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AN RFMD® APPLICATION NOTE Application Note RFG1M09180, 865MHz to 895MHz, 48V, 400Wpk Doherty Reference Design Abstract This application note is a reference point for an amplifier circuit design using RFMD’s RFG1M09180 in a Symmetrical Doherty configuration using two RFG1M09180 devices. The frequency of operation is optimized for the 869MHz to 895MHz frequency range. The operating drain voltage is 48VDC at an output power of +50dBm, with >17dB gain, and >50% drain efficiency. The RFG1M09180 is optimized for commercial infrastructure applications in the 700MHz to 1000MHz frequency band, ideal for WCDMA and LTE applications. Using an advanced 48V high power density Gallium Nitride (GaN) semiconductor process optimized for high peak to average ratio applications, these highperformance amplifiers achieve high efficiency and flat gain over a broad frequency range in a single amplifier design. The RFG1M09180 is an input pre-matched GaN transistor packaged in an air cavity ceramic package, which provides excellent thermal stability. Ease of integration is accomplished through the incorporation of simple optimized matching networks external to the package that provide wideband gain, efficiency, and linearizable performance in a single amplifier. Introduction The reference design circuit described in this document was designed to achieve a maximum back-off efficiency and linearity through trade-offs between output power, gain, distortion, and efficiency. All recommended components are standard values available from well-known manufacturers. Components specified in the bill of materials (BOM) have known parasitics, which may affect the circuit’s performance. Deviating from the recommended BOM or design layout may result in a performance shift due to different parasitics, line impedances, and line lengths. Component placement, line impedances, and line lengths are critical to each circuit’s performance. Circuit Details The circuit recommended for this application note was designed using the following PCB material: • Material: Taconic, RF-60A • Core thickness: 0.025 inch • Copper cladding: 1.0oz with plating • Dielectric constant: 6.15 at 10GHz • Dissipation Factor: 0.0038 at 10GHz http://www.taconic-add.com/en--index.php http://www.taconic-add.com/pdf/rf60a.pdf A 0.25” thick copper plate interface was used between device flange and aluminum heat sink. Aluminum heat sink is Cool Innovations dense pin configuration #3-505017R http://www.coolinnovations.com/ http://www.coolinnovations.com/includes/pdf/heatsinks/3-5050XXR.pdf RF MICRO DEVICES® and RFMD® are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks, and registered trademarks are the property of their respective owners. ©2013, RF Micro Devices, Inc. AN130410 7628 Thorndike Road, Greensboro, NC 27409-9421 – For sales or technical Support, contact RFMD at (+1) 336-678-5570 or [email protected] 1 of 9 AN RFMD D® APPLICA ATION NOTE E Design Background B Information As system ms move to complex modulations, am mplifier design ns are requirred to handle e the peak power requireme ents in order to t keep nonlinearity levels at a minimu um. One tradiitional straighttforward meth hod to combat no onlinearity is to design an n amplifier us sing the large est power tra ansistor availa able. As the power transistor size reaches a maximum, adding additio onal transistorrs in parallel (in a balanced d configuratio on) will increase the peak powe er capability. The T issue bec comes average e power (backk-off) efficienccy. Even thoug gh the balanced amplifier is de esigned and tuned for peak k power and e efficiency, the e efficiency at the average power c wavefforms is much h less. The Do oherty amplifie er design imprroves the averrage power ba ack-off levels in complex efficiency without a majo or degradation n in RF perform mance. erty amplifier transistors t are e biased differrently from th heir balanced amplifier coun nterparts. Typ pically, The Dohe balanced amplifiers a are biased equally, so they turrn on and ope erate in unison n. The Dohertty amplifier ha as one transistor that