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A compact high-power four-port circulator aiming to simplify the conventional, complex, and bulky injection-locking magnetron system is proposed. To reduce the performance deterioration and the risk of ferrite rupture under long-term high-microwave-power condition, the method of breaking a monolithic ferrite into three discrete ferrites in a conventional three-port circulator is proposed. To miniaturize the size and cost of the four-port circulator, a butterfly-shaped waveguide structure is proposed, with a stub inserted into the cavity at the central point and with no connecting waveguide. Multiphysics simulation results show that the temperature coefficient of variation (COV) at the surface of the discrete ferrites is 12.4% lower than that of a monolithic ferrite circulator, with input microwave power of 10 kW. The size of the proposed four-port waveguide circulator is 27% less than the assembly of two three-port circulators, and way smaller than a conventional differential phase shift circulator (DPSC). The simulated and measured S-parameters match well, and the measured power capacity of the fabricated circulator is higher than 3 kW (limited by the experimental condition). A magnetron is successfully locked using only one designed compact circulator. The research in this paper promotes the development of injection-locking magnetron and provides a design example for the compact, high-power circulator. [ABSTRACT FROM AUTHOR]

A microwave power-combining technique based on magnetrons has been widely researched to solve the urgent demands for high-power, low-cost microwave sources in microwave industrial applications. To achieve high resultant efficiency, conventionally, injection locking with static frequency is utilized to drag the output frequency of each magnetron source to the exact same frequency, and a phase shifter is required to adjust the output phase of each combining source. In this article, we propose a novel phase shifterless microwave power system with two magnetrons utilizing a frequency-searching injection-locking technique. Coaxial cables with different physical lengths are used to realize phase adjustment under different injection frequencies. By sweeping the injection frequency in a small band, the phase difference between combining signals can be adjusted. Thus, high resultant efficiency can be obtained. When the injection frequency is swept, the phase difference between the output and injection signals has been analyzed theoretically, the phase difference between the different-length coaxial injection cables has also been analyzed. Furthermore, the relationship between the sweeping frequency bandwidth and requirements of the minimum length difference of the coaxial injection cables has been derived and analyzed. Experimental results show that a high resultant efficiency of 94.6% can be obtained with the proposed phase shifterless system. The system could maintain high resultant efficiency even when the free-running frequency and power of one magnetron are changed by adjusting its anode current. The experiments reveal that the proposed method works for different combining sources. [ABSTRACT FROM AUTHOR]

Jamming signals are usually generated by solid-state microwave sources that are high in cost, low in efficiency, and fragile. In this article, we present a novel approach in which a high-power jamming signal is generated from a continuous-wave magnetron in a low-cost and highly efficient way. The remote-control communication signal of an unmanned aerial vehicle (UAV) is successfully jammed by a magnetron jamming transmitter working around 5.8 GHz. The UAV uses the frequency-hopping binary phase shift keying (FH-BPSK) technique for communication. The magnetron jamming transmitter can adjust its output power and spectrum (which have a strong relation to the jamming results) by changing its anode current. The calculation of the bit error ratio (BER) of FH-BPSK communication under the jamming signal from the magnetron is derived theoretically. Then, the variation of BER under different anode currents of the magnetron and different distances between the UAV and its remote controller are analyzed. The comparison of experimental results and theoretical analysis show that the UAV is successfully jammed when the BER is higher than 6%. Because the distance between the UAV and its remote controller is fixed at 26 m, jamming succeeds when the anode current of the magnetron is between 70 and 120 mA. If the anode current of the magnetron is fixed, jamming could also succeed with a greater distance between the UAV and its remote controller. [ABSTRACT FROM AUTHOR]

A microwave power combining system based on four 20-kW hybrid injection-locked magnetrons in the S-band was proposed and presented. A high-power-capacity power combiner was designed, and the behaviors of the hybrid injection-locking magnetrons were qualitatively explained. An excellent output amplitude stability of 0.01 dB (peak-to-peak), a phase stability of ±0.9° (peak-to-peak), and a spur suppression ratio of −65.0 dBc at 500 kHz were achieved when the injection ratio was 0.07. The proposed four-way 20-kW magnetron coherent power combining system exhibits a total output power of over 60.6 kW and a combining efficiency of 91.5%. Simultaneously, neither real-time automatic phase tuning processes nor high-isolation circulators are required in the system. The results show that a high-efficiency magnetron power combining system has the potential to be applied as a cost-effective high-power microwave source for industrial applications. To the best of the authors’ knowledge, a microwave power combining system featuring four 20-kW S-band continuous wave magnetrons has been successfully testified for the first time. The power output of over 60.0 kW and combining efficiency of 91.5% set a new performance record for S-band magnetron power combining systems and represent the best phase noise performance reported for any injection-locked magnetron with an output power of over 15 kW. [ABSTRACT FROM AUTHOR]

