page_title: Warren P. Mason
section_title: Work
hierarchical_section_title: Warren P. Mason / Work
caption_attribution_description: English: A microstrip hairpin filter followed by a low pass stub filter on a PCB in a 20GHz Agilent N9344C spectrum analyser
context_page_description: Warren Perry Mason was an American electrical engineer and physicist at Bell Labs. A graduate of Columbia University, he had a prolific output, publishing four books and nearly a hundred papers. He was issued over two hundred patents, more than anyone else at Bell Labs. His work included acoustics, filters, crystals and ceramics, materials science, polymer chemistry, ultrasonics, bonding to semiconductors, internal friction, and viscoelasticity.
  Mason founded the field of distributed-element circuits. He was the first to experimentally show viscoelasticity in individual molecules. He found experimental evidence of electron-phonon coupling in solids and made measurements that aided the theories of phonon drag and superconductivity. Many of Mason's inventions in electronics are still widely used by modern circuit designers.
context_section_description: Mason's work covered a wide range of fields.  A large part of his work concerned filtering, not only in the electrical domain, but also in the mechanical and acoustic domains.  Other fields of study included piezoelectric crystals and ceramics, ferroelectric crystals, underwater sound transducers, bonding of metals to metals and semiconductors, physics of wear, semiconductor strain gauges, metal fatigue, and internal friction of solids and liquids.
  Mason worked on mechanical filters, a key component of frequency-division multiplexing in telephone carrier systems.  They can be made with much sharper transition bands than can be achieved with conventional LC filters.  Mason invented a new type of mechanical filter, the quartz crystal filter consisting of lattices of crystals, which became the standard form of filtering on these systems.  Mason showed that the efficiency and bandwidth of acoustic transducers, such as those used in sonar, could be massively improved through mechanical-electrical analogies and applying electrical network theory, in particular filter theory.
  Mason's doctoral thesis was on acoustic filters and horns.  In this work, Mason pioneered the use of the distributed-element model to describe acoustic filters.  He later extended this work for distributed electrical filters and distributed mechanical filters, making him the founder of the field of distributed-element circuits.
  Mason was head of the Crystal Research Department 1935–1948, which studied piezoelectric crystals.  He invented the GT crystal cut which has a near zero temperature coefficient of its resonant frequency.  The crystal is widely used where accurate frequency is required such as in frequency standards and filtering.  Other materials studied were ammonium dihydrogen phosphate, used in sonar transducers, barium titanate, an electrostrictive material, and ethylene diamine tartrate.  The latter material was studied as a possible solution to the shortage of Brazilian quartz, since it was water-soluble and hence growable in the laboratory.  However, it became unnecessary once quartz crystal growing was possible.
  During World War II, Mason was tasked with finding a stronger material than neoprene to make sonar domes.  The requirement was for a material that retained neoprene's good match to the sonic transmission properties of sea water but had an elastic modulus thousands of times greater.  Mason tried mixtures based on cellulose esters whose smell was so bad he was driven out of the lab to a nearby lake to do the testing.  This led him to complain that polymer chemistry was not "civilized national defense."  Other war work included crystal transducers for sonar and torpedoes, crystal delay lines for radar, and gun silencers.
  From 1948, Mason was head of the Mechanics Research Department.  Together with Ronald Wick, Mason invented the Mason-Wick horn, a mechanical impedance transformer.  This consisted of a solid, exponentially tapered barium titanate rod and was used in experiments to amplify mechanical vibrations.  One such type of experiment concerned internal friction and fatigue in metals.
  In ultrasonics, Mason provided the first demonstration of single-chain viscoelasticity in which the elasticity is due to the individual molecular chains themselves rather than their entanglement.  In 1956 Mason and H. E. Bömmel found experimental evidence for electron-phonon coupling in pure samples of lead and tin.  The work was relevant to measurement of parameters in BCS theory of superconductivity.  In 1964 Mason and T. B. Bateman measured attenuation and velocity changes in doped germanium and silicon.  This work helped quantify the theory of phonon drag in semiconductors.  Mason used ultrasonics to develop his theory that internal friction in metal alloys and rocks was due to dislocations.
caption: A modern distributed-element circuit.  Such circuits are based on the principles established by Mason.  This one is a band-pass filter followed by a low-pass filter
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