Using the periodical surface′s character of band gap and impedance transition of electromagnetic crystal structure such as photonic band gap(PBG),frequency selection surface(FSS),high impedance surface(HIS) and so on,the varactor diode was put onto the approximate HIS′s surface to join each cell of metal on top layer to realize the electronic control for periodical structure.

In this method, the capacitance of the varactor diode is changed by voltage.

In this paper,the design principles and methods of the super-abrupt junction GaAs varactor diode has been discussed.

The Pre-condition for Variable Capacitance Diode Frequency Modulator Obtaining the Linear Frequency Modulation;

It is confirmed by electrical measurements of I-V,C-V,C-f,and deep level transient spectrum that this is a variable capacitance diode of linear slowly varied heterojunction.

Gives an analysis on the non linearity in frequency modulation when a varactor modulates directly in a FM ranging fuze,and shows its influence on the precision of ranging.

The transformation between digital signal and DC voltage was made with D/A converser and high voltage amplifier; varactors were used for tuning components; the bandpass filter was a combline microstrip line one, its dimension was presented.

The recent developments in varactor are reviewed, such as large capacitance rate, dual ion implantation, embedded in tuner, multi-varactor cell, super-miniaturization, low voltage and varieties of application.