SC1894 225MHz to 3800MHz RF Power Amplifier Linearizer (RFPAL) General Description Features The SC1894 is the Scintera 3rd generation of RF PA lin- RFin/RFout PA Linearizer SoC in Standard CMOS earizers (RFPAL) that provide improved correction and Fully Adaptive Correction * functionality over the previous generations. The SC1894 Up to 28dB ACLR and 38dB IMD Improvement is a fully adaptive, RFin/RFout predistortion linearization External Reference Clock Support: solution optimized for a wide range of amplifiers, power 10, 13, 15.36, 19.2, 20, 26, and 30.72MHz levels, and communication protocols. The SC1894 uses Low Power Consumption: the PA output and input signals to adaptively generate Duty-Cycled (9%) Feedback: 600mW an optimized correction function in order to minimize the Full Adaptation: 1200mW PAs self-generated distortion and impairments. Using Frequency Range: 225MHz to 3800MHz RF-domain analog signal processing enables the SC1894 to operate over wide-signal bandwidths and consume Input Signal Bandwidth: 1.2MHz to 75MHz very low power. Packaged in 9mm x 9mm QFN Package The SC1894 goes beyond linearization and provides Operating Case Temperature: -40C to +105C accurate RF power measurement of RFIN and RFFB. Fully RoHS Compliant, Green Materials Design support features including spectral monitoring and ACLR alarm are also available. These design sup- Dual-RF Power Measurement port features are accessed through the SC1894s serial peripheral interface (SPI) bus. Benefits Ease of Use Applications Integrated RFin/RFout Solution Cellular Infrastructure (SC1894A-00C13) Reduced FW Development Single/Multicarrier, Multistandard: CDMA/EVDO, Reduces System Power Consumption and OPEX TD-SCDMA, WiMAX , WCDMA/HSDPA, LTE, and Reduces BOM Costs, Area, and Total Volume TD-LTE Smaller Power Supply, Heat Sink, and Enclosure BTS Amplifiers, RRH, Booster Amplifiers, Eliminates Microcontroller and Power Detectors Repeaters, Small Cells, Microcells, Picocells, 2 Small Implementation Size (< 6.5cm ) DAS, AAS, and MIMO Systems Field-Proven, Carrier Class Reliability Microwave Backhaul (SC1894A-00M13) BPSK, QPSK, Up to 1024-QAM IF-to-RF Outdoor Unit (ODU) Support for Adaptive Coding and Modulation (ACM) and Automatic Transmit Power Control (ATPC) Up to 100dB/s Ordering Information and Application Block Diagram appears at end of data sheet. Broadcast Infrastructure (SC1894A-00C13) UHF Digital Broadcast DVB-T/H/T2, CMMB, ISDB-T and ATSC Other Applications: Digital Terrestrial UHF Amplifiers, Exciters, Drivers and Transmitters Wide Range of PAs and Output Power Amplifier: Class A/AB and Doherty PA Process: LDMOS, GaN, GaAs, and InGaP Average PA Output Power Examples: *Performance dependent on amplifier, bias, and waveform. Cellular Infrastructure: Up to 49dBm Terrestrial Broadcast: Up to 60dBm Any Application Requiring PA Linearization 19-6957 Rev 1 7/20SC1894 225MHz to 3800MHz RF Power Amplifier Linearizer (RFPAL) from the +25C performance uses the performance of a Detailed Description given device and waveform type as the reference. This Introduction to Predistortion Using the SC1894 error is largely dominated by output variations associated Wideband signals in todays telecommunications systems with temperature. have high peak-to-average ratios and stringent spectral The PMU codes are represented as 16-bit signed integer regrowth specifications. These specifications place high and are converted to dBm (referenced to the balun input) linearity demands on power amplifiers. Linearity may using the following formula: be achieved by backing off output power at the price of For RFIN: reducing efficiency. However, this increases the compo- nent and operating costs of the power amplifier. Better RFIN PMU (CODE) 3.01 linearity may be achieved through the use of digital pre- P Balun (dBm) = 1024 distortion and other linearization techniques, but many of these are time consuming and costly to implement. + OFFSET (dBm) RFIN Wireless service providers are deploying networks with For RFFB: wider coverage, greater subscriber density, and higher data rates. These networks require more efficient power RFFB PMU (CODE) 3.01 P Balun (dBm) = amplifiers. Additionally, the emergence of distributed 1024 architectures and active antenna systems is driving the + OFFSET (dBm) need for smaller and more efficient power amplifier imple- RFFB mentations. Further, there continues to be a strong push The OFFSET and OFFSET are dependent on toward reducing the total capital and operating costs of RFIN RFFB end-system characteristics and also on the part-to-part base stations. variation of the RFPAL. For absolute accuracy, the PMU With the SC1894, the complex signal processing is done calibration procedure outlined in the release notes and in the RF domain. This results in a simple system-on-chip SPI programming guide must be followed. that offers wide signal bandwidth, broad frequency of operation, and very low power consumption. It is an ele- Measurement Considerations gant solution that reduces development costs and speeds In order to provide sufficient integration samples to allow time to market. Applicable across a broad range of signals precise measurements of signals, the default integration including 2G, 3G, 4G wireless, and other modulation time (measurement window) is fixed to 40ms. Note that if types the powerful analog signal-processing engine the measurement window is not a multiple of the system is capable of linearizing the most efficient power ampli- frame length, then the power-measurement window will fier topologies. The SC1894 is a true RFin and RFout span an incomplete frame and cause a measurement solution, supporting modular power amplifier designs error. However the synchronization of the frame and that are independent of the baseband and transceiver measurement window is not required to achieve precise subsystems. The SC1894 delivers the required efficiency measurements. and performance demanded by todays wireless systems. TDD ConsiderationsOperation with < 100% RF Power Management Unit (PMU) PA Duty Cycle Description The PMU fully supports accurate measurement of TDD waveforms. The PMU does not differentiate between Analysis samples taken when the PA is on versus when the PA is The RFIN and RFFB log slope and intercept are derived off. Though easily compensated, this condition will affect using a linear regression performed on data collected the reading for waveforms with less than 100% duty cycle under nominal operating conditions. The error from linear (e.g., TDD applications). For example, the PMU value response to the CW waveform is the dB difference in out- read for a 50% duty-cycle waveform will be 3dB lower put from the ideal output. This is a measure of the linearity than the value for the same signal but with a 100% duty of the device response to both CW and modulated wave- cycle. Calculating the offset associated with TDD mea- forms. Error from the linear response to the CW waveform surements is straightforward and may be handled by the is a measure of relative accuracy because the system has PMU depending on the system requirements. Refer to the yet to be calibrated. However, it verifies the linearity and Release Notes for additional details on different methods. the effect of modulation on the device response. Error Maxim Integrated 2 www.maximintegrated.com