Stanislava Papezova

Power wire-wound RF resistor with high linearity

This paper describes a wire resistor with the resistance of several hundreds ohms, with a power dissipation up to several hundreds watts. In a high frequency band, it shows maximum frequency reflection coefficient values with respect to the nominal resistance value of about 0.1, and which reaches a third order IM distortion products close to −130dBc at the dissipation power.

Highly pure signal generators

The special testing signal generators were designed for a series of frequencies in the frequency band 0.5 to 20 MHz. The generator is very simple. It is composed of only one stable crystal oscillator and one high power amplifier. The frequency stability of the generators is in the order of 10−6/day, the output power is 1W, the value of SINAD is under −130 dB and the total harmonic distortion is under −170 dB by using a linear narrowband filter.

Non-linearity diagnostics of nominally linear components

Traditional methods and new method for measurement of low non-linearity of electronic components and circuits are described in this paper. Maintaining a linearity of components and circuits that are on principle linear is a measure of their quality. Passive intermodulation distortion (PIM) and non-linearity itself arises as a result of faults in production or component degradation and limits their usability.

Transformer short-time overload testing

An increased level of safety in operation is one of the requirements prescribed by EU regulations for control trans-formers. This requirement is verified by a special test of the transformer resistance during its short-time overload. The paper provides an analysis of testing conditions and gives an example of the testing equipment construction.

High sensitivity phase noise measuring equipment

This article describes a device for a phase noise measurement using the phase locked loop (PLL). This allows measuring signals with the possibility of passing the phase noise better than -160 dB. There are analyzed the effects of the measuring device on the measuring results and presented examples of solving the PLL, circuits for low-frequency signal processing and power supplies with their minimal basic noise.

Equipment for the automatic testing of power capacitors

The paper describes a special method for testing power capacitors by means of their loading by alternating current with the effective value up to 100 A at frequencies in the order of units up to tens of kHz. There is described the realization of the test equipment enabling a precise compensation of the reactive power of the capacitor and the input minimisation at the testing. It discusses the realization of the key components and parts of the measuring equipment.

Frequency compensated high power matrix resistor network

This paper describes a circuit arrangement, design and construction of the power load composed of many pieces of thick film flanged resistors, which are serial-parallel connected so that the resulting combination showed the desired impedance-resistance, which may or may not be consistent with the resistance of individual components and, at the same time, it can be loaded with more power than a single component. The solution is given to the compensation circuit which increases several times the maximum frequency at which the load is applied.

Low level phase noise measurement techniques

This article describes a device for phase noise measurement using the phase lock technique. This allows the user to measure signals with level of the phase noise lower than -160 dBc/Hz. The effects of the measuring device on the measurement results are analyzed and examples phase noise measurements using PLL method, circuits for low-frequency signal processing and for power supplies with minimal own noise are presented.

Bridge symmetric crystal oscillator

This contribution describes bridge symmetric crystal oscillator. A selective component of the oscillator is realized as Wheatstone bridge with two identical crystal resonators. An amplifier of this oscillator is realized as a symmetrical differential amplifier. Oscillator is especially solved with a view to achieve minimal phase noise of generated signal. Results are compared with common Gouriet-Clapp oscillator.

Bio-impedance signal processing using adaptive digital filter

Bio-impedance evaluation is one of the medicine diagnostic methods for the evaluation of tissue perfusion. The bioimpedance on the patients body surface is evaluated by analogue HF-vector Z-meter. The Z signal is converted into a digital form and further digitally processed and filtered. Spurious disturbing signals distorting the bio-impedance signal are suppressed by adaptive FIR filter.