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Negative resistance radio frequency (RF) and microwave oscillators are widely used in modern wireless communication systems. In these circuits, the active device is imposed to work in the unstable region in order to present a negative resistance at its input or output port. This paper discusses the effect of the load impedance on the large signal b...
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Context 1
... Design System (ADS 2009) has been utilized in the simulation process for this oscillator. The SPICE Gummel-Poon large-signal model of the BFR91 transistor is defined from the RF transistor library of ADS. For an emitter current of 10 mA, the measured base-emitter voltage is 0.78 V, and the measured DC current gain of the transistor, hFE, is 70. Fig. 5 presents a common base (CB) voltage-divider bias circuit. This bias circuit is designed to hold the Q-point of the transistor against variations in device internal parameters, and is isolated from the RF circuit via two RF chokes, RFC1 and RFC2, while Cb is a bypass capacitor for resistors R1 and R2. ...
