Method for implementing continuous radio frequency (RF) alignment in advanced electronic warfare (EW) signal stimulation systems

• US 20090237295A1
• Filed: 12/18/2006
• Published: 09/24/2009
• Est. Priority Date: 12/18/2006
• Status: Active Grant

• Current Assignee: AAI Corporation (Textron Inc)
• Original Assignee: AAI Corporation (Textron Inc)
• Inventors: Jaklitsch, James J., Markey, Jay, McGrath, Thomas P.
• Granted Patent: US 7,801,502 B2
• Time in Patent Office: Days
• US Class Current: 342/169
• CPC Class Codes: G01R 31/2841 Signal generators
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

A method of providing an integrated approach to automated system alignment is set forth, which may include in an exemplary embodiment: providing amplifier compression alignment, (which may include characterizing and/or compensating for a parasitic effect); providing continuous internal alignment of phase and amplitude of a synthetic stimulus instrument (SSI) output signal; providing external measurement port alignment; and providing transfer alignment of internal measurement paths. According to another exemplary embodiment, a receiver apparatus may include: a dual-channel coherent measurement receiver which may include at least one internal channel operative to measure time-division-multiplexed (TDM) feedback signals from each signal source of a synthetic stimulus instrument (SSI); and at least one external channel operative to make direct measurement at an external alignment port output.

Claims

1. A method of providing an integrated approach to automated system alignment, comprising:

providing amplifier compression alignment;

providing continuous internal alignment of phase and amplitude of a synthetic stimulus instrument (SSI) output signal;

providing external measurement port alignment; and

providing transfer alignment of internal measurement paths.

2. The method of claim 1, further comprising:

providing power leveling to improve accuracy.

3. The method of claim 1, further comprising:

providing time angle of arrival alignment.

4. The method of claim 1, further comprising:

providing pulse width alignment.

5. The method of claim 1, wherein said providing continuous internal alignment, comprises:

a foreground process, wherein said foreground process comprises

characterizing one or more parameters that are most sensitive to fluctuation with at least one of time and/or temperature, and

updating said parameters for all frequency at a high refresh rate; and

a background process, wherein said background process comprises

characterizing one or more parameters that are less sensitive to fluctuation with at least one of time and/or temperature, and

updating said parameters for all frequency at a lower refresh rate.

6. The method of claim 5, wherein said parameters comprise at least one of base state phase and/or amplitude.

7. The method of claim 5, further comprising:

a parametrically extendible measurement cycle comprising

matched-filter coherent measurement processing comprising

making back-to-back elementary measurements, wherein each of said measurements are phase offset by 180 degrees, to cancel a VSWR error of a VSWR cancellation technique.

8. The method of claim 1, wherein said providing amplifier compression alignment comprises:

characterizing the effect of amplifier compression on phase and amplitude comprising;

driving an attenuation control as required to achieve actual attenuation states in octave increments of dB, for each applicable range of step attenuation; and

measuring a super-attenuation and a saturation induced phase contribution (SIPC) at each of said attenuation states, in each of said ranges of step attenuation.

9. The method of claim 8, wherein said driving said attenuation control as required to achieve actual attenuation states in said octave increments comprises:

driving said attenuation control as required to achieve actual attenuation states in said octave increments of dB comprising at least one of 0, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0, and/or 16.0.

10. A method for characterizing the effect of each step attenuator state, on phase and amplitude, comprising

activating each step attenuator state as the sole contributor to attenuation, and

measuring at least one of a step attenuator amplitude contribution (SAAC) and/or a step attenuator phase contribution (SAPC).

11. A method for mapping an arbitrary RF Power command into hardware control signals used to produce a commanded RF Power at a Port output for each frequency, the method comprising:

a. providing a level shift that maps an absolute Power Command, in units of dBm, to a relative power command, in units of dBfs;

b. providing a step attenuation state parser that computes the appropriate state for the step attenuator, and subtracts a step attenuator amplitude contribution from said relative power command, to compute an AM DAC attenuation;

c. providing a super-attenuation function that adjusts said AM DAC attenuation command to produce desired attenuation, adding any additional attenuation as required to compensate for non-linear effects of compression, wherein said super-attenuation function is implemented as a stored data table, in octave increments of dB, for each applicable range of step attenuation, with an exact value determined by means of quadratic interpolation at run time;

d. providing a theoretical conversion of said AM DAC attenuation command to hardware bits; and

e. providing a frequency-dependent offset for power leveling.

12. The method of claim 11, wherein said providing said super-attenuation function in said octave increments of dB comprises:

providing said super-attenuation function in said octave increments of dB comprising at least one of 0, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0, and/or 16.0.

13. A method for mapping an arbitrary RF Phase Command into hardware phase-shift control signals, as required to produce a commanded RF Phase at the Port output for each frequency, the method comprising:

a. computing an aggregate Phase Compensation value from at least one of;

i. a base-state phase error, measured at each sub-band of a synthetic stimulus instrument (SSI),

ii. a filter induced phase contribution (FIPC) measured at closely spaced frequency increments across each sub-band, stored in data tables, and interpolated at run-time using quadratic interpolation,

iii. a step attenuator phase contribution (SAPC), measured at each sub-band of the SSI, and/or

iv. a saturation-induced phase contribution (SIPC), characterizing a non-linear phase shift associated with amplifier compression, wherein SIPC compensation is implemented as a stored data table, in octave increments of dB, for each applicable range of step attenuation, with the exact value determined by means of quadratic interpolation at run time; and

b. subtracting said Phase Compensation value from the RF Phase Command.

14. The method of claim 13, wherein said (a) (ii) comprises closely spaced frequency increments comprising about 200 KHz.

15. The method of claim 13, wherein said (a) (iv) comprises octave increments of dB comprising at least one of 0, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0, and/or 16.0.

16. A method of using a state-estimation filter comprising:

using a state-estimation filter for computing true values for a step attenuator amplitude contribution (SAAC) and a step attenuator phase contribution (SAPC), in presence of measurement noise.

17. The method of claim 16, wherein said step attenuator amplitude contribution (SAAC) and said step attenuator phase contribution (SAPC) are computed as differentials from a full-power reference measurement comprising amplitude and phase.

18. A method for using a “

B”

channel of a dual channel measurement receiver as a transfer standard for power measurement comprising;

correlating measurements made with an “

A”

channel to measurements made with an RF Power Meter on one RF signal source, so that readings from the “

A”

channel are aligned to the RF Power Meter;

aligning the “

B”

Channel to the “

A”

Channel (Transfer alignment of Channel B to the RF Power Meter), once the “

A”

channel has been aligned to read the same as the RF Power Meter; and

using the “

B”

Channel as a transfer standard to measure all remaining RF signal sources in the system, on a time-line much faster than may be accomplished using a power meter.

19. A receiver apparatus comprising:

a dual-channel coherent measurement receiver comprising

at least one internal channel operative to measure time-division-multiplexed (TDM) feedback signals from each signal source of a synthetic stimulus instrument (SSI); and

at least one external channel operative to make direct measurement at an external alignment port output.