Method and system for down-converting and electromagnetic signal, and transforms for same
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.
1. A method for down-converting an electromagnetic signal, comprising the steps of:
(1) performing with a finite time integrating module a finite time integrating operation on a portion of a carrier signal;
(2) accumulating the result of the finite time integrating operation of step (1); and
(3) repeating steps (1) and (2) for additional portions of the carrier signal, whereby the accumulation results form a down-converted signal.
2. The method according to claim 1 , wherein step (1) comprises the step of operating on an approximate half cycle of the carrier signal with a filter having an approximately rectangular impulse response and integrating the output of the filter.
3. The method according to claim 1 , wherein step (1) comprises the step of controlling a switch to pass an approximate half cycle of the carrier signal through the switch and integrating the output of the switch.
4. The method according to claim 1 , where D 1 is a transform, u(t) is a step function, u(t)−u(t−T A ) is a windowing operator or aperture of duration T A , and A sin (φt+N) is an approximate half cycle of the carrier signal, and wherein step (1) comprises the step of processing the approximate half cycle of the carrier signal in accordance with:
D 1 =∫ 0 T A ( u ( t )− u ( t−T A ))· A sin(ω t +φ) dt.
5. The method according to claim 1 , wherein step (2) comprises the step of transferring a portion of the energy contained in an approximate half cycle of the carrier signal to an energy storage device.
6. The method according to claim 1 , wherein step (2) comprises the step of transferring a portion of the energy contained in an approximate half cycle of the carrier signal to a capacitive storage device.
7. The method according to claim 1 , where E is energy, A is a constant, S i (t) is the carrier signal, A·S i (t) is an aperture impulse response of duration T A , and wherein step (2) comprises the step of accumulating energy from an approximate half cycle of the carrier signal in accordance with:
E
=
(
∫
0
T
A
A
·
S
i
(
t
)
)
2
ⅆ
t
.
8. The method according to claim 1 , further comprising the step of:
(4) passing on the accumulation result of step (2) to a reconstruction filter.
9. The method according to claim 1 , further comprising the step of:
(4) passing on the accumulation result of step (2) to an interpolation fiter.
10. The method according to claim 1 , wherein step (3) comprises the step of repeating steps (1) and (2) at a sub-harmonic rate of the carrier signal.
11. The method according to claim 1 , wherein step (3) comprises the step of repeating steps (1) and (2) at an off-set of a sub-harmonic rate of the carrier signal.
12. The method according to claim 1 , further comprising the step of:
(4) performing steps (1), (2), and (3) for positive approximate half cycles of the carrier signal and for inverted negative approximate half cycles of the carrier signal.
13. A system for down-converting an electromagnetic signal, comprising:
a first finite time integrating module that receives an input signal, wherein said first finite time integrating module down-converts said input signal according to a first control signal and outputs a down-converted in-phase signal portion of said input signal;
a second finite time integrating module that receives said input signal, wherein said second finite time integrating module down-converts said input signal according to a second control signal and outputs a down-converted inverted in-phase signal portion of said input signal, wherein said down-converted inverted in-phase signal portion is substantially equal to an inverted version of said down-converted in-phase signal portion of said input signal; and
a first combiner module that combines said down-converted inverted in-phase signal portion with said down-converted in-phase signal portion and outputs a first channel down-converted signal;
wherein a second control signal pulse of said second control signal occurs 1.5 cycles of a frequency of said input signal after the occurrence of a first control signal pulse of said first control signal.
14. The system of claim 13 , wherein said input signal is a RF carrier signal that is AM, FM, or PM modulated with an information signal.
15. The system of claim 14 , wherein said first channel down-converted signal is a baseband signal.
16. The system of claim 14 , wherein said first channel down-converted signal is an intermediate frequency signal.
17. The system of claim 13 , further comprising:
a third finite time integrating module that receives said input signal, wherein said third finite time integrating module down-converts said input signal according to a third control signal and outputs a down-converted quadrature-phase signal portion of said input signal;
a fourth finite time integrating module that receives said input signal, wherein said fourth finite time integrating module down-converts said input signal according to a fourth control signal and outputs a down-converted inverted quadrature-phase signal portion of said input signal; and
a second combiner module that combines said down-converted inverted quadrature-phase signal portion with said down-converted quadrature-phase signal portion and outputs a second channel down-converted signal.
18. The system of claim 17 , wherein said first combiner module and said second combiner module each comprise a differential amplifier.
19. The system of claim 17 , further comprising:
a first filter that filters said down-converted in-phase signal portion;
a second filter that filters said down-converted inverted in-phase signal portion;
a third filter that filters said down-converted quadrature-phase signal portion; and
a fourth filter that filters said down-converted inverted quadrature-phase signal portion.
20. The system of claim 19 , wherein said first, second, third, and fourth filters each comprise a low-pass filter.
21. The system of claim 20 , wherein each said low-pass filter comprises a resistor and a capacitor.
22. The system of claim 17 , further comprising a low-noise amplifier that amplifies said input signal.
23. The system of claim 17 , wherein said input signal comprises an RF I/Q modulated signal.
24. The system of claim 23 , wherein said first channel down-converted signal comprises an I-phase information signal portion of said RF I/Q modulated signal, and wherein said second channel down-converted signal comprises a Q-phase information signal portion of said RF I/Q modulated signal.
25. The system of claim 24 ,
wherein a fourth control signal pulse of said fourth control signal occurs 1.5 cycles of said frequency of said input signal after the occurrence of a third control signal pulse of said third control signal; and
wherein said third control signal pulse occurs 0.75 cycles of said frequency of said input signal after the occurrence of said first control signal pulse.