Power oscillator for control of waveshape and amplitude
AssigneeCubic Corporation
InventorThomas Busch-Sorensen
Life of this patent
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Abstract
An RF power oscillator for contactless card antennas shapes a carrier signal at the operating frequency utilizing a delay circuit having a number of taps for delaying the carrier signal by different lengths of time. The delayed signals are input into a buffer and output through impedance elements to a node coupled to the antenna. The resulting waveform for a square wave input signal, and equal-length delay taps, is a trapezoidal wave output. Any input wave form can be shaped in a variety of ways depending upon the combinations of delay taps used. Since the buffer drivers for each delayed wave switch state at slightly different times, the amplitude and bandwidth of emitted electromagnetic interference (EMI) is reduced for the transmission circuit.
Claims20
A power oscillator for controlling the wave shape and amplitude of an input signal to produce a desired output signal, the circuit comprising:
- a tapped delay line connected to the input signal, the tapped delay line having a plurality of taps, each tap separated from an adjacent tap to produce a plurality of delayed input signals;
- at least one buffer, the buffer comprising:
- a plurality of input lines connected to the plurality of taps;
- an input voltage line for connection to a controllable voltage source;
- and
- a plurality of output lines;
- and
- a plurality of impedance elements having first ends connected to the plurality of output lines, the plurality of impedance elements having second ends connected in parallel to an output node to produce the desired output signal.
A method for shaping and controlling the amplitude of an carrier signal, the method comprising the steps of:
- inputting the carrier signal into a tapped delay line having a plurality of taps separated by a plurality of delay distances;
- connecting each tap of the plurality of taps to a buffer of a plurality of buffers;
- connecting an impedance element to an output of each buffer of the plurality of buffers;
- connecting the outputs and impedance elements of each buffer in parallel to a single node to produce a shaped carrier signal;
- and
- supplying a supply voltage to the buffers to control an output voltage amplitude of the shaped carrier signal.
A power oscillator for controlling the wave shape and amplitude of an input signal to produce a desired output signal, the circuit comprising:
- a tapped delay line means connected to the input signal, the tapped delay line means having a plurality of taps, each tap separated from an adjacent tap to produce a plurality of delayed input signals;
- at least one buffer means, the buffer means comprising:
- a plurality of input lines connected to the plurality of taps;
- an input voltage line for connection to a controllable voltage source;
- and
- a plurality of output lines;
- and
- a plurality of same-type impedance elements having first ends connected to the plurality of output lines, the plurality of same-type impedance elements having second ends connected in parallel to an output node to produce the desired output signal.
Dependencies are inferred from the claim text.