One conventional antenna type is known as a four arm helical spiral, wherein transmit and receive antenna elements may be interleaved with one another. This type of antenna provides a generally hemispherical coverage region. As a result, and if such an antenna type were to be employed as an antenna for a user terminal in a satellite communication system, in particular a non-geosynchronous orbit satellite communication system, the gain for low satellite elevation angles is greater than for a satellite that is directly overhead, thus compensating to some degree for the greater path loss to a satellite near the horizon.
However, one disadvantage of conventional four arm helical spiral antennas is that they tend to be physically larger than is customary for hand-held user terminals, such as cellular telephones. A second disadvantage is that loss between the active elements and the antennas tends to be greater than desirable. A further disadvantage is an undesirable loss that can result from mutual coupling between interleaved transmit and receive antenna elements.