Agilent Making Stimulus Response Measurements - Application Note 5991-1877EN [9] free download

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Application Note Making Stimulus/Response Measurements Using the Agilent N9322C Basic Spectrum Analyzer and Tracking Generator The tracking generator provides a cost-effective way for spectrum analyzer users to expand their testing to cover more component-level characterization. Introduction to Tracking Generators A tracking generator is a signal source whose RF output follows the tuning of the spectrum analyzer. The tracking generator output signal is generated by mixing the signals from two or more oscillators. A simplified block diagram is shown in Figure 1. ATT PRE filter Mix IF filter RF IN DSP Fs F if Device Control & LO S display TG OUT F's F'if S Filter Mix LO Figure 1. Block diagram of tracking generator The tracking generator uses the Swept LO from the spectrum analyzer and mixes that LO signal with a stable, fixed oscillator. If we tune the oscillator in the tracking generator (F'if) to the center frequency of the IF filter in the spectrum analyzer (F if), and use the difference mixing product, then the output frequency of the tracking generator (F's) will equal the input frequency of the spectrum analyzer (F s). The spans of the spectrum analyzer and tracking gen- erator are matched and synchronous and therefore precise tracking is achieved. Benefits of Using a Tracking Generator 1. It stretches your instrument budget -- One instrument provides dual-purpose measurements. In addition to measuring signal amplitude characteristics such as carrier power, sidebands, and harmonics, a spectrum analyzer with a tracking generator can also make scalar network analysis with high dynamic range, such as the insertion loss, pass/stop band of a component, or the gain of an amplifier. For example, adding a tracking generator to your N9322C BSA provides single- channel scalar network analysis in addition to the analyzer's spectrum analysis capabilities. DUT Figure 2. Using N9322C and its tracking generator for scalar network analysis 2 2. It is effective for scalar transmission measurements --The tracking generator output and the RF input of the spectrum analyzer are well synchronized. The precise tracking between the tracking generator and the analyzer estab- lishes a well-synchronized stimulus/response measurement system. It is able to cover scalar transmission measurements such as gain, frequency response, insertion loss, and