SzRR Broadband Radio Communications Recorder designed by the KenBIT company is a good example of the abilities possessed by the Polish industry, working in collaboration with the Polish research facilities and the National Centre for Research and Development, to create an unique product meeting the requirements of the telecommunication services market for the demanding users.
The SzRR Broadband Radio Communications Recorder, used to monitor the radio bandwidth communications, has been created by a consortium, formed by the following entities: KenBIT company (leader), Office of Electronic Communications, and Faculty of Electronics of the Warsaw University of Technology. The work was taking place within the framework of development project no. 4/2013, with financing in an amount of PLN 11.5 million provided, at the end of 2013, by the National Centre For Research and Development.
As a result of the aforesaid collaboration, an operational system has been created, allowing the user to monitor, at once, a broad range of frequencies (up to 500 MHz) and to analyse numerous signals received at once, even if they are recorded within discriminate, largely differing frequencies. The ability to record also allows the user to go back to the emissions being of interest, that were impossible to intercept at the moment when they were being actually received, e.g. due to the fact that the operator was involved in another procedure.
This is thus a perfect solution for electromagnetic emission monitoring systems controlling the way in which the available frequency ranges are used by the users responsible for frequencies management and for control of the requirements related to electromagnetic compatibility.
The SzRR recorder shall also be viewed as an ideal fit for military-grade SIGINT systems that are dealing with professional surveillance and analysis of electromagnetic signals. Currently, in order to cover the whole usable range of frequencies, it is often required to make use of multiple narrow band receivers, with numerous operators being involved in the process.
Moreover, one should also remain aware of the fact that not only can the SzRR system be used as a real time radiocommunications recorder, as the suite could also be utilized as a subsystem for analysis and visualization of the recorded signals and as a radio receiver with specifications including parameters that are not frequently witnessed in case of other similar devices. It turned out that a recorder has been designed, that can be operated within a bandwidth that, at the moment, remains inaccessible to any of the readily available pieces of radio hardware on the market (offering bandwidths ranging from couple to several MHzs).
It was decided to create a unique receiver system then. Thanks to the aforesaid approach, SzRR system has been created, enabling the user to monitor and record continuous radio signals within a band with breadth of up to 500 MHz, in V/U/SHF frequency ranges.
The task assigned to the receiver package is to acquire the radio signal and process it into a digital form, making it possible to record the signal in a lossless form afterwards. The package is available in “0-IF” (direct processing) and “IF” variants. The two variants were required as due to the fact of technology limitations, one system allows for obtaining a greater bit-resolution, with the other one providing a greater sampling frequency (GS/s).
The analogue portion of the receiver tract in both systems is tasked with selection, amplification and conversion of the given frequency range for the purposes of carrying out the AD conversion.
In case of the “0-IF” version a homodyne receiver was created covering the bandwidth between 1 and 6 GHz, with a system featuring a “single analogue quadrature processing and with the use of dual-channel AD 14-bit converter operated at a sampling frequency of 1 GS/s”. Developing of a proper amplifying system and control of non-linear distortion introduced by the individual blocks of the suite was recognized as the greatest challenge which needed to be met to, “by the means of intentional amplification adjustment, provide the most optimal signal acquisition and prepare the signal for further processing”.
In case of the “IF” receiver, a system has been developed to replace the analogue quadrature processing with an entirely digital system, with the “quadrature processing taking place digitally in a FPGA system”. The aforesaid digital solution is destined for further distribution of the signal/data via separate optical ethernet links. Meanwhile, the AD converter is a single-channel system with a resolution of 12 bits (lower than in case of “0-IF”), with a sampling rate of 3.6 GS/s (higher than in case of the “0-IF” set-up).
The transmission of signals and data to the broadband recorder from the AD converter of the receiver takes place over an Ethernet network at transfer speeds of up to 40 Gbit/s. In order to ensure continuous data recording in real time, KenBIT software-using servers based on the Linux OS have been used. Each of the said servers remains capable of recording data streams at speeds of up to 800 MB/s.
The system management software includes a database for saving the information allowing “both for identification of a single recording (parameters, acquisition status etc.), as well as for signal sync and reconstruction”.
A highly efficient broadband switch is the element that acts as the intermediary segment between the receiving set and the recorders. Its role is to separate the data stream for being recorded by the individual servers, as well as to convert the signal to be transmitted from fibre optics to copper links, depending on the data transmission speed requirements.
Signal Visualization and Analysis System
The recorded data remains available for being scrutinized within the dedicated external analysis systems operated in real time. The operators of such systems may select the recording of the specific signal and, utilizing a special purpose software package, visualize a spectrogram of the indicated signal, presenting the said signal in a time/frequency setting. Obviously, the operators may also access other visualization settings and tools that would allow them for selective time/band analysis of the signal.
Search for the emissions that remain interesting for the user may also take place automatically, e.g. through a system for automatic search with predefined parameters. The results of such analysis are than saved in the database and visualized, frequency-wise on a spectrogram, as well as in a table.
The above article has been written on the basis of information provided by the KenBIT company.