Abstract: A pilot valve suited for use as the first stage of a large hydraulic valve system. The pilot valve virtually eliminates the steady state fluid leakage associated with orifice-based prior art systems. A pair of low noise and long life fluid restrictors are employed having flat openings thereto over which a flexible metal strip is disposed. The ends of the strip adjacent each opening are attached to one edge of rolling members whereby they can be rolled progressively off of and over the openings by an electrically driven actuator. In this manner, fluid flow through the two restrictor paths are controlled simultaneously to change the amount of fluid passing therethrough. Taps are provided in each restrictor for taking out the control fluid flow and pressure which are applied to the main valve as the driving means thereto.

Abstract: An optical element includes an ogival reflective surface which diverges an incident radiant energy beam substantially uniformly into a 2.pi. solid angle. The precise shape of the reflective surface is defined mathematically in relation to the desired solid angle of divergence and energy distribution of the incident beam. To facilitate mounting and alignment of the reflective surface in an optical system, it is formed internally of a body of optically transmissive material. The external surface of the transmissive body is shaped so as to provide normal incidence for rays reflected from the reflective surface. The element may be used as a beam diverger, or alternatively in reverse, to converge and collimate radiation.

Abstract: In a sketch pad embodying the present invention, the sensing pad has an array of generally parallel pairs of adjacent sensing conductors which, for the purpose of this explanation, will be condidered as extending in the horizontal or X direction. Each conductor has a generally triangular shape, with the base of the triangle at one edge of the pad and the apex at the opposite edge. The conductors in each pair are complementary, that is, their bases are at opposite edges of the pad. Preferably the stylus used with the sensing pad has an electrode at its tip to which it applies an alternating current signal at a frequency that is suitably high for capacitive coupling to the sensing pad. To ascertain the X position of the stylus on the pad, the right or left set of conductors is connected to sensing circuitry and the other of these two sets is grounded. The sensed voltage then corresponds to the X position.

Abstract: In a spread-spectrum direction-finding system, the outputs of the several antenna elements (10a-d) are progressively translated in frequency by a chirped local oscillator (14) and mixers (12a-d) and applied to a two-dimensional dispersive filter (18), which time compresses the results of single-frequency components in the antenna-element outputs to narrow pulses. Limiters (24a-d) remove any strong narrow-band components that are compressed by the dispersive delay line (18) so that further processing to detect a spread-spectrum signal is not degraded by the presence of narrow-band signals. The use of a common two-dimensional delay line (18) to provide the time compression avoids the need to maintain phase tracking among a plurality of separate parallel one-dimensional dispersive delay lines.

Abstract: An optical decoder to permit differentiating between at least two flashing spots displayed on a cathode ray tube screen is provided by a photosensor and an electrical circuit which is responsive to the absence of flashes during a flashing sequence which is different for the two spots and not distinguishable by the naked eye.

Abstract: A signal-acquisition system (10) for a circular antenna array (12) includes a two-dimensional compressive receiver (18) that performs a two-dimensional Fourier transformation in time and position on the outputs of the array. Each of the outputs of the compressive receiver (18) is fed to input ports of several processing units (24), which multiply them by an appropriate time-dependent function. The resultant modified signals are then processed by Butler matrices (30) that together have a matrix of output ports (32). Each output port is associated with a different combination of azimuth and elevation angles. A signal source at given azimuth and elevation angles with respect to the array (12) causes its greatest response in the output port (32) associated with those angles.

Abstract: The invention of this disclosure comprises a system that simultaneously determines the frequency and direction of arrival of incoming signals. The apparatus of this invention comprises a layered half space dispersive delay line which is utilized as a beam forming element in a device that performs a two-dimensional Fourier transform on a function which is both time and space dependent.A pulse appears at the end of the delay line at a time which corresponds to the frequency of the incoming signal and the position of the pulse along the edge of the delay line is related to the direction of arrival of the incoming signals.

Abstract: A pneumatic time delay valve primarily adapted for use in the ejection system of electronic or optical countermeasure devices and the like wherein an explosive squib is employed to create a momentary charge of high pressure gas used to depress the firing pin on the device to activate the device and also to push the device out of an ejection tube. The invention comprises means for splitting the pressurized gas into a first conduit communicating with the firing pin and a second conduit communicating with the device to apply the ejection pressure thereon and a time delay valve disposed within the second conduit for delaying the application of the gas to the device. During the time delay period, a piston is forced down a cylindrical bore forcing metering fluid through an orifice.

Abstract: A flexible circuit (28) containing the grid connectors of a digitizer tablet (10) converge in a transition region (48) disposed in an unshielded area. However, the positional inaccuracies that would otherwise result from the exposure of the non-parallel conductors to radiation from the tablet's stylus (24) are reduced because the flexible circuit (28) is kept in close proximity to a metal plate (32) throughout the transition region (48) in which the conductors depart from a parallel configuration.

Abstract: Signals from antenna elements (14) of a rectangular array (12) are translated in frequency by mixers (16) fed from a chirped local oscillator (19). The resultant signals are fed to the first of two groups (20 and 36) of two-dimensional delay lines connected in series at right angles to each other. The two-dimensional delay lines are dispersive, having a linear relationship of delay to frequency, and the sweep rate of the local oscillator (19) is such that the signals caused by a given frequency component at the mixer input ports are completely compressed in time when they reach the output ports (46) of the delay lines of the second group (36). As a consequence, the device performs a three-dimensional Fourier transformation from time and two spatial dimensions to temporal frequency and two dimensions of spatial frequency. When fed by a two-dimensional antenna array, the output of the device can readily be interpreted as indicating the direction of the source and the frequency at which it is radiating.

