Why Impedance Matching Is Necessary WWW.WHWIRELESS.COM Estimated reading time: 15 minutes The biggest difference between radio frequency (RF) and hardware lies in impedance matching, and the reason for impedance matching is the transmission of electromagnetic fields. As we all know, an electromagnetic field is the interaction between an electric field and a magnetic field. The loss in the transmission medium occurs because the electric field causes oscillations in its effect on electrons. The higher the frequency, the more cycles of electromagnetic waves there are in a transmission line of the same length, and the higher the frequency of current changes. As a result, the heat loss generated by oscillations increases, leading to greater losses in the transmission line. At low frequencies, since the wavelength is much longer than the transmission line, the voltage and current on the transmission line in the circuit remain almost unchanged, so the transmission line loss is very small. Meanwhile, if reflection occurs during wave output, the superposition of the reflected wave with the original input wave may lead to a decline in signal quality and also reduce the efficiency of signal transmission. Whether working on hardware or RF systems, the goal is to achieve better signal transmission, and no one wants energy to be lost in the circuit. When the load resistance is equal to the internal resistance of the signal source, the load can obtain the maximum output power. This is what we often refer to as impedance matching.  It is important to note that conjugate matching is for maximum power transmission.    According to the voltage reflection coefficient formula \( \Gamma = \frac{Z_L - Z_0}{Z_L + Z_0} \), \( \Gamma \) is not equal to 0 at this time, meaning there is voltage reflection.    For distortionless matching, the impedances are completely equal, so there is no voltage reflection. However, the load power is not maximized in this case. Return Loss (RL) = \( -20\log|\Gamma| \) Voltage Standing Wave Ratio (VSWR) = \( \frac{1 + |\Gamma|}{1 - |\Gamma|} \) The relationship between standing wave ratio and transmission efficiency is shown in the table below:    Impedance matching involves a rather tedious calculation process. Fortunately, we have the Smith Chart, an essential tool for impedance matching. The Smith Chart is a diagram composed of many intersecting circles. When used correctly, it allows us to obtain the matching impedance of a seemingly complex system without any calculations. The only thing we need to do is read and track data along the circular lines.    ## Smith Chart Method  1. After connecting a series capacitor component, the impedance point moves counterclockwise along the constant-resistance circle it is on.  2. After connecting a shunt capacitor component, the impedance point moves clockwise along the constant-conductance circle it is on.  3. After connecting a series ind...

What is Antenna Gain, and is Higher Always Better? WWW.WHWIRELESS.COM Estimated 10minutes to finish reading Let's discuss what antenna gain is and whether a higher value is always preferable. In reality, it entirely depends on the application of the antenna. Take a flashlight as an example: if you remove the reflector, the light will obviously become less intense. However, if you need an omnidirectional light source to evenly illuminate a room, removing the reflector to allow the light to spread out uniformly is more appropriate. Conversely, if the goal is to create a laser, using a lens to focus all the light from the bulb into a narrow beam is undoubtedly an improvement. But this concentrated beam is unsuitable for lighting up an entire room.   This phenomenon of concentrating light in a specific direction is called directivity, and the degree of concentration is referred to as gain. In the field of antennas, these two concepts behave very similarly to those of a light source. Imagine an antenna radiating energy uniformly in all directions like a candle; this is a non-directional isotropic radiator. Technically, this is defined as 0 dBi, meaning the radiation energy is the same in every direction.   Now, if you place a mirror next to the candle, the mirror will alter the distribution of light energy and give the candle directivity. The mirror will make half of the room darker and the other half brighter because the light is reflected and concentrated in one direction. This approach of "stealing" and redirecting energy from less favorable directions to enhance it in certain directions also applies to antennas.   Therefore, antennas do not generate radio energy; they merely transfer, guide, or concentrate it in a specific direction. This directional characteristic is known as gain. A mirror can redirect half of the candle's energy, making it appear twice as bright in certain directions—equivalent to two candles. In this case, we say the mirror provides a gain of 3 dB because it doubles the energy.   It is important to mention that the unit for measuring antenna gain is the decibel (dB). However, it is typically relative to a reference antenna. Usually, the radiation intensity of an omnidirectional antenna or a half-wave dipole antenna with the same input power in a certain direction is used as the reference value. When using an omnidirectional antenna as the reference, it is denoted as dBi (i - isotropic), and when using a half - wave symmetric dipole antenna as the reference, it is denoted as dBd (d - dipole).   From the definition of antenna gain, we can understand that it refers to the square ratio of the electric field strengths (i.e., the power ratio) produced by an actual antenna and an ideal radiation element at the same point in space under the condition of equal input power. It quantitatively describes the degree to which an antenna concentrates and radiates the input power.   The gain performance of an ante...

