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In this paper, a visible light communication transmitter using a LED matrix with low-cost LEDs is shown. This design use a DAC to control the LED drivers, through a discrete component current mirror circuit. The DAC is controlled using an FPGA, which together works as a highly configurable direct digital synthesiser. The design proposed in this paper is thus well suited as a transmitter node in a software defined radio using visible light communication. In this paper, we describe the design, and show its behaviour when programmed to transmit a number of carriers modulated with amplitude and phase modulation schemes.

This paper evaluates the opportunity to utilise external sensors through near field communication (NFC) for smartphones, both, in terms of energy consumption from the smartphones’ battery and time consumption of the smartphones’ user. Our developed sensor card enables external sensors to obtain information, for example, on the current temperature level, humidity level, UV level, and amount of ambient light. We demonstrate that our approach requires significantly less energy and time compared to alternatives which users of smartphones have. Furthermore, we analyse the impact of heat sources present in smartphones on the readings of temperature and humidity level sensors. We propose to externalise sensors in order to minimise the negative impact of temperature on sensors readings and, thereby, improving the accuracy of the measurements and the acquired sensor data.

In this paper, we present a new approach to interrogate sensors using Near Field Communication (NFC). This approach utilizes NFC data exchange format (NDEF) to report the sensor data directly to a cloud service through a smartphone. The new advantage in this approach is that no smartphone application is needed to move the data from the sensor to the cloud. We also discuss advantages and disadvantages of this approach compared to earlier NFC sensor interrogation solutions.

In this paper, we present and evaluate a new approach to communicate with inter-integrated circuit (I2C) enabled circuits such as sensors over near field communication (NFC). The NFC-to-I2C interface was designed using a non-standard NFC command to control the I2C bus directly from a smartphone, which was controlling both, the read and write operations on the I2C bus. The NFC-to-I2C interface was reporting back the data bytes on the bus to the smartphone when the transaction was completed successfully. The proposed system was tested experimentally, both, with write and read requests to a commercial microcontroller featuring a hardware I2C port, as well as reading a commercial I2C enabled humidity and temperature sensor. We present experimental results of the system which show that our approach enables an easy interface between smartphones and external sensors. Interfacing external sensors is useful and beneficial for smartphone users, especially, if certain types of sensors are not available on smartphones.

This paper describes a technique for calibrating the internal ambient light sensor (ALS) in smart phones. The calibration process depends on Near-Field Communication (NFC). The system consists of an NFC core implemented in an Field-Programmable Gate-Array (FPGA) development platform featuring the NFC analog front end circuit. In the proposed system, the smart phone interacts directly with a reference ALS through the NFC device The direct communication is possible with the help of a custom NFC command that controls an Inter-Integrated Circuit (I2C) master core in the FPGA. After the calibration process of the ALS in a smart phone is completed, the accuracy of the measurement is greatly improved. This is helpful to obtain precise information on the light intensity in indoor surroundings.

This thesis investigates the reliability of printed conductors on flexible substrates under cyclic bending. The topic is approached by studying the effects of several key design parameters on the bending lifetime of printed conductors under dynamic loading. In this thesis, the test specimens with various cross-sectional geometries were printed on different plastic and paper substrates. The test samples were fabricated with two printing methods, silk screen and roll-to-roll printing, by utilizing three different silver pastes as the conductive material. To evaluate the long-term performance of the printed traces, the test specimens were exposed to cyclic bending and their electrical behaviour during the test was monitored with resistance measurements. The bending test results were analysed by utilizing the Weibull analysis, with a 20% increase in resistance as the failure criterion. This method yielded a characteristic lifetime for a test population, including 10 individual test specimens. When comparing the characteristic lifetimes of all of the fabricated test populations, it was observed that all of the varied design parameters had an effect on the bending reliability of the printed traces. However, within the studied geometries and materials, the substrate was found to have the highest impact on the long-term electrical performance of printed conductors under cyclic bending. The study proves that the bending reliability of printed conductors can be enhanced by proper design choices. This is done by minimizing the strain when the printed trace is subjected to bending., Tiivistelmä Tässä työssä tutkitaan joustaville substraateille painettujen johdinten luotettavuutta syklisessä taivutuksessa. Aihetta lähestytään tutkimalla useiden tärkeiden suunnitteluparametrien vaikutusta painettujen johdinten elinikään dynaamisessa rasituksessa. Työssä painettiin poikkileikkausgeometrialtaan vaihtelevia testirakenteita erilaisille muovi- ja paperisubstraateille. Testinäytteet valmistettiin käyttäen kahta painotekniikkaa, silkkipainoa ja rullalta rullalle painoa, hyödyntäen kolmea erilaista hopeapastaa johtavana materiaalina. Painettujen johdinten pitkäaikaisen suorituskyvyn arvioimiseksi testinäytteet altistettiin sykliselle taivutukselle ja niiden sähköistä käyttäytymistä monitoroitiin testin aikana resistanssimittauksilla. Taivutustestin tulokset analysoitiin Weibull analyysin avulla käyttäen 20%:n kasvua resistanssissa vikakriteerinä. Tämän menetelmän lopputuloksena saatiin karakteristinen elinikä testipopulaatiolle koostuen kymmenestä yksittäisestä testinäytteestä. Vertailtaessa kaikkien valmistettujen testipopulaatioiden karakteristisiä elinikiä, havaittiin kaikilla vaihdelluilla parametreilla olevan vaikutusta painettujen johdinten luotettavuuteen. Tästä huolimatta, tutkittujen geometrioiden ja materiaalien rajoissa, substraatilla todettiin olevan suurin vaikutus painettujen johdinten pitkä-aikaiseen sähköiseen suorituskykyyn syklisessä taivutuksessa. Tämä tutkimus osoittaa, että painettujen johdinten taivutusluotettavuutta voidaan parantaa oikeilla suunnitteluvalinnoilla. Tämä voidaan toteuttaa minimoimalla venymä painetun johtimen ollessa taivutuksessa.

