How does a varactor work?
A varactor diode is designed to store electric charge not to conduct electric current. So varactor diode should always be operated in reverse bias. When a reverse bias voltage is applied, the electrons from n-region and holes from p-region moves away from the junction.
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.
What are the two methods of FM generation?
The following two methods generate WBFM wave.
- Direct method.
- Indirect method.
What is varactor modulator?
Varactor diode modulator is the direct method of FM generation wherein the carrier frequency is directly varied by the modulating signal. A varactor diode is a semiconductor diode whose junction capacitance varies linearly with applied voltage when the diode is reverse biased.
How does a varactor diode operate?
Operation of Varactor Diode The function of the varactor diode is to store charges, so it is always operated in reverse bias condition. When a forward bias voltage is applied, the electric current flows, as a result, the depletion region becomes negligible, which is undesirable.
What is a varactor diode give its circuit symbol and one application?
Varactor diode is one kind of semiconductor microwave solid-state device and the applications of this diode mainly involve in where variable capacitance is preferred which can be accomplished by controlling voltage. These diodes are also named as varicap diodes.
How does balance modulator work?
In electronic communications, a balanced modulator is a circuit that produces double-sideband suppressed-carrier (DSBSC) signals: It suppresses the radio frequency carrier thus leaving the sum and difference frequencies at the output.
What is reactance modulator?
The reactance modulator gets the modulating signal as input. It operates on the tank circuit of an LC master oscillator. The output of this oscillator is FM signal. It is passed through a buffer and amplitude limiter before it is applied to the Class C power amplifier.
Where is the varactor modulator used?
Varactor diode modulator is used for automatic frequency control and remote tuning. The drawback of varactor diode modulator is that since it uses a crystal, the peak frequency deviation is limited to relatively small values. Thus they are used mostly for low index applications such as two way mobile radio.