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Industry News

A 10 MHz to 46 GHz Microwave Spectrum Analyzer for Testing Wireless Backbone Links

An introduction to the model 6845 10 MHz to 46 GHz microwave spectrum analyzer with a full bandwidth, independently-controlled tracking generator

April 1, 2001
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IFR Systems Inc.
Wichita, KS


MWJ23TA The growth of the wireless market at higher frequency bands means that approximately half of all radio links manufactured are above 30 GHz. The 38 GHz band is significant with increasing interest in bands above 40 GHz, particularly 42 and 43 GHz. In this region, both point-to-point and point-to-multipoint radios for broadband wireless access are becoming available.

To manufacture and maintain such links demands test equipment with capability in this part of the spectrum. Fulfilling the requirement is the model 6845 10 MHz to 46 GHz Microwave Spectrum Analyzer with a full bandwidth, independently-controlled tracking generator.

Integrated into this single instrument are a synthesized source, a three-channel scalar analyzer and a spectrum analyzer. The inclusion of a 46 GHz tracking generator is of particular merit for engineers because it allows the 6845 to act as both transmitter and receiver when testing up and down links.

For insertion and reflection measurements, the tuned input of the 6845's spectrum analyzer gives a dynamic range of 70 dB at 40 GHz. The instrument is especially effective for frequency conversion measurements when the ability to set the spectrum analyzer and source frequencies independently in both CW and swept modes greatly simplifies the testing of mixers, up and down converters, and frequency multipliers and dividers. Figure 1 shows the instrument's display of a 38 GHz radio signal spectrum. Figure 2 shows the response of a 24 GHz high pass filter.

As an addition to the 6840 series, the 6845 incorporates the main features of the existing range. For instance, the integration of a source, spectrum analyzer and scalar analyzer into a single instrument means the operator uses a single interface to set up any measurements. This saves time and is easier than writing software to perform complex measurement tasks, such as frequency offset network measurements.

Eight soft keys give rapid access to all commonly used parameters and are shaped to inform the user of the action that the key will perform, such as enter data, select from list, move to another menu or immediate action. All commonly accessed functions are no more than one level deep.

To simplify operation a built-in applications interface allows the users to create their own measurement routines and guides the operator through the test procedure. For example, it can display on screen how to set up the measurement, lead the operator through a calibration, show where to connect the device under test and then test the device's performance against predefined limits.

A large thin-film technology (TFT) display shows up to four measurements on two channels, and scalar and spectrum measurements can be displayed simultaneously on independent channels. Alternatively, two spectrum channels can be shown with a wide and narrow frequency sweep. This could be used to scan a frequency spectrum for interfering signals, while simultaneously displaying the wanted carrier.

Up to eight markers are available. In spectrum mode the markers identify the frequency and level of a signal, position signals on the display and measure relative signal values. A peak search feature places markers on the eight highest signals displayed for spurious signal identification. A table displayed below the traces shows the values of all eight markers dynamically.

In scalar mode, markers automatically calculate peak-to-peak ripple, N - dB bandwidth, ­1 dB compression point, and find the maximum and minimum signal levels. For fault location measurements the next peak left/right feature identifies the position and magnitude of each of the discontinuities along the transmission lines, with the peak find soft key used to quickly locate the biggest discontinuity on the line.

The 6845 provides real-time transmission line fault location with 0.1 percent accuracy, and its applications interface allows guided and automatic testing. The use of electrically erasable programmable read-only memory (EEPROM) corrected scalar detectors ensures accurate measurements, which can either be saved to internal non-volatile memory or to a 3.5" disk. Traces saved onto disk can then be either archived or imported into a spreadsheet for viewing.

By providing an integrated solution to component and subsystem testing from 10 MHz to 46 GHz the 6845 has particular relevance to the manufacturing, installation and maintenance of point-to-point and point-to-multipoint radios and satellite communications equipment. It is especially designed for testing components and assemblies used in radio and military systems.

For component and subsystem design engineers, the flexibility provided by the instrument's integrated testing solution can help reduce design time. For installation and maintenance engineers it provides a quick and convenient method of measuring return loss and fault location on antennas and feeders at mobile communications basestations, as well as verifying radio performance through the modulation spectrum.

Other applications include measuring for compliance with specifications on emissions, which must be below a specified level and can run up to 44 GHz. Similarly, test houses have a requirement to measure components at these frequencies, particularly for electromagnetic compatibility and Conformite European (CE) marking activities.

Also, for those out in the field maintaining radio links at frequencies above 30 GHz, the fact that the spectrum analyzer is incorporated into the same box as an instrument that enables the measurement of SWRs is a benefit.

Whether in the laboratory, on the factory floor or out in the field, an instrument's reliability and capability for future expansion are paramount. That is why the 6845 Microwave System Analyzer is of modular design for rapid servicing and includes expansion slots for ease of upgrading to accommodate additional modules and options.

IFR Systems Inc.,
Wichita, KS (316) 522-4981
or (800) 835-2352.

Circle No. 303

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