Method and apparatus for improving AM compatible digital broadcast analog fidelity

A combined amplitude modulated and digital signal transmission system comprising:

• a. means for transmitting an amplitude modulated signal, said amplitude modulated signal consisting of an RF amplitude modulated carrier that is amplitude modulated by a baseband signal;
• and
• b. means for producing multiple pairs of complementary digitally modulated carriers and transmitting said multiple pairs of complementary digitally modulated carriers in quadrature to said amplitude modulated signal, said multiple pairs of complementary digitally modulated carriers being separated from said amplitude modulated carrier by an equal and opposite frequency offset and having amplitudes and phases so that the addition of said multiple pairs of digitally modulated carriers results in a signal that is in phase quadrature to said amplitude modulated signal.

A method for transmitting in a combined amplitude modulated and digital signal comprising the steps of:

• a. transmitting an amplitude modulated signal, said amplitude modulated signal consisting of an RF amplitude modulated carrier that is amplitude modulated by a baseband signal;
• and
• b. producing a complementary pair of digitally modulated carriers and transmitting said complementary pair of digitally modulated carriers in quadrature to said amplitude modulated signal, said complementary pair of digitally modulated carriers being separated from said amplitude modulated carrier by an equal and opposite frequency offset and having phases and amplitudes so that the addition of said complementary pair of digitally modulated carriers is in phase quadrature to said amplitude modulated signal.

A method for transmitting an amplitude modulated signal and a digital signal comprising the steps of:

• a. transmitting an amplitude modulated signal, said amplitude modulated signal consisting of an RF amplitude modulated carrier that is amplitude modulated by a baseband signal;
• and
• b. producing multiple pairs of complementary digitally modulated carriers and transmitting said multiple pairs of complementary digitally modulated carriers in quadrature to said amplitude modulated signal, said multiple pairs of complementary digitally modulated carriers being separated from said amplitude modulated carrier by an equal and opposite frequency offset and having phases and amplitudes so that the addition of said multiple pairs of complementary digitally modulated carriers is in phase quadrature to said amplitude modulated signal.