Due to its nature, intelligent construction mainly provides a safe and accurate working environment for the campus. The entrance and exit personnel of the school are quite complicated, and the criminals just use this environmental factor to wait for an opportunity to commit crimes, which directly affects the safety of the students and school staff. At the same time, the school where the project is located is a high school with a boarding student. Avoiding the phenomenon of students going out at night and returning to the night, the original school had hired a number of security guards, which not only increased the workload of the campus security department, but also felt that the effect was not good. Therefore, the establishment of a scientific and reasonable security system for digital video surveillance systems is an effective means of campus defense.
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Adhering to the advanced design, reliability, safety, scalability, and normative design principles, according to the overall architectural plan of the campus, and taking into account the actual situation on the site, the front-end design uses high-definition color cameras, and the video transmission uses campus network and Anti-interference high-shielded coaxial cable, control signal transmission uses dedicated control cable to ensure accurate transmission of video signals and control signals; control video recording system uses digital hard disk video recording system, which can realize cyclic recording and facilitate retrieval and playback.
The closed-circuit monitoring system consists of three parts: front-end image acquisition, image and control signal transmission, and image display control storage.
Front end image acquisition section
The camera section is usually installed at the surveillance site. It generally includes a camera, a lens, a shield, a bracket, and a uniform ball. Its role is to take pictures of the surveillance area and convert it into a video signal. The camera is divided into color and black and white. Generally, the color is turned into a black-and-white camera (turning to black and white at night or when the light source is poor). It is more suitable for the place where the light is insufficient. The installation method of the camera is fixed and the pan/tilt is fixed.
The campus closed-circuit television monitoring system is designed with infrared integrated cameras in important places such as the main entrance, main passage, teaching building, student dormitory, and main perimeter. The infrared dome machine is installed in the canteen. The student playground considers the monitoring scope to be spacious, mainly monitoring the daytime personnel activities. Therefore, the camera without the infrared zoom camera is used. The above design basically guarantees that any disputes and incidents between Japanese and Japanese staff and office personnel in the office can provide effective treatment basis, and can effectively deal with hidden dangers or disputes in time; the monitoring room is set at the gate office. In the region, it can be supervised by itself, which strictly guarantees that the duty personnel can view the important passage site and strictly implement the secrecy system.
There is now a TV surveillance system that packages the pan/tilt, zoom lens and camera together to form an integrated camera. They are equipped with an advanced servo system, which has a high rotational speed and can also be preset for monitoring points and patrol paths. Usually, the automatic patrol is carried out according to the set route. Once an alarm occurs, the alarm point can be quickly aligned, and the fixed point monitoring and video recording can be performed. A camera can function as several cameras.
Image and control signal transmission section
The transmission system includes the transmission of video signals and control signals.
Video signals can be transmitted over coaxial cable, fiber optic or twisted pair. Video conversion adapters are required for transmission over twisted pair.
Control signal transmission methods include:
Direct control: Direct control of the control center, such as the power supply current of the pan/tilt and zoom lens, directly sent to the controlled device. Features are simple, intuitive and easy to implement. Applicable when there are few field devices and the host is manually controlled. However, when the number of controlled pan/tilt and the number of lenses is large, the number of control cables is large and the lines are complicated, so they are not used in large systems.
Indirect control of multi-line coding: The control center encodes the control commands into binary or other parallel codes, which are transmitted to the control device on site by multiple lines, and then converted into control quantities to control the on-site camera equipment. This method uses less lines than the previous method and is often used in close-range control.
Indirect control of communication coding: With the popularity of microprocessors and various integrated circuit chips, most large-scale TV monitoring systems currently use communication coding, and serial coding is commonly used. Its advantage is that a single line can transmit multiple control signals, which greatly saves the line cost. The communication distance can reach more than 1km without adding intermediate processing, and the processing can transmit more than 10Km. This overcomes the shortcomings of the previous two methods. This system uses this control.
