Communications: directive radio wave systems and devices (e.g. – With particular circuit
Reexamination Certificate
1999-11-29
2001-08-21
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
With particular circuit
C342S371000, C342S372000
Reexamination Certificate
active
06278400
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to transmit/receive (T/R) circuit modules utilized, for example, in phased array radar systems and, more particularly, to a dual channel T/R module where two discrete T/R RF signal channels are implemented side-by-side in a common package.
2. Description of Related Art
Phased array radars utilizing electronically scanned antenna arrays, also referred to as active apertures, require many individually controllable T/R modules which are arranged in an array. The T/R modules are connected to frontally located radiator elements which collectively generate a transmitted radar beam. The beam is normally energized, shaped and directed in azimuth and elevation under electronic control of the signals applied to the individual radiators.
A phased array radar system generates successive transmit pulses which are distributed through a transmit manifold and microwave circuitry to the various antenna radiators. Between transmit pulses, the radar system receives and processes successive return signals from the antenna radiators. The return signals are processed through microwave circuitry in the T/R module, collected through a receive manifold, and then processed in the system for target identification.
Such a radar system also employs a programmed digital processor to control amplification, attenuation, and phase shifting of transmit and receive signals, thereby determining the amplitude, direction, and shape of the aggregate RF energy beam transmitted by or received by the aperture. Different phase shifts cause different transmit or receive circuit delays in delivery of individual RF radiator signals to control the pattern of RF energy wavefronts associated with the different radiators and which are combined to define the direction and shape of a transmitted or received antenna beam.
Each T/R module according to the known prior art typically includes a housing structure or package including microwave signal processing means for processing transmitted and received radar signals, control signal processing means interconnected with microwave signal processing components for coupling control signals thereto; and power conditioning means comprising a number of power conditioning components selectively interconnected with the microwave signal processing components and the control signal processing components for providing electrical power thereto. Because such apparatus operates at relatively high power levels, there is also normally provided means for dissipating the heat generated by the various components, particularly the microwave power amplifiers and the power conditioning components associated therewith.
One known T/R module developed by the assignee of this invention is shown and described in U.S. Pat. No. 4,967,201, entitled, “Multi-Layer Single Substrate Microwave Transmit/Receive Module”, granted to Edward L. Rich, III, on Oct. 30, 1990, one of the inventors named in this application. The module disclosed therein is referred to as a “sugar cube” T/R module and includes a single multi-layer substrate having at least two opposed mounting surfaces. The substrate includes a plurality of integrated dielectric layers, electrical conductors and thermal conductors selectively interconnected between the layers of the substrate. Microwave signal processing means is mounted on at least one of the mounting surfaces of the substrate for processing microwave radar signals. Control signal processing means is also mounted on at least one of the mounting surfaces of the substrate for providing control signals for the microwave signal processing means. Power conditioning means is additionally mounted on at least one of the mounting surfaces of the substrate for providing power to power the microwave signal processing means and control signal processing means. A heat sink interface is coupled to a set of thermal conductors or vias passing vertically through the substrate layers and which are positioned in thermal proximity to selected portions of the microwave signal processing means, the power conditioning means, and the control signal processing means for conducting thermal energy away from the heat generating elements mounted on the substrate to a heat sink.
The “sugar cube” module comprises a relatively early T/R module design in which basic transmit and receive functions, as then conceived, are embodied in a single modular T/R unit with the operating structure supporting such functions integrated together on a main substrate. While presumably operating as intended, certain inherent deficiencies have been found to exist. For example, while the “sugar cube” module exhibits a compact appearance, it embodies only a single T/R channel and is limited by its design to relatively low RF power output operation and is structurally limited to a single RF connection to an RF manifold. Also, while this type of module has a back-end plug-in capability for certain electrical connections, it has no easy plug-in capability for antenna connections. Instead, each module has an antenna radiator built into its front end, thereby creating installation problems in aligning misaligned radiators among installed T/R modules. This is due to the fact that transmitted and received beams require aligned antenna radiators to enable beam control in accordance with system commands.
Moreover, the module-integrated radiator of the “sugar cube” module limits bandwidth during transmission and reception and, because of its simple unpolarized patch structure, restricts radiator operation to a fixed polarization. The “sugar cube” T/R module is thus characterized with polarization inflexibility, whereas good system design requires polarization flexibility to permit variable settings of radiation properties including bandwidth and polarization. For example, if a received signal carries a high noise level in a particular polarization, it is desirable to have the flexibility to control the polarization to an angle where the noise is reduced. In this manner, the signal-to-noise ratio is enhanced and weaker signals can be detected with substantially reduced noise interference.
Further, in an antenna assembly employing “sugar cube” T/R modules, the pin within the single coaxial RF connector between each sugar cube module and the system manifold is susceptible to excessive axial movement in response to antenna mechanical vibrations. Such pin movements can change RF path lengths thereby causing increased noise level and erroneous phase changes which produce beam dispersion and thereby affect intended beam control.
Among other problems encountered with the “sugar cube” T/R module is the removal of heat generated by the active components therein. Thermal conductors, coursing vertically through the layered structure of the module to a heat transfer interface provides only limited heat transfer for removal of heat from the active circuit components. As a result, poor thermal performance contributes to a relatively low RF-power-output capability.
Following the “sugar cube” T/R module the assignee of this invention developed a T/R module which is disclosed in U.S. Pat. No. 5,745,076, entitled “Transmit/Receive Module For Planar Active Apertures”, issued to Thomas R. Turlington et al on Apr. 28, 1998. The T/R module disclosed therein and referred to by the assignee as a “StackPak” (a registered trademark of the Northrop Grumman Corporation) comprises a module configuration which plugs into the backside of an active aperture and includes discrete RF, DC power and data distribution manifolds which are planar in configuration and are stacked together one on top of the other between a cold plate and an antenna assembly, with the antenna elements and circulators being assembled in a single physical unit which forms the front layer of the aperture.
The T/R module itself comprises a multi-chip microwave package comprised of multiple layers of high temperature cofired ceramic (HTCC) including ground planes, stripline, data and DC interconnects, thermal vias and RF inputs/outp
Bonadies Gary N.
Cassen John W.
Eder Timothy L.
Ferrell Gary L.
Fisher John S.
Northrop Grumman Corporation
Sotomayor John B.
LandOfFree
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