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RF Electronics Chapter 6: Oscillators Page 176 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. resonator used in the oscillator, and the way that the amplifier loads the resonator. The higher the Q of the resonator, the lower the phase noise and in general, the lower the frequency variation that can be obtained by tuning the resonator. The choice of the resonator and its Q is thus the primary factor affecting the oscillator properties [1]. Figure 6.4. Q values and volume of different resonators at 900 MHz. Colpitts Oscillator Design Procedure A 100 MHz oscillator is required, to operate from a 10V supply. The oscillator in this chapter can easily operate at > 100 MHz. Simply change Fo in the Global Definitions of the project file for figures 6.5 to 6.22, to select the desired operating frequency. The design procedure is illustrated by designing a Colpitts oscillator. Step 1: Select an Amplifier Type The active device used in an oscillator is very important, factors for consideration are; Output power, oscillating frequency, supply voltage and cost. The low frequency phase noise of the oscillator does depend on the flicker noise of the amplifier, so that the noise figure of the amplifier is important for low noise oscillators. When designing a circuit, it is important to ensure that the devices used will be available for a reasonable time. Infineon's [2] BFR193W is a High Linearity low noise transistor that is "active and preferred" for VHF and UHF applications. The transistor has a maximum Vceo of 12V and a collector current of 80 mA. The Spice model for that transistor is available from LibrariesX Libraries *AWR web site Parts By Type Nonlinear Infineon RF Bipolar Transistors High Linearity Si- and SiGe:C- Transistors up to 6 GHz BFR193W. That transistor has a typical noise figure of 1 dB @ Vce=8V, Ic = 10 mA and 900 MHz. The design procedures outlined in this chapter apply to any active device. The only requirements are that a Spice model is available to allow non-linear simulations to be carried out and that the device can operate at the voltage and current used in the simulations. Stripline Microstrip 10 100 1 000 100 000 10 000 100 1000 1 0.01 0.1 10 000 Volume in mL Unloaded Q Resonator unloaded Q at 900 MHz Coaxial (Er=92) Coaxial (Air) Suspended Stripline TE Mode Dielectric Extrapolated Superconducting Microstrip RF Electronics: Design and Simulation 176 www.cadence.com/go/awr

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