Plextek RFI www.plextekRFI.com Our expertise is your advantage Plextek RFI www.plextekRFI.com Our expertise is your advantage Plextek RFI www.plextekRFI.com Our expertise is your advantage Plextek RF RFIIntegration Design of a 100W, X-band GaN PA Using Discrete Transistor Die Stuart Glynn, Liam Devlin, Graham Pearson [email protected] www.plextekRFI.com Our expertise is your advantage Plextek RFI Introduction • Solid-state PA covering 10.5 to 11.5GHz • Psat > 100W • Small signal gain > 23dB • Design based on discrete GaN transistor die (Cree, 0.25µm, 40V bias) – Power levels available from 50Ω matched MMICs require combination of too many parts – Packaged X-band power transistors are pre-matched for specific bands – Discrete die allow a very compact implementation and flexibility of operating band www.plextekRFI.com Our expertise is your advantage Transistor Selection Plextek RFI • Available die, all 18GHz devices from Cree’s 40V, 0.25µm, GaN on SiC Process CGHV1J006D CGHV1J025D CGHV1J070D Output Power 6W 25W 70W Die Width 0.84mm 1.92mm 4.80mm Electrical Die Width at 11GHz (in air) 11.1° 25.3° 63.4° www.plextekRFI.com Our expertise is your advantage Plextek RFI Transistor Performance Analysis • Initial device performance analysis undertaken to determine: – Matching topologies – Requirements to ensure unconditional stability – Trade off in Psat and PAE – Initial estimate of thermal performance • Useful application note available from Agilent at: – http://cp.literature.agilent.com/litweb/pdf/5991-4154EN.pdf • Corresponding workspace available free of charge from Agilent at: – http://bit.ly/1jZ2eYT www.plextekRFI.com Our expertise is your advantage Plextek RFI Transistor Performance Analysis • Standard Cree two-port large signal model in ADS Selected quiescent bias point: 50mA/mm www.plextekRFI.com Our expertise is your advantage Plextek RFI Transistor Performance Analysis • Distributed model based on Cree 0.25µm process PDK in ADS www.plextekRFI.com Our expertise is your advantage Plextek RFI Single Transistor – Stability • At 11GHz the transistor die is not unconditionally stable, gate resistance is required to ensure unconditional stability: – Bare die, no gate resistance – Bare die with 0.4Ω series gate resistance www.plextekRFI.com Our expertise is your advantage Plextek RFI Transistor Performance Analysis • Distributed model based on Cree 0.25µm process PDK in ADS www.plextekRFI.com Our expertise is your advantage Plextek RFI Second Harmonic Termination Best case termination Worst case termination Design target at 22GHz Centre of Smith Chart is 5.0 +j0.0 Ω www.plextekRFI.com Our expertise is your advantage Plextek RFI Third Harmonic Termination Best case termination Worst case termination Design target at 33GHz Centre of Smith Chart is 5.0 +j0.0 Ω www.plextekRFI.com Our expertise is your advantage Plextek RFI Transistor Performance Analysis • Re-sweeping fundamental load with updated harmonic terminations www.plextekRFI.com Our expertise is your advantage Plextek RFI Thermal Considerations • Thermal Conductivity of SiC, Gold and GaAs at Room Temperature www.plextekRFI.com Material Thermal Conductivity (W/°C.cm) SiC 4.30 Gold (Au) 3.17 GaAs 0.46 Our expertise is your advantage Thermal Considerations Plextek RFI • Variation of Thermal Conductivity of SiC and GaAs with Temperature 5 0.5 0.45 4 0.4 3.5 0.35 3 0.3 2.5 0.25 2 0.2 1.5 0.15 1 0.1 0.5 GaAs Thermal Conductivity (W/degC.cm) SiC Thermal Conductivity (W/degC.cm) 4.5 SiC GaAs 0.05 0 0 0 50 100 150 200 250 300 Temperature (degC) www.plextekRFI.com Our expertise is your advantage Plextek RFI Channel Temperature • Quiescent and Psat – Standard Cree model, tcase=85°C – Quiescent bias 50mA/mm – Ideal source and load matches at 11GHz. – Input power at 11GHz swept from -20dBm to 35dBm. – Junction temperature is 122.4°C under quiescent conditions and150.4°C at 5dB compression. www.plextekRFI.com Our expertise is your advantage Output Stage Topology Plextek RFI • Selected device has Psat of 25W • Allowing for combiner, matching and bias network losses we assume the use of 6 transistors • Balanced topology with each branch driving 3 power-combined transistors: 3 Vgg Input Matching Network W A Y RF i/p Gate Bias Tee www.plextekRFI.com S P L I T T E R Input Matching Network Input Matching Network Output Matching Network Output Matching Network Output Matching Network 3 W A Y C O M B I N E R Vdd Drain Bias Tee RF o/p Our expertise is your advantage Plextek RFI Implementation of 3-Transistor Block • Design of bias-tees • Design of input and output matching • Single transistor performance – Small signal performance – Large signal performance • Performance of 3 transistor block – Small signal performance – Large signal performance www.plextekRFI.com Our expertise is your advantage Plextek RFI Gate Bias Tee Design Substrate is 30 thou RT/duroid 6002 with 2oz copper www.plextekRFI.com Our expertise is your advantage Plextek RFI www.plextekRFI.com Gate Bias Tee – S-parameters Our expertise is your advantage Plextek RFI EM Analysis • Essential for accurate prediction of performance at microwave/mm-wave frequencies • Momentum 2.5D EM simulator integral to ADS • Optimisation of layout required after EM simulation to account for proximity and discontinuity effects • More details of how to do this can be found in the Plextek RFI video tutorial “Designing mm-wave integrated filters using Agilent ADS” – http://www.youtube.com/watch?v=PnkGkb3q3Qo – Full technical tutorial video library: • http://www.plextekrfi.com/publications/video-tutorials.html www.plextekRFI.com Our expertise is your advantage Plextek RFI www.plextekRFI.com Drain Bias Tee Design Our expertise is your advantage Plextek RFI • Design of Output Matching Target Load Impedance at 11GHz: (2.59 + j7.0)Ω • Impedance presented by output match: (2.27 + j7.21)Ω at 11GHz Centre of Smith Chart : 5.0 +j0.0Ω Z = (2.27 +j7.21)Ω at 11GHz www.plextekRFI.com Z = 50Ω Our expertise is your advantage Plextek RFI • Design of Output Matching Target Load Impedance at 22GHz: (0.38 + j18.65)Ω • Impedance presented by output match: (0.12 + j18.94)Ω at 22GHz • Target Load Impedance at 33GHz: (0.83 + j28.33)Ω • Impedance presented by output match: (0.1 + j30.15)Ω at 33GHz www.plextekRFI.com Centre of Smith Chart : 5.0 +j0.0Ω Our expertise is your advantage Plextek RFI Design of Input Matching • Target Source Impedance at 11GHz: (1.0 + j0.0)Ω • Impedance presented by input match: (1.6 + j0.06)Ω at 11GHz; includes series gate resistance for stability Centre of Smith Chart : 5.0 +j0.0Ω Z = 50Ω www.plextekRFI.com Z = (1.6 +j0.06)Ω at 11GHz Our expertise is your advantage Plextek RFI Single Transistor – Small Signal • Includes gate and drain bias tees www.plextekRFI.com Our expertise is your advantage Plextek RFI Single Transistor – Large Signal • Large Signal Performance at 5dB Compression (Psat is ≈23.4W). Includes gate and drain bias tees: www.plextekRFI.com Our expertise is your advantage Plextek RFI ADS Schematic • Of 3-transistor block: www.plextekRFI.com Our expertise is your advantage Plextek RFI Loop Stability Analysis Loop Gain dB = 20log10 (vout/vin) www.plextekRFI.com Our expertise is your advantage Plextek RFI www.plextekRFI.com Loop Stability Analysis