Inductor is an energy storage component, mostly used in power filter circuit, LC oscillation circuit, low frequency filter circuit, etc., its application frequency range rarely exceeds 50MHz. For inductors, its inductive reactance is proportional to the frequency. This can be illustrated by the formula: XL = 2πfL, where XL is the induced reactance (in Ω). For example: an ideal 10mH inductance, at 10kHz, the inductive reactance is 628Ω; At 100MHz, this increases to 6.2MΩ. Therefore, at 100MHz, this inductor can be considered an open circuit. At 100MHz, if a signal is allowed to pass through this inductor, the quality of this signal will be degraded.
    The material of ferrite bead is iron-magnesium or iron-nickel alloy, which has a high resistivity and permeability, and the capacitance between the coils in the inductor will be minimal at high frequency and high impedance. Magnetic beads are usually only suitable for high frequency circuits, because at low frequencies, they basically retain the complete characteristics of inductance including resistive and reactive components, and therefore cause small losses on the line. At high frequencies, it basically has only a reactive component (jωL), and the resistant component increases as the frequency increases. Like some RF circuits, PLL, oscillation circuits, including ultra-high frequency memory circuits (DDR,SDRAM,RAMBUS, etc.) need to add magnetic beads in the power input part. In fact, magnetic beads are high-frequency attenuators of radio-frequency energy. In fact, the magnetic bead can be regarded as a resistor in parallel with an inductor. At low frequencies, the resistance is "short-circuited" by the inductor, and the current flows to the inductor. At high frequencies, the high inductance of the inductor forces current to the resistor. In essence, a magnetic bead is a "dissipative device" that converts high-frequency energy into heat. Therefore, in terms of performance, it can only be interpreted as a resistor, not an inductor.

zero ohm resistance functions as follows:
    1, there is no function in the circuit, only on the PCB for debugging convenience or compatible design reasons.
    2, can be used as a jumper, if a certain line is not used, directly subsidize the resistance can be (does not affect the appearance).
    3, when the matching circuit parameters are uncertain, replace with 0ohm, when the actual debugging, determine the parameters, and then replace with specific numerical components.
    4, when you want to measure the power consumption of a certain part of the circuit, you can remove the 0ohm resistance and connect the ammeter, so that it is convenient to measure the power consumption.
    5, in the wiring, if the cloth can not be passed, you can also add a 0ohm resistance (feel should be directly inserted, should not be table paste (luther.gliethttp)).
    6, in the high-frequency signal, acting as an inductor or capacitor. (related to external circuit characteristics) inductance, mainly to solve EMC problems. (such as ground to ground, between power supply and IC Pin).
    7, single point grounding (refers to the protection grounding, working grounding, DC grounding on the equipment are separated from each other, each become an independent system).
    8, fuse action inductance

① Analog and digital ground single-point grounding
    As long as it is the ground, it must eventually be connected together and then enter the earth. If not connected together is "floating", there is a pressure difference, easy to accumulate charge, resulting in static electricity. The ground is the reference 0 potential, all voltages are derived from the reference ground, and the standard of the ground should be consistent, so all kinds of ground should be short-connected together. It was thought that the earth could absorb all electrical charges and remain stable, the ultimate ground test. Although some boards are not connected to the ground, the power plant is connected to the ground, and the power supply on the board will eventually return to the power plant to the ground. If a large area of analog and digital land is directly connected, it will cause mutual interference. Not short and inappropriate, the reasons above there are four ways to solve this problem:
    1. Connect with magnetic beads; The equivalent circuit of the magnetic bead is equivalent to a wave limiter with a resistance, which only has a significant suppression effect on the noise at a certain frequency, and the noise frequency needs to be estimated in advance when used in order to select the appropriate model. For situations where the frequency is uncertain or unpredictable, magnetic beads do not fit.
    2. Connect with capacitors; The capacitor partition is directly connected, which can easily cause floating ground.
    3, with inductance connection; The inductor has large volume, many stray parameters and is unstable.
    4, with 0 ohms resistance connection; The 0 ohm resistance is equivalent to a very narrow current path, which can effectively limit the loop current and suppress the noise. The resistance has a attenuation effect in all frequency bands (0 ohm resistance also has an impedance), which is stronger than the magnetic bead.
② For current circuit when jumper
    When the electric ground plane is divided, the shortest return path of the signal is broken, at this time, the signal circuit has to detour, forming a large loop area, and the influence of electric and magnetic fields becomes stronger, which is easy to interfere/be interfered with. The 0 ohm resistance is crossed over the partition area to provide a shorter return path and reduce interference.
③ Configuration circuit
    In general, jumpers and dip switches should not appear on the product. Sometimes the user will mess with the setting, easy to cause misunderstanding, in order to reduce maintenance costs, the application of 0 ohm resistance instead of jumper welding on the board. The vacant jumper is equivalent to the antenna at high frequency, and the resistance effect is good with the patch.
④ Other uses:
    A. When wiring, cross line B, debug/test C, temporarily replace other patch devices D, and serve as temperature compensation devices are more often required for EMC countermeasures. In addition, the 0 ohm resistance is smaller than the parasitic inductance of the hole, and the hole will also affect the ground plane (because of the hole to be dug).