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High Performance Spectrum Analysis to 26.5 GHz

Digitally synthesized spectrum analyzers providing precision performance and versatility in an easy-to-use instrument

August 1, 1997
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High Performance Spectrum Analysis to 26.5 GHz

IFR Systems Inc.
Wichita, KS

The AN1800 series high performance spectrum analyzers are designed to meet the needs of cellular maintenance, microwave link analysis, radar installation and maintenance, satellite earth station communications and precompliance testing of electromagnetic compatibility (EMC). The series comprises the models AN1820, AN1830 and AN1840, which provide frequency coverage from 9 kHz to 2.9, 22 and 26.5 GHz, respectively. The analyzers offer precision performance and versatility in an easy-to-use instrument.

Features and Applications

The AN1800 series spectrum analyzers are digitally synthesized, enabling accurate measurements over wide frequency spans. A built-in frequency counter allows accurate frequency measurements of signals down to –85 dBm and resolutions as fine as 1 Hz. An optional time base provides measurement accuracy to 0.02 ppm.

The spectrum analyzers utilize proven fundamental mixing to 12 GHz and two harmonic steps are incorporated to achieve frequency coverage to 26.5 GHz. This technique provides good sensitivity throughout the entire frequency range and allows detection of interfering signals, even those that are masked by noise.

The AN1800 series analyzers are ideally suited for analyzing frequency-hopping and spread spectrum signals due the instruments’ state-of-the-art 30 MHz wideband demodulator. In addition, the wide dynamic range and internal frequency counter allow rapid characterization of interfering signals. These interfering signal sources are identified easily with the instruments’ integrated AM/FM receiver.

Modulation detection may be set to wideband or narrowband modes. Ten, 20 and 50 percent per division AM modulation scales and 1 kHz to 5 MHz per division FM modulation scales allow direct measurement of modulation components of carrier signals to ±20 MHz deviation. A built-in speaker and headphone connector allow audible detection of noise and distortion. The DC-coupled FM detector output makes measurement of frequency synthesizer settling time possible.

The AN1800 series spectrum analyzers contain 10 and 30 MHz resolution bandwidth filters that ensure accuracy when measuring wide bandwidth signals, such as those found in spread spectrum radio and pulsed radar applications. The filters optimize signal characterization of wideband signals by providing an impulse bandwidth of greater than 5 MHz.

Signal components with as little as 10 Hz separation are detected easily using the analyzers’ 3, 10, 30 or 100 Hz selectable digital bandwidths. Seven windowing function choices make it possible to match the digital bandwidth characteristics to the desired signal measurement. Using the 3 Hz resolution bandwidth, a noise level of less than –135 dBm at 2.9 GHz and less than –125 dBm at 26.5 GHz permits the easy location of low level spurious and harmonic signals.

A built-in tracking generator with an adjustable output of –70 to 0 dBm is available for use as a low level input for amplifiers or as a synthesized LO for making frequency response measurements on filters, amplifiers and couplers. An optional Quasi Peak detector with three extra resolution bandwidth filters conforms to the recommendations for RF emissions measurements in accordance with the latest stringent EMC specifications instituted in Europe and North America. Precompliance testing of EMC characteristics can be performed using the AN1800 series analyzers.

The analyzers also perform time-domain measurements at sweep rates up to 200 ns/div. A total of ±300 divisions of pre- and posttrigger ranges enable accurate real-time interval measurements with digitizing rates up to 25 Msps. In addition, the spectrum analyzers’ input mixer minimizes internally generated intermodulation distortion, resulting in true spectrum displays.

Many of the user interface features have been designed to simplify measurement procedures and boost productivity. A 6.4-inch liquid-crystal display shows settings and measurements in full-color VGA resolution and an extensive marker function simplifies signal analysis. The user-friendly front-panel control makes measurement tasks easier by utilizing simple menus and soft keys. Standard RS-232 and IEEE-488 interfaces are available for remote operation and control. The instruments’ nonvolatile memory stores up to 99 traces and setups for future recall and an extensive marker system helps simplify analysis.

A unique automatic limits test mode makes the task of detecting erroneous signal conditions simple and straightforward. A limit violation triggers one or more user-specified actions including automatic storage of the trace violation with date and time recorded for later recall and analysis.

EasySpan® waveform transfer software, a Windows™-based program for PCs, extracts and displays sweep traces and setups. The easy-to-use software downloads data to a PC for future reference or handles a modem connection for remote-site monitoring. In addition, the interactive graphic user interface allows the flexibility to write customized automatic trace aquisition macros.

Conclusion

The AN1800 series spectrum analyzers are a unique combination of precision performance and versatility that provide an easy solution to today’s RF and microwave signal analysis requirements. The instruments’ rugged, portable design makes them suitable for use in the laboratory as well as in the field.

IFR Systems Inc., Wichita, KS (316) 522-4981.

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