Transcorder Tackles 50 MHz to 6 GHz

March 12, 2015
Within its nearly 6-GHz wide bandwidth, this compact signal recorder/playback system can capture as much as 80 MHz of bandwidth in two 40-MHz frequency spans.
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Measuring RF/microwave signal activity is not always easy because of the changing nature of those signals, especially when the activity may be irregular or inconsistent. Yet, it is often necessary to have some form of record of a particular signal, especially when characterizing or documenting the activity of different wireless systems.

1. Model WBT-200 is a portable RF/microwave recorder/playback instrument capable of recording and playing back as much as 80 MHz of bandwidth from 50 MHz to 6 GHz.

Fortunately, the model WBT-200 Wide Band Transcorder (WBT) from QRC Technologies is a compact, portable solution for recording and playing back portions of RF/microwave bandwidth from 50 MHz to 6 GHz. With its two independent transceivers, it can be tuned to measure two separate 40-MHz sections of bandwidth across that nearly 6-GHz range and capture signals across a 74-dB instantaneous dynamic range. It is actually a system in a box, storing test results on solid-state drives for ease of data transport and analysis with external computers.

The WBT-200 (Fig. 1) performs signal analysis and signal generation across its frequency range, all from a compact enclosure measuring just 18.7 × 12.4 × 3.1 in. (47.5 × 31.5 × 7.9 cm) and weighing less than 10 lbs. (4.5 kg). It is relatively simple to operate, with a straightforward user interface and single button for activating RF/microwave signal recording and playback. The WBT-200’s two transceivers each feature typical receiver sensitivity of -95 dBm on standard input ports and -110 dBm on special-use ports. SMA female connectors are used on the WBT-200’s input and output ports.

Each transceiver provides selectable bandwidths of 0.78125, 1.5625, 3.125, 6.25, 12.5, 25, and 40 MHz with as much as 30-dB input gain and 30-dB input attenuation to control the levels of input signals. The transceivers maintain high sensitivity due to low-noise tuning sources and reference clocks, with phase noise of better than -80 dBc/Hz offset 1 kHz from a 1-GHz carrier.

The WBT-200 incorporates an embedded Global Positioning System (GPS) disciplined oscillator (GPSDO) which produces an internal 10-MHz timing reference signal—which is also available at an output port (BNC connector) to be used as input signals for synchronizing other equipment, such as additional WBT-200 systems. The GPS signals exhibit stability of 1 PPS with ±50-ns accuracy and also serve to tag signal recordings with GPS geolocation details. The WBT-200’s 50-channel GPS receiver has an acquisition sensitivity of -144 dBm and tracking sensitivity of -160 dBm.

Each WBT-200 records to and plays back signals from standard 2.5-in. solid-state drives (SSDs) using the VITA 49 Radio Transport (VRT) industry-standard open memory format. Data from these drives can also be analyzed and visualized by means of the WBT’s Signal Analysis Toolkit or other software packages that can work with the file format.

Each WBT-200 has two SSD drive bays. For long recording sessions, one SSD can be replaced while the other SSD is active and recording, without interrupting or degrading the recording. For applications where less than 80 MHz of instantaneous bandwidth is required, it is possible to operate with considerably less of disk space.

2. Model WBT-201 provide the equivalent measurement capabilities of the WBT-200, in a half-rack-mount enclosure for permanent installations.

The WBT-200 shows results on a 10.4-in diagonal liquid-crystal-display (LCD) screen with 1024 × 768 pixel resolution. The compact transcorder is designed for use with operating temperatures from 0 to +50°C. It includes a Gigabit Ethernet port for remote control of other WBTs or to transfer data.

The portable WBT-200 can be used for reference signal recording and playback, for interference analysis, and for general signal analysis. It is supported by numerous application software tools, and consumes typically 60 W power. It can run on DC voltage from 10 to 32 VDC, AC voltage of 120 or 240 VAC, an AC power adapter (that supplies 20 VDC), an internal UPS battery consisting of four LiFePO4 rechargeable cells, and an automobile cigarette-lighter adapter.

For those seeking slightly greater stability, the signal recorder/player is available as model WBT-210 (Fig. 2), with all the same measurement capabilities as the WBT-200 but in a rack-mount enclosure.

QRC Technologies, 1211 Central Park Blvd., Fredericksburg, VA 22401; (540) 446-2270

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About the Author

Jack Browne | Technical Contributor

Jack Browne, Technical Contributor, has worked in technical publishing for over 30 years. He managed the content and production of three technical journals while at the American Institute of Physics, including Medical Physics and the Journal of Vacuum Science & Technology. He has been a Publisher and Editor for Penton Media, started the firm’s Wireless Symposium & Exhibition trade show in 1993, and currently serves as Technical Contributor for that company's Microwaves & RF magazine. Browne, who holds a BS in Mathematics from City College of New York and BA degrees in English and Philosophy from Fordham University, is a member of the IEEE.

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