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Reconfigurable analog baseband LSI tailored for SDR

Posted: 08 Feb 2008 ?? ?Print Version ?Bookmark and Share

Keywords:analog baseband LSI? software defined radio?

reconfigurable LSI

NEC Corp. and NEC Electronics Corp. have announced the development of a reconfigurable analog baseband LSI for software defined radio (SDR). The LSI is capable of filtering unnecessary signals in the frequency range of 400KHz to 30MHz, allowing it to simultaneously support multiple wireless standards for existing and future mobile system standards such as mobile phone, broadcasting and WLAN systems. Boasting a small chip area of 0.57mm?, the LSI can also change the type of filter depending on the wireless standard.

Conventionally, it has been difficult to incorporate SDR into mobile equipment since the existing SDR technology relied upon selective switching of transceiver devices, which resulted in a large mounting area of existing chips for each wireless standard. One of the key building blocks for our novel SDR transceivers is an analog baseband that includes tunable filters. NEC's slim, compact analog baseband LSI has been achieved by development of a pulse-width controlled reconfigurable filter for changing filter type and/or bandwidth.

Key features
The chip responds to tuned transmissions and rejects other signals within a broad bandwidth range of 400KHz to 30MHz, allowing support of mobile, WLAN, WPAN, broadcasting and GPS standards. It also realizes reconfigurability to enable several filter types, including Butterworth, Chebyshev and Elliptic. All of the filter types are achieved by a simple change in the pulse-width of the control signal, realizing a small chip area of 0.57mm?.

In recent years, the need for mobile terminals to support several wireless functions has been rapidly increasing with the progressive integration of information and communication devices. However, these mobile terminals need to be able to support multiple wireless standards without increasing die and/or mounting area. This need can be met by SDR transceivers as they can change the RF building-block function and receive the appropriate wireless standard signal just by a simple change in software. One of the key building blocks for SDR transceivers is an analog baseband that enables changes in filter characteristics, such as bandwidth, and selectivitythe ability to respond to tuned transmission and reject other signalsto meet specific application requirements. However, it is difficult to realize a wide tuning range (e.g. two orders of magnitude in bandwidth) or to reconfigure selectivity, such as filter type, with conventional filter technology. Therefore, it has conventionally been necessary to arrange filter circuits side by side and switch from one to the other to achieve several types of filter characteristics in a single chip, hence the current large chip size.

NEC and NEC Electronics have been actively carrying out research and development to solve the issues of circuit size and reconfigurability. The reconfigurable analog baseband LSI is extremely small, making it fit for use in mobile equipment, says NEC.

This research result can also be applied to a single RF chip to support any wireless standard. NEC and NEC Electronics will continue to actively pursue research and development in this area toward early realization of multi-standard mobile equipment, essential to a ubiquitous networked society.

The results of the research were presented at this week's International Solid-State Circuit Conference.

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