Harmonic mode magnetron
View Patent ↗A novel magnetron achieves increased power output at high frequencies by replacing a typical resonant cavity with a slow-wave waveguide structure. Waveguides built into the anode body sustain oscillations having phase change coefficients of 2*pi*n radians per section, where n is a positive integer. The magnetron is capable of supporting RF oscillations at frequency harmonics of the fundamental frequency, permitting it to operate at frequencies double or quadruple that of a similarly sized conventional magnetron.
1. A harmonic mode magnetron for converting DC electrical current to radio frequency (RF) power comprising:
an anode body formed from a conductive material and including a central cavity; and
a cathode fixed within the central cavity of the anode body;
wherein the anode body further comprises at least two slow-wave waveguide structures formed within the anode body, each slow-wave waveguide structure comprising a channel having a rectangular cross section cutting through the anode body in a continuous path and having two openings into the central cavity such that the two openings and the channel define a central column of anode body material between them and wherein the central column forms one broadwall of the slow-wave waveguide structure and wherein another broadwall of the slow-wave waveguide structure is formed from the anode body.
2. The harmonic mode magnetron of claim 1 , wherein each slow-wave waveguide structure further comprises one narrow wall formed from the anode body material and another narrow wall formed from a cap material joined to the anode body.
3. The harmonic mode magnetron of claim 1 , wherein each slow-wave waveguide structure further comprises two narrow walls formed from the anode body material.
4. The harmonic mode magnetron of claim 1 , wherein the anode body is formed from copper.
5. The harmonic mode magnetron of claim 1 , further comprising mode-isolating structures for suppressing certain harmonic oscillation modes.
6. The harmonic mode magnetron of claim 5 , wherein the mode-isolating structures comprise irises disposed within at least one of the slow-wave waveguide structures.
7. The harmonic mode magnetron of claim 6 , wherein at least some of the irises disposed within at least one of the slow-wave waveguide structures are transmitting irises.
8. The harmonic mode magnetron of claim 6 , wherein at least some of the irises disposed within at least one of the slow-wave waveguide structures are non-transmitting irises.
9. The harmonic mode magnetron of claim 5 , wherein the mode-isolating structures comprise resonant high-Q cavities constructed with a resonant frequency corresponding to a desired operating frequency of the harmonic mode magnetron.
10. The harmonic mode magnetron of claim 9 , wherein the mode-isolating structures comprise discrete high-Q cavities coupled to each slow-wave waveguide structure.
11. The harmonic mode magnetron of claim 9 , wherein the mode-isolating structures comprise a coaxial cavity coupled to multiple slow-wave waveguide structures.
12. The harmonic mode magnetron of claim 1 , wherein the anode body includes an odd number of slow-wave waveguide structures such that the π resonant mode is suppressed.