Spectrum Analyzer Spans 20 Hz To 67 GHz

Sept. 12, 2007
This spectrum analyzer covers 20 Hz to 67 GHz with a single coaxial connection, and without the help of external frequency mixers.

Spectrum analyzers are considered essential RF/microwave test tools. With spectral crowding, the need closely track interference caused by harmonic signals, and the opening of millimeter-wave bands for commercial communications, spectrum analyzers must provide greater frequency coverage than ever before, and the R&S FSU67 spectrum analyzer from Rohde & Schwarz (www.rohdeschwarz.com) sets a new standard for single-connection coverage with a coaxial range of 20 Hz to 67 GHz. It is the first commercial spectrum analyze to coverage that expanse one full-span sweep, and without external harmonic mixers.

The broadband R&S FSU67 spectrum analyzer (Fig. 1) integrates an instrument-controlled RF attenuator with a range of 0 to 75 dB in 5-dB steps. The built-in attenuator eliminates the need for the external, manually operated step or rotary attenuator associated with harmonic mixers. In addition to bringing simplicity to millimeter-wave spectrum analysis, the R&S FSU67 also boasts a reference level range (–130 to +30 dBm) that is far beyond what is possible using external harmonic mixers.

The R&S FSU67 is the latest member of the company's FSU spectrum analyzer family, which includes models with measurement frequencies from 20 Hz to 3.6, 8, 26.5, 46, and 50 GHz. The firm strives for functional commonality among the members of an instrument family, and the R&S FSU67 continues this trend. It is software-compatible with other FSU spectrum analyzers as well as with other Rohde & Schwarz spectrum analyzers, and the test routines created for other spectrum analyzers and signal analyzers can be used on the R&S FSU67 as well.

With a maximum measurement frequency of 67 GHz, the instrument is not targeted to designers of "low-frequency" wireless systems, but rather those designing radar, electronic warfare (EW), electronic countermeasures (ECM), microwave radio, and satellite-communication (satcom) systems, in addition to emerging high-frequency wireless systems. As a result, the options available for the R&S FSU67 are different than for other R&S FSU spectrum analyzers. However, the R&S FSU67 retains the core functionality of the instrument family along with its inherent strengths in measurement speed, signal purity, and standard features.

In addition to its likely use in research and development, the R&S FSU67 will also find a home on the production line. For this application, it provides both high measurement speed and signal purity along with IEEE-488 (GPIB) or Ethernet local-area-network (LAN) connectivity. It is also certified compliant with the LAN eXtension for Instruments (LXI) Class C standard for reliable communications over a standard LAN. The R&S FSU67 can make 80 measurements/s in manual mode and 70 measurements/s over the IEEE-488 bus, for enhanced production test throughput.

The instrument will also control external signal generators via IEEE-488 or TTL bus to act as tracking sources for making scalar transmission, loss, and reflection measurements. Screen contents can be saved as .bmp or .wmf files and imported into word-processing documents, or as .csv files for use in spreadsheets. The instrument has several Universal Serial Bus (USB) interfaces that allow firmware updates and other files to be imported from an external flash memory device, hard drive, or CDROM, and allow connection of a computer mouse and/or keyboard.

Specifications for the R&S FSU67 include a noise floor of –158 dBm at 1 GHz and –130 dBm at 65 GHz, resolution bandwidth filters from 1 Hz to 50 MHz, display linearity of better than 0.1 dB, total measurement uncertainty of 0.3 dB or less, and amazing frequency resolution of 0.01 Hz. The phase-noise performance is excellent across the entire measurement range (Fig. 2), with levels of –104 dBc/Hz offset 100 Hz from the carrier and –160 dBc/Hz offset 10 MHz from the carrier. The table provides a summary of the R & S FSU67's specifications.

The R&S FSU67 can perform as a fully featured RF power meter with instantaneous display of measurement results when coupled with one of the company's R&S NRP Series power sensors. Sensor calibration factor is automatically applied along with the selected center frequency. In addition, channel and adjacent-channel power can be determined with the instrument's time-domain power-analysis capability and channel or RRC filters.

Demodulators for measuring signals with amplitude modulation (AM), frequency modulation (FM), and phase modulation are optionally available for determining frequency deviation and the frequency settling of oscillators. The R&S FSU67 can be outfitted as an automated phase-noise measurement system, determining residual FM from a source's phase-noise characteristics. Noise-figure measurement capability is also optionally available which, combined with the instrument's linearity and calibrated power-measurement routines, eliminates the need for a separate noise-figure meter.

A comprehensive array of tools is available for performing signal analysis, including a third-order intercept marker, noise and phase noise marker, complementary-cumulative-distribution-function (CCDF) statistical measurements, split-screen mode, a peak list marker for spurious signal searches, as well as spurious and harmonic emission testing.

A wide variety of filters are available, including sweep filters from 10 Hz to 50 MHz, digital Fast Fourier Transform (FFT) filters from 1 Hz to 30 kHz, and communications channel filters from 100 Hz to 5 MHz. For electromagnetic-interference (EMI) applications, 6-dB-bandwidth filters addressing commercial and military applications are available.

The R&D FSU67's LO and IF ports can be configured with external mixers to increase the measurement range to 110 GHz. Rohde & Schwarz, 8661A Robert Fulton Dr., Columbia, MD 21046; (410) 910-7800, Internet: www.rohde-schwarz.com.

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