USA As Represented by Secretary of the Navy

Jeffrey M Speiser

Harper J Whitehouse

James M Alsup

Edwin H Wrench

James W Bond

Isaac Lagnado

William H McKnight

Robert W Means

Allan G Weber

Herbert M Federhen

Improved dynamic range resolution or accuracy analog to digital conversion ses linear prediction. An open loop or feed-forward architecture passes an analog signal to a coarse or orthodox analog-to-digital converter that provides digital signals representing a most significant part of the output signal and offers them as inputs to a digital linear predictor whose digital output signal is reconverted to analog form and fed to an analog adder. An analog delay device may be used to receive the next analog sample and, after the proper delay (if needed), feed it to the adder where the difference between the analog predicted value and the analog signal is determined and passed to a subsequent coarse or orthodox analog to digital converter. A closed loop or feedback configuration receives the analog input signal data as well as a feedback predicted value in analog form and passes the difference to a coarse or orthodox analog to digital converter. A digital delay of the digital signal may be used to insure that the digital summing of prediction and digitized error signals occurs at the appropriate times. The recirculated predicted signal is converted to analog form (unless predicted via analog means) and subtracted from the analog input signal to provide an error signal output digitized to form low order bits that correspond in time with an output of high order bits generated by a digitized prediction signal. This arrangement improves the dynamic range, accuracy, resolution or number of resolvable signal levels in an analog to digital converter.

Wide dynamic range analog-to-digital converter using linear prediction

A transform system provides a real-time implementation of the discrete Foer transform (DFT) of length N, the system being useful in sonar and radar signal processing. The input signal g.sub.n, 0.ltoreq.n.ltoreq.N-1, comprises a discrete signal, generally complex, of N samples. The system comprises an input for receiving the input signal g.sub.n and convolving in a first, input, convolver with a signal represented by the function e.sup.i.pi.n.spsp.2.sup./N , to result in a first modified signal at the output of the first convolver. Means are provided for generating the signal e.sup.-i.pi.n.spsp.2.sup./N. A multiplier receives the first modified signal and the signal e.sup.-i.pi.n.spsp.2.sup./N and multiplies these two signals its output being a second modified signal. A second, output, convolver, whose input is connected to the output of the multiplier, convolves the output signal from the multiplier with a signal represented by the function e.sup.i.pi.n.spsp.2.sup./N, to result in a discrete Fourier transformed (DFT) signal at the output. The output signal is generally a complex signal, having a real part and an imaginary part. One of the three chirps, represented by the two signals e.sup.i.pi.n.spsp.2.sup./N and the signal e.sup.-i.pi.n.spsp.2.sup./N, is multiplied by a factor of (1-i) either explicitly or in a summer for the corresponding complex operation in order to obtain the correct output phase.

Discrete Fourier transform system using the dual chirp-Z transform

A charge-coupled device (CCD) analog and digital correlator comprises identical modules, each of which is a simple analog CCD correlator with digital input and output. Circuits are included:

CCD Analog and digital correlators

A frequency-domain beamformer is used with arrays comprising M rings with a maximum of N elements per ring, the positions of the elements having rotational symmetry. An element need not be present at each position. The outputs of each of the M rings of arrays are connected to the inputs of M sets of lowpass filters, each set comprising N filters. Each filter output is an input to a sample-and-hold circuit. A temporal discrete Fourier transform (DFT) is performed on the output signal from each sample-and-hold circuit. M demultiplexers, one for each of the M sets of DFT circuits, convert their parallel input signals into serial output signals. A memory, or function generator, is used for steering. A circular convolver convolves the outputs of the demultiplexers and the memories, the outputs of the convolvers being summed in an output summer. The beamformer is used with a 3-D array such that it has rotational symmetry, that is, if rotated at some angle, the situation is exactly the same as before the rotation.

Beamformer for arrays with rotational symmetry

An image-compression system, wherein the image consists of a planar array of data points having various brightness levels, comprises a transmitter and a receiver. The transmitter comprises an analog-digital converter, for converting input analog data into digital data. The cosine transform is taken of the incoming digital data to transform the data representing various brightness levels into the frequency domain. The various frequency data points are differentially pulse code modulated, thereby removing line-to-line redundancy, the output data being in parallel form. Timing circuitry is provided for controlling the timing of the various circuits. Circuitry is provided in a receiver for the modulating or decoding of the output signal of the transmitter.

TV bandwidth reduction system using a hybrid discrete cosine DPCM

A permutation memory comprises an input control means for decoding, having plurality L of inputs for an L-bit binary number, and a plurality 2.sup.L of outputs. Means are connected to the decoding means, for initiating the read-in of the L-bit number. Means are provided for applying an input signal. A first plurality of 2.sup.L of normally open switching means are connected to the 2.sup.L outputs of the decoding means and to the signal applying means. A plurality of 2.sup.L of means are connected to the switching means, for storing a charge when a specific switching means, connected to a corresponding charge storing means, is in a closed condition. A second plurality 2.sup.L of switching means are connected to the first plurality of switching means and to the charge storing means. An output control means, connected to the second plurality of switching means, reads out the states of the 2.sup.L charge-storing means, as to the amount of charge in each. Means are connected to the read-out means, for initiating the read-out.

