VSA peers into circuit behavior between baseband, RF chips

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Test-and-measurement supplier Agilent Technologies Inc. is rolling out a combination of products that tightly integrate digital signal capture of Agilent's logic analyzers with the company's 89600 series vector signal analysis (VSA) software. The analysis tools are for RF signal analysis.

The combination of products is a digital vector signal analysis measurement system that delivers modulation measurements on digitized communication signals such as those in today's DSP-based radios in cellphones, cellular base stations, satellite and military communications systems, and radar applications.

Agilent claims that, for the first time, digitized transmit and receive signals found on data buses between baseband and RF blocks of digital radio applications can be analyzed in time, frequency and modulation domains within a logic analyzer—just as if they were in full analog form.

This gives you a view into circuit behavior at the digital interface between baseband and RF integrated circuits. Agilent's logic-analyzer-based approach lets you apply the full power of a VSA to waveforms, while they're still on the data buses in digitized form.

The system also provides a unified user-interface within the logic analyzer. That gives baseband and RF design and development teams the ability to share the same measurements and more easily solve cross-domain problems.

By capturing transmit and receive data buses (digital I/Q or digital IF), and demodulating them within the Agilent Digital VSA, communication system architects can gain insight into true circuit function, identifying design flaws, and accurately characterizing circuit performance.

Tight integration
The test capabilities of Agilent's Digital VSA technology are provided within a single instrument. That's achieved by the tight integration of the 89600 series software with a logic analyzer. These capabilities extend the capture and analysis power of Agilent's logic analyzers by providing tools for making modulation quality measurements on a variety of digital communication signals.

In addition to the full capabilities of Agilent's 1680, 1690 and 16900 series logic analyzers, the Digital VSA provide analysis of the digital baseband or digital IF signal in a variety of different formats, including scalar baseband, scalar IF, complex I/Q (in-phase and quadrature), magnitude and phase, and phase-only.

The system also handles flexible demodulation types to measure carrier offset, error vector magnitude (EVM) and frequency error. It will do this for QPSK, QAM, GSM, EDGE, WiMAX, WCDMA and other modulation schemes.

The Digital VSA also provides multiple display formats, including phase vs. time, frequency versus time, and spectrogram displays.

External signal generators
The 89600 software can also send signal capture files to external signal generators and analyze data from several types of signal acquisition hardware. In its source mode, an 89600 VSA can control an Agilent signal generator via IEEE-488/GPIB (General Purpose Interface Bus) or over a LAN.

Control is provided via the VSA's graphical user interface, where both frequency and level control of CW (continuous wave) signals is provided.

Arbitrary signals can also be downloaded from time capture memory to the signal generator for replay. The same time record can be played over and over contiguously. A window function can also be applied to smooth the start-up and finish of replay.

More instruments
The 89600 VSA software can also be linked to Agilent's ESA-E series spectrum analyzers, its PSA series spectrum analyzers, its 89600 VXI hardware, and most of the company's Infiniium oscilloscopes.

It can also work with Agilent's N4010A and E4406A transmitter tester via instrument-specific interfaces such as LAN, GPIB, USB or FireWire.

Price and availability
Digital VSA measurement pricing varies depending on the Agilent logic analyzer (1680, 1690 or 16900 series) and software configuration selected. Prices for the addition of the Digital VSA software start at $10,000.

- Alex Mendelsohn
eeProductCenter