A resonator is an electronic component or circuit that has a specific frequency response characteristic. It exhibits a high response at a specific frequency such that the input signal is boosted at that frequency and has a lower response at other frequencies.
Ⅰ. The difference between quartz crystal resonators and ceramic resonators
Commonly used resonators are divided into 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. Quartz crystal resonators have higher frequency accuracy than ceramic resonators, but also cost more than ceramic resonators.
Resonators mainly play the role of frequency control, and all electronic products require resonators for frequency transmission and reception.
Resonators are piezoelectric ceramic devices that oscillate at specific frequencies. The materials used to make such devices excite resonant properties during the production process. Since this resonant characteristic is within manufacturing tolerances and its figure of merit is much lower than that of quartz, ceramic resonators do not provide the same frequency stability as crystal resonators. This quality factor, also known as "Q", refers to the ratio of the energy stored in the resonator to the energy dissipated, and is also defined as the ratio of the reactance to the series resistance of the system at the resonant frequency.
Usually ceramic resonators are used in occasions where the cost is low and the performance is not required. Compared to crystals, ceramic resonators cost half as much and are smaller in size. But relative to the crystal resonator, its disadvantage is the lack of frequency and temperature stability. A crystal resonator is essentially similar to a ceramic oscillator, except that the resonant unit it uses is a quartz slice. Quartz has a naturally high quality factor "Q", which allows crystal resonators to maintain high accuracy and frequency stability over the entire operating temperature and voltage range.
1. The difference in material:
Quartz crystal resonators use the resonance characteristics of quartz crystals to generate stable oscillation signals. A quartz crystal exhibits resonance at a specific frequency, so it can be used as a frequency-stabilized reference oscillator.
Ceramic resonators are resonators made of ceramic materials. Unlike quartz crystal resonators, the resonant frequency of a ceramic resonator is usually determined by its material and structural design.
2. Differences in application:
Quartz crystal resonators are often used in occasions that require precise and stable frequencies, such as computers, communication equipment, precision instruments, etc.
Ceramic resonators are usually used in some low-cost and widely used occasions, such as wireless communication equipment, remote controls, smart cards, etc.
3. The difference in frequency stability:
Quartz crystal resonators have very high frequency stability and precision. Its frequency change is relatively less affected by factors such as temperature and supply voltage, so it is widely used in applications that require high stability, such as oscillators, clock sources, timers, etc.
Ceramic resonators have less frequency stability than quartz crystal resonators. Under the influence of temperature changes and supply voltage fluctuations, its frequency may have large changes.
Ⅱ. Working principle of resonator
The working principle of a resonator is based on the resonance phenomenon, that is, when the natural frequency of a system matches the external excitation frequency, the system will resonate. In a resonator, the natural frequency is determined by the resonator's circuit components (such as inductors, capacitors, crystals, etc.).
When a resonator is working, it needs an appropriate circuit to support its resonant characteristics. When the frequency of the external electrical signal is the same as the natural frequency of the resonator, a resonance phenomenon will occur, causing the electromagnetic wave energy inside the resonator to continuously accumulate, and finally achieve the effect of resonance amplification.
A resonator can change its resonance characteristics by adjusting the parameters of circuit components, such as changing capacitance or inductance. In addition, the quality factor of a resonator determines its resonant bandwidth and frequency accuracy, so it is also one of the important factors to be considered in resonator design.
How common resonator types work:
1. Ceramic resonator
Ceramic resonators are made of ceramic materials and have a specific resonant frequency and resonant bandwidth. Ceramic resonators are often used in wireless communication and radio frequency applications, such as mobile phones, wireless routers and other equipment.
2. LC resonator
An LC resonator consists of an inductor and a capacitor to form a resonant circuit. In a series resonator, the inductor and capacitor are connected in series, while in a parallel resonator, they are connected in parallel. The resonant frequency of a resonant circuit can be calculated by the following formula:
Resonant frequency = 1 / (2 * π * √(L * C))
When the external excitation frequency is equal to the resonant frequency, the resonant circuit will exhibit high impedance and form a resonant circuit.
3. Resonant cavity
Resonant cavities are resonators used in microwave and optical applications that form a standing wave field at a specific frequency. Resonators play an important role in microwave communications, laser systems and other fields.
4. Crystal resonator
Crystal resonators use the resonant properties of crystal materials to generate stable resonant frequencies. Crystal resonators are usually made of quartz crystals. In crystals, due to the special properties of the lattice structure, crystals can exhibit resonance characteristics at specific frequencies. Crystal resonators have high stability and precision and are often used in precision applications such as oscillators and clock sources.
Ⅲ. Function of resonator
1. A resonator can be used as a frequency selector, selecting a signal at a specific frequency and boosting the signal at that frequency. In wireless communication systems, resonators are used to select specific communication frequencies.
