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test&measurementZONE Products for the week of June 8, 2009
Agilent Technologies Says…
World's Most Flexible PNA-X Network Analyzer for Active Device Test with 13.5, 43.5, 50 GHz Models
New Models Include Industry-First 50 GHz Nonlinear Vector Network Analyzer
Agilent Technologies Inc. expands the world's most flexible PNA-X network analyzer with 13.5, 43.5 and 50 GHz models. The 43.5 and 50 GHz models support higher frequency applications such as radar and satellite communications, while the 13.5 GHz model is ideal for lower-frequency devices used in wireless communications. Agilent's award winning PNA-X nonlinear vector network analyzer (NVNA) has also been expanded to include a 13.5 GHz model and the industry's first 43.5 and 50 GHz NVNA. These new solutions provide engineers developing and manufacturing active devices the flexibility to select just the right frequency that is required for their specific application.
Aerospace and defense engineers working up to 50 GHz can now benefit from Agilent's single-connection, multiple measurements PNA-X. This analyzer's integrated measurements, versatile hardware, and re-configurable measurement paths address this market's key challenges: test system costs, test complexity, throughput gains, accuracy and equipment space. Typical radar, satellite and electronic-warfare applications require complex test systems with multiple racks of instruments and numerous connections to the device under test. The PNA-X integrates the capabilities of a full rack of equipment into a single instrument, simplifying test stations, reducing equipment count by 50 percent, and increasing throughput by 400 percent. The PNA-X also offers a unique single contact solution for on wafer tests. This approach significantly improves quality by eliminating multiple probe contacts and enabling the most accurate characterization and reliable wire-bonding. Additionally, engineers working above 50 GHz can use the PNA-X to configure a banded mm-wave system up to 0.5 THz.
The 13.5-GHz PNA-X model supports lower frequency devices used in the wireless communications market where reduced test time, number of test stations and test cost is critical. With low-noise amplifier tests there are typically multiple test stations, such as small signal gain/match, distortions, and noise figure; the PNA-X integrates these test stations into one. By integrating measurements from multiple test stations into one, the PNA-X reduces the number of test stations by as much as 75 percent and reduces costs by 30 percent.
The industry's first 43.5 and 50 GHz NVNAs and new 13.5 GHz model now bring the NVNA solution to engineers working in the RF and microwave frequency ranges. Agilent's NVNA is the industry's first measurement and simulation environment for designing nonlinear components. The result is the highest level of insight into nonlinear device behavior, making the NVNA capability especially useful for scientists researching new RF technologies and engineers involved in designing today's high-performance active devices. Using NVNA, X-parameters are measured and then used to create X-parameter models that can be imported into Agilent's Advanced Design System (ADS) to simulate actual linear and nonlinear component behavior.
"The new PNA-X models, coupled with the industry's widest range of measurement applications, provide engineers with flexibility that was previously not possible," said Gregg Peters, vice president and general manager of Agilent's Component Test Division. "Engineers can build their optimal test system by selecting the frequency range and measurements for their specific device test needs without paying for functionality they don't need."
Key Features of the PNA-X Series Network Analyzers:
- Single-connection, multiple measurements. This configurable 2- or 4-port network analyzer offers a unique single-connection solution for CW and pulsed S-parameter, compression, intermodulation distortion (IMD), and noise figure measurements.
- Two built-in high-performance signal sources; the industry's only 2-port network analyzer with an internal second source. Sources offer high output power (+16 dBm), low harmonics (-60 dBc) and a wide power sweep range (40 dB).
- Industry's widest range of measurement applications for amplifiers, converters or modules with linear and nonlinear characterizations. Applications include vector noise figure, gain compression, IMD, true differential and NVNA.
- Internal signal-routing switches. Switches provide increased flexibility for adding signal conditioning hardware or additional test equipment for single connection measurements.
- Only network analyzer with internal pulse modulators and generators for fast, simplified pulse measurements. This advanced capability enables pulse measurements up to 30 times faster compared with other analyzers that require external generators and modulators.
EN-Genius Says…
With the upgrading of its instrumentation for taking X-parameter readings at frequencies as high as 50-GHz, Agilent Technologies kicks it up a notch for measuring non-linearity, especially in large-signal operating environments. X-parameters are to non-linear measurements what scattering or S-parameters are to linear measurements. In short, X-parameters are Agilent's mathematically correct extension of S-parameters.
