Cambridge, U.K.: Developed for military software defined radios (SDRs), the Modstar architecture from Cambridge Consultants requires less power while promising more efficient performance. It enables modules that can link multiple communications platforms in a lightweight device that’s more portable for troops than previous designs.
SDRs have long been used in military communications to connect various custom legacy radios that use a variety of air interfaces. For example, the Joint Tactical Radio System (JTRS) uses SDR’s ability to be reprogrammed from a high-level description of the new radio waveform to use new communications protocols.
The challenge lies in finding a practical implementation for SDR since demanding requirements often lead to complex power amplifier (PA), filtering, and antenna switching arrangements. For troops on the ground, this can mean bulky, heavy radio equipment that can only be moved in a vehicle.
Part of ModStar’s increase in portability is due to Nujira’s Coolteq envelope-tracking technology for PAs, which can extract double the power output from a given power transistor (see “Envelope Tracking Saves Smart-Phone Power” at engineeringTVcom). Coolteq minimises battery size, allowing smaller form factors.
ModStar also uses an open-loop polar modulator with non-continuous time feedback and software pre-distortion to achieve simpler radio design, with the most significant design challenges being moved into the digital domain.