Optimization of PA Linearity and Efficiency through Loadpull Measurements and Simulations using Modulated Signals Onno Kuijken, Komo Sulaksono, Rob Heeres, Léon van den Oever, Luc de Maaijer Philips Semiconductors, Nijmegen, The Netherlands BU Mobile & Personal

Semiconductors 2 2 of 1 Slides Outline Introduction – Problem statement and background Loadpull measurements using CW and modulated RF signals Linearity simulations using modulated RF signals and behavioural modelling Conclusions

Semiconductors 3 3 of 1 Slides Problem statement 1.Target is to make a linear, efficient power amplifier for WiBro uplink transmissions 2.Implementation platform is laminate-based multi- technology SiP with integrated RF passives

Semiconductors 4 4 of 1 Slides Linearity efficiency trade-off A WiBro uplink signal is an OFDM(A) signal with up to 864 subcarriers, 2300 MHz < f RF < 2390 MHz. –CCDF on the right –10 dB PAPR Do we really need to back-off by 10 dB? –Very detrimental for power efficiency

Semiconductors 5 5 of 1 Slides Multi-technology SiP assembly platform Application example in (quadband GSM) PA module BGY284 PASSI dies for output matching and harmonics filtering, flipchip-mounted GaAs HBT dies for PA output stages, wirebonded QUBiC die for PA first and intermediate stages, for biasing and for control, wirebonded SMDs for low-frequency supply decoupling and for interstage matching circuits, soldered Laminate substrate as mechanical carrier, I/O rerouting and collector feedlines Molded package (not shown) Layout of the two PASSI dies and their environment

Semiconductors 6 6 of 1 Slides Implementation: PASSI Passive Integration on High-Ohmic Silicon Pro (during manufacturing) –Reproducible manufacturing –Stable, reliable, reproducible assembly Con (during product development) –3 – 4 weeks processing leadtime –Little / no post-assembly tuning Total 5 mask layers high ohmic Si 5 m Al MIM capacitor 425 nm SiNx dielectric 145 pF/mm 2 Inductor Q > 2 GHz L = 1 … 10 nH

Semiconductors 7 7 of 1 Slides Outline Introduction – Problem statement and background Loadpull measurements using CW and modulated RF signals Linearity simulations using modulated RF signals and behavioural modelling Conclusions

Semiconductors 8 8 of 1 Slides Loadpull contours with an unmodulated (CW) RF signal light blue: P out contours yellow: G T contours purple: PAE contours Impedances are around 2 Z 0 = 5 measured at collector Gain, compression, efficiency versus output power for different load impedances 2.16 – j – j – j3.57

Semiconductors 9 9 of 1 Slides Z 0 = 5 Loadpull contours with a modulated RF signal At collector of output transistor, for 25 dBm output power yellow : ACLR-1 contours Optimum at (3.2 + j2.5), –37 dBc purple : ACLR-2 contours Optimum at (3.2 + j1.6), –45 dBc light blue : PAE contours Optimum at (6.8 + j5.8), 33.3% white: point of infinite happiness, best trade-off overall (4.8 + j2.9) : ACLR-1 = –34.8 dBc, ACLR-2 = –42.5 dBc, PAE = 27.0%

Semiconductors of 1 Slides Conclusion of loadpull measurements CW loadpull measurements based on signal statistics and simple amplifier metrics (CCDF, compression point) give values for load impedance which result in non-optimum efficiency For non-constant-envelope signals, loadpull measurements require real-life stimuli

Semiconductors of 1 Slides Outline Introduction – Problem statement and background Loadpull measurements using CW and modulated RF signals Linearity simulations using modulated RF signals and behavioural modelling Conclusions

Semiconductors of 1 Slides reference branch realistic behavioural model piecewise linear model Simulation set-up For Ptolemy / ADS co-simulation with modulated RF signals signal sources (file-based, downloadable to AWG)

Semiconductors of 1 Slides Behavioural model s-parameters for output match derived from EM simulation s-parameter dataset block representing PASSI output match derived from Momentum (EM) simulation

Semiconductors of 1 Slides Simulation results using behavioural models Large-signal s-parameter representation (measured / simulated) simulated and measured gain curves simulated and measured phase curves ACLR-1ACLR-2 Simulated–34.4 dBc–45.2 dBc Measured–33.6 dBc–43.5 dBc

Semiconductors of 1 Slides Outline Introduction – Problem statement and background Loadpull measurements using CW and modulated RF signals Linearity simulations using modulated RF signals and behavioural modelling Conclusions

Semiconductors of 1 Slides Conclusions Loadpull with modulated excitation signals is a necessary tool in designing highly linear, efficient power amplifiers Results obtained have been reproduced by simulations based on behavioural models. The behavioural models can be derived through simulations (including EM), measurements, or a combination This leads to almost first-time right design for integrated passive circuits