Apparatus for improving the signal to noise ratio in an electrical signal. A signal enhancement processor operating in real time and selecting signals based upon the similarity of the incoming signal to a locally generated reference and which does not require that signals be filterable in the frequency domain, that external reference signals be supplied, or that signal amplitude criteria be employed. A system for providing input signal attenuation or rejection as a function of the frequency or phase of the input signal, with attenuation at a maximum for an undesired signal and at a minimum for a desired signal.

Real-time cross-correlation signal processor

A method and apparatus wherein a single dual element galvanomagnetic sensor, herein exemplified by a single dual element magnetoresistive sensor ( 16 ′), is utilized to sense crankshaft position and rotational speed from the passage of single tooth edges ( 12 ′) of a target wheel ( 10 ′) by continuous adaptive matching of both MR output signals (V MR1′ , V MR2′ ) during sensor operation Over a slot ( 28 ′) or tooth ( 26 ′), both MR output signals should be equal, and if not, they are matched by adjusting the current of one of the current sources ( 30′, 32′ ) driving the MRs, performed over a slot or a tooth Due to higher magnetic sensitivity at smaller air gaps, matching by current adjustment over a tooth is preferred In a preferred embodiment of the present invention, one MR is driven by a constant current source ( 30′ ) while the other MR is driven by a voltage controlled current source ( 32′ ) The output voltages of the MRs approximate the tooth pattern of the target wheel; they are high over a tooth and low over a slot Hence, the signals over the teeth can be simply acquired by means of a peak detector ( 36 a, 36 b ), one for each MR The signals from the peak detectors are subtracted from each other in a comparator ( 36 c ), and then used as a control voltage (V C ) for a voltage controlled current source changing its preset nominal current to a value that minimizes the mismatch of MR signals If matching of MR signals over slots would be desired, valley detectors would be substituted for the peak detectors

Differential magnetic position sensor with adaptive matching for detecting angular position of a toothed target wheel

A receiver for receiving recurring first and second scanning signals. The peak of successive first and second scanning signals is digitally detected (16) and averaged (19, 20). The gain of an amplifier (6) of the receiver is controlled in response to the averraged peaks to anticipate the magnitude of the next scanning signal. As a result, recurring first and second scanning signals of significantly different magnitudes are received and processed by the receiver.

Microprocessor controlled AGC

A peak detector circuit (10) is disclosed wherein an input signal is full-wave rectified by a circuit (14) and the rectified signal is provided simultaneously to peak detect, hold and dump circuits (18), (20). Each of the peak detect, hold and dump circuits is discharged at the start of periodic intervals with a phase offset between the intervals for the two circuits. The peak signals are discharged at essentially the start of the interval followed by rapid charging of the peak signal to the peak amplitude of the rectified input signal. The later portions of each of the intervals of the peak signals produced by the peak detect, hold and dump circuits (18) and (20) are transmitted alternately through a multiplexer circuit (24). The resulting output signal is transmitted through a high impedance buffer amplifier (30) to an output terminal (32) of peak detector circuit (10). The timing of the operation of multiplexer (24) serves to remove the discharge and charge transitions of the peak signals from the peak detected output signal.

Fast updating peak detector circuit

An automatic attenuation circuit comprises a variable loss attenuation circuit that drives circuitry for detecting the level of the output signal of the variable loss attenuation circuit. The level detector drives a periodically reset integrator, which in turn feeds a signal to a comparator, also responsive to a reference. A control circuit responsive to the output signal of the comparator controls the attenuation factor of the variable loss attenuation circuit. The control circuit, which may be a microcomputer, is so programmed that the attenuation factor of the variable loss attenuation circuit is stepwisely increased until the level of the output signal of the variable loss attenuation circuit becomes equal to or below a predetermined level.

Automatic attenuation circuit

The sequential automatic gain control circuit is an improved AGC circuit that can be used in search and track radars which receive a series of pulse returns from each target. The sequential AGC is well suited for monopulse radars and moving target indication (MTI) processing where gain stability and gain match between channels are required. The maximum input signal levels are sensed by a pair of AGC circuits which alternately provide output levels for a predetermined time. The output signal levels are proportional to the maximum input signal received during the previous pulse return period.

W Briscoe

Papers

Sequential automatic gain control circuit