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Folded Dipole Antenna for CC25XX(天线设计).pdf

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    Introduction
    Abbreviations
    Description of the folded dipole design
    Implementation of the folded dipole
    Results
    Radiation pattern
    Bandwidth
    Spurious and harmonic emission
    Conclusion
    General Information
    Document History
    Important Notice
    Folded Dipole Antenna for CC25xx Design Note DN004 By Audun Andersen Keywords • CC2500 • CC2550 • CC2510 • CC2511 1 Introduction following products This document describes a folded dipole PCB antenna design that can be used with the from Texas Instruments, CC2500, CC2550, CC2510 and CC2511. Maximum gain is measured • Folded Dipole • PCB Antenna • 2.4 GHz to be 7.4 dB and overall size requirements for this antenna is 46 x 9 mm. Thus this is a compact, low cost and high performance antenna. Figure 1: CC2500 Folded Dipole EM. SWRA118 Page 1 of 15
    Table of Contents Design Note DN004 KEYWORDS.............................................................................................................................. 1 1 INTRODUCTION............................................................................................................. 1 ABBREVIATIONS........................................................................................................... 2 2 DESCRIPTION OF THE FOLDED DIPOLE DESIGN .................................................... 3 3 IMPLEMENTATION OF THE FOLDED DIPOLE.................................................................... 3 4 RESULTS........................................................................................................................ 5 RADIATION PATTERN .................................................................................................. 5 BANDWIDTH............................................................................................................. 12 SPURIOUS AND HARMONIC EMISSION......................................................................... 13 CONCLUSION .............................................................................................................. 13 GENERAL INFORMATION .......................................................................................... 14 DOCUMENT HISTORY................................................................................................ 14 IMPORTANT NOTICE .................................................................................................. 15 3.1 4.1 4.2 4.3 6.1 5 6 7 2 Abbreviations CC25xx CAD DXF EM LOS PCB CC2500, CC2550, CC2510, CC2511 Computer Aided Design Data eXchange Format Evaluation Module Line Of Sight Printed Circuit Board SWRA118 Page 2 of 15
    Design Note DN004 3 Description of the folded dipole design Since the impedance of the folded dipole is matched directly to the impedance of the radio no external matching components are needed. Dependent on which regulatory limits the application should comply with, two filtering capacitors might however be needed. To ensure compliance with ETSI requirements for receiver spurious emission, C121 and C131 in Figure 3 must be included. The optimum value of C121 and C131 depends on which ETSI standard to comply with. For EN 300 440, 2.2 pF is recommended and 1.5 pF is recommended for EN 300 328. The required filtering for compliance with FCC is dependent on which regulatory part to meet, part 15.247 or 15.249, and the duty cycle of the transmitted signal. Including C121 and C131 reduces the output power but ensures lower harmonic emission in TX and reduced VCO leakage in RX. Typically a board with two 1.5 pF capacitors will have 2 dB less output power than a board without C121 and C131. file is called Implementation of the folded dipole 3.1 It is important to make an exact copy of the antenna dimensions to obtain optimum performance. The easiest approach to implement the antenna in a PCB CAD tool is to import the antenna layout from either a gerber or DXF file. Such files are included in the reference design, “CC2500EM_FD_Reference_Design_1_1.zip” available at www.ti.com/lpw. The gerber is called “CC25xx_Folded_Dipole.dxf”. If the antenna is implemented on a PCB that is wider than the antenna it is important to avoid placing component or having a ground plane close to the end points of the antenna. If the CAD tool being used doesn’t support import of gerber or DXF files, Figure 2 and Table 1 can be used. Since the pinout of CC251x differs from CC2500 it might be necessary to make a slight modification on the routing of the antenna feed lines. If this is done it is important to keep the same distance between the chip and the antenna. “CC25xx_Folded_Dipole.spl” and the DXF file Figure 2: Antenna dimension. L1 L2 D1 D2 44.7 mm 21.0 mm 1.5 mm 0.9 mm H1 H2 H3 H4 2.4 mm 3.1 mm 6.0 mm 2.8 mm Table 1: Antenna dimension. SWRA118 Page 3 of 15
    Design Note DN004 Figure 3: Schematic for CC2500 folded dipole reference design. SWRA118 Page 4 of 15
    Design Note DN004 4 Results All results presented in this chapter are based on measurements performed with the CC2500 Folded Dipole EM placed on SmartRF04EB. 4.1 Radiation pattern Figure 4 shows how to relate all the radiation patterns in this section to the orientation of the antenna. The radiation patterns were measured with 0 dBm output power. XY plane XZ plane YZ plane Figure 4: How to relate the antenna to the radiation patterns. SWRA118 Page 5 of 15
    Design Note DN004 Figure 5: XY plane horizontal polarization. SWRA118 Page 6 of 15
    Design Note DN004 Figure 6: XY plane vertical polarization. SWRA118 Page 7 of 15
    Design Note DN004 Figure 7: XZ plane horizontal polarization. SWRA118 Page 8 of 15
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