Abstract: A wireless interface device is used to RF communicate between a computer system and input devices comprising a keyboard and a mouse. The interface device comprises a radio transmitter and receiver, wherein a modem encodes data to be sent by the radio transmitter and decodes data received by the radio receiver. A baseband circuit encrypts data to be transmitted and decrypts received data. The wireless interface device has power saving functions to extend the battery life of the input device and has the capability to automatically select between several communication frequencies or channels as well as automatically select between RF data rates.

Abstract: Described is the transformation of a mono-band antenna into a or multi-band antenna by adding matching circuits, in either serial or parallel fashion, to a mono-band antenna. The matching circuits contain reactive elements such as inductors and capacitors which create impedance matching for two or more frequency bands. These multi-band loop antennas can be used for frequencies extending from a few megahertz to several hundred megahertz. The method of tuning such multi-band antennas is also described.

Abstract: Methods and systems to determine the position of objects indoors or in confined areas are disclosed. A multitude of broadcast stations are transmitting an omni-directional reference signal and directional signals having each a phase-shift depending upon their specific direction. The objects whose positions are to be identified have a transponder and a means to measure the phase-shift between the omni-directional reference signal and a directional signal received. The measured time-difference indicating the relative direction to the broadcast station, which has sent the directional signal, is sent back to the broadcast station. The absolute position of the object can be determined by the results of an angular measurement of a second broadcast station. The broadcast stations can communicate amongst each other. A post-processing unit can initiate actions according to the position of an object identified.