Abstract: An analog TV system includes a transmitter which produces a horizontal unique pulse sequence during each horizontal blanking interval. The pulse sequence is amplitude modulated between two levels to define a horizontal unique word for horizontal synchronization. The frequency of the pulse sequence is selected for use by the receiver section as the color subcarrier phase reference. The average level of the pulse sequence is set at the transmitter and used at the receiver for DC restoration in a clamping circuit. The peak amplitude of the pulses of the pulse sequence define a reference level against which a receiver producing local reference is compared for AGC.

Abstract: A cipher system in which a key is initially inserted into a shift register and the serial output of the shift register is added to the plain text message and the sum is fed back into the serial input of the shift register. Parallel outputs of the shift register are led to a logic function which transforms the multiple inputs into a single output, the value of which is evenly distributed among the possible combinations on the input. The logic function output is then added to the message to produce the enciphered message. In the decipherer, the deciphered message is added to the serial output of the shift register to produce the serial input to the shift register. Otherwise, the decipherer closely resembles the encipherer.

Abstract: PN sequence generators used in the scrambling and descrambling circuits at remote locations are periodically preset to the same value in order to maintain synchronism, with the preset value being also periodically changed. The preset value can be transmitted to the scrambling and descrambling circuits over a privacy channel once per frame and stored in storage registers associated with each of the scrambling and descrambling circuits. The stored starting state values can be loaded into the PN sequence generators as often is desired to maintain proper synchronization, with the stored values themselves being changed at a rate in accordance with the desired degree of security.

Abstract: A method of detecting and correcting received values of a pitch period estimate of a speech signal for use in a speech coder or the like. An average is calculated of the nonzero values of received pitch period estimate since the previous reset. If a current pitch period estimate is within a range of 0.75 to 1.25 times the average, it is assumed correct, while if not, a correction process is carried out. If correction is required successively for more than a preset number of times, which will most likely occur when the speaker changes, the average is discarded and a new average calculated.

Abstract: A method and apparatus for one-way subscription television service control which allows the subscribers to subscribe in advance to a variety of programming or to select programming oa a pay-per-view basis.

Abstract: A satellite clock system in which the frequency of the onboard satellite clock, which is implemented as a relatively high uncertainty voltage-controlled oscillator, is corrected in accordance with a high-stability, low-uncertainty terrestrial clock. Metering bursts are transmitted from the earth station to the satellite where portions of the metering bursts are truncated due to misalignment between the bursts and the synchronization windows timed by the onboard oscillator of the satellite. The patterns of the received bursts which are re-transmitted by the satellite are compared with a stored pattern and a phase shift value determined in accordance with the number of incorrect comparisons. The phase error measurement value is utilized to control a programmable divider connected between the high-stability, low-uncertainty oscillator and the burst transmitter to thus provide a short-term correction.

Abstract: The invention is a method of orienting a satellite in a geosynchronous orbit so as to direct a beam from an antenna mounted on the satellite to cover a desired target site, and pointing the beam axis at a desired bore site target. One embodiment of the method according to the invention includes a step of orienting the spin axis of a geosynchronous satellite at a direction angle which equals the inclination angle of the current orbital plane plus an adjustment or correction angle (.beta.), when the inclination angle is greater than zero. The correction angle is determined using one or both of the following equations:.beta.=BS-tan.sup.-1 {[ sin (bs-I)]/[6.61-cos (bs-I)]},or.beta.=.vertline.-(BS-tan.sup.-1 {[ sin (bs+I)]/[6.61-cos (bs+I)]}).vertline.,where, BS=the elevation angle of the bore site target in spacecraft coordinates, bs=the latitude of the bore site target, I=the inclination angle of the orbital plane with respect to the equatorial plane, and .beta.

Abstract: A switch matrix with a delay feature for temporary storage of burst communications on-board a satellite. Additional input and output ports are added to a conventional switch matrix in such a manner that, if delay is desired, the additional output ports loop their output signals through acoustical delay devices to the additional input ports whereupon they enter the matrix either for further delay or for transmission. If delay is not desired, signals pass through the matrix in a conventional manner.

Abstract: A microstrip antenna array having broadband linear polarization, and circular polarization with high polarization purity, feedlines of the array being capacitively coupled to feeding patches at a single feedpoint or at multiple feedpoints, the feeding patches in turn being electromagnetically coupled to corresponding radiating patches. The contactless coupling enables simple, inexpensive multilayer manufacture.

Abstract: In an adaptive differential PCM (ADPCM) system transmitter, three quantizers provide, respectively, 3, 4, and 5-bit quantization at the signal sampling rate. Each quantizer produces, in response to an input signal sample, a coded signal I(n) in the form of a bit sequence the number of bits in the coded signal from each quantizer being different. The number of bits comprising the coded signal is proportional to the bit rate. The bit rate can thus be altered by switching the codec output to selected ones of the adaptive quantizers. To eliminate quantizing distortion during bit rate transitions, one adaptive quantizer is caused to operate in the dominant mode, to receive the input signal sample and produce the coded signal I(n). At the same time, the other adaptive quantizers operate in a secondary mode to update their step-size .DELTA.(n) on the basis of the quantized signal produced by the dominant mode quantizer.

