Philips Semiconductors is the third largest supplier of semiconductors for the global multimedia and telecommunications markets. Its facility in Caen, Normandy, France, is a world leader in the design and production of microelectronic components for the digital media, optical networks, and telecommunications industries.
A particularly important market for Philips Semiconductors is RF ICs (Radio Frequency Integrated Circuits) for mobile telephony and data communications. This market is booming - from cordless phones using the DECT protocol to second-generation mobile phones using GSM, through GPRS and EDGE (2G+), to third-generation (3G), W-CDMA and UMTS devices, and beyond to the future generation of wireless connections using Bluetooth* technology in the 2.4 GHz ISM band.
To meet the needs of their telephony customers, the designers at Philips Semiconductors were faced with the problem of controlling analog, digital and RF signals in very high-density circuits. For example, integrating bipolar transistors alongside passive components and high-speed CMOS logic introduces significant uncertainty in the operational behavior of the circuits. Conventional simulation tools are not up to the task.
Philips Semiconductors designs its ICs using its advanced QUBiC BiCMOS process family. "The QUBiC family is ideal for integrating functions such as VCOs, synthesizers, mixers, LNAs, filters, and RF power amplifiers into single-chip RF solutions," explained Jean-Pierre Manhout, senior RF designer at Philips Semiconductors. "But simulating these circuits, particularly under the conditions in which RF transistors operate in a power amplification regime, can take so much time using conventional simulation tools that it is difficult to iterate the design enough times to create right-the-first-time silicon."
Philips Semiconductors has overcome this problem by taking advantage of the Agilent Advanced Design System (ADS) software to speed up simulation of both steady-state and transient conditions in RF circuits.
Philips Semiconductors particularly appreciated the ease with which it was possible to integrate Philips' own state-of-the-art MEXTRAM models for RF bipolar transistors into the system. Within a few months, the whole library of models was inserted, and the complete solution became operational during 1999. ADS is now totally integrated into the design and manufacturing process.
New designs are fine-tuned and re-simulated to a much greater extent than was previously possible, particularly under the specific RF modulation and pulsed power conditions that exist in the end application. Using Philips own MEXTRAM models for RF power transistors also means that power amplifier functions can be simulated with unprecedented accuracy.
Early tests of ADS from Agilent Technologies proved the value of the system. "As a result of using Agilent ADS with MEXTRAM models, we have been able to refine the performance of an all-silicon 500 mW DECT pulsed power amplifier to the point where we are achieving typical power-added efficiencies of 50% under real DECT pulsed power conditions", said Manhout. " That's comparable to GaAs performance but at a considerably lower system cost and complexity."
ADS has also dramatically reduced simulation time for the validation of the newly designed circuit - by ten times compared with other simulation programs, say the Philips designers. This means that even in the fast-moving world of mobile telecommunications they have the time to fine-tune the parameters, multiply the number of tests, introduce new variations, try new processes, and - by successive iterations - imagine and develop real innovative products.
But the major advantage of the Agilent ADS system is the accuracy of the simulation. The results measured on the real product conform extremely closely to the outputs of the model simulation. "It is the exceptional reliability of the system which has convinced us," declared Manhout.
In addition to simulating the performance of complete RF chips, Philips Semiconductors is also using Agilent ADS to develop new IP blocks for RF ASIC design. Here, the increased level of simulation that has become possible is helping to ensure the very high level of circuit characterization required for effective IP re-use.
- Bluetooth(tm) is a trademark of Telefonaktiebolaget L M Ericsson, Sweden and licensed to Philips Semiconductors.
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