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  • How do antennas actually work
    How do antennas actually work 2021-09-16
    How do antennas actually work? 2021-9-16 www.whwireless.com Estimated 8 minutes to finish reading Antennas are widely used in telecommunications, for example in radio communications, radio and television. Antennas pick up electromagnetic waves and convert them into electrical signals, or pick up electrical signals and radiate them as electromagnetic waves. In this article, let's take a look at the science behind antennas. If we have an electrical signal, how do we convert it into an electromagnetic wave? You probably have a simple answer in mind: that is to use a closed wire which, with the help of the principle of electromagnetic induction, will be able to generate a fluctuating magnetic field and an electric field around it. However, this fluctuating field around the source is of no use in the transmission of the signal. Here the electromagnetic field does not propagate, it just fluctuates. In an antenna, the electromagnetic waves around the source need to be separated from the source and they should propagate. Before we look at how to make an antenna, let's understand the physics of an antenna. Wave separation considers the placement of a positive charge and a negative charge. This pair of charges arranged very close together is called a dipole, and they obviously produce an electric field as shown in the diagram. Assuming that these charges are as shown, oscillating at the midpoint of their path, the velocity will reach a maximum and at the end of their path, the velocity will be zero, and due to the change in velocity, the charged particles will experience successive accelerations and decelerations. The challenge now is to find out how to make the electromagnetic field vary due to this motion. Let us focus on just one electric field line that expands and deforms in front of the wave that forms at time zero, after a time period of one-eighth. As shown in the diagram. You may be surprised to expect a simple electric field to be shown at this location as shown below. Why does the electric field expand to form an electric field like this one? It is because accelerating or decelerating charges produce some electric field memory effect and the old electric field does not easily adapt to the new electric field. It will take us some time to understand this memory effect electric field or the accelerating or decelerating charges produced by the kink. We will discuss this interesting topic in more detail in another article. If we continue the analysis in the same way, we can see that in a quarter time period the wave front meets at a point where. After this, the wave fronts separate and propagate. Note that this changing electric field automatically generates a magnetic field perpendicular to his change. If you plot the variation of the electric field strength with distance, you can see that the wave propagation is intrinsically sinusoidal. It is interesting to note that the resulting propagation wavelength is exactly twice the length of the dipole. T...
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  • The next generation of wireless technology - Wi-Fi 7 - how powerful is it?
    The next generation of wireless technology - Wi-Fi 7 - how powerful is it? 2021-09-10
    The next generation of wireless technology - Wi-Fi 7 - how powerful is it? 2021-9-10 www.whwireless.com  Ken Mobile will have faster speeds and lower latency. The current Wi-Fi 6 and even Wi-Fi 5 technology introduces many of the technologies used in mobile networks, also known as 4G 5G, such as beam focussing, a technology that greatly improves the directionality of the signals sent by the router. By interfering with multiple antennas the signal is directed to the terminal, significantly solving the previous problem of omnidirectional antenna coverage distances. The "main flap" in the middle, created by beam focussing, is highly directional and has a much longer range.  There is also the introduction of MIMO (Multiple In Multiple Out) technology in Wi-Fi 5, which gives mobile devices a huge increase in data throughput. The latest Wi-Fi protocol is Wi-Fi6e and there are only a handful of routers and terminals that support this protocol. Personally, I think Wi-Fi6e may not catch fire in China because the Ministry of Industry and Information Technology may not approve Wi-Fi6e. The main reason for this is that although Wi-Fi6e provides more frequency bands, which effectively improves device band capacity and transmission speed, it conflicts with some of the frequency bands of the 5G network   currently under construction in China. However, individuals are only limited and perhaps Wi-Fi6e has the ability to solve this problem.   The protocol specification for Wi-Fi7 is presumably still being developed right now, and it will be a long time before the actual launch and the corresponding wireless terminals are launched. However, now our broadband bandwidth Wi-Fi5 is in fact fully satisfied, as long as it is not a special demand Wi-Fi6 and 6e are not particularly necessary now. Except of course if there are special LAN transmission needs or scenarios that require new features.   Personally, I think that Wi-Fi7 will have a higher frequency than the previous generation, which means that it can carry more bandwidth, although the signal coverage capability will definitely be reduced, which can be referred to 5G base stations. The 5G speed is now double that of 4G to a large extent due to the significant increase in communication frequency, which also leads to a decrease in signal coverage and an increasing number of base stations. Wi-Fi technology has been developed for over twenty years since it came out in the late 1990s and there have been numerous technological enhancements. Now Wi-Fi is not only used for internet access, there are also many transmission technologies based on Wi-Fi featured LAN, such as Apple's AirPlay, airdrop, etc. Huawei's Internet of Everything and collaboration between devices also rely on the huge bandwidth of current Wi-Fi technology. www.whwireless.com  
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  • Comparison of multiple GPS navigation systems, signal and spectrum distribution
