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AWG serves microwave design

Posted: 28 Jun 2005 ?? ?Print Version ?Bookmark and Share

Keywords:agilent technologies? n6031a module? awg arbitrary waveform generator module? compactpci?

Can be synchronized to generate phase-coherent signalAgilent Technologies' low phase-noise N6031A AWG (arbitrary waveform generator) module, using a CompactPCI backplane internally and to connect to the chassis that it's plugged into, offers dual differential output channels to drive both single-ended and balanced designs. Its two independent channels are available as baseband or IF (intermediate frequency) outputs.

With that, you get the choice of driving your circuitry differentially from the module's DAC (digital-to-analog converters) outputs (which improves common-mode rejection), or single-endedly through multiple signal-conditioning paths. You can drive up to a volt (p-p) in single-ended operation, and 0.5V differentially.

Inside the N6030A plug-in Agilent uses two high-speed DACs to get the 500MHz of signal bandwidth. These DACs also let the instrument achieve at least -65dBc of SFDR (spurious-free dynamic range) across each channel. Phase noise can constrain dynamic range, but a glance at the instrument's specs confirms that the N6030A is indeed a high performance box. At 1-kHz, phase noise is specified to be -95dBc/Hz. At 10kHz it's -115dBc/Hz. At 100kHz it's -138dBc/Hz, and at 1MHz it comes in at -150dBc/Hz.

Fast downloads

If you're running many waveform scenarios, the plug-in's CompactPCI backplane also reduces waveform downloading time. It's much faster than conventional LAN (local area network) or IEEE-488/GPIB (General Purpose Interface Bus) downloads.

Not mentioned in Agilent's notes is the fact that this system's sequencer relies on an FPGA (field programmable gate array) engine that addresses multiple banks of waveform memory. A separate bank holds segment information that's used to define the order that stored waveforms are played back in.

Significantly, the N6030A's waveform and sequencer memories can typically be re-loaded in less than a second. That aids and abets the long loop and repeat capabilities mentioned in the press statement.

Unconstrained differential channels
Some competing AWGs also require you to make a tradeoff between the number of output channels and differential outputs, but the N6030A gives you the best of both worlds. You don't have to compromise. That means you can drive whatever needs your design may impose, essentially eliminating the need for placing kludgey baluns (balanced-to-unbalanced transformers) or hybrids in the test path. In addition, each channel can output waveforms as an IF or as a baseband signal for I/Q (in-phase and quadrature) up-conversion.

As noted in Agilent's press statement, the AWG's sequencing and triggering modes can let you readily create event-based signal simulations, too. The N6030A's four trigger inputs control the waveforms in the instrument's sequencer in order to create event-based signal simulations.

Not mentioned in the press release is the fact that multiple N6030A AWGs can also be synchronized to generate phase-coherent signals for simulations of multiple RF emitters.

That's done by means of a precision SYNC clock. In use, a single AWG can drive a total of eight AWG modules to sync their outputs on a sample-by-sample basis.

The modules are also synchronized with relatively simple driver hardware, and the AWG includes multiple front-panel trigger and marker connectors to help in this system synchronization configuration; all are gold plated. The markers connectors are 3.3V TTL/CMOS terminated and can drive 50? loads. The trigger input connectors support TTL/CMOS, ECL, and PECL logic levels.

RF/IF strip tests
If the N6030A is combined with a wideband I/Q (in-phase and quadrature) up-converter, modulation bandwidths of 1GHz can be realized at microwave frequencies. That's just what's needed for signal simulations for advanced RF strip and IF strip testing.

The release notes also briefly mention The MathWorks's popular MATLAB software. Using it, advanced instrument control can be achieved directly from MATLAB's command line. In addition, other programming interfaces are included. These include LabVIEW, IVI-C, Agilent ADS, and Microsoft.NET.

The N6030A's inherent GUI (graphical user interface), as depicted above, guides you through set-up and waveform file transfer operations. Using the GUI, you can configure signal conditioning paths, marker and trigger lines, sample and reference clock sources, and most basic sequencing functions. More sophisticated sequencing is done using the above-named packages.

- Alex Mendelsohn

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