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  • Ten Daily Electronic Common Sense-Section 79

    What are the specific frequency bands for the RFID system?

    Low frequency, the frequency range is 30 kHz ~ 300 kHz, the working frequency band is lower than 135 kHz, and 125 kHz is commonly used.
    High frequency, the frequency range is 3MHz ~ 30 MHz, and the operating frequency is l3.56 MHz ± 7 kHz.
    Ultra-high frequency (UHF, the frequency range is 300 MHz ~ 3 GHz). Operating frequencies are 433 MHz, 866 MHz to 960 MHz and 2.45 GHz.
    Ultra-high frequency (SHF, the frequency range is 3 GHz to 30 GHz, the operating frequency is 5.8 GHz and 24 GHz, but 24 GHz is basically not used at present.

    What is a carbon film Resistors? The parameters of the carbon film Resistors:

    Carbon film resistors are one of the film resistors (FilmResistors). It is made by using high temperature vacuum coating technology to closely attach carbon to the surface of the porcelain rod to form a carbon film, then add appropriate joints to cut, and coat the surface with epoxy resin for sealing protection. Because it is a lead type resistor, it is convenient for manual installation and maintenance, and it is also the cheapest among lead resistors. Nowadays, it is mostly used in some low-value low-end products such as power supplies and adapters or in early designed products. Characteristics of carbon film resistors Working temperature range: -55℃~155℃ accuracy, 2% 5% resistance range, 1Ω~10MΩ nominal resistance. E-96 has high limit voltage, excellent long-term stability and low price. Packing methods include tape and bulk.

    What are the features of SignalTapII’s features?

    1. It is an FPGA board-level debugging tool. Functions like a logic analyzer.
    2. Real-time display of the signals inside the FPGA. Easily find faulty signals.
    3. No need to purchase separately, it is integrated in Quartus II, easy to use, and does not change the original design.
    4. Under the premise of not affecting the original design, the logic value of the observation signal is stored in the remaining RAM in the FPGA chip, and then transmitted to the computer through JTAG to display the waveform.
    5. The sampling depth depends on the remaining RAM.

    What are the functions implemented by the MAC sublayer?

    The functions implemented by the MAC sublayer include: mapping between logical channels and transport channels, and selecting an appropriate transport format for each transport channel. Priority processing between UE data streams, priority processing using dynamic pre-scheduling method between UEs. Priority handling between data streams of several users on DSCH and FACH, and the identity of the UE on the common transport channel. The higher layer PDUs are multiplexed into transport blocks transmitted to the physical layer through the transport channel, and the transport blocks from the physical layer are multiplexed into higher layer PDUs through the transport channel. Traffic detection, dynamic transmission channel type switching. Transparent RLC encryption, access service level selection.

    What are the advantages of RFID?

    RFID can identify a single very specific object whereas barcode can only identify the category of the object
    RFID uses radio frequency and can read data through external materials, while barcodes rely on lasers to read external data.
    RFID can identify multiple objects at the same time (ie, has anti-collision capability), while barcodes can only be read one by one.
    RFID electronic tags can store a large amount of information and can be rewritten many times.
    RFID is easy to build a network application environment, and for commodity goods, a so-called logistics network can be built.

    What is network coding?

    The most basic idea of network coding is to combine routing and coding, which are the core operations of the network layer and the physical layer respectively. This mechanism is to allow the intermediate nodes of the data flow to encode the data flow.
    Network coding is the basis for many efficient wireless network transport mechanisms. The network coding can greatly improve the spectral reuse rate, and the finite-length random linear codes in the Galois Field can make the network coding be used efficiently in practice.

    What are the applications of the adder?

    • Binary parallel adder/subtractor
    • 8421-BCD code is converted into the remaining 3 code circuit

    What are the characteristics of the S3C2440A?

    2 V core power supply, 1. 8 V/2. 5 V/3. 3 V memory power supply, 3. 3 V external I/O power supply with 16 KB I-Cache and 16KB DCache/MMU microprocessor; External memory controller (SDRAM control and chip select logic); LCD controller (maximum support 4K color STN and 256K color TFT) provides 1-channel LCD dedicated DMA; 4-channel DMA and external request pins; 4-channel DMA and external Request pin; 3-channel UARTCIrDA1.0, 64-byte Tx FIFO, and 64-byte Rx FIFO); 2-channel SPI; 1-channel IIC-BUS interface (multi-master support); 1-channel IIS-BUS audio codec interface ;AC’97 Decoder Interface; Compatible with SD Host Interface Protocol Version 1.0 and MMC Card Protocol Version 2.11 Compatible; 2-Port USB Host/I-Port USB Device (Version 1.1); 4-Channel PWM Timer and 1-Channel Internal Timer/Watch Watchdog timer; 8-channel 10-bit ADC and touch screen interface; RTC with calendar function; camera interface (maximum 4096 × 4096 pixel input support, 2048 × 2048 pixel input, support zoom); 130 general-purpose I/ O port and 24-channel external interrupt source; with normal, slow, idle and power-down modes; with PLL on-chip clock generator.

    How to reduce the noise impact and improve the detection accuracy?

    1. Average multiple times. Due to the randomness of noise, the influence of noise can be reduced by averaging multiple samples. Multiple sampling and averaging of the signal can be conveniently accomplished by a microcomputer.
    2. Curve fitting method. The output signal is synchronously sampled by microcomputer control, and the obtained data is fitted with polynomial curve by the least square method, and then the peak point coordinate of the fitting curve is obtained as the dark spot position of the diffraction pattern to calculate the diameter of the wire to be measured. The curve fitting method can greatly reduce the influence of random factors, so that the measurement accuracy can be significantly improved, and another obvious advantage of the curve fitting method is that the resolution is not limited by the size of the array element.
    3. Multiple dark spot position fitting method. Since the linear optoelectronic device is long, several dark streaks can be received in one sampling, so the measured distance between the peaks of multiple dark streaks can be processed by the least square method, and finally the diameter can be calculated. This method can also effectively reduce the influence of random noise.
    4. Reduce the operating temperature of the device to reduce the noise of the device itself.

    What is the PTN technology in terms of network planning and construction?

    The core layer, aggregation layer and access layer can organize ring network, chain network, mesh network, etc.


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