A real-time phase-shifterless power controlled combining based on 20-kW S-band continuous-wave magnetrons with an asymmetric injection was proposed in this letter. A high-power-capacity combiner was designed, and the behaviors of the asymmetric injection magnetrons were qualitatively characterized. The system showed a nearly 3-MHz injection-locked bandwidth and an output power control range over 3 dB at an injection ratio of 0.07. An excellent spur suppression ratio of −65.0 dBc at 500 kHz, an output amplitude stability of 0.02 dB (peak to peak), and a phase stability of ±0.9° (peak to peak) were also demonstrated. To the best of our knowledge, the power output of 34.0 kW with a total combining efficiency of 86.7% sets a new performance record for an S-band continuous wave magnetron power combining system, which is one of the best spur suppressions among all reported S-band injection locked magnetrons with an output power of over 15 kW. [ABSTRACT FROM AUTHOR]

This paper proposes an S-band microwave transmitting system based on four-way master–slave injection-locked magnetrons, which has the advantages of low cost and high efficiency. The transmitting system consists of a microwave generator and an antenna array. The microwave generator provides four-way excitations with equal phases and amplitudes to the antenna array, where a radial divider is applied to produce and control the four-way injected signals to lock the slave magnetrons. The antenna array includes four pyramid horns and two layers of artificial materials with 2-D periodic corner-truncated square slots, which are arranged to enhance the gain and suppress sidelobes. The transmitting system is fabricated and measured. Experimental results show that the microwave generator is able to produce four-way excitations with the phase differences less than 12° and the amplitude errors less than 3%. The antenna array provides a gain of 27.2 dB, sidelobe levels less than −10 dB, and reflection coefficients less than −15 dB. The whole system operates stably at 2.46 GHz with a transmitting power of 3.5 kW. [ABSTRACT FROM PUBLISHER]

A high power gain magnetron amplifier with output phase control based on load–pull characterization has been developed. The equivalent resonant cavity method was first introduced to facilitate the proposed magnetron amplifier system as a basic injection model, and the system behavior was qualitatively evaluated based on Alder’s equation. It is the first time that a magnetron has been locked at a 58-dB gain. The magnetron amplifier shows an enhanced power-added efficiency of 72.0%, wide output phase control range, and 18.5-MHz bandwidth at a ratio of the output to the input power of 45 dB. This is the first time a successful magnetron output phase control based on load–pull at a power gain of 45 dB has been demonstrated. The magnetron output spectra were fully synchronized with a reference signal and the phase noise of the magnetron amplifier reached −106.3 dBc/Hz at an offset of 1 kHz. An output amplitude stability of 0.01 dB (peak to peak), a phase stability of 0.5° (peak to peak), and a high-efficiency dual 1-kW magnetron amplifier coherent-power combination based on the load–pull characterization was achieved. To the best of the authors’ knowledge, this is one of the highest power gains and phase noise performances ever reported for an S-band injection-locked magnetron with a power output of over 1 kW. [ABSTRACT FROM AUTHOR]

Currently, microwave energy is utilized for many diverse industrial applications because of its various advantages including its eco-friendliness. Low-cost, high-efficiency, and high-power industrial microwave sources are in urgent demand. In this paper, we propose a low-cost quasi-coherent power-combining system based on a combination of two magnetrons. We have analyzed and built a low-loss waveguide-based applicator combined with specific phase. This system utilizes the coupling of the combiner to quasi-lock the slave magnetron. A waveguide phase shifter lies in the slave magnetron branch to adjust the phase difference between the master and slave magnetrons’ signals to achieve high resultant efficiency. Based on theory, the phase difference between the master and the injected slave magnetrons has been numerically calculated and analyzed. The phase difference changes periodically when the slave magnetron is quasi-locked to the master magnetron and the periodicity increases with the injection ratio. Experimental results show the resultant efficiency of the proposed system can reach as high as 92% when using several suitable waveguide components. The investigation also provides guidelines for further microwave power combination systems with multiple sources. [ABSTRACT FROM PUBLISHER]

