Radiant energy – Radio and microwave absorption wavemeters
Reexamination Certificate
1999-10-07
2001-12-11
Dang, Hung Xuan (Department: 2873)
Radiant energy
Radio and microwave absorption wavemeters
C250S338100, C250S338400, C338S014000, C338S018000
Reexamination Certificate
active
06329649
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to the field of radiation sensors. More particularly, the present invention relates to a monolithic integrated focal plane sensor array having elements sensitive to millimeter-wave radiation and elements sensitive to infrared radiation.
2. Description of the Related Art
Radiation sensors are generally known which convert electromagnetic radiation for radiation sensing equipment that is capable of detecting and monitoring electromagnetic radiation of varied wavelength bands to provide a multi-mode sensing type of device. In the prior art, physically separate, non-integrated millimeter-wave (mm-wave or MMW) and infrared (IR) sensing units have been used to provide separate sensing and detecting capabilities in those two different electromagnetic wavelength bands, which, however, leads to a bulky overall system. Several prior attempts have been made to fabricate a single integrated system incorporating two separate FPAs (focal plane arrays), with one being a mm-wave FPA and the other an IR FPA, as provided on a common support body or substrate. However, millimeter-wave radiation of approximately 94 GHz and IR at 3-5 and 8-12 &mgr;m (where atmospheric transmission of IR is greatest) differ so significantly in frequencies from each other that integrating these different types of electromagnetic radiation sensors into a single device has posed a technical and practical challenge in the field. Sometimes these integrated systems have used a single aperture for receiving incident radiation at the sensor. The systems separate the incoming radiation energy into mm-wave and IR beams by means of a series of beam splitters to direct the appropriate energy to the appropriate FPA. However, such an approach results in increased cost, lower efficiency and increased size of the overall system.
U.S. Pat. Nos. 4,654,622 and 5,450,053 describe incorporating antennas in microbolometer detector architectures used for IR/mm-wave detection to provide a mm-wave energy coupling apparatus. These patents describe, as one embodiment, a linear sensor array on the front surface of a substrate that combines planar dipole or bowtie type antennas to couple the mm-wave radiation microsensors with interdispersed separate microsensors used for IR sensing. The mm-wave sensors sense only one polarization. The configuration of this linear geometry type of focal plane sensor array in these patents can not be extended to a two-dimensional (2-D) array. Also, the focal plane sensor array can not sense the other dimensional (2-D) array. Also, the focal plane sensor array can not sense the other polarization without losing ≈10× of IR resolution. In another described embodiment in these patents, fabrication of a two-dimensional array is proposed where “bow-tie” microantenna designs are formed on the backside of a silicon substrate while IR sensitive microdetector arrays are formed on the opposite frontside of the substrate, such that incident radiation is collected by the antennas after passing through the substrate. Again, the single “bowtie” microantennas sense only one polarization. This two-dimensional sensor array approach of the above-identified patents is considered problematic because, among other things, incident mm-wave radiation would be reflected by the intervening XY matrix read-out wiring associated with the IR sensor array before it reaches the antennas located on the backside of the substrate.
Consequently, there remains a need for improved monolithic sensors that integrate an IR sensor array with mm-wave sensors on a common support in way that can be conveniently fabricated while resulting in a high performance radiation sensing device.
SUMMARY OF THE INVENTION
The above and other needs in the art are addressed by the monolithic integrated radiation sensor of the present invention. In one embodiment of this invention, there is an integrated infrared and millimeter-wave monolithic focal plane sensor array comprising a substrate having first and second opposing generally flat surfaces in which an array of infrared sensors and at least one millimeter-wave sensor are provided at a first level on the first surface, and further including a planar antenna for receiving incident millimeter-wave the substrate, for coupling the millimeter-wave radiation field to the millimeter-wave sensor.
In one preferred implementation, this invention combines linear or two-dimensional (2-D) arrays of IR sensors and mm-wave sensors on the front surface of a silicon read-out IC (ROIC) substrate. Advantageously, the inventive focal plane sensor array incorporates an antenna onto the same side of the substrate as the mm-wave and IR microsensors having a unique and improved antenna shape for coupling a radiation field to the mm-wave sensor element. Namely, the improved antenna shape of the antenna is defined by two constituent microantennas which are orthogonally-oriented to one another in a manner, such as a “crossed-bowtie” configuration, enabling absorption of electromagnetic radiation of both polarities.
Among other advantages provided by the invention, the monolithically integrated mm-wave/IR focal plane sensor array is a bona fide integrated structure as both types of sensors are fabricated upon the same side of the substrate without the mm-wave sensor system interfering with the operation of the IR sensor system, and vice versa. Successfully combining these two types of sensors on one focal plane results in much smaller and lower cost system. It automatically provides the same, naturally aligned Field of View (FOV) for both imaging domains. This simplifies significantly the sensor fusion algorithms, which results in reduced needs for high speed, high power computing. Also, the inventive integrated sensor offers manufacturing ease as it only requires adding simple processing to provide the additional metallization layer for the antenna. Additionally, to make room for the mm-wave sensor on the same plane or level of the sensor device as the IR sensors, relatively little real estate is needed, e.g., only one out of about 100 IR bolometers must be sacrificed to make room for the mm-wave sensor. The performance of each respective mm-wave and/or IR sensor array can be maximized in an independent manner. The invention also is directed to a method of fabricating such a focal plane sensor array. also is directed to a method of fabricating such a focal plane sensor array.
REFERENCES:
patent: 4654622 (1987-03-01), Foss et al.
Balcerak Ray
Dolezal Franklin A.
Grinberg Jan
Jack Michael D.
Dang Hung Xuan
Lenzen, Jr. Glenn H.
Raytheon Company
Schubert William C.
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