Power supply modulation circuits for radio-frequency power amplifiers

Glavni dio svakog primopredajnika signala je pojačalo snage, a ono je ujedno i najveći potrošač električne energije. Jedan od načina povećanja efikasnosti pojačala je modulacija napona napajanja. Princip modulacije koji se najčešće koristi za povećanje efikasnosti linearnih pojačala snage je praćenje ovojnice. U sklopu ovog rada projektiran je modulator napona s dvije diskretne razine napona napajanja, a nakon odrađenih simulacija, modulator je izveden na tiskanoj pločici. Kao prekidački tranzistori korišteni su bipolarni tranzistor s horizontalnim tokom struje (HCBT) i komercijalni tranzistor s efektom polja te je napravljena usporedba. Pokazalo se da su poklapanja simuliranih i izmjerenih rezultata vrlo dobra te je postignuta efikasnost od 87,77 % koristeći MOSFET, što je samo 3 % manje od očekivanog. Za odgovarajuće razine napona napajanja, efikasnost sklopa s HCBT-om iznosi 82,52 % pa se može zaključiti da se HCBT može koristiti i u prekidačkim primjenama i pri tome dati vrlo dobre rezultate. Projektiran je i modulator napona napajanja s kontinuiranim praćenjem ovojnice, koji bi trebao dodatno smanjiti disipaciju pojačala snage. Kako bi se utvrdilo rade li modulatori napona napajanja dobro, trebalo bi ih spojiti u sustav s pojačalom snage i provjeriti postoji li povećanje efikasnosti pojačala.The main part of every signal transceiver is a power amplifier, which is also the largest consumer of electricity. One method of increasing the amplifier efficiency is supply modulation. The most commonly used modulation principle for increasing the efficiency of linear amplifiers is envelope tracking. In this thesis, a supply modulator with two voltage levels was designed, and after simulations were conducted, the modulator was made on a PCB. Horizontal current bipolar transistor (HCBT) and commercial FET were used as switching transistors and a comparison was made. It is shown that the simulated and measured results were well matched and efficiency of 87,77 % using MOSFET was achieved, which is only 3 % lower than expected. For conveniently chosen voltage levels, efficiency of the modulator with HCBT is 82,52 %, thus HCBT can be used in switching circuits and yield good results. A supply modulator with continuous envelope tracking was also designed, which should additionally reduce heat dissipation of the power amplifier. In order to determine if the supply modulators are functioning well, they should be connected into a power amplifier system, for which any efficiency improvement needs to be verified