A Systematic Investigation on Leaky Characteristics for NRD Guide with Arbitrary Profile of Cross-Section

The leaky characteristics of the NRD guide with arbitarary profile of cross section are systematically studied by a method which combines staircase approximation with multimode network theory and mode-matching procedure. Emphasis is laid on the investigation of the effect of the different profile dimensions on the leakage characteristics of the NRD guide. Extensive numerical results are given to establish useful guidelines for the design of some new types of NRD guide leaky wave antennas.     

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.     

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.     

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.     

W-band gunn second subharmonically locked oscillator

In this paper, the averaging method is used to analyse the performance of second subharmonically injection locked Gunn oscillator. Some useful expressions such as the locking range, output response, output impedance of nonlinear device in fundamental and subharmonic frequency are obtained. a W — band subharmonically locked Gunn oscillator is developed and experimental result demonstrates the validity of this analysis.     

Analysis of Transmission Characteristics for NRD/Microstrip Line Hybrid Integrated LSE and LSM-Mode Baluns*

The NRD/microstrip line hybrid integration structure shows good behavior for millimeter wave applications. This paper applies the integral equations method to analyze the transmission characteristics of the NRD/microstrip line hybrid integrated baluns coupling through slot and operating in LSE or LSM modes. To apply this method, a new Greens’ function of microstrip line is presented and the slot coupling problems between NRD guide and microstrip line and the practical LSE and LSM-mode baluns are analyzed respectively. The availability of the present approach is validated by rather good agreement between the theoretical results and the experiment data given in the literature.* Supported by the National Natural Science Foundation of China (No. 60371010) (No. 60471037)     

Steady-State Responses of NRD-Guide LSE/LSM Mode Oscillators in MM-Wave Bands

The analysis methods for the steady-state responses of the mm-wave band NRD-guide negative impedance oscillators based on nonlinear microwave autonomous circuits harmonic balanced method are presented in the paper in details. Firstly, the large-signal nonlinear lumped equivalent circuits of the Gunn diode are studied in mm-wave bands. Then, the performances of two kinds of NRD-guide autonomous circuits, the probe-exciting LSM ₁₁ ^o-mode oscillator and the LSE ₁₁ ^o-mode oscillator, are analyzed by the way of extracting the large-signal dynamic harmonic admittance (conductance) of the Gunn diode or directly configuring the harmonic balance equations for the oscillator. The input impedance of the exciting probe in the oscillator and the performances of the load-pulling and the local stability of the NRD-guide oscillator are also involved.     

Analysis on suitability of pure and α-Histidine doped KDP crystals in high speed applications

Ferroelectric Potassium Dihydrogen Phosphate (KDP) crystals are widely used in modern short wavelength laser techniques, non-linear and integrated optics. The pure and α-Histidine doped KDP crystals were procured from SRM Institute of Science and Technology, Chennai. The presence of additive in the doped KDP crystal is confirmed through X-Ray diffraction patterns and the lattice parameters were evaluated. Also, Fourier Transform Infrared spectrum confirms the presence of α-Histidine in the doped crystals. The dielectric behaviour of the pure and doped crystals have been studied in the microwave region using K-band microwave bench equipped with the Gunn oscillator and guided with rectangular wave guide.     

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.     

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.     

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     

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.     

Phaselock system for millimeter-wave Gunn oscillators used in radio astronomy and laboratory spectroscopy

A frequency-agile heterodyne phaselock loop (PLL) system for millimeter-wave Gunn-effect oscillators between 40 and 110 GHz is described. The Gunn oscillators are phase-locked via the bias in an active second-order servo loop. A facility for fast frequency switching with a maximum rate of 10 kHz and a frequency separation up to 80 MHz is provided. Measurements on the spectral characteristics of a phase-locked Gunn oscillator are presented. The described PLL system is used in radio astronomy and laboratory molecular spectroscopy.     

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.     

Coupling and quality factors in parallelepiped nonradiative dielectric resonators

In this work, the quality factors and the coupling effects have been investigated for parallelepiped dielectric resonators in nonradiative dielectric (NRD) waveguide, in order to achieve fundamental information for the design of various types of advanced filters. The unloaded quality factor has been calculated taking into account both conductor and dielectric losses through a straightforward version of the perturbation method. The electromagnetic coupling as a function of the distance between NRD guide and resonators has been evaluated through proper extensions of typical lumped equivalent circuits, thus quantifying resonance frequency shifts, external and loaded quality factors, etc.. To validate the derived theoretical models, suitable measurements of all these parameters have been performed at microwaves on X-band NRD prototypes.     

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     

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.     

Microwave Invasion Through Anti-Reflecting Layers of Dielectrics at a Millimeter Wave Irradiation to Living Bodies

Microwave invasion into living bodies through a millimeter wave catheter irradiation is described. As radiation sources for millimeter wave irradiation tests both Impatt oscillator (IO) and a Gunn oscillator were used. Irradiated samples are cow livers and living rats. A newly designed wave-guide vent antenna (WVA) with an anti-reflecting layer (ARL) is used as a launcher for the irradiation and the reflectance measurements. The correlation between the denaturation of the tissue and the reflectance from the WVA is studied in detail.     

Low-frequency noise of Gunn-oscillator first and second harmonics

The low-frequency modulation noise of a Gunn oscillator is analyzed assuming that the diode ac voltage contains the first and second harmonics. The requirements for stable operation with allowance for the mutual effect of the harmonics are examined. It is shown that the procedure for determination of external Q according to frequency pulling is not applicable to such an oscillator. The fluctuational characteristics of a Gunn oscillator with outputs at the first and second harmonics are investigated experimentally. The experimental data are in qualitative agreement with the analysis results.Presented at All-Union Coordinating Conference Low-Frequency Noise in Semiconductor Devices (Chernogolovka, Moscow Region, June, 1991).St. Petersburg State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 2, pp. 226–241, February, 1994.     

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.