NEC has come up with a reconfigurable analogue baseband IC for Software Defined Radio (SDR), achieved by the development of a pulse-width controlled reconfigurable filter for changing filter type and/or bandwidth.
The 0.57mm2(super) chip filters 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 wireless LAN.
It can change the type of filter depending on the wireless standard.
The difficulty of incorporating SDR into mobile equipment stems from the conventional reliance on the selective switching of transceiver devices, which results in a large mounting area of existing chips for each wireless standard.
Tunable filters
One of the key building blocks for NEC's SDR transceivers is an analogue baseband that includes tunable filters.
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.
Mobile terminals need to be able to support multiple wireless standards without increasing die and/or mounting area.
This re quires SDR transceivers as they can change the radio frequency (RF: 24.24, -0.86, -3.42%) building-block function and receive the appropriate wireless standard signal by a software change.
SDR transceivers need an analogue 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's research into highly integrated reconfigurable can also be applied to a single RF chip to support any wireless standard.