Transmitter noise considerations in super-Nyquist FMCW radar design

• Published in: Electronics letters Vol. 51; no. 5; pp. 413 - 415
• Main Authors: Ash, M, Brennan, P.V
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 05.03.2015
• Subjects: CW radar; DDS frequency; direct digital synthesis; direct digital synthesiser frequency; FM radar; FMCW radar systems; frequency modulated continuous wave radar system; phase noise; phase noise curves; radar designers; radar imaging; radar receivers; radar transmitters; Radar, sonar and navigation; receiver noise leakage; receiver sensitivity; signal‐to‐noise ratio; super‐Nyquist FMCW radar design; super‐Nyquist image; thermal noise; transmitter noise; radar transmitters; super-Nyquist FMCW radar design; radar designers; frequency modulated continuous wave radar system; CW radar; transmitter noise; super-Nyquist image; DDS frequency; FM radar; receiver sensitivity; direct digital synthesis; FMCW radar systems; phase noise curves; direct digital synthesiser frequency; signal-to-noise ratio; radar receivers; radar imaging; receiver noise leakage; thermal noise; phase noise
• ISSN: 0013-5194; 1350-911X; 1350-911X
• DOI: 10.1049/el.2014.4236

A design consideration for super-Nyquist frequency modulated continuous-wave (FMCW) radar systems relating to transmitter to receiver noise leakage is introduced. Phase noise curves comparing the fundamental direct digital synthesisers frequency and its second super-Nyquist image show a significant increase in relative noise level at all offsets from the carrier. This results in a reduced transmitter signal-to-noise ratio. It is shown with a simple example that this can lead to a significant degradation in receiver sensitivity if not managed properly. A design rule-of-thumb that can be used by radar designers to avoid or mitigate this problem is provided.