1. Technical Field
This disclosure relates to wireless devices, more particularly to antenna used in wireless devices.
2. Background
Wireless devices send and receive signals through an antenna. For transmission, the antenna converts electrical signals from a power amplifier to electro-magnetic fields and radiates those fields out in a desired manner. When receiving, the antenna receives radiated electro-magnetic fields and converts them back to electrical signal for interpretation and operation by the wireless device.
Many different types of antenna are being used in wireless applications. A common one is an inverted ‘F’ antenna. It has two ‘fingers’ that provide electrical connection to the wireless device, and a long, straight arm that typically parallels an edge of the printed circuit board upon which the wireless device is mounted. The inverted F antenna provides good electrical performance, but has a rather large physical size. Another option is an antenna that is shaped similar to a ‘question mark,’ but the physical size is comparable to the inverted F antenna.
Wireless devices, because of their freedom from cables and wires, are particularly suited for small, portable implementations. One of the main physical constraints on making the device smaller is the size of the antenna. However, smaller antennas need to be able to match the electrical performance of the larger antenna.