In addition to the above methods, there is also a coaxial video transmission method in which a control signal and a video signal are multiplexed with one cable. This method does not require a separate control cable. There are two ways to achieve it: one is frequency division, that is, the control signal is modulated in a different frequency range from the video signal, and then transmitted together with the video signal, and then decomposed after being in the field; another method The control signal (coaxial video control) is transmitted during the blanking period of the video signal field. This method is significantly better than other methods in short-distance transmission, but the price of the equipment is relatively expensive.
In this project, the video signal of CCTV monitoring system adopts shielded video cable. According to the installation position of the camera, SYV-75-3/96 braided coaxial cable is selected to ensure the accurate transmission of monitoring information.
Image control storage section
Display and recording devices are installed in the control room, mainly including monitors, hard disk recorders, and some video processing devices. Image monitors are mainly divided into two categories: black and white and color. The center resolution of a black and white monitor is usually above 800 lines, and the center resolution of a color monitor is generally 400 lines or more. The bandwidth of the image monitor video signal is generally in the range of 7 to 8 MHz.
The monitoring center computer room is located in the doorkeeping room. The monitoring room video system is designed with two 16-channel digital hard disk recorders, and two 7-inch flat-panel displays are equipped for real-time monitoring. The entire hard disk recording system can be designed to continuously store 30 days of video data. The hard disk recording system supports full-duplex work of recording and playback.
System power and control room requirements
In order to ensure the normal and stable operation of the monitoring system, the system is required to use the online UPS for centralized power supply;
The monitoring system and the central control room use separate power supply circuits;
The trunk is powered by AC220V, and is powered by a transformer at the front end of the camera;
The central control room must be equipped with equipment for communication, safety and fire protection;
The central control room must be equipped with an air conditioning unit separately to ensure that the temperature of the control room is between 16 and 28 Â° C and the relative humidity is not more than 85%.
The control room has sufficient light and its illumination should be no less than 300Lux;
Â· Real-time video surveillance of public gate areas such as the gate environment, channels, and playgrounds;
Â· Real-time monitoring of the entry and exit of personnel vehicles at the gate, and the video surveillance of the personnel entering and leaving the administrative office building;
Â· The overall situation of the student dormitory realizes video surveillance management;
Â· Can adapt to a certain degree of low illumination changes;
Â· Video recording of each point can be recorded for security check;
Â· Effectively guarantee the safety activities of students and staff;
Â·Operating software interface is intuitive and user-friendly;
Â· Set up cabinet management for the monitoring host, and perform password management on the system operator to perform multi-function settings on the system.
Campus security construction can not be ignored, relying solely on personnel to be on duty and simple management, can no longer support the important responsibility of security. The strict management of security personnel is of course important, but it is also an urgent task to build a campus security system that can be managed by the school and can be remotely supervised by public security organs and education bureaus. It is crucial to consider the security network that can be intervened by other campus multi-functional systems in the whole design concept. If the unilateral implementation of a simple security management system cannot support the rapid development of the safe campus implementation, it is safe throughout the campus. In the system design, we must consider the extension and expansion for the future development of science and technology. This is an advanced concept that professional security companies must have.
High Frequency PCB - Definition, Characteristics, Manufacturing, Materials and Application Scenarios
With the development of science and economy, the electronic industry has become an important driving force for economic development. Electronic products have become a part of life, affecting people's way of life. High-frequency circuit boards are widely used in many electronic industries and some instruments and equipment, and high-frequency PCB applications are also increasing. Choose high-frequency circuit board manufacturers in good service to buy high-quality products for use, we have to understand the relevant knowledge of high-frequency board.
What Is A High Frequency Circuit Board?
High frequency circuit board (HF PCB) is a special circuit board with high electromagnetic frequency. Generally speaking, high frequencies can be defined as frequencies above 1GHz. Its physical performance, accuracy and technical parameters are very demanding. It is often used in automobile anti-collision system, satellite system, radio system and other fields.
