AN1205.04 ADVANCED COMMUNICATIONS & SENSING FINAL Application Note AN1205.04 250mW Power Amplifier Platform with the XE1205 GENERAL DESCRIPTION KEY PRODUCT FEATURES The XE1205 is an integrated transceiver operating in the 433, 868 and 915 MHz license-free ISM (Industrial, Scientific and Medical) frequency bands. This application note describes how to take advantage of a low-cost external Power Amplifier to reach an output power of up to 250 mW (+24dBm) at 915 MHz. A full bill of materials and details of regulatory compliance with §CFR 47 Part15.247 is also provided. APPLICATIONS Long Distance Automatic Meter Reading Alarm system Asset tracking Programmable RF output power: from 12 to 24 dBm Low power receive mode: 14 mA High Rx sensitivity: down to -121 dBm at 1.2 kbit/s, -116 dBm at 4.8 kbits Good transmitter efficiency: 250 mA typ. @ +24 dBm 902 to 928 MHz frequency range Lowest-Cost Bill Of Materials: L-C based output filter SUPPORT MATERIAL Schematic Drawing Bill Of Materials Gerber Files upon request Long Range Telemetry Please contact your Semtech representative. Revision 1.0 / February 2008 ©2008 Semtech Corp. Page 1 www.semtech.com AN1205.04 ADVANCED COMMUNICATIONS & SENSING FINAL Application Note Table of Contents Section 1. 2. 3. Page Board Description .................................................................................................................................................... 3 1.1. Board Overview ............................................................................................................................................... 3 1.2. Board Schematics............................................................................................................................................ 4 1.3. PCB Layout...................................................................................................................................................... 5 1.4. Bill Of Materials................................................................................................................................................ 5 Board Performance.................................................................................................................................................. 7 2.1. Output Power over the ISM Band .................................................................................................................... 7 2.2. Pout vs. Vcc ..................................................................................................................................................... 7 2.3. Pout vs. Temperature ...................................................................................................................................... 8 2.4. Spurious Emissions ......................................................................................................................................... 9 Conclusion ............................................................................................................................................................. 10 Table of Figures Figure 1. Board Overview ................................................................................................................................................3 Figure 2. Schematic Diagram ..........................................................................................................................................4 Figure 3. PCB Top Layer .................................................................................................................................................5 Figure 4. PCB Bottom Layer............................................................................................................................................ 5 Figure 5. Pout over Frequency ........................................................................................................................................ 7 Figure 6. Output Power vs. Vcc....................................................................................................................................... 8 Figure 7. Power Consumption vs. Vcc ............................................................................................................................ 