A digitally-tuned oscillator (DTO) includes a digital-to-analog converter (DAC) and an RC oscillator The RC oscillator includes an RC circuit for forming a time constant equal to the RC product However, this RC time constant is not used in the manner of a typical RC network to set the frequency of oscillation Instead, the RC oscillator disclosed herein includes a separate oscillator, such as a voltage-controlled oscillator (VCO), and uses the RC time constant to compare with the oscillator-generated period and to adjust the frequency of the overall RC oscillator circuit in accordance with the comparison The RC oscillator is self-calibrating

Digitally-tuned oscillator including a self-calibrating RC oscillator circuit

A controllable broad-band frequency generator comprising a voltage-controlled oscillator incorporated in a frequency controlled loop and an external controllable voltage source connected thereto, the control loop furthermore incorporating a digital crystal stable frequency discriminator and a combination device in which the direct voltage value derived from the voltage source is deducted from the output voltage provided by the frequency discriminator to obtain a direct control voltage for frequency controlling the voltage-controlled oscillator.

Wide frequency range voltage controlled oscillator with crystal controlled frequency stabilizing loop

The present invention relates to an automatic frequency control (AFC) system for controlling the frequency of an oscillator

Automatic frequency control system

An oscillation frequency control device which comprises a voltage control local oscillator; a generator for giving forth an output having a predetermined referential frequency; means for periodically generating a gate pulse whose time width is equal to an integral multiple of the period of an output signal from said generator; a gate circuit for permitting the passage of an output signal from the local oscillator only during the time width of said gate pulse, wherein, while the local oscillator continues oscillation at a desired frequency, the number k of waves running through the gate circuit is chosen to be equal to an integral multiple of the counting capacity or the scale type n of a counter; said n-scale counter counts signals which have traveled through the gate circuit in at least one cycle for each supply period of the gate pulse, starting with the prescribed count at which said counter is initially reset; a count obtained in the final cycle is changed into an analog signal; comparison is made between a voltage represented by said analog signal and the referential voltage corresponding to the prescribed count at which the counter is initially reset; a differential voltage resulting from the outcome of said comparison is fed back to the local oscillator as a control voltage, thereby causing said oscillator to carry out oscillation only at desired frequencies.

Oscillation frequency control device for a local oscillator

A pulse generator provides a continuous train of electrical pulses of variable frequency, duration and amplitude. The pulse generator includes an adjustable frequency astable oscillator coupled to a monostable pulse generator. An isolation circuit isolates the output of the monostable pulse generator from loading effects to minimize output waveform jitter. A power amplifier receives the isolated pulse signal from the monostable pulse generator and provides output pulses of sufficient energy to simultaneously power continuous and capacitive electrical loads with minimal effect on the pulse generator output pulse waveshape.

Repetitive pulse generator with wide pulse duration, amplitude, frequency and duty cycle characteristics

A variable frequency oscillator is digitally commanded to any one of a large number of frequencies by a system that involves closing a sample data frequency servomechanism loop around a voltage (or current) controlled oscillator. In the sample data frequency loop, a phase-locked subharmonic oscillator produces a sampled frequency at a fraction of the oscillator output. This sampled frequency is applied to a logic system that produces a frequency error signal by an arithmetic operation of subtraction and addition. This frequency error signal is then utilized to adjust the controllable oscillator.

David C Conner

Papers

Variable frequency control