The challenge of multi-band, multi-mode: The proliferation of new standards and frequency bands places great challenges on the RF designer. Each frequency band requires its own signal path and each new standard has its own set of requirements on the RF front -end.
Figure 1: Typical Current RFE Implementation
Whether you are designing a TDMA – or FDMA-based system such as GSM EDGE or a system that is based on CDMA technologies such as W-CDMA, CDMA2000 or LTE, the basic problem remains; your radio design has to work with many different wireless standards implemented on as many or more different frequency bands. In addition, future systems will also use advanced techniques such as antenna diversity and MIMO (Multiple In Multiple Out) to enhance data throughput. For a complete diversity function the receiver needs to have a separate RF chain for each of the antennas, again driving front end complexity.
The preferred implementation to date has been a combination of parallel front-ends and several broadband antennas combined with switching arrays to select the desired signal path. Active devices have traditionally been standard specific and separate since a CDMA based design requires higher linearity than a system based on GSM, where the power amplifier is used in a deep saturation mode.
While this approach has worked in the past, it is going to be increasingly difficult and inefficient to implement as the number of wireless standards continue to grow and new frequency bands are introduced along with the requirement for antenna diversity. In order for integration to continue, signal paths have to merge and active devices have to become more flexible both in terms of frequency and mode of operation.
The signal path duplication increases both the size and the cost of a typical multi-band, multi-standard phone. There is no inherent reason why RF-parts have to be static, as they are today, because the enabling technology for dynamic RF functions has not been available in silicon. WiSpry replaces duplication with signal chain adaptability, using tunable digital capacitors.
Figure 2: WiSpry Roadmap to a Fully-Integrated Tunable Mult-band, Multi-mode Front End
A software programmable signal chain approach changes the very foundation of RF design. Not only can the designer re-use the same components for all the different modes of operation, thereby saving both space and cost, but it also becomes possible to design with far fewer switches in the signal chain. Fewer switches means lower insertion loss which translates into increased RF performance, longer battery life and fewer dropped calls in the network.
In addition, new attractive functions such as automatic tuning for optimum performance in the network and frequency agile antennas can be added and maintained by the network operator through software updates, in the field.
WiSpry recognizes that technology must be affordable. WiSpry’s innovation is all developed on a CMOS standard flow process. This enables the system designer to add functionality and reduce parts count, with little or no impact to the BOM cost.
The future of RF starts with WiSpry’s tunable RF.
WiSpry: we make wireless work…better!
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