Method and apparatus for reducing peak to average power ratio in digital broadcasting systems

A method for reducing peak to average power ratio in a radio frequency signal, the method comprising the steps of:

• modulating a plurality of sub-carriers with a plurality of data symbol vectors to produce a first modulated signal, a first group of said subcarriers lying in upper and lower sidebands of a radio channel, and a second group of said subcarriers lying in a central band of said radio channel;
• limiting the magnitude of the first modulated signal to produce a first limited modulated signal;
• removing intermodulation products in said first limited modulated signal;
• demodulating the first limited modulated signal to recover the constellation points;
• predistorting the data symbol vectors on said first and second group of subcarriers to provide a minimum magnitude for in-phase and quadrature components thereof to produce predistorted data symbol vectors;
• modulating the plurality of carriers with the predistorted data symbol vectors to produce a second modulated signal;
• limiting the magnitude said second modulated signal to produce a second limited modulated signal;
• removing intermodulation products in said second limited modulated signal;
• and
• predistorting the data symbol vectors on said second group of subcarriers to provide a minimum magnitude for in-phase and quadrature components thereof to produce additional predistorted data symbol vectors.

A radio frequency transmitter providing reduced peak to average power ratio in a radio frequency signal, the transmitter comprising:

• means for modulating a plurality of sub-carriers with a plurality of data symbol vectors to produce a first modulated signal;
• means for limiting the magnitude of the first modulated signal to produce a first limited modulated signal;
• means for demodulating the first limited modulated signal to recover the data symbol vectors;
• means for predistorting the data symbol vectors to provide a minimum magnitude for in-phase and quadrature components thereof to produce predistorted data symbol vectors;
• means for modulating the plurality of carriers with the predistorted data symbol vectors to produce a second modulated signal;
• means for limiting the magnitude said second modulated signal to produce a second limited modulated signal;
• means for reducing intermodulation products in said second limited modulated signal.

A radio frequency transmitter providing reduced peak to average power ratio in a radio frequency signal, the transmitter comprising:

• means for modulating a plurality of sub-carriers with a plurality of data symbol vectors to produce a first modulated signal, a first group of said subcarriers lying in upper and lower sidebands of a radio channel, and a second group of said subcarriers lying in a central band of said radio channel;
• means for means for limiting the magnitude of the first modulated signal to produce a first limited modulated signal;
• means for removing intermodulation products in said first limited modulated signal;
• means for demodulating the first limited modulated signal to recover the constellation points;
• means for predistorting the data symbol vectors on said first and second group of subcarriers to provide a minimum magnitude for in-phase and quadrature components thereof to produce predistorted data symbol vectors;
• means for modulating the plurality of carriers with the predistorted data symbol vectors to produce a second modulated signal;
• means for limiting the magnitude said second modulated signal to produce a second limited modulated signal;
• means for removing intermodulation products in said second limited modulated signal;
• and
• means for predistorting the data symbol vectors on said second group of subcarriers to provide a minimum magnitude for in-phase and quadrature components thereof to produce additional predistorted data symbol vectors.