A multidirectional feed and flush-mounted surface wave antenna

The present invention relates to a multidirectional feed which can be used by itself or preferably incorporated within a surface wave structure to form a flush-mounted antenna on, for example, a mobile unit. The feed arrangement comprises a ground plane (l0) including an annular cavity (ll) with a smaller annular slot (l2). The annular slot is connected by multiple, spaced-apart, leads (l4) to an associated transceiver. The annular cavity is also formed to prevent both a shorting of the radio waves therein and the radio waves from propagating away from the cavity in a direction opposite the slot. A surface wave structure is disposed preferably with the feed centrally mounted and can comprise any suitable structure including annular corrugations and/or a dielectric layer to provide a flush-mounted antenna arrangement which provides radiation in azimuth in all directions with moderate elevation gain.