Abstract: A remote level measurement system for use in a multi-terminal communications system wherein a plurality of remote terminals are connected to a master terminal by a distribution network for bi-directional transmission of signals. The remote terminals are adapted to receive and transmit signals on the network. work. The master terminal is adapted to transmit an interrogation signal to a selected remote terminal and wait for a period of time sufficient for the interrogation signal to be transmitted to, and detected by, a selected remote terminal and a reply signal to be sent back to the master terminal by the remote terminal. At the expiration of that time the master terminal samples and measures the analog level of the reply signal.

Abstract: A method and system for reconstruction of chroma component segments in a line sequential chroma format television system. Filtering of a received line sequential chroma signal is employed to reconstruct missing chroma components and to attenuate phantom frequency components greater than one half the spatial sampling rate. Digital and analog filters are disclosed for implementation of such post filtering. The luminance component of the line sequential signal is delayed at the transmitter to synchronize the reconstructed chroma segment with its corresponding luminance segment with the use of minimal hardware at the receiver. Horizontal offset chroma sampling is used along with such post filtering to decrease transmission bandwidth requirements without sacrificing horizontal resolution at the receiver.

Abstract: A method and apparatus for measuring characteristics of a component color video signal. In one embodiment the luminance component of a color video signal is applied to the vertical input of a cathode ray tube display device and a chrominance component is applied to the horizontal input. The resultant dots and transitions therebetween produced by the display trace provide an indication of component bandwidth, amplitude and relative time between components. All components can be compared simultaneously by alternately applying one chrominance component with the luminance component, and the other chrominance component with an inverted luminance component. In another embodiment one chrominance component is applied to the vertical input and the other is applied to the horizontal input. Delay circuits are provided for use with a time-division multiplexed video signal to compare time multiplexed components simultaneously. A graticule is provided for relating the display trace to a standard display.

Abstract: A method and circuit for reducing the effect of variations in resistances within a multiplying digital-to-analog converter. A first resistor is connected at one end to the feedback resistor of the MDAC, the other end providing a compensated circuit input. A second resistor is connected from the MDAC input to the feedback resistor. The MDAC output to which the feedback resistor is internally connected is connected to the MDAC reference connection, the other output providing a compensated circuit output. The first and second resistors are chosen such that the product of their resistances is equal to the product of the feedback resistance times the MDAC input resistance.

Abstract: A low-distortion transformer-coupled circuit. An amplifier is constructed to have a negative output impedance equal to the resistance of the primary winding of a coupling transformer to which the amplifier is connected thereby cancelling the distortion component produced by the transformer distortion current flowing through the primary winding resistance. The input to the amplifier is thus coupled to the secondary winding of the transformer. A low-frequency feedback circuit is provided between the amplifier output and a non-inverting input thereof. Means is provided for adjusting the negative output impedance of the amplifier to match circuit parameters. Alternatively, the coupling transformer employs two matched primary windings and one secondary winding, and the amplifier is constructed to provide a signal to each primary winding.

Abstract: A 50% point of amplitude and phase detector. A differential amplifier produces non-inverted and inverted signals representative of a periodic input signal. Respective sample and hold circuits sample the levels of the non-inverted and inverted signals at predetermined points and the difference is input to the differential amplifier to equalize the position of those signals. The crossover of the non-inverted and inverted signals is detected by a gated differential amplifier whose output controls an oscillator from which the gating signal is derived to lock the phase of the oscillator output with the phase of the periodic signal.

Abstract: A dual rank sample and hold circuit and method is particularly applicable to deglitching the output of a digital-to-analog converter. One signal path is provided for coupling an input signal to the output of the sample and hold circuit to track the input signal during sampling. A second signal path is provided for coupling the input signal to a storage capacitor for charging or discharging the capacitor to the level of the input signal. In one embodiment the output is coupled simultaneously via the first signal path to the input signal and through a resistor to the storage capacitor, during a sampling phase, the capacitor being coupled to the input signal, and thereafter only to the capacitor during a hold phase, the capacitor being decoupled from the input signal.

Abstract: A circuit configuration is provided for reducing noise sidebands in the output of an oscillator due to modulation of the oscillation signal by characteristic noise produced by the amplifying element. A gallium arsenide field-effect transistor that produces characteristic noise is operated as a linear amplifier. Positive feedback to the input of the amplifier is provided by a resonator. The amplitude of the oscillation signal is limited by a distinct limiting circuit in the feedback loop, the input to which is isolated from the amplifier by a high pass filter, thereby divorcing the non-linear limiting function of the oscillator from the amplifying function where noise is generated.

Abstract: A dielectric resonator frequency selective network. A frequency selective network for microwave circuits is provided whereby a dielectric resonator is coupled to associated circuitry by input and output coupling loops formed in a single circuit board. The two loops are closely spaced, but partially overlapping at a position such that they are substantially decoupled from one another. A dielectric resonator is placed adjacent one of the loops so as to couple one loop to the other through the resonator and to cause the resonator to operate in its dominant mode. The circuit board is constructed by forming conductors separated by insulating material on a ceramic substrate.

Abstract: A method and circuit for quickly adjusting the frequency of a phase lock loop controlled oscillator to match a reference frequency signal by starting the reference frequency signal at essentially zero initial phase coincident with a zero crossing of the oscillator output. The reference frequency signal is provided by dividing a higher source frequency signal a predetermined amount. Upon receipt of an initialization signal the divider and the phase lock loop are inhibited. Upon the occurrance of a zero crossing the divider and loop are enabled so that the reference signal starts at zero phase within a predetermined period following the zero crossing, and the loop thereafter adjusts the oscillator frequency.

Abstract: A state variable oscillator with leveler circuit and with a feedforward circuit for improving the oscillator's rejection of leveler-induced distortion. The feedforward circuit combines a signal representative of a leveler-distorted feedback signal with the main oscillator output to reduce the amount of harmonic distortion, below a certain order, appearing in the output.

Abstract: An oscillator having a circuit for fine tuning the frequency thereof while minimizing any effect on the output amplitude thereof. A state variable oscillator employs an inverter amplifier having a negative feedback resistor R.sub.f, a first integrator, and a second integrator. 180.degree. feedback from the second integrator is fed back through resistors R.sub.i and R.sub.v to an inverting input of the inverter amplifier. 90.degree. feedback from the first integrator is fed back partially through resistors R.sub.n and R.sub.v and partially through resistor R.sub.m to the inverting input, and also through resistor R.sub.c to the non-inverting input. A field effect transistor provides a common return to the non-inverting input to control oscillator amplitude. If R.sub.i R.sub.m =R.sub.n R.sub.f then R.sub.v may be adjusted to vary the frequency of the oscillator output signal without affecting its amplitude.

Abstract: A circuit for use in association with a sample and hold circuit for preventing a sampled signal voltage from changing with time. The storage capacitor port at the sample and hold circuit is connected through a resistor to a variable voltage divider so that by adjusting the tap of the divider the current through the resistor can be adjusted to match the bias current generated at the capacitor port by the sample and hold circuit. A temperature sensitive device is included in the voltage divider for varying tap voltage and, hence, the matching current with ambient temperature to compensate for corresponding changes in bias current. The voltage divider is connected between the sample and hold output and a common return path to ensure that the voltage at the tap is a function of the sampled voltage and the temperature only.