Low cost millimeter wave imager

• US 7,583,074 B1
• Filed: 12/16/2005
• Issued: 09/01/2009
• Est. Priority Date: 12/16/2005
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Colburn, Joseph, Schaffner, James H., Choudhury, Debabani, Lynch, Jonathan James, Hunter, Andrew T., Schulman, Joel N., Sievenpiper, Daniel Frederic, Moyer, Harris P.
• Primary Examiner(s): Dole; Timothy J.
• Assistant Examiner(s): Valone; Thomas F.
• Application Number:
  US11/303,642
• Time in Patent Office: 1,355 Days
• Field of Search: 324/120, 324/119, 324/96, 250/208.1, 250/334, 342/179
• US Class Current: 324/120
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: H01Q 19/062 for focusing
• CPC Class Codes: H01Q 21/064 using horn or slot aerials slotted waveguides arrays H01Q21/005
• CPC Class Codes: H01Q 3/2658 Phased-array fed focussing structure
• CPC Class Codes: H05K 1/0243 Printed circuits associated with mounted high frequency components
• CPC Class Codes: H05K 1/0306 Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 1/112 directly combined with via connections

Abstract

Low cost millimeter wave imagers using two-dimensional focal plane arrays based on backward tunneling diode (BTD) detectors. Two-dimensional focal arrays of BTD detectors are used as focal plane arrays in imagers. High responsivity of BTD detectors near zero bias results in low noise detectors that alleviate the need for expensive and heat generating low noise amplifiers or Dicke switches in the imager. BTD detectors are installed on a printed circuit board using flip chip packaging technology and horn antennas direct the waves toward the flip chip including the BTD detectors. The assembly of the horn antennas, flip chips, printed circuit board substrate, and interconnects together work as an imaging sensor. Corrugated surfaces of the components prevent re-radiation of the incident waves.

Claims

1. A focal plane array detector comprising:

a printed circuit board having an input side and an output side;

an array of backward tunneling diodes located on monolithic microwave integrated circuits at a focal plane, the monolithic microwave integrated circuits being assembled onto the input side;

electrical connections for readout circuitry located on the output side; and

a plurality of horn antennas coupled to the input side, each of the horn antennas being associated with a corresponding one of the backward tunneling diodes, and coupling incident waves directly to the corresponding one of the backward tunneling diodes without an intervening active component,

wherein the printed circuit board comprises;

a quartz substrate having a thickness of one quarter wavelength of a millimeter wave;

a metal pattern on a side of the quartz substrate corresponding to the input side, the metal pattern comprising bonding pads for coupling the monolithic microwave integrated circuits to the printed circuit board; and

a plurality of vias through the quartz substrate for routing a signal from the input side to the electrical connections located on the output side,

wherein the output side is opposite to the input side.

2. The focal plane array detector of claim 1,

wherein a waveguide portion is coupled between each of the horn antennas and a corresponding one of the monolithic microwave integrated circuits.

3. The focal plane array detector of claim 1, wherein the printed circuit board contains circuitry for transferring incident waves collected by the plurality of horn antennas to the backward tunneling diodes.

4. The focal plane array detector of claim 1, wherein the horn antennas are radiatively coupled to the monolithic microwave integrated circuits.

5. The focal plane array detector of claim 1, wherein the monolithic microwave integrated circuits are flip chips.

6. A millimeter-wave imaging sensor comprising:

a focal plane array detector at a focus of an objective lens and on a printed circuit board,

wherein the focal plane array detector comprises horn antennas for focusing incident waves onto backward tunneling diodes without an intervening active component between each horn antenna and a corresponding one of the backward tunneling diodes, each of the backward tunneling diodes corresponding to one of the horn antennas, and

wherein the printed circuit board comprises;

a quartz substrate having a thickness of one quarter wavelength of a millimeter wave;

a metal pattern on a side of the quartz substrate corresponding to an input side of the printed circuit board, the metal pattern comprising bonding pads for coupling the focal plane array detector to the printed circuit board; and

a plurality of vias through the quartz substrate for routing a signal from the input side to electrical connections for readout circuitry located on an output side of the printed circuit board,

wherein the output side is opposite to the input side.

7. A wave detector module comprising:

a flip chip;

a backward tunneling diode wave detector on the flip chip, the flip chip being on a surface of a printed circuit board;

electrical connections for readout electronics coupled to the flip chip; and

a horn antenna coupled to the flip chip, the horn antenna having an inlet rectangular cross-section substantially parallel with said surface of the printed circuit board,

wherein the flip chip, the electrical connections, and the backward tunneling diode are configured to function together as an imaging sensor,

wherein the flip chip is at a focal plane of a focusing lens, and

wherein the printed circuit board comprises;

a quartz substrate having a thickness of one quarter wavelength of a millimeter wave;

a metal pattern on a side of the quartz substrate corresponding to said surface of the printed circuit board, the metal pattern comprising bonding pads for coupling the flip chip to the printed circuit board; and

a plurality of vias formed through the quartz substrate for routing a signal from said surface to the electrical connections located on an output side of the printed circuit board,

wherein the output side is opposite to said surface.

8. The wave detector module of claim 7, further comprising:

readout electronics coupled to the electrical connections.

9. A method of detecting low power waves for use by readout circuitry, the method comprising:

receiving wave energy by a horn antenna, the horn antenna having an inlet and a throat, the inlet having a rectangular cross-section;

directing the wave energy toward a backward tunneling diode detector on a printed circuit board within the throat without an intervening active component between the horn antenna and the backward tunneling diode detector, the printed circuit board being substantially parallel with the inlet rectangular cross-section;

detecting the wave energy by the backward tunneling diode detector, the backward tunneling diode detector operating near zero bias voltage; and

providing detected wave energy signals to the readout circuitry,

wherein the printed circuit board comprises;

a quartz substrate having a thickness of one quarter wavelength of a millimeter wave;

a metal pattern on a side of the quartz substrate corresponding to an input side of the printed circuit board, the metal pattern comprising bonding pads for coupling the backward tunneling diode detector to the printed circuit board; and

a plurality of vias through the quartz substrate for routing a signal from the input side to electrical connections located on an output side of the printed circuit board,

wherein the output side is opposite to the input side.

10. The method of claim 9,

wherein the throat comprises a waveguide portion between the inlet and the printed circuit board.