| Abstract | U ovom je radu napravljena realizacija visoko propusnog filtra četvrtog reda u bikvartnoj strukturi s aproksimacijom po Besselu, s aproksimacijom po Chebyshevu kao i realizacija visoko propusnog filtra četvrtog reda u kaskadnoj strukturi s aproksimacijom po Besselu. Na temelju parametara iščitanih iz tablica dobivene su prijenosne funkcije nisko propusnih filtara nad kojima je izvršena frekvencijska NP - VP transformacija kako bi se dobile normirane prijenosne funkcije visoko propusnih filtara. Denormiranje je izvršeno na graničnoj frekvenciji of 4 kHz te je napravljena analiza frekvencijskih i vremenskih karakteristika normiranih i denormiranih prijenosnih funkcija i usporedba frekvencijskih i vremenskih karakteristika denormiranih prijenosnih funkcija filtra s aproksimacijom po Besselu i filtra s aproksimacijom po Chebyshevu. Nadalje se izvršila realizacija filtarskih struktura s normiranim i denormiranim elementima u sve tri strukture, te se u svrhu provjere izvršila analiza frekvencijskih i vremenskih karakteristika u programu LTSpice. Nadalje se analizirala Schoefflerova osjetljivost filtarskih realizacija te su se uspoređivale osjetljivosti između filtra s aproksimacijom po Besselu i filtra s aproksimacijom po Chebyshevu, kao i filtra s aproksimacijom po Besselu u kaskadnoj strukturi s filtrom u strukturi bikvarta. Potom je napravljena "Monte Carlo" analiza filtra s aproksimacijom po Besselu u kaskadnoj strukturi s filtrom u strukturi bikvarta. U idućem je poglavlju izvršen izračun šuma zadanog filtra gdje se ukratko opisao šum i analizirani termički šum. Grafički su prikazane karakteristike šuma pasivnih elemenata, operacijskih pojačala te pojedinih sekcija, kao i ukupan šum filtra u bikvartnoj strukturi s aproksimacijom po Besselu. U zadnjem se poglavlju prikazala realizacija realnog filtra s realnim vrijednostima elementima, prikazane su frekvencijske i vremenske karakteristike te je napravljena shema spajanja filtra te izrada i izgled PCB pločice s ostalim potrebnim elementima. |
| Abstract (english) | In this paper, a fourth-order high-pass filter in a biquad structure with Bessel approximation, a fourth-order high-pass filter with Chebyshev approximation, and a fourth-order high-pass filter in a cascade structure with Bessel approximation are realized. Based on the parameters read from tables, the transfer functions of low-pass filters were obtained, and a frequency LP - HP transformation was performed to derive the normalized transfer functions of the high-pass filters. Denormalization was carried out at the cutoff frequency $ f_{g} = 4 \text{ }kHz $, and an analysis of the frequency and time characteristics of the normalized and denormalized transfer functions was conducted. A comparison of the frequency and time characteristics of the denormalized transfer functions between the Bessel and Chebyshev approximations was made. Furthermore, the implementation of filter structures with normalized and denormalized elements in all three structures was performed, and an analysis of the frequency and time characteristics was conducted in LTSpice for verification purposes. Additionally, the Schoeffler sensitivity of the filter implementations was analyzed, comparing the sensitivities between the Bessel and Chebyshev approximations, as well as the Bessel approximation in the cascade structure versus the biquad structure. A Monte-Carlo analysis of the Bessel approximation filter in the cascade structure and the biquad structure was then performed. The following chapter includes a noise calculation for the given filter, briefly describing noise and analyzing thermal noise. Graphical representations of the noise characteristics of passive components, operational amplifiers, and individual sections, as well as the total noise of the Bessel approximation filter in the biquad structure, are presented. The final chapter presents the realization of a real filter with real element values, showcasing the frequency and time characteristics, the filter connection diagram, and the design and layout of the PCB with the necessary components. |