8 Figure 8. Spectral Purity DC-960 MHz ............................................................................................................................9 Figure 9. Spectral Purity 960 MHz - 10 GHz .................................................................................................................10 Revision 1.0 / February 2008 ©2008 Semtech Corp. Page 2 www.semtech.com AN1205.04 250mW PA Platform with the XE1205 ADVANCED COMMUNICATIONS & SENSING FINAL Application Note 1. Board Description This 250 mW high power transceiver design is based on Semtech's XE1205 ISM band transceiver and an NEC NESG250134 SiGe RF transistor. Information about the NEC transistor can be found at the following websites: www.ncsd.necel.com www.cel.com This high power Short Range Device design is implemented on a simple low-cost, two-layer FR4 substrate board. The design is as small as 37 x 57 mm, and is intended to meet the regulatory requirements of the North American FCC Part 15.247 FHSS (Frequency Hopping Spread Spectrum) systems. 1.1. Board Overview Figure 1. Board Overview Figure 1 shows the reference design sub-divided into six different areas: XE1205 2-layer reference design (blue) - the output matching network of this stage has been modified to optimize power transfer to the following (PA) stage. Interstage Matching (yellow) - performs the impedance transformation between the XE1205 and the PA and is necessary to ensure stability. Power Amplifier (grey) - includes the PA (an NESG-250134) and its associated power supply biasing and decoupling. Antenna tank circuit and switch (white) - these components are taken from the original XE1205 reference design (downloadable from the Semtech website). However, a higher power switch (Hittite HMC595) has been used to accommodate the higher 250 mW output power. PA Output match (red) - necessary to ensure that the optimal gain, linearity and efficiency are achieved. Output Filter (purple) - required for harmonic rejection, to ensure regulatory compliance with §CFR 47 Part 15.247 of the FCC regulations. The filter is based upon discrete components for minimum cost. Revision 1.0 / February 2008 ©2008 Semtech Corp. Page 3 www.semtech.com AN1205.04 250mW PA Platform with the XE1205 ADVANCED COMMUNICATIONS & SENSING FINAL Application Note 1.2. Board Schematics Figure 2 shows the 250 mW board schematic diagram. For clarity, the sub-divisions of section 1.1 are reproduced here. Note: For the components values, please consult the Bill Of Material (BOM), in section 1.4. Figure 2. Schematic Diagram Revision 1.0 / February 2008 ©2008 Semtech Corp. Page 4 www.semtech.com AN1205.04 250mW PA Platform with the XE1205 ADVANCED COMMUNICATIONS & SENSING FINAL Application Note 1.3. PCB Layout For low-cost and practicality, the reference design has been implemented on a 2-layer, 1.6mm-thick, FR4 substrate printed circuit board. The design can be implemented on other thicknesses and other substrate materials keeping in mind the following: Any change in board thickness or material will affect the impedance of the board, as will changes in track length or thickness. The RF signal path will be especially susceptible to such changes. We recommend, where possible, the design be kept as close as possible to the reference design. The application note RF Design Guidelines: PCB Layout and Circuit Optimization can be downloaded from the Semtech website www.semtech.com if the users want to implement the reference design for their own application. Figure 3 and Figure 4 below show the two PCB layers, top and bottom sides. Figure 4. PCB Bottom Layer Figure 3. PCB Top Layer 1.4. Bill Of Materials The table below gives the values and characteristics of the components detailed in the schematic on section 1.2. It is important to note that deviation from the specified components may result in a degradation of the circuit performances. Revision 1.0 / February 2008 ©2008 Semtech Corp. Page 5 www.semtech.com AN1205.04 250mW PA Platform with the XE1205 ADVANCED COMMUNICATIONS & SENSING Table 1 FINAL Application Note Bill Of Materials at 915MHz RefDes MPN Geom Value U1 VQFN48 XE1205 