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Antennas have become an integral part of modern technology, serving as crucial communication components for various mainstream devices such as smartphones, IoT devices, and security systems. This prevalence underscores the significance of radio frequency (RF) engineering and design, making it a captivating and influential field. In this context, my objective is to provide readers with a foundational understanding of antennas – their fundamental principles, operation, and the process of constructing a 2.4 GHz antenna design.Before delving into the details, it's important to note that while I am not an RF expert, I bring forth years of practical experience that can guide individuals in initiating and advancing their projects effectively.
What is Antenna Overview
While the main focus of this article centers around PCB antennas operating at 2.4 GHz, a foundational understanding of antennas can greatly benefit beginners. However, if you're a professional seeking a more advanced insight into PCB antennas, feel free to skip this section.To grasp antennas more comprehensively, a brief exploration of impedance matching and resonant circuits is essential. To achieve optimal power transfer, the source impedance should ideally match the load impedance.An antenna essentially constitutes a metallic structure, often composed of wires, serving as a means to convert high-frequency electrical currents into electromagnetic waves and vice versa. In essence, it functions as a specialized transducer that transforms high-frequency electrical current into electromagnetic waves.For an antenna to efficiently transmit signals, it must effectively match the transmission line and the load impedance. The length of the wire, its dielectric properties, and the frequency play crucial roles in its function. This wire acts as an impedance-matching transmission line, a topic we'll delve into further in this article.The antenna also operates as a resonant circuit. This means it possesses the capacity to transform energy from electrostatic to electromagnetic, and with proper impedance matching, the energy is transferred and radiated into the surrounding space, akin to how a transformer shifts energy from primary to secondary.While the above overview simplifies the complexities of RF transmission, it serves as the foundation for further discussions.In antennas, wavelength, frequency, and antenna length are intertwined. Let's elucidate these parameters with a basic example.The antenna's length and configuration are interconnected with the wavelength of the transmitting frequency. Specifically, the mechanical length is inversely proportional to the frequency's value.As we're aware, the formula is:T = 1 / fwhere T represents time andf signifies frequency.Consequently, for an antenna operating at 50 MHz,t = 1 / f = 0.2 μs,Wavelength (λ) = C / f = 3 * 10^8 / 50 * 10^6 = 6 m,with C denoting the speed of light.For a quarter-wavelength antenna, it becomes a constant λ/4.The simple example provided illustrates how to compute wavelength for a specific frequency.Applying the same calculations for 2.45 GHz yields an antenna length of 23 mm.With these foundational concepts in place, we can now delve into the main focus of this blog: PCB design.Before proceeding, it's important to clarify that I won't be delving into the intricate details of every facet of PCB antenna design step by step. My expertise, tools, and measurements don't extend to such exhaustive explanations.Instead, I'll explore core concepts, share best practices, and offer key considerations. With that said, let's delve into the design process!
Antenna Schematic
In this phase, our focus is on designing a 2.4 GHz antenna tailored for the ESP8255 Mini board. Below, you'll find the circuit diagram for this endeavor. In the upcoming article, we'll take the schematic and craft an entire PCB based on it.To ensure the accuracy of our schematic, we'll leverage the ESP8285 design guide thoughtfully provided by Espressif. Upon searching, I located the hardware design guide for the ESP8285, which offers an in-depth resource for crafting a comprehensive hardware design.Within these hardware design guidelines, I'd like to emphasize a few critical design prerequisites, specifically concerning the analog and digital power supplies for the ESP. While these two power supply aspects will receive comprehensive exploration when we embark on designing the complete PCB for the ESP8285 board, our current focus remains dedicated to the intricacies of antenna design.
2.4 GHz PCB Antenna Design
The antenna segment offers a toggle feature between a PCB antenna and a whip antenna. In case of contingencies, inductors L3 and L4 are included.Dividing our attention to the PCB, we can distinguish two primary sections: the antenna segment and the crystal oscillator segment. For now, our exclusive focus lies on the antenna component.The most challenging phase of this project involved strategizing the antenna's placement.Initial steps encompassed positioning essential junctions and connectors.Following that, we meticulously positioned the antenna, U.FL connector, programming header, GPIO0 switch, and microcontroller, mirroring the arrangement depicted in the image above.The subsequent task entails configuring the antenna traces. I'll harness Eagle PCB's polygon tool to fulfill this requirement.An imperative aspect to bear in mind prior to routing pertains to maintaining a trace impedance of 50 ohms. This impedance is vital as the trace serves as a high-frequency transmission line. However, the exact 50-ohm value hinges considerably on factors such as dielectric material and board thickness. Hence, a meticulous calculation is in order to ensure accurate trace drawing.For this purpose, we will utilize an online resource called Mantaro.To compute the optimal trace width, input the necessary parameters, all of which are readily available from the manufacturer's documentation.Firstly, I manually input a trace width of 70 mils.Subsequently, the trace thickness is set at 1 ounce, equivalent to 1.4 mils.The third parameter is the dielectric thickness, i.e., the board's thickness, which stands at 39.3701 or 1.6 mm.Lastly, the relative dielectric constant, unique to each manufacturer, is sourced from the manufacturer's specifications.Upon pressing the "calculate" button, the result yielded an impedance of 50 ohms.A noteworthy observation: The dominant factors shaping impedance are trace width (w) and dielectric thickness (h).PR -
The thickness of copper plays a pivotal role in thick copper printed circuit boards. The cost is contingent on the copper's weight, measured in ounces, hence 20 oz thick copper is pricier than 16 oz.Copper finds applications in fume hoods, countertops, stand-up roofs, trim roofs, downspouts, and gutters. It boasts pre-perforated hammered panels.Copper measurements are denoted in ounces by weight. Upon exposure to air, copper develops a bronze hue, influenced by various factors. Its color spectrum ranges from black to green, brown, or intermediate shades. Although many misconstrue this color change as corrosion, it's merely a chemical reaction, unrelated to product lifespan. In fact, copper's durability is enhanced by this reaction.Now, let's delve briefly into the definition of a 20 oz limit PCB.
