Abstract: An MTI radar system transmits pulses with variable interpulse time periods and is structured with a lattice filter to process return signals to identify targets while substantially rejecting static and moving clutter. The MTI radar system also operates to reject adverse effects of transmitter instability in the processing of return signals. The MTI radar system is applied as an airport traffic control in which aircraft are detected as targets.

Abstract: A radar antenna system, adapted to be supported on an aircraft for surveillance, employs a nonconducting disk radome structured with aerodynamic fairing and otherwise to produce relatively low aerodynamic drag. A plurality of struts are used to secure the disk radome to the aircraft with the disk radome generally extending in a solid horizontal reference plane. A plurality of elongated, relatively low gain radiating elements are supported by a ground-plane box within the disk radome, with the radiating elements distributed across the disk radome and disposed to radiate generally in the vertical direction. An electronic system is supported within the ground-plane box, and it includes respective transmit/receive circuits which send and receive radio frequency signals to and from the radiating elements. Power cables extend through the struts to couple signals between the electronic system in the disk radome and radar system level circuitry located externally of the disk radome.

Abstract: A wear ring assembly for an air gun includes a support ring having a receiving recess of a first length formed in a surface of an end of the support ring. An elastic ring is adjacent an end of the receiving recess. A wear ring seats in the receiving recess and is of a second length, greater than the first length, such that a portion of the wear ring overlaps the end of the support ring, thereby covering and deforming the elastic ring. The wear ring is formed of a thin, low-friction, wear-resistant plastic material having dimensions such that the wear ring does not plastically yield during installation into the receiving recess. Installation is accomplished by attaching a core tool adjacent the seal groove. The wear ring is installed with an expanding pusher tool, over the core tool and into the receiving recess.

Abstract: A seismic air gun includes a body, a main chamber, two ports, several air passageways, a shuttle, a return device, and a firing device. The main chamber is within the body. The two ports are in the main chamber. The ports lie along a common axis. The air passageways connect a high pressure air source to the return device, the main chamber, and the firing device. The shuttle slides along the common axis between an open position, in which the main chamber is open, and a closed position, in which the main chamber is closed. The return device biases the shuttle toward the closed position. The firing device causes the shuttle to move from the closed position to the open position whereby pressurized air is released simultaneously from the two ports and in opposite directions.

Abstract: A seismic source apparatus 10 includes body 12, cap 22, actuator 24, and shuttle 26. Body 12 includes a main chamber 14 that is formed therein and adapted to receive a charge of compressed air. Actuator 24 is preferably a solenoid actuated valve, capable of rapidly opening and closing in response to an electrical signal. Seismic source apparatus 10 includes a solenoid chamber orifice 38 that is positioned within a fill passage 34 to enable fluid communication between fill passage 34 and solenoid chamber 40. Solenoid chamber orifice 38 and solenoid chamber 40 are configured to provide a quick burst of high pressure air through actuator 24 when actuator 24 is opened in order to start the shuttle 26 in motion, while restricting the flow of air from main fill passage 34 and main chamber 14 into the actuator 24 so that the pressure in the main chamber 14 remains high enough to emit a suitable bubble, and so that shuttle 26 is not prevented from closing.

Abstract: A bus structure for a real-time multiprocessor computing system connects, for example, 16 processors, each having only two bus interfaces, without degrading processor performance or requiring partitioning by application programmers. The processors are divided into groups with each combination of two groups connected together and to memory and peripheral units via a different bus. In a computing system having first, second, third and fourth processor groups and first and second memory groups and peripheral groups, a first bus connects the first and second processor groups together and to first groups of memory and peripheral units, a second bus connects the first and fourth processors together and to second memory and peripheral groups, a third bus connects the second and third processors to the second memory and peripheral groups and a fourth bus connects the third and fourth processor groups to the first memory and peripheral groups.

Abstract: A dual shuttle air gun for generating maximum acoustic output for seismic testing having a housing with an air chamber formed therein and a chamber opening that opens 360 degrees around the periphery of the body is disclosed. The two shuttles are positioned around the housing axially displaced from each other, but close enough to allow the end faces of each shuttle to come into close proximity with each other. When the air gun is fired by the activation of a solenoid, compressed air flows into a firing chamber formed between the first shuttle and the housing causing the first shuttle to begin opening. When the first shuttle moves, the end faces of the two shuttles are exposed to the compressed air from the primary chamber. This causes the two shuttles to rapidly move away from each other providing for very quick release of the stored compressed air. When the solenoid is deactivated, the two shuttles are forced back into a prefire condition over the 360 degree opening.

Abstract: The disclosure relates to a solenoid valve for an air gun which substantially increases the rate at which maximum air flow is achieved. The new valve structure includes a coil actuated plunger, which is preferably solid and formed of a magnetically permeable material and closes an annular 360 degree port opening between the valve inlet and valve outlet when in the unactuated state. This plunger position is maintained by a biasing spring which forces the forward annular sharp plunger edge against a face seal in the nose of the valve, thereby sealing the valve input port from its output port. Upon actuation of the solenoid valve coil, the plunger is moved against the bias of the spring very rapidly, thereby speedily uncovering the channel between inlet and outlet and permitting rapid 360 degree communication between the inlet and outlet to permit maximum air flow therebetween and out of the outlet port.

Abstract: The present invention comprises a multi-barrel seismic source air gun module for use in a marine environment, preferably comprising a plurality of air gun barrels symmetrically disposed in a single plane about and rigidly secured to a control head containing means for actuating said barrels.