High Frequency PCB include:
- Rogers high frequency PCB
- Power amplifier high frequency PCB
- Buried blind hole mixed high frequency PCB
- Ceramic high frequency PCB
- Ceramic mixed high frequency PCB
- Communication antenna high frequency PCB
- GPS antenna high frequency PCB
- FR-4 high frequency PCB
- Double sided high frequency PCB
- Microwave High Frequency PCB
- Induction High Frequency PCB
- 2.4G Radar Induction PCB
- 5.8G Microwave Induction PCB
The utility model patented high frequency circuit board includes a core board with a hollow groove and a copper clad plate adhering to the surface and the lower surface of the core board by flow glue. The upper opening and the lower opening edges of the hollow groove are provided with a baffle.
The high frequency circuit board provided by the utility model is provided with a barrier which can block the flow glue at the upper and lower edges of the hollow groove of the core board.
In this way, the flow glue will not enter the hollow slot when the core plate is bonded with the copper clad laminate placed on the upper and lower surfaces, that is, the bonding operation can be completed by one press.
Compared with the existing technology, the high frequency circuit board can only be completed by secondary pressing. The high frequency circuit board in the utility model has the advantages of simple structure, low cost and easy manufacture.
Characteristics of High Frequency Circuit Board
Generally speaking, high frequency circuit boards have their own characteristics: low dielectric constant, relatively stable. In theory, the smaller the dielectric constant, the more stable the signal, and the higher the frequency circuit board can play a better role in signal transmission. Medium loss is very small, it is not easy to absorb water and moisture, heat resistance, corrosion resistance and other excellent performance. Conversely, if the dielectric constant is high, the signal transmission process is slow.
The thermal expansion coefficients of high frequency circuit boards and copper foil are also correlated to a certain extent. They are consistent as far as possible. The inconsistency can easily lead to the separation of copper foil in the alternate change of heat and cold. The later use will affect the signal transmission of PCB. The absorbency of high frequency circuit board is lower than that of other multi-layer circuit boards, because humidity will affect the dielectric constant and dielectric loss of high frequency circuit board. In addition, the heat resistance, chemical resistance, impact strength, peeling strength and other requirements are also good.
High frequency signals are vulnerable to noise and come with much tighter impedance tolerance as compared to conventional circuit boards.
High Frequency Circuit Board Materials
High frequency PCB have their own unique plates. Special materials are used to attain the high frequency given by the High Frequency PCB. PCB manufacturer commonly used Materials are: rogers(Rogers 4350B HF.Rogers RO3001.Rogers RO3003).Taconic(RF-35 Ceramic.TLX). Arlon(85N).Isola(IS620 E-fibre glass).F4B.TP-2.FR-4,Dielectric constant 2.2-10.6 and so on. FR4 is the cheapest one, while Teflon is the most expensive one. But they all have a common characteristic, which is the resin used in the material. The wiring of high frequency circuit board is exquisite and has great influence on components. High-frequency signals have the strongest impact on analog devices, so we should deal with the relationship between them to achieve the best performance. Therefore, high frequency is not easy to pass through high capacity electrolytic capacitors with poor high frequency performance.
The substrate material used in the high-frequency circuit board needs to have excellent electrical properties, good chemical stability, and the loss on the substrate is very small as the frequency of the power signal increases, so the importance of the high-frequency board is highlighted.
Therefore, when selecting a substrate for a PCB for a high-frequency circuit, it is particularly necessary to examine the various characteristics of the material DK at different frequencies. For the requirements of high-speed transmission of signal emphasis, or characteristic impedance control requirements, focus on DF and its performance under conditions of frequency, temperature and humidity.
