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Maxim > Design Support > Technical Documents > Application Notes > Wireless and RF > APP 698
Keywords: vco, pll, rf, rfic, phase noise, voltage controlled oscillator, rf ics, integrated circuits, phase-
locked loop, radio frequency
APPLICATION NOTE 698
Silicon-Bipolar IC Facilitates VCO Design
Sep 02, 2002
Abstract: The frequency of a voltage-controlled oscillator (VCO) varies with the voltage applied to its
tuning port. Operating in a phase-locked loop (PLL), the VCO provides a stable local oscillator (LO) for
frequency conversion in superheterodyne receivers. VCOs are also used in transmit chains, where they
upconvert the baseband signal to a radio frequency (RF) suitable for transmission over the airwaves.
The frequency of a voltage-controlled oscillator (VCO) varies with
the voltage applied to its tuning port. Operating in a phase-locked
loop (PLL), the VCO provides a stable local oscillator (LO) for
frequency conversion in superheterodyne receivers. VCOs are also
used in transmit chains, where they upconvert the baseband signal
to a radio frequency (RF) suitable for transmission over the
airwaves (Figure 1).
Figure 1. VCOs appear as part of the PLLs in this typical superheterodyne receiver.
Design Considerations
The VCO designer must consider several important performance parameters:
Output level in dBm (dB relative to 1mW)
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