Editing Phased array (section)

=== Passive phased array ===
[[Passive phased array]]s typically use large amplifiers that produce all of the microwave transmit signal for the antenna. Phase shifters typically consist of waveguide elements controlled by magnetic field, voltage gradient, or equivalent technology.<ref>{{cite web|url=http://scholarworks.sjsu.edu/cgi/viewcontent.cgi?article=5082&context=etd_theses&sei-redir=1&referer=http%3A%2F%2Fwww.google.com|title=YIG-sphere-based phase shifter for X-band phased array applications|publisher=Scholarworks|url-status=live|archive-url=https://web.archive.org/web/20140527212406/http://scholarworks.sjsu.edu/cgi/viewcontent.cgi?article=5082&context=etd_theses&sei-redir=1&referer=http%3A%2F%2Fwww.google.com|archive-date=2014-05-27}}</ref><ref>{{cite web|url=http://www.microwaves101.com/encyclopedia/phaseshifters_ferro.cfm|title=Ferroelectric Phase Shifters|publisher=Microwaves 101|url-status=live|archive-url=https://web.archive.org/web/20120913014513/http://www.microwaves101.com/encyclopedia/phaseshifters_ferro.cfm|archive-date=2012-09-13}}</ref>

The phase shift process used with passive phased arrays typically puts the receive beam and transmit beam into diagonally opposite quadrants. The sign of the phase shift must be inverted after the transmit pulse is finished and before the receive period begins to place the receive beam into the same location as the transmit beam. That requires a phase impulse that degrades sub-clutter visibility performance on Doppler radar and Pulse-Doppler radar. As an example, [[Yttrium iron garnet]] phase shifters must be changed after transmit pulse quench and before receiver processing starts to align transmit and receive beams. That impulse introduces FM noise that degrades clutter performance.

Passive phased array design is used in the AEGIS Combat System<ref>{{cite web|url=http://apps.dtic.mil/dtic/tr/fulltext/u2/a460426.pdf|title=Total Ownership Cost Reduction Case Study: AEGIS Radar Phase Shifters|publisher=Naval Postgraduate School|url-status=live|archive-url=https://web.archive.org/web/20160303234942/http://www.dtic.mil/dtic/tr/fulltext/u2/a460426.pdf|archive-date=2016-03-03}}</ref> for [[Direction of arrival|direction-of-arrival]] estimation.