White Paper

WHITE PAPER Development Tactics and Techniques for Small Form Factor RF Signal Recorders mrcy.com 3 GNNS receivers also allow systems to record the latitude, longitude and altitude of the recorder, for logging flight paths, vehicle movement or static ground location, if required. GNNS receivers often provide options for oven controlled oscillators for operation across a wide range of temperatures and accelerometers to improve time and position accuracy during rapid acceleration, allowing them to operate in a wide range of environments. DRIVE PACKS SIMPLIFY HIGH CAPACITY DATA STORAGE Streaming data to disk in real-time at rates in the gigabytes per second has been achievable in large rackmount recorders by striping data over a RAID array of many SSDs. High performance RAID controllers not only provide lightning fast write speeds but offer redundancy, protecting against the rare but disastrous disk failure that could occur during a mission. RAID controllers also utilize SSD features to provide data encryption and secure erase capabilities. Another feature typical seen in rackmount recorders is front panel removable drives. An array of as many as 48 drives, mounted to sleds can be inserted and removed individually from the front of the system. This allows users to remove all recorded data while allowing the recorder to remain mounted in a rack. It also allows users to maintain multiple sets of drive arrays to minimize downtime between missions. Figure 2: Mercur y 's QuickPac TM drive pack provides up to 30 TB of solid state storage in a small package. Images show the QuickPac drive pack and OS drive removed and partially ejected from the Talon Model RTX 2589 3.6 GS/sec Ultra Wideband RF/IF Extreme 1/2 ATR Recorder. While the A /D sample rate is impor tant for selecting the front end of our recorder, the dynamic range of the A /D is equally impor tant to effectively match each application's requirement. For an RF signal recorder, dynamic range can be described as the ratio between the largest and smallest signals that can be recorded successfully. Some signal acquisition scenarios require the ability to record ver y small signals in the presence of potentially ver y large signals, requiring an A /D conver ter with excellent dynamic range. The bit resolution of the A /D conver ter and the effective number of bits (ENOB) help to express dynamic range to the user. However, A /D conver ter specifications like spur free dynamic range (SFDR) and signal to noise ratio (SNR) provide an even more useful way to present dynamic range. High per formance 200 MS/s A /D conver ters provide 16 bits of resolution and offer SFDR specifications greater than 85 dBFS and SNR specifications greater than 75 dBFS, while 6.4 MS/s A /D conver ters provide 12 bits of resolution and offer SFDR closer to 65 dBFS and SNR closer to 55 dBFS. Typically, the higher the sample rate of the A /D conver ter, the lower the dynamic range, so it is impor tant to provide a wide array of A /D conver ters on XMC modules to cover different types of applications. FPGAs coupled with A /D conver ters on XMC modules provide an excellent digital signal processing engine for the recorder. Digital downconver ters, signal detection, radar gating and acquisition time stamping are common processing capabilities that are often provided in standard FPGA IP designs. A well developed set of FPGA IP modules greatly enhances the capabilities of an RF signal recorder. D/A conver ters are often included on XMC modules to allow users to playback acquired signals or generate radar pulses. Multi-channel A /D and D/A XMC modules provide phase coherency across all channels. This is an essential capability of any real-time signal recorder. PRECISION TIME STAMPING WITH SMALL GNNS RECEIVERS Extremely small GNNS receivers have emerged over the last few years with suppor t for Galileo, GPS and Glonass systems. These small receivers suppor t timestamping of acquired data with nanosecond precision. The receivers provide 10 MHz reference clocks and PPS signals to the recorder 's XMC modules to allow users to capture the exact timing of gated or triggered events.

• Cover