Introduction: Esterline Research and Design (ERD) is a frequency control company that designs and manufactures oscillators and test and measurement gear for the oscillator industry. As a consequence, we also manufacture high-high end counter products to qualify and test those time bases. Instead of using reciprocal RF counters at the output frequency of the DUT (device under test), we use the heterodyne method to increase resolution and increase channel to channel isolation by mixing down to audio frequencies instead of counting RF. The following will focus on how the heterodyne method dramatically increases counter resolution. Figure 1: Down converter block diagram..

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