Abstract. Today the radar stations with
continuous wave broadband linear frequency modulated waveforms are used in
advanced driver assistance systems, ground radar systems for drone detection,
airborne systems of imagery intelligence and some other fields of activities,
thanks to their compact sizes, low power requirements and relatively low costs.
The research performed in the article shows that the effect of transmitter
phase noise suppression in the receiver output channel is present in LFM-CW
radars, and its significance depends on the distance to the target. The largest
values of suppression are reached for the signal phase noises of the targets
situated close to the radar. The expressions for calculation of the power
spectrum density of the phase noises in the output of an FMCW radar receiver
and the technique of their suppression level calculation for the specified
characteristics of the frequency synthesizer in use and radar operation range
are given in the article.
The derived ratios and dependencies allow estimating
the acceptable level of frequency synthesizer phase noise and substantiate its
choice accounting for the effect described above and for the LFM-CW radar
observation region characteristics. The fact that the consequence of the
suppression effect is the reduction of the target's demodulated echo signal
phase noise level by 10...30 dB and more depending on its distance from the
radar allows to draw a conclusion that relatively simple and low-cost frequency
synthesizers can be utilized in LFM-CW radars, thus allowing to simplify its
construction, reduce its weight, sizes and cost. Besides that, the derived
results can be used in the research of frequency modulated noises effect on
auto-correlational receivers, which are used, for example, as the LFM-CW radio
signals parameters estimation devices in radio-technical intelligence systems.
Key words: continuous wave, phase noise, power
spectrum density.
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