What are the causes of standing waves and what are standing waves?

VSWR is another measure of the degree of matching, and is generally used in devices such as transmitters and antennas. If the match is good, the load impedance is equal to the characteristic impedance of the cable, no reflection is generated, there is only an incident wave, no reflected wave, and the amplitude of the electrical signal at all parts of the cable is equal, and it is in a traveling wave state. If the match is not good, the load impedance is not equal to the characteristic impedance of the cable, and the reflection will be generated, at this time, there are both incident waves and reflected waves in the cable, and the incident wave and the reflected wave are superimposed, so that the voltage or current amplitude changes periodically along a certain distance in the cable, and the amplitude is the largest in some places, and the amplitude is the smallest in other places, forming a standing wave, and the ratio of the maximum amplitude to the minimum value is called the standing wave ratio.

In the traveling wave state, due to the equal amplitude of the electrical signals everywhere in the cable, the VSWR ratio is equal to 1, and after the standing wave is formed, the VSWR ratio is always greater than 1

The superposition of two columns of planes with opposite propagation directions, the same direction of vibration, the same amplitude, and the same frequency will form a standing wave. There is no phase condition, because the phase difference of different points is different, the combined amplitude is different, the maximum amplitude of the in-phase point is called the wave belly, and the amplitude of the inverting point is zero is called the wave node.

It is the terminal of the transmission line, short connection or impedance mismatch, etc.

The conditions for the formation of standing waves are that the transmission line terminal is broken, the short connection or impedance is mismatched, and the reflection occurs. The frequency of both waves, the transmission speed is exactly the same, but the direction is opposite.

A standing wave is a superimposed standing wave definition of two columns of waves propagating in opposite directions. In the superposition area, the vibration reinforcement point is always strengthened, forming the wave belly, and the vibration weakening point superposition is always weakened, that is, the wave node, to achieve such a stable superposition, the amplitude of the two waves must be the same, and the frequency is also the same.

The standing wave equation is:

A simple harmonic with two periods t, a wavelength and an amplitude a propagates in opposite directions along the x-axis.

1. The wave propagating along the positive direction of the x-axis is called the right-traveling wave, and the wave equation is:

y1=acos2π（t/t-x/λ）

2. The wave propagating in the negative direction of the x-axis is called the left-hand wave, and the wave equation is:

y2=acos2π（t/t-x/λ）

3. The equation for the synthesized standing wave is:

y=y1+y2=2acos2π(x/λ)cos2π(t/t)

Standing waves

Standing waves are waves that are superimposed on each other when two series of coherent waves (of the same frequency) of the same amplitude propagate in opposite directions in the same straight line. Features: The wave formed by the interference between the incident wave (propulsion and lack of search wave) and the reflected wave is no longer propelled (only the upper and lower vibrations of the wave belly, and the wave node does not move) is called a standing wave.

When the wave propagates in the medium, its waveform continues to move forward, so it is called a traveling wave; After the above two columns of waves are superimposed, the waveform does not move forward, so it is called standing finger blocking wave. To put it simply, it is a wave form in which the node is stationary, the waveform does not propagate forward, and "stops" in place.

The conditions for the formation of standing waves are:1. The transmission line terminal is broken, short-connected, or the impedance is mismatched, and there is a reflection;

2. The frequency and transmission speed of the two waves are exactly the same, but the direction is opposite. Standing wave refers to a distribution state formed along the transmission line of two waves (not necessarily radio waves) with the same frequency and opposite direction of transmission. One of these waves is generally a reflected wave of the other.

Features of Standing Waves:

1. The difference between voltage and current is not only 90° in time. There is also a spatial difference of 90°;

2. The average power is zero, so it cannot be used to transmit electromagnetic energy;

3. Have a wave belly and a wave node whose position does not change with time, and the distance between the wave node and the adjacent wave belly is 2.

The standing wave phenomenon is that if a compressed part of the tire leaves the ground, its recovery speed cannot catch up with the forward rotation speed of the wheel, and the tire that has not recovered into a circle will repeatedly contact the ground, so that the tire is easy to form irregular polygons.

When the tire produces a standing wave, the friction of the part of the tire that is deformed by the backlog will be greater, which will cause the temperature of the tire to be higher than that of other parts.

The steel wire or high-strength nylon wire inside the part of the tire that generates standing waves will also be continuously squeezed and twisted during the rolling process, resulting in material fatigue and fracture and high-speed puncture. When the wheel is rolling, the part of the tire in contact with the ground will be deformed due to compression, and the normal tire will quickly return to a round shape under the action of rubber elasticity and tire pressure after leaving the ground in the process of rolling forward.

The weight of the car will deform the part of the tire that touches the ground slightly. The part of the car that is deformed while driving will return to its original shape after leaving the road. If you look at a point on the surface of the tire, the tire rotates once, and this point undergoes a process of deformation and restoration.

Deformation and recovery take time, and when driving at high speeds, if the recovery speed cannot catch up with the speed of the tire, it will cause abnormal deformation of the standing wave behind the tire ground, which is the standing wave phenomenon.