NEC Develops Reconfigurable Analog Baseband LSI for SDR

NEC Corporation and NEC Electronics Corporation announced the successful development of a reconfigurable analog baseband LSI for Software Defined Radio (SDR). The newly developed LSI is capable of filtering unnecessary signals in the frequency range of 400 KHz to 30 MHz, allowing it to simultaneously support multiple wireless standards for existing and future mobile system standards such as mobile phone, broadcasting, and wireless LAN systems. Boasting a small chip area of 0.57mm2, the LSI can also change the type of filter depending on the wireless standard.

NEC Reconfigurable Analog Baseband LSI for SDRConventionally, 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 the novel SDR transceivers is an analog baseband that includes tunable filters. The new slim, compact analog baseband LSI has been achieved by development of a pulse-width controlled reconfigurable filter for changing filter type and/or bandwidth.

Features of the new LSI

  1. Responds to tuned transmissions and rejects other signals within a broad bandwidth range of 400 KHz to 30 MHz, allowing support of mobile, WLAN, WPAN, broadcasting and GPS standards.
  2. 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 0.57mm2.

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 the die and/or mounting area. This need can be met by SDR transceivers as they can change the radio frequency (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 selectivity—the ability to respond to tuned transmission and reject other signals—to 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 new reconfigurable analog baseband LSI is extremely small, making it ideal for use in mobile equipment.

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 this research were presented on February 4 at the International Solid-State Circuit Conference (ISSCC) 2008, being held February 3 to 7 in San Francisco, California, U.S.A.

About NEC Corporation
NEC Corporation is one of the world’s leading providers of Internet, broadband network and enterprise business solutions dedicated to meeting the specialized needs of its diverse and global base of customers. NEC delivers tailored solutions in the key fields of computer, networking and electron devices, by integrating its technical strengths in IT and Networks, and by providing advanced semiconductor solutions through NEC Electronics Corporation. The NEC Group employs more than 150,000 people worldwide.

About NEC Electronics
NEC Electronics Corporation (TSE: 6723) specializes in semiconductor products encompassing advanced technology solutions for the high-end computing and broadband networking markets, system solutions for the mobile handset, PC peripherals, automotive and digital consumer markets, and platform solutions for a wide range of customer applications. NEC Electronics Corporation has 25 subsidiaries worldwide including NEC Electronics America, Inc. and NEC Electronics (Europe) GmbH.