Method and system for down-converting an electromagnetic signal, and transforms for same, and aperture relationships

• US 9,118,528 B2
• Filed: 02/04/2014
• Issued: 08/25/2015
• Est. Priority Date: 10/21/1998
• Status: Expired due to Fees

• Current Assignee: ParkerVision, Inc.
• Original Assignee: ParkerVision, Inc.
• Inventors: Sorrells, David F., Bultman, Michael J., Cook, Robert W., Looke, Richard C., Moses, Charley D., Rawlins, Gregory S., Rawlins, Michael W.
• Primary Examiner(s): Bhattacharya, Sam
• Application Number:
  US14/172,392
• Publication Number:
  US 20140241464A1
• Time in Patent Office: 567 Days
• Field of Search: 455/413, 455/113, 455/118, 455/130, 455/131, 455/182.1, 455/190.1, 455/191.1, 455/313, 455/323, 455/343, 455/350, 327/113, 375/130, 375/142, 375/143, 375/150, 375/152, 375/316, 375/343
• US Class Current: 1/1
• CPC Class Codes: H03C 1/62 Modulators in which amplitude of carrier component in output is dependent upon strength of modulating signal, e.g. no carrier output when no modulating signal is present H03C1/28 - H03C1/34, H03C1/46, H03C1/48 take precedence
• CPC Class Codes: H03D 7/00 Transference of modulation from one carrier to another, e.g. frequency-changing H03D9/00, H03D11/00 take precedence; dielectric amplifiers, magnetic amplifiers, parametric amplifiers used as a frequency-changers H03F
• CPC Class Codes: H03D 7/1441 using field-effect transistors H03D7/145 takes precedence
• CPC Class Codes: H03D 7/1475 Subharmonic mixer arrangements
• CPC Class Codes: H04B 1/0025 using a sampling rate lower than twice the highest frequency component of the sampled signal for demodulation of angle-modulated signals H03D3/006
• CPC Class Codes: H04B 1/16 Circuits
• CPC Class Codes: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes
• CPC Class Codes: H04B 7/12 Frequency diversity
• CPC Class Codes: H04L 25/08 Modifications for reducing interference; Modifications for reducing effects due to line faults ; Receiver end arrangements for detecting or overcoming line faults
• CPC Class Codes: H04L 27/00 Modulated-carrier systems
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 27/12 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 27/14 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 27/148 using filters, including PLL-type filters
• CPC Class Codes: H04L 27/156 with demodulation using temporal properties of the received signal, e.g. detecting pulse width
• CPC Class Codes: H04L 27/2672 Frequency domain
• CPC Class Codes: H04L 27/3881 using sampling and digital processing, not including digital systems which imitate heterodyne or homodyne demodulation

Abstract

Methods, systems, and apparatuses, and combinations and sub-combinations thereof, for down-converting an electromagnetic (EM) signal are described herein. Briefly stated, in embodiments the invention operates by receiving an EM signal and recursively operating on approximate half cycles (½, 1½, 2½, etc) of the carrier signal. The recursive operations can be performed at a sub-harmonic rate of the carrier signal. The invention accumulates the results of the recursive operations and uses the accumulated results to form a down-converted signal. In an embodiment, the EM signal is down-converted to an intermediate frequency (IF) signal. In another embodiment, the EM signal is down-converted to a baseband information signal. In another embodiment, the EM signal is a frequency modulated (FM) signal, which is down-converted to a non-FM signal, such as a phase modulated (PM) signal or an amplitude modulated (AM) signal.

Claims

1. A system for frequency down-converting a modulated carrier signal to a baseband signal, comprising:

a first switch coupled to a first control signal which comprises a sampling aperture with a specified frequency, wherein the first switch is on and a portion of energy that is distinguishable from noise is transferred from the modulated carrier signal as an output of said first switch during the sampling aperture of the first control signal;

a first energy storage element that stores the transferred energy from the modulated carrier signal and outputs a down-converted in-phase baseband signal portion of said modulated carrier signal;

a second switch coupled to a second control signal which comprises a sampling aperture with a specified frequency, wherein the second switch is on and a portion of energy that is distinguishable from noise is transferred from the modulated carrier signal as an output of said second switch during the sampling aperture of the second control signal;

a second energy storage element that stores the transferred energy from the modulated carrier signal and outputs a down-converted inverted in-phase baseband signal portion of said modulated carrier signal;

wherein the portions of transferred energy from each of the first and second switch are integrated over time to accumulate said portions of transferred energy from which said down-converted in-phase baseband signal portion and said down-converted inverted in-phase baseband signal portion are derived; and

a first differential amplifier circuit that combines said down-converted in-phase baseband signal portion with said down-converted inverted in-phase baseband signal portion and outputs a first channel down-converted differential in-phase baseband signal.

