Abstract: A multifrequency antenna for a missile is realized by an arrangement in which four microwave antennas are located under a narrow circumferential slot in the skin of the missile forming four separate antennas each with its own input connector. Each antenna consists of a probe fed annular quarter wavelength microwave cavity which radiate out of a top wall end slot. The cavity antennas are fed by a stripline distribution network directly under the antennas. Two L band antennas are positioned directly adjacent the inner surface of the missile skin and an S band antenna and a C band antenna are positioned beneath the L band antennas. A radome covers the circumferential slot.

Abstract: Uniform background charge subtraction in a radiation sensing array is realized by removing the background charge from the array detectors several times during each array integration time. Radiation sensing arrays of the type to which the method of the invention can be applied include a radiation sensor with a charge storage reservoir to which there is coupled a CCD output register having a channel with multiple charge storage sites. Signal background and bias charge is accumulated in the charge storage reservoir and transferred to a CCD storage site by a transfer gate. Charge in the CCD storage site can be shifted to another storage site in the CCD channel or it can be dispersed to drain by means of a drain barrier gate. According to the method of the invention a number of times during each array integration period the charge accumulated in the charge storage reservoir is transferred to a CCD charge storage site and then returned in part to the reservoir leaving a metered amount in the charge storage site.

Abstract: Graphic data entry in an interactive graphic display system is achieved by means of an apparatus that provides automatic centering of a pointing laser beam on a hand held cursor. The graphic display system provides a means for displaying and comparing through superposition full size overlaid graphical data and projected graphical data on a common display screen. It includes a steerable pointing laser the beam of which scans the display screen in response to a laser beam deflection circuit. The system also includes laser beam position sensing and indicating circuits which accurately measure the laser beam position. Centering of the laser beam on the cursor at the display screen is accomplished by dithering the beam uniformly about its average position in a discrete dither pattern and utilizing the dither pattern to determine misalignment of the beam's average position with respect to the center of the cursor.

Abstract: Antenna alignment in troposcatter systems is accomplished by: (1) nutating the antenna receiver beam with a sinusoidal nutation signal to induce envelope modulation on the received signal; (2) crosscorrelating the envelope of the received signal with the nutating signal; and, (3) aligning the average angle of the antenna receiver beam into the position where the crosscorrelation goes to zero.

Abstract: The generation of very high power pulses of coherent electromagnetic radiation that are continuously tunable in frequency is accomplished by means of a free electron laser in which a hollow relativistic electron beam is projected along the longitudinal axis of an evacuated drift tube. A first magnetic field expands the electron beam into an annular peripheral interaction region of the drift tube where the beam interacts with a second periodic radial magnetic field. Frequency is varied by changing the electron velocity of the electron beam or by changing the periodicity of the radial magnetic field. The device can be made to operate as an oscillator by the inclusion of resonant cavity defining mirrors within the interaction region, or as an amplifier by injecting a coherent radiation signal into the interaction region. Both oscillator and amplifier functions can be incorporated into a single device.

Abstract: A physical deterrent barrier is utilized as an integral part of an intruder detection sensor that provides surveillance of intrusions in the air space over the barrier. The sensor is a corner reflecting antenna that is coextensive with and mounts on the top of the barrier and is integrated into a barbed wire topped chain link fence by arranging appropriately spaced parallel strands of barbed wire into a V configuration so as to effect an electrical corner reflector at the system operating frequency.

Abstract: Surface acoustic wave devices such as reflective array compressors which utilize orthogonal propagation directions are improved by employing a substrate member the surface acoustic wave propagation surface of which exhibits zero temperature coefficient of delay in two orthogonal directions. Temperature compensation means are eliminated and improved performance in relaized by aligning the principal and secondary axes of propagation of the device with the zero temperature coefficient of delay directions. A single cut quartz substrate having its propagation surface defined by a plane coinciding with the Euler angles lambda=0.0.degree.; mu=125.87 (+1-6).degree., theta=45.0.degree. enables realization of the concept with reflective array compressors and other reflective quartz devices.

Abstract: A crystal reference oscillator with improved g-sensitivity is realized through the use of an appropriately oriented single axis accelerometer. Components of acceleration normal to the plane of zero g-sensitivity of the oscillator are sensed by the accelerometer which returns a correction voltage to the electronic frequency control input of the oscillator. A model is developed that permits determination of accelerometer position relative to the oscillator without prior knowledge of crystal orientation.

Abstract: Direct, real time digital data recording of thermal imagery is realized by the utilization of a computer that receives and stores bursts of high speed data from the digitized analog output of an infrared camera and simultaneously transfers a uniform flow of the data at a lower data rate to a digital tape recorder. The computer receives data only during camera active scan periods but transfers data to the recorder continuously. By making the computer output data rate substantially equal to the average input data rate real time recording is achieved. Full utilization of the data handling capacities of both the computer and the lower speed recorder is accomplished by digitizing the camera output signals in 8 bit words, combining pairs of 8 bit words for 16 bit word processing in the computer and reconverting the computer output data to 8 bit words for recording by the digital tape recorder.

Abstract: An overload warning system for fighter type aircraft combines analytical techniques of computing structural loads with flight conditions and aircraft control inputs to calculate the allowable load factor/control input on a real time basis. The flight conditions and aircraft control inputs are monitored by a microprocessor, which continuously monitors actual load factor, compares the answers with a computed allowable value and generates an output signal whenever a prescribed value is exceeded. This signal is available for transmission to aural or visual warning devices and for permanent recording.

