Antenna principle Expect to finish reading in 9 minutes 1. Antenna principle 1.1 Definition of antenna: A device that can effectively radiate electromagnetic waves in a specific direction in space or can effectively receive electromagnetic waves from a specific direction in space. 1.2 The function of the antenna: Energy conversion-the conversion of guided traveling waves and free space waves; Directional radiation (receiving)-has a certain directionality. 1.3 Principle of antenna radiation 1.4 Antenna parameters Radiation parameters Half-power beam width, front-to-back ratio; Polarization mode, cross-polarization discrimination rate; Directivity coefficient, antenna gain; Main lobe, side lobe, side lobe suppression, zero point filling, beam downtilt... Circuit parameters Voltage standing wave ratio VSWR, reflection coefficient Γ, return loss RL; Input impedance Zin, transmission loss TL; Isolation degree Iso; Passive third-order intermodulation PIM3… Antenna side lobe Horizontal beam width Front-to-back ratio: specify the ratio of the forward radiation power to the antenna and the backward radiation power within ±30° The relationship between gain and antenna size and beam width Flatten the "tire", the more concentrated the signal, the higher the gain, the larger the antenna size, and the narrower the beam width; Several key points of antenna gain: The antenna is a passive device and cannot generate energy. Antenna gain is just the ability to effectively concentrate energy to radiate or receive electromagnetic waves in a specific direction. The gain of the antenna is produced by the superposition of the elements. The higher the gain, the longer the antenna length. The gain is increased by 3dB and the volume is doubled. The higher the antenna gain, the better the directivity, the more concentrated the energy, and the narrower the lobe. 1.5 Radiation parameters Polarization: Refers to the trajectory or changing state of the electric field vector in space. 1.6 Circuit parameters Return loss In this example, the return loss is 10log(10/0.5) = 13dB VSWR (Standing Wave Ratio) is another measure of this phenomenon Isolation: It is the ratio of the signal received by one polarization of the other polarization https://www.whwireless.com/

Aquatic Black Technology-IoT Hub's aquaculture intelligent monitoring system solution    The aquaculture industry is very strict in terms of environmental data requirements and sensitivity, and needs to pay attention to various data at all times. With the development of industrial Internet, Internet of Things, cloud computing and other technologies, the aquaculture industry can use these technologies to master various equipment data in real time, greatly improve the efficiency of the aquaculture industry's production, management, and service links, and accelerate the entire industry Upgrade and transformation of the chain. Project Background    A large aquaculture enterprise has several fisheries scattered across the country, and each fishery has one or more breeding equipment (controlled by PLC). However, existing equipment cannot upload status information in time and return it to the service center of the enterprise, resulting in poor controllability of the production process; water quality information cannot be updated in real time, resulting in increased production costs; equipment cannot be remotely controlled, resulting in high labor costs. The client hopes to establish a set of real-time monitoring system, which can upload on-site information in real time and grasp the situation in time.    aquaculture system monitoring solution based on IoT Hub    The IoT Hub Industrial Internet Empowerment Platform team designed an intelligent monitoring system for aquaculture based on customer pain points.   Equipment monitoring system architecture diagram The entire system IoT Hub industrial Internet empowerment platform, connected to the PLC of the aquaculture plant through the edge controller, transmits the field data to each local IoT Hub? server via WIFI or 4G, and finally each local IoT Hub uploads the data to the IoT The Hub Industrial Internet Empowerment Platform summarizes.   1 Features of IoT Hub Industrial Internet Empowerment Platform   ■ Provide powerful data storage capabilities   ■ Provide rich background service functions   ■ Provide flexible deployment methods   ■ Provide secure data protection   2 Features of Edge Controller   ■ Quick access to equipment   ■ Fast data analysis   ■ Results are uploaded quickly   ■ Remote control: You can remotely control the work of key equipment through mobile phones and tablets, requiring specific permissions.   ■ Timing trigger: The equipment can be controlled regularly through the management system and requires specific permissions.   ■ Real-time monitoring and alarm: real-time monitoring of various key data, when the parameter value reaches a dangerous value, the system sends a mobile phone text message to the manager.   ■...

