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RF Electronics Chapter 11: Circuit Manufacture Page 368 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. constant become too small so that at these frequencies a low dielectric constant has to be used. Because of their low water absorption characteristics, RT/duroid 58X0 is good for applications in high moisture environments. The LNC of figure 11.5 is located at the focal point of antenna, which is sometimes very hot, sometimes very cold, and sometimes very wet. RT/duroid is thus a good choice for the PCB material. RT/duroid is flexible and thin laminates require care in mounting them securely. RT/duroid is normally brown and the woven glass mat can clearly be seen in figure 11.5. If the dielectric constant of the PTFE composite filling and the glass microfibers are slightly different then small local variations in dielectric constant will occur. Having a random orientation of the microfibers minimises that variation. The glass reinforcing provides an excellent strength and prevents tracks from cracking. Figure 11.5. Ku band (12 GHz) low noise converter (LNC) using RT/duroid (Norsat). The RT/duroid 6000 laminates have a thermal expansion coefficient of the laminate that matches that of copper. This product is ideal for applications in rapidly changing thermal environments such as space. Multilayer boards are possible with this laminate. RT/duroid 6000 is a military specified substrate and thus very expensive. RO3000 and RO3200 (PTFE/Ceramic Laminates) The RO3000® laminates are aimed at a commercial market and are a lot cheaper than the corresponding RT/duroid 6000 laminates. Dielectric constants of 3.0 to 10.2 are available. The temperature coefficient of expansion matches that of copper and FR4 in the X-Y plane, so that multilayer RO3000/FR4 boards can easily be made. RO3003G2 is designed for 77/79 GHz auto radar applications. RO4000 The RO4000 series is a woven glass/ceramic loaded thermoset plastic resin laminate. This is a low cost commercial laminate, which is especially suited for multilayer boards using RO4000 and FR4. The boards have a glass transition temperature (T g ) > 280°C. They can thus be used with conventional PCB processing techniques, such as wave soldering and surface mount techniques. Unlike PTFE based microwave materials, no special through- hole treatments or handling procedures are required. Therefore, RO4000 material circuit processing and assembly costs are comparable to FR4 epoxy/glass laminates. Dielectric constants vary from 2.55 to 6.15. Prepreg sheets of matching dielectric constant are available to produce multilayer boards. The Microstrip filters if figures 7.66, 7.73 and 7.80 to 7.83 have all been made by milling RO4003 substrates. RF Electronics: Design and Simulation 368 www.cadence.com/go/awr

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