SAW-Stabilized Tunnel-Diode Oscillators: Prior Art for the Microwatt Microwave (M2) Oscillator

The Microwatt Microwave (M²) Oscillator presents as its key contribution an oscillator that couples a tunnel diode with a high-Q surface-acoustic-wave (SAW) resonator to achieve few-ppm frequency stability on a microwatt budget, and states that the two components were "never combined to produce a stable oscillator," framing stable low-power microwave generation as having been "considered impossible." This comment documents that the combination was conceived, built, and characterized in the open literature four decades earlier — most directly by Kmita, Kundin, and Maltsev (1984), "A tunnel-diode oscillator with an SAW resonator" — within a Soviet line of SAW-stabilized oscillators (1978–1983) and a deeper lineage of crystal-stabilized microwatt tunnel-diode transmitters documented in a 1964 handbook. It shows that the central novelty claim conflicts with this record, that the conflict is visible within the paper's own bibliography, and that the omitted prior art is available in English. The measurements and systems-level results of M² are not disputed; the contribution should be restated as a quantitative and systems-level advance over four decades of prior work rather than as the invention of the circuit concept.