Our expertise is your advantage Plextek RFI Loop Stability Analysis • Improving loop stability – adding balancing resistors: www.plextekRFI.com Lp Lp Rb Rb Lp Lp Our expertise is your advantage Plextek RFI www.plextekRFI.com Loop Stability Analysis Our expertise is your advantage Plextek RFI Small Signal Performance • Of 3-transistor block: www.plextekRFI.com Our expertise is your advantage Plextek RFI Large Signal Performance • Of 3-transistor block at 5dB Compression (Psat is ≈ 69W): www.plextekRFI.com Our expertise is your advantage Plextek RFI Balanced Combination • Two 3-transistor blocks are power combined with Branch Line couplers (ADS schematic): www.plextekRFI.com Our expertise is your advantage Plextek RFI Balanced Output Stage • Small Signal Performance: www.plextekRFI.com Our expertise is your advantage Plextek RFI Balanced Output Stage • Large Signal Performance at 5dB Compression (Psat is ≈125W): www.plextekRFI.com Our expertise is your advantage Plextek RFI Balanced Output Stage • Large Signal Performance at 4dB Compression (Pout is ≈110W): www.plextekRFI.com Our expertise is your advantage Plextek RFI Sizing of Driver Stage • Selecting the optimum size of the driver stage: Parameter at 11GHz Balanced Output Stage 3-Transistor Block Dual Transistor Single Transistor Gain (dB) 13.6 13.6 13.6 13.8 P-5dB (dBm) 51.2 48.3 46.8 43.9 Input Referred P-5dB (dBm) 42.6 39.7 38.2 35.1 P-1dB (dBm) 41.2 38.2 36.4 33.5 www.plextekRFI.com Our expertise is your advantage Plextek RFI Driver Stage • Schematic – Driver stage uses two 25W amplifiers in a balanced configuration: www.plextekRFI.com Our expertise is your advantage Plextek RFI Driver stage • Small Signal Performance: www.plextekRFI.com Our expertise is your advantage Plextek RFI Driver Stage • Large Signal Performance at 2dB Compression (Pout is ≈11.3W): www.plextekRFI.com Our expertise is your advantage Plextek RFI Complete Two-stage PA • Small Signal Performance: www.plextekRFI.com Our expertise is your advantage Plextek RFI Complete Two-stage PA • Large Signal Performance at 6dB Compression (Psat is ≈110W): www.plextekRFI.com Our expertise is your advantage Plextek RFI Gain Compression Characteristics • Compression of each stage and complete PA at 11GHz: www.plextekRFI.com Our expertise is your advantage Plextek RFI Complete Two-stage PA • Output Spectrum at P-6dB, 11GHz www.plextekRFI.com Our expertise is your advantage Plextek RFI Complete Two-stage PA • Second Harmonic Rejection (compared to fundamental), 29dBm Input Power, 10GHz to 12GHz www.plextekRFI.com Our expertise is your advantage Plextek RFI Complete Two-stage PA • Performance variation with changing load: www.plextekRFI.com Our expertise is your advantage Plextek RFI Complete Two-stage PA • Performance variation with changing load: www.plextekRFI.com Our expertise is your advantage Plextek RFI Complete Two-stage PA • Performance variation with changing load: www.plextekRFI.com Our expertise is your advantage Plextek RFI Summary/Conclusions • Design and simulation of a 100W, X-band PA module presented • Based on 0.25µm gate length, bare die transistors from Cree • Uses mixed bare die/SMT assembly with thin film matching components • Six transistors (CGHV1J025D) used in the output stage and two in the input stage • Final simulation shows a Psat of 110W at 6dB compression across 10.5 to 11.5GHz • Small signal gain is 26.8dB with input and output return losses of > 22dB www.plextekRFI.com Our expertise is your advantage Plextek RFI www.plextekRFI.com Our expertise is your advantage Plextek RFI www.plextekRFI.com Our expertise is your advantage