What is edge computing (MEC)? To avoid the dullness of technology, let me give you an example. There is a very intelligent animal in nature-octopus. It has the highest IQ among invertebrates. Whether it is for escape or predation, it has many long tentacles that can be used freely. Scientists have found that the tentacles of the octopus are full of neurons, which can handle many actions independently. The octopus's brain only accounts for 40% of the processing. The other processing power is distributed on its 8 tentacles, which greatly enhances its strain processing. ability. If the human body is the central processing method of the brain, and 99% of its capabilities require the brain to respond, the octopus is a distributed processing system, and 60% relies on its "small brain" processing distributed in the antennae. Yes, this is the principle of edge computing. The calculation and processing capabilities are submerged to the edge closest to the business to complete. Most of them do not need to interact with the core network, and a few are interoperable with the core network. This is edge computing. The concept of Multi-Access Edge Computing (MEC) technology was first proposed in 2009 on the cloudlet computing platform developed by Carnegie Mellon University. In 2014, the European Telecommunications Standards Institute (ETSI) formally defined the basic concepts of MEC and established the MEC specification working group to start related standardization work. In 2016, ETSI extended this concept to multi-access edge computing, and extended the application of edge computing in mobile cellular networks to other wireless access networks (such as Wi-Fi). Under the promotion of ETSI, other international and Chinese standardization organizations including 3GPP and China Communications Standards Association (CCSA) have also initiated related work. Currently, MEC has evolved into one of the important technologies of 5G mobile communication systems. Why does 5G have to use edge computing? In the 5G era, mobile communication has shifted from the initial communication between people to the communication between people and things to the communication between things. AR/VR, Internet of Things, industrial automation, unmanned driving and other services have been introduced in large numbers, bringing network requirements for high bandwidth, low latency, and large connections. New services have increasingly demanding requirements for bandwidth, delay, and security, and the centralized deployment of traditional cloud computing has been unable to meet service requirements. Let's take a look at the following "5G flower" that can reflect the vision of 5G capabilities. We can see that the key capability requirements of the 5G vision are almost the pursuit of the ultimate, so that many people in the industry have always questioned: Can such a demanding 5G key capability really be realized? For example, how to realize the key capability of end-to-end delay of 1 milliseco...

Does NB iot module need a sim card? The simple answer is needed. (More wireless communication knowledge; IoT knowledge, antenna cable https://www.whwireless.com ) NB iot is deployed under the signal coverage of the existing cellular network and uses the licensed frequency band, so it can only be used through the network provided by the operator. Someone may ask why lora, which is also a low-power wide area network, can not use a sim card, while nbiot has to use a sim card? This is still related to the network frequency bands used by the two networks. NB iot devices do not need a gateway, and they rely on 4G coverage and use the spectrum in LTE, so NB-IoT is not easy to work in remote areas without 4G signals. Lora uses an unlicensed frequency band, which means that there is no frequency band operated by an operator. Therefore, Lora needs to pass through a gateway during use. NB-IoT network The NB-IoT network is shown in the figure. It can be seen that it consists of 5 parts: NB-IoT terminal. As long as the corresponding SIM card is installed, IoT devices in all industries can access the NB-IoT network; NB-IoT base station. It mainly refers to base stations that have been deployed by operators, and it supports all three deployment modes mentioned earlier; NB-IoT core network. Through the NB-IoT core network, the NB-IoT base station can be connected to the NB-IoT cloud; NB-IoT cloud platform. The NB-IoT cloud platform can process various services and forward the results to the vertical business center or NB-IoT terminal; Vertical business center. It can obtain NB-IoT service data and control NB-IoT terminals in its own center. Compared with the transport layer in the traditional IoT, NB-IoT changes the complex network deployment, in which the relay gateway collects information and feeds it back to the base station. Therefore, many problems such as multi-network networking, high cost and high-capacity batteries are solved. A network throughout the city can bring convenience to maintenance and management, and can easily solve and install advantages by separating it from property services. However, there are new security threats: Access to high-capacity NB-IoT terminals One sector of NB-IoT can support connections with approximately 100,000 terminals. The main challenge is to perform effective authentication and access control on these large-scale real-time high-volume connections to avoid malicious nodes from injecting false information. Open network environment The communication between the perception and transport layer of NB-IoT is completely through the wireless channel. The inherent vulnerabilities of the wireless network bring potential risks to the system. That is, an attacker can transmit interference signals to cause communication interruption. In addition, because there are a large number of nodes in a single sector, an attacker can use nodes controlled by him to sponsor a denial of service (DoS) attack, so he can affect network performance...