Under the condition of frequency change, the general type of substrate material shows a large change of DK and DF values. Especially in the frequency range of l MHz to l GHz, their DK and DF values change more significantly. For example, a general-type epoxy resin-glass fiber-based substrate material (general type FR-4) has a DK value of 4.7 at a frequency of 1 MHz, and a DK value of 4.19 at a frequency of 1 GHz. Above lGHz, its DK value tends to be flat. The changing trend is smaller as the frequency increases (but the change is not large). For example, at 10 GHz, the DK value of FR-4 is generally 4.15, and the substrate material having high-speed and high-frequency characteristics changes in frequency. In the case of DK, the DK value changes little, and the DK keeps changing in the range of 0.02 from the frequency of change from 1 MHz to 1 GHz. Its DK value tends to decrease slightly from low to high frequency.
The dielectric loss factor (DF) of a general type of substrate material is affected by a change in frequency (especially in a high-frequency range), and the change in DF value is larger than that of DK. The law of change tends to increase. Therefore, when evaluating the high-frequency characteristics of substrate material, the focus of its investigation is on the change of its DF value. There are two distinct types of two types of substrate materials with high-speed and high-frequency characteristics. In general, there are two different types of substrate materials: one is that the (DF) value changes little with frequency. There is also a class that, although similar in magnitude to the general substrate material, has a lower (DF) value.
High-frequency circuit boards with induction heating technology have been widely used in the communication industry, network technology field promotion and high-speed information processing systems to meet the requirements of many high-precision parameter instruments. A reliable high-frequency circuit board provides great help in actual production.
From material DF:
The circuit board material with DF between 0.01 and 0.005 is suitable for the digital circuit with the upper limit of 10Gb / S;
DF between 0.005-0.003 is suitable for digital circuits with an upper limit of 25gb / s;
Circuit board materials with DF no more than 0.0015 are suitable for 50GB / s or even higher speed digital circuits.
Common high-speed PCB materials are:
1) Rogers: ro4003, ro3003, ro4350, ro5880, etc
2) TUC: tuc862, 872slk, 883, 933, etc
3) Panasonic:Megtron4.Megtron6, etc
4) Isola: fr408hr, is620, is680, etc
5) Nelco:N4000-13.N4000-13EPSI, etc
Of course, there are many other high-frequency board materials, such as Arlon (acquired by Rogers) and Taconic, which are all old brand RF microwave material factories with guaranteed performance.
Our most common request is for FR-4 material, which is composed of woven fiberglass bound by an epoxy resin, and which we always keep stocked as one of our PCB Options at a Standard Price. FR-4 is a robust material with excellent thermal characteristics, and electrically it is known to perform quite reasonably at RF or Microwave frequency levels.
Some clients whose designs are intended for particularly demanding applications-such as high-power or broadband circuits-find that FR-4 sometimes just does not do the job at those higher frequencies. In these cases, we are always happy to help you find a laminate material to suit your specific needs, and our highly customizable PCB Assembly Process can be easily adjusted to make sure your project lead time is not impacted.
A snapshot of the datasheet for FR-4 material is shown below for reference.
The most popular high-frequency-specific laminate materials were developed by Rogers, and referred to with an [RO-[ prefix. These high-quality materials exhibit approximately a 20% reduction in dielectric constant, compared to standard FR-4; they also boast rather impressive thermal characteristics, with Tg values above 280Â°C . A snapshot of the datasheet for RO4350B and RO4003C is included below for your convenience.
Requirements for Manufacturing Materials of High Frequency PCB
1. Dielectric loss (Df) must be small, which mainly affects the quality of signal transmission. The smaller the dielectric loss, the smaller the signal loss.
2. Low water absorption. High water absorption will affect dielectric constant and dielectric loss when damped.
3. The dielectric constant (DK) must be small and stable. Usually the smaller the better. The transmission rate of the signal is inversely proportional to the square root of the dielectric constant of the material. High dielectric constant easily causes signal transmission delay.
4. The coefficient of thermal expansion of copper foil is the same as that of copper foil, because the inconsistency will cause the separation of copper foil in the change of cold and heat.
5. Other heat resistance, chemical resistance, impact strength and peeling strength must also be good.
Generally speaking, high frequency can be defined as frequency above 1 GHz. At present, most of the high frequencies used are fluorine dielectric substrates. Teflon is much better than other substrates, such as PTFE, which is usually called Teflon. However, Teflon substrate has the disadvantage of high cost and large heat resisting property..