Permutation memories

Apparatus for performing a discrete cosine transform of an input signal, table for real-time television image processing, specifically for obtaining an acceptable picture when the number of bits of information available for describing the picture and/or the channel bandwidth are severely limited, comprising: two read-only memories, each containing a predetermined number of +1's and -1's arranged in a predetermined manner; two multipliers, each having an input from one of the read-only memories, and another, joint, input connectable to the input signal which is to be transformed discretely and cosinusoidally; two transversal filters, each having N taps, rather than twice the number (2N-1) of taps in the prior art discrete cosine filters, the input to each filter being the output of one of the multipliers; and a single-pole double-throw switch, which switches position at every shift of the samples through the filter, the output of the transform apparatus being connected to the switch arm, each of the free terminals of the switch being connected to the output of one of the transversal filters.

Apparatus for performing a discrete cosine transform of an input signal

High-speed, high-accuracy, apparatus for performing discrete Fourier and crete cosine transforms, suitable for signal processing applications. The apparatus includes a means for switching an input signal from a sample-and-hold circuit to a circuit which includes an integrator in cascade with an amplifier. The outputs of these two circuits are summed in a first summer to give one term, G.sub.0, which is proportional to the d-c component of the input signal. In parallel with the integrator and amplifier is a cascade circuit comprising a first permuter, a filter and a second permuter. A permuter is a special type of memory. The outputs of the sample-and-hold circuit and of the second permuter are summed in a second summer, to result in an output comprising the other transformed terms, G.sub.1, . . . , G.sub.N-1.

Discrete transform systems using permuter memories

A beam former, to be used with a circular array of N receiving elements, toreq.3, comprising a set of N discrete Fourier transform (DFT) devices, each one connected to one of the receiving elements, for taking a temporal discrete Fourier transform of the signals at each of the N receiving elements. Means are connected to the array of DFT devices, for connecting sequentially to each of the N devices. A reference function generator generates the sequence of terms ##EQU1## where the argument x is equal to the number of wavelengths in the circumference of the circular array at the frequency being processed, and M is several times greater than x. A means connected to the connecting means and to the reference function generator circularly convolves the signals, for example, acoustic signals, received from the connecting means and the function generator. The beam former may further comprise means connected to the convolving means for displaying the inverse discrete Fourier transform, and therefore the beam pattern.

Beam former using bessel sequences

Apparatus for performing an even discrete cosine transform (EDCT) on an it signal of size 2N, with components for an EDCT of size N, which comprises four similar modules, for performing an extended discrete Fourier transform (EDFT) on their input signals. Each EDFT module comprises means for generating the signal ##EQU1## s = - (N- 1), . . . , (N- 1), an input multiplier, a transversal filter, and an output multiplier. The apparatus further comprises a switching means, means for generating a signal (- 1).sup.n, two input multipliers, two complex attenuators, two other means for generating a signal, four output multipliers, two signal summers, and two circuits for taking the real part of an input signal.

Modular discrete cosine transform system

Two kinds of apparatus for combining N.sub.2 chirp-Z transform (CZT) modu of length N.sub.1 to perform a discrete Fourier transform (DFT) of length N.sub.1 N.sub.2. The first method uses an auxiliary parallel-input, parallel-output, DFT device of size N.sub.2 and allows the transform of size N.sub.1 N.sub.2 to be performed in the same time as is required for a single CZT module to perform a size N.sub.1 transform. The second method uses an auxiliary parallel-input, serial-output, DFT device of size N.sub.2. If the second method is implemented entirely in a single technology, such as with charge-coupled devices (CCDs), it performs the size N.sub.1 N.sub.2 transform in N.sub.2 times the amount of time required for a single CZT module to perform a size N.sub.1 transform. If N.sub.2 is a composite number, say N.sub.2 = M.sub.1 M.sub.2, the second method also permits the same hardware to perform M.sub.1 simultaneous transforms of length N.sub.1 M.sub.2.

Modular system for performing the discrete fourier transform via the

An apparatus for the generation of a two-dimensional discrete Fourier transform of an input signal developed from data within a data block, or field, having a size of N.sub.1 by N.sub.2 data points, N.sub.1 and N.sub.2 being relatively prime with respect to each other, the transforms being in a form suitable for subsequent electronic processing. The apparatus comprises an input scan apparatus connectable to the N.sub.1 by N.sub.2 two-dimensional data field comprising the input signal, such as a television viewing field. The apparatus receives and scans in proper order, or sequence, the N.sub.1 by N.sub.2 input data so that the subsequently generated one-dimensional Fourier transform of the length N.sub.1 N.sub.2 serial data string is identical to an N.sub.1 by N.sub.2 two-dimensional discrete Fourier transform of the N.sub.1 by N.sub.2 input data samples. A serial-access one-dimensional discrete Fourier transform (DFT) device, connected to the input scan generator, generates a one-dimensional discrete Fourier transform of the length N.sub.1 N.sub.2 serial data string.

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San Diego, CA, United States of America

Jeffrey M Speiser