Thermo-Mechanical Design and Validation of Spaceborne High-Speed Digital Receiver Unit for Synthetic Aperture Radar Application

This paper presents the effectiveness of the thermo-mechanical design of a high-speed digital receiver unit (HSDRU) developed for spaceborne synthetic aperture radar applications. The main features of HSDRU’s thermo-mechanical design include the thermal management of high-heat dissipation units by adopting heat sinks with the additional function of structural stiffeners and securing the heat rejection path to the upper side of electronics that interfaces the foil radiator for the on-orbit passive thermal control of electronics exposed to deep space environments. The thermal design, which adopts a thermal gap pad, is closely related to the solder joint fatigue life in a launch vibration environment, owing to its initial compressive static load between the heat sink and heat dissipation units that enhances the heat transfer capability. The effectiveness of the design was validated via the qualification level of launch environment tests.

A Tracking Method in FM Broadcast-based Passive Radar Systems

Passive radars are popular because without the expensive, high-power-rated RF components, they are much cheaper than the active ones, nevertheless, they are much harder to detect from their electromagnetic emission. Passive radars produce so-called RV matrices in an intermediate signal processing step. Although accurate RV matrices are found in DVBT-based passive radars, the characteristics of the FM signals are not always suitable for this purpose. In those situations, further signal processing causes false alarms and unreliable plots, misleads the tracker, and consumes power for processing unnecessarily, which matters in portable setups. Passive radars also come with the advantage of a possible MIMO setup, when multiple signal sources (broadcast services for example) are reflected by multiple targets to the receiver unit. One common case is the stealth aircraft’s which form is designed to reflect the radar signal away from the active radar, but it could also reflect the signals of the available broadcast channels. Only one of these reflected signals could reveal the position of the target.

The eVe reference polarisation lidar system for Cal/Val of Aeolus L2A product

The eVe dual-laser/dual-telescope lidar system is briefly given here, focusing on the optical and mechanical parts of system’s emission and receiver units. The compact design of linear/circular emission unit along with the linear/circular analyser in the receiver unit, allows eVe to simultaneously reproduce the operation of the ALADIN lidar on board Aeolus as well as the operation of a traditional ground-based polarisation lidar system with linear emission. As such, eVe lidar aims to provide: (a) ground reference measurements for the validation of the Aeolus L2A aerosol products, and (b) the atmospheric conditions for which linear polarisation lidar systems can be considered for Aeolus L2A validation, by identifying any possible biases arisen from the different polarisation state in the emission between ALADIN and these systems, and the detection of only the co-polar component of the returned signal from ALADIN for the L2A products retrieval. In addition, a brief description is given concerning the polarisation calibration techniques that are applied in the system, as well as the developed software for the analysis of the collected signals and the retrieval of the optical products. More specifically, the system’s dual configuration enables the retrieval of the optical properties of particle backscatter and extinction coefficients originating from the two different polarisation states of the emission, the linear and circular depolarisation ratios, as well as the direct calculation of the Aeolus like backscatter coefficient, i.e., the backscatter coefficient that Aeolus would measure from ground. Two cases, one with slightly-depolarising particles and one with moderately-depolarising particles, were selected from the first conducted measurements of eVe in Athens, in order to give a glimpse of the system’s capabilities. In the slightly depolarising scene, the Aeolus like backscatter coefficient agrees well with the actual backscatter coefficient, which is also true when non-depolarising particles are present. The agreement however fades out for strongly depolarising scenes, where an underestimation of ~17 % of the Aeolus like backscatter coefficient is observed when moderately-depolarising particles are probed.

Advanced diagnostic system for underground communication networks with ventilation on demand

In this thesis, a novel diagnostic system has been developed to increase the realibility of leaky feeder communication systems in underground mines. The new system is based on three main parts: 1) Diagnostic Receiver Unit (DRU) located in the control room above ground; 2) several Diagnostic Transponder Units (DTU) connected to amplifiers, Power Supply Units (PSU), fans and sensors; and 3) Communication protocol that was designed for this specific system. The amplifiers, PSU, fans, and sensors in the system cascade will be able to communicate freely with the control room through the leaky cable to send information about their current conditions, and receive configuration messages. A new concept is also presented that provides energy saving in mines; Ventilation-on-Demand where the fans will operate according to the current situation of each section in the mine. This is made possible through a series of interrupt messages that is sent from the DTU attached to the fan/sensor to the DRU in the control room.

