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转:RFIC development flow from EDABOARD  

2008-12-09 16:04:33|  分类: IC design |  标签: |举报 |字号 订阅

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1. System Level Specification: The system-level specification is the first item in a typical RF-ASIC design flow (Figure-1) . One can use specification for wireless local area networkor bluetooth or some other parameters as an input for the start of the design. Given a broad specification like this one, there is a host of different ways to implement the system.

2. System Analysis and Architecture Choice: This is most critical step in RF ASIC design flow. It needs lot of analysis and research on different architectures. But now, since chips are so highly integrated and are, in reality, systems-on-a-chip, the IC designer must be involved at this level to ensure that optimal choices and proper trade-off are made in order for chips to be produced correctly. At this point in the design flow, We may use a combination of CAD tools (some system level simulators) and hand calculations to come up with the system analysis and architecture choice.

3. Chipset partitioning and chip level specifications: The architecture is then partitioned into separate chips. For instance, We may divide the architecture into transmitter chip and a receiver chip, or between a full transmit/receive chip that operates at the RF, and another chip that works at the intermediate frequency (IF). Another option is to split the functions among several chips. We will combine all the blocks to complete the design. Partitioning also involves technology selection — whether or not to utilize standard CMOS, bipolar CMOS (BiCMOS), or gallium arsenide. In most cases, CMOS is used for lower frequency, while higher frequency circuitry is based on bipolar processing. These trade-off are determined before actually starting the IC design. For this RF transceiver ASIC, BiCMOS or SiGe process may be better over CMOS technology.


4. Preliminary RFIC design topology trade off: By now, the system spec has been developed into a chip-level spec, and each block inside the chip is reviewed and analyzed for topology trade-off or for actual selection of the optimal topology. For example, there may be two ways to design a low-noise amplifier (LNA), and you’ll want to closely investigate both to achieve the best performance in this particular realm of the design.

5. Detailed Design Phase: The detailed design phase is the point where 90% of the work is done to make the IC a reality. Include all the parasitic of the design, package models, and all models of the IC. The design is simulated over the specified temperature range and worst-case process variations to make sure the design is centered and robust. Then, it’s time to move to layout. Due to the RF IC’s high frequency and high level of integration, there are crucial interactions between blocks, determined by how they are laid out and in what relative orientation. For this reason, this portion of the design is an art form. Currently, the majority of RF ICs continues to be laid out by hand; they are not auto-routed like large digital ASICs are. So a considerable amount of care must be taken, for example, in substrate connections and grounding. In higher frequency the metal layers connecting different blocks will be treated as transmission lines. Impedance mismatch should be taken great care for the layout. The detailed design schematic is converted into a physical implementation using technology files for the process.


6. RFIC Layout: Inevitably, there will be layout parasitics that can have an adverse effect on RF performance. Therefore, parasitic extraction is performed by calculating capacitance between nodes, parasitic capacitance, and resistance to the substrate. These are parasitics that couldn’t be predicted before layout.

7. Parasitic Extraction and simulation: The parasitic values are extracted using the design tool and are then inserted back into the detailed design schematics for a simulation to make sure the design is still centered and works over process and temperature variations. This represents the final simulation. The design as it is physically implemented is what is simulated, and this is the expected result after the device is tested.

8. Fabrication: After verifying the rule files provided by the vendor, The final layout to be given to the fab lab for fabrication.

9. Evaluation to Specification: This is one great exercise for a designer. We will compare between the simulated value and actual measured value. We can analyze the chip and will improve the design parameters in the subsequent stages

                                                                                              ---By Guru


测试是很需要技巧的,同一块板子,不同的PCB出来,不同的匹配网络,结果会差很多,因此要仔细调整。

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