Oscilloscopes are versatile, workhorse test instruments, ideal for high-speed circuit characterization. But for microwave measurements, they have rarely been considered on par with a vector network analyzer (VNA).With the introduction of the Infiniium 90000 X-Series of digital oscilloscopes from Agilent Technologies (www.agilent.com), that thinking may change. These high-performance oscilloscopes come in 10 models with real-time bandwidths ranging from 16 to 32 GHz. They feature sampling rates as high as 80 GSamples/s and the support of a new probing system with capability through 30 GHz.

A VNA may be a familiar sight on microwave company test benches, but these new Infiniium 90000 X-Series scopes (Fig. 1) are sure to earn a place nearby. The 10 models can operate as two-channel or four-channel instruments, with five each DSO-X and DSA-X models. The former comes equipped standard with 10 Mpoints/ channel of signal acquisition memory while the latter is shipped with 20 Mpoints/channel memory along with additional noise-reduction and serialdata- analysis capabilities. All of the scopes can be upgraded to hold as much as 2 Gpoints/channel of acquisition memory. The 10 models differ in analog bandwidth capabilities. For example, the low-end DSO/ DSA-X91604A models offer 16-GHz analog bandwidths across both two and four channels, while the high-end DSO/DSA-X93204A models provide 32-GHz analog bandwidth when only two channels are used and 16-GHz analog bandwidth when all four channels are used. The sampling rates for all models are 80 GSamples/s for twochannel operation and 40 GSamples/s for four-channel operation.

Noise is a function of bandwidth, and the lower frequency models maintain a noise floor of 1.34 mV at 16 GHz for a scale of 50 mV/div and 0.348 mV for a scale of 10 mV/div. At 32 GHz, the noise floor is a mere 2 mV at a scale of 50 mV/div and only 0.6 mV at a scale of 10 mV/div. The signal sensitivity can be set from 1 mV/div to 1 V/div. To minimize interference between channels, the oscilloscopes provide 60-dB channelto- channel isolation through 3 GHz, 40 dB channel-to-channel isolation through 8 GHz, and 35 dB through 32 GHz. The oscilloscopes attain a jitter measurement floor of about 180 fs and sample clock jitter of less than 20 fs. Signals from the internal 10-MHz reference can be sent to an external port to synchronize instruments in an automatic-test-equipment (ATE) setup.

The 50-Ohm, DC-coupled oscilloscopes digitize signals with 8-b vertical resolution and show information on a bright 12.1-in., 1024 x 768-pixel, XGA color touch-screen display. The display screen offers 256-level intensitygraded or color-graded persistence that provides a near three-dimensional (3D) view of signal information.

The scopes are aided by a new series of InfiniiMax III probes with PrecisionProbe software. The probes can be specified with a variety of probe tips for use through 30 GHz. In addition, they work with the PrecisionProbe AC calibration software for improved accuracy. The software can be used to automatically remove the effects of load probing, most noticeable at higher load probing, most noticeable at higher frequencies, without the need to transfer functions by means of time-domain reflectometer or VNA.

The oscilloscopes also feature built-in Fast Fourier Transform (FFT) signalprocessing capability to quickly and easily analyze the frequency components of acquired signals. The FFT capability allows signal magnitude and phase to be studied by means of a variety of windowing functions, including Hanning and rectangular functions. For modulation analysis, each of the oscilloscopes can be loaded with the Agilent 89601A Vector Signal Analyzer software as well as with MATLAB mathematical analysis software. The Infiniium 90000 X-Series oscilloscopes are supported by more than 40 measurement-specific application packages available as options from Agilent, including jitter, triggering, measurement, and analysis tools and full compliance certification test suites.

The oscilloscopes benefit from the firm's proprietary indium phosphide (InP) integrated-circuit (IC) process. Five custom InP chips are part of a frontend multichip module (MCM) on an aluminum-nitride substrate (Fig. 2). The MCM also incorporates unique noise shielding and heat dissipation techniques to maintain low noise levels even while surrounded by electromagnetic (EM) sources, and to effectively remove heat from the compact MCM circuitry for good long-term reliability.

The Infiniium 90000 X-Series oscilloscopes have tremendous measurement power but also convenience, with a removable hard drive and a dedicated single acquisition button to simplify capturing unique events. The instruments are LXI Class C compliant and allow remote access by means of an Ethernet connection. They are loaded with Universal Serial Bus (USB) ports, with three front-panel USB 2.0 host ports, and four additional USB host ports and one device port on the back panel. Agilent Technologies, 5301 Stevens Creek Blvd., Santa Clara, CA 95051; (877) 424-4536, (408) 345-8886, FAX: (408) 345-8474, Internet: www.agilent.com.