2. The system of claim 1, wherein said modulated carrier signal includes an amplitude variation.

3. The system of claim 1, wherein said modulated carrier signal includes a phase variation.

4. The system of claim 1, wherein said modulated carrier signal includes a combination of amplitude variation and phase variation.

5. The system of claim 1, wherein the first switch is on for less than one-half cycle of the modulated carrier signal.

6. The system of claim 1, wherein the second switch is on for approximately one-tenth of a cycle of the modulated carrier signal.

7. The system of claim 1, wherein the apertures of the first and second control signals are defined by a windowing function u(t)−

u(t−

T_A), where the length of the windowing function aperture is T_A, which is equal to an approximate half cycle of the received carrier signal, S_i(t).

8. The system of claim 1, wherein the first and second control signals each control a charging and discharging cycle of their respective energy storage element by respectively controlling the first and second switching devices so that for each switching device said portion of energy that is distinguishable from noise is transferred to the respective storage element when the switch is on during the charging cycle, and a portion of the transferred energy is discharged during the discharging part of the cycle for each respective switching device when the switching device is off.

9. The system of claim 8, wherein for each respective storage element, the energy discharged during any given discharge cycle is not completely discharged, with the remaining undischarged energy from the given discharge cycle becoming an initial condition for the next charging cycle.

10. The system of claim 8, wherein each said control signal operates at an aliasing rate selected so that energy of the modulated carrier signal is sampled and differentially applied to the respective energy storage element at the frequency of the respective control signal'"'"'s aperture, and each respective energy storage element outputs, respectively, said differential down-converted in-phase baseband signal portion and said down-converted inverted in-phase baseband signal portion of said modulated carrier signal as a result of the alternate charging and discharging applied to the respective energy storage elements.

11. The system of claim 1, wherein the frequencies of the first and second apertures have periods that are two (2) percent or greater of the modulated carrier signal'"'"'s period.

12. The system of claim 1, wherein the frequencies of the first and second apertures have periods that are five (5) percent or greater of the modulated carrier signal'"'"'s period.

13. The system of claim 1, wherein the frequencies of the first and second apertures have periods that are ten (10) percent or greater of the modulated carrier signal'"'"'s period.

14. The system of claim 1, wherein the frequencies of the first and second apertures have periods that are twelve and a half (12.5) percent or greater of the modulated carrier signal'"'"'s period.

15. The system of claim 1, further comprising:

a first filter that filters said down-converted in-phase baseband signal portion; and

a second filter that filters said down-converted inverted in-phase baseband signal portion.

16. The system of claim 15, wherein the first and second filters each comprise a low-pass filter.

17. The system of claim 1, wherein said portions of transferred energy from each of the first and second switch which are integrated over time to accumulate said portions of transferred energy are integrated by a separate integration module coupled to the output of each said first and second switch.

18. The system of claim 1, wherein said first and second storage elements are capacitive storage circuits, and wherein said portions of transferred energy from each of the first and second switch which are integrated over time to accumulate said portions of transferred energy are integrated by the capacitive storage circuits as they accumulate charge during successive sampling apertures.