Abstract: The conversion of simple "1" and "0" PIXELS of a binary pattern into PIXELS with numerical values dependent upon relative location in the original pattern is realized by a technique that identifies various types of PIXELS including the edge PIXELS in contiguous groups of "1" PIXELS. A multilevel pattern using the various types of PIXELS is developed and a numerical value assigned to each PIXEL. The numerical value for each PIXEL is a function of its own type and the types of its near neighbor PIXELS. Pattern measurements for the augmented pattern are less sensitive to erroneous cell deletions than for simple binary patterns. The technique is implemented by a simple mechanization for generating the augmented pattern. The mechanization is characterized by operations that are easily implemented in a real time environment using standard digital logic devices.

Abstract: A nonlinear amplitude detector generates signal amplitude from the signal's inphase and quadrature components based on a Binomial series expansion. The amplitude detector significantly reduces the processing requirement from an ideal square root operation and yet provides much improved error performance over a conventionally used linear amplitude detector. In operation, the inphase and quadrature signal components are compared for relative magnitude and the smaller magnitude signal component is squared and divided by the large magnitude signal component. The quotient from this operation is multiplied by a coefficient that is selected to provide desired amplitude error deviation characteristics. Signal amplitude is then determined by summing this product with the larger magnitude signal component.

Abstract: T.V. reception from transmitting stations located beyond the range commonly covered by T.V. receivers using conventional antennas is achieved by means of a highly directional bi-conical antenna structure that accommodates both VHF and UHF signals. Two truncated conductive cone antenna elements are mechanically connected at their apexes to the ends of an r.f. coil to provide the bi-conical antenna structure. The structure is horizontally positioned and rotatable for alignment with a desired station for optimum reception. A monopole antenna element is center tapped to the r.f. coil and the television UHF antenna lead is connected to the r.f. coil. The VHF antenna lead is connected to the bi-conical antenna structure.

Abstract: Adaptive suppression of narrow band interference is realized by a filter that automatically makes estimates of interfering signals in the frequency domain and separates the interference from the desired signal. Received analog signals are Fourier transformed in accordance with a CHIRP Z algorithm, squared, and filtered by an N point serial structural CCD to provide a smoothed power spectral density signal. The smoothed power spectral density signal is utilized to cancel interfering signals by any one of three mechanizations. One mechanization comprehends a threshold circuit that generates binary signals in response to the CCD output. The binary signals control a gate that gates strong frequency components (the estimates of the interfering frequency coefficient) from the Fourier transformer through to an inverse Fourier transformer. The inverse Fourier transformed strong frequency components are then subtracted from the delayed received analog signal.

Abstract: An extensible surface wave transmission line is fed through a coupler that utilizes the geometric properties of a planar ellipse. The coupler is in the form of a planar elliptical r.f. cavity with the r.f. input signal being fed to the cavity at the location of one ellipse focus point and the extensible output transmission line slidably traversing the cavity at the position of the other ellipse focus point. The elliptical eccentricity of the r.f. cavity is chosen such that the direct path between the ellipse foci is one half wavelength less than the ellipse major axis (or any indirect path-length between foci) thereby ensuring constructive addition of all input signals at the coupler output. The coupler is adapted to use in conjunction with aircraft antennas, transit and rail system applications, and electrical cable manufacturing quality control systems.

Abstract: A high power pulser, suitable for high energy laser and radar applications, that provides both uniform loading on the source and power combining to achieve high peak power output pulses while eliminating the customary transformer-rectifier power supply is realized by connecting a number of conventional line type AC resonant charging pulsers together in a manner that allows them to be sequentially charged from a polyphase A.C. generator and, upon command, simultaneously discharged into a load.

Abstract: Improved performance of an electronically scanned subarray antenna system is realized by tailoring the subarray pattern in a manner that reduces the undesirable effects of illumination truncation at the edge of the main array. This is accomplished by introducing variable attenuators into individual feed elements to effect an illumination intensity taper of the feed element array output. The improvement permits effective utilization of deterministic and adaptive nulling at both the main array and the subarray levels and further provides a system ability to scan over wide spatial angles with wide bandwidths and low sidelobes. The technique is adaptable to both space fed and constrained subarray antenna systems.

Abstract: A sensitivity time control circuit for radar receivers, using range gated feedback where the video signal is sampled and compared to a desired signal at intervals based upon range sweep; as the radar antenna is reversing direction, integrated averages of the video signal are used to update the sensitivity time controlled waveform.

Abstract: Uniform detection sensitivity along the periphery of an r.f. loop intruder detector system is realized by periodically electronically interchanging the input and termination ends of the system's leaky transmission line transmitting element. The intruder detector system comprises a length of leaky transmission line that encompasses the region to be protected, a receiving antenna within the protected region, an r.f. transmitter and a remotely located receiver and detector. R.F. energy is transmitted through the leaky transmission line and received by the receiving antenna and detector means to establish a normally quiescent field. Violation of the protected region by crossing the leaky transmission line disturbs the quiescent field condition and the intrusion event and the location is signaled by the detector. The effects of attenuation along the leaky transmission line are obviated by periodically switching the transmitter to alternate leaky transmission line ends.

Abstract: Crossed field amplifier collector efficiency is improved by decreasing the ratio of electron velocities to r.f. signal wave velocity at the output end of the amplifier slow wave circuit. In a preferred embodiment of the invention this is accomplished by tapering the sole emitting cathode so as to increase the cathode-slow wave circuit spacing in the output end of the interaction region prior to the collector. Alternatively, an increasing r.f. signal phase velocity taper can be used to provide the required decreased electron velocities to r.f. signal wave velocity ratio.