Abstract: A decoy radar transmitter governed by a control signal derived from a main radar transmitter to emit radiation which is phase coherent with the carrier frequency of the main radar transmission is disclosed. A section of the main radar transmitter generates a control signal compositely formed by the combination of derived signals including a phase coherent subharmonic of the carrier frequency of the main radar, a frequency shift keyed signal and a signal having a power content. The frequency shift keyed signal is representative of a phase coded modulation sequence of the carrier frequency transmissions, each frequency fo the frequency shift keying corresponds to a phase polarity of the phase coding. A single coaxial cable conducts the composite control signal to the decoy radar transmitter. Upon receiving the composite control signal, a section of the decoy radar transmitter separates the power signal from the received control signal for use in energizing the decoy radar transmitter.

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: A multiplexed filter bank having a digital by analog multiplier for weighting sampled input signals by digital constants is disclosed. The digital constants are stored and sequenced to the multiplier by a programmable read only memory.

Abstract: A four quadrant analog by digital multiplier includes an amplifier gain network in which the digital sign bit controls the polarity of the gain of an amplifier to determine the product of the digital sign and the analog value, and in which the digital magnitude bits control a multiple of resistor steps of a resistance network to determine the product of the digital magnitude and analog value as previously multiplied by the digital sign bit in the amplifier gain network.

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.