A 4.3 GHz BiCMOS VCO with multiple 360° variable phase outputs using the vector sum method

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.

BiCMOS Colpitts oscillator for vector-sum interpolators

“…This alteration of the phase could be achieved using the vector-sum method (Opperman and Sinha, 2012), which is described in detail in Section 2. The section also describes the system configuration followed to implement the vector-sum method.…”

“…A local local oscillator (LO)-path shifting architecture for a phased array system generates phase shifted LO signals by locally varying the output phase of a single-phase voltage controlled oscillator (VCO) before feeding to the mixers (Valdes-Garcia et al , 2010). This alteration of the phase could be achieved using the vector-sum method (Opperman and Sinha, 2012), which is described in detail in Section 2. The section also describes the system configuration followed to implement the vector-sum method.…”