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 and antenna.
Whether you are designing a TDMA / FDMA-based system or one 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 receive diversity and MIMO (Multiple In Multiple Out) for LTE 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 higher.
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. A flexible tuning capability resolves a number of these issues. There is no longer an inherent reason that RF-parts have to be static, as they have been. Until now, the enabling technology for dynamic RF functions has not been available in silicon. WiSpry replaces this signal chain 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 programmable signal chain approach changes the very foundation of RF design. Not only can the designer re-use the same components for all of the different modes of operation, thereby saving both space and cost, fewer switches are needed in the signal chain. Fewer switches means lower insertion loss and that 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. The RF chain can even be updated in the field with new features and maintained by the network operator through software updates.
WiSpry recognizes that new 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.
