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Avalon’s AE7000 High Performance Disk Recorder is an important development in the emerging trend towards scalable, ‘multi-technology’ data capture where wide bandwidth data is captured initially on fast disks before being edited for transcription onto low cost disk or tape media for analysis, archiving or onward
transmission.
Data is recorded onto a group of eight 36 GB disks giving the system a total capacity of 288 GB (2.2
Terabits) - almost double that of the largest ID-1 tape cartridge. The disks are housed in a shock-resistant, 'hot-swappable' crate which can be replaced in seconds or stored in a secure safe when not in use. The unit is controlled by four multi-function pushbuttons and a user-friendly graphical interface. Data can be output either in its original analog or digital form or automatically backed up to an integral Exabyte™ or AIT-2™ drive.
When integrated with a Windows NT Workstation as part of an Avalon AE7800 SIGINT Data Capture System, selected passages of data can be written directly to any networked disk or tape storage medium as computer-compatible files which are then immediately available for analysis or onward transmission. Long-term, unattended monitoring solutions are also
available.
Data interfaces include analog (DC to 20 or 50 MHz), digital (zero to 1 Gbit/s) plus a range of widely used telecommunication standards including: E1, E2, E3, T1, T2, ATM/OC3 (155 Mbits/s) and SONET/OC12 (622 Mbits/s). Other application specific interfaces are available either from Avalon or its qualified third party associates. 8-bit (45 dB) or 14-bit (70 dB) analog/digital conversion can be specified.
 The user interface is provided by a 170 mm (6.7 in) TFT color display
used in conjunction with four multi-function pushbuttons and a rotary digital encoder/enter button. Controls and status are also available using a standard computer keyboard and monitor. A complete on-screen HELP facility is provided.
The total disk capacity can be divided into one, two, or four logical partitions. Individual partitions can be locked to protect valuable mission data or on-board library information. As data is written to disk, it is time-stamped, along with any event marking and other ‘housekeeping’ information. A directory is held in a Flash-memory card which resides in, and travels with, the disk crate. If required, time-stamping to an accuracy of 100 ns can be
provided.
Text Annotation
During recording, this facility permits up to 32 characters of text annotation to be appended to data records using an optional external keyboard. During replay, the last relevant text annotation is displayed regardless of whether the playback process actually passed through the point where the annotation was originally made. This is a major advance on traditional voice annotation techniques which rely on the user locating and listening to the unique voice notes wherever they occur on tape. The message is attached to the data cluster which was active when the Annotation Mode was initially selected, even if the operator takes a few moments to type the note itself. For simple navigation of recorded data, the GOTO screen displays the text annotation relevant to the current cursor position along with all date, time, event and cursor position
information.
 Recording is as simple as pushing a single button. An ‘Event Marker’, incremented from the control panel (or remotely), allows passages of interest to be tagged for quick and easy location during
replay. Records available for replay are displayed through a convenient graphical GOTO screen, showing the time of the recording (vertical axis) and position in the record (horizontal axis). Each event-marked section is displayed in a different color on the graph line. The spikes on the graph line indicate times when the input signal level has exceeded a programmable threshold. A pair of cursors are used to select passages of recorded data as described later under Loop Playback, Skip and
Backup.
An important advantage of the disk recording concept is its ability to operate as a virtual ‘endless loop’, continuously overwriting earlier passages of recorded data. On an external command, recording can be discontinued, capturing a pre-programmed period of data either side of the trigger
point.
The Skip feature protects passages of data from being accidentally overwritten - a particularly useful feature in Loop Recording, for example. A cursor on the GOTO screen is used to select and tag the passage to be skipped. Data tagged in this way cannot be overwritten until the tag has been
lifted.
Similarly, passages of recorded data can also be marked for Backup at the end of the mission. In this case, the passages to be transcribed are selected and tagged using the cursor on the GOTO screen. When Backup is selected, all tagged passages are automatically backed up to the internal AIT-2 or Exabyte
drive.
If the start and finish point of a passage of data have been selected using the cursors on the GOTO screen, the recorder will output this data as an endless loop until a stop command is issued. To assist in analysis, the position and width of the selected timeframe can be adjusted as can the pause time between output
runs.
 When equipped with an analog interface, data sampling is under the control of a stable 10 MHz oscillator. For even greater stability, an external 10 MHz frequency source can be used.