This thesis studies the methods to test mixed-signal devices and circuits on board and system level with embedded test instrumentation. The study is divided in three continuous sections, development of embedded test methods for discrete components, integration of test instruments on board level and development of test and health monitoring strategy for large scale system. The developed embedded test methods for mixed signal circuitry on board level are based on the standard for mixed signal test bus IEEE 1149.4. The standardized embedded test infrastructure is utilized for testing discrete components with emphasis on testing active components as diodes and transistors. The developed embedded tests are evaluated with PCOLA/SOQ method for manufacturing testing and also the usability of the tests is discussed. A solution for embedded mixed-signal test controller is presented with discussion of test communication and the possibilities of implementing embedded test control. The target in the development of the test control is to enable launch mixed signal tests on device remotely. The test controller is IEEE 1149.4 compatible and can generate and measure analog test signals while controlling boundary-scan enabled devices. The final section of the thesis focuses on an embedded test solution for aerospace bus system (MIL-STD-1553). Current solutions are based on testing the bus system during maintenance on ground. The developed test and monitoring method allows on-line monitoring of the bus to detect and locate possible defects which only occur during use of the aeroplane., Tiivistelmä Väitöstyössä tutkittiin sekasignaalilaitteiden ja -piirien testausmenetelmiä levy- ja järjestelmätasolla hyödyntäen sulautettuja testilaitteita. Työ jakaantuu kolmeen osaan; sulautettujen testausmenetelmien kehitys diskreeteille komponenteille, testi-instrumenttien integrointi piirilevytasolle sekä testaus- ja kunnonmonitorointimenetelmän kehitys laajemmalle järjestelmälle. Sulautettujen testimenetelmien kehitys sekasignaalipiireille piirilevytasolla perustuu sekasignaalitestiväylän standardiin IEEE 1149.4. Standardoitua sulautettua testi-infrastruktuuria käytettiin diskreettien komponenttien testaukseen painottuen aktiivikomponentteihin, kuten diodeihin ja transistoreihin. Kehitetyt sulautetut testit on arvioitu PCOLA/SOQ menetelmällä, jota hyödynnetään tuotantotestauksen testikattavuuden arvioinnissa. Lisäksi testimenetelmien käytettävyyttä arvioitiin. Sulautettu sekasignaalilaitteiden testikontrollerin tavoite on käynnistää ja suorittaa sekasignaalitestejä laitteessa etäältä. Kehitetty testikontrolleri on IEEE 1149.4 yhteensopiva ja voi generoida ja mitata analogista testisignaalia sekä samanaikaisesti ohjata testiväylää. Lisäksi etätestauksen mahdollistavasta testikommunikaatiomenetelmiä arvioitiin kuten myös erilaisia toteutustasoja sulautetuille testimenetelmille. Laajemman järjestelmän kehityksessä tutkittiin sulautettua testausratkaisua lentokoneen väyläjärjestelmälle, joka perustuu standardiin MIL-STD-1553B. Nykyiset menetelmät perustuvat väyläjärjestelmän testaukseen huollon yhteydessä, mutta osa virheistä ilmenee vain käytön aikana. Kehitetty testaus- ja monitorointimenetelmä mahdollistaa käytönaikaisen jatkuvan virheiden monitoroinnin sekä niiden paikantamisen lennon aikana.

This thesis studies the level of performance achievable using today's standard IC processes in the integrated RF subcircuits of the modern GSM base station. The thesis concentrates on those circuit functions, i.e. I/Q modulators, variable gain amplifiers and frequency synthesizers, most relevant for integration in the base station environment as pinpointed by studying the receiver/transmitter architectures available today. Several RF integrated circuits have been designed, fabricated and their level of performance measured. All main circuits were fabricated in a standard double-metal double-poly 1.2 and 0.8 μm BiCMOS process. Key circuit structures and their measured properties are: 90° phase shifter with ±1° phase error with VCC = 4.5…5.5 V and T = -10…+85 °C, I/Q modulator suitable for operation at output frequencies from 100 MHz to 1 GHz and baseband frequencies from 60 to 500 kHz (2.0 mm × 2.0 mm, 100 mA, 5.0 V) with LO suppression of 38 dBc and image rejection of 41 dBc, temperature compensated DC to 1.5 GHz variable gain amplifier (1.15 mm × 2.00 mm, 100 mA, 5.0 V) with a linear 50 dB gain adjustment range, maximum gain of 18.5 dB and gain variation of 1 dB up to 700 MHz over the whole operating conditions range of VCC = 4.5…5.5 V and T = -10…+85 °C, a complete bipolar semicustom synthesizer (90…122 mA, 5.0 V) and two complete full-custom BiCMOS synthesizer chips including all building blocks of a PLL-based synthesizer except for the voltage controlled oscillator and the loop filter. The synthesizers include circuit structures such as ∼2 GHz multi-modulus divider and low-noise programmable phase detector/charge pump (18.7 pA/√Hz at Iout = 500 μA) and have an exemplar phase noise performance of -110 dBc/Hz at 200 kHz offset. One of the main problems of the integer-N PLL based synthesizer when used in a multichannel telecommunications system is the level of spurious signals at the output, when the synthesizer is optimised for fast frequency switching. T