Filter is reconfigurable RF spectrum channeliser

RF Engines (RFEL) has developed a radical new patented filter bank design, called the Tuneable Pipelined Frequency Transform (TPFT).

RF Engines (RFEL) has developed a radical new patented filter bank design, called the Tuneable Pipelined Frequency Transform (TPFT).

The TPFT allows the user to dynamically select sections of spectrum (channels) of differing bandwidths, from a broad band of spectrum, and to acquire and process these channels in real time.

Furthermore, the design disregards the processing of those sections of spectrum that are not of interest, so improving the silicon efficiency even further.

The TPFT architecture has been developed by building upon RFEL's own Pipelined Frequency Transform design, and is aimed at those applications that require flexibility in frequency channelisation, but also real-time reconfiguration to different frequency plans.

The TPFT is targeted at a range of applications where reconfigurable front ends are required, from wideband multistandard receivers (such as satellite earth station receivers, basestation receivers and reconfigurable radio systems) through to instrumentation.

It is aimed at those applications requiring the channelisation of wideband signals (80MHz) into different size frequency bins arbitrarily distributed across the input spectrum.

The TPFT gives the users the freedom to tailor the design to their requirements, and allows them to specify channels by centre frequency and bandwidth, to fully define the filter characteristics, and to then reconfigure in real time to a different frequency plan or plans, as required.

Furthermore, spectral shaping masks can also be directly applied onto the outputs within the architecture itself, so allowing even the final filter shapes to be finely tuned to the needs of the application.

The underlying concept of this architecture is that of successive band splitting in a pipelined manner: at each stage, the input spectrum is split in multiple channels.

A first stage splits the input in two frequency bands, a second stage into four, and so on.

Tuneability is achieved by controlling the channelisation process from outside the TPFT itself, thus allowing reconfiguration on demand.

A PC Windows based graphical user interface (GUI) controls the architecture, modifying the required parameters as required, although the development of a self-contained SoC architecture is also under consideration.

The TPFT has been developed as an alternative to standard digital down convertor (DDC) techniques and offers significant advantages in terms of silicon usage.

The architecture is highly pipelined, thus it is best suited to target devices such as FPGA or ASIC.

The latest generation of FPGA devices from the likes of Xilinx, Altera, etc allows very complex DSP architectures such as the TPFT, to be implemented on single mid-range FPGAs.

Furthermore, with the introduction of system on chip (SoC) capable devices (such as the Xilinx Virtex-II PRO), the whole system, ie filter bank and controls, can be implemented on a stand-alone platform.

A typical TPFT implementation would consists of 10 pipelined stages, providing in excess of 800 usable frequency channels at the finest frequency resolution (in this case a 1024th of the input bandwidth) or fewer channels if wider frequency bins are also required.

The TPFT can be customised to accommodate for customers needs, leading to optimal tailored solutions: a TPFT design could perhaps compromise on tuneability where a frequency plan is fixed, leading to an even more compact implementation.

For the real-time processing of uneven channels and for on-the-fly reconfiguration, the TPFT architecture provides significant advantages over more conventional methods of frequency splitting, such as complex down converters, or even less flexible frequency transforms such as the discrete Fourier transform (DFT) etc.

Overall, the TPFT fills the gap between the comparatively inflexible FFT or PFT approaches and the use of DDCs, which is extremely flexible but becomes increasingly inefficient above a certain number of channels.

The TPFT provides a highly flexible and efficient means of frequency channelisation, which is fully reconfigurable within its hardware frame.

A software model of the TPFT is available for system engineers.

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