# US 10,865,760 B2 · Compact electromagnetic plasma ignition device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,865,760 B2 - Document ID: US10865760B2 - Status: Granted - Kind: B2 - Application number: 15/454,418 - Filed: 2017-03-09 - Published: 2017-06-22 - Granted: 2020-12-15 - Earliest claimed: 2008-01-31 - Assignees: West Virginia University - Applicants: West Virginia University - Inventors: James E. Smith; Franz A. Pertl - Web page: https://patentgrep.com/patent/US10865760B2 ## CPC - F02P 9/007: {by supplementary electrical discharge in the pre-ionised electrode interspace of the sparking plug, e.g. plasma jet ignition} - F02P 3/01: Electric spark ignition installations without subsequent energy storage, i.e. energy supplied by an electrical oscillator (with magneto- or dynamo-electric generators F02P1/00; piezoelectric ignition F02P3/12; with continuous electric spark F02P15/10) - F02P 23/045: {using electromagnetic microwaves} - H01J 37/32091: {the radio frequency energy being capacitively coupled to the plasma} - H01T 9/00: Spark gaps specially adapted for generating oscillations - H01T 13/50: having means for ionisation of gap (H01T13/52 takes precedence) - H01T 19/00: Devices providing for corona discharge (for charging electrographic elements G03G15/02) - F02P: IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES ({anti-pollution means for internal-combustion engines F02B17/00}; specially adapted for rotary-piston or oscillating-piston engines F02B53/12; {ignition of gas turbine plants F02C7/26; ignition of jet propulsion plants F02K9/95; starting of combustion engines F02N9/00}; ignition of combustion apparatus in general, glowing plugs F23Q; measuring of physical variables in general G01; controlling in general G05; data processing in general G06; electrical components in general see Section H; {ignition coils H01F38/12}; sparking plugs H01T13/00) - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) - H01T: SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES (overvoltage protection circuits H02H) ## Abstract A quarter wave coaxial cavity resonator for producing corona discharge plasma from is presented. The quarter wave coaxial cavity resonator has a folded cavity made of opposing concentric cavity members that are nested together to form a continuous cavity ending in a aperture. A center conductor with a tip is positioned in the cavity. The folded cavity advantageously permits the coaxial cavity resonator to resonate at a lower operating frequency than an unfolded quarter wave coaxial cavity resonator of the same length. Embodiments of the quarter wave coaxial cavity resonator use narrower apertures to reduce radiative losses, and include center conductors that are reactive load elements, such as helical coils. When a radio frequency (RF) oscillation is produced in the quarter wave coaxial cavity resonator, corona discharge plasma is formed at the tip of the center conductor. The corona discharge plasma can be used to ignite combustible materials in combustion chambers of combustion engines. ## Claims ### Claim 1 A quarter wave coaxial cavity resonator, comprising: a plurality of concentric nested cavity members arranged to form a folded cavity, the plurality of concentric nested cavity members including an outer concentric hollow conductor and an inner concentric hollow conductor defining an aperture; a reactive load center conductor including a tip, at least a portion of the reactive load center conductor disposed in the folded cavity, wherein the folded cavity is coupled to a radio frequency power source to produce a sustained RF oscillation of an operating wavelength in the quarter wave coaxial cavity resonator, wherein the operating wavelength is derived from an operating frequency in a range between 750 MHz to 7.5 GHz, wherein an RF corona is formed at the tip of the reactive load center conductor when the sustained RF oscillation of the operating wavelength is produced in the quarter wave coaxial cavity resonator, and wherein a length of the folded cavity is no longer than approximately one fourth of the operating wavelength. ### Claim 2 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, wherein the reactive load center conductor is a corrugated reactive load element. ### Claim 3 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, wherein the reactive load center conductor is a dielectric coated center conductor. ### Claim 4 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, further comprising a threaded body surrounding the aperture and adapted to fit a spark plug socket. ### Claim 5 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, further comprising a dielectric seal positioned about the reactive load center conductor. ### Claim 6 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, wherein the tip is generally cylindrical. ### Claim 7 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, wherein the tip is generally spherical. ### Claim 8 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, wherein the tip is curved. ### Claim 9 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, wherein the tip includes a point. ### Claim 10 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, wherein the tip is generally teardrop shaped. ### Claim 11 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, further comprising a loop coupling to couple an energy shaping circuit to the reactive load center conductor of the quarter wave coaxial cavity resonator. ### Claim 12 (depends on 1) The quarter wave coaxial cavity resonator of claim 1, wherein the tip of the reactive load center conductor extends through the aperture.