2. Resonators can be used in the design of frequency synthesizers to synthesize multiple frequencies into a composite frequency signal.
3. Resonators can be used in the design of frequency tuners in radio receivers to adjust the receiving frequency to receive specific signals.
4. As the core component of the oscillator, the resonator is used to generate a stable oscillation signal. Oscillators are fundamental components in many electronic devices and systems, providing stable frequency signals for applications such as timing control, clock sources, and communications.
5. The resonator can be used as a reference frequency for other systems to synchronize or calibrate other oscillators or clock sources.
6. A resonator has a high impedance at a specific frequency, so it can be used as a filter for filtering out signals within a specific frequency range.
7. The resonator can be used as an antenna, which is a device that couples electromagnetic waves into space, and the antenna itself has resonance characteristics. The use of resonators can improve the efficiency of antennas and enhance signal reception and transmission capabilities.
Ⅳ. Quartz crystal resonator
A quartz crystal resonator is an electronic component that uses the resonance characteristics of a quartz crystal to generate a stable oscillating signal. Quartz crystal resonators are mainly composed of quartz wafers, bases, shells, silver glue, silver and other components. It is an electronic device that uses the piezoelectric effect of quartz crystal (also known as crystal) to generate high-precision oscillation frequency, and is a passive device.
1. History of Quartz Crystal Resonators
The piezoelectric effect was discovered in 1880 by Jacques Curie and Pierre Curie. Paul Langevin first discussed the use of quartz resonators in sonar during World War I. The first crystal-controlled electronic oscillator was made using Rochelle salt in 1917, and was patented by Alexander M. Nicholson of Bell Telephone Laboratories in 1918, although Walter Guyton, who applied for the patent at the same time Cady has had his share of controversy. Cady made the first quartz crystal oscillator in 1921. Contributed to other early innovations in the quartz crystal oscillator were G. W. Pierce and Louis Essen.
2. Working principle
Quartz crystal resonators usually consist of a single piece of quartz crystal sandwiched between metal electrodes. When a voltage or electric field is applied to the crystal, the crystal starts to vibrate, creating a resonant frequency. Because the resonant frequency of the quartz crystal is very stable, the quartz crystal resonator can be used as a high-precision oscillator.
The working principle of the quartz crystal resonator is based on the resonance phenomenon of the quartz crystal. Quartz crystal has a special lattice structure, when a voltage or electric field acts on the quartz crystal, it will cause mechanical vibration in the crystal. This vibration causes the crystal to exhibit resonant properties at specific frequencies.
3. Temperature effect
The frequency characteristics of a quartz crystal depend on the shape or how it is cut. Tuning-fork crystals are usually cut into a parabola whose temperature characteristic is centered at 25°C. This means that a tuning-fork crystal oscillator resonates close to its target frequency at room temperature and decreases as the temperature increases or decreases. The temperature coefficient of a common 32.768 kHz tuning fork crystal with a parabolic frequency-temperature curve is negative 0.04 ppm/°C².
4. Resonant mode
Quartz crystal provides two resonance modes, series resonance composed of C1 and L1, and parallel resonance composed of C0, C1 and L1.
For general MHz-level quartz crystals, the series resonance frequency is generally several KHz lower than the parallel resonance frequency. Quartz crystals with a frequency below 30 MHz usually operate at a frequency between the series resonant frequency and the parallel resonant frequency. At this time, the quartz crystal presents inductive impedance. Because the capacitance on the external circuit will lower the oscillation frequency of the circuit.
Quartz crystals with a frequency above 30 MHz (to 200 MHz) usually work in series resonance mode, and the impedance is at the lowest point during operation, which is equivalent to Rs. Such crystals are usually marked with series resistance (< 100 Ω) rather than parallel load capacitance. In order to achieve high oscillation frequencies, a quartz crystal oscillates at one of its harmonic frequencies, which is an integer multiple of the fundamental frequency. Because the even-numbered harmonics will cause the electric fields in the crystal to cancel each other, only odd-numbered harmonics can be used, such as 3 times, 5 times, and 7 times overtone crystals.
5. The electronic devices of quartz resonant crystals can be divided into two categories: quartz crystal oscillators and quartz crystals.
Quartz crystal oscillator: refers to a module that contains a quartz crystal and an oscillating circuit. It needs a power supply and can directly generate an oscillating signal output. Because it contains active (active) electronic devices, the entire module is also an active device, and it is also called an active crystal oscillator in mainland China. Quartz crystal resonators are usually four-pin electronic devices, two of which are power supplies, one is for oscillation signal output, and the other is for empty pins or control.
