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Spectrum analyzers have long been among the most popular, invaluable RF/microwave test equipment. By offering as much measurement power in the RSA306 portable spectrum analyzer for such a low price, Tektronix is also making this instrument more accessible to a greater number of users.

Fig. 1As an added bonus, this truly is a “green” measuring tool, requiring only 4 W of operating power for spectrum measurements from 9 kHz to 6.2 GHz. The compact spectrum analyzer works with the processing functionality of a personal computer (PC) and Tektronix’s supplied SignalVu-PC software to provide all the capabilities of a full-sized spectrum analyzer, at a fraction of the size and price.

The compact RSA306 (Fig. 1) is not the spectrum analyzer of years past—which is to say, one of those hefty portable units with carrying handles (the 492 and 494 series) upon which Tektronix built its reputation for quality and innovation. This new, portable instrument weighs a mere 1.2 lbs and is the firm’s first spectrum analyzer with a Universal Serial Port (USB) 3.0 connection, but it certainly won’t be their last. It is designed for use with a laptop or other PC running with the proper measurement software.

The essential spectrum-analyzer functionality is contained within the RSA306’s portable-radio-sized housing; it relies on the computer for control, processing, and screen display to show captured signals across an instantaneous real-time bandwidth of 40 MHz. The analyzer has a frequency span range of 1 kHz to 40 MHz. The RSA 306 measures just 5.0 × 7.5 × 1.2 in. (127 × 190.5 × 30.5 mm, making it a perfect fit for both field and laboratory. It uses a Type-N female RF/microwave input connector and SMA female connectors for the external frequency reference input and trigger/sync input signals.

The RSA306 (Fig. 2) achieves frequency accuracy of 3 ppm across its full operating temperature range and provides an amplitude measurement range of -160 to +20 dBm. The absolute amplitude measurement accuracy is ±1 dB + the absolute amplitude accuracy for room-temperature measurements (from +18 to +28°C). The spectrum analyzer can performed stepped measurements, with dwell times per step from 50 ms to 100 s.

The RSA306 offers a resolution-bandwidth (RBW) filter range from 10 Hz to 10 MHz and can achieve in-phase/quadrature (I/Q) measurement resolution of 17.9 ns for an acquisition bandwidth of 40 MHz. This rugged little analyzer is low on noise, with second-harmonic distortion of typically less than -55 dBc from 10 to 300 MHz at a reference level of 0 dBm and typically less than -50 dBc from 10 MHz to 3.1 GHz at a reference level of -40 dBm.

Fig. 2The analyzer’s displayed average noise level (DANL) is specified as -130 dBm/Hz from 100 kHz to 42 MHz; -145 dBm/Hz from 2 to 5 MHz; -160 dBm/Hz from beyond 5 MHz to 1 GHz;-158 dBm/Hz from beyond 1 GHz to 2 GHz; -155 dBm/Hz from beyond 2 GHz to 4 GHz; and -150 dBm/Hz from beyond 4 GHz to 6.2 GHz. The instrument’s phase noise for a carrier of 10 MHz is -108 dBc/Hz offset 1 kHz from the carrier; -118 dBc/Hz offset 10 kHz from the carrier; -120 dBc/Hz offset 100 kHz from the carrier; and -122 dBc/Hz offset 1 MHz from the carrier.

At the other measurement extreme, the RSA306’s phase noise for a 6-GHz carrier is -70 dBc/Hz offset 1 kHz from the carrier; -75 dBc/Hz offset 10 kHz from the carrier; -85 dBc/Hz offset 100 kHz from the carrier; and -105 dBc/Hz offset 1 MHz from the carrier.

It is important to remember that the PC contributes to the performance of the RSA306 spectrum analyzer, not just to controlling the analyzer. The RSA306 requires a PC with Windows 7 or Windows 8 or 8.1 with a 64-b operating system and a USB 3.0 connection to link the PC with the spectrum analyzer. Installation of the SignalVu-PC software on a computer will require at least 8 GB random-access memory (RAM) and 20 GB free hard-drive or flash memory.

To take full advantage of the RSA306’s features and performance, an Intel Core i7 4th generation processor is required. The spectrum analyzer can operate with computers having processors with lesser capabilities, although the real-time performance of the spectrum analyzer will be reduced. Storage of streaming data requires that the PC be equipped with a drive capable of streaming storage rates of 300 MB/s.

The portable analyzer is shipped with SignalVu-PC software, which will run on most laptop or desktop PCs and provides tremendous flexibility in the measurement and analysis of signals within the RSA306’s range. In addition to using SignalVu-PC for running tests and programming control of the RSA306, the software can be used with an included application programming interface (API) to execute its own extensive set of commands and measurements.

Also, a MATLAB driver is available for the SignalVu-PC API, to operate the RSA306 with the MATLAB mathematical analysis software from The MathWorks and its Instrument Control Toolbox.

By leveraging its computer “companion” and the SignalVu-PC software, the RSA306 can perform many measurements beyond a traditional spectrum analyzer. The basic software provides spectrum analyzer functionality with three signal traces and a spectrogram trace, along with five markers with power, relative power, integrated power, and other functions. It can capture and report signals as narrow as 100 μs in a 40-MHz-wide span.

The software also supports basic vector analysis functions, including amplitude, frequency, and phase versus time, as well as I and Q versus time. The software enables AM/FM radio monitoring and measurements, multichannel power measurements, measurements of adjacent-channel leakage ratio (ACLR), and the use of the complementary cumulative distribution function (CCDF) for plotting the statistical variations in signal levels. By using Fast Fourier Transforms (FFTs), the spectrum analyzer and PC can show frequency as a function of time for advanced signal analysis.

The software can also be used for spectrum mask testing with the RSA306, to simplify signal monitoring of a portion of spectrum of interest. Mask testing can be used to find intermittent interference or other types of spectrum violations, for durations as short as 100 μs. The software can be used to color-code signals of interest, using a mask to identify a particular portion of spectrum.

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