Design tool automates a common environment for RF and mixed signal
16 May 2008
As the RF element in mixed signal PCB design increases, two of the lead companies in both areas of expertise have collaborated to deliver a common design tool to open up communication between the two design camps.
Agilent Technologies (www.agilent.com) has 62 per cent RF design and simulation tools market share and Mentor Graphics (www.mentor.com) has 34 per cent of the PCB EDA market, according to analyst company GarySmith EDA. For two years, the two companies have been working on the RF Design Tool which is now available to both sets of customers for around $9,000 to add to Mentor’s Expedition Enterprise or Board Station XE and to Agilent’s ADS (Advanced Design System). Now, system designers can concurrently build a PCB using Mentor design flows and seamlessly integrate it with Agilent’s ADS software for RF design and simulation.
RF is now used in multi-layer boards in communications applications. PDAs and other handheld communication products, basestations and automotive radar sensors for reversing are all designed by analogue and digital design teams, which work separately from the RF designers. Mentor’s John Isacc, describes as an ‘over the wall’ approach, where two teams operate independently, often manually passing data back and forth for revisions and respins.
Isacc refers to the RF design option as ‘dynamic integration’ with synchronised libraries and databases for analogue and digital and RF designers to share. The EDA company has added RF understanding from both schematic and metal viewpoints. RF circuits can be designed directly in Expedition Enterprise or Board Station XE or transferred from Agilent ADS using a dynamic link. True RF schematics are now at system-level design with commonly used elements so that the RF design does not have to be translated. The library is synchronised with circuit-simulation model counterpart in the RF simulation environment for identical behaviour in both ‘camps’.
Schematic entry and RF circuit layout can be started in either environment with the RF simulator supplying the simulation, tuning and optimisation capabilities. The complete circuit is transferred via the dynamic link to the RF simulator. By transferring only what the RF simulation needs rather than the whole design eliminates error prone translations.
Previously RF circuits were treated as metal in the board design. Now, but with RF understanding, the shapes can be parameterised and synthesised. For example, via stitching can be sent to Mentor for the sparameter model to simulate how it will act on the board in isolation without translation. Similarly multi-layer boards’ metal can be viewed in 3D for vias checking before layout.
The auto-arranger can handle partial selections from an RF circuit or arrange the full circuit. RF shape connection can be micromanaged and connected at different angles. Similarly, RF circuits can be grouped so the circuit stays intact on the main system board. They can also be divided into groups for partial simulations or to protect parts of the circuit. Non-RF objects, like high-speed traces, plane shapes or cut-out can be added into the RF groups.
Meanders can be added at any stage to connect elements. The meander can be broken down into elements and simulated in a circuit and sent over the dynamic link as layout for electro-magnetic simulation.
For electro-magnetic simulation, grids can divide the design so that parts can be simulated for RF performance. The frequency response of the circuit can be viewed, for the environment to act as an analyser or oscilloscope to see the response of the metal and save board spins and respins. The common libraries can check core components and the engineer can use it to see spectral components and add markers or view in the time domain as if probing with an oscilloscope before building the hardware.
In addition, the surface current can be viewed across the metal to see where coupling may occur pinpointing, rather than indicating, areas to be altered.
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