Advanced diagnostic system for underground communication networks with ventilation on demand

In this thesis, a novel diagnostic system has been developed to increase the realibility of leaky feeder communication systems in underground mines. The new system is based on three main parts: 1) Diagnostic Receiver Unit (DRU) located in the control room above ground; 2) several Diagnostic Transponder Units (DTU) connected to amplifiers, Power Supply Units (PSU), fans and sensors; and 3) Communication protocol that was designed for this specific system. The amplifiers, PSU, fans, and sensors in the system cascade will be able to communicate freely with the control room through the leaky cable to send information about their current conditions, and receive configuration messages. A new concept is also presented that provides energy saving in mines; Ventilation-on-Demand where the fans will operate according to the current situation of each section in the mine. This is made possible through a series of interrupt messages that is sent from the DTU attached to the fan/sensor to the DRU in the control room.

Development of a YAMUGAG-20 Wireless Exploder for Safe Disposal of Military and Civil Explosives

YAMUGAG-20 Exploder is a Radio Frequency (RF)-based wireless exploder system designed and constructed specially for the Nigerian Air Force (NAF) to overcome the challenges associated with the existing wired exploders used for the disposal of unserviceable ordnances. The Exploder system has three main parts namely, the master transmitter unit, the master receiver/slave transmitter unit, and the slave receiver unit. Each of these units is made up of transceiver module, microcomputer and power source. The microcomputers were programmed using C and C++ programming language of the Integrated Development Environment (IDE) software. The exploder is portable and easy to operate. For a typical demolition exercise, the operation of the exploder is such that signals are relayed from the master transmitter unit to the master receiver/slave transmitter unit onto the slave receiver unit to initiate an electric detonator leading to the detonation of the unserviceable ordnances. Functionality, range, power consumption, and system reliability tests were conducted on the exploder to establish its performance and efficiency. The results obtained from the tests indicated that the exploder transmitting at a frequency of 2.4GHz performed satisfactorily up to a range of 1000 meters. Therefore, the exploder has the potential of not only meeting the demolition demands of the NAF but can also be applied for other nonmilitary purposes like mining and related activities.

Application of Wireless Accelerometer Mounted on Wheel Rim for Parked Car Monitoring

Damages of different kinds that can be inflicted to a parked car. Among them, loosening of the car wheel bolts is difficult to detect during normal use of the car and is at the same time very dangerous to the health and life of the driver. Moreover, in patents and publications, only little information is presented about electronic sensors available for activation from inside of the car to inform the driver about the mentioned dangerous situation. Thus, the main aim of this work is the proposition and examination of a sensing device using of a wireless accelerometer head to detect loosening of wheel fixing bolts before ride has been started. The proposed sensing device consists of a wireless accelerometer head, an assembly interface and a receiver unit. The assembly interface between the head and the inner part of the rim enables the correct operation of the system. The data processing algorithm developed for the receiver unit enables the proper detection of the unscrewing of bolts. Moreover, the tested algorithm is resistant to the interference signals generated in the accelerometer head by cars and men passing in close distance.

Thermal performance and design parameters investigation of a novel cavity receiver unit for parabolic trough concentrator

In this paper, we discuss an improved concept for a cavity receiver unit for Solar Parabolic Trough Collectors (PTC) with the application of hot mirror coating (HMC) on a cavity aperture. This design aims to lessen radiant energy losses while operating at higher temperatures by incorporating a variety of optically active layers. We present the theoretical background, which we derived in previous work, and the resulting implementation in a simulation code. We next discuss the layout and results of an experiment, which allowed us to make contact with the simulation with minor adjustments It was seen that the correspondence between the experiment and simulation results was encouragingly close (Chi-squared p > 0.8 and p > 0.95), and we proceeded to investigate simulations of different receiver designs. Simulated outcomes for the temperature of the heat transfer fluid, temperature maps, and efficiencies are presented. Our proposal indicates temperature-related benefits when compared to other popular designs in terms of the heat transfer fluid temperature and efficiency.