Northrop Grumman Systems Corporation

Kent KinMan Tam

Leon Burks, Jr

Mark David Brown

William R Sheppard

A non-destructive, inline, multi-channel fabric conductivity measurement system uses an array of opposing paired transmit/receive microwave horns on opposite sides of a fabric material moving in a production line, each horn pair corresponding to a channel in the system. A processor-based controller can control channel hopping, frequency hopping, and measurement orientation to acquire measurements of material conductivity and anisotropy, which measurements can be analyzed for defects that can be flagged in real time during production. Measurements and/or analyses can be stored to make roll-to-roll, batch-to-batch, day-to-day, or production-phase-to-production-phase comparisons useful in identifying the sources of production problems and/or the causes of corrections.

Inline fabric conductivity measurement

The invention is a process for determining the resistivity of a layered structure including a layer of resistive material hidden under a topcoat and a tile layer, the process comprises the steps of; 1) directing electromagnetic radiation over a selected frequency range to the outer surface of the layered structure; 2) measuring the reflection of the electromagnetic radiation from the layered structure surface; 3) converting the signal into the time domain; 4) analyzing the first echo to obtain the topcoat thickness; 5) obtaining the tile thickness from the time delay between the first and second echoes; 6) compensating the second echo with electromagnetic power loss due to the topcoat and tile; and 7) determining the resistance of the resistive layer from the compensated second echo.

Process for determining the resistivity of a resistive layer

A non-contact probe for determining the conductivity of coating materials is disclosed. The probe includes a free running oscillator operating at a selected frequency, a sensor made up of an LC circuit, a detector for detecting a change in the LC circuit in response to change in the sensor coil induction, and a processor for converting the detected changes in the signal to surface conductivity data. The detector may be a frequency detector that detects changes in the resonant frequency of the LC circuit or the detector may be a magnitude detector that detects changes in the signal magnitude of the LC oscillator. The sensor is the coil inductor of the LC circuit. Inductance of the sensor coil is variable depending on conductivity of the material near the sensor coil.

Non-contact surface conductivity measurement probe

The invention is a device for inspecting an assembly including a surface coating containing magnetic radar-absorbing materials on a conductive surface. In detail, the device includes a first system for transmitting an electromagnetic signal to the assembly, which includes a first waveguide made of a conductive material coupled in series to a second waveguide made of a dielectric material. A second system is provided for receiving the portion of the electromagnetic signal reflected from the assembly, which includes a third waveguide made of a conductive material coupled in series to a fourth waveguide made of a dielectric material. Thus the electromagnetic signal is transmitted from the first waveguide to the second waveguide on to the assembly and the portion of the electromagnetic signal reflected off the assembly is received by the fourth-waveguide and transmitted to the third, waveguide.

Inspection device for radar absorbing materials

A methodology for the measurement of the effectiveness of gap filler materials and treatments in radar cross section reduction uses an untreated calibration gap in a plate mounted at an acute angle so that specular reflection from radar illumination is diverted away from the horn antenna while monostatic reflection is returned to the antenna. A dielectric lens is used to focus the radar illumination in a narrow beam width so that edge effects of the plate are minimized, obviating the need for an anechoic facility. A spectral baseline is first determined using an untreated gap after which a relative quantitative test is performed on a treated gap. The antenna and horn may be mounted for motion along the gap to determine the electrical continuity of the gap treatment.

Measurement of radar cross section reduction

An eddy current probe for detection of cracks in multi-layered structures. The probe includes a body of a material having high permeability and is shaped to include a central core and an additional wall. A central core drive coil is wound around the central core of the body and a plurality of sense coils are located in an array in association with the additional wall. An outer drive coil is wound about the outside of the additional wall. The central core drive coil is excited with a first alternating current high frequency signal producing eddy currents primarily in the top of the layered structure. These eddy currents are sensed with the sense coil array and analyzed for structural defects in the top surface of the layered structure. The central core coil is excited with a second alternating current signal of a lower frequency than the first signal producing eddy currents in deeper layers of the structure. Such eddy currents are sensed by the sense coils and the signals so sensed are stored. The outer drive coil is excited with a low frequency signal and the sense coils operated to detect eddy currents in deeper layers of the structure. The signal from excitation of the outer drive coil is scaled with respect to the signal from the central core drive coil for separating signal indicative of defects from that indicative of differences in the structure of the underlying components of the layered structure. The probe may be circular or linear.

Growing community of inventors

Rowland Heights, CA, United States of America

Kent KinMan Tam