Abstract: A synchronization detecting system for data transmission in which a two-dimensionally modulated signal is received by way of a demodulator. In a training sequence for a two-dimensional modulation modem, a point of transition from an alternation to a pseudorandom symbol sequence is detected by producing a sum of the vectors of two signals which are remote from each other by a period of two samples, or a difference therebetween. Whether the detection of the transition point has been correct is decided utilizing the alternation.

Abstract: A signal pre-processing method for detecting valid Manchester-encoded activity on a line carrying Manchester-encoded data signals to an inexpensive Manchester-decoding receiver. Detection is provided by monitoring both a positive-level presence and a negative-level presence to determine whether the received Manchester-encoded signal exceeds a predetermined positive voltage or falls below a predetermined negative voltage. Following detection of such line activity, the received signal is determined to be validly Manchester-encoded if it first crosses a predetermined positive level or a predetermined negative level after having first previously crossed the opposite level within a time interval of 3/4 to 11/4 of the inter-bit period of the received data signals.

Abstract: A method of sending self-clocking data characters and control characters in a sequence from a first communications node to a second node includes the steps of: encoding each data character as respective code pairs of the form 0XX . . . X1 and 1XX . . . X0 where the X's are the zero and one bits of the data character; encoding each control character as respective code pairs of the form 0XX . . . X0 and 1XX . . . X1 where again the X's are the zero and one bits of the control character; and transmitting, for each character in said sequence, the particular code in that character's code pair whose first code bit is the opposite of the last code bit of the immediately preceding character in the sequence.

Abstract: A facility is provided for recovering the clock and data from a data stream transmitted in the bi-phase code even if the data stream contains no sync bits and if the transmission speed varies.For clock recovery, a nonretriggerable monostable multivibrator is triggered at each phase change, so that the inserted phase changes are rendered ineffective. The clock is used to control a memory which receives the valid data of the transmitted data stream at the correct instant and keeps this data constant during one clock period.

Abstract: Radiation hard, N-channel MOS devices comprising active regions surrounded by field oxide protected by an underlying region of heavily doped p-type material. The guard region is doped heavily enough to provide field inversion voltages in the range of 50 V to 60 V prior to irradiation. The guard region is separated from the source and drain regions to provide acceptably high breakdown voltages. The devices are produced with minor variations to well known, high density local oxidation of silicon-type processes.

Abstract: An tuner unit is provided for communications receivers with automatic self-balancing of the individual high frequency filter circuits. An assigned frequency applied to the desired receiver channel is fed to the antenna input during the automatic balancing process. The voltage of this assigned frequency picked up at the output of the filter circuits changes according to a stepwise increase of a tuning voltage controlled by a microprocessor. The tuning voltage is applied to the filter circuit to be balanced via a digital-analog converter and via a switching means controlled by the microprocessor. The automatic balancing is provided by switching the switching means successively to connect to the individual filter sections.

Abstract: A multipath distortion reducing circuit particularly adapted for use with stereophonic receiving circuits in which the amount of mixing between right and left channels is reduced. In accordance with the invention, the envelope of the received FM signal is AM detected, and the envelope detected circuit is multiplied by the FM detected signal differentiated to provide a distortion cancelling signal. The distortion cancelling signal is summed with the detected FM signal to provide an output having a reduced multipath distortion component.

Abstract: The baud rate of a digital signal is estimated using a method based on a mean squared error determination. The disclosed method fits a sine wave curve to the digital signal and varies its frequency until the mean squared error is a minimum, wherein the error is defined as the distance of the sine wave curve from its center line at each transition of the digital signal. The disclosure includes an apparatus for carrying out the method of the invention. In addition, the method is suitable for execution as a stored program within a high-speed signal processor.

Abstract: A radar warning receiver includes means for distinguishing pulsed or continuous fixed frequency radar signals emanating from a radar transmitter from variable frequency signals such as those radiated from a nearby superhomodyne receiver. This invention includes a superheterodyne receiver having a local oscillator that is repeatedly varied in frequency over a range of frequencies sufficiently large and at a rate fast enough to cause any signals within an input range of frequencies to be detected by a sensitive, limited bandwidth detector. If an input signal is fixed in frequency, that signal will be detected at the same time during successive sweeps of the local oscillator, and a correlated output will be generated; otherwise, an uncorrelated output will be generated. If the number of correlated outputs equal or exceed the uncorrelated outputs detected, then an alarm is provided.

Abstract: Digital Data receiving apparatus includes means for adjusting the timing of the sampling instants. A phase controlled oscillator (PCO 19) provides timing signals for sampling the received signal and is controlled, at the commencement of a received signal, by a timing initialization circuit (17) responsive to repetitive phase alterations in a training sequence. The timing initialization circuit (17) includes a plurality of Discrete Fourier Transform (DFT) circuits (23) responsive to frequencies dependent on the power spectral densities of the received signal, which received signal may be modulated at a normal rate or a fall-back rate. The DFT circuits (23) measure the correlation of locally-generated frequencies with the incoming samples for a predetermined number of such samples to produce a plurality of complex signals. A selector circuit (24) selects a pair of the complex signals dependent on the modulation rate.

Abstract: A DC current injectable double balanced diode ring mixer circuit for radio frequency (RF) application. The diode ring includes eight diode elements and defines eight terminals including four symmetrical DC injection ports in conjugate pairs interleaved with four symmetrical RF inputs for phase and anti-phase application.

Abstract: An MOS voltage divider is described which is particularly useful for dividing a relatively high voltage (e.g., 21 volts). Capacitance division is employed, thus, the divider consumes substantially no current. Capacitors are fabricated from first and second layers of polysilicon and an intermediate layer of silicon dioxide. Common centroid geometry is used to compensate for process variations.

Abstract: In a distributed IMPATT structure, power is coupled out through a side contact. That is, in previously proposed distributed IMPATT structures the gain medium (the active region of the IMPATT) operates as a transmission line. The prior art has attempted to couple output power from the gain medium through an end contact, i.e. through a contact which intercepts the primary direction of energy propagation of the active medium. In the present invention, a side contact extends along the whole active region in a direction which is parallel to the principal direction of propagation of the energy in the active medium. Thus, the side contact plus the active region together can be considered as a single transmission line.The present invention can be configured as an oscillator, amplifier, phase shifter, or attenuator. When configured as an oscillator, multiple short active regions can be sequentially coupled to a single long microstrip, which serves as the side contact for each of the active regions.

Abstract: An insulated-gate field-effect transistor which may be of the D-MOS or V-MOS type includes a source region (1) which is surrounded by a second region (2) of opposite conductivity type, itself surrounded by a third region (3) associated with the transistor drain (4). An insulated gate (12) of the transistor is present on a channel area of the second region (2) between the source region (1) and a first part (31) of the third region (3). The third region (3) also has a surface-adjoining second part (32) which is remote from the first part (31) and preferably has a lower doping concentration than the second and source regions (2, 1).