Power amplifiers (PAs) and power-amplifier modules (PAMs) are being made smaller and with more functionality to meet the requirements of third/ fourth-generation (3G/4G) multiband, multimode phones. Whether based on Wideband Code Division Multiple Access (WCDMA) or Long Term Evolution (LTE) formats, those phones must provide more talk time, faster data rates, and streaming video. To achieve such performance, the PAs and PAMs must deliver good linearity and high efficiency in miniature packagesand at low cost, of course.
Eying CDMA, WCDMA, and LTE handsets and datacards, Skyworks Solutions has readied five 3-x-3-mm PAMs with an integrated coupler. These modules were designed to meet the spectral linearity requirements of high-speed downlink packet access (HSDPA), high-speed uplink packet access (HSUPA), and LTE with high power-added efficiency (PAE). The PAMs include bias and input and interstage matching circuits in a single galliumarsenide (GaAs)-based monolithic microwave integrated circuit (MMIC). Because output matching circuitry is included in the packaged multichip module (MCM), only a few passive components are needed outside the amplifier package.
The SKY77701 is tailored to cover 1920 to 1980 MHz with 40-percent PAE while delivering +28.25 dBm output power. Its sibling, the SKY77702, spans 1850 to 1910 MHz with 40-percent PAE while providing +28.6 dBm output power. Other members in this series include the SKY77703/04/05. The SKY77703 is designed to cover 1710 to 1785 MHz with 40-percent PAE at +28.4 dBm power output. In contrast, the SKY77704 spans 824 to 849 MHz with 40-percent PAE while providing +28.25 dBm output. Lastly, SKY77705 covers a range of 880 to 915 MHz with 40-percent PAE at +28.5 dBm output power.
All five of the MMICs are manufactured using an indium-gallium-phosphide (InGaP) GaAs heterojunction-bipolartransistor (HBT) BiFET process. This process provides for all positive-voltage DC supply operation while maintaining high efficiency and good linearity.
By combining a proprietary architecture with copper-flip (CuFlip) interconnect technology and a GaAs InGaP HBT process, TriQuint Semiconductor has readied an integrated PAM family with a built-in regulator and a high-performance coupler. Called TRITON, the devices target spaceconstrained WCDMA/HSUPA applications. The line's latest addition is the TQM776003, a fully matched, three-gainstate PAM that operates in low-, medium-, and high-power mode to minimize current consumption and maximize talk time. Housed in a 4-x-4-mm package, the TQM776003 provides +28 dBm output power with receive band noise of −140 dBm/Hz and an adjacent-channel leakage ratio (ACLR) of −43 dBc.
For GSM/EDGE wireless handsets, the maker also has added a new PAM to the HADRON II family. The TQM7M5012H, which comes in a 5-x-5-mm package, is optimized for high EDGE efficiency, Rx-band noise performance, and ACPR and EVM in an open-loop polar modulation for class E2+ operation. It maintains high GSM/GPRS efficiency with typical GSM efficiency of at least 50 percent as well, while EDGE is rated at 25 percent.
Meanwhile, TriQuint continues to shrink the size of the Tritium PA plus duplexer family. The newest addition, called the TQM676021, packs a 3-V linear PA, duplexer, transmit filter, and highly accurate power detector in a 7-x-4-mm package. It is designed for UMTS handset applications with support for HSUPA transmission data rates to 10 Mb/s. Efforts are under way to further reduce the size to 3 x 5 mm by 2011, states Shane Smith, Director of Marketing for TriQuint's mobile devices.
With a focus on smartphones and mobile-Internet devices, RF Micro Devices has developed a multiband, multimode PA platform called PowerSmart. At the center of this platform is a new RF Configurable PowerCore that can process all popular cellular modulation schemes including 3G and 4G. Its building blocks include PAs, power-management, switching, and signal-conditioning circuits. In essence, PowerSmart is modulation agnostic and can support four bands of GSM/GPRS or EDGE and up to five bands of TD-SCDMA, WCDMA/ HSPA+, LTE, WiMAX, or CDMA. These capabilities are offered within a product footprint that is 35 percent smaller than modern high-volume quad-band solutions, points out Ben Thomas, Marketing Director for RFMD's 3G/4G product line.
