AN2731 Freescale Semiconductor / Motorola, AN2731 Datasheet
AN2731
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AN2731 Summary of contents
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... Freescale Semiconductor, Inc., 2004. All rights reserved. Rev. 1.2, 11/2004 Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Antenna Terms . . . . . . . . . . . . . . . . . . . . . . . . 2 3 Basic Antenna Theory . . . . . . . . . . . . . . . . . . 2 4 Impedance Matching . . . . . . . . . . . . . . . . . . . 6 5 Miniaturization Trade-offs . . . . . . . . . . . . . . 13 6 Potential Issues . . . . . . . . . . . . . . . . . . . . . . 14 7 Recommended Antenna Designs . . . . . . . . 14 8 Design Examples . . . . . . . . . . . . . . . . . . . . . 16 AN2731 ...
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Antenna Terms 2 Antenna Terms Antenna Gain A measure of how well the antenna radiates the RF power in a given direction, compared to a reference antenna, such as a dipole or an isotropic radiator. The gain is usually measured ...
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Basic Antenna Variations 3.1.1 3.1.1 Dipole Antenna The dipole is one of the most basic antennas. The dipole is a straight piece of wire cut in the center and fed with a balanced generator or transmission line. As previously ...
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Basic Antenna Theory Figure 2. Dipole Shapes to Improve Omnidirectional Characteristics To reduce the size of the dipole, several options exist: • Replacing some of the wire length with loading coils • Bending the dipole ends back on the dipole ...
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In general, the smaller the antenna, the lower the radiation resistance and the lower the efficiency. The antenna should also be removed somewhat from the ground plane, preferably at least ¼ wavelength (3 cm) but not less than 1 cm. ...
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Impedance Matching 4 Impedance Matching For heavily loaded antennas and antennas close to ground, the radiation resistance may deviate considerably from 50 Ohms which causes a poor match. An Inductive/Capacitive (LC) matching network may be employed, but better efficiency is ...
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All the different dipole types, loading techniques, and feeding networks total enormous amount of possible combinations, each with its own advantages and disadvantages. Selection of the correct design for your application is best found using case-by-case assessment. ...
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Impedance Matching The ground plane should be a reasonably sized area compared to the antenna, and should be reasonably continuous monopole is used on a very small PCB, perhaps even with only a small area of copper, efficiency ...
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The Helix If a quarter wavelength is coiled up, a very compact antenna can be made which still has reasonable efficiency. Some experimentation may be required to find resonance, because the length of the wire is not exactly related ...
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Impedance Matching 4.2 Loop Antennas Loop antennas can be divided in two groups: 1. Half-wave antennas 2. Full-wave antennas The term wave refers to the approximate circumference of the loop. 4.2.1 Half-wave Loop The half wave loop consists of a ...
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Slot Antennas Slot antennas are used extensively in aircraft and radar applications. The basic slot antenna is a half wave slot cut in a conducting sheet of metal. The feed point is across the center of the slot and ...
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Impedance Matching Figure 10. Half-wave and Quarter-wave Slot Antennas 4.2.4 Patch Antennas Patch antennas are a group of antennas with a very low profile and are capable of working very close to a ground plane. However, they require a fair ...
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Because the balun is a discrete device bidirectional. The balanced port can be both input or output. Several discrete circuits are available that perform as baluns. Most of them are sensitive to input and ...
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Potential Issues 6 Potential Issues Numerous things can go wrong with an antenna design. The following list provides a few do’s and don’t’s which may server as a good checklist in a final design. Many of these items seem obvious ...
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Feedpoint impedance of 2-300 Ohm • Easily loaded to smaller size, with PCB or lumped loading • Provide a DC feed to the TX port • Easy to implement in FR-4 PCB Of the different antenna types, the following ...
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Design Examples 8 Design Examples The following section shows a series of design examples. Each of these has been tuned for a particular design cut-and-paste approach will not necessarily ensure optimum performance. However, these designs are a good ...
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Figure 14. F-Antenna Radiation Pattern (For Antennas as Shown in Figures 11 and 12) Freescale Semiconductor Figure 13. F Antenna 3 EVK Horiz ontal PCB R adiation Pattern -10 -15 -20 -25 -30 Vert. polarization (dBi) Hor. ...
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Design Examples Figure 15. F-Antenna Radiation Pattern (Rotated 90 Degrees For Antennas as Shown in Figures 11 and 12) The following figure shows a typical plot of the return loss and bandwidth obtainable with an F-antenna. A slight ripple is ...
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Chip Antennas Numerous chip antenna designs exist recommended to carefully follow the manufacturers recommendations regarding ground, keep-out areas, etc. Only one example is shown, indicating that some tuning will be necessary. The chip antenna, AT9520-B2R4HAAT from ACX, ...
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Design Examples Total Length = 55 mm (Tip-to-Tip) Center part = 30 mm (Length) Track = 2.5 mm Bending angle = 45 degrees .522”/13.27mm .582”/14.79mm 20 Figure 18. Single Bend Dipole 1.22”/30.99mm .84”/21.29mm Figure 19. Dipole Antenna With Dimensions Compact ...
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Figure 21. Antenna Pattern for Dipole Antenna in Position Shown ( Freescale Semiconductor Figure 20. VSWR Plot of Dipole Antenna Compact Integrated Antennas, Rev. 1.2 Design Examples 21 ...
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Design Examples Figure 22. Antenna Pattern for Dipole Antenna in Position Shown ( Compact Integrated Antennas, Rev. 1.2 Freescale Semiconductor ...
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Figure 23. Antenna Pattern for Dipole Antenna in Position Shown ( Freescale Semiconductor Compact Integrated Antennas, Rev. 1.2 Design Examples 23 ...
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Design Examples 8.4 Loop Antennas An experimental full-wave loop, loaded with chip inductors, is shown in the following figure. Gain is about –3 dBm, which is much better than a chip antenna of comparable performance. 8.5 Slot Antenna An experimental ...
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Patch Antenna Two patch antennas, originally designed as diversity antennas, are shown in the following figures. The types have no ground beneath them, and have fairly high bandwidths. Other types, which sit on top of a ground plane, can ...
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... Home Page: http:// .com Freescale AN2731 Rev. 1.2 11/2004 Information in this document is provided solely to enable system and software implementers to use Freescale Semiconductor products. There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document ...