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A comparison of approaches to carrier generation for zigbee transceivers
Date Issued
30-03-2009
Author(s)
Abstract
Two methods for generating in phase and quadrature local oscillator signals at 2.4GHz for Zigbee transceivers are investigated. In one method, the output of a 4.8GHz LC VCO is divided by two to obtain I and Q phases at 2.4GHz. In another method, outputs of a four stage differential ring VCO at 1.2GHz are appropriately multiplied to obtain I and Q phases at 2.4GHz. These circuits are designed and laid out in a 0.18 μm CMOS process and they operate from a 1.8V power supply. The former architecture occupies 0.052mm2, consumes 7.56mW, and has a phase noise of -117 dBc/Hz at 3.5MHz. The latter occupies 0.021mm2, consumes 9mW, and has a phase noise of -97 dBc/Hz at 3.5MHz. Temperature variations of the ring oscillator are minimized using a combination of constant current and constant gm biasing. © 2009 IEEE.