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RF SMA Connector :Describing the wireless future with radio waves

  • Categories:News Center
  • Time of issue:2021-02-03 16:31
  • Views:

(Summary description)Please take out your mobile phone and take a closer look. Do you think the mobile phone is a mobile phone because of which function it has? Yes, the obvious answer is wireless communication. Even though a mobile phone can be used to take photos, set alarms, record schedules..., its core function is still talking on the phone or surfing the Internet. Compared with the era of wired communication in the past, it was necessary to pull a line to talk on indoor phones. Today, we can talk anytime and anywhere on the road with our mobile phones. Using an invisible "wire"-electromagnetic waves, we can finally transmit signals wirelessly. This exploratory lecture was lectured by Professor Chen Shiyuan from the Department of Electrical Engineering of National Taiwan University. They explained the basis of wireless communication from the four aspects of the history of electromagnetic waves, the development of mobile phones, what antennas are, and the analysis of Conan’s "Young Detective Badge".

RF SMA Connector :Describing the wireless future with radio waves

(Summary description)Please take out your mobile phone and take a closer look. Do you think the mobile phone is a mobile phone because of which function it has? Yes, the obvious answer is wireless communication. Even though a mobile phone can be used to take photos, set alarms, record schedules..., its core function is still talking on the phone or surfing the Internet. Compared with the era of wired communication in the past, it was necessary to pull a line to talk on indoor phones. Today, we can talk anytime and anywhere on the road with our mobile phones. Using an invisible "wire"-electromagnetic waves, we can finally transmit signals wirelessly. This exploratory lecture was lectured by Professor Chen Shiyuan from the Department of Electrical Engineering of National Taiwan University. They explained the basis of wireless communication from the four aspects of the history of electromagnetic waves, the development of mobile phones, what antennas are, and the analysis of Conan’s "Young Detective Badge".

  • Categories:News Center
  • Author:Zheng Zhaoting
  • Origin:
  • Time of issue:2021-02-03 16:31
  • Views:
Information

Please take out your mobile phone and take a closer look. Do you think the mobile phone is a mobile phone because of which function it has? Yes, the obvious answer is wireless communication. Even though a mobile phone can be used to take photos, set alarms, record schedules..., its core function is still talking on the phone or surfing the Internet. Compared with the era of wired communication in the past, it was necessary to pull a line to talk on indoor phones. Today, we can talk anytime and anywhere on the road with our mobile phones. Using an invisible "wire"-electromagnetic waves, we can finally transmit signals wirelessly. This exploratory lecture was lectured by Professor Chen Shiyuan from the Department of Electrical Engineering of National Taiwan University. They explained the basis of wireless communication from the four aspects of the history of electromagnetic waves, the development of mobile phones, what antennas are, and the analysis of Conan’s "Young Detective Badge".

1

In order to fully understand the operation of the antenna, Professor Chen first reviewed the development of electromagnetics. Although humans discovered static electricity and magnetostatics as early as BC, major breakthroughs in electromagnetism have to wait until after the seventeenth century. In 1600, the British William Gilbert published the first book " De Magnete " in the field of electromagnetics ; in 1752, the founding father of the United States, Benjamin Franklin, did a number of electrical experiments, which have been used today The positive and negative electricity is also defined by him. What the above two people did is qualitative research. In 1777, the French Coulomb (Coulomb) used a sophisticated experimental device to measure the inverse square relationship between the force between two charges and the distance (Coulomb's law). This experiment opened up quantitative research in the field of electromagnetics. Afterwards, the Danish Ørsted and the French Ampère established the theory of electricity generation and magnetism; the British Faraday (Michael Faraday) built an electric motor (motor) based on this, and on September 23, 1831 Japan proved that the time-varying magnetic field can generate induced current (magnetism), and then invented the generator. The above-mentioned research was made by James Maxwell with the famous Maxwell equation, and derived the existence of electromagnetic waves from this set of equations. In 1888, the German Heinrich Hertz indirectly confirmed the existence of electromagnetic waves through experiments. The experimental device he used was also the first transmitting antenna (dipole antenna) and receiving antenna (loop antenna) in history. These two antennas are still Someone uses it.

