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Wednesday, November 19, 2014

 

Software defined radio in the battlefield: Multiband analogue front end brings one chip radio closer to reality

By Jonathan Cheng

From the soldiers in the field to the decision makers in the command and control centre, secure real time and accurate information is critical to any military campaign, facilitating strategy and tactical decision making. The network of advanced wireless communication technologies is a labyrinth of complex radio frequency (RF) and signal processing technologies, all working in harmony to produce a reliable communications network delivering information at the touch of a button. The history of military communications has been a proliferation of different incompatible radios, where a team may need units for airborne links, satellite communications, a base relay station and an emergency transmitter, as well as application specific roles such as for UAV operation. Each of these radio links serves a vital purpose and leaving one out of the mix would put the operational team at a disadvantage. Yet each radio carries a cost in size, weight and spare battery needs. The problem is further complicated as new requirements and links are added to the list. A universal full duplex radio module is required which can be used across all platforms and dynamically reconfigured in the field. This would lessen the load, provide flexibility and versatility, be efficient and provide longer operating life from a single set of batteries, all enabling significant SWaP (size, weight, power) advantages. But making the 'universal' radio concept into a reality has proven harder than envisioned and providing a suitable analogue front end (AFE) has been very difficult. Until recently, a practical AFE for this type of versatile radio required an array of overlapping parallel channels, each designed to cover a particular segment of the RF spectrum and with bandwidth matched to the intended signal format. This approach is costly in terms of final printed circuit board footprint, weight and power. Software defined solution A software defined radio (SDR) can accommodate various physical layer formats and protocols, encrypt data and convert analogue to digital with software running on a processor, making it perfect for military requirements. Users can control the frequency, modulation, bandwidth, encryption functions and waveform requirements dynamically. SDR also has the flexibility to incorporate new waveforms and functionality into the system without the need to upgrade or replace hardware components. These SDRs would be used not only by the soldier for data access and communicating back to the command centre, but also to create a wide area sensor/mesh networks for position/detection and communication among combat soldiers. The most important component in SDR is the transceiver, which needs to have an exceptionally wide RF range that can be tuned rapidly via software. It also needs to support frequency division multiplexing (FDD) and time division multiplexing (TDD), whilst having a high level of performance in terms of range and reliability, even under noisy conditions. At the same time, such a device should be able to operate under reduced power to minimise the drain on the soldier's battery pack. A highly integrated mixed signal RF IC would make broadband SDR designs smaller, lighter and less power hungry. But the real challenge is the extremely broadband nature of the AFE in the SDR; many spectrum specific front ends would be needed, each of which is a challenge to design and evaluate. Not only that, the final product would fall short in terms of SWaP.

http://www.newelectronics.co.uk/electronics-technology/multiband-analogue-front-end-brings-one-chip-radio-closer-to-reality/64097/