How to choose high frequency high speed PCB material
To select the PCB substrate, a balance must be made among meeting the design requirements, mass production and cost. In short, the design requirements include electrical and structural reliability. Generally, when designing a very high-speed PCB Board (frequency greater than GHz), PCB material problem will be more important. For example, the FR-4 material, which is commonly used now, has a large dielectric loss DF (dielectric loss) at several GHz, which may not be applicable.
For example, 10Gb / s high-speed digital signal is a square wave, which can be regarded as the superposition of sine wave signals of different frequencies. Therefore, 10Gb / s contains many different frequency signals: 5GHz fundamental signal, 3-order 15GHz, 5-order 25ghz, 7-order 35GHz signal, etc. The integrity of the digital signal and the steepness of the upper and lower edge are the same as the low loss and low distortion transmission of the RF microwave (the high-frequency harmonic part of the digital signal reaches the microwave frequency band). Therefore, in many aspects, the selection of high-speed digital circuit materials is similar to the requirements of RF microwave circuits.
The main factors to be considered in the selection of suitable base materials are as follows:
2. Various performances (electrical, performance stability, etc.) matching with products:
Low loss, stable Dk/Df parameters, low dispersion, small variation coefficient with frequency and environment, small tolerance of material thickness and glue content (good impedance control), if the trace is long, consider low roughness copper foil. In addition, the high-speed circuit needs to be simulated in the early stage of design, and the simulation result is the reference standard of the design. "Xingsen Technology-Agilent (High Speed/RF) Joint Lab" solves the performance problems of inconsistent simulation results and tests. It has done a lot of simulation and actual test closed-loop verification, and the simulation can be consistent with the actual measurement through unique methods.
3. The availability of materials in a timely manner:
Many high-frequency board material procurement cycles are very long, even 2-3 months; in addition to the conventional high-frequency board material RO4350 in stock, many high-frequency boards material need to be provided by customers. Therefore, high-frequency plates need to communicate with manufacturers in advance, and prepare materials as soon as possible;
5. Applicability of laws and regulations:
It should be integrated with environmental protection regulations of different countries to meet the requirements of RoHS and halogen-free.
Among the above factors, the high-speed digital circuit operation speed is the main factor to be considered in PCB material selection. The higher the speed of the circuit, the smaller the DF value of the selected PCB material. The low loss circuit board will be suitable for 10Gb / s digital circuit; 25gb / s digital circuit needs to select the board with lower loss; ultra-low loss board will be suitable for the faster high-speed digital circuits, and its speed can be 50GB / s or higher.
How to Make High Frequency Circuit Board?
Fabrication Principle of High Frequency Circuit Board
In the design of high frequency circuit, the power supply is designed in the form of layers, which is much better than that in the form of buses in most cases, so that the circuit can always follow the path with the smallest impedance. In addition, the power board has to provide a signal loop for all generated and received signals on PCB, which can minimize the signal loop and reduce noise, which is often ignored by low frequency circuit designers.
In the design of high frequency PCB, we should follow the following principles:
- Unity of power supply and ground, stability.
- Careful wiring and proper termination can eliminate reflection.
- Careful consideration of wiring and proper termination can reduce capacitive and inductive crosstalk.
- Noise suppression is needed to meet EMC requirements.
Points for Attention in Manufacturing High Frequency Circuit Board
1. Impedance control is strict, relative line width control is very strict, general tolerance is about 2%.
2. Because of the special plate, the adhesion of PTH copper deposit is not high. Usually, plasma treatment equipment is needed to roughen the through-hole and surface to increase the adhesion of PTH copper and solder resist ink.
3. Do not grind the plate before welding resistance, otherwise the adhesion will be very poor, and can only be coarsened with micro-corrosive powder.
