Radio frequency oscillators

A radio frequency oscillator is simply a signal generator that generates a sinusoidal or non-sinusoidal signal at a specific frequency. RF oscillators are the fundamental component of many electrical and electronic circuits.

Sustained oscillations are the main function of an oscillator. These components are also referred to as amplifiers with positive feedback. Or, to be more precise, a feedback amplifier with an open-loop gain greater than or equal to 1.

In principle, oscillators are ‘energy converters’. They convert DC energy into an AC signal. This signal can have frequencies ranging from a few Hz up to the GHz range.

Oscillators generate a periodic RF signal with a defined frequency and power. In RF measurement technology, they are primarily used as signal, reference or clock sources. To this end, the oscillators are usually synchronised to a stable, lower-frequency quartz oscillator

• Local oscillators (LO) for Mixers: The oscillator supplies the LO signal, which is used to down-convert an RF signal to a lower intermediate frequency or to up-convert it to a higher frequency.

• Signal generation: In signal generators and RF sources, oscillators generate the test signal for amplifiers, filters, antennas or receivers.

• Network and spectrum analysis: Oscillators are used internally for signal generation, frequency conversion and evaluation.

In many RF measurement systems, the oscillator provides the frequency reference (usually implemented as a quartz oscillator of the XO, TCXO or OCXO type) or the required carrier signal. Its signal quality often limits the achievable measurement accuracy.