Abstract: A frequency-and-direction-finding system (10) employing a circular array (12) performs a two-dimensional Fourier transformation in space and time on the signals from the individual elements. The results of the transformation are fed to multipliers (22) that multiply them by correction factors that are derived from antenna patterns of the array but do not include the bearing-dependent factors in those systems. The result is an ensemble of values whose relative phases represent a spatial frequency proportional to the bearing angle of the source. Accordingly, a second fast-Fourier-transform circuit (26) operating on this ensemble of values produces an output only on an output port corresponding to the bearing angle of the source.

Abstract: A receiver employs fast-Fourier-transform modules to process the received signals in the frequency domain. It samples the input signal at a high sampling rate to cover a broad input bandwidth, but it transforms the sampled input signals in short segments, segments that cover time durations considerably shorter than the duration of the impulse response of the receiver's tuner filter. The transform of the sampled input signal is multiplied by a Gaussian transfer function to reduce the amount of information contained in the signal, and the values of the resultant frequency-domain sequence are reordered in such a manner as to correspond to resampling in the time domain at a slower rate. This results in coverage of the time duration of an input segment by a relatively small number of samples.

Abstract: In a digital communications system, one of two tones is selected for each bit, a first tone for a "0" and a second tone for a "1"; the tones are unique for each bit. The tones for all of the bits of a byte are sent simultaneously, in a burst or pulse. At the receiver, a parametric model-based spectrum analysis is performed to find the constituent frequencies which produced the composite spectrum. This spectrum analysis uses autoregressive parameter estimation techniques to determine the most likely combination of frequency components which would have generated the composite spectrum. The combination of frequency components so found is then decoded to yield the corresponding bit values represented by those frequencies. The use of autoregressive spectral analysis techniques to recover the frequency components in the composite signal provides both bandwidth compression (by virtue of increased resolution) and faster signalling rates in transmitting just such signals.

Abstract: A system for indicating the direction of a source of radio waves received by a circular antenna array (12) includes a Butler matrix (18) that receives the array outputs and feeds the resultant matrix outputs to correction circuits (22) whose transfer functions are the inverses of the direction-independent factors of antenna patterns generated by antenna elements driven at relative phases that advance around the array at rates that complete an integral number of cycles in one circuit of the array. The resultant corrected signals are fed to a compressive receiver (26), which accordingly generates an output on an output port whose position indicates the direction of the source of the signal.

Abstract: The effects of impulse noise on the operation of a microprocessor-controlled Loran-C receiver are reduced by muting or attenuating the received signals in the front end of the receiver ahead of the receiver gain during a time period which preceeds the start time of the pulses being tracked. The attenuation is selectively removed after the start time of each pulse being tracked to permit the receiver to perform its time difference of pulse arrival measurements in the normal manner. The attenuation is also selectively removed during those time periods in which the receiver performs its envelope slope, skywave/groundwave and other such samplings. The attenuation is provided by a muting circuit which is controlled by a time gate signal that derives from the microprocessor of the receiver.

Abstract: A D-type flip-flop (10) receives the D input on an input line (14) of a transfer gate (12) that also receives the flip-flop clock signal. A state gate (20) forwards the transmission-gate output when the signals on two of its input lines (22) and (24) remain true. To reset the flip-flop asynchronously, a false signal is imposed on one of the input lines (22) of the state gate (20). By coordination of a second clock signal, which is applied to a second transmission gate (34), with the reset signal, the reset condition is held until the next clock pulse on the first transmission gate (12). The flip-flop ordinarily operates as a dynamic circuit, but, in order to maintain the reset condition in circumstances in which the reset state is to be maintained for an extended period of time, a latch gate (26) is enabled by a true signal on one of its input lines (32) to feed the reset output of the state gate 20 to one of its input terminals (24 ) so as to latch the flip-flop in the reset state.

Abstract: A data stack for storing data at sequential locations in a memory and for transmitting the data in modes defined by commands from a host data processing system. A random access memory stores the data in sequential locations at addresses selected by a state signal generator comprising read only memory. The state generator generates the addresses and read/write control signals for the random access memory in response to the commands from the host system and a previous address provided by the generator.

Abstract: The present invention pertains to .[.an apparatus and.]. .Iadd.a .Iaddend.method, in conjunction with standard monochrome and color television receivers, for the generation, display, manipulation, and use of symbols or geometric figures upon the screen of the television receivers for the purpose of .[.training simulation, for.]. playing games.[., and for engaging in other activities.]. by one or more participants. The invention comprises in one embodiment a control unit, connecting elements and in some applications a television screen overlay mask utilized in conjunction with a standard television receiver. The control 10 unit includes the control, switches and electronic circuitry for the generation, manipulation and control of video signals which are to be displayed on the television screen. The connecting elements couple the video signals to the receiver antenna terminals thereby using existing electronic circuits within the receiver to process and display the signals.

Abstract: A hand held paper pager is disclosed in which a transmitted message is displayed in alpha/numeric form by a precessing display which moves the received message across the display in a continuous fashion so that the display need be only large enough to present a relatively small portion of the total message at any given time. In one embodiment a dot matrix LED display is used and is driven by a recirculating shift register memory to provide the precession of the message as a result of the recirculation. In another embodiment the pager may also include a message entry section in which the precessing display is used to present and edit the message prior to transmission either via an acoustic telephone link to a remote transmitter, or directly from a transmitter carried in the pager/encoder package.