Abstract: The disclosure relates to a solenoid valve for an air gun which substantially increases the rate at which maximum air flow is achieved. The new valve structure includes a coil actuated plunger, which is preferably solid and formed of a magnetically permeable material and closes an annular 360 degree port opening between the valve inlet and valve outlet when in the unactuated state. This plunger position is maintained by a biasing spring which forces the forward annular sharp plunger edge against a face seal in the nose of the valve, thereby sealing the valve input port from its output port. Upon actuation of the solenoid valve coil, the plunger is moved against the bias of the spring very rapidly, thereby speedily uncovering the channel between inlet and outlet and permitting rapid 360 degree communication between the inlet and outlet to permit maximum air flow therebetween and out of the outlet port.

Abstract: A seismic energy source air gun has a body with an air chamber formed therein that opens 360 degrees around the periphery of the body. A sleeve-type shuttle covers the opening in a pre-fire condition. When the air gun is fired, the shuttle moves rapidly away from the opening providing a large area for compressed air held in the chamber to escape. This very quick release maximizes the acoustic output. The movement of the shuttle is ultimately controlled by a solenoid which, when activated, causes the shuttle to move away from the 360 degree opening and when deactivated permits the shuttle to move back into the pre-fire position over the 360 degree opening.

Abstract: An adaptive filter for enhancing the discrimination of targets from clutter and noise and suitable for use in a pulse doppler radar signal processor which processes successive echo pulse period signalling in accordance with range cell samples is disclosed. One embodiment of the filter has a delayed lattice configuration including a plurality of cascadedly coupled lattice stages, each adapted to operate on the range cell samples of first and second complex signal inputs. The adaptive filter embodiment provides rapid and low cost updating of the lattice stage weighting coefficients so that varying clutter spectrums may be effectively dealt with. Moreover, the lattice filter embodiment is insensitive to average clutter motion and to transmitter phase and gain instabilities. It further permits the use of variable interpulse period operation in radars that are unambiguous in range.

Abstract: Disclosed is a seismic source device, known in the industry as an air gun, having shuttle control for allowing a predetermined discharge of compressed air into water for purposes of seismic exploration. The shuttle is controlled by valve means for closing the exhaust ports before all of the compressed air in the firing chamber of the air gun is exhausted. By preventing further discharge of air, with little or no loss in acoustic output, secondary pulses are greatly reduced, thereby enhancing the operation of the entire system. Further by preventing all the air in the firing chamber from being discharged, the system becomes more efficient and more cost effective.

Abstract: Disclosed is a seismic source device, known in the industry as an air gun, having shuttle and external sliding valve control for allowing a predetermined discharge of compressed air into water for purposes of seismic exploration. The shuttle is controlled by air pressure to move it upward, thereby permitting compressed air in the firing chamber to exhaust through exhaust ports. The external sliding valve had been held in a downward position by air pressure supplied from the firing chamber, compressing a spring. As the firing chamber pressure drops, the compressed spring expands, forcing the sliding valve to move upward, closing the exhaust ports. By preventing further discharge of air, secondary pulses are greatly reduced, with little or no loss in acoustic output, thereby enhancing the operation of the entire system. Further, by preventing all the air in the firing chamber from being discharged, the system becomes more efficient and more cost effective.

Abstract: Spurious frequencies are eliminated in a direct frequency synthesizer by means of a feed forward correction circuit. The improved direct frequency synthesizer of the invention includes a series adder, clocked register, a D/A converter and a phase corrector. The adder is inputted by a digital control increment and the output of the register. The system clock frequency is divided down by a smoothing counter that in part controls the phase of the output signal. Spurious frequencies are manifested by overflow of the register. The register overflow is converted to an analog signal by the D/A converter. The system output is provided by a voltage controlled oscillator that is controlled by an amplifier which is responsive to both the smoothing counter output and the analog output of the D/A converter. Additionally, the D/A converter is sampled twice for every cycle of output frequency, resulting in a doubling of the output frequency for a given D/A converter.

Abstract: There is disclosed a direction-sensitive doppler radar particularly for detecting intruders into a protected area which is free of the mechanically controlled parts of the prior art. To distinguish between an intruder and the clutter produced by the movement back and forth of trees or like growth in a wind, the doppler side bands of the clutter produced by the growth moving or swaying in opposite directions are processed so that they counteract each other. The incoming signals, both clutter and from intruders, are converted into I and Q quadrature signals, frequency or sensitivity compensated and passed through a variable bandwidth bandpass filter whose bandwidth is reduced at the low-frequency end as the clutter increases. The I and Q signals are then each converted into quadrature I3 and I4 and Q3 and Q4 signals respectively, and the products I3Q4 and I4Q3 derived and subtracted. The resulting signal produces the alarm if there is an intruder and indicates the direction of movement of the intruder.

Abstract: Method and apparatus for determining and applying a feedback current to the two sense windings of a vehicle mounted flux gate compass in order to provide a compensating magnetic field to cancel out the effect of local magnetic disturbance field(s) produced by the vehicle. Two zero crossing detectors for each channel respectively associated with the two sense windings indicate when the output from a sense winding passes through a null. This indication is used to enable a sample and hold circuit for the voltage on the opposite coil. During the calibration sequence the vehicle traverses a complete circular path wherein each coil passes through two nulls resulting in two voltages being sampled and held for each coil. The two pairs of voltages are then averaged, which then results in two resultant voltages which are representative of the lateral and longitudinal components with respect to the vehicle of the disturbance field.