Novatel Communications Ltd.

Ashfaq Choudhury

Humphrey Gordon

A system uses a charge storage unit to produce shaped pulses in response to an incoming digital signal. The system detects transitions or patterns in the digital signal and produces a charging waveform that controls the charge maintained in the charge storage unit, and thus, the instantaneous value of an output voltage produced by the unit. The charging waveform is, in turn, controlled by transition characteristics or counts that are stored, respectively, in transition memories. In the case of a binary transmission the memories contain rising and falling characteristics. These memories are addressed by addresses generated in response to the detection of a pattern, or as appropriate, a transition in the incoming digital signal. The charging waveform may be a series of pulses with varying widths, a signal that has a variable duty cycle, or a varying pulse count. The charging waveform controls the charging of capacitors in the charge storage unit, which consists essentially of cascaded low pass filters. In a preferred embodiment, a buffer amplifier is placed between the low pass filters, to isolate them and allow the system to control more easily the amplitudes of the shaped pulses.

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Calgary, Canada

Ashfaq Choudhury