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  • AN ULTRA-LINEAR SP7T HANDSET ANTENNA SWITCH FOR GSM/PCS/ EDGE/WCDMA APPLICATIONS I ndustry standards bodies — such as the continues to grow, however through consoli- 3GPP Standards organization governing dation now fewer companies compete for a global cellular networks such as GSM, larger share of the integrated design. PCS, EDGE and WCDMA — are traditional- At the “RF front end” of the cellular hand- ly chartered to create a stable business envi- set, the antenna switch module (ASM) and ronment for advancing technology in a com- power amplifier (PA) module have advanced petitive market. These industry standards — on a steep learning curve due to the well de- as simple as the pitch of a PCB or as influen- fined expectations of handset manufacturers. band and were 5.5 × 10 mm. Today’s ASMs — tial as the premise of Moore’s Law — offer The initial ASMs supported a single frequency suppliers an equal opportunity to compete, and provides an industry the best chance to 81 percent smaller than their predecessors — grow and prosper. Additionally, industry stan- are tasked to support four bands with signifi- dards enable well-defined product roadmaps, cantly better RF performance, and to fit in 3.2 which in turn set clear objectives for rapid mm2. Complexity is at an all time high, and technology advancement using focused re- the learning curve has hit an inflection point. sources. Without achievable directives, an in- The number of variations and the lack of dustry stagnates as misaligned resources and GSM/WCDMA architectural, functional and product roadmaps reach a dead-end. mechanical standards has stalled advance- The cellular phone industry enjoyed well- ment. As well, the number of frequency bands defined guidelines for performance and and the aggressive technical requirements of mechanical footprint during the transition the multi-mode, multi-band GSM/WCDMA from analog to Second Generation (2G and 2.5G) standards. Today’s 3G environment, PEREGRINE SEMICONDUCTOR CORP. however, is more complicated. The market San Diego, CA Reprinted with permission of MICROWAVE JOURNAL® from the December 2005 issue. © 2005 Horizon House Publications, Inc.
  • P RODUCT F EATURE cept is +68 dBm at 50 Ω and its IMD3 is –111 dBm (with +20 dBm Tx and tion, until now. At the European Mi- crowave Conference (EuMC) in Paris, France, Nokia presented a pa- –15 dBm blocker signals). RX1 RX2 per addressing its quest to integrate into a single radio architecture.1 The STATE-OF-THE ART HARMONICS (WCDMA, TRX1 Peregrine PE42660 SP6T switch, de- Harmonic performance of the RF RX) RX3 signed in Peregrine’s UltraCMOS™ switch is a critical element of the an- (WCDMA, RX) (GSM/PCS) process with HaRP™ technology, was (GSM/PCS) tenna switch module. Typical switch TRX2 TX1 identified as a high throw count technologies such as PIN diode and switch that meets the linearity re- GaAs pHEMT provide only 6 dB of standard: an IP3 of +65 dBm. Typical quirements defined by the 3GPP margin, requiring up to three or four TX2 CMOS Control/ Driver design iterations to match the LTCC have IP3 of only +57 dBm. And now, and ESD SP6T/SP7T GaAs pHEMT switches to the switch before hitting the speci- V1 V2 V3 power of +35 dBm, the HaRP- fication. At the maximum operating v Fig. 1 The PE42671 SP7T switch. Peregrine’s newest HaRP-enhanced PE42671 SP7T switch provides for enhanced UltraCMOS switch deliv- dual WCDMA bands and a quad- ers –50 dBm P3fo, which is 20 dB of RX1 ANT RX2 band GSM radio to be connected to a margin to the GSM specification of precedented +68 dBm IP3. GND GND single antenna, delivering an un- –30 dBm. The second harmonic is TRX1 RX3 fundamentally low in UltraCMOS GND technology because distortion is sym- TRX2 PE42671 – TRUE MULTI-BAND metric on positive and negative volt- GND PERFORMANCE age swings. In the GSM system, this The PE42671 SP7T switch inte- very low even-order distortion for the 1680 m ANT µ GND GND grates one or two WCDMA and three second harmonic is desirable because TX2 or four GSM frequency bands (see the second harmonic of the GSM unprecedented linearity (IP3 = +68 Figure 1). Its four transmit ports with transmit band falls in the DCS re- TX1 ceive band. The less than –50 dBm GND dBm) allow for spec-compliant hand- second-harmonic performance allows GND sets and efficient front-end architec- for less noise transmitted in the DCS tures. Beyond linearity, the PE42671 band and increased system capacity GN VDD V1 GND V2 V3 GND µ switch also provides significant design for the carrier. value over other technologies such as 1260 m PIN diode and pHEMT configura- ULTRACMOS PERFORMANCE v Fig. 2 PE42671 die top view. tions. Small size and versatile layout, as ADVANTAGE shown in Figure 2, enable the applica- UltraCMOS is a standard CMOS handset have overcome the limits of tion designer to use the PE42671 processing technology, however as op- traditional RFIC technologies such as switch in extremely small RF modules. posed to building devices on silicon, a GaAs. Most critically affected by The SP7T switch is comprised of two conducting substrate, it places devices these ultra-high performance specs transmit ports that can be used for directly on top of a sapphire substrate. are the antenna and the RF switch. GSM/PCS/EDGE, two transmit/re- The perfectly insulating sapphire allows The antenna must effectively radiate ceive ports that can be used for either UltraCMOS to maintain all the positive from 800 to 2200 MHz, a daunting WCDMA or as receive ports and three attributes of bulk CMOS including low task given the miniscule area allowed symmetric receive ports. On-chip power operation, manufacturability, re- for the antenna. The RF switch must CMOS decode logic facilitates three- peatability, scaling properties and IP be capable of switching up to eight pin low voltage CMOS control, while block re-use, and to deliver the RF per- paths of high power RF signals with high ESD tolerance of 1500 V at all formance required for 3G applications low insertion loss, high isolation and ports, no blocking capacitor require- and beyond. exceptional linearity. ments and on-chip SAW filter over- To create a WCDMA/GSM hand- voltage protection devices make this Reference set that is spec compliant, handset device the ultimate in integration and 1. T. Ranta, J. Ellä and H. Pohjonen, “Antenna Switch Linearity Requirements for GSM/ manufacturers have been incorporat- ruggedness. The switch operates at WCDMA Mobile Phone Front-ends,” 8th Euro- ing separate WCDMA and GSM ra- 2.75 V over a frequency range of 100 pean Conference on Wireless Technology Pro- dio sections in one case — not a strat- ceedings, Paris, France, Oct. 2005, pp. 23–26. to 3000 MHz and offers low transmit egy any handset manufacturer would insertion loss of 0.60 dB at 900 MHz want on its roadmap for long. So and 0.80 dB at 1900 MHz. Tx-Rx isola- Peregrine Semiconductor Corp., while the industry has set its sights tion is 47 dB at 900 MHz and 40 dB at San Diego, CA (858) 731-9400, high, it has struggled to find a solu- 1900 MHz. Its input third-order inter- www.psemi.com.