At the end of 1901, Italian engineer Marconi (Marconi) successfully carried out transatlantic and transoceanic wireless communication, which attracted the attention of the world, and since then a lot of resources have been invested in the field of wireless communication. The first commercial mobile phone was Motorola "Black King Kong". The body and antenna are 33 cm long, weigh 800 grams, and cost about $4,000. This mobile phone looks cumbersome and expensive now, but at the time it was a classic of engineering system integration. With the evolution of semiconductor technology, battery technology, and antenna technology, the size of mobile phones has become increasingly smaller. Nokia 6150 (with black and white LCD screen) and Nokia 3310 (hidden antenna) are all products of this trend of "mobile phones than smaller". Since 2003, with the emergence of the 3G communication system, mobile Internet access has become more and more popular. Small screens and small keyboards are no longer favored by the market. Apple's first-generation iPhone has become an epoch-making mobile phone invention due to the touch screen. Now that large screens and high-endurance batteries are the mainstream in the market, mobile phones are getting bigger and bigger. Professor Chen pointed out that since the invention of the mobile phone, the hand structure has been small and then large, like a "smile curve."

As far as mobile phone antennas are concerned, the current built-in antennas need to consider many aspects. The built-in antenna design must consider the entire mobile phone, no longer the interactive use of mobile phone antennas in the past. Taking the iPhone 4 as an example, engineers designed the antenna for the beauty and symmetry of the mobile phone, resulting in poorer communication performance than expected. In addition, although the metal back cover enhances the texture of the phone, it also shields the signal. The antenna design also needs to be adapted to "mechanical" conditions.

So what is an antenna? Antenna in English has two meanings: antenna and antennae. Professor Chen said that antennas are like electronic eyes and ears for humans to perceive electromagnetic waves. For people in the field of wireless communication, an antenna is a device that emits and receives electromagnetic waves. Antenna experts describe the characteristics of antennas in terms of "radiation pattern". Commercial antennas have four important parameters, namely directivity, radiation efficiency, gain, and equivalent isotropic radiation power (EIRP). The directivity is the data of whether the antenna radiates in a specific direction and the energy is concentrated or not. The spherical field pattern with the worst directivity is used as the definition standard. The radiation efficiency is affected by the material of the antenna and is the ratio of the power at the circuit end to the total power radiated by the antenna. The gain, which is the directivity multiplied by the radiation efficiency, is a parameter usually used when describing an antenna. The equivalent omnidirectional radiated power is the gain multiplied by the output power. The current electromagnetic wave-related regulations use EIRP as the control standard.

With the knowledge of the above antennas, Professor Chen asked everyone to think about the fictitiousness and reality of the wireless transceiver "Young Detective Badge" in Detective Conan. According to the story, the "Juvenile Detective Badge" is a thin, short and small point-to-point wireless communication system. It has two important features: limited power consumption and its monopole antenna radiates in all directions. If according to the hypothesis of the story, the "Juvenile Detective Badge" is point-to-point communication, the signal may be limited by distance and building obscuration. To maintain point-to-point communication, it must be transmitted with strong power or transmitted through artificial satellites. In order to balance power consumption and stable communication quality, a "junior detective badge" based on a cellular base station is more feasible. In addition, the base station system has the advantages of high mobility, cross-zone communication, miniaturization of devices, strong environmental adaptability, and improved spectrum efficiency.

Finally, Professor Chen concluded with an analysis of "Are the base stations terrible?" The EIRP of a general base station is between 5 and 50 watts, which is far less than the output power of digital TV and FM and AM radio stations. Since the power density of electromagnetic waves is inversely proportional to the square of the distance, a simple calculation shows that the power density of the base station is only about one ten thousandth of the power density of the mobile phone (using EIRP as 2 watts), so as long as the reception is good, there is no need to worry . Professor Chen hopes that everyone can uphold the "scientific spirit" and make careful judgments.

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