Injection locked multi-section gain-coupled dual mode DFB laser for terahertz generation

A dual mode multi-section gain-coupled distributed feedback laser with tunable mode spacing is subharmonically injection locked at 0.315 THz. The injected signal consists of an optical comb with harmonics 35 GHz apart and a bandwidth of approximately 1.9 THz. The optical comb is a result of strong four-wave mixing in a highly-nonlinear dispersion-shifted fiber. In order to observe locking of the multi-section laser, the output is optically downconverted to RF frequencies using the same optical comb. The locked multi-section DFB laser is a coherent and tunable optical source suitable for continuous-wave terahertz generation systems.     

Operation Features of a Locked Gunn-Diode Microwave Oscillator due to Sign Reversal of the Nonlinear Reactance of the Diode

It is shown experimentally that the nonlinear reactance of a Gunn diode can reverse sign depending on the operation mode of the diode with respect to the direct current. We propose a method for determination of the factor describing the diode-reactance nonlinearity in the case of a locked Gunn-diode oscillator.     

Experimental investigation of millimeter wave Gunn oscillator circuits in circular waveguides

Millimeter wave Gunn oscillator circuits using circular waveguides for 33–50 GHz and 75–110 GHz frequency bands are described. These oscillators are simpler to construct at millimeter wavelengths compared to the conventional rectangular waveguide circuits. The effect of various circuit parameters on the oscillator frequency and output power has been experimentally studied. The CW power and mechanical tuning range obtained from the circular waveguide Gunn oscillators are found to be comparable and sometimes even better than those obtained with conventional rectangular waveguide circuits using the same Gunn device.     

One-Circuit Stabilization of Millimeter-Wave Solid-State Oscillator by Quasi-Optical Resonator

The construction and operating characteristics of the highly stabilized millimeter wave IMPATT oscillator are described. The frequency stability is 8.1 × 10^-7 at 115 GHz. The output power is no less than 15 mW. The sphere-corner-echelette open resonator have been used for oscillator stabilization. This approach is also adaptable to the Gunn oscillator.     

Frequency Sources in W-band Radar Front-end with Low Phase Noise

A W-band coherent stepped-frequency pulsed radar front-end is developed. It consists of a millimetre wave transmitting source, a mm-wave local source, a DDS with multi frequency points output and two microwave sources serving as local oscillators. All the sources are coherent with the 120 MHz referenced crystal oscillator. The mm-wave sources are realized by frequency multiplier chain, up-conversion and injection locking. The phase noise of fundamental-wave injection-locked W-band harmonic Gunn oscillator output signal achieves −98 dBc/Hz at 10 kHz offset and the spurious output is less than −50 dBc. The received intermediate frequency signal is also presented.     

Millimeter wave pulsed gunn oscillator for low chirp radar application at W-Band

Pulsed Gunn oscillator at 94 GHz has been developed using GaAs CW Gunn diode, by choosing a proper operating point and resonant circuit. Peak power output of 25 mw at 94 GHz with a pulse width of 2 microseconds and duty factor of 2% is achieved. Bias circuit oscillations are suppressed by rising the operating voltage alongwith other circuit considerations.     

A W-band Frequency Source with Low Spurs and Low Phase Noise

A W-band millimeter wave frequency source is developed by frequency multiplier chain and injection locking. The referenced crystal oscillator (CO) signal 120 MHz is multiplied 400 times to output 48 GHz signal. Then, it is used as a referenced source of fundamental-wave injection-locked harmonic Gunn oscillator with output power more than 10 mW at 96 GHz and spurious output less than −65 dBc. The measured phase noise is −97 and −105 dBc/Hz at 10 kHz and 200 kHz offset, respectively. At last, the influence of the flicker noise, provided by the frequency multipliers and amplifiers, is analyzed.     

