Zdenko Brezovic

Optimization PLL synthesizer with active RC notch filters

The linear model of Phase-locked loop with triple active RC notch filters (ARCN) which is proper for investigating of dynamic properties in the time domain and frequency domain are presented in this contribution. Also the noise analysis and noise optimization of such filters were carried out. Spectral properties and phase noise measurement on experimentally evaluated frequency synthesizer were carried out. Based on numerical simulations results has been possible to design good ARCN filters.

PLL synthesizer with very low discrete spurious

Frequency, transient and noise numerical analysis of a triple active RC notch filters (ARCN filters) are presented in this contribution. ARCN filters analyzed here are used for additional damping of the first unwanted harmonics (1., 2. and 4. ) at the phase detector output voltage. Every additional passive filter inside the PLL very often causes instability due to its too big additional phase shift. On the base numerical simulations results it is possible to design good ARCN filters with small phase shift within active PLL bandwidth. Also the noise analysis and noise optimization of such filters was carried out.

Active RC notch filter for phase-locked loop

In this paper, we present some results of computer simulations oriented on frequency and noise properties of an active RC notch filter (ARCN filter), which is intended to provide high reference spur suppression in the phase detector output voltage of PLL. In this paper also has been presented the substitution of complicated active ARC structure with the simple passive RLC filter. On the base numerical simulations results it is possible to design good ARCN filters with small phase shift within active PLL bandwidth.

A two-resonator quartz model for advanced PC-supported design for a VCXO

In this contribution we will demonstrate an extended-usage two-resonant circuit model of quartz with two LC resonators for numerical computation tuning characteristics. Real crystal resonators contain, besides a dominating resonance, other, unwanted parasitic resonances. Their existence can markedly modify the tune performance chart of the VCXO.

PLL phase-noise modeling by PC

The linear model of phase locked loop which is proper for investigating of phase noise properties in the frequency domain is presented in this contribution. For simulation on PC analog-digital circuit analysis program Micro-Cap is used. Verification of the MC numerical simulations was done by MATLAB and measurements on the prototype were carried out. Based on numerical simulations results it is possible to verify basic theoretical relations and make a good PLL design. Using the mathematical analysis software MATLAB, along with the previous example, it will be possible to show how the various noise sources in a PLL can be modeled. A PSPICE noise macro models using the polynomial model of noise sources were tested successfully.

A Flexible Oscillator for Measurement of Varactor-Tuned Resonators

A new version of RF oscillator with high linearity (THD<1%) and wide zone of adjusting its amplitude (min. 40 dB) is presented in this contribution. Oscillator is designed for single and quickly measurement of non-linearity effects in varactor-tuned LC resonators, and it is usable in frequency band from LF up to 50 MHz. Active part of the oscillator consist of high-speed OA of type VFB (voltage feedback), or CVB (current feedback) and resistive feedback circuit. Herein are presented analytical relationships derived for parameters input characteristics for both VFB OA and CVB OA respectively. OA with positive feedback has in the centre its input characteristics negative resistance, which give the possibility to compensate losses in parallel LC resonator. For simple and effective control of the oscillation amplitude is used backward biased diode detector with control voltage. In contributions are also presented measured parameters of the oscillator and there are given some examples of measured tuning characteristics with varactors.