Direct digital polar modulator
OwnerAlexander Wayne Hietalainventor
Life of this patent
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Abstract
A polar modulator creates an amplitude signal and a frequency signal and digitally adjusts the signals so that the frequency and amplitude signals arrive at the power amplifier at the appropriate times. A digital predistortion filter is applied to the frequency signal. The frequency signal is then provided to a single port of a fractional N divider in a phase locked loop. The output of the phase locked loop drives an input of the power amplifier while the amplitude signal is converted to an analog signal and controls the power supply input of the power amplifier.
Claims17
A modulator circuit comprising:
- a polar converter adapted to generate a digital frequency signal and a digital amplitude signal from an incoming signal;
- a digital predistortion filter adapted to filter the digital frequency signal from the polar converter;
- and
- a phase locked loop comprising a divider adapted to receive an output from said digital predistortion filter, said phase locked loop generating an output adapted to comprise an input for a power amplifier.
A method of modulating a signal prior to transmission, comprising:
- mapping a bit stream to I and Q components;
- converting the I and Q components to a frequency signal and an amplitude signal;
- digitally predistorting the frequency signal with a first transfer function to create a distorted frequency signal;
- passing the distorted frequency signal to a divider in a phase locked loop to create an input signal, said phase locked loop having a second transfer function, said first transfer function being approximately the inverse of the second transfer function;
- and
- passing the amplitude and input signal to a power amplifier for transmission.
A hardware implemented modulator circuit comprising:
- a switch adapted to switch the modulator circuit between a GMSK mode and an EDGE mode;
- a serial data interface adapted to receive a bit stream of data representing a signal to be transmitted and output the same;
- a GMSK modulator adapted to receive the bit stream of data when in said GMSK mode;
- a polar modulator adapted to receive the bit stream of data when in said EDGE mode and comprising:
- a mapping module adapted to map the bit stream of data onto I and Q components;
- and
- a polar converter adapted to convert the I and Q components into frequency and amplitude signals;
- a digital predistortion filter imposing a first transfer function on a frequency signal received from either said polar converter or said GMSK modulator;
- a phase locked loop having a second transfer function, said first transfer function being approximately the inverse of said second transfer function, said phase locked loop comprising a fractional N divider, said fractional N divider receiving an output from said digital predistortion filter;
- and
- a power amplifier receiving an amplitude signal and the output of the phase locked loop.
Dependencies are inferred from the claim text.