XE1205I074TRLF U2 TMX S110 SMT 3.8x3.8 915MHz U3 HMC595E SC-70 6L HMC595 NX3225DA 39MHz EXS00A-02557 SMD 3.2x2.5 39.0MHz Q1 Q2 NESG250134 Power Minimold NESG250134 D1 0603 1N4148 R1 0402 1k R2 0402 1k R3 0402 1k R4 0402 680 R5 0402 1k R6 0402 1k R7 NC R8 0402 0R R9 0402 0R R10 0402 330 R11 0402 0R R434 NC R869 NC R915 0402 0R C1 0603 33pF C2 0603 1uF C3 0603 1.8pF C4 0603 1.2pF C5 0603 1.2pF C6 NC C7 0603 2.2pF C8 0603 33pF C9 NC C10 0402 1.5pF C11 0402 10nF C12 0402 1nF C13 0603 1.2pF C14 0603 33pF C15 0402 1nF C16 0402 1nF C17 NC C18 NC C19 NC C20 0603 1.2pF C21 0603 33pF C22 0603 1uF C23 0603 33pF C24 0603 68pF C25 0603 10nF C26 NC C27 NC C28 0603 3.3nF C29 0603 33pF C30 0603 10nF C32 0603 1uF C33 0603 1.8pF C34 0603 3.9pF C35 0603 33pF C36 0603 0.47pF C37 0603 2.2pF C38 NC C39 0603 2.2pF C40 0603 2.2pF C41 0402 Note 1 C42 0402 Note 1 L1 0603 10nH L2 0603 47nH L3 LQW18AN27NG00D 0603 27nH L4 0402 5.6nH L5 0402 18nH L6 0603 18nH L7 0603 3.3nH L8 0603 0R L9 0603 47nH L10 0603 0R L11 0603 0R L12 0603 0R L13 0603 47nH L15 0603 3.3nH L16 0603 6.8nH L17 0603 2.7nH SMA 50 Ohms RF_IO Note 1: C41 and C42 are ajusted to tune LO at nominal frequency of 915.000MHz Revision 1.0 / February 2008 ©2008 Semtech Corp. Qty 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 0 0 1 1 1 1 1 1 0 1 1 0 1 1 1 1 1 1 1 0 0 0 1 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Page 6 Description RF transceiver IC SAW Bandpass Filter 915MHz GaAs MMIC 3W T/R Switch Crystal 39MHz CL=8pF NPN SiGe RF Transistor General purpose 1N4148 diode Resistor (+/-5%) Resistor (+/-5%) Resistor (+/-5%) Resistor (+/-1%) Resistor (+/-5%) Resistor (+/-5%) Manufacturer Semtech Temex Hittite NDK NEC Resistor Resistor Resistor (+/-5%) Resistor Resistor Capacitor NPO (+/-5%) Capacitor Y5V (+80/-20%) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-5%) Capacitor NPO (+/-0.25pF) Capacitor X7R (+/-10%) Capacitor X7R (+/-10%) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-5%) Capacitor X7R (+/-10%) Capacitor X7R (+/-10%) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-5%) Capacitor Y5V (+80/-20%) Capacitor NPO (+/-5%) Capacitor NPO (+/-5%) Capacitor X7R (+/-10%) Capacitor X7R (+/-10%) Capacitor NPO (+/-5%) Capacitor X7R (+/-10%) Capacitor Y5V (+80/-20%) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-5%) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-0.25pF) Capacitor NPO (+/-0.25pF) Multilayer inductor Multilayer inductor Wirewound MURATA Multilayer inductor Multilayer inductor Multilayer inductor Multilayer inductor Resistor Multilayer inductor Resistor Resistor Resistor Multilayer inductor Multilayer inductor Multilayer inductor Multilayer inductor SMA Straight Jack Receptacle for PCB mount www.semtech.com AN1205.04 250mW PA Platform with the XE1205 ADVANCED COMMUNICATIONS & SENSING FINAL Application Note 2. Board Performance This application was designed to meet the conducted output power requirement of 250 mW (i.e. +24 dBm) over the 902928 MHz North American ISM band. This circuit will deliver the specified power over the following ranges: Pout=+24 dBm Vcc range from 2.4 to 3.6 V Temperature range from -40 to +85°C Output Power derating along all operating conditions: +/-2 dB 2.1. Output Power over the ISM Band Figure 5 shows the variation in ouput power of the XE1205 power amplifier circuit over the 902 to 928 MHz ISM band. The measured performance guarantees a constant link budget over the whole band of operation. Output Pow er over the Frequency Band Vcc=3.3V, m axim um pow er level 26 Pout [dBm] 25 24 23 22 21 20 902 904 906 908 910 912 914 916 918 920 922 924 926 928 Frequency [MHz] Figure 5. Pout over Frequency 2.2. Pout vs. Vcc Figure 6 below illustrates the reference design performance versus the supply voltage range for each of the output power settings of XE1205. Figure 7 then shows the total dissipation of the amplifier plus XE1205 over the same range of test conditions. Revision 1.0 / February 2008 ©2008 Semtech Corp. Page 7 www.semtech.com AN1205.04 250mW PA Platform with the XE1205 ADVANCED COMMUNICATIONS & SENSING Application Note FINAL Pout vs. Vcc 30.0 25.0 Pout [dBm] 20.0 15.0 10.0 5.0 0.0 3 3.15 3.3 3.45 3.6 Vcc [V] "11" "10" "01" "00" Figure 6. Output