What is a 20 oz PCB?
A 20oz PCB can be succinctly defined as a thick printed circuit board housing a copper layer with a thickness of 20 ounces. This signifies that the PCB possesses substantial thermal capacity and can accommodate high levels of current flow.To determine the thickness of a 20 oz PCB, one must first understand the dimensions of a 1 oz PCB and then multiply it by 20. A 1 oz PCB measures 1.37 mils or 0.00137 inches in thickness. Accordingly, the thickness of a 20 oz metal core PCB would be 20 times 1.37 mils, equating to 27.4 mils or 0.0274 inches.The integration of heavy copper in circuit boards is a strategic response to the escalating demands for high current and power in various industries such as automotive, military, electric energy, solar energy, and computing.The emergence of 20oz PCBs is poised to supplant archaic metal strips and conventional cable routing methods. This innovative transmission structure not only enhances production efficiency but also curtails system maintenance and wiring expenses.How to make a 20 oz PCB
Manufacturing a 20 oz PCB introduces several challenges compared to conventional methods used for Traditional PCB manufacturing. These complexities encompass processes such as drilling, lamination structures, solder mask application, precise etching, and more. Currently, the production of heavy copper PCBs involves three distinct approaches:Plating:Due to the limited availability of thick copper foil in the market, factories often possess copper foil with a thickness of only 5 oz. Orders requiring copper foil thickness beyond this level typically involve initial processing with 5 oz copper foil, followed by electroplating to achieve the desired thickness.This approach takes into consideration both the overall cost of processing, including the extended electroplating duration and the high production capacity of electroplating equipment. The challenge lies in maintaining uniformity during etching, which directly stems from the uniformity achieved during the electroplating process.Laminated:In this method, a layer of exceptionally heavy copper foil is applied through lamination. While this technique offers improved uniformity in copper thickness compared to electroplating thickening, it still necessitates multiple etching stages.Etching:This technique entails etching both the front and back sides of the copper foil. Initially, one side of the copper foil undergoes etching to create the desired pattern at half-depth. This partially etched pattern is then pressed onto the board before proceeding with lamination. After lamination, the second side of the copper foil undergoes etching, resulting in the removal of remaining copper thickness and substrate. This leaves the initially etched pattern embedded in the substrate. -
Hot-swappable PCB (Printed Circuit Board) is a design that facilitates the easier replacement of mechanical keyboard switches, allowing users to adjust keyboard configurations more conveniently. This article will explore the differences between hot-swappable PCBs and traditional soldered PCBs.For individuals planning to create a mechanical keyboard, one formidable task is soldering the switches. However, the introduction of hot-swappable PCBs provides a convenient solution to this challenge. The PCB, or Printed Circuit Board, serves as the core component of a keyboard, with mechanical switches connected to the PCB through two main methods.One method involves soldering the PCB, using soldering tools and solder to connect the switch to the PCB by threading the switch pins through the holes on the PCB and melting the solder. While this method securely fixes the switch, it requires caution during execution, as the solder may potentially damage the PCB socket and break the switch pins.The alternative, simpler method employs a hot-swappable PCB to install the switch, eliminating the need for soldering tools and solder. This approach is akin to installing PC components or Lego blocks, where the switch pins are pushed into pre-installed sockets. The hot-swappable design offers advantages such as easy operation, no requirement for professional training, and effortless switch replacement.An example of a product featuring a hot-swappable PCB is the Modular Mechanical Keyboard (GMMK), providing convenience for users seeking a straightforward, intuitive, and customizable keyboard experience.When installing switches on a hot-swappable PCB, it is advisable to press them carefully on a soft surface to reduce the risk of pin bending. Similarly, when removing keys, caution is necessary to avoid causing fatal damage to the sockets.It's important to note that while it is theoretically possible to convert a soldered PCB to a hot-swappable PCB, this process also requires the use of soldering tools, presenting challenges for novice users.
Advanced Reading: How to Build Your Own Keyboard PCB