19. The system of claim 1, further comprising:

a third switch coupled to a third control signal which comprises a sampling aperture with a specified frequency, wherein the third switch is on and a portion of energy that is distinguishable from noise is transferred from the modulated carrier signal as an output of said third switch during the sampling aperture of the third control signal;

a third energy storage element that stores the transferred energy from the modulated carrier signal and outputs a down-converted quadrature-phase baseband signal portion of said modulated carrier signal;

a fourth switch coupled to a fourth control signal which comprises a sampling aperture with a specified frequency, wherein the fourth switch is on and a portion of energy that is distinguishable from noise is transferred from the modulated carrier signal as an output of said fourth switch during the sampling aperture of the fourth control signal;

a fourth energy storage element that stores the transferred energy from the modulated carrier signal and outputs a down-converted differential quadrature-phase baseband signal portion of said modulated carrier signal;

wherein the portions of transferred energy from each of the third and fourth switch are integrated over time to accumulate said portions of transferred energy from which said down-converted quadrature-phase baseband signal portion and said down-converted differential quadrature-phase baseband signal portion are derived; and

a second differential amplifier circuit that combines said down-converted quadrature-phase baseband signal portion with said down-converted differential quadrature-phase baseband signal portion and outputs a second channel down-converted differential quadrature-phase baseband signal.

20. The system of claim 19, wherein said modulated carrier signal includes an amplitude variation.

21. The system of claim 19, wherein said modulated carrier signal includes a phase variation.

22. The system of claim 19, wherein said modulated carrier signal includes a combination of amplitude variation and phase variation.

23. The system of claim 19, wherein the third switch is on for less than one-half cycle of the modulated carrier signal.

24. The system of claim 19, wherein the fourth switch is on for approximately one-tenth of a cycle of the modulated carrier signal.

25. The system of claim 19, wherein the apertures of the third and fourth control signals are defined by a windowing function u(t)−

u(t−

T_A), where the length of the windowing function aperture is T_A, which is equal to an approximate half cycle of the received carrier signal, S_i(t).

26. The system of claim 19, wherein the third and fourth control signals each control a charging and discharging cycle of their respective third and fourth energy storage element by respectively controlling the third and fourth switching devices so that for each third and fourth switching device a portion of energy that is distinguishable from noise is transferred to the respective third and fourth storage element when the respective switch is on during the charging cycle, and a portion of the transferred energy is discharged during the discharging part of the cycle for each respective third and fourth switching device when the respective switching device is off.

27. The system of claim 26, wherein for each respective energy storage element, the energy discharged during any given discharge cycle is not completely discharged, with the remaining undischarged energy from the given discharge cycle becoming an initial condition for the next charging cycle.

28. The system of claim 26, wherein each said third and fourth control signal operates at an aliasing rate selected so that energy of the modulated carrier signal is sampled and differentially applied to the respective energy storage element at the frequency of the respective third and fourth control signal'"'"'s aperture, and each respective third and fourth energy storage element generates, respectively, said differential down-converted in-phase baseband signal portion and said down-converted inverted in-phase baseband signal portion of said modulated carrier signal from the alternate charging and discharging applied to the respective energy storage elements.

29. The system of claim 19, wherein the frequencies of the third and fourth apertures have periods that are two (2) percent or greater of the modulated carrier signal'"'"'s period.

30. The system of claim 19, wherein the frequencies of the third and fourth apertures have periods that are five (5) percent or greater of the modulated carrier signal'"'"'s period.

31. The system of claim 19, wherein the frequencies of the third and fourth apertures have periods that are ten (10) percent or greater of the modulated carrier signal'"'"'s period.

32. The system of claim 19, wherein the frequencies of the third and fourth apertures have periods that are twelve and a half (12.5) percent or greater of the modulated carrier signal'"'"'s period.

33. The system of claim 19, further comprising:

a first filter that filters said down-converted in-phase baseband signal portion;

a second filter that filters said down-converted inverted in-phase baseband signal portion;

a third filter that filters said down-converted quadrature-phase baseband signal portion;

a fourth filter that filters said down-converted inverted quadrature-phase baseband signal portion.

34. The system of claim 33, wherein the first, second, third, and fourth filters each comprise a low-pass filter.

35. The system of claim 19, wherein said portions of transferred energy from each of the first, second, third and fourth switch which are integrated over time to accumulate said portions of transferred energy are integrated by a separate integration module coupled to the output of each said first, second, third and fourth switch respectively.

36. The system of claim 19, wherein said first, second, third and fourth storage elements are capacitive storage circuits, and wherein said portions of transferred energy from each of the first, second, third and fourth switch which are integrated over time to accumulate said portions of transferred energy are integrated by the capacitive storage circuits of the respective first, second, third and fourth storage elements as they accumulate charge during successive sampling apertures.