Showing papers on "Extremely high frequency published in 1990"

Monolithic millimeter-wave two-dimensional horn imaging arrays

Abstract: A monolithic two-dimensional horn imaging array has been fabricated for millimeter wavelengths. In this configuration, a dipole is suspended in an etched pyramidal cavity on a 1- mu m silicon-oxynitride membrane. This approach leaves room for low-frequency connections and processing electronics. The theoretical pattern is calculated by approximating the horn structure by a cascade of rectangular-waveguide sections. The boundary conditions are matched at each of the waveguide sections and at the aperture of the horn. Patterns at 93 and 242 GHz agree well with theory. Horn aperture efficiencies of 44+or-4%, including mismatch and resistive losses, have been measured. A detailed breakdown of the losses is presented. The coupling efficiency to various f-number imaging systems is investigated, and a coupling efficiency of 24% for an f0.7 imaging system (including spillover, taper, mismatch and resistive losses) has been measured. Possible application areas include imaging arrays for remote sensing, plasma diagnostics, radiometry and superconducting tunnel-junction receivers for radio astronomy. >

Narrow-band modulation of semiconductor lasers at millimeter wave frequencies (>100 GHz) by mode locking

Abstract: The possibility of mode locking a semiconductor laser at millimeter wave frequencies approaching and beyond 100 GHz was investigated theoretically and experimentally. It is found that there are no fundamental theoretical limitations in mode locking at frequencies below 100 GHz. At these high frequencies, only a few modes are locked and the output usually takes the form of a deep sinusoidal modulation which is synchronized in phase with the externally applied modulation at the intermodal heat frequency. This can be regarded for practical purposes as a highly efficient means of directly modulating an optical carrier over a narrow band at millimeter wave frequencies. Both active and passive mode locking are theoretically possible. >

A wide-band millimeter-wave gyrotron traveling-wave amplifier experiment

Abstract: A saturated instantaneous bandwidth (FWHM) of at least 10% in a Ka-band gyrotron traveling-wave tube (gyro-TWT) with uniform interaction waveguide and magnetic field was obtained. A relatively low alpha ( identical to nu /sub perpendicular to // nu /sub ///) beam has resulted in stable saturated operation and broad bandwidth. This, together with the overall performance of the tube (18.4-kW maximum power at 18.6% efficiency and 18-dB gain), strongly reinforces the possibility of developing a new generation of millimeter traveling-wave amplifiers based on the gyro-TWT. >

Microwave oscillator with reduced phase noise

Abstract: An oscillator operational in the millimeter wave and microwave range, including frequencies greater than 60 GHz, is provided with reduced phase noise by enhancing Q of the resonant circuitry by reactively terminating fundamental frequency oscillation and increasing stored fundamental frequency energy in the resonant circuitry. A two frequency system is provided with constructive reflection of energy at fundamental frequency back to the resonant circuitry, and with isolation of fundamental frequency energy from the output load. Energy to the output load is obtained from the in-situ generated second harmonic of the active element. Phase noise is reduced by enhancing Q by more than an order of magnitude.

Operation of a large-orbit high-harmonic gyro-traveling-wave tube amplifier

Abstract: The high-harmonics gyro-traveling-wave tube (gyro-TWT) is a high-power (>or=1-kW) millimeter wave amplifier based on the synchronous interaction of a beam of large-orbit axis-encircling electrons with a high-order cylindrical waveguide mode. Since the interaction occurs at a high harmonic of the cyclotron frequency, the intense magnetic fields required for the conventional fundamental-mode gyro-TWT are not required. A proof-of-principle experiment designed to demonstrate the interaction of a 150-mA, 350-keV electron beam with the TE/sub 81/ mode of a cylindrical waveguide is described. Principal results include a small signal gain of 10 dB, an interaction bandwidth of 4.3%, and a saturated power transfer from electron beam to wave of 0.5 kW. Additional measurements include the dependence of gain on electron beam current and the measurement of the beam's gamma , beta /sub 4/F, beta /sub ///, and Delta beta /sub ///. Sufficient agreement between the experimental results, the simulation codes, and an analytic description of the interaction is demonstrated to permit the design of high-performance millimeter wave amplifiers. >

Millimeter-wave generation and characterization of a GaAs FET by optical mixing

Abstract: Coherent mixing of optical radiation from a tunable continuous-wave dye laser and a stabilized He-Ne laser was used to generate millimeter-wave signals in GaAs FETs attached to printed-circuit millimeter-wave antennas. The generated signal was further down-converted to a 2-GHz IF by an antenna-coupled millimeter-wave local oscillator at 62 GHz. Detailed characterizations of power and S/N under different bias conditions have been performed. This technique is expected to allow signal generation and frequency-response evaluation of millimeter-wave devices at frequencies as high as 100 GHz. >

Millimeter-Wave Frequency Tripling in Bulk Semiconductors

Abstract: The free charge carriers in lightly doped semiconductor crystals exhibit an optical nonlinearity throughout the infrared which strongly increases with wavelength. While at 10 μm wavelength the nonlinear frequency conversion is hardly measurable, we observe strong third harmonic conversion in the submillimeter region at 500 μm. This talk discusses theoretical considerations and preliminary experiments of extending third harmonic conversion into the millimeter wavelength region. It will be pointed out that the mechanism in question is distinct from the long-known nonlinearity which arises when the carrier temperature is periodically modulated by the microwave field, an effect which dies off at higher microwave frequencies. Sizable third harmonic conversion was obtained by shining a 200 kW millimeter-wave beam from a gyrotron at 70 GHz through a lightly doped n-silicon crystal.

