DIGITAL SIGNAL CONDITIONING

• US 20110206163A1
• Filed: 08/30/2010
• Published: 08/25/2011
• Est. Priority Date: 08/31/2009
• Status: Active Grant

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems National Security Solutions Incorporated (BAE Systems Plc)
• Inventors: Lowdermilk, Robert W., Tammen, Michael, Vuletic, Dragan, Harris, Fredric J.
• Granted Patent: US 8,744,025 B2
• Time in Patent Office: Days
• US Class Current: 375/316
• CPC Class Codes: G01R 23/16 Spectrum analysis; Fourier analysis

Abstract

Methods, systems and other embodiments associated with pre-processing a signal for spectral analysis are presented. A system for pre-processing a digital input signal includes a digital down converter (DDC), an interpolator, and a series of down samplers. The DDC modulates the digital input signal to create a down converted signal. The interpolator re-samples the down converted signal to produce a re-sampled signal. The series of down samplers produces down sampled signals. The multiplexer selects one of the digital input signal, the down converted signal, and the down sampled signals and routes the selected signal to an output line.

Claims

1. A system for pre-processing a digital input signal comprising:

a digital down converter (DDC) to modulate the digital input signal to create a down converted signal;

an interpolator to re-sample the down converted signal to produce a re-sampled signal;

two or more down samplers to produce two or more down sampled signals associated with the down samplers; and

a multiplexer to multiplex one of the digital input signal, the down converted signals, and one of the two or more down sampled signal to an output line.

2. The system of claim 1 wherein the DDC is a 4-to-1 digital down converter.

3. The system of claim 1 wherein the two or more down samplers are 2-to-1 down samplers.

4. The system of claim 1 wherein the interpolator is an M-path polyphase filter bank.

5. The system of claim 4 wherein the M-Path polyphase filter bank performs interpolation based, at least in part, on a Taylor series correction of the down converted signal.

6. The system of claim 1 wherein the digital input signal is a real input signal and not a quadrature based signal.

7. The system of claim 1 wherein the digital input signal is received from an analog-to-digital converter (ADC).

8. The system of claim 1 wherein the digital input signal is an intermediate frequency (IF) signal.

9. The system of claim 1 wherein the output line is configured to be connected to a spectrum analyzer input buffer.

10. The system of claim 1 wherein the interpolator further comprises:

one or more finite impulse response (FIR) filters;

one or more accumulators; and

wherein the interpolator is configured to operate on the down converted signal with the one or more FIR filters to produce filter values, wherein the filter values are accumulated in the one or more accumulators to produce accumulated values, and wherein the re-sampled signal is based, at least in part, on the filter values and accumulator values.

11. The system of claim 1 wherein the interpolator is configured to produce the re-sampled signal based, at least in part, on a modulo (MOD) 32 function.

12. The system of claim 1 wherein the interpolator is configured to produce derivative weights of the down converted signal and configured to produce interpolator weights of the down converted signal, and wherein the re-sampled signal is based, at least in part, on the derivative weights and the interpolator weights.

13. A method of digital signal conditioning comprising:

down converting an input signal to produce a down converted signal;

interpolating the down converted signal to produce an interpolated signal;

passing the interpolated signal through a series of two or more down samplers to produce down sampled singles; and

multiplexing one of the input signal, the converted signal, the interpolated signal and the down sampled signals to an output port as an output signal.

14. The method of claim 13 wherein the interpolating further comprises:

filtering the down converted signal with an M-path polyphase filter bank;

generating the interpolated signal based, at least in part, on a result of the filtering.

15. The method of claim 13 wherein the interpolating further comprises:

passing the down converted signal through a finite impulse response (FIR) filter; and

generating the interpolated signal based, at least in part, on an output of the FIR filter.

16. The method of claim 13 further comprising:

receiving the input signal form an analog-to-digital (ADC).

17. The method of claim 13 wherein the receiving further comprises:

receiving an input signal that is an intermediate frequency (IF) signal.

18. The method of claim 13 further comprising:

transferring the output signal to an input buffer of a spectrum analyzer.

19. The method of claim 13 wherein the down converting further comprises:

passing the input signal through a 4-to-1 digital down converter.

20. The method of claim 13 wherein the passing further comprises:

passing the interpolated signal through one or more 2-to-1 down samplers.