Quadrature modulation with reduced phase-error distortion
AssigneeTropian, Inc.
InventorRichard W. D. Booth
Life of this patent
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Abstract
A system and method of modulation is described that initially over-modulates with an information signal at a scale that is N times an intended modulation scale and then subsequently, frequency-divides the over-modulated signal by the same factor of N to generate a modulated signal having the intended modulation scale wherein distortion of the resulting modulated signal is reduced by a factor of 20 log10(N)dB.
Claims17
A method of modulating an information signal to generate an essentially constant-envelope modulated signal having an intended modulation scale and an intended carrier frequency, said method comprising the steps of:
- quadrature over-modulating with said information signal to generate a constant-envelope over-modulated signal having a modulation scale that is N times the intended modulation scale;
- and
- frequency-dividing a derivative of said constant-envelope over-modulated signal by a factor of N;
- wherein signal distortion that is created while quadrature over-modulating is logarithmically reduced by a factor of 20 log10(N)dB.
A method of modulation for generating a constant-envelope quadrature modulated signal from an information signal, said constant-envelope modulated signal having an intended modulation scale and an intended carrier frequency, said method essentially comprising the steps of:
- using said information signal to generate constant-envelope over-modulated quadrature signal components, said over-modulated quadrature signal components having an associated modulation scale that is N times that of said intended modulation scale;
- mixing said over-modulated quadrature signal components with first and second carrier signals each having an associated carrier frequency rate that is N times said intended carrier frequency rate to generate first and second over-modulated signals;
- summing said first and second over-modulated signals to generate a single, over-modulated constant-envelope signal;
- converting said single, over-modulated signal into a digital signal;
- and
- digitally frequency-dividing said digital signal by a factor of N to generate said constant-envelope quadrature modulated signal having said associated intended modulation scale and said intended carrier frequency.
The system of modulation for generating a constant-envelope quadrature over-modulated signal from an information signal, said over-modulated signal having an intended modulation scale and an intended carrier frequency comprising:
- a quadrature over-modulator for generating a constant-envelope over-modulated quadrature signal from an information signal, said over-modulated quadrature signal having an associated modulation scale that is N times that of said intended modulation scale;
- a mixer for mixing I and Q components of said constant-envelope over-modulated quadrature signal with first and second carrier signals, respectively, so as to generate first and second over-modulated signals having an associated carrier frequency rate that is N times said intended carrier frequency rate;
- a summer for summing said first and second over-modulated signals to generate a single, over-modulated signal;
- a convertor for converting said single, over-modulated signal into a digital signal having an associated frequency;
- and
- a digital frequency divider for digitally dividing said associated frequency of said digital signal by N to generate said constant-envelope modulated signal having said intended modulation scale and said intended carrier frequency.
Dependencies are inferred from the claim text.