HP 5965-7009E free download

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8 Hints for Better Spectrum Analysis Application Note 1286-1 The Spectrum Analyzer The spectrum analyzer, like an When digital technology first became To get better spectrum analyzer oscilloscope, is a basic tool used for viable, it was used to digitize the measurements the input signal must observing signals. Where the oscil- video signal, as shown in Figure 2. be undistorted, the spectrum ana- loscope provides a window into the As digital technology has advanced lyzer settings must be wisely set for time domain, the spectrum analyzer over the years, the spectrum analyzer application-specific measurements, provides a window into the frequency has evolved to incorporate digital and the measurement procedure domain, as depicted in Figure 1. signal processing (DSP), after the final optimized to take best advantage of IF filter as shown by the dotted box, the specifications. More details on Figure 2 depicts a simplified block to be able to measure signal formats these steps will be addressed in the diagram of a swept-tuned super- that are becoming increasingly hints. heterodyne spectrum analyzer. complex. DSP is performed to pro- Superheterodyne means to mix or vide improved dynamic range, faster to translate in a frequency above sweep speed and better accuracy. audio frequencies. In the analyzer, a signal at the input travels through an attenuator to limit the amplitude of the signal at the mixer, and then through a low-pass input filter to eliminate undesirable frequencies. Past the input filter, the signal gets mixed with a signal generated by the local oscillator (LO) whose frequency Time domain Frequency domain is controlled by a sweep generator. measurements measurements As the frequency of the LO changes, Figure 1. Measurement domain the signals at the output of the mixer, (which include the two original signals, their sums and differences and their harmonics), get filtered by Digital signal processor the resolution bandwidth filter (IF Preselector Resolution Input or input bandwidth Log Envelope filter), and amplified or compressed attenuator filter Mixer filter IF gain amp detector in the logarith