If you're an RF engineer, sooner or later you'll be making S-parameter measurements. These are usually derived by means of network analyzers, and are typically used to model small-signal linear components.
Indeed, S-parameters are related to familiar measurements such as S11 input match, S22 output match, S21 gain/loss, and S12 isolation, using network analyzers. Using S-parameters, simple gain-compression, harmonic amplitude only, frequency converter match, conversion loss/gain, and group delay can be measured.
Network analyzers can also provide insight into the non-linear behavior of devices. But, this is typically accomplished using approximation techniques such as un-ratioed receiver measurements and offsetting a measurement receiver's frequency from the source stimulus frequency.
In contrast, X-parameters can be used to analyze non-linear as well as linear behavior of RF components. What's more, X-parameters can do that in a more robust way.
Large-Signal Conditions
As an extension of S-parameters under large-signal operating conditions, devices are driven into saturation and X-parameters are then measured. In this process, no knowledge is required about the internal circuitry of a device under test (DUT). The measurement is a stimulus-response model of voltage. In operation, the absolute amplitude and cross-frequency relative phase of the fundamental, and all related harmonics, are measured and represented by X-parameters.
The process requires two RF sources to simultaneously drive the DUT with both a large-signal and small-signal, at the appropriate frequencies and phases. Control of phase and the amplitude of these signals is critical.
Measuring the amplitudes and phases of the scattered waves then yields X-parameter information, revealing information about device gain and impedance matching. This is especially important in on-the-air systems, where linearity of RF amplifier stages is paramount.
Non-linearity broadens radiated signals and wastes spectrum space, so RF power amplifier Q points are sometimes placed on their load lines so they act as linear amplifiers, but that's power-inefficient.
Many amplifier designs are driven into non-linearity and then linearized. Non-linear operation is used to get maximum output power and efficiency, but feedback is needed to force the PA to behave like a high-power linear amplifier, even though it isn't.
In such designs, suppressing the PA's harmonics is often accomplished with lowpass or bandpass filters. But, if the filter's input impedance doesn't match the output match of the specific harmonic of interest generated by the amplifier, then the harmonic's attenuation level could be significantly different from what's anticipated. This can cause you to resort to brute force trial-and-error cut-and-try filtering.
 That underscores why it's increasingly important to understand the non-linear behavior of active RF components from the get-go. But, making non-linear measurements isn't an easy task, especially considering currently available tools and models.
What's needed is a way to accurately measure and simulate the non-linear effects of active RF devices, and that's where Agilent's PNA-X comes in.
Agilent provides two primary methods for measuring the non-linear effects of a DUT. One is non-linear component characterization and the other is X-parameters. The former provides calibrated, vector-corrected waveforms of incident, transmitted, and reflected waves from a DUT. Vector calibration, power calibration, and the use of a harmonic phase reference calibration then remove systematic error terms.
For their part, X-parameter measurements, requiring two signal sources, drive the DUT with both a large and small signal tone at the appropriate frequencies and phases. The X-parameters are extracted into Agilent's Advanced Design System (ADS) software, or are displayed like S-parameters.
 However, because X-parameters relate cross-frequency dependencies, there are usually many more X-parameters than S-parameters. For example, in the case of the gain of an output fundamental frequency to an input's third harmonic, there are eight X-parameters. And this is for only one harmonic and no power dependency (in contrast, there can never be more than four S-parameters).
X-parameters also depend explicitly on the large signal state of the device (making input power a variable). In contrast, S-parameters are assumed to be power-independent. X-parameters, however, give you accurate phase and amplitude information that can be ported to a simulator such as ADS. That lets you design an optimized system in the shortest time, and with a high degree of accuracy. You can examine both non-linear component characterization and X-parameters to accurately measure a device's non-linear behavior.
Full Characterization
With Agilent's NVNA (Nonlinear Vector Network Analyzer) non-linear component characterization, all of a DUT's input and output spectra are measured. Both the amplitude and phase of the full spectra (the fundamental, the harmonics, and all cross-frequency products) are then displayed in the PNA-X. The relative phase and absolute amplitude of any of the frequencies of interest can be displayed, and the data can be shown in the frequency, time, or power domains, as well as in terms of user-defined ratios such as I/V to display dynamic load lines.
