Design, development and linearity testing of synthesized FMCW RF source

This paper presents the design and development of an X-band LFM sweep generator. The proposed waveform generator utilizes a fully synthesized hybrid architecture that combines the advantages of both DDS and PLL. The architecture consists of a synthesized PLL source with DDS as a reference generator. At start up, the PLL is programmed for a fixed frequency while DDS is programmed for a linear triangular sweep. The PLL follows the reference that results in a linear RF sweep. This paper also presents the linearity testing of the synthesized FMCW RF source. The test was performed on a down-converted signal using a high sampling oscilloscope. The measured results indicate that with the proposed scheme, a very linear chirp can be generated at X band that is very useful for radar applications.