A novel frequency down-converter design at X-band for LEO satellite ground station using single conversion

Abstract This paper presents the design and implementation of a broadband down-converter system using the AWR (Advancing the Wireless Revolution) modeling and Microwave Office tool. The radio frequency (RF) signal coming to the antenna interface requires a frequency down-converter to be lowered to the intermediate frequency (IF) band. It includes mixing blocks, oscillators, amplifiers, step attenuators, isolators, and filters. The input frequency band (RF) is 8250 ± 250 MHz, while the output frequency (IF) band is 720 ± 200 MHz. The gain dynamic range of the circuit is expanded through the use of digital attenuators. It is a superheterodyne down-conversion circuit, combining the IF band to produce the desired RF spectrum in one pass. Two phase-locked oscillators are used at the local oscillator port of the mixer, one providing a single frequency, while the other has a programmable frequency synthesizer with 1 MHz steps in the frequency range from 7280 to 7780 MHz.