Classification of array antennas. WWW.WHWIRELESS.COM Estimated reading time: 15 minutes Array antennas are typically categorized based on the arrangement of their individual units. Linear array: An array of antenna elements arranged along a straight line, with unit spacing that can be equal or unequal. It can be further divided into edge-illuminated arrays and end-illuminated arrays based on the direction of concentrated radiation energy. Planar array: An array of antenna elements arranged at the centers of a single plane. If all the elements in a planar array are arranged in a rectangular grid, it is called a rectangular array; if all the element centers are located on concentric circles or elliptical rings, it is called a circular array. Planar arrays can also have arrays with equal or unequal spacing. Conformal arrays: arrays of antennas that are attached and conform to the shape of the carrier. Cylindrical-surface arrays, spherical-surface arrays, and conical-surface arrays are all examples of conformal arrays. Array antenna unit configuration. Linear antenna array elements: dipole types, monopole types, ring-shaped elements (such as slot antennas), and spiral elements. Diaphragm-type elements: horn antenna elements, open-slot waveguide elements, microstrip patch elements. Hybrid and specialized elements: Yagi-Uda units, logarithmic-periodic dipole array units, medium-resonance antenna units, metasurface/metamaterial units. The theoretical basis of array antennas. ① Principle of Interference and Superposition of Electromagnetic Waves: Array antennas can create radiation characteristics that differ from those of conventional individual antenna units. One of the primary reasons for this is that the electromagnetic waves emitted by multiple coherent radiation units interfere and superimpose on each other in space, with some areas experiencing increased radiation and others experiencing decreased radiation. This results in a redistribution of the constant total radiation energy across different spatial regions. ② The Directional Diagram Product Theorem: Under far-field conditions, the overall normalized directional function of an antenna array composed of multiple identical elements, excited with fixed amplitude and phase, and arranged in fixed geometric positions, can be decomposed as follows: Primary factor F(θ, φ): The directionality of a single unit in free space (including the unit’s polarization and orientation). Array factor AF(θ, φ): This is determined solely by the geometric layout, spacing, excitation amplitude, and phase of the array, and is independent of the specific shape of the elements. That is, the composite overall direction diagram D(θ,φ) = F(θ,φ) · AF(θ,φ). Analysis of array antennas. The analysis of an array antenna involves determining its radiation characteristics under the assumption that four parameters are known (the total number of elements, the spatial distribution of elements, the distribution of excitation amplitudes...

What Is an Antenna? WWW.WHWIRELESS.COM Estimated reading time: 10 minutes An antenna is a device used to transmit and receive radio waves. It is a key component in wireless communication systems, capable of converting high-frequency electrical currents (which flow in transmission lines) into electromagnetic waves (which propagate through free space), and vice versa. Antennas are widely used in radio broadcasting, television, mobile communication, satellite communication, radar systems, and many other fields. Specifically, the functions of an antenna include: Radiating Electromagnetic Waves: On the transmitting side, the antenna converts high-frequency electrical energy generated by electronic equipment into radio waves and radiates them into surrounding space for long-distance transmission. Receiving Electromagnetic Waves: On the receiving side, the antenna captures radio waves from space and converts them into high-frequency electrical currents. These signals can then be processed—such as demodulation, amplification, and decoding—to recover the original information or data. Energy Conversion: The antenna acts as a medium for energy conversion, efficiently transferring energy between guided waves (in transmission lines) and free-space waves (radio waves). Directivity and Polarization: Many antennas have specific directivity and polarization characteristics. Directivity refers to the antenna’s ability to radiate or receive energy more effectively in certain directions than others. Polarization describes the orientation of the electric field of the radio wave emitted or received by the antenna. These properties help optimize communication performance, reduce interference, and extend communication distance. Impedance Matching: To ensure minimal signal reflection and energy loss during transmission, the antenna must be impedance-matched with the transmission line (feed line). This means the antenna’s input impedance should match the characteristic impedance of the line to allow efficient power transfer. Signal Enhancement and Coverage: In some systems, antennas are used to enhance signal strength or extend coverage. For example: In mobile base stations, high-gain antennas can expand signal coverage areas. In satellite communications, directional and high-gain antennas improve signal reception quality and reliability. WWW.WHWIRELESS.COM

