Three-Chip GSM Front-End Solution Pairs TriQuint’s New Quad-Band Filter Bank

x_jwen

November 2004
Three-Chip GSM Front-End Solution Pairs TriQuint’s New Quad-Band Filter Bank & Transmit Module With Leading OEM Transceivers
by TriQuint Semiconductor
Using modules to eliminate and combine discrete components remains a key aspect of GSM handset evolution. Design cycle times, performance, feature requirements, hardware form factors, quality and cost targets remain the dominant selection criteria for mobile phone designs. Recognizing these needs, TriQuint has released a portfolio of RF receive (Rx) and transmit (Tx) GSM module products to address the increasing expectations of next-generation cellular phone designers. When used in combination with a variety of leading handset transceivers, TriQuint’s modules offer a three-chip solution for RF front-end design.

Quad-Band Filter Bank Module
TriQuint recently introduced a new family of receive filter banks designed for global GSM/GPRS/EDGE handset manufacturers incorporating the latest advancements in surface acoustic wave (SAW) filter technology. The SAWs in these new products provide unprecedented insertion loss compared to alternative solutions while offering the world’s smallest chip scale footprint. Ideally suited for integration into a compact RF module, the new filter banks provide cost efficiencies and circuitry matching abilities discrete solutions can’t offer.
Quad-band Transmit Module [TQM6M4001; TQM6M4002]
These highly integrated modules incorporate all RF transmit functions for GSM/GPRS between the transceiver and the antenna into the market’s smallest form factor device – 6x6x1.1mm – offering a 35% size reduction compared to competing solutions. Their smaller size and high-level integration make the new TQM6M4001 & TQM6M4002 transmit modules a marketplace breakthrough. The modules require no external matching and save customers the need for any PA-to-switch design effort. This significant form factor advancement (6x6x1.1mm) was achieved by eliminating all surface mount devices (SMDs) inside the laminate-based module, resulting in clear size, cost and time-to-market advantages.

Figure 1: Optimized, 3-Chip RF Radio In-Line Design
TriQuint has provided the GSM handset industry with a highly integrated and simplified RF Front-End. Taken together, the new filter bank and transmit module provide all functions between the transceiver and the antenna in the market’s smallest form factors. As seen in Figure 1, next generation transceiver chips have integrated much of the RF section into a single CMOS device. Creating the remaining RF section depends on leading HBT, pHEMT and SAW technologies. These areas are the core focus of TriQuint’s strategy and are designed to achieve optimal system performance in next generation mobile multimedia applications (e.g. combining UMTS / GSM and GPRS / WLAN / GPS in one phone). TriQuint has reduced design complexity and component size to develop highly integrated RF modules that address the increasingly sophisticated demands of the GSM marketplace, as demonstrated by the three-chip front-end solution diagram also illustrated in Figure 1.

Figure 2: GSM1900 (PCS) SAW Filter - Low Loss Filter
TriQuint’s new family of quad-band filter banks, designed by its Sawtek Division, support all GSM bands, as do its matching transmit modules. The filter banks target key GSM transceiver chipsets with design and production methodologies based on TriQuint’s successful line of GSM filter modules already in use by worldwide OEMs.

Figure 3: GSM1800 (DCS) SAW Filter - Low Loss Filter
The Figures 2-5 offer performance details of the latest in advanced surface acoustic wave (SAW) filter devices:

TriQuint’s GSM/GPRS/EDGE filter bank integrates four receive SAW filters and all matching circuitry required to optimize impedance between the filter module and transceiver. This quality deliberately exceeds the expectations of past design methodology that placed matching circuitry external to the SAW device, leaving the task of optimizing SAW and transceiver impedance to the phone designer. Instead, TriQuint actively partners with major transceiver manufacturers to fully optimize system performance, providing design engineers with guidelines and procedures necessary to achieve the desired results. This highly optimized product provides handset designers crucial time-to-market advantages.

