Local oscillator

A local oscillator or the local oscillator ( LO short ) is the name given to an oscillator which generates an auxiliary frequency. With his help, the transmit or receive frequency is changed with a mixer, it creates the intermediate frequency, or IF for short IF English Intermediate frequency.


Be used, among other local oscillators in communications technology and laser spectroscopy. In laser spectroscopic measurements are used laser beams, ie electromagnetic waves, as local oscillators.

The main application is the heterodyne receiver, wherein the radio frequency to a lower, constant ( and easier to process ), intermediate frequency (IF ) is implemented. The required frequency of the LO can be easily calculated:

The LO frequency will usually with the aid of quartz oscillators or VCOs ( Voltage Controlled Oscillator English, which are stabilized by a phase -locked loop (PLL) ) is generated. In simple devices, it is also unstable oscillators such as the three-point circuit.


Intermediate frequency 90 MHz, desired transmission frequency 1.8GHz


  • Communications Engineering
  • Electrical oscillator