35 GHz dielectric resonator stabilised gunn oscillator

A 35 GHz dielectric resonator oscillator(DRO) using GaAs Gunn diode in microstrip configuration has been designed and developed. The oscillator, with an integral waveguide-to-microstrip transition, delivered an output greater than 18 dBm. Phase noise of the oscillator is found to be better than –80 dBc/Hz at 100 KHz away from the carrier. A frequency drift of about ±25 MHz has been observed over the temperature range from –10 °C to 50 °C.     

Q-band injection-locked gunn diode oscillator

The configuration and performance of a Q-band injection-locked Gunn oscillator are presented whose outport is connected with a phase-locked reference source by a circulator. The output power of the oscillator is more than 60mW at 46.1GHz. The single-sideband phase noise (SSB) is less than-71.7dBc/Hz offset 10KHz from the carrier, and the spectrum of clutter signal is less than -40dB.     

Thermistor controlled gunn oscillator at Ka-band

Frequency drift of Gunn oscillators is a major cause of concern in most of the Millimeter wave communication systems. This paper describes a simple and cost effective technique to arrest the frequency drift of a Ka band Gunn oscillator within 15 MHz for the operating temperature range of 0°C to 60°C as against a typical drift of about 50 to 100 MHz for free running Gunn oscillator for the same temperature range. At the ambient, the oscillator remains within ±1 MHz from switching on to stabilization. The temperature variation is sensed with a small thermistor bead placed close to the diode and a correction voltage is applied to the bias to compensate for the frequency drift. This compensation circuit also takes into account the non-linear behaviour of the thermistor and the Gunn oscillator with the temperature.     

The parameter analysis of the large signal mathematical model of Gunn devices operating in the harmonic mode

This paper analyses in detail the parameters of the large signal mathematical model of a Gunn device operating in the harmonic mode using the frequency-domain harmonic balance method and indicates the variation trend of the output power and the operating frequency of a harmonic oscillator under the influence of the model parameters of the device. The analysis results offer the theoretical basis for the production of Gunn devices and for the design of harmonic oscillators     

Varactor Controlled Gunn Oscillator at W-Band

This paper describes the experimental circuit and measured performance of varactor tuned Gunn oscillator at W-band. The power output of 12.5 dBm has been achieved when packaged GaAs Gunn diode is used. Linear frequency excursion of 150 MHz with power variation of 1 dB has been observed when varactor was given reverse bias from 0 to 20 volts. GaAs hyperabrupt varactor is used in parallel to gunn diode at a distance of odd multiple of g/2 in waveguide channel.     

Hot electron injector Gunn diode for advanced driver assistance systems

This paper reviews the main aspects of the design, fabrication and characterization of GaAs Gunn diodes intended to be used in advanced driver assistance systems. The corresponding Gunn diode based oscillators operate at the microwave frequency of 77 GHz and deliver an output power up to 19.2 dBm (83.2 mW). To fulfill the high demands of the automotive industry, temperature stability and a high grade of frequency purity, the Gunn diode structure includes a hot electron injector. This is based on the heteroepitaxy of a graded gap Al_xGa_1-xAs layer and an adjacent thin highly doped GaAs layer. The hot electron injector properties are investigated using dc and rf electrical measurements, including the temperature influence as well. Specific production related data of the cavity oscillators using our Gunn diodes are presented. New alternatives, such as the resonant tunneling emitter as a hot electron injector and the Gunn diode based MMIC as oscillator, are introduced. PACS 85.30.-z; 73.40.-c; 07.57.Hm; 84.30.Ng; 85.30.Fg     

高性能注入锁相光电振荡器

提出一种基于注入锁定和锁相环技术的注入锁相光电振荡器.利用注入锁定来改善光电振荡器的近载频相噪以及杂散抑制度.将光电振荡器的输出信号与外注入源进行鉴相,通过锁相环来提升频率稳定性,并进一步改善光电振荡器的近载频相噪.实验结果表明:注入锁相光电振荡器在电滤波器中心频率为9.5GHz、3dB带宽为20 MHz和光纤环长度为6km的情况下,实现了输出信号频率为9.5GHz的单模振荡;当注入锁定带宽为1.98kHz时,光电振荡器输出信号在1kHz频偏处的相位噪声为-125dBc/Hz,在10kHz频偏处的相位噪声为-147dBc/Hz,杂散抑制度高于80dB,阿伦偏差接近1.37×10~(-11)@1s和1.22×10~(-11)@1000s.     

