To make a double CubeSat with limited power resources capable of transmitting large amounts of data to Earth a high gain antenna is needed. In this thesis a switched beam MSA array operating at 5.84 GHz has been designed to operate on a double CubeSat. The array has 5 beams and uses a switched-line phase shifter to switch between beams. Three different array geometries has been proposed. Computer simulations suggest that the array should be capable of an effective beamwidth of over 60 degrees with a directivity of over 11 dBi. A feed network has been designed to fit the best suited geometry. A ground plane will separate the feed network from the antenna elements. Along with the full array solution all the sub parts has been realized as test circuits. This allows for an evaluation of their characteristics. A TRL calibration kit has also been designed so that the sub parts could be more accurately evaluated. When sending the circuits to fabrication it appeared to be a problem with the selected substrate used for the antenna elements. A redesign using the same substrate for the feed network and antennas was done and production commenced. As it turns out, the TRL calibration kit was not good enough so the S-parameters had to be measured with regular SOLT calibration. Significant problems with connection to ground and mismatches due to a poor SMA-to-microstrip transition was encountered. This caused large deviations between measured and simulated results. It was also discovered that the wrong dielectric constant had been used. This error caused the antenna elements to be dimensioned for operation at 5.70 GHz instead of 5.84 GHz. Problems was also encountered in the switched line phase shifter design. Beam-lead PIN-diodes has been used and due to their small size, a sufficient quality of the soldering was not achieved. This lead to different losses through the phase shifter which again caused the different beam directions to vary from simulations. Only one beam had characteristics similar to simulations. Measurements on the array without phase shifters showed good correspondence with simulation results (adjusted for the correct dielectric constant). It is concluded that by making a better SMA-to-microstrip transition, improve the soldering work and do a redesign with the correct dielectric constant, the array configuration should work as outlined in the design process.

More to come

The main goal of this thesis is to present two good alternatives for the HDL+ protocol proposed for ratification in STANAG 4538, as this partially is restricted by a patent claims. The HDL+ protocol is used as a starting point, and in order to accommodate for the patented parts, the adaptive process is altered, and the code combining process is removed for the highest rate. For simplifying the comparison between the performance of the proposed protocols, and the HDL+, both proposed protocols is simulated in a MATLAB environment, over the same channels as Harris has presented the throughput capabilities of the HDL+. These channels include the AWGN, single tap channel with flat fading, the ITU-MLD channel, and the ITU-MLD channel with Long- and Intermediate- Time SNR variations. By analyzing the results, it is clear that the current implementation of the proposed protocols does not achieve as high throughput as the HDL+, but there are indications that there is potential for better results if further development is performed.

This work explores an alternative set of features to the frequently used melfrequency coefficients (MFCCs). The cochlea features simulate the nerve fibre signal sent from the ear to the brain. In this study the usage of the cochlea features for acoustic segmentation is of main interest. Both the cochlea features and a variant of combining them with zero crossing with peak amplitude (ZCPA) have been used as input to an acoustic segmentation algorithm. Also experiments using the cochlea features as input to an artificial neural network (ANN) for classifying each vector as boundary/non-boundary have been performed. The results show that the features contain a great deal of information regarding the speech signal. Especially the combination of cochlea and ZCPA are giving good results.

Atmospheric impairments are a major obstacle in satellite communications at Ka-band in high latitude regions. This report gives a short summary of the existing models that can be used to model the impairments. Further a simple measurement system based on satellite beacon reception is designed using locally available and off-the-shelf components as well as locally manufactured ones. Performance of the components as well as of the whole system is examined and found to be in agreement with the expected values with overall system figure of merit (G/T) of 21 dB/K. Data from 25 days of measurements are presented and compared with model predictions. The comparison points to possible deficiencies in some of the system components that should be assessed for further use. Most notably low amplitude accuracy of the spectrum analyzer and a low sampling rate of the data acquisition system.

