Resonators refer to electronic components that generate resonant frequencies. Commonly used are quartz crystal resonators and ceramic resonators. The function of generating frequency has the characteristics of stability and good anti-interference performance, and is widely used in various electronic products. The frequency accuracy of quartz crystal resonators is higher than that of ceramic resonators, but the cost is also higher than that of ceramic resonators. The resonator mainly plays the role of frequency control, and all electronic products involve frequency transmission and reception require a resonator. The type of resonator can be divided into two types: in-line and patch type according to the shape.
The most basic resonant device is a dielectric resonator. To understand the working principle of dielectric resonators, we must first understand metal waveguides and resonant cavities.
The ways to transmit electromagnetic energy or electromagnetic signals can be divided into two categories, one is the propagation of electromagnetic waves in space or the atmosphere, and the other is the propagation of electromagnetic waves along the waveguide system.
The first electromagnetic waveguide wave system used by mankind is a two-wire transmission line. The two-wire transmission line is mainly used in low frequency occasions. When the use frequency gradually increases, the transmission loss and radiation loss of the two-wire transmission line increase sharply. In order to overcome the radiation loss, A coaxial line structure is adopted.
However, the mode used in the coaxial line is still the TEM mode, and there must be two conductors inside and outside. When the frequency is higher, the loss of the inner conductor becomes very serious. In the microwave frequency band, that is, the decimeter wave band and the centimeter wave band, people have found that it is feasible and convenient to use a hollow metal tube to transmit electromagnetic waves. It is impossible to propagate TEM mode in an empty tube, so TE mode or TM mode is used, which is a metal waveguide or waveguide.
In the short millimeter wave band and the sub-micro millimeter wave band, the cross-sectional area size of the metal waveguide is too small to be easy to process, so dielectric waveguides are used as the transmission system. The use of optical fibers and optical waveguides in the optical waveband is also a dielectric waveguide. Optical fiber referred to as optical fiber has become the main means of transmitting electromagnetic signals.
In order to approximately realize the boundary conditions of the short-circuit surface, a boundary surface composed of a high-conductivity conductor, that is, a metal, can be used to form a metal waveguide or waveguide. The metal waveguide may be composed of one waveguide or multiple waveguides.
Wave impedance of metal waveguide
The metal wall is composed of good conductors rather than ideal conductors, so there must be power loss when electromagnetic waves propagate in the waveguide, which will cause the attenuation of the electromagnetic waves along the propagation direction.
Metal waveguides and metal resonators are widely used in decimeter waves, centimeter waves, and longer millimeter wave bands.
Oscillator is the process of converting DC electric energy into AC electric energy, which is used to generate an AC signal of a certain frequency and is an active device. A resonator is a circuit that resonates a signal of a certain frequency. It is mainly used to filter out a certain frequency. It is a passive device. The crystal resonator is a passive device and does not require a power supply. The crystal oscillator is an active device and requires a power source, and the most important component in the circuit of the crystal oscillator is the crystal resonator. Add the crystal resonator to the external oscillating circuit, amplifying circuit, filter circuit, etc. to form the crystal oscillator.
In the past, the resonator and the oscillator were often confused. The crystal oscillator was an active device and required a power supply, and the most important component in the circuit of the crystal oscillator was the crystal resonator. Add the crystal resonator to the external oscillating circuit, amplifying circuit, filter circuit, etc. to form the crystal oscillator.