MILLIMETER AND SUB-MILLIMETER WAVE PORTAL

• US 20080111735A1
• Filed: 02/12/2007
• Published: 05/15/2008
• Est. Priority Date: 11/13/2006
• Status: Active Grant

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Optimer Photonics, Inc (Battelle Memorial Institute)
• Inventors: Schofield, Philip, Risser, Steven, Ridgway, Richard
• Granted Patent: US 8,098,185 B2
• Time in Patent Office: Days
• US Class Current: 342/200
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 7/03 Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
• CPC Class Codes: H04B 2210/006 Devices for generating or processing an RF signal by optical means

Abstract

In accordance with one embodiment of the present invention, a millimeter or sub-millimeter wave portal system is provided. Generally, the portal system comprises an electrooptic source and one or more millimeter or sub-millimeter wave detectors. The electrooptic source comprises an optical signal generator, optical switching and encoding circuitry, and one or more optical/electrical converters. Additional embodiments are disclosed and claimed.

Claims

1. A millimeter or sub-millimeter wave portal system comprising an electrooptic source and a millimeter or sub-millimeter wave detector, wherein the structure of the portal is such that at least the following conditions apply:

the electrooptic source comprises an optical signal generator, optical circuitry, and an optical/electrical converter;

the optical signal generator is configured to generate a modulated optical signal characterized by a modulation frequency of at least about 30 GHz;

the optical circuitry is configured to direct the modulated optical signal to the optical/electrical converter;

the optical/electrical converter is configured to convert the modulated optical signal to a millimeter or sub-millimeter wave and direct the millimeter or sub-millimeter wave in the direction of an object positioned within a field-of-view defined by the millimeter or sub-millimeter wave detector; and

the millimeter or sub-millimeter wave detector is configured to convert reflections of the millimeter or sub-millimeter wave from the object to signals representing attenuation of the millimeter or sub-millimeter wave upon reflection from the object.

2. A system as claimed in claim 1 wherein the optical signal generator comprises an electrooptic sideband generator and an optical filter.

3. A system as claimed in claim 2 wherein:

the electrooptic sideband generator is configured to generate frequency sidebands about a carrier frequency of an input optical signal; and

the optical filter is configured to discriminate between the frequency sidebands and the carrier frequency.

4. A system as claimed in claim 3 wherein the optical signal generator further comprises optical circuitry configured to direct particular sidebands of interest to an optical output in the form of a millimeter wave optical signal.

5. A system as claimed in claim 2 wherein:

the sideband generator comprises a phase modulator comprising an optical waveguide and a modulation controller configured to drive the sideband generator at a control voltage substantially larger than V_π

to generate frequency sidebands about a carrier frequency of the optical signal, where V_π

represents the voltage at which a π

phase shift is induced in the optical waveguide; and

the optical filter is configured to discriminate between the frequency sidebands and the carrier frequency such that sidebands of interest can be directed to the optical output of the optical signal generator.

6. A system as claimed in claim 2 wherein:

the sideband generator is formed over a device substrate and is configured to generate frequency sidebands about a carrier frequency of the optical signal; and

the optical filter is formed over the device substrate and is configured to discriminate between the frequency sidebands and the carrier frequency such that sidebands of interest can be directed to the optical output.

7. A system as claimed in claim 2 wherein the electrooptic sideband generator comprises an electrooptic interferometer and the optical filter comprises an arrayed waveguide grating.

8. A system as claimed in claim 7 wherein the optical circuitry is configured to combine selected optical outputs of the arrayed waveguide grating to create the modulated optical signal.

9. A system as claimed in claim 1 wherein the optical circuitry is configured to direct the modulated optical signal to a plurality of optical/electrical converters.

10. A system as claimed in claim 9 wherein the optical circuitry directs the modulated optical signal to a plurality of optical/electrical converters by splitting the modulated optical signal into a plurality of modulated outputs.

11. A system as claimed in claim 9 wherein the optical circuitry directs the modulated optical signal to a plurality of optical/electrical converters by redirecting the modulated optical signal sequentially from one optical/electrical converter to the next.

12. A system as claimed in claim 1 wherein:

the optical signal generator comprises a plurality of optical outputs characterized by distinct frequencies; and

the optical circuitry is configured to permit the selection and combination of different ones of the distinct-frequency optical outputs of the optical signal generator.

13. A system as claimed in claim 12 wherein the optical circuitry is configured to direct different combinations of the distinct-frequency optical outputs to a common optical/electrical converter.

14. A system as claimed in claim 12 wherein the optical circuitry is configured to direct different combinations of the distinct-frequency optical outputs to plurality of different optical/electrical converters.

15. A system as claimed in claim 1 wherein the optical circuitry is configured to encode the modulated optical signal prior to direction to the optical/electrical converter.

16. A system as claimed in claim 1 wherein the detector comprises an antenna assembly comprising an antenna portion and an electrooptic waveguide portion.

17. A system as claimed in claim 16 wherein:

the antenna portion comprises at least one tapered slot antenna; and

the electrooptic waveguide portion comprises a waveguide core extending substantially parallel to a slotline of the tapered slot antenna in an active region of the antenna assembly.

