CS259718B1 - High-frequency tunable RC oscillator - Google Patents

Abstract

The connection concerns the field of tunable low-frequency oscillators. The subject is the solution of the technical problem of implementing a tunable oscillator for very low frequencies. The tunable RC oscillators used so far have a relatively long amplitude stabilization time relative to the length of the period of the generated signal and are therefore not applicable for frequencies lower than 1 Hz. Sawtooth generators with a shaping circuit are used for these frequencies. However, these generators have difficulty achieving a harmonic distortion value lower than one percent. The essence of the solution to this problem lies in the use of a tunable active RC filter and a nonlinear non-inertial element, which are connected in a loop so that the amplitude and phase oscillation conditions are met. The amplitude of the oscillation voltage is determined by the nonlinear properties of the non-inertial element, the oscillation frequency is given by the resonant frequency of the active RC filter, and the harmonic distortion by its selectivity. The connection can be used not only for generating very low frequencies, but also for higher frequencies, where we need a minimum amplitude stabilization time when changing the frequency.

Description

The invention relates to a tunable RC oscillator with fast amplitude stabilization suitable for very low frequencies.

Continuously tunable RC oscillators are still realized by combining a selective RC cell and a linear controlled amplifier. However, this control used to stabilize the amplitude must be considerably slower than the period of the generated frequency. Therefore, the use of normal RC generators for frequencies below 1 Hz is very problematic. Therefore, the principle of a saw generator with a forming circuit is used for very low frequencies. However, it is difficult to achieve harmonic distortion below one percent.

The above-mentioned drawbacks are solved by a new type of RC oscillator, which is based on a circuit formed by combining a tunable active RC filter and a non-linear non-inertial loop stabilizing member, with the non-inertial member providing positive feedback.

The main advantage of this oscillator lies in the minimum rise time and stabilization of oscillations even at low frequencies and in very low harmonic distortion.

The attached figure shows the group connection of the RC tunable oscillator, the oscillator output signal being taken from the RC tunable active filter output.

Tunable RC oscillator with fast amplitude stabilization consists of RC 2 tunable active filter with sufficient selectivity and non-linear non-inertia circuit

1.

The principle of the oscillator function is to introduce positive feedback for the active RC 2 filter through the non-linear non-inertia circuit 1 so that the amplitude and phase conditions of the oscillations are met. The transfer of the first harmonic through the non-linear non-inertia circuit 1 is dependent on its amplitude, so that with its increase the transfer decreases. Thus, the amplitude condition for a given signal size is satisfied and the oscillation voltage is stabilized. Oscillation frequency and harmonic distortion are given by the selectivity of the RC 2 tuned filter.

Claims (1)

A tunable RC oscillator for very low frequencies, characterized in that the tunable active filter RC (2) output is connected to the input of the nonlinear inertia circuit (1) and the non-linear inertia circuit output (1j) is connected to the tunable active filter RC (2) input. the oscillator output terminal is connected to the RC tunable active filter output (2).