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Network Analyzer Software for Simplified Bandpass Filter Tuning
Agilent Technologies Inc.
Santa Rosa, CA
Tuning the multiple poles and zeros of a coupled-resonator bandpass filter is generally labor-intensive and time-consuming. Often performed by a company's most experienced technicians armed with a vector network analyzer, such tuning requires tuning the center frequency of each resonator as well as the coupling between resonators. The Agilent N4261A filter tuning application software works with many of the company's vector network analyzers to dramatically reduce the complexity of filter tuning, and makes it possible for individuals without extensive experience or technical skill to quickly tune coupled-resonator bandpass filters with a high degree of accuracy.
The N4261A software package is based on patent-pending time-domain and proprietary filter tuning techniques. While most filter tuning techniques are based on adjusting resonators while observing the filter's amplitude response as a function of frequency (frequency domain), the N4261A software makes use of the time-domain, in which filter responses, such as the change in impedance that occurs at each resonator, are displayed as a function of time from the launch of the initial test signal.
The software works with a vector network analyzer with fast sweep speed and two-port measurement capability. The software has been qualified for use with the firm's PNA Series of RF Network Analyzers as well as with an 8753ES Series network analyzer, an 8753D or an 872xD Series analyzer with an upgraded CPU board, or an 872xES analyzer, interfacing through the GPIB port.The software can operate internally in the PNA Series analyzers due to the instruments' powerful Windows 2000-based embedded computer. The N4261A software controls the other network analyzers from an external personal computer running under Windows 2000 and NT environments.
By controlling a vector network analyzer, the software can quickly identify each resonator in a coupled-resonator bandpass filter, its center frequency and the coupling between resonators. Using this information, the software creates intuitive graphic tuning indicators on the screen of a PNA Series analyzer or on the personal computer's screen (for the other analyzers) that an operator can follow to adjust each resonator and achieve proper coupling between resonators. These visual indicators quickly inform an operator when a filter is tuned within acceptable limits based on parameters supplied during software/test-system setup.
The use of the N4261A filter tuning software and a properly equipped vector network analyzer allows operators without extensive experience to perform filter tuning. Operators can use the simple, intuitive on-screen controls to set up reference filter performance parameters as a reference for other measurements. New operators do not have to interpret a trace on a vector analyzer but can rely on the software to help quickly and accurately tune each resonator, and adjust the coupling between resonators to obtain the desired optimum filter response. The software allows as many as four real time S-parameters and their corresponding reference traces to be displayed in each window to simplify tuning of filter amplitude response as well as time delay and return loss.
With the continued growth of wireless applications, the demand for high quality bandpass filters and multiplexers has also grown. Use of the N4261A filter tuning software and a PNA Series, 8753ES Series, 8753D, 872xD or 872xES vector network analyzer can help filter manufacturers meet those demands in a timely fashion, without requiring long tuning times or highly skilled technical personnel. The filter software is supplied on a CD-ROM with future upgrades available over the Internet. Additional information may be obtained from the company's Web site at www. agilent.com/find/fts.
Agilent Technologies Inc.,
Santa Rosa, CA (800) 452-4844.
Circle No. 300
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