Measurement of transmission and reflection of conductive lossy polymers at millimeter-wave frequencies

Abstract: Several conductive polymer samples of various thicknesses were measured at a frequency range of 26.5 to 60 GHz. Samples of conductive polymer were measured for transmission and reflection characteristics using a Hughes millimeter-wave waveguide network. It is shown that thin, lightweight planar samples of a particular conductive polymer significantly reduce reflections while providing a high transmission loss over a broad frequency range. >

Millimeter wave generation and phase control using optical heterodyne techniques and waveguide devices

Abstract: The use of optical techniques for generating microwave signals and controlling microwave devices has several advantages over more conventional approaches, including improved transmission and modulation capabilities.1,2 Previous work has demonstrated microwave signal generation up to 35 GHz by heterodyning the outputs of sideband injection-locked semiconductor lasers.3,4 Radio frequency phase control potentially suitable for phased array antenna applications has also been demonstrated using a He–Ne gas laser and KDP crystal for optical phase shifting.5 That work, however, was limited to a rf of 125 MHz and required 260 V for a π phase shift.

Novel shielding, reflection and scattering control using chiral materials

Abstract: Electromagnetic and optical shields, controllers, and reflectors comprising chiral materials. Electromagnetic and optical controllers and layers provided in accordance with this invention comprise chiral materials wherein reflection, scattering, absorption and shielding properties can be tailored over specified frequency regime. Layered structures have a variety of potential applications in radar cross section management, radar absorbers for low observables and other applications, radomes, antennae, and radio wave, microwave and millimeter wave chambers. Likewise, these structures have many applications to electronic devices, integrated optics, and optical components and systems, as well as in their radio wave, microwave, and millimeter wave counterparts.

Millimeter wave fin-line gas discharge receiver protector

Abstract: A passive, broadband, millimeter wave, fin-line, gas discharge device operable for use in a radar system as a receiver protector. The preferred embodiment of this device comprises: a rectangular waveguide housing having a free electron emitting radioactive primer mounted upon one interior wall, an inert gas under pressure contained within the housing by two thin, low loss dielectric windows at opposing ends of the waveguide housing, and two bevelled, tapered fins operable to provide a narrow discharge gap region. Incident ratio frequency signals entering the radar system pass through the fin-line receiver protector. Signals entering the waveguide housing through the thin dielectric windows excite the free electrons causing the electrons to collide with the inert gas molecules. A spontaneous breakdown of gas occurring in the narrow discharge gap region between the two bevelled, tapered fins greatly attenuates the incident ratio frequency signal from entering the receiver thereby protecting it. Embodiments for board band, narrow band, low power and high power applications are described.

Millimeter wave radar transmitter receiver

Abstract: PURPOSE: To improve an SN ratio as a beam switching type FM-CW radar by switching an intermediate frequency, obtained by mixing a reflected wave and a sent wave with different local oscillation frequencies, in two stages so that data processing for angle and distance arithmetic can be performed. CONSTITUTION: The output of an FM-CW wave source 100 is led to respective transmitting and receiving circuits 50 on a time-division basis and separated to paths for transmission and reception, and they are filtered by BPFs(band-pass filter) 15 and 17 after being multiplied 14 and 16 to become an RF(radio frequency for transmission) signal and an Lo(local oscillation) signal. A reflected signal from a target is passed through a distributor 30 and a circulator 18 and frequency-mixed by a mixer 19 with the Lo signal, thereby obtaining the same 1st intermediate frequency as the frequency of the CW wave source 100. Then a selector 40 selects it on a time-division basis and the selected frequency is mixed by a mixer 41 with a properly selected local oscillation signal 42 to obtain the IF signal of frequency which enables the digital processing for the angle and distance arithmetic, etc. Thus, the SN ratio is increased to improve distance resolution and angle accuracy. COPYRIGHT: (C)1992,JPO&Japio

Millimeter wave power generator

Abstract: A millimeter wave power generator combines two laser beams, tuning the beat frequency to the desired millimeter wave value with an opposing pair of millimeter wave cavities. The combined beam is diffracted onto a plurality of externally powered, modulation doped field effect photodetectors (MDFEPs). A plurality of antennas is provided, one between each pair of adjoining MDFEPs. The antennas are parallel, and each is driven by the MDFEPs at its ends. The back propagating millimeter wave radiation is reflected forward by a wire grid parallel to the antennas. The grid is situated between the diffractor and the MDFEPs, and is spatially tuned to constructively interfere the reflected back propagating with the forward propagating millimeter wave radiation.

