What is varactor tuned oscillator?
What is varactor tuned oscillator?
Varactor-tuned oscillators (VTO), on the other hand, feature high speed tuning, although their linearity is inferior to that of YIG-tuned oscillators. Therefore, improving the linearity of VTOs has been the subject of much research.
How varactor diode is used in tuning circuit?
A varactor diode is a simple variable capacitor that allows oscillator circuits and other circuits to be easily tuned by applying a voltage. When the reverse bias voltage is increased, the width of the depletion region also increases, which decreases the capacitance.
How does a VCO work?
A voltage-controlled oscillator (VCO) is an electronic oscillator whose oscillation frequency is controlled by a voltage input. Consequently, a VCO can be used for frequency modulation (FM) or phase modulation (PM) by applying a modulating signal to the control input.
Where are varactors used?
Varactor or varicap diodes are used mainly in radio frequency or RF circuits to provide voltage controlled variable capacitance. These electronic componenta can be used in a whole variety of ways where a capacitance level needs to be controlled by a voltage.
How does varactor diode work?
Definition: Varactor diode is the one which works on the principle of variation in capacitance by changing the width of the depletion region of P-N junction. The P-N Junction diode creates capacitor effect. The capacitance is controlled by applied voltage. It works on reverse biased mode.
How does a varactor work?
What is loop filter?
[′lüp ‚fil·tər] (electronics) A low-pass filter, which may be a simple RC filter or may include an amplifier, and which passes the original modulating frequencies but removes the carrier-frequency components and harmonics from a frequency-modulated signal in a locked-oscillator detector.
What is a digitally tuned VCO?
A digitally controlled oscillator or DCO is used in synthesizers, microcontrollers, and software-defined radios. The name is analogous with “voltage-controlled oscillator.” DCOs were designed to overcome the tuning stability limitations of early VCO designs.
Who invented varactor diode?
Erik Kollberg
The device was invented by Erik Kollberg together with Anders Rydberg in 1989 at Chalmers University of Technology.
What is the key feature of a varactor diode?
Important characteristics are capacitance when designated bias voltage is applied (ex. C3V where VR=3V), capacitance variation when applied voltage changes (capacitance ratio) and series resistance that affects Q index when used in oscillators or filters.
How is a varactor diode used in a tuning circuit?
A varactor diode is a simple variable capacitor that allows oscillator circuits and other circuits to be easily tuned by applying a voltage. These diodes have a similar structure as a p-n diode; the structure of a varactor diode is rather simple and illustrates its power as a component with nonlinear reactance.
How are the parameters of a tuning circuit determined?
These parameters can be easily determined from measurements of the capacitance versus applied reverse-bias voltage, as long as the built-in voltage is known. This is normally done using a log-log plot, which will be a linear function of log (1 + V/ɸ). An example is shown below for C0 = 1 pF.
What happens to the capacitance of a varicap diode?
The effect is cancelled out – as the RF voltage rises, the capacitance on one diode will increase and the other decrease. The back-to-back configuration also halves the capacitance of the single diode as the capacitances from the two diodes are placed in series with each other.
How does reverse bias voltage affect the capacitance?
When the reverse bias voltage is increased, the width of the depletion region also increases, which decreases the capacitance. The image below shows the schematic symbol and capacitance equation for a varactor diode. Schematic symbol for a varactor diode and capacitance equation.
