Augmenting the dPX spectrum processing technology in the upgraded analyzers is dPX density triggering, which lets users trigger on “signals within signals” that are obscured by traditional analyzers. with this capability, designers can isolate random, low-level events. examples include sources of self-interference in radar and electronic warfare applications.
Tektronix further enhanced the analyzers with its second-generation dPX live rF spectrum display. This provides more than a sixfold increase in the update rate, which translates into an update rate of 292,000 spectrums per second. it also means a 100% probability of intercept for signals of just 10.3 µs.
“if you had a 2-µs event, the analyzer would still show it with 100% probability, but the amplitude would be at 20% of the level of the 10.3-µs signal,” says darren mccarthy, rF technical marketing manager at Tektronix.
ANALYZING THE NETWORK
Anyone who’s ever had to integrate and maintain the systems required to test transmit/ receive modules, converters, and amplifiers in the aerospace and defense market knows that these systems are massive. multiple racks full of instruments must be deployed to run the hundreds of tests usually conducted on a typical transmit/receive module. These modules are often tested under hundreds of different test conditions in both linear and nonlinear operating conditions.
To address these requirements, Agilent expanded its PnA-X series of network analyzers to include 43.5- and 50-GHz models (Fig. 3). with double the frequency coverage of existing PnA-X analyzers, highly integrated and versatile hardware, and reconfigurability by means of internal switch banks, these instruments can potentially replace a large portion of those multiple racks of instruments. Functions now included within the PnA-X instruments include vector network analysis, signal sources, spectrum analysis, pulse pattern generators, pulse modulators, and switch matrices.
when it comes to active device tests for wireless communications, Agilent provides a 13.5-GHz version of the PnA-X. in the wireless arena, active devices such as power amplifiers, low-noise amplifiers, front-end modules, and up/down converters are tested at a series of test stations for different requirements. These include small-signal s parameters for linear performance, high-power gain or pulsed rF stimulus, distortion, and noise figure. Again, the 13.5-GHz PnA-X comprises a single test station that makes the test process extremely efficient.
Because the PnA-X is so highly integrated, it enables multiple measurements with one connection. This benefit takes on greater importance in on-wafer device tests. in typical test setups involving multiple stations, the act of attaching probes can scratch device bonding pads to the point where subsequent wire bonding suffers. The PnA-X sidesteps this potential for damaging devices in the testing process.
Agilent also released nonlinear vector versions of the 43.5- and 50-GHz network analyzers, which deliver accurate nonlinear characterization of higher-frequency devices. These instruments, claimed by Agilent as industry firsts, are based on the standard PnA-X units, so they also incorporate all of the linear measurement capabilities.
in nonlinear mode, all of the input and output spectra of the device under test (dUT) are measured. Both the amplitude and phase of the full spectra, including fundamental, harmonics, and cross-frequency products, are displayed. relative phase and absolute amplitude of any of the frequencies of interest can also be displayed.
one interesting potential application of the nonlinear analyzer is the creation of X-parameter models for use within Agilent eesof’s Advanced design system, which simulates actual linear and nonlinear component behavior. in traditional top-down design specifications, precious little is shared with ic designers to describe how the chip should behave in typical operating conditions. That results in a tedious, iterative process of tweaking to satisfy system-level performance requirements.
A better methodology is for network equipment manufacturers to use the nonlinear analyzer to generate X parameters that describe much more comprehensive systemlevel performance requirements (Fig. 4). These requirements can be shared with IC designers without providing detailed specifications for all operating conditions. Then, during the IC design cycle, the IC designers can send back their own X parameters to the equipment manufacturers for verification before prototyping.
During the prototyping phase, designers can use those same X parameters to thoroughly simulate the IC’s responses to various realworld operating conditions. These X parameters accurately represent the responses and are transferable to the circuit-level or system-level simulation so the equipment designer can effectively optimize system-level performances with little iteration.
Reprints
