order macromodels, numerical problems typical to direct (outdated) high-order methods can be avoided and, thanks to partitioning, hierarchical analysis can he applied in a natural manner to further facilitate the reduction process. It is shown, in this thesis that by combining partitioning, low-order approximation, and the hierarchical approach, robust MOR algorithms can be obtained. First, two realizable MOR methods suitable for RC (-circuit)-in -RC (-circuit)-out and RL-in -RL-out reduction are presented. Then, a general-purpose, RLC-in -RLC-out MOR method, PartMQR, is presented. Comparison to existing MOR techniques is discussed with each method. Here, it is shown that the presented methods are well comparable with or clearly outperform the existing approaches for the cases shown.
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    Radio wave propagation analysis for single- and multi-link MIMO channel models
    (2010) Poutanen, Juho; Hult, Tommy; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Vainikainen, Pertti
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    Approximate information filtering in publish/subscribe peer-to-peer networks
    (2010) Soitinaho, Jouni; Beijar, Nicklas; Tietoliikenne- ja tietoverkkotekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Kantola, Raimo
    Publish and subscribe systems are becoming increasingly popular in Internet mainly due to the users need to limit the information flood. The pubsub paradigm refers to a model where the receivers (subscribers) specify the information they want to receive instead of letting senders (publishers) decide what they want to send. The problem of this model is often the difficulty to compose the query for exact matching of the words. The user may not find the correct terms, or all synonyms. Approximate filtering addresses this problem by giving the user more freedom to specify the query. This thesis studies the key issues of applying approximate free text filtering to the pubsub model in p2p overlay networks. In approximate filtering the subscriber accepts a document whenever it is similar enough with the query according to the selected measure. The query may be words, phrases or even a text document, and the task of the pubsub system is to match the published documents with the queries and generate the notifications to the subscribers. In a p2p network the documents are published and the queries are stored by any peer, but the user wants the relevant documents regardless of their location, which creates the "rendezvous" problem for the pubsub system to solve efficiently. Three technical problem areas are studied. First, the pubsub model involves the problem of inverse query, i.e. each document is matched against all queries at a time and not vice versa. The solutions developed for databases and search applications are not feasible. Second, in the selected approximate filtering method the query parameters are not matched directly to the document content but both are transformed to an abstract "concept space". This raises the question about the quality of the transformation. Third, the scalability of the p2p network is addressed by comparing the message rate of different publishing strategies. A lot of previous research exists m each of the three technical problem areas However, studies containing all three together are rare. Therefore, the method of the thesis is to review previous studies in different areas and select some alternatives for evaluation. The evaluation is performed experimentally by simulations and analytically whenever feasible. The results are compared in terms of the user experience (filtering quality) and network load (message rate)
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    Parameter estimation for synchronous machine models
    (2010) Mäkelä, Olli; Repo, Anna-Kaisa; Sähkötekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Arkkio, Antero
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    Methods for speaking style conversion from normal speech to high vocal effort speech
    (Aalto-yliopisto, 2020) Ramírez López, Ana; Alku, Paavo; Signaalinkäsittelyn ja akustiikan laitos; Department of Signal Processing and Acoustics; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Alku, Paavo
    This thesis deals with vocal-effort-focused speaking style conversion (SSC). Specifically, we studied two topics on conversion of normal speech to high vocal effort. The first topic involves the conversion of normal speech to shouted speech. We employed this conversion in a speaker recognition system with vocal effort mismatch between test and enrollment utterances (shouted speech vs. normal speech). The mismatch causes a degradation of the system's speaker identification performance. As solution, we proposed a SSC system that included a novel spectral mapping, used along a statistical mapping technique, to transform the mel-frequency spectral energies of normal speech enrollment utterances towards their counterparts in shouted speech. We evaluated the proposed solution by comparing speaker identification rates for a state-of-the-art i-vector-based speaker recognition system, with and without applying SSC to the enrollment utterances. Our results showed that applying the proposed SSC pre-processing to the enrollment data improves considerably the speaker identification rates. The second topic involves a normal-to-Lombard speech conversion. We proposed a vocoder-based parametric SSC system to perform the conversion. This system first extracts speech features using the vocoder. Next, a mapping technique, robust to data scarcity, maps the features. Finally, the vocoder synthesizes the mapped features into speech. We used two vocoders in the conversion system, for comparison: a glottal vocoder and the widely used STRAIGHT. We assessed the converted speech from the two vocoder cases with two subjective listening tests that measured similarity to Lombard speech and naturalness. The similarity subjective test showed that, for both vocoder cases, our proposed SSC system was able to convert normal speech to Lombard speech. The naturalness subjective test showed that the converted samples using the glottal vocoder were clearly more natural than those obtained with STRAIGHT.
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    Millimetrialueen tutkavälkkeen mittausjärjestelmät
    (Aalto-yliopisto, 2019) Peltonen, Jouni; Ruoskanen, Jukka; Sähkötekniikan ja automaation laitos; Department of Electrical Engineering and Automation; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Eskelinen, Pekka
    The aim of this research was to design and construct a stationary and a mobile radar test system and to perform rain and sea clutter measurements in Finnish environment. The performance of these systems is evaluated together with an analysis of obtained results. Open clutter test data exists already from the 1940’s and our own previous experiments suggested a difference to these plus a requirement of site-specific data collection. Both designed test radar installations proved to be working and useful. Particularly rain clut-ter data has turned out to be valuable. The post processing of sea surface clutter results is still going on due to the very limited signal to noise ratio. Our research has been fruitful also due to the simultaneous design and construction of several auxiliary electronic units such as a fast sampling device, antenna platform stabilizer and various digital radar video correlator concepts.
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    A Radar Front-End of a Planetary Altimeter
    (Aalto-yliopisto, 2019) Ruokokoski, Teemu; Räisänen, Antti; Elektroniikan ja nanotekniikan laitos; Department of Electronics and Nanoengineering; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Taylor, Zachary
    The European Space Agency (ESA) is aiming for small landers in future planetary exploration missions. This imposes drastic design constraints on individual components in terms of size, mass and power. A reliable measurement of the ground distance by an altimeter is the key asset for the planetary descent and landing system. In the case of small landers, the size, mass and power consumption of the altimeter must be minimized as well. Harp Technologies Ltd. was responsible for developing a radar front-end of a planetary altimeter. The main project objective was to analyse the most promising radar concept for ESA’s exploration programme, and then design and bread-board the chosen concept. A development of a frequency modulated continuous wave (FMCW) radar front-end for the frequency band 13.25 – 13.35 GHz is described in this Licentiate thesis. At first, a theoretical background for pulse and FMCW radars is presented. Based on the operational requirements, the FMCW radar concept is selected for the further development. The detailed design of the radar front-end is then described, and the performance of the manufactured breadboard is verified in laboratory conditions. The measured power consumption of the radar front-end is less than 2.5 W. The output frequency range is 13.28 – 13.389 GHz and the output power is approximately 14 dBm. The noise figure of the receiver is 6.5 dB. The performance of the realised radar altimeter is deemed satisfactory, and it has also sufficient improvement potential to be suitable for the next phase of the project (i.e. Engineering Model).