A 3-D particle-in-cell simulation model of a commercial industrial heating magnetron is developed as a guide for improving a fixed-output-power magnetron. After this improvement, the magnetron is transformed into a 20-kW power-adjustable phase-locked magnetron, which can then be injection-locked with tunable power output. For the first-time ever, the output power of the injection-locked magnetron is continuously tuned from 2 to 19 kW. This large-power magnetron is both phase and amplitude controlled, and is useful for the coherent power combining of multiple magnetrons. The magnetron frequency pushing effect, which affects the injection-locked frequency range of the phase-locked magnetron, is observed in both simulations and measurements. In the injection-locking experiments, the locking bandwidth varies from 11.7 to 2.4 MHz when the output power is tuned from 5 to 19.1 kW and the injection power is kept at 120 W. Moreover, the center frequency of the phase-locked magnetron increases with increasing output power. [ABSTRACT FROM AUTHOR]

Microwave power combining based on dual 15-kW continuous-wave (CW) magnetrons in S-band is presented. The injection locking on 15-kW CW magnetrons has been successfully accomplished. The phase-locking bandwidth of each magnetron reaches 5 MHz with an improved dc power supply. Meanwhile, phase jitters are measured and analyzed briefly. The injection-locked 15-kW magnetrons have stable magnitude and tunable locked phase, which are suitable for coherent power combining. A dual-magnetron microwave power combining system has been designed and developed with an automatic phase controlling mechanism. The microwave power combining efficiency is higher than 95%. It is the first time to demonstrate a successful microwave power combining of dual 15-kW S-band CW magnetrons. The system will find industrial applications in producing diamond film from microwave plasma chemical vapor deposition. Large-power and high-efficiency microwave sources based on power combining from magnetrons are good candidates for industrial applications. [ABSTRACT FROM PUBLISHER]

A multi-magnetron microwave source, a metamaterial transmitting antenna, and a large power rectenna array are presented to build a near-field 2.45 GHz microwave power transmission system. The square 1 m2rectenna array consists of sixteen rectennas with 2048 Schottky diodes for large power microwave rectifying. It receives microwave power and converts them into DC power. The design, structure, and measured performance of a unit rectenna as well as the entail rectenna array are presented in detail. The multi-magnetron microwave power source switches between half and full output power levels, i.e. the half-wave and full-wave modes. The transmission antenna is formed by a double-layer metallic hole array, which is applied to combine the output power of each magnetron. The rectenna array DC output power reaches 67.3 W on a 1.2 Ω DC load at a distance of 5.5 m from the transmission antenna. DC output power is affected by the distance, DC load, and the mode of microwave power source. It shows that conventional low power Schottky diodes can be applied to a microwave power transmission system with simple magnetrons to realise large power microwave rectifying. [ABSTRACT FROM AUTHOR]

Phase-control precision is important for applications of magnetrons in the microwave source array. Here, experimental results use a 20-kW $S$ -band continuous-wave magnetron to investigate the phase deviation of large-power phase-locked magnetrons. For the first time, the phase deviation of a 20-kW magnetron controlled through an externally injected signal was studied. The phase deviation of the injection-locked magnetron output worsened gradually, the greater the difference in frequency of the injected signal (with the same injection ratio) from the center of magnetron injection-locked bandwidth was. When the injected power was maintained at 150 W and the magnetron output was at 19 kW, the maximum phase deviation was varied from approximately 1° to 6° with frequency tuning. In addition, the phase deviation of the phase-locked magnetron decreased as the injected signal power increased at a given frequency. [ABSTRACT FROM AUTHOR]

Conventional microwave heating has serious problems such as non-uniform heating and low efficiency. A novel magnetron microwave sweep frequency heating method is proposed to improve microwave heating uniformity. In this method, the frequency-sweeping signal is injected into the magnetron by the injection frequency-locking technique, and the microwave sweep frequency heating of the magnetron is realized. In this paper, a complicated injection frequency locking system is given and analyzed and a multiphysics calculation model based on the finite element method for electromagnetic waves and heat transfer is established. The calculation of microwave sweep frequency heating is realized by the combination of COMSOL and MATLAB. The results show that the sweep frequency heating has an obvious superiority. An experiment is carried out to verify the simulation results. The simulation results are in agreement with the experimental data. Moreover, the effect of sweep bandwidth and sweep interval on heating uniformity is discussed. [ABSTRACT FROM AUTHOR]