Abstract: A digital pen comprising a skeleton and a removable skin: the skeleton holding together in fixed relationship: an electric circuit; an acoustic transmitter, detached from said electric circuit, and configured to transmit acoustic signals; and a resilient holder, configured to mechanically press said electric circuit into electrical contact with said transmitter, so as to electrically connect said electric circuit and said transmitter; and the removable skin comprising a housing fitting over said skeleton.

Abstract: A digital pen comprising: an electric circuit, an acoustic transmitter, detached from the electric circuit, and configured to transmit acoustic signals, and a resilient holder, configured to mechanically press the electric circuit into electrical contact with the transmitter, so as to electrically connect the electric circuit and the transmitter.

Abstract: A wireless telecommunication system and method including at least two transmit antennae and means for implementing a downlink switched sub-channels diversity scheme during transmission. The method includes splitting a total bandwidth allocated for transmission of a transmitted signal to individual sub-channels or groups of sub-channels; boosting each of the sub-channels or groups of sub-channels; and routing each of the sub-channels or groups of sub-channels to a different transmit antenna.

Abstract: A digital pen comprising: an electric circuit, an acoustic transmitter, detached from the electric circuit, and configured to transmit acoustic signals, and a resilient holder, configured to mechanically press the electric circuit into electrical contact with the transmitter, so as to electrically connect the electric circuit and the transmitter.

Abstract: A digital pen comprising: an electric circuit, an acoustic transmitter, detached from the electric circuit, and configured to transmit acoustic signals, and a resilient holder, configured to mechanically press the electric circuit into electrical contact with the transmitter, so as to electrically connect the electric circuit and the transmitter.

Abstract: A receiving unit for receiving an acoustic signal from a digital pen, comprises: at least two ultrasound receivers, for receiving ultrasound signals from the digital pen; an electric circuit connected to said ultrasound receivers, and configured to extract ultrasound signals received by said ultrasound receivers, to enable tracking a position of said pen, and a biased clip for holding paper in fixed relationship to said ultrasound receivers. The clip may be metal, and alignment and location features may be provided for fitting sheets of paper for writing.

Abstract: A receiving unit for receiving an acoustic signal from a digital pen, comprises: a housing; at least two ultrasound receivers, for receiving ultrasound signals from the digital pen, the ultrasound receivers comprising electret microphones, the electret microphones being located in location holes in the housing; and an electric circuit connected to said electret microphones, to extract ultrasound signals received by the ultrasound receivers. An attachment device may removably attach the receiving unit to another item.

Abstract: A digital pen comprising a skeleton and a removable skin: the skeleton holding together in fixed relationship: an electric circuit; an acoustic transmitter, detached from said electric circuit, and configured to transmit acoustic signals; and a resilient holder, configured to mechanically press said electric circuit into electrical contact with said transmitter, so as to electrically connect said electric circuit and said transmitter; and the removable skin comprising a housing fitting over said skeleton.

Abstract: A wireless telecommunication system and method including at least two transmit antennae and means for implementing a downlink switched sub-channels diversity scheme during transmission. The method includes splitting a total bandwidth allocated for transmission of a transmitted signal to individual sub-channels or groups of sub-channels; boosting each of the sub-channels or groups of sub-channels; and routing each of the sub-channels or groups of sub-channels to a different transmit antenna.

Abstract: A digital pen comprising: an electric circuit, an acoustic transmitter, detached from the electric circuit, and configured to transmit acoustic signals, and a resilient holder, configured to mechanically press the electric circuit into electrical contact with the transmitter, so as to electrically connect the electric circuit and the transmitter.

Abstract: A modem for more efficiently processing a received analog signal into a digital output. The modem preferably estimates the carrier frequency offset in at least one stage, by receiving a synchronization field divided into at least two portions, calculating a difference of the phase between the portions, and then calculating the frequency offset from the phase difference. More preferably, the modem estimates the carrier frequency offset in two stages, with a first stage being a initial frequency estimate of the offset.

Abstract: A modem for more efficiently processing a received analog signal into a digital output. The modem preferably features an adaptive equalizer with coefficients which are saved and reused for processing of subsequent analog signals, in order to reduce the time required to reach convergence. In addition, preferably the modem features an automatic carrier frequency control which adjusts the sampled digital signal according to both the carrier phase offset and the carrier frequency offset. Again, in order to process the signal more quickly and efficiently, preferably the carrier frequency offset is stored and reused for processing subsequent signals.