4. Most of the sheets are PTFE materials. There will be many rough edges when they are formed by ordinary milling cutters, which need special milling cutters.
5. High frequency circuit board is a special circuit board with high electromagnetic frequency. Generally speaking, high frequency can be defined as frequency above 1 GHz.
Its physical performance, accuracy and technical parameters are very demanding. It is often used in automobile anti-collision system, satellite system, radio system and other fields.
Scenario and Field of High Frequency Circuit Board Application:
- Communication Base Station
- GPS antenna
- Radio Frequency Antenna
- power amplifier
- Signal amplifier
- Wave filter
- Power divider
- 3DB Bridge, etc.
Nowadays, the high frequency of electronic equipment has become a trend of development, especially in the growing development of communication networks, aerospace, military equipment, intelligent transportation, information products are also increasingly high-speed and high-frequency. Nowadays, with the development of science and economy, many new products need high frequency circuit boards. High frequency circuit boards play an increasingly important role in people's daily life.
It is not easy to find a fast and good manufacturer of high frequency circuit boards. Jinghongyi PCB has its own unique board advantages in making high frequency circuit boards. It has reliable automatic production equipment and testing equipment.
Reasons for Choosing Jinghongyi PCB
1. Top imported raw materials for high frequency circuit boards to ensure product quality from the source
- Plate: Shengyi, South Asia, KB.Rogers.Taconic. Isola. Arlon.F4BM.Nelco.Hitachi.
- Potions: Rohm&Haas (US) Atotech (Germany) Umicore (Germany)
- Ink: Taiyo (Japan)
- Dry membrane: Asahi (Japan), Dupont (US)
2. Full set of surface treatment equipment to meet the needs of various industries
We are one of the few companies in PCB industry equipped with complete surface treatment equipment.We can deal with the Immersion Gold completely.
Immersion Silver, Immersion tin, OSP, tin spraying, gold plating, thick gold plating, tin plating, silver plating and other related requirements.
3. Leading PCB Multilayer Circuit Board Technology Capability
- Maximum Layer: 28 layer
- Maximum Plate Thickness: 6.0mm
- Maximum Thickness to Diameter Ratio 10:1
- Maximum Copper Thickness: 6OZ
- Maximum working plate size: 1000x610mm
- Thinnest 4 Layer PCB : 0.33mm
- Minimum mechanical hole/pad: 0.2/0.40mm
- Drilling accuracy: +/-0.05mm
- PTH Aperture Tolerance: +/-0.05mm
- Minimum Linewidth/Line Spacing: 3mil/0.075mm
4. Strict PCB quality control system to effectively guarantee product performance
- Strictly control according to IPC standard to ensure 100% qualified rate of shipment quality.
- Implement quality PDCA cycle process to continuously improve product performance
- Imported DIONEXICS-900 and Temperature Cycle Inspection Equipment from USA to ensure high reliability and stability of products
5. Top Technical Team
Eight years of focus on R&D and manufacture of high-frequency board and microwave radar RF circuit board, with a dedicated, united and tenacious R&D team, customers NPI stage products, all into the process evaluation system, meet the evaluation criteria of the project, further review by the R&D team and file a case tracking the whole process.
The staff has 3-12 years of professional and technical personnel with multi-layer circuit board experience. They have rich experience in various industry standards and process quality requirements.
6. Intimate service
Service concept: regard customers as eternal partners, develop together, only choose reputation, not customers, regardless of the size of customers, in the case of customer needs, to provide the best service.
Flexible service: We will be eager to meet the customers'needs, think what they want, and do our best to help customers solve problems, reduce losses or promote project development.
- Ten PCB Routing Rules for High Frequency Circuits
- Difference between High Frequency Circuit and High Speed Circuit
- Interference Analysis and Countermeasure in High-Frequency PCB Design
High Frequency PCB
High Frequency PCB, High Frequency Circuit Board, High Frequency PCB Design, High Frequency PCB Materials
JingHongYi PCB (HK) Co., Limited , https://www.pcbjhy.com