operates s as the carrie er (or main) amplifier and one or more e transistors tthat operate a as the peaking amplifier. a For this t reference e design, the carrier ampliffier transistor is biased in cclass AB, so it can amplify the e incoming sig gnal under all levels of power. The peakin ng amplifier iss biased in cla ass C, thereforre, will only amplify signals wh hen they reach h a large enough level (the e peaks) to tu urn on the gatte. Also, the d design w the peaking amplifierr is “turned offf” incorporatess quarterwave e lines configuration of the carrrier amplifier while hing structures s effectively sh hifting the load d impedance tto a state thatt increases the e efficiency at lower and match power leve els. In a Dohe erty amplifier, the t efficiency and linearity ttrade-off can be shifted eassily by changin ng the amount off bias voltage applied a to the gate of the ca arrier and peakking amplifier. wing informattion describes s the fundam mental differe nces between traditional balanced am mplifier The follow configuration and the Do oherty configu uration. Additio onal informatio on on Dohertyy amplifier dessign can be fou und at w.rfmd.com/cs//documents/C CommDRunton nPASymposium m11.pdf http://www xplore.ieee.org/xpl/login.jsp?tp=&arnumber=5616135& &url=http%3A% %2F%2Fieeexxplore.ieee.org g%2Fi http://ieeex el5%2F5606055%2F5614756%2F056 616135.pdf%3 3Farnumber% %3D5616135 http://www w.home.agilentt.com/upload/c cmc_upload/A All/7March2013 3Webcast.pdff?&cc=US&lc= =eng TRADITION NAL AMPLIFIER: Good for High H power op peration Both amplifier A1 and A2 A contribute equally e to POUTT ciency versus POUT characte eristics Both have standard Effic SYMMETRICAL DOHERTY Y AMPLIFIER: Good for 3 to 7dB Back--off operation A1 and A2 2 operate independently whe en needed RF MICRO DEVICES S® and RFMD® are trademarks of RFMD D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp pective owners. ©2013, RF Micro Devicces, Inc. AN13 30410 7628 Thorndike Road, Gree ensboro, NC 27409 9-9421 – For sales oor technical Supportt, contact RFMD at (+1) 336-678-5570 or [email protected] 2 of 9 AN RFMD D® APPLICA ATION NOTE E A1 operate es most of the e time - handle es average sig gnal A2 operate es only when peak power is s needed ed carrier pow wer by 3dB Load Modulation droppe es the efficienc cy enhanceme ent point back This move Even more e suitable for CDMA C type sig gnals ASYMMETR RICAL DOHERT TY AMPLIFIER: Good for 7dB 7 to 10dB back-off operattion Change th he ratio of the carrier/peaking amplifier pow wer Equal pow wer creates ma aximum efficie ency at -6dB Size the ca arrier amplifier smaller to efffectively move e the maximum m efficiency po oint lower in average powerr, suitable fo or higher peak to average ra atio signals RF MICRO DEVICES S® and RFMD® are trademarks of RFMD D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp pective owners. ©2013, RF Micro Devicces, Inc. AN13 30410 7628 Thorndike Road, Gree ensboro, NC 27409 9-9421 – For sales oor technical Supportt, contact RFMD at (+1) 336-678-5570 or [email protected] 3 of 9 AN RFMD D® APPLICA ATION NOTE E Typical Performa ance RFG1M09180, 865 5MHz to 895MHz, 48V,, 400Wpk S Symmetrical Doherty Re eference De esign RF MICRO DEVICES S® and RFMD® are trademarks of RFMD D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp pective owners. ©2013, RF Micro Devicces, Inc. AN13 30410 7628 Thorndike Road, Gree ensboro, NC 27409 9-9421 – For sales oor technical Supportt, contact RFMD at (+1) 336-678-5570 or [email protected] 4 of 9 AN RFMD D® APPLICA ATION NOTE E Sc chematic RFG1M09180, 865 5MHz to 895MHz, 48V, 400Wpk S Symmetrical Doherty Re eference De esign RF MICRO DEVICES S® and RFMD® are trademarks of RFMD D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp pective owners. ©2013, RF Micro Devicces, Inc. AN13 30410 7628 Thorndike Road, Gree ensboro, NC 27409 9-9421 – For sales oor technical Supportt, contact RFMD at (+1) 336-678-5570 or [email protected] 5 of 9 AN RFMD D® APPLICA ATION NOTE E Bill of o Materia als RFG1M09180, 865 5MHz to 895MHz, 48V, 400Wpk S Symmetrical Doherty Re eference De esign Component