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What is the common impedance induction of RFI component interference path

  RFI component is the abbreviation of anti RF interference component. RF interference is the interference generated at or very close to the signal frequency received by the receiver. The Federal Communications Commission (FCC) of the United States has formulated RF interference standards for electronic equipment to minimize this interference.   RFI components generally include RFI gaskets, common mode chokes, ferrite beads and other products.   Interference voltage will be generated when interference current flows through impedance Z. The interference voltage caused by common impedance induction is divided into the following categories:   First of all, from the internal circuit layout and ground wire design of the equipment, when a power supply supplies several circuits, the output current of the high-level circuit will flow into the power supply in whole or in part, resulting in interference. For high frequency, the output impedance of the power supply and the distributed inductance of the power lead can cause interference.   Similarly, when there is high-frequency current on the grounding system inside the equipment, there will be the problem of converting the impedance of the grounding system into voltage. When it forms a part of the input circuit of the low-level signal amplifier, the voltage of the grounding system will be amplified and output in the form of interference.   Secondly, from the perspective of shared power supply and grounding wire, when several devices and RF devices are powered by the same AC power supply, the high-frequency current generated by the RF device is converted into interference voltage to other devices through the impedance Z of the shared power supply, and it should be transmitted through the power source line.   It should also be noted that if each equipment uses a common wiring as the grounding wire, mutual interference will inevitably occur when there is a large current flowing on the common grounding wire.

What is FPGA field programmable gate array

  Field programmable gate array (FPGA) is the product of further development on the basis of programmable devices such as pal (programmable array logic) and gal (general array logic). As a semi custom circuit in the field of application specific integrated circuits (ASIC), it not only solves the shortcomings of custom circuits, but also overcomes the shortcomings of the limited number of programmable devices.   The mainstream manufacturers of field programmable gate array FPGA chips include Xilinx, Altera, lattice and MICROSEMI, of which the first two have a total market share of 88%.   Field programmable gate array FPGA is a semiconductor device composed of configurable logic block (CLB) matrix connected through programmable interconnection. FPGA can be reprogrammed according to the required application or functional requirements after manufacturing.   This feature is the key to the difference between FPGA and ASIC. You can customize FPGA devices for specific design tasks. Although there are also one-time programmable (OTP) FPGAs on the market, most of them are based on SRAM and can be reprogrammed as the design evolves.   Field programmable gate array FPGA has a very mature and wide range of applications in the aerospace, military, telecommunications fields. Taking the telecommunication field as an example, in the stage of all-in-one telecommunication equipment, FPGA is applied to network protocol parsing and interface conversion because of its programming flexibility and high performance. In the nfv scenario, FPGA based on the general server and hypervisor can achieve a 5-fold performance improvement of the network element data plane, and can be managed and arranged by the openstack cyborg hardware acceleration framework.   In terms of chip design, we need to focus on rationality in algorithm design to ensure the final completion effect of the project, and put forward a solution to the problem according to the actual situation of the project, so as to improve the operation efficiency of FPGA. After the algorithm is determined, the module should be constructed reasonably to facilitate the later code design.   In the code design, we can use the pre designed code to improve work efficiency and reliability. Write the test platform, carry out the code simulation test and board debugging, and complete the whole design process. Unlike ASIC, FPGA has a short development cycle. It can change the hardware structure in combination with the design requirements. When the communication protocol is immature, it can help enterprises quickly launch new products and meet the needs of non-standard interface development.

What is the application scope of DSP digital signal processor?

  DSP digital signal processor is a processor composed of large-scale or very large-scale integrated circuit chips, which is used to complete a certain signal processing task. It is gradually developed to meet the needs of high-speed real-time signal processing tasks. With the development of integrated circuit technology and digital signal processing algorithm, the implementation method of digital signal processor is also changing, and the processing function is constantly improved and expanded.   Before the emergence of DSP digital signal processor chips, digital signal processing can only be completed by microprocessors. However, due to the slow processing speed of microprocessors, they can not meet the high-speed real-time requirements of increasing amount of information. Subsequently, the emergence of DSP chip meets these needs, and the application field has become extensive.   Digital signal processor is not only limited to the audio and video level, it is widely used in communication and information systems, signal and information processing, automatic control, radar, military, aerospace, medical, household appliances and many other fields.   In the past, general microprocessors were used to complete a large number of digital signal processing operations, which was slow and difficult to meet the actual needs; Using bit chip microprocessors and fast parallel multipliers at the same time was once an effective way to realize digital signal processing, but this method has many devices, complex logic design and program design, large power consumption and high price.   The emergence of digital signal processor solves the above problems well. DSP can quickly realize the signal acquisition, transformation, filtering, estimation, enhancement, compression, recognition and other processing, in order to get the signal form that meets people's needs.   Digital signal processor DSP enhances the performance and availability of the vehicle host, improves the audio and video quality, provides more flexibility and faster design cycle. With the development of technology, it is believed that more auditory and visual effects can be provided in the future, making the on-board host become a high-tech information and entertainment center in the car.

How to realize the frequency synchronization of crystal oscillator?

  Crystal oscillators can help electronic systems provide frequencies for synchronous operation, as frequency references or to achieve accurate timing.   In microprocessor-based systems, there are several different frequency signals used to execute instructions, move data into and out of memory, and external communication interfaces.   A simple embedded controller may have a clock frequency of several MHz, while microprocessors in personal computers usually expect an input frequency of 15 MHz. This will multiply internally to provide the frequency of the CPU and other subsystems. Other components in the system may have their own frequency requirements.   In addition to providing the basic requirements of the specified frequency, the oscillator may have to meet other requirements depending on the application requirements of the product.   For example, many product applications require extremely precisely defined frequencies. This is particularly important for systems that need to communicate with other devices through serial or wireless interfaces. Accuracy is usually measured in parts per million (PPM).   At the same time, the trimming circuit can be based on resistance capacitance (RC) or inductance capacitance (LC) networks. These devices are relatively simple and can change the frequency in a wide range. However, designing an accurate RC oscillator or LC oscillator requires the use of expensive precise components. Even so, they cannot meet the highest accuracy and stability required by many product applications.   Crystal oscillators (usually quartz) can also be used as resonant components. Cut the crystal into two parallel crystal planes and deposit metal contacts on them. Quartz has piezoelectric effect, which means that when the crystal is placed under pressure, voltage will be generated on its crystal surface. On the contrary, when voltage is applied to the crystal, the crystal will also change its shape.