2004 IEEE Topical Workshop on Power Amplifiers Load-Pull Based Design of Ultra-Linear W-CDMA Base-Station Power Amplifiers Srdjan Pajić and Zoya Popović Department of Electrical and Computer Engineering University of Colorado, Boulder William McCalpin dBm Engineering, Boulder, CO, USA Funded by: dBm Eng. WPAFB DARPA IRFFE

2004 IEEE Topical Workshop on Power Amplifiers Overview Motivation for load-pull based PA design Description of method for linearity design (~2GHz, 60W LDMOS, -45dBc ACPR) Resulting PA characterization Discussion: other PAs designed using load-pull (high-efficiency with dynamic biasing etc.)

2004 IEEE Topical Workshop on Power Amplifiers Usual Approach to PA Design 80-90% of time 10-20% of time

2004 IEEE Topical Workshop on Power Amplifiers Load-pull Based PA Design, Systemathic Approach 10% of the design time

2004 IEEE Topical Workshop on Power Amplifiers Design Example: WCDMA Base-Station PA Commercial load-pull system (Focus Microwaves) Experimental (uncharacterized) device: LDMOS, 42-finger, internally matched to ~3  V DDMAX = 66V, I DDMAX = 11 A (DC pulsed testing) Frequency range: 2.11GHz – 2.17GHz Expected CW output power: 70W Expected power gain: 12 dB Recommended drain voltage: 28V

2004 IEEE Topical Workshop on Power Amplifiers ACPR = - 45 dBc 3GPP Test Model 1, 16 DPCH, 10dB peak/av., 0.01% CCDF Z S = (8.5 + j0)  f = 2.11 GHz Z L = (1.5 – j3.25)  Source-PullLoad-Pull Design Example: WCDMA Base-Station PA

2004 IEEE Topical Workshop on Power Amplifiers Design Example: WCDMA Base-Station PA ACPR = - 45 dBc 3GPP Test Model 1, 16 DPCH, 10dB peak/av., 0.01% CCDF Z S = (7 + j0)  f = 2.17 GHz Z L = (1.5 – j3.0)  Source-PullLoad-Pull

2004 IEEE Topical Workshop on Power Amplifiers Final PA Input Bias Input Matching Output Bias Output Matching PA matching and biasing network microstrip substrate: h = mm,  R = 2.5 Design Example: WCDMA Base-Station PA

2004 IEEE Topical Workshop on Power Amplifiers Parameter variations: microstrip line dimension width: ±100  m capacitor tolerance: 5%  Z L variation: Re {Z L }: (1.3  1.6)  Im {Z L }: -(2.6  3.3)  Expected performance variation: Output ACPR < -45 dBc: 0.5 dB Power ACPR < -45 dBc: 0.75 dB Yield analysis of the output matching network Constant Power Gain (dashed) Constant Output Power (solid) Design Example: WCDMA Base-Station PA

2004 IEEE Topical Workshop on Power Amplifiers Tuning response C 1,2 C3C3 Output PA circuit half C1C1 C2C2 C3C3 C4C4 Comparison for output matching network Initially measured Z L ADS Z L Target Z L Momentum Z L Design Example: WCDMA Base-Station PA

2004 IEEE Topical Workshop on Power Amplifiers Source impedanceLoad impedance 2.11GHz 2.17GHz 2.11GHz 2.17GHz Measured Z S 2.11GHzMeasured Z L Target Z S Target Z L Pre-tuning / verification circuit and tuning results C1C1 C2C2 C3C3 C4C mm Design Example: WCDMA Base-Station PA

2004 IEEE Topical Workshop on Power Amplifiers f = 2.11 GHz f = 2.17 GHz Measured power-sweep parameters of the PA designed using this method Load-pull, ACPR = -45 dBcFinal PA, ACPR = -45 dBc f [GHz]Pout [dBm]Gain [dB]Pout [dBm]Gain [dB] Design Example: WCDMA Base-Station PA

2004 IEEE Topical Workshop on Power Amplifiers Discussion Systematic design procedure leads to one-pass PA design: DC characterized device  output power estimates load-line theory  approximate range of load impedances multiple prematching load-pull characterization  accurate and reliable target impedances Z S and Z L matching network synthesis using EM modeling of microstrip lines and lumped element modeling (or measurement)  initial load/source impedances close to targets pretuning of amplifier halves using calibrated break-apart test fixture  avoids extensive postproduction tuning. Example design – 60W WCDMA base station PA (and many others…) Approach can be applied for wide frequency and power range and practically any kind of linearity/efficiency requirements. For example…

2004 IEEE Topical Workshop on Power Amplifiers A High-Efficiency High-Frequency Example First principles assisted by load-pull measurements for first-pass success - 10-GHz class-E hybrid PA

2004 IEEE Topical Workshop on Power Amplifiers Two-stage class-E PA designed for increased gain, using “bias-pull” and same impedances for the 2 stages

2004 IEEE Topical Workshop on Power Amplifiers AM-PM characterization: Switched-mode PAs enable amplitude modulation through bias PA alone with varying Vds PA with constant Vds PA with closed-loop dynamic bias control Maintaining high efficiency while output power varies  Adaptive amplifier

2004 IEEE Topical Workshop on Power Amplifiers High-efficiency signal-adaptive X-band PA, slow and fast dynamic biasing