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Industry News

An RF Component Analyzer for Measuring Multi-function RF Modules

February 27, 2004
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Communications services such as mobile phone and wireless LAN have increased the use of multi-bands while the terminals are becoming smaller. These trends have led to the widespread use of RF modules combining multiple functions. Along with this trend is the ability to make increasingly complex measurements more efficient.

A new generation of analyzers with the flexibility to handle all tasks requiring high accuracy, high speed measurements and superior analysis functions has been developed. The model R3860A RF component analyzer is a new instrument with the flexibility to measure RF modules that combine multiple functions. Its capability extends over a wide range of uses from multi-function RF modules to frequency conversion circuits and other active components.

Complementing the new R3680A analyzer is the model R3768/3770 network analyzer, a high performance multi-port analyzer designed with a greater emphasis on measuring passive components. Together the R3680A/ 3768 combination supports frequencies from 300 kHz to 8 GHz and the R3680A/3770 supports frequencies from 300 kHz to 20 GHz.

All models have the software fixture function that performs real-time simulation of virtual matching circuits and standardized impedance conversion in addition to S-parameter analysis. At an ultra-fast sweep speed of 5 ms/point, simulations of complex analysis are also accomplished instantly. Moreover, multi-port models can perform software balun simulations and balance parameter analysis. If these models are combined and used with the flexible multi-window and multi-trace functions, they can also measure complex analysis items instantly. Also, the large, high visibility display is a key factor in improving the analysis efficiency because it enables the simultaneous display of multi-port paths in addition to the simultaneous display of fixture simulation traces.

Table 1 lists the significant characteristics of the R3860A combined with either the R3768 or R3770 network analyzers. The analyzer provides several interfaces that allow connection to a variety of external instruments. The instrument’s front panel comes standard with mouse and keyboard connectors, and the rear panel has GPIB, LAN, printer port and VGA monitor output connectors. In addition, the parallel port built into the analyzer provides two channels of 8-bit output ports and two channels of 4-bit inputs and outputs.

Performance

Utilizing a system dynamic range of up to 125 dB, a greater range of RF components and modules can be measured. With the 5 ms/point measuring speed and 16 measurement channels, the analyzer can be used for a wide variety of applications such as design, evaluation and front-end inspection of multiple function modules.

Fig. 1 16 channel sweep screen.

Fig. 2 16 trace/window display screen.

To support the higher frequencies being used today for wireless LAN communications in the 5 GHz band and standards for measuring higher cell phone harmonics, a greater measuring range for wider bands is needed. The R3860A provides an application package with an upper limit of 20 GHz and is suitable for measuring devices at the most recent performance standards.

Applications

With 16 independent sweep channels, the frequency range, number of sweep points and output power can be set for each measurement path. The status of multiple channels can be displayed in a dialog box and the sweep results displayed in multiple images, as shown in Figure 1. The customizable user interface dramically improves operability for multi-port devices requiring complex settings.

For normal S-parameter analysis, 16 parameters can be analyzed for a four-port device. In addition to the S-parameter analysis, a comprehensive evaluation requires a variety of simulation data that can be obtained using the software fixture function. When simultaneous analysis of multi-port devices is performed using the multi-port test set, the efficiency of the analysis is greatly improved by displaying more of the information at the same time. This is made possible by the built-in 12.1" SVGA large TFT LCD that can display more analysis results with better visibility and the multi-window function that allows a viewing window to be split into as many as 16 windows, as shown in Figure 2. With this flexibility, it is possible to support a wide variety of measurement environments simultaneously.

One of the options available to the R3860A/3678/3770 instrument is a test set for full S-parameter measurements for up to four ports. For module devices that have more functions, up to 11 ports are supported after connection of the R3968 multi-port test set (option).

Software Fixture

The widespread use of balanced input/output devices has increased the demand for a software fixture function that simulates virtual fixtures. A software fixture is provided as a standard function on all models to address these requirements.

Characteristics obtained by virtual addition of a matching circuit to the measuring port can be simulated in real time. Matching condition changes can be easily calculated by entering the topology of components and constants directly from the keyboard. For cases when a more complex matching circuit is added, the S-parameter file can be read externally. Figure 3 shows an example of software fixture settings.

Fig. 3 Example of software fixture settings (measurement uses MDAS-PRO).

In addition, a delete circuit can remove predefined error sources as an S-parameter file. Other capabilities include an impedance conversion function for measuring devices with an impedance other than the standardized 50 W. A software balun enables a balanced circuit to be replaced with unbalanced parameters. A balance parameter enables intuitive analysis of how close a balanced circuit is to its ideal value, and a mode analysis permits the S-parameter in each mode to be analyzed separately focusing on the common mode and the differential mode for input/output of a balanced circuit.

Nonlinear Analysis

In addition to the signal source for sweeps, a second signal source may be added, extending the use of the analyzer. Because both signals and the frequency range in the receiving section can be controlled independently, new measuring methods can be utilized for filter harmonic measurements. The addition of a second signal provides a still wider range of measurement targets, including mixers and other nonlinear devices.

Controlling the phase of the second signal source so that it is a completely local signal source allows mixer characteristics to be measured with vector values to a high degree of accuracy. Sweep, Fixed or Auto mode can be selected as the local signal for the signal output from the second signal source. In addition, the frequency sweep of the receiver section is easily set from the mixer measurement dialog box, as shown in Figure 4. Figure 5 shows a typical measurement sample for a mixer/filter combined circuit.

Fig. 4 Dialog box for mixer measurement settings.

Fig. 5 Measurement sample for combined circuit of a mixer and filter.

A built-in function enables the operator to independently set the frequency ranges of the signal source, second signal source and the receiving section. This capability, shown in Figure 6, enables harmonic measurement when a signal enters the basic waveband of a filter. The availability of this function also means an external signal generator and spectrum analyzer are not needed, thus lowering design evaluation and production process costs.

Fig. 6 Multi-frequency function setting.

Conclusion

A new generation RF component analyzer series has been introduced that is significantly faster (5 ms/point) with a frequency range that extends to 20 GHz. The analyzer is particularly aimed at multi-function module applications where complex measurements involving multiple ports are required. The new instrument features an increase in dynamic range, much improved crosstalk performance, lower trace noise and higher output power than its earlier version. The R3860A RF component analyzer, along with its associated R3768/3770 network analyzer, is currently available along with optional support accessories. Additional information is available on the company’s Web site or by phone.

Advantest America
Measuring Solutions Inc.,
Edison, NJ (866) 414-0870, www.advantest.com/instruments.

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