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    What are the two stages of frame rate control?

    • Pre-encoding stage. This stage calculates QP for each frame, and the calculation method is different for different frame types. Since the B frame is not used as a reference frame, its QP is obtained from the QP of the adjacent P frame by linear interpolation of simple and large. While the P frame is used as a reference frame, its QP needs to be calculated accurately.
    • Post-encoding stage. There are three essential tasks in this stage two: updating the parameters in the linear prediction mode, updating the parameters of the quadratic rate-distortion model and determining the number of frame skips}j. In order to avoid buffer overflow, the fullness of the buffer is judged. If the fullness of the current frame stream exceeds a certain threshold (such as 80%) after the current frame stream is sent to the buffer, the next frame will be skipped and not encoded.

    What is a surface acoustic wave touch screen?

    Surface acoustic waves are a type of ultrasonic waves, which are mechanical energy waves that propagate shallowly on the surface of a medium (such as glass). Surface acoustic wave performance is stable, easy to analyze, and has very sharp frequency characteristics in the process of shear wave transmission. 
    The touch screen part of the surface acoustic wave touch screen can be a flat, spherical or cylindrical glass plate installed in front of the CRT, LED, LCD or plasma display screen. This glass plate is just a pure tempered glass without any film or overlay. The surface acoustic wave touch screen is very stable and is not affected by environmental factors such as temperature and humidity. Long life (about 50 million touches), high light transmittance and clarity, no color distortion and drift. No need for calibration after installation, excellent scratch resistance, can withstand all kinds of rough touch, most suitable for use in public places. 
    The surface acoustic wave touch screen directly adopts the rectangular coordinate system, the data conversion is distortion-free, and the precision is extremely high, up to 4096 × 4096 pixels. Due to the limitation of its working principle, the surface of the surface acoustic wave touch screen must be kept clean. It will be affected by dust and oil pollution during use, and regular cleaning and maintenance work is required.

    What clock input modes can each programmable register work with?

    • Global clock signal.
    • The global clock signal is enabled by an active-high clock signal.
    • Implement an array clock with product terms.

    Analysis of the heat dissipation function of the heat sink, what characteristics can be found?

    • When the wafer substrate operates at clock rates of 100MHz or more, large amounts of common-mode current are generated within the device package.
    • Decoupling capacitors only remove differential mode RF currents between power and ground.
    • Some ceramic packaged devices have pads on top for further differential mode decoupling. Decoupling capacitors can reduce ground reflections and board-level induced noise voltages that occur when switching devices operate at maximum capacitive loading on all component leads.
    • The die (or substrate) inside the package is placed closer to the package case (dimension x) than to the package base (dimension l,). Therefore, the heat sink is placed on top of the component package so that the metal plate is physically closer to the die (x) in the package than the ground plane (y).
    • When a metal heat sink is placed on top of the component, it provides a zero volt reference (image plane) closer to the die than the image plane on the PCB. A tighter common mode RF coupling is then created between the chip substrate and the heat sink than the chip substrate and the first reference plane of the PCB.
    • The common-mode coupling that occurs on the heat sink turns this thermodynamically designed structure into a dipole antenna that radiates to free space very efficiently.

    What are the two ways to design an interface?

    One is to generate ui files through Qtdesigner T tool design, and convert the corresponding XML code into . h file; another is to complete the design of the corresponding interface by writing your own code, and you can make multiple forms by writing multiple form classes. By modifying the corresponding . cpp files and . h file to complete the functions you need.

    What are the main components of the RF interface?

    1. Receiving part
    2. Transmitting part
    3. Common circuit part

    What is the title of IS0/IEC l4443 international standard?

    The identification card is a contactless integrated circuit card proximity card.
    The standard is divided into 4 parts, and the details of each part are introduced in Chapter 4.

    Which power saving mode does LPC2114/2124/2210/2220/2212/2214 support?

    The LPC2114/2124/2210/2220/2212/2214 supports two power-saving modes: idle mode and power-down mode.
    ① In idle mode, the processor stops executing instructions.
    ② In power-down mode, the oscillator is turned off, so that the chip does not have any internal clock.

    What are the characteristics of chemical sensors?

    The chemical sensor has the characteristics of simple structure, less sampling, fast measurement speed and high sensitivity. Especially with the development of semiconductor integration technology, the sensor can be miniaturized, so small that it can be inserted into the cell for measurement. It can also be combined with a computer to realize the intelligence of the sensor. In addition, chemical sensors are also important signal converters for enzymes, immune and microbial sensors. Therefore, it occupies a very important position in medical sensors.

    What are the important properties of circularly polarized waves?

    Circularly polarized waves have the following important properties.
    (1) A circularly polarized wave is an instantaneous rotating field of equal amplitude, that is, looking along its propagation direction, the endpoint trajectory of the instantaneous electric field vector of the wave is a circle. If the instantaneous electric field vector rotates in the direction of the left-handed spiral along the propagation direction, it is called a left-handed circularly polarized wave; if it rotates in a right-handed spiral along the propagation direction, it is called a right-handed circularly polarized wave.
    (2) A circularly polarized wave can be decomposed into two equal-amplitude linearly polarized waves that are orthogonal in space and time. Therefore, the basic principle of realizing a circularly polarized antenna is to generate two spatially orthogonal linearly polarized electric field components, and to make the two equal in amplitude and 90 degrees out of phase.
    (3) Any polarized wave can be decomposed into two circularly polarized waves with opposite handedness. For example, a linearly polarized wave can be decomposed into two circularly polarized waves with opposite handedness and equal amplitude. Therefore, the incoming wave of any polarization can be received by the circularly polarized wave antenna; conversely, the circularly polarized wave radiated by the circularly polarized antenna can also be received by the antenna of any polarization. in some applications of RFID. For example, in an airport baggage handling system, in order to provide high directivity and narrow beams within a specific range to better identify objects, the reader antenna is generally designed to be linearly polarized. According to the requirements of the polarization characteristics of the tag antenna, the circular polarization of the tag antenna must be realized.
    (4) If the antenna radiates left-handed circularly polarized waves, it can only receive left-handed circularly polarized waves and cannot receive right-handed circularly polarized waves; on the contrary, if the antenna radiates right-handed circularly polarized waves, it can only receive right-handed circularly polarized waves. polarized waves and cannot receive left-handed circularly polarized waves. This is called the handed orthogonality of a circularly polarized antenna. In the application of RFID system, attention should be paid to the polarization characteristics of the antenna.
    (5) When a circularly polarized wave is incident on a symmetrical target (such as a plane, spherical, etc.), the reflected wave will become anti-handed. That is, left-handed to right-handed, right-handed to left-handed. According to this property, the radar working with circularly polarized wave has the ability to suppress the interference of rain and fog. Since different objects have different reflection characteristics of waves, the object’s characteristics can be obtained by analyzing the received reflected waves by irradiating the object with circularly polarized waves. Therefore, circularly polarized antennas are also widely used in target recognition.


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