Joined: 03 Aug 2017
|Posted: Thu Aug 03, 2017 1:07 am Post subject: Reflected current on a patch antenna
I have a few questions about the current on a standard lambda/2 rectangular patch antenna. If the antenna is designed correctly, then the interface at the feed and the patch are (ideally) matched; all current/voltage is transferred to the patch over some arbitrary bandwidth.
Continuing, maybe this is where I get it all wrong...
Initially, there is no current present on the patch. When the source is providing a voltage such that a current is produced, in due time the front of the current, maybe a better way to say that is the current "wavefront", will eventually make its way to the patch, and hit the open end and reflect back toward the feed; the rest of the current wave continues in time and continuously reflects off the open end.
but these forward and reverse currents obey linear superposition; that is to say that they don't truly cancel each other out, but at certain times and positions on the antenna structure the net current is 0, max, min, and everything in between. Since the feed is matched, the reflected current shows up on the feed line and continues towards the source. So does the feed line also exhibit a standing wave pattern since the feed/patch interface presents no reflection in either direction?