[antenna] [1] explanation of some nouns and simple concepts

Preface

It's just a simple record , No matter what you see , You have to remember , Human memory is always unreliable , And I'm even less reliable .

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Specific absorption SAR

Electromagnetic power absorbed or consumed by human tissue per unit mass , Unit is $W/kg$

loop The antenna

Loop antenna （ Common use of mobile phones ）

If the perimeter is less than a quarter of the wavelength , It is thought to be a small ring road . Most directional receive loops are about one tenth of the wavelength

IFA

pour F The antenna （ Common use of mobile phones ）

MIFA

Serpentine F The antenna （ Because of the demand for miniaturization , from IFA Antenna evolution MIFA）

PIFA

Stereoscopic inversion F The antenna

Ceramic antenna （ Chip antenna ）

Very small , High dielectric constant , It looks like a capacitor , In the shape of a cuboid

The price of small patch ceramics is high , But it is easy to replace

Isolation

radio frequency RF Or intrinsic LO Leakage power at other ports is similar to RF or LO Ratio of input power , Company dB

or

$S_{21}$ ——
Antenna port isolation ,2 Yes 1 Communication of .$S_{21}<0$, Use its absolute value as the port isolation

Electromagnetic coupling feed

The change of electromagnetic field leads to the change of current , Or the electromagnetic field changes due to the change of current . So the coupling feed is unconnected 、 Air mutual inductance

So feeders and radiators （ Microstrip antenna ） Not on the same side , It reduces the interference of feeders to the pattern

The circular polarization is realized by introducing a tangent angle on the radiation patch as a perturbation element

The principle of circular polarization is to generate two orthogonal linear polarization electric field components , And their amplitudes are equal , Phase difference 90 degree . There are many ways to realize circular polarization of microstrip antenna , There is a single point feed method 、 Multipoint feed method and multivariate method . seeing the name of a thing one thinks of its function , Single point feed method has only one feed point . Firstly, the orthogonal degenerate modes are generated by appropriate feeding points , Then a perturbation element is introduced into the antenna radiation structure , Change the phase of the antenna surface current , The phase difference of two degenerate modes with orthogonal polarization 90 degree , So as to meet the requirements for radiation of circularly polarized waves . There are many ways to realize circular polarization of microstrip antenna by single point feed method , The main purpose is to introduce a suitable perturbation unit , Also known as degenerate perturbation unit , Such as corner cutting 、 Slotting, etc

The external antenna has good directivity , Efficient , Strong anti-interference ability , Keep away from interference on the motherboard . There is no need to do too much debugging and matching . The disadvantage is that it's bulky , The high cost

Dielectric loss tangent

$tan{\delta }_{\sigma }=\frac{\sigma }{ϵ\omega }=$ In a conductive medium , The ratio of the amplitude of the conducted current to the displacement current

433MHz

The length of the antenna is about... Of the electromagnetic wave length 1/4 （ Source and half wavelength single-stage antenna $l=\frac{\lambda }{4}$）, So the lower the signal frequency , The longer the antenna length . therefore 100MHz Left and right FM The radio needs a long pole antenna ,400MHz Left and right interphones , External long pole antenna is also required . Commonly used in the Internet of things 433MHz Wireless serial port , External antennas are usually used

External antenna

External antennas are generally standard , Buy the right band , No need to debug , Plug and play . For example, express cabinet 、 Vending machines, these , External antennas with magnetic suction are widely used , It can be sucked on the iron shell . These antennas can't be put in a tin cabinet , Metal shields the antenna signal , So it can only be put outside . The advantage is that it is easy to use 、 Cheapness , The disadvantage is that it can not be used in small-size products .

Receiving elevation

The included angle between the connecting line between the satellite and the receiving antenna and the horizontal plane is the receiving elevation angle

active

Active power

Mobile phone antenna technology （IFA,monopole,loop）

Metal frame

utilize Metal frame As part of the antenna —— shortcoming ： It is very difficult to debug the antenna

MDA

utilize Metal parts in the mobile phone shell As a carrier to achieve radiation function —— advantage ： The metal parts as the antenna carrier can be made into a whole with the shell by injection molding . shortcoming ： It is very difficult to repair the mold of the mobile phone shell

FPC（ Steel sheet ）

Flexible circuit board , hold PCB Pull out the antenna line on the board , Use other External metal To make an antenna —— advantage ： It is applicable to almost all small electronic products , Capable of making complex antennas of more than ten frequency bands , Good performance , The cost is also relatively low . shortcoming ： It needs to be debugged separately according to each product

LDS

Laser forming ——FPC An evolutionary version of the antenna , High space utilization

PDS

Printing molding , Using pad printing technology, conductive silver paste is directly printed on the shell to make a metal antenna shape —— advantage ： No plating required , Is a highly reliable 、 Low success Ben 、 Environmental protection process plan

Creepage

The phenomenon of dendritic discharge on the insulator surface between the two poles

Creepage distance ： The distance between conductors along the insulating surface .

PCB On slotting It can increase the creepage distance , Prevent arcing when the voltage is high

Electrical clearance

（ It's usually PCB On ） The shortest space distance between conductors

Discharge tooth

The discharge teeth are a pair of triangles pointing at acute angles to each other , It's from PCB It is made of copper foil during wiring . These triangles need to be set at PCB Place another layer of board components , Can not be covered by green oil .

（ There are both notches and discharge teeth in the picture ）

Over voltage protection , Suppress surge current

Fuse routing

Used as overcurrent protection

A straight line 、 Serpentine 、 Diamond and other complex shapes , And it's small .

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Reference source ：
Design of circularly polarized microstrip array antenna
Read a text PCB The antenna 、FPC Characteristics of the antenna
I've seen it all these years but I don't know it pcb Antenna and ceramic antenna
As long as the slot is wide enough , The creeper can't catch up with me