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Glossary of Specifications and Terms

The following definitions apply specifically to VCO'S unless otherwise stated

Phase Noise

In the frequency domain, an ideal carrier would appear as an infinitesimally thin line, The typical carrier however, will have skirts whose amplitudes generally follow 1 / f distribution with increasing video frequencies. These skirts are the envelope of side bands due to modulations of the carrier, and are both FM and AM in nature, random in both frequency and amplitude, and are caused by various phenomena relating to the physics of the particular oscillator, and are commonly referred to as "NOISE". We specify phase noise as single sideband power in relation to the fundamental RF output frequency, and measured at various offset frequencies from the carrier, normalized to a one hertz measuring bandwidth ( example -120dBc / Hz / 100KHz, offset ).

Harmonic Rejection

As specified in this catalog are the worst case amplitude of all harmonically related outputs or signals relative to the carrier (fundamental frequency) power. The measurement is normally expressed in terms of dBc below the carrier (dBc); also referred to as "Harmonic Suppression".


Spurious signals are any outputs in the spectrum of a source (VCO) that are neither part of the carrier, not its harmonic and they may be discreet or bands of frequencies. Modco VCO'S do not contain any spurious outputs.

Post Tuning Drift

This could be defined as the change in frequency occurring within a definite time frame beginning a particular time after an instantaneous specified change in address (tuning voltage). Generally helpful information to know for open loop fast tuning (EW) applications.

Pushing or Pushing Figure

This refers to the maximum change in frequency and or power that can be tolerated for a given change in the input voltage (Vcc). This would be expressed in terms of "MHz per volt" for frequency and "dB" for power.

Pulling or Pulling Figure

This refers to the maximum change in frequency and or power tolerable when a mismatch of specified magnitude at the output is rotated through all phases (360 deg).

Frequency Stability

This is a measure of how much the frequency of the VCO changes as a result of temperature shifts, and is expressed in terms of "MHz / deg c".

Input Capacitance

Normally refers to the maximum amount of capacitance located at the tuning voltage input terminal of a VCO.

Modulation Sensitivity

The ratio of frequency change for a VCO to a change in tuning voltage and is expressed in "MHz / volt".

3dB Modulation Bandwidth

The Frequency at which the Modulating Frequency Deviation decreases to 0.707 of its DC value.

Voltage Standing Wave Ratio (VSWR)

The ratio of the maximum to minimum voltage present on a transmission line, and normally due to load reflections from an unmatched VCO (source) and load impedance.