Integrated VCO Design for MICS Transceivers

The 402-405 MHz MICS (medical implant communication service) band has recently been allocated by the US Federal Communication Commissions (FCC) with the potential to replace the low frequency inductive coupling techniques in implantable devices. This paper investigates the designs of VCO (voltage controlled oscillator) architectures that will be essential building blocks of such wireless implantable devices. Three different integrated quadrature VCOs that meet the requirements of the MICS standard are designed in 0.18 mum TSMC CMOS process to propose an optimum choice. The fabricated VCO´s are a four stage differential ring VCO, an LC tank VCO directly loaded with a poly-phase filter and an 800 MHz LC tank VCO with a high frequency master-slave divider. All three architectures target a VCO gain of K_VCO = 15 MHz/V with 3 calibration control and 2 FSK (frequency-shift keying) control signals and are designed for 1.5 V supply voltage