Figure 4: GSM900 (EGSM) SAW Filter - Low Loss Filter
TriQuint’s filter bank helps handset designers minimize part count, eliminate on-board matching, reduce size and optimize system performance. In the past, a designer would use four SAW filters with 2-3 matching components for each filter, resulting in 8-12 surface mount devices (SMDs). Assuming the use of standard discrete Rx chip scale package (CSP) SAW dimensions of 2.0x1.5mm, and standard “0402” passive matching components, the discrete solution could demand nearly 43mm2 of valuable PCB area. TriQuint’s new family of matched filter banks achieve the same performance while occupying less than 25mm2 of PCB area, an amazing 42% reduction in premium board space. Filter banks in production today are 7.0x3.5mm, while future packaging capabilities will allow these modules to shrink further to only 6.0x3.5mm - 21mm2.

Establishing a new milestone in high-level integration while ideally complementing the quad-band filter bank are the TriQuint TQM6M4001 & TQM6M4002 - next generation GSM / GPRS quad-band transmit modules. TriQuint utilized in-house 150mm GaAs processes including GaAs InGaP HBT and GaAs pHEMT for the PA, LPF and switch circuits (respectively). A dedicated GaAs-based process was also developed and implemented for high level ESD protection. All control functions for the PA and switch are incorporated into a proprietary CMOS design. Both modules leverage the discrete GSM850/900 and DCS1800/ PCS1900 PA blocks and integrated power control found in current generation power amplifier modules. Taking integration to a new level is the addition of a low insertion loss quad-band pHEMT switch, Tx harmonics filtering, an integrated switch decoder, four non-selective receive ports, and full ESD protection - all necessary to implement total RF transmit functionality, and all in an unprecedented size of 36mm2. TriQuint also utilizes an SP6T pHEMT switch architecture instead of a solution that uses an SP3T switch and a diplexer. Using the SP6T design not only simplifies module architecture, it also results in improved insertion loss between the antenna port and the SAW filter bank input. When the SP6T is combined with a low loss quad-band filter bank, the noise level in front of a transceiver input is greatly reduced while also providing the handset with higher sensitivity.

Figure 5: GSM850 (EGSM) SAW Filter - Low Loss Filter
The transmit module is laminate-based and all die are connected through wire bonds. TriQuint was able to achieve its industry-leading size reduction by using integration to eliminate all interior matching and biasing surface mount device (SMD) components. The fundamental advantage of this transmit module is its built-in PA-to-front-end interface, which eases the design process for handset engineers. By combining PA and antenna switch functionality into a single module, one part may now be used for multiple applications, thus significantly simplifying the component qualification process, bill of materials (BOM) and supply chain management.

Figure A: TQM6M4001 & TQM6M4002 performance data in GSM 850/900 band

Figure B: TQM6M4001 & TQM6M4002 performance data in DCS/PCS band

Figure C: TQM6M4001 & TQM6M4002 DC performance
The Figures A & B & C detail typical TQM6M4001 / TQM6M4002 performance:

The TQM6M4001 & TQM6M4002 transmit module architecture and interface are optimized for next generation quad-band transceivers and assure optimal line routing on the phone PCB level. Combining the transmit module with TriQuint’s quad-band GSM receive filter bank and a corresponding transceiver achieves a three-chip RF radio. In this design, four broadband and frequency independent Rx ports simplify development of a PCB radio design that is free from RF line crossing for most leading transceivers in use today.

The transmit module and its companion GSM quad-band filter bank are also significant ‘value-added’ products in that they also simplify purchasing and inventory management. Buying integrated modules simplifies the purchasing process by allowing a manufacturer to work with fewer suppliers. In turn, stock is also easier to manage, resulting in a reduction of “stranded inventory.” For manufacturing, fewer components are handled, therefore reducing the number of items that need to be issued to the production floor. Add the value of shifting a yield burden to the supplier and choosing a filter bank / transmit module pair instead of a host of discrete components becomes a quantifiable ‘value proposition’ in the truest sense.

TriQuint Semiconductor offers a wide variety of GSM products for the multi-mode, multi-band phones in today’s worldwide markets including the individual products needed to create GSM front-end modules for three-chip RF radio solutions. This technology portfolio will enable mobile handset design evolution to continue, resulting in even greater integration and modularization of the RF front-end.
TRIQUINT SEMICONDUCTOR
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