Lime moves from SiGe to CMOS for its latest wideband CMOS software-radio chip

February 05, 2014 // By Nick Flaherty
Lime Microsystems hasd been proactive in pushing the conecpt of open-source hardware for RF; the same thinking has contributed to the definition of a wideband CMOS RF chip.

According to Lime's CEO, the highly integrated zero-IF transceiver has already been taped out in 65nm CMOS and runs from 50 MHz to 3.8 GHz. Machine-to-machine (M2M) designs are an important target market for the part.
The chip integrates 2x2 MIMO functionality and supports all cellular standards and frequencies, including 2G, 3G and 4G / LTE and their TDD / FDD variants amongst numerous other standards such as WiFi. This allows designers to make M2M and Internet of Things (IoT) equipment for global markets.
Lime’s first device was built in SiGe BiCMOS and the experience of making it available as part of an open source design through distributors such as Digikey and Richardson has given an insight into the additional functions that customers want.
“A whole host of novel platforms came out of the 6002 which really prompted us to cross migrate those flexibilities and go for further flexibility,” said Ebrahim Bushehri, CEO of Lime. “One of the key aspects of this kind of transceivers is you can capture a whole bunch of fragmented markets and when you look at the totality of the market the volume becomes quite interesting: just in the same way as the FPGA guys. And if any go into high volume we can respond and cost-reduce significantly. It also gives us early access to what is required in three or four years down the line.”
As a result the device features DSP functions, a microcontroller, multiple 12-bit ADCs and DACs, LNAs, filters, PLLs and mixers that can be accessed separately from the RF chain. These elements can also be used as cost-effective standalone parts and the open architecture allows each function to be accessed and used separately. The DSP enhances the analogue gain and filtering with digital control and is an important factor in reducing the overall power consumption.
“Staying true to bit-programmable RF we have brought a range of features from a range of