Value Manufaacturer Part Num mber C1-C4 100pF ATC C ATC800A1 101JT C5-C6 8.2pF ATC C ATC800A8 8R2CT C7-C12 56pF ATC C ATC100B5 560JT C13-C14 6.8pF ATC C ATC100B6 6R8CT C15-C20 4.7F Muraata GRM55ER72A475KA01L C21-C26 0.1F Muraata GRM32NR72A A104KA01L C27-C28 100F Panassonic ECE-V1HA1 101UP C29-C30 330F Panassonic EEU-FC2A A331 R1-R2 100 Panassonic ERJ-1TYJ1 101U R3-R4 10 Panassonic ERJ-8GEYJJ100V X1 90° Hybrid H Coupler Anarren XC0900LL-03S Photo RFG1M09180, 865 5MHz to 895MHz, 48V,, 400Wpk S Symmetrical Doherty Re eference De esign RF MICRO DEVICES S® and RFMD® are trademarks of RFMD D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp pective owners. ©2013, RF Micro Devicces, Inc. AN13 30410 7628 Thorndike Road, Gree ensboro, NC 27409 9-9421 – For sales oor technical Supportt, contact RFMD at (+1) 336-678-5570 or [email protected] 6 of 9 AN RFMD® APPLICATION NOTE Parts Layout RFG1M09180, 865MHz to 895MHz, 48V, 400Wpk Symmetrical Doherty Reference Design RF MICRO DEVICES® and RFMD® are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks, and registered trademarks are the property of their respective owners. ©2013, RF Micro Devices, Inc. AN130410 7628 Thorndike Road, Greensboro, NC 27409-9421 – For sales or technical Support, contact RFMD at (+1) 336-678-5570 or [email protected] 7 of 9 AN RFMD D® APPLICA ATION NOTE E Thermal Managemen nt As with mo ost power amp plifiers, the circuit must have e adequate the ermal manage ement in orderr to operate effectively and reliably. Therefore, T an external fan and a thermal co ompound betw ween flange off the device an nd a recommen nded. heat sink are Mounting g Instruction ns STEPS FOR R MOUNTING A FLANGED DEV VICE 1. Heat-sink H surface flatness control. a. Surface finish = average deviation d of the mean m value of thee surface height. b. Surface roughness (Ra) = 0.8m ( 0.03mills) 2. A clean interface surface s on both th he heat-sink and flange. f 3. Device D mounting holes h need to be clean c and flat (no o burrs). 4. Apply A a “thin” and even layer of the ermal compound to t the surface of tthe flange. 5. Place P the device, “flange-side-down “ n”, into the recesss of the PCB. 6. Attach A the device to the PBC/Heat-sink with the specified the screw aand washer assem mbly. (S SS #4-40 X ¾ captive SHCS and RND R Shim-bearingg. .178”O.D. X .12 23” ID X .01” Thic k) 7. Use U a Two Step torque sequence: a. 1st step torque the screw w and washer on each e side = 0.5kgg.cm. b. 2nd step p torque the screw w and washer on each side = 6kg.ccm (+- 1kg.cm). Caution: excessive torque e may damage the e flanged device. 8. Solder S the device leads to the PCB.. ustry standard is to t use a Pb-free alloy a (typically SAC C305; 96.5%Sn, 3 3%Ag, 0.5%Cu) with a liquidus a. One indu tempera ature of 221°C. b. Tempera ature at the device lead interface should s be <400°C C (750°F) for <10 0 seconds. c. Pre-tin th he leads to reduce any effects of ‘ggold embrittlemennt’. RF MICRO DEVICES S® and RFMD® are trademarks of RFMD D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp pective owners. ©2013, RF Micro Devicces, Inc. AN13 30410 7628 Thorndike Road, Gree ensboro, NC 27409 9-9421 – For sales oor technical Supportt, contact RFMD at (+1) 336-678-5570 or [email protected] 8 of 9 AN RFMD D® APPLICA ATION NOTE E Biasing instructions for f the RFG1 1M09180 Syymmetrical D Doherty 1. 2. 3. 4. 5. 6. 7. 8. Connect C RF cables at RFIN and RFO OUT Connect C ground to o the ground supp ply terminal, and ensure e that both tthe VG and VD grrounds are also co onnected to this gground terminal Apply A -6.5V to VG_ _PEAK Apply A -5.5V to VG_ _CARRIER Apply A 48V to VG In ncrease VG_CARRIER until drain curren nt reaches 600mA A or desired bias point. Turn T on the RF inp put power Readjust R VG_PEAK fo or desired linearityy versus efficienccy RF MICRO DEVICES S® and RFMD® are trademarks of RFMD D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp pective owners. ©2013, RF Micro Devicces, Inc. AN13 30410 7628 Thorndike Road, Gree ensboro, NC 27409 9-9421 – For sales oor technical Supportt, contact RFMD at (+1) 336-678-5570 or [email protected] 9 of 9