Abstract: A laser displacement measurement system including a radiation source for transmitting radiation to a target, an R.F. transmitter oscillator for modulating the amplitude of the radiation at a first frequency, a detector for sensing the radiation reflected from the target, an R.F. local oscillator for providing an R.F. signal at a second frequency, a first mixer circuit, responsive to the oscillators for providing a local I.F. signal which is the difference between the first and second frequencies, a second mixer circuit, responsive to the detector and the R.F. local oscillator, for providing a reflected I.F. signal which is the difference between the second frequency and the modulation frequency of the reflected radiation, and a phase detector, responsive to the local and reflected I.F. signals, for detecting a first phase difference between the signals representative of the distance of the target.

Abstract: A digital phase measuring system and method for measuring the phase difference between two signals including generating quadrature clock signals for a first reference signal, converting a second measured signal from analog to digital form by sampling the second measured signal using the quadrature clock signals to produce quadrature cartesian samples of the measured signal, and converting the quadrature cartesian samples to polar coordinates to define the polar phase coordinate representative of the phase difference between the two signals.

Abstract: A high speed laser driver includes a differential pair of bipolar transistors sharing a common emitter resistor as in the prior art. However, an improvement thereover resides in the use of Schottky barrier diodes, one of which couples the emitter of one transistor to the common emitter resistor and the other of which couples the emitter of the other transistor to the common emitter resistor. Furthermore, separate resistors couple the emitters of both transistors to a voltage source so that the transistors are always conducting.

Abstract: A high speed laser driver includes a differential pair of bipolar transistors sharing a common emitter resistor as in the prior art. However, an improvement thereover resides in the use of Schottky barrier diodes, one of which couples the emitter of one transistor to the common emitter resistor and the other of which couples the emitter of the other transistor to the common emitter resistor. Furthermore, separate resistors couple the emitters of both transistors to a voltage source so that the transistors are always conducting.A high speed logic circuit includes a pair of input bipolar transistors, and a reference transistor, sharing a common emitter resistor as in the prior art. However, an important resides thereover in the use of Schottky barrier diodes that couple the emitters of the transistors to the common emitter resistor. Furthermore, separate resistors couple the emitters of the three transistors to a voltage source so that the transistors are always conducting.

Abstract: A predistortion circuit that cancels second order distortion of light emitting diodes enabling interference free transmission of multiple vestigial sideband television channels through a single optical fiber. This is achieved by preamplifying a signal with an amplifier that has opposite characteristics to the distortions of a light emitting diode.

Abstract: A low noise optical receiver utilizes a novel amplifier as the open loop gain element. The amplifier provides for lower noise performance over that of commercial receivers, thus allowing longer fiber optic communication links.

Abstract: A radio frequency receiver system adapted to monitor the international radio-telegraph distress frequency is disclosed. The system comprises a first receiver section coupled to a receiving antenna. Such receiver section includes an automatic gain control circuit having a relatively long time response characteristic for adjusting the sensitivity of the receiver section in accordance with the average level of received background noise, thereby to pass sudden radio frequency signals having levels above the average level of the received background noise and which are substantially unaffected by the automatic gain control circuit. The passed radio frequency signals are fed to a second receiver section. Such second receiver section includes an automatic gain control circuit which is responsive to the average level of the received background noise level in the absence of a sudden strong signal, and which is, in the presence of a sudden strong signal, responsive to the level of such sudden strong signal.