From the perspective of energy conversion, unlocking the evolution code of antennas WWW.WHWIRELESS.COM Estimated 15minutes to finish reading In the vast system of wireless communication, antennas play a key role. Essentially, they are a very special type of energy converter that can achieve energy conversion between guided waves and free space waves. This conversion process is of paramount importance in the transmission and reception stages of communication signals. When in the signal transmission state, the high-frequency current from the transmitter is transmitted along the transmission line to the antenna. At this moment, the antenna acts like a magical wizard, skillfully converting the energy in the form of guided waves (high-frequency current) into free space waves, which we commonly refer to as electromagnetic waves, and then radiating them into the surrounding space. For example, in common mobile phone communication, the internal circuits of the phone generate high-frequency current signals, which are transmitted to the phone's antenna. The antenna then converts these signals into electromagnetic waves and emits them, establishing a communication connection with the base station to achieve information transmission. In the signal reception phase, the antenna's work is the reverse of the above process. When electromagnetic waves propagating in space reach the antenna, it sensitively captures these electromagnetic waves and converts the energy they contain into high-frequency current, which is the conversion from free space waves to guided waves. This high-frequency current is then transmitted through the transmission line to the receiver for subsequent signal processing and information extraction. For example, the television antenna in our home can receive electromagnetic waves emitted by television stations and convert them into electrical signals, which are transmitted to the television, allowing us to watch a variety of television programs. Early Exploration: The Prototype of Antennas and Initial Energy Conversion In the 19th century, the field of electromagnetism witnessed significant theoretical breakthroughs. James Clerk Maxwell proposed the famous Maxwell equations, theoretically predicting the existence of electromagnetic waves and laying a solid theoretical foundation for the birth of antennas. In 1887, German physicist Heinrich Hertz conducted a series of pioneering experiments to verify Maxwell's predictions. He designed and manufactured the world's first antenna system, consisting of two metal rods about 30 centimeters long, with the ends connected to two metal plates of 40 square centimeters. Electromagnetic waves were excited through spark discharges between the metal balls; the receiving antenna was a single-loop metal square ring antenna, which indicated that a signal was received when sparks appeared between the endpoints of the ring. Hertz's experiment not only successfully confirmed the existence of electromagnetic waves b...

Exploring the 700MHz Band:Why It Is Regarded as the"Golden"Frequency in the Communication World https://www.whwireless.com/ Estimated 15minutes to finish reading In today's era of rapidly developing communication technology,frequency bands are like"magic keys"in the world of communication,unlocking different"treasures"of communication.Among them,the 700MHz band is particularly favored and is hailed as the"golden"frequency band.What are the secrets behind this?Let's delve into it together.  Superior Propagation Characteristics:Signals Travel Unimpeded Just as marathon runners experience fatigue,signals also attenuate during propagation.The 700MHz band can be regarded as a"long-distance runner"in the communication world.According to the free-space propagation loss formula,the lower the frequency,the smaller the propagation loss.Compared to higher-frequency bands such as 2.6GHz and 3.5GHz,the 700MHz band experiences much less signal attenuation.This means it can cover longer distances and deliver signals stably to their destinations.Whether in remote mountainous areas or vast rural regions,it can easily provide coverage. Strong Diffraction:Overcoming Obstacles When signals encounter obstacles like high-rise buildings or towering mountains,high-frequency signals often get blocked.However,the 700MHz band,with its longer wavelength,demonstrates strong diffraction capabilities.Like a nimble dancer,it can cleverly bypass obstacles and continue on its way.This characteristic ensures stable signal propagation in complex urban environments,preventing communication signals from being easily"intercepted"by obstacles. Deep Penetration:Full Signal Strength Indoors Indoor signal weakness is a common problem.However,the 700MHz band has excellent penetration capabilities,allowing it to easily pass through building walls and reach every corner of the interior.This means that indoors,we can enjoy smooth communication services without worrying about weak signals.Whether streaming videos,playing games,or making video calls,the signal remains strong. Cost-Effective Network Deployment In communication network construction,base stations are the key"signal fortresses."The low propagation loss and wide coverage of the 700MHz band bring significant cost advantages for network deployment.Calculations show that with the 700MHz band,building 450,000 to 500,000 base stations is sufficient to cover the entire country.If other frequency bands were used,achieving the same coverage would require a much larger number of base stations.This would not only significantly increase construction costs but also lead to higher maintenance and management expenses.The 700MHz band,with its advantages,greatly reduces the burden on operators,making communication network construction more economical and efficient. Wide-Area Coverage:A Boon for Remote Areas  In rural and mountainous regions with vast areas and sparse populations,as well as high-speed scenarios like high-speed rail and hig...