Tomas Urbanec

Experimental band monitor for PSAT satellite

During changing sun activity, the ionosphere is responding accordingly and therefore it is interesting to observe the propagation behavior of shortwave bands. For the above mentioned purpose we are designing a monitoring payload for an experimental cubesat satellite called PSAT. The payload consists of a receiver, which is able to receive SSB modulated narrowband signals in 28 MHz uplink band and a transmitter with FM modulation in UHF downlink frequency band. The receiver frequency is selected to be at the center of radio amateur activity with low data rate digital modulations.

Variable Impedance in Measuring EMI Filter’s Insertion Loss

This paper deals with problems concerning variable impedance of power lines in the measurement of insertion loss of EMI filters. A circuit which represents variable power line impedance was designed and was added into the normal measuring structure of EMI filters. This was applied to an asymmetrical and a non-symmetrical measurement technique. The design, structure of measurement and results obtained are explained in this paper

Slow Data Rate Sequence Satellite Ranging

In this paper a simple newly developed semicoherent slow data rate ranging application for small satellites is described. Ranging, as a set of methods for satellite tracking, is a very important part of most of the satellite systems and the space missions. Firstly, a brief overview of the most commonly used ranging methods is presented. After that, a semicoherent ranging system is described that has to be implemented in a simple experimental system for feature testing using a simple linear transponder of an AMSAT satellite phase-3E and phase-5A probe. Practical test range measurements via FO-29 satellite have been carried out by this system

An innovative HVAC control system: Implementation and testing in a vehicular cabin

Personal vehicles undergo rapid development in every imaginable way. However, a concept of managing a cabin thermal environment remains unchanged for decades. The only major improvement has been an automatic HVAC controller with one users input - temperature. In this case, the temperature is often deceiving because of thermally asymmetric and dynamic nature of the cabins. As a result, the effects of convection and radiation on passengers are not captured in detail what also reduces the potential to meet thermal comfort expectations. Advanced methodologies are available to assess the cabin environment in a fine resolution (e.g. ISO 14505:2006), but these are used mostly in laboratory conditions. The novel idea of this work is to integrate equivalent temperature sensors into a vehicular cabin in proximity of an occupant. Spatial distribution of the sensors is expected to provide detailed information about the local environment that can be used for personalised, comfort driven HVAC control. The focus of the work is to compare results given by the implemented system and a Newton type thermal manikin. Three different ambient settings were examined in a climate chamber. Finally, the results were compared and a good match of equivalent temperatures was found.

Implementation of the equivalent temperature measurement system as a part of the vehicle Heating, ventilation and Air-conditioning unit

Thermal comfort evaluation based on the Comfort zone diagram is relatively new and promising method [1] developed by Hakan O. Nilsson [2]. The method was developed mainly for non uniform indoor environments [3] such as vehicle cabins [4]. Mean thermal vote (MTV) is correlated with equivalent temperature, which is typically measured by a thermal manikin with clothing or by a sensor with heated surface. This fact is the advantage of this method because prediction of thermal comfort is based on a measurable physical phenomenon which is called dry heat loss. The essence of this method inspired us to develop a measurement system that will be based on miniaturised and cost effective equivalent temperature sensors. Such sensors could be easily integrated into the surroundings of seated human and could provide data about local thermal comfort as feedback information for HVAC control unit. Our project, which started last year, is called Innovative control for Heating, Ventilation and Air Conditioning systems, iHVAC.

A band monitor for a cubesat-type satellite

During changing sun activity, the ionosphere is responding accordingly and therefore it is interesting to observe the propagation behavior of shortwave bands. For the above mentioned purpose we are designing a monitoring payload for an experimental cubesat satellite called PSAT. The payload consists of a receiver, which is able to receive SSB modulated narrowband signals in 28 MHz uplink band and a transmitter with FM modulation in UHF downlink frequency band. The receiver frequency is selected to be at the center of radio amateur activity with low data rate digital modulations.

Vector network analyzer versus sixport comparison for ground penetrating radar

The standard ground penetrating radar (GPR) realized with pulsing technology has its limitations and alternatives exist. Using vector network analyzer (VNA) with time domain transformation is possible, but cost of such implementation is prohibitive. The sixport measurement system can be used as alternative to standard VNA. The comparison of the test cases measured by VNA and sixport are in the paper. The resolution is the same and the dynamic range even greater with the use of sixport system.

High resolution easy to build 2D scanner of EM field

Paper describes the easy way to obtain high resolution EM field scanner with the use of surplus plotter and minimum mechanical modification. Examples of probes are described with its measurement results comparison. Realized software is described then and measurement examples are given. In the end there are presented suggestions for the parameters advancement.

0-2.5 GHz Generator Based on ADF4360 Controlled by Microprocessor

The aim of this paper is not to bring a theoretical expressions and some new ideas in mixing theory, but only to show a simple wide band RF generator design with one mixing. The instrument is based on two integrated frequency synthesizers (ADF-4360-x) controlled by Atmel AVR microcontroller via integrated SPI bus. Wide frequency range is achieved by dividing ADF output signal by two using internal frequency divider, signal mixing and suitable switching. Frequency tunning is discontinuous (because of synthesizers), but ADFs are allowed to design frequency step of tens of kilohertzs. In this design, 1 MHz tunning step and (1-2837) MHz bandwidth are used. Simple output microwave lowpass filter (with 3 GHz limit frequency) and two microwave high-pass filters (with 1.7 GHz and 1.9 GHz limit frequencies) around mixer are included in generator design. Of course, microwave gain blocks, monolithic mixer and monolithic and discreet microwave switches are used in also.

Compact size substrate integrated waveguide phase shifter

The design and implementation of the proposed compact size substrate integrated waveguide (SIW) phase shifter for the K band is presented. The comparison of the simple moved via towards the center of SIW and the structure with three vias moved towards the center with the smooth transition is presented. Results show that return loss values are better and working bandwidth is preserved for greater phase shift obtained. The phase shifter offers 51.4° in the K band.