Abstract:
A 4.3 GHz voltage controlled oscillator (VCO)
with multiple independently tunable phase outputs is presented.
The VCO is realized by coupling two LC oscillators
together in order to obtain quadrature signals and is tunable
between 4.12 and 4.74 GHz. The variable phase outputs
are achieved by varying the amplitudes of the in-phase and
quadrature signals independently and then combining these
signals together. By using multiple Gilbert cells as variable
gain amplifiers (VGAs), multiple tunable phase outputs are
achieved with the use of only one quadrature VCO. The
VGAs are controlled using a custom non-linear digital-toanalog
converter. The entire circuit is designed using a
3.3 V SiGe BiCMOS process. A maximum phase noise of
-108.17 dBc/Hz was measured over the entire tuning
range at a 1 MHz offset. The outputs of the VCO can be
used as local oscillators that achieve phase shifting during
radio frequency up or down conversion.
