Dwuzakresowy analizator widma dla zakresu częstotliwości radiowych

W artykule przedstawiono analizator widma, zrealizowany w technice analogowej. Przedstawione tu rozwiązanie dotyczy analizatora w klasycznym układzie z przemianą częstotliwości. Sterowanie części analogowej zrealizowano za pomocą mikrokontrolera 8-bitowego. Zaprezentowano przykład zmiany koncepcji realizacji klasycznego analizatora widma, pozwalający na zmniejszenie kosztów przyrządu i poprawę komfortu obsługi. Wskazania urządzenia są dostatecznie zbieżne z przyrządami wzorcowymi.

This paper presents a simple spectrum analyzer based on analog techniques and 8-bit microprocessor (Atmel AVR microcontroller – Atmega16A [6]) used in control section. The method of spectrum analysis is frequency conversion with tunable local oscillators in first and second conversion stage. This is an example where first frequency conversion stages are based on module from television receiver and satellite receiver. The local oscillators are controlled by PLL loop. The device has two inputs called “Input A” and “Input B”. Measurement range of “Input A” is from 45MHz up to 860MHz, but for “Input B” it is from 950MHz up to 2000MHz. Block diagram of the spectrum analyzer is shown on figure 1. The device can measure value of the frequency components using marker but it cannot measure amplitude value. Measurements effects are presented on the graphic LCD display based on T6963 (Toshiba) controller [9]. Communication with PC computer is realized with RS232C interface. Article explains a new, simple and cheap but useful structure of the spectrum analyzer. Combination of the measurement errors is presented in table 1. Tables 2 and 3 explains combination of measurements results of analyzer from this article and ROHDE&SCHWARZ FSL3. Figures 4 and 6 explain spectrum of the analog TV channel (fig. 4) and digital TV channel – DVB-T (fig. 6) measured by analyzer from this article. Figures 3 and 5 explain the same channel like figures 4 and 6, but it was measured by FSL3 spectrum analyzer.