Why Impedance Matching Is Necessary WWW.WHWIRELESS.COM Estimated reading time: 15 minutes The biggest difference between radio frequency (RF) and hardware lies in impedance matching, and the reason for impedance matching is the transmission of electromagnetic fields. As we all know, an electromagnetic field is the interaction between an electric field and a magnetic field. The loss in the transmission medium occurs because the electric field causes oscillations in its effect on electrons. The higher the frequency, the more cycles of electromagnetic waves there are in a transmission line of the same length, and the higher the frequency of current changes. As a result, the heat loss generated by oscillations increases, leading to greater losses in the transmission line. At low frequencies, since the wavelength is much longer than the transmission line, the voltage and current on the transmission line in the circuit remain almost unchanged, so the transmission line loss is very small. Meanwhile, if reflection occurs during wave output, the superposition of the reflected wave with the original input wave may lead to a decline in signal quality and also reduce the efficiency of signal transmission. Whether working on hardware or RF systems, the goal is to achieve better signal transmission, and no one wants energy to be lost in the circuit. When the load resistance is equal to the internal resistance of the signal source, the load can obtain the maximum output power. This is what we often refer to as impedance matching.  It is important to note that conjugate matching is for maximum power transmission.    According to the voltage reflection coefficient formula \( \Gamma = \frac{Z_L - Z_0}{Z_L + Z_0} \), \( \Gamma \) is not equal to 0 at this time, meaning there is voltage reflection.    For distortionless matching, the impedances are completely equal, so there is no voltage reflection. However, the load power is not maximized in this case. Return Loss (RL) = \( -20\log|\Gamma| \) Voltage Standing Wave Ratio (VSWR) = \( \frac{1 + |\Gamma|}{1 - |\Gamma|} \) The relationship between standing wave ratio and transmission efficiency is shown in the table below:    Impedance matching involves a rather tedious calculation process. Fortunately, we have the Smith Chart, an essential tool for impedance matching. The Smith Chart is a diagram composed of many intersecting circles. When used correctly, it allows us to obtain the matching impedance of a seemingly complex system without any calculations. The only thing we need to do is read and track data along the circular lines.    ## Smith Chart Method  1. After connecting a series capacitor component, the impedance point moves counterclockwise along the constant-resistance circle it is on.  2. After connecting a shunt capacitor component, the impedance point moves clockwise along the constant-conductance circle it is on.  3. After connecting a series ind...

What is Antenna Gain, and is Higher Always Better? WWW.WHWIRELESS.COM Estimated 10minutes to finish reading Let's discuss what antenna gain is and whether a higher value is always preferable. In reality, it entirely depends on the application of the antenna. Take a flashlight as an example: if you remove the reflector, the light will obviously become less intense. However, if you need an omnidirectional light source to evenly illuminate a room, removing the reflector to allow the light to spread out uniformly is more appropriate. Conversely, if the goal is to create a laser, using a lens to focus all the light from the bulb into a narrow beam is undoubtedly an improvement. But this concentrated beam is unsuitable for lighting up an entire room.   This phenomenon of concentrating light in a specific direction is called directivity, and the degree of concentration is referred to as gain. In the field of antennas, these two concepts behave very similarly to those of a light source. Imagine an antenna radiating energy uniformly in all directions like a candle; this is a non-directional isotropic radiator. Technically, this is defined as 0 dBi, meaning the radiation energy is the same in every direction.   Now, if you place a mirror next to the candle, the mirror will alter the distribution of light energy and give the candle directivity. The mirror will make half of the room darker and the other half brighter because the light is reflected and concentrated in one direction. This approach of "stealing" and redirecting energy from less favorable directions to enhance it in certain directions also applies to antennas.   Therefore, antennas do not generate radio energy; they merely transfer, guide, or concentrate it in a specific direction. This directional characteristic is known as gain. A mirror can redirect half of the candle's energy, making it appear twice as bright in certain directions—equivalent to two candles. In this case, we say the mirror provides a gain of 3 dB because it doubles the energy.   It is important to mention that the unit for measuring antenna gain is the decibel (dB). However, it is typically relative to a reference antenna. Usually, the radiation intensity of an omnidirectional antenna or a half-wave dipole antenna with the same input power in a certain direction is used as the reference value. When using an omnidirectional antenna as the reference, it is denoted as dBi (i - isotropic), and when using a half - wave symmetric dipole antenna as the reference, it is denoted as dBd (d - dipole).   From the definition of antenna gain, we can understand that it refers to the square ratio of the electric field strengths (i.e., the power ratio) produced by an actual antenna and an ideal radiation element at the same point in space under the condition of equal input power. It quantitatively describes the degree to which an antenna concentrates and radiates the input power.   The gain performance of an ante...