Power vs. Vcc Icc vs. Vcc 350 300 Icc [mA] 250 200 150 100 50 0 3 3.15 3.3 3.45 3.6 Vcc [V] "11" "10" "01" "00" Figure 7. Power Consumption vs. Vcc 2.3. Pout vs. Temperature With the combination of D1 and R10, the design exhibits a very good stability of the output power over the temperature range, i.e. from -40 to +85°C: at 25°C, 3.3V: +25.2 dBm at -40°C, 3.3V: +25.8 dBm at +85°C, 3.3V: +23.7 dBm Revision 1.0 / February 2008 ©2008 Semtech Corp. Page 8 www.semtech.com AN1205.04 250mW PA Platform with the XE1205 ADVANCED COMMUNICATIONS & SENSING Application Note FINAL 2.4. Spurious Emissions The North American regulatory constraints applicable to this circuit are given in the FCC Part 15.247 section. If the spurious emissions fall inside the restricted bands (listed under section 15.205a), their level should be below 200 microvolts per meter measured at a 3 meter distance, if their frequency is below 960 MHz. Spurious emissions that fall inside restricted bands over 960 MHz should respect a field strength limit of 500 microvolts per meter at a 3 meter distance. For any other spurii, their level should be 20 dB below that of the carrier (i.e. -20dBc). The measured radiated response will, of course, depend upon the type of antenna employed and the screening employed. Here, an equivalent conducted measurement is performed to assess compliance with the FCC limits. We define these limits as: 200 uV/m @ 3m correspond to -49.2 dBm EIRP limit below 960 MHz 500 uV/m @ 3m correspond to -41.2 dBm EIRP limit above 960 MHz These limits are shown in red on Figure 8 and Figure 9, assuming the use of a 0 dBi gain antenna. Spectral Purity from DC to 960MHz 30 20 10 Power [dBm] 0 -10 -20 -30 FRF-4*FXO -40 -50 4*FXO -60 0 100 200 300 400 500 600 700 800 900 Frequency [MHz] Figure 8. Spectral Purity DC-960 MHz A spurious emission at 4 times the crystal oscillator frequency (i.e. 156 MHz +/- 100ppm typ.) is highlighted on Figure 8. Referring to the FCC Part 15.205(a), which lists the restricted bands of operation, the 200uV/m @ 3 meters limit will apply from 156.52475 to 156.52525 MHz. This is very narrow and, since the crystal drift is not expected to be over +/-100ppm, this spur will not fall inside the restricted band. Revision 1.0 / February 2008 ©2008 Semtech Corp. Page 9 www.semtech.com AN1205.04 250mW PA Platform with the XE1205 ADVANCED COMMUNICATIONS & SENSING Application Note FINAL Spectral Purity from 960MHz to 10GHz 0 H2 -10 Power [dBm] -20 -30 H7 -40 H4 H5 -50 -60 960 1960 2960 3960 4960 5960 6960 7960 8960 9960 Frequency [MHz] Figure 9. Spectral Purity 960 MHz - 10 GHz The harmonic frequencies of the transmitter are highlighted on Figure 9. Their level is below the specified limit. Notes: Semtech suggests the user also read the accompanying application note: FCC Regulations for ISM Band Devices: 902-928 MHz. This describes in detail the North American FCC restriction on ISM band Short Range Devices. It can be downloaded from www.semtech.com The rejection of harmonic frequencies on this design, has been achieved through lumped elements, to enable the lowest-cost BOM. For size constrained applications, the filter (outlined in purple on Figure 1) can be replaced by a multilayer LTCC (Low Temperature Co-Fired Ceramic) low-pass filter. This type of filter exhibits a very good harmonic response within a single 0603 footprint. An example is the 0915LP15B026 from Johanson Technology. It offers a minimum attenuation of 30 dB on the 2nd and 3rd harmonics (actually more than 40dB). Additional information can be found at www.johansontechnology.com. 3. Conclusion A reference design for a single-stage 250 mW power amplifier in conjunction with XE1205 has been presented. This reference design uses a low-cost lumped element filter and is intended for operation in the 902-928 MHz ISM band. Applications of this circuit include, for instance, long range Automatic Meter Reading or two-way car alarm systems. Revision 1.0 / February 2008 ©2008 Semtech Corp. Page 10 www.semtech.com AN1205.04 ADVANCED COMMUNICATIONS & SENSING FINAL Application Note © Semtech 2008 All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. 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