This paper design a fixed frequency source with the phase-locked loop chip ADF5355. Controlled by MCU C8051F340, the source realized the goal of miniaturized, low cost and ultra wideband. First, the phase-locked loop chip ADF5355 can realize frequency range from 54 MHz to 13600 MHz, so it can fulfill the request of the frequency range of the fixed frequency source. In addition, this source is formed by the PLL chip ADF5355, MCU C8051F340 and a LDO (Low dropout regulator) chip. Through reasonable PCB design, the size of this source is 30mm×30mm, with great practical value in engineering.