GENERALIZED FREQUENCY MODULATION

• US 20120224658A1
• Filed: 05/07/2012
• Published: 09/06/2012
• Est. Priority Date: 08/05/2009
• Status: Active Grant

• Current Assignee: Aerospace Corporation
• Original Assignee: Aerospace Corporation
• Inventors: Kumar, Rajendra
• Granted Patent: US 8,638,890 B2
• Time in Patent Office: Days
• US Class Current: 375/340
• CPC Class Codes: H04L 27/12 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 27/156 with demodulation using temporal properties of the received signal, e.g. detecting pulse width

Abstract

A receiver may comprise a complex mixer for converting the modulated signal to a complex modulated signal comprising a first in-phase component and a first quadrature component. The receiver may further comprise a digital demodulator. The digital demodulator may comprise at least one processor circuit programmed for applying a phase differencer for generating an output function in terms of a phase difference of the complex modulated signal. Applying the phase differencer may comprise converting the first in-phase component to a function of a phase difference of the first in-phase component expressed in digital time, and converting the first quadrature component to a function of the phase difference of the first quadrature component expressed in digital time. The at least one processor circuit of the digital demodulator may also be programmed for applying a four quadrant inverse tangent to the output function to generate the information signal.

Claims

1. A receiver for demodulating an information signal from a modulated signal, the receiver comprising:

a complex mixer for converting the modulated signal to a complex modulated signal comprising a first in-phase component and a first quadrature component; and

a digital demodulator in communication with the complex mixer, wherein the demodulator comprises at least one processor circuit programmed for;

applying a phase differencer for generating an output function in terms of a phase difference of the complex modulated signal, wherein applying the phase differencer comprises;

converting the first in-phase component to a function of a phase difference of the first in-phase component expressed in digital time; and

converting the first quadrature component to a function of the phase difference of the first quadrature component expressed in digital time; and

applying a four quadrant inverse tangent to the output function to generate the information signal.

2. The receiver of claim 1, wherein the phase differencer comprises a plurality of cascaded stages, wherein each stage is programmed to convert an input in-phase component to a function of a phase difference of the input in-phase component and to convert an input quadrature component to a phase difference of an input quadrature component, wherein the input in-phase component for the first stage of the plurality of cascaded stages is the first in-phase component and wherein the output of the last stage of the plurality of cascaded stages is the output function.

3. The receiver of claim 2, wherein the plurality of cascaded stages comprises two stages.

4. The receiver of claim 1, further comprising a down converter in communication with the complex mixer for shifting the frequency of the modulated signal to an intermediate frequency.

5. The receiver of claim 1, further comprising a first analog-to-digital converter for digitizing the first in-phase signal and a second analog-to-digital converter for digitizing the first quadrature signal.

6. The receiver of claim 1, wherein the function of the phase difference of the first in-phase component expressed in digital time is given by:

x_i+1(n)=x_i(n)x_i(n−

1)+y_i(n)y_i(n−

1)

wherein;

n is digital time;

x_i+1(n) is the function of the phase difference of the first in-phase component;

x_i(n) is the in-phase signal; and

y_i(n) is the quadrature signal.

7. The receiver of claim 1, wherein the function of the phase difference of the first quadrature component expressed in digital time is given by:

y_i+1(n)=y_i(n)x_i(n−

1)−

x_i(n)y_i(n−

1)

wherein;

n is digital time;

y_i+1(n) is function of the phase difference of the first quadrature component;

x_i(n) is the in-phase signal; and

y_i(n) is the quadrature signal.

8. The receiver of claim 1, further comprising a de-emphasis filter in communication with the digital demodulator for filtering the information signal.

9. The receiver of claim 1, further comprising an antenna in communication with the complex mixer, the antenna for receiving the modulated signal.

10. A method of demodulating a modulated signal to obtain an information signal, the method comprising:

converting the modulated signal to a complex modulated signal comprising a first in-phase component and a first quadrature component; and

generating an output function in terms of a phase difference of the complex modulated signal, wherein applying the generating is performed with at least one programmed processor circuit and wherein the generating comprises;

converting the first in-phase component to a function of a phase difference of the first in-phase component expressed in digital time; and

converting the first quadrature component to a function of the phase difference of the first quadrature component expressed in digital time; and

applying a four quadrant inverse tangent to the output function to generate the information signal.

11. The method of claim 10, wherein the generating further comprises applying a plurality of cascaded differencer stages, wherein each stage is programmed to convert an input in-phase component to a function of a phase difference of the input in-phase component and to convert an input quadrature component to a phase difference of an input quadrature component, wherein the input in-phase component for the first stage of the plurality of cascaded stages is the first in-phase component and wherein the output of the last stage of the plurality of cascaded stages is the output function.

12. The method of claim 11, wherein the plurality of cascaded stages comprises two stages.

13. The method of claim 10, further comprising shifting the frequency of the modulated signal to an intermediate frequency.

14. The method of claim 10, wherein the function of the phase difference of the first in-phase component expressed in digital time is given by:

x_i+1(n)=x_i(n)x_i(n−

1)+y_i(n)y_i(n−

1)

wherein;

n is digital time;

x_i+1(n) is the function of the phase difference of the first in-phase component;

x_i(n) is the in-phase signal; and

y_i(n) is the quadrature signal.

15. The method of claim 10, wherein the function of the phase difference of the first quadrature component expressed in digital time is given by:

y_i+1(n)=y_i(n)x_i(n−

1)−

x_i(n)y_i(n−

1)

wherein;

n is digital time;

y_i+1(n) is function of the phase difference of the first quadrature component;

x_i(n) is the in-phase signal; and

y_i(n) is the quadrature signal.

16-20. -20. (canceled)