Coherent AM demodulator using a weighted LSB/USB sum for interference mitigation

A method of processing an AM radio signal comprising the steps of:

• receiving an AM radio signal including an upper sideband portion and a lower sideband portion:
• demodulating the upper sideband portion and the lower sideband portion to produce a demodulated upper sideband signal and a demodulated lower sideband signal;
• weighting the demodulated upper sideband signal and the demodulated lower sideband signal using a weighting factor that varies in response to signal to noise ratio in the demodulated upper sideband signal and the demodulated lower sideband signal to produce a weighted demodulated upper sideband signal and a weighted demodulated lower sideband signal;
• and
• combining the weighted demodulated upper sideband signal and the weighted demodulated lower sideband signal to produce an output signal;
• wherein the step of weighting the demodulated upper sideband signal and the demodulated lower sideband comprises the steps of multiplying the demodulated upper sideband signal by the weighting factor;
• and multiplying the demodulated lower sideband signal by one minus the weighting factor.

A demodulator for processing an AM radio signal comprising:

• means for demodulating the upper sideband portion and the lower sideband portion of an AM radio signal to produce a demodulated upper sideband signal and a demodulated lower sideband signal;
• means for weighting the demodulated upper sideband signal and the demodulated lower sideband signal using a weighting factor that varies in response to signal to noise ratio in the demodulated upper sideband signal and the demodulated lower sideband signal to produce a weighted demodulated upper sideband signal and a weighted demodulated lower sideband signal;
• and
• means for combining the weighted demodulated upper sideband signal and the weighted demodulated lower sideband signal;
• wherein the means for weighting the demodulated upper sideband signal and the demodulated lower sideband signal comprises means for multiplying the demodulated upper sideband signal by the weighting factor, and means for multiplying the demodulated lower sideband signal by one minus the weighting factor.

A receiver for processing an AM radio signal comprising:

• means for receiving an AM radio signal including an upper sideband portion and a lower sideband portion;
• means for demodulating the upper sideband portion and the lower sideband portion to produce a demodulated upper sideband signal and a demodulated lower sideband signal;
• means for weighting the demodulated upper sideband signal and the demodulated lower sideband signal using a weighting factor that varies in response to signal to noise ratio in the demodulated upper sideband signal and the demodulated lower sideband signal to produce a weighted demodulated upper sideband signal and a weighted demodulated lower sideband signal;
• and
• means for combining the weighted demodulated upper sideband signal and the weighted demodulated lower sideband signal to produce an output signal;
• wherein the means for weighting the demodulated upper sideband signal and the demodulated lower sideband sianal comprises means for multiplying the demodulated upper sideband signal by the weighting factor, and means for multiplying the demodulated lower sideband signal by one minus the weighting factor.

A demodulator for processing an AM radio signal comprising:

• a circuit for demodulating the upper sideband portion and the lower sideband portion of an AM radio signal to produce a demodulated upper sideband signal and a demodulated lower sideband signal;
• a circuit for weighting the demodulated upper sideband signal and the demodulated lower sideband signal using a weighting factor that varies in response to signal to noise ratio in the demodulated upper sideband signal and the demodulated lower sideband signal to produce a weighted demodulated upper sideband signal and a weighted demodulated lower sideband signal;
• and
• a combiner for combining the weighted demodulated upper sideband signal and the weighted demodulated lower sideband signal;
• p1 wherein the circuit for weighting the demodulated upper sideband signal and the demodulated lower sideband signal multiplies the demodulated upper sideband signal by the weighting factor, and multiplies the demodulated lower sideband signal by one minus the weighting factor.

A receiver for processing an AM radio signal comprising:

• an input for receiving an AM radio signal including an upper sideband portion and a lower sideband portion;
• a demodulator for demodulating the upper sideband portion and the lower sideband portion to produce a demodulated upper sideband signal and a demodulated lower sideband signal;
• a circuit for weighting the demodulated upper sideband signal and the demodulated lower sideband signal using a weighting factor that varies in response to signal to noise ratio in the demodulated upper sideband signal and the demodulated lower sideband signal to produce a weighted demodulated upper sideband signal and a weighted demodulated lower sideband signal;
• and
• a combiner for combining the weighted demodulated upper sideband signal and the weighted demodulated lower sideband signal to produce an output signal;
• wherein the circuit for weighting the demodulated upper sideband signal and the demodulated lower sideband signal multiplies the demodulated upper sideband signal by the weighting factor, and multiplies the demodulated lower sideband signal by one minus the weighting factor.

A method of processing an AM radio signal comprising the steps of:

• splitting the AM radio signal into real and imaginary components;
• taking a Hilbert Transform of the imaginary component to produce a transformed signal;
• using the real component and the transformed signal to calculate a weighting factor;
• mixing the transformed signal with the weighting factor to produce a weighted transformed signal;
• and
• combining the weighted transformed signal and the real component to produce an output signal.

A receiver for processing an AM radio signal comprising:

• a splitter for splitting the AM radio signal into real and imaginary components;
• a processor for taking a Hilbert Transform of the imaginary component to produce a transformed signal and using the real component and the transformed signal to calculate a weighting factor;
• a mixer for mixing the transformed signal with the weighting factor to produce a weighted transformed signal;
• and
• a combiner for combining the weighted transformed signal and the real component to produce an output signal.