IQ modulation systems and methods that use separate phase and amplitude signal paths
DCFirst Claim
1. A modulation system comprising:
- a digital signal processor that generates in-phase, quadrature-phase and amplitude signals from a baseband signal;
a modulator that modulates the in-phase and quadrature-phase signals to produce a modulated signal;
a phase locked loop that is responsive to the modulated signal, the phase locked loop including a controlled oscillator having a controlled oscillator output; and
an amplifier having a signal input, an amplitude control input and an output, wherein the signal input is responsive to the controlled oscillator output and the amplitude control input is responsive to the amplitude signal;
wherein the in-phase and quadrature-phase signals are normalized in-phase and quadrature-phase signals such that the modulated signal is a constant amplitude modulated signal; and
wherein the digital signal processor generates the normalized in-phase signal as one of a cosine and a sine of an angle theta and generates the normalized quadrature-phase signal as the other of a cosine and a sine of the angle theta, where theta is an angle whose tangent is the quadrature-phase signal divided by the in-phase signal.
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Abstract
A digital signal processor generates in-phase, quadrature-phase and amplitude signals from a baseband signal. A modulator modulates the in-phase and quadrature-phase signals to produce a modulated signal. A phase locked loop is responsive to the modulated signal. The phase locked loop includes a controlled oscillator having a controlled oscillator input. An amplifier includes a signal input, amplitude control input and an output. The signal input is responsive to the controlled oscillator output and the amplitude control input is responsive to the amplitude signal. The in-phase and quadrature-phase signals may be normalized in-phase and quadrature-phase signals. Alternatively, a phase tracking subsystem may be provided that is responsive to the quadrature modulator to produce a phase signal that is responsive to phase changes in the modulated signal and that is independent of amplitude changes in the modulated signal. An amplitude tracking subsystem also may be provided that is responsive to the modulator to produce an amplitude system that is responsive to amplitude changes in the modulated signal and that is independent of the phase changes in the modulated signal. An amplifier has a signal output, an amplitude control input and an output. The signal input is responsive to the phase signal and the amplitude control input is responsive to the amplitude signal.
51 Citations
32 Claims
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1. A modulation system comprising:
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a digital signal processor that generates in-phase, quadrature-phase and amplitude signals from a baseband signal;
a modulator that modulates the in-phase and quadrature-phase signals to produce a modulated signal;
a phase locked loop that is responsive to the modulated signal, the phase locked loop including a controlled oscillator having a controlled oscillator output; and
an amplifier having a signal input, an amplitude control input and an output, wherein the signal input is responsive to the controlled oscillator output and the amplitude control input is responsive to the amplitude signal;
wherein the in-phase and quadrature-phase signals are normalized in-phase and quadrature-phase signals such that the modulated signal is a constant amplitude modulated signal; and
wherein the digital signal processor generates the normalized in-phase signal as one of a cosine and a sine of an angle theta and generates the normalized quadrature-phase signal as the other of a cosine and a sine of the angle theta, where theta is an angle whose tangent is the quadrature-phase signal divided by the in-phase signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A modulation system comprising:
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a quadrature modulator that modulates in-phase and quadrature-phase signals to produce a modulated signal;
a phase tracking subsystem that is responsive to the quadrature modulator to produce a phase signal that is responsive to phase changes in the modulated signal and that is independent of amplitude changes in the modulated signal;
an amplitude tracking subsystem that is responsive to the modulator to produce an amplitude signal that is responsive to amplitude changes in the modulated signal and that is independent of phase changes in the modulated signal; and
an amplifier having a signal input, an amplitude control input and an output, wherein the signal input is responsive to the phase signal and the amplitude control input is responsive to the amplitude signal. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A modulation method comprising:
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generating normalized in-phase, normalized quadrature-phase and normalized amplitude signals from a baseband signal;
modulating the normalized in-phase and quadrature-phase signals to produce a constant amplitude modulated signal;
phase locking the constant amplitude modulated signal to produce a phase locked signal; and
amplifying the phase locked signal at a gain that is varied in response to the normalized amplitude signal;
wherein the generating a normalized in-phase signal, a normalized quadrature-phase signal and a normalized amplitude signal from a baseband signal comprises;
generating an in-phase signal and a quadrature-phase signal from the baseband signal;
generating an angle theta whose tangent is the quadrature-phase signal divided by the in-phase signal;
generating the normalized in-phase signal as one of a sine and a cosine of the angle theta; and
generating the normalized quadrature signal as the other of a sine and a cosine of the angle theta. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A modulation method comprising:
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modulating in-phase and quadrature signals to produce a modulated signal;
producing a phase signal from the modulated signal that is responsive to phase changes in the modulated signal and that is independent of amplitude changes in the modulated signal;
producing an amplitude signal from the modulated signal that is responsive to amplitude changes in the modulated signal and that is independent of phase changes in the modulated signal; and
amplifying the phase signal at a gain that is varied in response to the amplitude signal. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32)
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Specification