Rohde & Schwarz renews spectrum analysis “flagship”

EDN Europe, 23 Sep 2011

At the top end of its range of spectrum analysers, Rohde & Schwarz has introduced the FSW, citing advances in phase noise, analysis bandwidth and in the user interface as major steps forward from previous instruments. R&S has followed the path set out with oscilloscopes such as the RTO model released last year, in having a touch-screen interface that allows you set up and view multiple measurements in any combination and in any screen position that helps you to understand the relationship between different aspects of your system’s behaviour. In particular, R&S says that it has shaped the features of the FSW for you, if you are working in fields such as radar, military and satellite communications, or in cellular basestations and, especially, multistandard transmitters.

The FSW will be available in three frequency spans; 2 Hz to 8 GHz, 13 GHz or 26.5 GHz. At 10 kHz carrier offset, the FSW has phase noise of less than –137 dBc (1 Hz), which R&S says is up to 10 dB less than comparable instruments on the market; very close to the carrier, the advantage is even greater, up to 20 dB, the company adds. Analysis bandwidth is up to 160 MHz, and internal signal paths in the instrument support up to 500 MHz in anticipation of future developments. With this, you can monitor the performance of frequency-agile signals or swept carriers such as chirped radar. With a few touches on the 12-in screen, you can place a spectrogram alongside a swept-frequency-span display (or a signal vector diagram, or any other appropriate representation) and correlate events across the multiple display formats. 160 MHz allows you to use the FSW with emerging standards such as IEEE 802.11ac.
R&S engineers also assert that the FSW will give you faster results than earlier units; in part this is from speed of set-up of measurement configurations, but it also refers to higher data throughput and shorter time to complete signal sweeps. Multipliers of five times, or 30-times, appear depending on application; you might benefit from this if you are searching for spurious emissions close to a transmitter carrier, for example.
The RF signal path in the FSW changes depending on the measured signal frequency. From near-DC (2 Hz) to 30 MHz the signal is directly digitised by a 12-bit, 200 Msamples/sec ADC. Up to around 1 GHz, the signal path uses an IF of 1.3 GHz which is also the second IF when the unit is measuring at microwave frequencies: above 1 GHz the first IF is at 9 GHz with a local oscillator tuning from 9 to 17 GHz, and the second IF is the 1.3-GHz module. Signals of over 8 GHz first encounter a YIG (yttrium-iron-garnet) pre-selector stage. The FSW switches its RF modules to re-configure these signal paths automatically and seamlessly, and you only see a contiguous sweep.
Also part of the FSW is a multistandard radio analyser that can interpret signals on different channels transmitted with different modulation schemes, simultaneously, in the manner that multistandard cellular basestations deliver their outputs. R&S adds that the FSW chassis is very modular, allowing for simple upgrades through exchange of initial, and future, plug-ins. The 160-MHz analysis bandwidth is itself an option that adds an alternative digitisation stage with a 12-bit, 1-GHz ADC. You can remove the instrument’s hard drive to protect secure data: the FSW comes with Ethernet, USB, GPIB or LXI connectivity options, and compatibility with all commonly-used programming schemes. This includes older R&S instruments; over time, the FSW will replace both the FSU and FSQ models, although these include coverage to 67 GHz that the FSW does not yet offer. Pricing, the company says, will be comparable to that of the existing units for similar frequency coverage.