Abstract: A BPSK Costas-type PLL circuit in which the circuit is positively prevented from falsely locking on to the input signal and in which the need for a complex lock detector is eliminated. The output levels of both the 0.degree. and 90.degree. sub-loops of the circuit are detected and a difference formed between the detected outputs. When the difference exceeds a predetermined reference level, it is determined that true locking has occurred, whereupon a sweep generator, used in achieving initial lock, is decoupled from the PLL circuit.

Abstract: An echo canceller comprising an adaptive finite impulse response filter receiving a receive signal and having its output subtracted from a send signal, a non-linear device for attenuating low level signals of the send signal and a noise injector for injecting noise into the send signal proportional to a dynamically measured background noise in the subtracted output. The non-linear device and the noise injector are disabled when the receive signal is below expected noise level or the send signal is at a high level relative to the receive signal.

Abstract: A method of measuring input-backoff to an amplifier in a time-division multiple access (TDMA) communication system having a carrier recovery segment and a clock recovery segment prior to a data segment in a traffic burst. A monitoring station transmits a CW pilot signal within the amplifier's bandwidth. In the guard time between bursts, the monitoring station measures the unsuppressed pilot level output by the amplifier. While a ground station is transmitting an unmodulated carrier during carrier recovery or a carrier modulated at the clock frequency during clock recovery, the monitoring station measures the suppressed pilot level, suppressed by the non-linear interaction of pilot and carrier. The amount of pilot suppression is related to the input power back-off of the carrier by a previously measured or a theoretically derived relationship.

Abstract: A technique for packaging and integrating of a microwave integrated circuit (MIC) or monolithic microwave integrated circuit (MMIC) with a waveguide uses a printed conductive circuit pattern on a dielectric substrate to transform impedance and mode of propagation between the MIC/MMIC and the waveguide. The virtually coplanar circuit pattern lies on an equipotential surface within the waveguide and therefore makes possible single or dual polarized mode structures.

Abstract: An echo canceller with extended frequency range for acoustic echoes comprising an adaptive finite impulse response filter receiving the receive signal below a cross-over frequency and predicting the echo of this signal across the echo path, a subtractor for subtracting the predicted echo form the send signal below the cross-over frequency, and an adder for combining the low frequency output of the adder with the send signal above the cross-over frequency to form the send signal to be transmitted.

Abstract: A method of preparing an active surface layer on a semi-insulating GaAs substrate comprising the steps of ion implanting a surface layer with silicon to form an n-type active layer and ion implanting a buried diffusion layer beneath the active layer with boron to prevent defects in the substrate from influencing the active region. The method is particularly useful for GaAs MESFETs.

Abstract: In an on-board satellite clock correction system of the type wherein phase errors between the satellite clock and a ground-based clock are determined and a clock correction value sent to the satellite, the clock correction value is determined by curve-fitting the determined phase errors in accordance with a polynomial function, updating the polynomial function coefficients so as to minimize discrepancy between the determined phase errors and those according to the polynomial function, predicting a clock drift in accordance with the polynomial function and calculating an error correction value in accordance with the predicted clock drift.

Abstract: An echo canceller for a teleconferencing device is herein disclosed in which a first attenuator limits the dynamic range of a composite speech-echo input signal. A second attenuator, having a gain equal to that of the first attenuator, alters the gain of the emulated echo signal produced by an AFIR filter. The gains of both the first attenuator and the second attenuator are controlled by a common automatic gain control device, which alters the gains as a function of both the dynamic range of the input composite signal and a feedback signal from the output of the first attenuator. This matched attenuator construction allows the AFIR filter to operate within its dynamic range while also limiting the range of the input speech/echo signal. The echo canceller may further comprise a third attenuator which is disposed in the adaptive feedback loop of the AFIR filter. The third attenuator has a gain inversely proportional to the gains of both the first attenuator and the second attenuator.

Abstract: A frequency conversion interface is disposed between the main and subreflectors in a multiple beam antenna system so that the antenna system amplification factor will be defined by m=(f.sub.1 /f.sub.2).multidot.(.omega..sub.1 /.omega..sub.2), to permit large main reflector to subreflector area ratios while maintaining small amplification factors.

Abstract: A coplanar waveguide quadrature hybrid is herein disclosed which produces even E-field symmetry about the center line of transmission during both even-and odd-mode excitation. In a first embodiment of the present invention, a first coupling element of a generally elongated shape is bifurcated and is interconnected at its ends to form a first rectangular coupling element. A second rectangular coupling element is disposed within the first rectangular coupling element. In a second embodiment of the present invention, one of the short sides of a first rectangular coupling element is broken and is cross-coupled to a third rectangular coupling element similar to the second rectangular coupling element, the third rectangular coupling element being disposed within a fourth rectangular coupling element similar to the first coupling element. The fourth rectangular coupling element is then directly connected to the second rectangular element to form a composite coupling element.