Equilibrium and stability of free-running, phase-locked, andmode-locked quasi-optical gyrotrons

Equilibria and stability (both single-mode and sideband) are calculated and contrasted for free-running, phase-locked, and mode-locked oscillator configurations in a quasi-optical gyrotron. The oscillator can be phase locked by direct injection of radiation into the oscillator cavity. The equilibrium and stability properties are not greatly affected at low injection power levels. Alternatively, the oscillator could be phase locked by prebunching the beam. If the beam is prebunched, there are dramatic effects on both equilibrium and stability. The transverse efficiency can be considerably enhanced by prebunching the beam. This prebunching can be done on either a phase-locked (using an external RF source) or mode-locked (using the oscillator output) configuration. The stable locking bandwidth turns out to be about half the ω/Q linewidth of the mode     

Investigations on optically controlled millimeter wave Gunn oscillators

There is a growing interest in optically controlled millimeter wave oscillators. In this paper, we have investigated the external-circuit impedances of an optically controlled millimeter wave subharmonic Gunn diode oscillator, which is illuminated by GaAs/GaAlAs laser beam. The variation of the external-circuit impedances looking outward from the Gunn diode with respect to the optical injection plasma density are calculated based on a field analysis method. The results give some useful conclusions for optically controlled millimeter wave Gunn diode oscillator design. Experimentally an optical tuning frequency shift of 7MHz is achieved at W-band.     

D-band operation of a second harmonic GaAs gunn oscillator

A GaAs second harmonic Gunn oscillator for D-band applications is proposed. The doping structure of the active device has been optimized using Monte-Carlo and hydrodynamic models. The load impedance characteristic of a resonant mounting structure in a WR06 waveguide has been consistently taken into account. At sufficiently low load resistances and reactances, output powers of the order of 20–50 mW should be obtainable around 140 GHz under realistic thermal conditions.     

Gunn oscillator injection locking circuit at millimeter wave frequencies

Millimeter wave frequencies are proposed as carriers of microcell future mobile systems. High frequencies in the region of 60–62 Ghz are suggested. A serious difficulty in this context is the lack of sufficient gain in active devices. Both on receiver and transmitter units this difficulty is faced. Mixing, amplification, carrier recovery and modulation / demodulation subsytems are required to be operational at these higher frequencies. Presently the MMIC 's show also limited performance. In this report an alternative approach active processing technique is examined based on an injection locking in Gunn oscillator. A non-linear analysis is applied to determine the fundamental properties of injection locking in Gunn oscillator performance under the influence of an external signal. Details of waveguide action is taken into account by solving the corresponding boundary condition problem. Finally experimental results are presented for a 30GHz oscillator.     

A novel millimeter wave gunn oscillator

It is described that the design, configuration and the performance of a novel millimeter wave Gunn oscillator stabilized by external cavity and temperature compensation in this paper. The frequency stability is 3.6 × 10⁻⁶ at 52 GHz over the teperature range from −10 to 50 °C. An output power of more than 100mW has been obtained in the frequency range from 51.5 to 52.8 GHz. This research work was supported by National Natural science Foundation and Electronic Industry Ministry of P. R. China.     

Coherent combination of high-power, zigzag slab lasers

We demonstrate a scalable architecture for a high-power, high-brightness, solid-state laser based on coherent combinations of master oscillator power amplifier chains. A common master oscillator injects a sequence of multikilowatt Nd:YAG zigzag slab amplifiers. Adaptive optics correct the wavefront of each amplified beamlet. The beamlets are tiled side by side and actively phase locked to form a single output beam. The laser produces 19 kW with beam quality <2x diffraction limited. To the best of our knowledge, this is the brightest cw solid-state laser demonstrated to date.