    Comparison of multiple GPS navigation systems, signal and spectrum distribution 2021-08-11
    Comparison of multiple GPS navigation systems, signal and spectrum distribution 2021-08-11 whwireless GLONASS system The Russian GLONASS system is similar to the US GPS system, and is also a global positioning system by satellite. The system has 24 satellites distributed in 3 orbits with 8 satellites in each orbit and an orbital altitude of 19,100 km. Comparison of multiple GPS systems, signal and spectrum distribution Figure 1 GLONASS satellite constellation The GLONASS system also has two PRN codes, military and civilian, with positioning accuracy comparable to that of the GPS system. The C/A code rate is 511 kHz, the code length 511 and the code period 1 ms, while the P code rate is 5.11 MHz. The difference is that all GLONASS satellites use the same PRN code, which is differentiated by frequency division multiple access. The frequencies of the satellites are Comparison of multiple GPS navigation systems, signal and spectrum distribution k = 1, 2, 3 ......, 24 are the satellite numbers. The spectrum distribution of GPS and GLONASS signals in the L1 band is shown in Figure 2. Comparison of multiple GPS navigation systems, signal and spectrum distribution Figure 2 Spectrum distribution of GPS and GLONASS signals in the L1 band The GLONASS signal has a ground strength of -161 to -155.2 dBW. The initial satellite life of the GLONASS system was too short and the lack of funding due to the collapse of the Soviet Union meant that by July 2005 there were only 10 available satellites in the system. The GLONASS system has now also been modernised and upgraded with the launch of new long-life satellites and the addition of L2 C/A signals. Comparison of multiple GPS navigation systems, signal and spectrum distribution GALILEO The GALILEO system, launched by the European Union, consists of 30 satellites, evenly distributed over three orbits, with an altitude of 23,000 km, an orbital period of 14h 4min and an orbital inclination of 56°. and multi-service. The GALILEO system consists of 10 signals located in 4 frequency bands. (1) E5 band: frequency range 1164~1215 MHz, containing two bands E5a and E5b, each containing two signals, modulation mode AltBOC(15, 10), code rate 10.23 MHz, minimum signal reception power -155dBW. this band mainly provides Open Service (OS) and Safety-of-Life (SOL) services. (2) E6 band: The frequency range 1215-1300 MHz contains 3 signals, modulated by BPSK, with a code rate of 5.115 MHz and a minimum received power of -155 dBW. Service (CS). (3) E2-L1-E1: The frequency range of 1559-1591 MHz contains three signals, with the centre frequency of 1575.42 MHz being used for GPS compatibility. The E2 band covers 1559 to 1563 MHz and provides mainly public licensed services. Comparison of multiple GPS navigation systems, signal and spectrum distribution Figure 3 GALILEO signal spectrum distribution The spectrum distribution of GALILEO system signals is shown in Figure 3. Comparison of multiple GPS systems, signal and spectrum distr...
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  • About 5G antenna OTA test method analysis and application
    About 5G antenna OTA test method analysis and application 2021-07-10
    About 5G antenna OTA test method analysis and application Estimated 8 minutes to finish reading www.whwireless.com Test methods of existing antennas With the deepening of electromagnetic research and the development of electronic technology, the development and application of antennas have penetrated into many fields such as navigation, communication, electronic countermeasures and radar, etc. Multi-beam antennas can form multiple mutually independent transmit or receive beams simultaneously or in time through phased arrays to achieve flexible control of beam shape and rapid switching of beam direction. At present, the most widely used phased array antenna test methods are mainly three: far-field method, near-field method and tight field method. 1、Far field test scheme Far-field test is the most direct test method, when the test distance is far enough, the human wave in the receiving surface is close to the plane wave. The diagram below shows the far-field test system, where the part under test can be rotated 360° in the vertical and horizontal planes, and the test probe position is fixed and can be polarised and rotated. The test system can test the beam assignment directional map and EIRP (Effective Isotropic Radiated Power), EVM (Error Vector Magnitude), occupied bandwidth, EIS (Effective Isotropic Sensitive), and EIS (Effective Isotropic Sensitive) of the 5G base station antenna. Isotropic Sensitive, effective omnidirectional sensitivity) and other RF radiation indicators. 2、Tight field test programme The tight field test is a far-field test method, which can use a reflector or lens to convert the spherical wave from the feed source at the focal point into a plane wave, so as to achieve the far-field test in a limited physical space. The figure below shows a parabolic single reflector constrained field test system that can test the beam assignment direction map and EIRP, EVM, occupied bandwidth, ACLR (Adjacent Channel LeakagePower ration), EIS, ACS (Adjacent Channel Selectivity) of a 5G base station antenna. Channel Selectivity) and other RF radiation indicators. 3、Near-field test solution Multi-probe spherical near-field test solution Near-field test in the measured antenna radiation near-field area to collect the amplitude and phase information, and then through the near and far field conversion algorithm to collect data into the far field direction map. The multi-probe spherical near-field test system is shown in the diagram below, where a large number of probes are arranged along the circumference of the radiated near-field of the DUT, and the DUT only needs to be rotated by 180 degrees to capture data from the entire radiated sphere. The system is capable of testing the beam assignment direction of a 5G base station antenna in CW (Continuous Wave) mode.   Single probe near-field test system Single probe near-field testing is less efficient than multi-probe spherical near-field testing, but it is simpler and requires less space. The ...
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