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Summary: Chapter 2
Synchronous Undersampling and
the LazyFish
This chapter describes the LazyFish, a board I designed that implements 8 channels of
Electric Field Sensing in a very small footprint. Its small footprint is made possible by my
Synchronous Undersampling technique, which is explained in this chapter. Before doing
so, I will review some other implementations of electric eld sensing, starting with the
Theremin.
2.1 Background
2.1.1 Theremin
Figure 2-1 shows a schematic of Clara Rockmore's Theremin, drawn by Bob Moog in 1989.
Here is a back of the envelope" analysis of the sensing and pitch synthesis. Changes in
hand proximity a ect the capacitance in one LC resonant circuit the one on the right side
of the gure, with the labeled pitch antenna, changing its resonant frequency. Though not
all component values are provided in this diagram, if we assume L = 38uH and C = 663pF,
the resonant frequency f = 1
2
p
LC
= 1MHz and Q =
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