The figure (right) is an unretouched copy of a chart from a digital oscilloscope, shows the Lissajous figure formed by plotting the 15 MHz sine wave output from an HP33120A Signal Generator against the replayed 15 MHz sine wave from the AE7000. From this one minute time exposure it can be seen that the displayed ellipse, comprising nearly one billion separate traces, is written so precisely as to be testing the stability of the signal source itself as much as the
recorder.
 An important feature for ‘secure’ applications, or when extended recording duration is required, is that the disk array is contained in a single, hot-swappable crate
(right). Crates can be interchanged in seconds and stored in a secure safe when not in use. The disks are isolated against shock and vibration within the
crate.
In addition, the system’s design allows full advantage to be taken of future advances in disk speed and storage capacity as they become
available.
The majority of AE7000 data input/output interfaces are designed as field replaceable modules. Avalon has scheduled the design of standard interfaces covering the most commonly used wideband analog, digital and telecommunications formats and protocols. Other application specific interfaces (such as multi-channel telemetry inputs) can be supplied either through Avalon’s engineering department or via qualified third party
associates.
Interface modules contain all the programming necessary to be recognized by the main-frame. When the system is powered-up, all installed modules are identified and interrogated, with the appropriate Graphical User Interface appearing on the
display. The following table summaries the standard interfaces currently
available. Please contact Avalon for details of Custom Interfaces.
AE7000 Data Interfaces (Summary)
|
| Type |
Description |
Recording
Time
(without looping) |
| Analog |
20 MHz / 8-bit |
98
mins. |
| Analog |
50 MHz / 8-bit |
37
mins. |
| Analog |
2 x 25 MHz / 8
bit |
37
mins. |
| Analog |
20 MHz /14-bit |
45
mins. |
| Analog |
16 x 2 MHz /
8-bit
(switchable for fewer
4, 8 and 16 MHz channels) |
51
mins. |
| Telecom |
ATM (OC-3) |
223
mins. |
| Telecom |
E1-3 |
288 hr (1 x E1)
17.5 hr (1 x E3). |
| Telecom |
E4 |
4.3 hr. |
| Digital |
Zero to 1
Gigabit/s |
37 mins @ 1Gbps. |
Disk recorders are essentially designed as flexible, high performance, but temporary data capture devices. The facilities incorporated into Avalon’s AE7000 Disk Recorder offer a range of versatile methods for copying, transcribing and forwarding data to other lower cost media. Although data may sometimes be analysed fully at the recording location, it is more usual for the acquired data to be shared with other
locations.
In some cases, it is practical for the disk crate itself to be transferred directly into another unit, for example at the completion of an airborne mission. Alternatively, data can be backed up to a tape drive located within the unit itself (see Skip and Backup modes, described earlier). The data on this cartridge can then either be ‘restored’ to another AE7000 or inputted directly to a suitably programmed NT or UNIX Workstation. If the source data is analog (say the IF output of a communications receiver) then this can be transcribed in analog form to a wideband data recorder such as Avalon’s 20 MHz AE3200FL. It is even possible to connect two or more AE7000s together via a high speed network, offering the possibility of remote, unattended operation over global-scale distances.
Each stage of the transcription process is reversible. For example, a section of analog data backed up to a
AIT-2 cassette in digital format can be restored to the same or a different
AE7000 without degradation.
By far the most popular method for post-mission data handling, however, is to extract selected passages in the form of computer compatible data files as described in the following
section.
Extracting Data in Computer Compatible File
Formats
Avalon’s unique AE7800 SIGINT Data Capture System allows users to extract and manipulate recorded data directly in computer compatible file formats. In addition to a standard AE7000 Disk Recorder, the system incorporates an IBM-compatible Workstation running Windows NT4 plus a range of proprietary file management utilities. The system will save selected passages of recorded data as named binary or ASCII files either to the Workstation’s hard drive or to any other drive in a network environment via a 10/100 Ethernet connection. Files created in this way are immediately available to all
authorized users on the network.
SIGINT Data Capture
Systems
The AE7000 Disk Recorder is also the principle
element of Avalon's revolutionary AE7800
family of SIGINT Data Capture Systems, a completely integrated
Receiver-to-Analysis package including (optionally) IF-to-Baseband
Converters, Disk Recorders, Time Stamping, Data Management, Archiving
and Forwarding plus on-board Data Analysis Software.
For applications requiring continuous data capture for extended - even indefinite - periods, Avalon offers
a range of Automated Data Storage Solutions. Please contact Avalon Electronics for further details.
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