Electronic Design
Signal Analyzer Aids Embedded Designers Facing RF Challenges

Signal Analyzer Aids Embedded Designers Facing RF Challenges

With embedded systems now incorporating a growing amount of RF-related functionality, designers are more in need than ever of tools and test gear that address RF issues. RF circuitry can be found in automotive systems, home-automation systems, and green-energy systems. Moreover, this RF content is typically situated in close quarters with digital circuitry, resulting in integration and electromagnetic-compatibility (EMC) challenges.

One answer to this design conundrum is available in the form of Tektronix’s RSA5000 signal analyzer, billed as the industry’s first real-time signal analyzer (see the figure). The mid-range instrument incorporates the third generation of Tek’s digital phosphor technology (DPX) and sports an 85-MHz acquisition bandwidth. Banner specifications include superior low-frequency performance with phase noise of -131 dBc/Hz at 10-kHz offset and -150-dBm displayed average noise level (DANL) at a 10-MHz carrier frequency.

First introduced in 2006 and revamped in a second generation 18 months ago, DPX technology first performs a digital conversion to analog RF waveforms. Next, a discrete Fourier transform is applied to obtain a spectrum image. In the third generation of DPX technology, it’s now applied to multiple domains: amplitude, frequency, or phase versus time. In doing so, the display updates at up to 50,000 waveforms/s; this approximates zero-span technology but is in fact 1000 times faster than zero-span technology for amplitude-vs.-time measurements. As a result, the instrument can find and measure RF-amplitude transients that other analyzers can miss.

What is new in the RSA5000 for signal analyzers is its ability to apply DPX in the frequency-vs.-time and phase-vs.-time modes. With DPX available in multiple domains, users can find and measure phase or frequency transients that won’t turn up in post-processed vector signal analyzer (VSA) analysis. Further, the addition of a frequency-edge trigger enables one to look at a very specific frequency crossing and be able to trigger on that signal. This is an important capability for embedded-RF designers who are performing analyses on frequency-hopping designs, as well as for spectrum-management applications that require power and frequency monitoring of short- and long-term events.

The RSA5000 should fulfill most requirements for a real-time spectrum/signal analyzer, given its DPX capabilities and minimum signal duration of 5.8 µs. It can perform swept-DPX analyses, enabling users to sweep the instrument’s full frequency range with live RF. Further, it can capture up to 7 s of signal at full 85-MHz bandwidth. That’s enough to capture the entire setup period of a Bluetooth transaction that is hopping across that entire 85-MHz spectrum.

Embedded-RF designers, or those doing electromagnetic interference (EMI) diagnostics, will also benefit from visibility into the instrument’s full bandwidth. This can aid with debugging jamming (or self-jamming) issues. In radio-communication design tasks, the instrument’s RF performance acquits itself well. Being able to see the entire 75-MHz bandwidth of a cellular receiver, for example, is a handy capability to have. As a tool for spectrum management and monitoring, the instrument’s real-time monitoring of 85-MHz bandwidths means a 100% probability of intercept for signals as brief as 6 µs.

The RSA5000 series signal analyzers are available now with prices starting at $34,900.


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