This work contains a study of underwater acoustic networks. The concept of underwater acoustic networks has been presented with its benefits and drawbacks. An overview of the marine research areas oceanography, seismology, waterside security, marine pollution and marine biology has been made and a review of conventional methods and instrumentation committed. The research methods used today have been compared with the potential of underwater acoustic networks as a platform for maritime applications. Underwater acoustic networks were reviewed as feasible within all areas with some restrictions. The fact that respectable data rate is best achieved for nodes deployed in a high density grid give limitations on the coverage area. Battery as an energy source limits the life span of an underwater acoustic network and makes it best suited for missions for short term monitoring, if not a recharging technology is applied. The energy restrictions also put constraint on the amount of sensing done and the temporal solution in measurements. Underwater acoustic networks were found applicable for intrusion detection in waterside security to increase the range of current ultrasonic surveillance systems or realize distributed systems for passive diver detection. In oceanography and pollution monitoring current in situ sensors may enable underwater acoustic networks to do autonomous synoptic sampling of limited areas to measure a number of parameters, e.g. oxygen, turbidity, temperature and salinity. For seismic exploration this technology might save costs for permanent seismic installations in constant monitoring of producing oil fields. It might also aid marine biologists in habitat monitoring.

Due to increase in ship traffic and activities related to oil and gas there is currently grate interest in the northern regions of Norway. Satellite communications to these areas i.e. north of the polar circle is however challenging due to low elevation angles and restricted visibility of geostationary satellites. Limited work has been done to study the propagation effects at theses latitudes and low elevation angles, especially at millimeter frequencies and for maritime communications. Some measurements have been conducted at Svalbard [5] and in Canada [5.1]. The studies from Svalbard were conducted at Ku-band frequencies whilst the Canadian measurements were conducted at 38 GHz. Non of the two did however include maritime measurements. Further measurements are therefore needed to characterize the propagation effects under these conditions. A beacon receiver is radio which is used to detect and measure the signal strength of a transmitted radio beacon signal. Beacon signals transmitted by satellites are often low power continuous wave signals intended for antenna steering and power control purposes. These signals are well suited for propagation measurement due to their constant transmits power and frequency. Propagation research often relies on beacon measurements along with other information such as weather data and radiometer readings. This thesis discusses the design and implementation of a low cost beacon receiver based on digital signal processing techniques and software defined radio. The intention was originally to design a Ka-band (20 GHz) receiver. This was however extended to a general purpose beacon receiver intended to operate at an L-band intermediate frequency. Different architectures and realizations are discussed with emphasis on costs and performance. It is shown that a 1.2 m antenna, receiving a Ka-band beacon with, 9 dBW EIRP would produce a signal level of about -130 dBm at its output. This would in turn yield a C/N0 ratio of about 46 dBHz at 76°North, assuming a receiver with overall noise figure of 1.5 dB and clear air conditions. Based on the link budget calculations two different beacon receiver designs are proposed. One based on the superheterodyne receiver architecture realized with standard RF-components such as mixers and amplifiers with coaxial connectors. The second design is based on the universal software radio peripheral, (USRP), which is a software radio, intended to allow personal computers function as radio transceivers. It was found that building a complete beacon receiver from standard RF-components would require about 100.000 NOK to achieve the wanted performance. This includes a complete system with antenna, front-end and baseband receiver. Due to the relatively inexpensive hardware (4900 NOK) of the USRP and the availability of front-end plug inn boards in the required intermediate frequency range the USRP was chosen as the hardware portion of the receiver. Linearity measurments and observations of the USRP output spectrum shows a linear dynamic range of about 60 dB which is found sufficient for beacon measurements. A Ku-band antenna intended for television reception has been used to receive a 12.2 GHz beacon transmitted by Eutelsat W3A Software code was developed based on the GNU radio framework in order to use the USRP as a beacon receiver. A number of issues were discovered during this work: •GNU radio does not contain filters for spectral averaging •Attempts to implement additional functionality in software proved challenging due to limitations in computational speed Both of the two issues affected the performance of the beacon receiver. Modifications and additions to the GNU radio software is therefore suggested for future work

