Wireless Infrastructure
interface (SPI), two phase shifters, two digital step attenuators and a 90-degree splitter that otherwise would have been a discrete component. For each one of the different paths, MPAC offers engineers maximum flexibility in adjusting the phase and the amplitude, allowing them to independently tune the carrier and peaking paths all through the SPI.
the same transmitter performance and have the flexibility to actively tune for operational and environmental factors. With a wide phase shift range of 87.2º, and a fine step size of 2.8º, MPAC delivers high linearity of 65 dBm IIP3 and extremely low power consumption of 300 µA. In addition it can support 31dBm of input RF
Figure 3: UltraCMOS MPAC evaluation kits are now available
MPAC eliminates the need for multiple discrete components and enables wireless-infrastructure vendors to improve system performance, lower cost, improve the overall product reliability and deliver maximum tuning flexibility for either LDMOS (laterally diffused metal oxide semiconductor) or GaN (gallium nitride) based Doherty power amplifier architectures. • Higher system performance: MPAC improves linearity across the frequency range, providing the Doherty bandwidth better matching based on a known impedance rather than variable impedances from discrete components. MPAC also improves the DPD-loop performance with broader bandwidth, delivering higher PAE and a better signal output. • Lower cost: MPAC improves the Doherty PA yield by making the peaking and carrier paths uniform. Engineers can relax the production margins used for their power transistors, and potentially use smaller, cheaper power transistors to accomplish the same function. MPAC also facilitates using the cheaper asymmetric Doherty configuration, which has a smaller carrier PA and offers cost reductions. The efficiency gain through MPAC also results in power savings, which reduces energy and standard BOM costs (heat sink, power supply, fans, etc.). • Higher reliability: MPAC increases the yield of power amplifier sub-assemblies and improves uniformity and repeatability between transmit paths. • Tuning flexibility: MPAC gives engineers the maximum flexibility to adjust the phase and amplitude of each one of the different paths. The Doherty architecture can be accurately optimised using automated calibration routines through the digital interface. Wireless-infrastructure vendors will be able to ship a dozen products that have
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power and has high port to port isolation of 30 dBm. As MPAC is built on an UltraCMOS monolithic die, RF engineers can confidently trust the industry-proven uniformity and manufacturing reliability of the UltraCMOS process. Only UltraCMOS technology enables intelligent integration, something GaAs technology can never achieve. If an MPAC-like solution were built on any other technology, such as GaAs, the result would be a multi-chip module held together by a myriad of bond wires. Additionally, UltraCMOS technology enables superior ESD performance of 1 kV, an extended temperature range up to 105-degree Celsius and a wide power supply range from 2.7 to 5.5V.
Beyond Doherty amplifiers, MPAC can be used in optimizing performance for other dual path, dynamically load modulated amplifier architectures, such as LINC and Chireix amplifiers. Additionally, MPAC can be utilized for vector generation purposes in feed forward amplifiers, beam-forming networks and dual polarized alignment/generation applications. In summary, the explosive growth of the LTE market has fuelled demand for Doherty architectures, and this demand will increase with LTE-A. Both LTE and LTE-A need high peak-to-average ratios, and the Doherty architecture provides a unique advantage. The market needs solutions that improve the Doherty's phase and amplitude precision, maximize performance, lower costs and deliver tuning flexibility. UltraCMOS MPAC is that solution.
Peregrine Semiconductor |
www.psemi.com
Kinana Hussain is senior marketing manager at Peregrine Semiconductor
Components in Electronics September 2014 25
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