With the ability to display data in the different domains, Agilent's NVNA will give you insight into non-linear component behavior. For example, if the DUT's output is distorted in the time domain, you can change to the frequency domain and observe individual frequency component amplitude and phase.
Similarly, power can be varied to observe the sensitivity and level of significance which that spectral component has for given power levels, relative to the fundamental frequency. If you were measuring a frequency doubler, for example, you can use the NVNA to measure the input and output stimulus phase relative to a calibrated phase reference, as well as the signal's amplitude.
An Integrated Environment
As pointed out in the company's press release, all of this is accomplished in one integrated instrument environment. With minimal external hardware, Agilent's NVNA converts its existing 4-port PNA-X network analyzer into a high-performance non-linear analyzer.
You get high power to drive amplifier into compression. You also get signal purity so you can test for harmonic distortion and IMD (intermodulation distortion). The combo of high output-power and low harmonics also can simplify test set-ups since you won't need external amplifiers and filters. The PNA-X also offers highly stable RF levels, which can ease calibration and save cal times.
Additionally, these instruments ensure good receiver compression. This is critical to measurement accuracy, especially at high power levels. If the network analyzer isn't well specified, it may inadvertently contribute to the measurement of amplifier compression, harmonics, and IMD.
Agilent's integrated pulse hardware is also nifty. It can simplify making pulsed S-parameter measurements. No external equipment is required.
The second RF generator inside the analyzer also offers a convenient local oscillator signal that can be used for making fast fixed-IF tests of converter and mixers. It can also be used as one of the RF signals when making IMD measurements.
Similarly, an internal source-combining network eliminates the need for an external combiner. With the internal combiner, S-parameter and IMD tests can be performed without having to change test set-ups.
Having a configurable signal routing architecture also gives you the flexibility to make a range of measurements with multiple pieces of test equipment using a single connection to your DUT. You won't have to modify a test equipment set-up to make additional measurements. However, the signal routing capability of Agilent's equipment also lends itself to adding external signal-conditioning hardware such as filters or amplifiers.
For example, an external signal generator with digital modulation capability, and a vector signal analyzer, can be switched to the inputs and outputs of an amplifier to make measurements such as ACPR (adjacent-channel power ratio), EVM (error-vector magnitude), or CCDF (complementary cumulative distribution function).
Finally, the fact that the PNA-X is now available in four frequency ranges also makes it cost effective, as you can select only that frequency model required for your specific application. The expanded PNA-X product promises to speed both R&D and manufacturing throughput, and should be adaptable to a great many measurement scenarios.
Agilent claims its latest PNA-X wares will typically slash test costs by 30%, reduce the number of test stations by 75%, and increase throughput by more than 400%, and I don't doubt it. This highly integrated hardware, with its re-configurable measurement paths, may displace racks full of conventional test gear.
An Arbitrary Load Impedance Option
Agilent also offers an arbitrary load impedance option for the NVNA. The option, when used in conjunction with Maury Microwave tuners and software, lets you accurately measure and simulate non-linear component behavior at all load impedances. Agilent claims this is an industry-first.
 Using the tuners, you can extend X-parameter design cascade-ability to arbitrarily large load mismatches. By removing the constraint for the output match to be either small or moderate, you can measure and simulate linear and non-linear behavior over a load gamma range covering the full Smith chart. Inter-stage matching of components with varying impedances is now predictable in the simulator.
You can also use the tuner options to measure and predict dynamic load-lines at input and output ports under arbitrary loading conditions, even under very large compression. You can additionally use the tuner options to measure and simulate magnitude and phase data at the input and output for each fundamental and harmonic frequency as non-linear functions of power, bias, and arbitrary load impedance. The resulting data can be used for simulation in ADS. You can also design multistage, Doherty, or other complex amplifier circuits using a drag-and-drop human interface in ADS.
Agilent's PNA-X models and PNA-X NVNA options are now available. Pricing is as follows:
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N5241A
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10 MHz to 13.5 GHz |
$76,400 |
| N5242A |
10 MHz to 26.5 GHz |
$98,000 |
| N5244A |
10 MHz to 43.5 GHz |
$125,400 |
| N5245A |
10 MHz to 50 GHz |
$140,100 |
The NVNA options start at $37,400. Agilent's Model U9391F 50-GHz comb generator acts a phase reference for the NVNA frequency extensions. Pricing is $16,000
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