Analysis and improved design considerations for airborne pulse Doppler radar signal processing in the detection of hazardous windshear

Original publisher: Hampton, Va. : National Aeronautics and Space Administration, Langley Research Center ; [Springfield, Va. : For sale by the National Technical Information Service, 1990] OCLC Number: (OCoLC)25150793 Subject: Doppler radar. Excerpt: ... 5 usually two highly stable oscillators, i.e, stable local oscillator ( STALO ) and coherent oscillator ( COHO ), are needed in the heterodyne detection system to retain the phase coherence. Both oscillators are used to provide a transmitted and reference signal, but the stability problem of the COHO is not so serious compared with that of the STALO since the frequency range of the COHO is several orders of magnitude less than that of the STALO. Therefore it is considered that the STALO plays a major role in the pulse-to-pulse system phase stability problem. Of course, there may be many other factors increasing the system phase noise such as the mismatch problem in obtaining I, Q data [ 4 ]. Phase instability factors will degrade Doppler frequency resolution and the spectrum moment estimation quality. This phase noise effect may also severely limit the capability of clutter rejection filtering by spreading the clutter signal over the Doppler signal bandwidth as seen in Figure 3. Although Doppler radar operation was successful in some other experimental cases [ 5 ], [ 6 ], future application of Doppler weather radar where higher spatial resolution is needed may require higher Doppler resolution and more accurate estimation of spectral moments [ 50 ], [ 51 ]. A fundamental problem is quantification of the effect of radar system phase noise on the performance of Doppler weather radar. However, it is really difficult to investigate all phase noise contributing factors separately in a radar system. Thus, a general systematic approach was developed in