The first PowerSmart power platform is the RFRD6460 (see "Power Amps Boost Multimode, Multiband Signals," November 2009 FOCUS supplement). This 3G-focused solution is expected to go into production by the first quarter of 2011. The manufacturer also has commenced volume production of seven WCDMA/HSPA+ PAs belonging to the RF720x family. They are optimized to work with 3G-transceiver chipset suppliers like those from QUALCOMM. Because the trend is toward incorporating band switches on board, RFMD designers also are investigating CMOS-based switch technologies, such as silicon-oninsulator (SOI), for integration into PA modules along with the antenna switch and duplexer/filter.
Reducing current consumption while adding functions is the norm at ANADIGICS as well. Recently, the supplier released a set of multimode PAMs for 4G LTE and advanced HSPA+ handsets and data cards. Utilizing its fourth-generation, high efficiency at low power (HELP) technology, the ALT6701/02/04/12/13 features low quiescent current and an integrated daisy-chain directional coupler with 20 dB directivity. To maximize PAE at several power levels, the PAM offers three power modes. It is sampling now in a 10-pin, 3-x-3-x-1-mm package.
Supporting Universal Mobile Telecommunication System (UMTS) bands 1, 2, 4, 5, and 8 in addition to CDMA and LTE, Avago Technologies has announced the ACPM-500x and -520x series PAMs with integrated 20-dB directional couplers and multimode power control. By adjusting maximum output power, the internally matched amplifiers are optimized to maximize PAE. Implemented in Avago's fifth-generation CoolPAM technology, the units offer lower quiescent current to 3 mA. They provide a switchless active bypass mode for higher PAE at low output- power levels. As a result, the PAMs feature PAE of 12 to 20 percent in bypass mode and 20 to 25 percent in mid-power mode. Other features include internally matched 50-Ω input and output ports. The devices come in a surface-mount 3-x-3-mm package and draw less than 5 A current drain in power-down mode.
Mimix Broadband, Inc., which has merged with M/A-COM Technology Solutions, has developed a PAM for WiMAX applications between 4.9 and 5.9 GHz. The frequency of the internally matched amplifier can be slightly shifted by adding external components to cover 3.5 and 5 GHz. Housed in a 7-x-7- mm package, the XP1044-QL two-stage amplifier delivers 18.5 dB gain and +34 dBm power at 1-dB compression. It provides less than 2 percent EVM at +26 dBm output with an IEEE 802.16 OFDM signal and peak-to-average ratio of 9.17 dB.
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CMOS Power Amplifiers
Complementary-metal-oxide-semiconductor (CMOS) technology has captured most of the functions on a handset's printed-circuit boardexcept the PA. Finally, several CMOS designers have broken ground in developing CMOS PAs that provide performance and reliability that matches the incumbent GaAs but at lower cost. They also promise to be able to integrate more on a single die.
Two startups that have overcome performance, integration, and reliability hurdles include Javelin Semiconductor and Black Sand Technologies. In fact, Javelin Semiconductor has begun sampling its JAV5001, a 3G UMTS band I PA that integrates circuitry for power regulation, PA bias, input/output matching, and power control on a single CMOS die (see figure). "By achieving compliance to the stringent 3GPP specifications for WCDMA and HSPA, this breakthrough is expected to initiate the long-anticipated shift in wireless PAs from GaAs to CMOS," asserts Patrick Morgan, Javelin's Vice President of Marketing.
Housed in a 3-x-3-mm package, the JAV5001 boasts low current consumption and low noise. Low average current of 27 mA is attributed to its patented bandpass architecture, which provides optimum performance at medium and low power levels in accordance with GSMA DG.09 specifications. The PA's noise performance is −150 dBc/Hz. Offering stability across output loads, the firm claims that the JAV5001's VSWR performance is superior. The PA is protected against open and short circuits while offering high electrostatic-discharge (ESD) immunity. Rated PAE in mid-band and maximum output power is 40 percent.
By leveraging its novel architecture, Black Sand unveiled its first 3G CMOS PA to the world last year. Now, the developer is in the process of implementing the control and power modes in silicon. Although the initial version is band- and modespecific, a multiband, multimode CMOS version is also on the drawing board. In addition, the developer has revealed that it has acquired a number of issued and pending CMOS PA-related patents from Silicon Laboratories.
To get a head start on the CMOS front, Skyworks acquired CMOS-based PA supplier Axiom Microdevices last year. Using Axiom's PAs, the maker has now released a complete CMOS-based front-end module for GPRS handsets.