18. A system as claimed in claim 17 wherein:

the electrooptic waveguide at least partially comprises a velocity matching electrooptic polymer in the active region of the antenna assembly;

a velocity v_e of a millimeter or sub-millimeter wave signal traveling along the tapered slot antenna in the active region is at least partially a function of the dielectric constant of the velocity matching electrooptic polymer;

a velocity v_O of an optical signal propagating along the waveguide in the active region is at least partially a function of the index of refraction of the velocity matching electrooptic polymer; and

the active region and the velocity matching electrooptic polymer are configured such that v_e and v_O satisfy the following relation;

$\frac{<br><br>v_e-v_O<br><br>}{v_O}\le <br><br>20<br><br>\%.$

19. A system as claimed in claim 16 wherein:

the antenna portion comprises at least one tapered slot antenna;

the waveguide portion comprises at least one electrooptic waveguide comprising a waveguide core in an active region of the antenna assembly; and

the electrooptic waveguide at least partially comprises a velocity matching electrooptic polymer in the active region of the antenna assembly.

20. A system as claimed in claim 19 wherein:

a velocity v_e of a millimeter or sub-millimeter wave signal traveling along the tapered slot antenna in the active region is at least partially a function of the dielectric constant of the electrooptic polymer;

a velocity v_O of an optical signal propagating along the waveguide in the active region is at least partially a function of the index of refraction of the electrooptic polymer;

the tapered slot antenna comprises first and second electrically conductive elements arranged to define a radiating slot of the antenna;

the first electrically conductive element is arranged in a plane above the electrooptic waveguide; and

the second electrically conductive element is arranged in a plane below the electrooptic waveguide.

21. A system as claimed in claim 1 wherein:

the detector comprises an antenna assembly comprising an antenna portion, a waveguide portion, and a frequency dependent filter;

the antenna portion comprises at least one tapered slot antenna;

the waveguide portion extends along at least a portion of an optical path between an optical input and an optical output of the antenna assembly;

the waveguide portion comprises a waveguide core in an active region of the antenna assembly;

the tapered slot antenna and the electrooptic waveguide are configured such that the millimeter or sub-millimeter wave signal traveling along the tapered slot antenna is imparted on the optical signal as frequency sidebands of an optical carrier frequency; and

the frequency-dependent filter comprises a plurality of filter output ports and is configured to discriminate the frequency sidebands from the carrier frequency band in an optical signal propagating along the waveguide portion, downstream of the active region such that frequency sidebands having wavelengths that are shorter and longer than a wavelength of the carrier band can be recombined at the optical output of the antenna assembly.

22. A system as claimed in claim 1 wherein:

the millimeter or sub-millimeter wave portal system comprises a plurality of parallel portals; and

each of the parallel portals comprises at least one dedicated optical/electrical converter fed by the optical signal generator.

23. A system as claimed in claim 1 wherein the millimeter or sub-millimeter wave portal system comprises at least one portal configured as a walk-through portal including at least one millimeter or sub-millimeter wave component and a supplemental detection component.

24. A millimeter or sub-millimeter wave portal system comprising an electrooptic source and a millimeter or sub-millimeter wave detector, wherein the structure of the portal is such that at least the following conditions apply:

the electrooptic source comprises an optical signal generator, optical circuitry, and an optical/electrical converter;

the optical signal generator is configured to generate a modulated optical signal characterized by a modulation frequency of at least about 30 GHz;

the optical signal generator comprises an electrooptic sideband generator configured as an electrooptic interferometer to generate frequency sidebands about a carrier frequency of an input optical signal and an optical filter configured as an arrayed waveguide grating to discriminate between the frequency sidebands and the carrier frequency at a plurality of optical outputs characterized by distinct frequencies;

the optical signal generator further comprises optical circuitry configured to combine selected optical outputs of the arrayed waveguide grating to create the modulated optical signal and direct particular sidebands of interest to a common optical/electrical converter or a plurality of different optical/electrical converters in the form of a modulated millimeter wave optical signal;

the optical circuitry is configured to direct the modulated optical signal to the optical/electrical converters by splitting the modulated optical signal into a plurality of modulated outputs or redirecting the modulated optical signal sequentially from one optical/electrical converter to the next;

the optical/electrical converter is configured to convert the modulated optical signal to a millimeter or sub-millimeter wave and direct the millimeter or sub-millimeter wave in the direction of an object positioned within a field-of-view defined by the millimeter or sub-millimeter wave detector;

the millimeter or sub-millimeter wave detector comprises an antenna assembly comprising an antenna portion and an electrooptic waveguide portion and is configured to convert reflections of the millimeter or sub-millimeter wave from the object to signals representing attenuation of the millimeter or sub-millimeter wave upon reflection from the object;

the antenna portion of the antenna assembly comprises at least one tapered slot antenna and the waveguide portion of the antenna assembly comprises at least one electrooptic waveguide comprising a waveguide core in an active region of the antenna assembly; and

the electrooptic waveguide at least partially comprises a velocity matching electrooptic polymer in the active region of the antenna assembly.