  The reflectionless filter cell described in this article alleviates many
system problems associated with excess out-of-band gain, impedance mismatches,
and component interactions. The simplest filter cell exhibits a third-order
Inverse Chebyshev response with 14.47 dB peak stopband attenuation, and several
can be cascaded for additional attenuation as needed. They are simple to design
and easy to use - for much like small fixed attenuators ("pads"), they can be
placed anywhere in the signal path desired without fear of causing unwanted
standing waves, and instead reducing them where they already exist beyond the
intended frequency range. Compared to conventional filter topologies with
similar cutoff frequencies, they exhibit an order of magnitude greater
amplitude and phase stability, ensuring accurate and repeatable complex gain in
calibrated systems. Finally, the component requirements are moderate in value
and minimal in number, easing their implementation while improving design
yield, and extending the applicability of a given component technology beyond
the normal range, both above and below.