Quartz crystal: It is a quartz wafer plus an electrode and a shell package. Also called quartz oscillator or quartz crystal resonator. This is a pure quartz crystal passive device, which does not contain active devices and needs to be matched with an external circuit to generate oscillation. This is a passive (passive) device, also known as a passive crystal oscillator. Quartz crystals are usually two-legged electronic devices.
Ⅴ. Optical Ring Resonator
An optical ring resonator is an optical device that uses the propagation and interference phenomena of light in a ring waveguide to achieve resonance.
The optical ring resonator is composed of at least one waveguide with closed optical path and the input and output ends of light (such as waveguide). The concept of an optical ring resonator is similar to that of a whispering gallery, except that light is used and the conditions of constructive interference and total internal reflection are respected. When the light that meets the resonance condition enters from the waveguide at the input end, and passes through the ring waveguide, the light intensity gradually increases due to constructive interference in the ring waveguide, and finally outputs from the waveguide at the output end.
The basic structure of an optical ring resonator is a ring waveguide composed of an optical waveguide. When light passes through the ring waveguide, due to light interference, some specific wavelengths of light are amplified in the ring waveguide, while other wavelengths of light are weakened. When the light of a specific wavelength matches the circumference and propagation loss of the ring waveguide, a resonance phenomenon occurs so that the optical signal of that wavelength is enhanced in the ring waveguide.
1. The principles of optical ring resonators include: constructive interference, total internal reflection and optical coupling.
Interference: Interference is the superposition of two or more waves to form a composite wave of higher or lower amplitude. In constructive interference, two waves of the same phase interfere with each other to produce a composite wave whose amplitude is the sum of the two waves. As light travels around the ring waveguide, it interferes with other light rays remaining in the ring. Therefore, assuming that there are no losses caused by absorption, evanescent waves, imperfect coupling, etc. in the system, and the system meets the resonance conditions, the output light intensity of the optical resonator will be the same as the input light intensity.
Total Internal Reflection: Due to total internal reflection, light rays traveling through an optical ring resonator stay inside the waveguide. When light hits the boundary of the propagation medium, if the incident angle is greater than the critical angle, and the material on the other side of the boundary has a lower refractive index, total internal reflection will occur, and no light will pass through the boundary. For an optical ring resonator to work well, it is necessary to satisfy the condition of total reflection, where light should be kept as far as possible from leaving the waveguide.
Optical coupling: due to the evanescent wave effect, when the light passes through the upper waveguide, part of the light will be coupled into the ring waveguide. There are three factors that affect coupling: the distance between waveguides, the length over which waveguides can couple, and the refractive index. Reducing the distance between waveguides and increasing the coupling length between waveguides can increase the coupling efficiency. The refractive index of the waveguide itself and the material between the waveguides also affect the coupling efficiency. One of the coupling characteristics is critical coupling. When critical coupling occurs, there will be no light intensity after passing through the coupling region, and all light will be stored in the ring waveguide and dissipated in the ring.
2. Advantages
Optical ring resonators can selectively amplify light of a specific wavelength, filter light of other wavelengths, and achieve wavelength-selective transmission and processing. Optical ring resonators have a high quality factor, meaning they are able to keep light at the resonant frequency for a longer period of time, thereby enhancing the effect of the resonance phenomenon.
3. Double loop resonator
A double ring resonator uses two ring waveguides, which can be connected in series (as shown on the right) or in parallel. When connected in series, the output direction of the double loop resonator is the same as the input. When the input light meets the resonance conditions of the first ring, the light couples into the first ring and propagates along the ring. If the light meets the resonance conditions of the second ring, the light will be coupled from the first ring to the second ring. In the same way, light is eventually coupled to the output waveguide.
In order for the target light to pass through the double ring resonator, the following conditions need to be met:
Where m1 and m2 are integers.
4. Application
Since optical resonators can filter specific wavelengths of light, high-order optical filters can be manufactured by using multiple optical resonators. Optical resonators have the advantages of "small size, low loss, and can be integrated into existing optical systems". In addition, since the resonant wavelength can be changed by changing the radius of the ring, the entire resonator can be regarded as a tunable system, and this property can be used to make some mechanical sensors. If the resonator is subjected to stress and changes in size, the resonant wavelength of the light will also change accordingly. This effect can be used to monitor for dimensional changes in fibers or waveguides.
Toroidal, cylindrical and spherical optical resonators can be used in the field of biosensing. How to increase the performance of biosensors is one of the research focuses. The advantage of using an optical resonator as a biosensor is that only a small amount of sample can be measured, and the Raman and fluorescence signals caused by solvents and impurities can be greatly reduced. Resonators are also used in the chemical identification of gases to measure absorption spectra.
标签：Resonators
