Tactical Persistent Surveillance Radar with Applications by David Lynch Jr.;

Author:David Lynch Jr.; [Неизв.]
Language: eng
Format: epub
ISBN: 9781785616501
Publisher: Institution of Engineering & Technology
Published: 2018-08-30T21:00:00+00:00

5.6.1 AESA unique noise contributions

An AESA gives rise to some new forms of antenna sidelobe noise. Normally there is angular filtering between the transmitter and free space. When the last circuit element in the transmit chain is just behind the radiator, the thermal and other random noise in the T/R channel power amplifier gives rise to degraded sidelobes. Although some fraction of this noise will be correlated channel to channel, the majority will be uncorrelated and will not go away on receive. An example of the effect of uncorrelated random phase and amplitude noise on transmit sidelobes is shown in Figure 5.14. It shows an antenna pattern of a 50 × 50 element active electronic scanned array in an inter-cardinal plane with a random error of ±1% in amplitude and ±0.025 radians in phase arising from all sources of T/R noise. Obviously the receive pattern is randomly different than the transmit pattern because temperature and ripple will be different. Usually, the NF of the final T/R amplifier chain is poor because the amplifiers are hot and the noise bandwidth is large. Nonetheless, this effect is minimal compared to FM noise from the MO.

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