This Thesis covers a part of the study comprised in the ULTRASPONDER (In vivo Ultrasonic Transponder System for Biomedical Applications) Project. The main area of interest is to study how to combine different signals which can imply an improvement onto the diagnostic information carried by the ECG records. It is believed that monitoring blood pressure inside the heart may give vital information to correctly diagnose and provide treatment for chronic heart failure patients. Moreover, heart rate variability analysis has proved to be one of the most important risk predictors in detecting ventricular tachycardias and fluttering. With this focus, the Thesis provides a solid background on cardiac anatomy and physiology, uncommon in many engineering texts, in order to understand the biological changes that affect the waveforms, for then moving to the performance of a theoretical and statistical study in order to find correlations, redundancies, or new information content in the signals intended to cohabit in the ULTRASPONDER control unit, namely, signals from the intra-cavity pressure sensors, ECG electrodes and other type of sensors, as well as heart rate time-series. Because this control unit, implanted underneath the patient's skin, must handle several different signals and transmit clinically relevant information in a power constraint manner to an external device, which may have much larger amount of resources, all signal processing performed in the context of the control unit must be kept under a reasonable limit that permits to efficiently extract information about the patient's health without decreasing the device's lifetime. We have implemented two time-domain QRS complexes detection systems, two simple beat classification algorithms based on beat-to-beat segmentation and template correlation, and some HRV measures as fundamental elements of ECG signal processing. Detection performance is analyzed from a critical point of view, considering several not so common parameters, such as Qalpha and MCC, which collect much more information than the usual sensitivity and predictivity assessments. A closed-loop DPCM system was chosen for the encoding and compression tasks, experiments showing its validity for ECG and blood pressure signals, although advising against its usage for HR time series. Compression performance is analyzed in terms of compression ratio attained and distorsion introduced. A novel measure called "compressibility quotient" (CQ) is presented as an indicator of the balance between theoretical compression limits marked by the sample entropy and actual compression obtained with a concrete scheme, in terms of the tradeoff CR-distorsion. A strong correlation between signal-to-noise ratio and CQ was found, implying that this measure might have some relevance for analyzing real compression possibilities under some quality criteria. The approaches followed in this Thesis, particularly regarding the theoretical study and data fusion comments, are valid for the ECG, blood pressure and heart rate signals considered, without detriment to be likewise applied to new signals that might become of interest in the future years. When new sensors are implemented to provide distinct signals, a theoretical study can include them to find out their usefulness and relation to the ones already considered. Data fusion should then be reviewed to assess the validity and convenience of the communication system for the new set of significant signals.

This thesis focuses on class A radio frequency power amplifiers in dynamic supply modulation architectures (dynamic bias). These are promising efficiency enhancement techniques where the device is driven harder by varying its bias signals. Non linearities that arise are considered as digitally compensated through, for example, digital predistortion (DPD). Bias signals are meant as functions of the PA?s output power level (P out). Therefore, the input power level (P in) as well as the feeding signals are thought as quantities the amplifier need to give a certain P out. The selected set of bias points the device sweeps through is called bias trajectory or bias path. A tool to find a suitable bias trajectory is developed considering the requirements a class A power amplifier should satisfy: high power added efficiency, acceptable gain and output phase variations as P out changes (allowing a DPD algorithm to be effective), low harmonic distortion and not too complicated bias signals patterns. The tool consists of two softwares: ADS and Matlab. ADS simulates the device under test while Matlab allows the user to analyze the data and find a suitable bias path. Once a trajectory is identified, ADS can sweep along it and give more information on linearity and efficiency through, for instance, 2-tone harmonic balance simulations. Note that only static characteristics are evaluated and memory effects disregarded. The path searching algorithm is then applied to a HBT transistor, at a frequency of 1.9GHz and to a complete pHEMT class A PA (frequency of 6Ghz). In both cases a suitable trajectory is identified and analyzed back in ADS. The Matlab plots are qualitatively similar to each other when switching form one device to another. The HBT transistor has then been tested in the laboratory and static measurements have been performed showing good agreement with simulations. Keywords: Bias trajectory, dynamic bias, efficiency, HBT, linearity, pHEMT, power amplifier

Ultramonit is a system under development for permanent installation on critical parts of the subsea oil- and gas pipelines in order to monitor the corrosion continuously by using ultrasound. The communication link which connects the Ultramonit units with the outside world is identified as the system’s bottleneck, and it is thus of interest to compress the ultrasonic data before transmission. The main goal of this diploma work has been to implement and optimize a lossy compression scheme in C on the available hardware (HW) with respect to a self-defined fidelity measure. Limited resources, such as memory constraints and constraints with respect to the processing time, have been a major issue during implementation. The real-time aspect of the problem results in an intricate relation between transfer time, processing time and compression ratio for a given fidelity. The encoder is optimized with respect to two different bit allocation schemes, two different filters as well as various parameters. Compared to transferring the unprocessed traces, the results demonstrate that the transfer time can be reduced with a factor 12. This yields acceptable fidelity concerning the main application of long term monitoring of subsea pipelines. However, for ultra-high precision applications where the total change in thickness due to corrosion is less than a few micrometers, compression should not be employed.