Integrated Optics for Microwave and Millimeter Wave Detection and Signal Processing

Abstract: Integrated optical electrooptic modulators can play a crucial role in the sensing, control and processing of microwave and millimeter wave signals of phased array antenna systems. Integrated optical single side band modulators with narrowband resonant microwave electrode structures can serve as ideal microwave/optical transducers for antenna elements. The single side band modulation scheme allows the encoding of the microwave frequency and phase information onto an optical carrier shifted by the microwave frequency. This allows the use of coherent optical techniques for beam steering and signal processing of microwave signals used in phased array antenna systems.

Computer Aided Design Models for Millimeter-Wave Suspended Substrate Microstrip Line

Abstract: : An equivalent circuit model was derived for the series gap discontinuity in shielded suspended-substrate transmission line. Numerical values of the circuit parameters were computed for various sets of line dimensions, over a range of operating frequencies. The shielded suspended- substrate line is a transmission medium useful for radar and microwave circuits in the Ka band frequency range, 30 - 40 GHz. In order to utilize this transmission medium in the construction of microwave circuits and filters, it is necessary to have valid circuit models for typical discontinuous change in width. These discontinuity characteristics may be deduced on the basis of a calculation of their scattering coefficients for propagating waves in the medium. The approach chosen in this thesis, however, is that of placing the selected discontinuity in an open-ended strip resonator in the transmission medium. An appropriate circuit model is adopted for the given discontinuity, and its circuit elements are then deduced on the basis of the perturbation of the resonance frequency of the strip resonator which is induced by the mode. The boundary-value problem associated with the microstrip resonator structure has been approached in a rigorous manner based on a full-wave analysis which utilizes a process of solving the electromagnetic (EM) boundary value problem with inclusion of all the field components.

Regions of single mode operation in high power gyrotron oscillator

Abstract: Stable single mode operation is a very important consideration in the design of high power microwave and millimeter wave sources.

Studies of the pressure-broadened atmospheric oxygen spectrum with an automated millimeter-wave resonance spectrometer

Abstract: Atmospheric O 2 has a host of absorption lines centered around 60 GHz. Spectral attenuation rates a in dB/km are calculated with the millimeter-wave propagation model MPM89.

Millimeter-wave active probe system

Abstract: PURPOSE: To contrive doubling of an input signal in order of 20GHz by disposing a circuit having a nonlinear element for frequency doubling in planar millimeter wave wafer probe structure. CONSTITUTION: An active millimeter wave probe receives an input signal in order of 20GHz with a coaxial connector and obtains in an output node 14 as output of a doubling device of the active probe 5. At first, a test signal of a about 20GHz is applied to the connector. The input signal is given to the input part 30 of a low area filter 88 through a coplanar wave guide path, and only the frequency of the input signal is passed. Output of the filter 88 is given to a diode satisfying a frequency doubling function. A high frequency is generated since a diode pair have a non-linear voltage-current characteristic. Next, an output matching network 84 matches the output impedance of the diode pair 34. Next, a band filter 86 transmits a fifth harmonics to an output part 14, thereby attenuating and reflecting the signal of the frequency out of a band.

Millimeter wave communication system

Abstract: PURPOSE:To attain the reception of always the same level at a reception side by using a millimeter wave, utilizing the characteristic of the millimeter wave in which the propagation loss depends on the frequency and varying the frequency while making the transmission power of the transmission side constant against a change in a propagation distance. CONSTITUTION:A radio wave sent from a transmission side 5 is received with attenuation at a receiver side 6. A millimeter wave is adopted for the operating radio wave and since the propagation loss depends on the frequency, the power amplification level at the transmission side 5 is made constant by adjusting the frequency (a frequency region of attenuation region 21 is in use), and even if the receiver side 6 is moved and the propagation distance is changed, the frequency is changed for the adjustment so that the demodulation is applied at an optimum level at the receiver side 6. Moreover, since the attenuation is controlled by the frequency, the frequency of a near distance differs from that of a long distance, and the frequency division multiplex is utilized to reduce any interference.

Extremely high frequency oscillator.

Abstract: In a peniotron, hollow electron beam (e) is generated from a cathode gun assembly (11) and a DC magnetic field is applied to the electron beam (e) from solenoid coils (18, 19, 20) Thus, each electron of the electron beam (e) is gyrated into a resonant cavity and propagating waveguide sections (13, 14) which are maintained in a auto-resonant conditions so that the electrons interact with an electromagnetic waves of TE mode not only in the resonant cavity section(13) but also in a waveguide section (14) Accordingly, the electromagnetic wave is oscillated in the resonant waveguide section (13) and amplified in the propagating waveguide section (14) such a manner that the level of the electromagnetic wave in the resonant cavity section (13) is far less than that output power from said propagating waveguide (14)

Use Of Picosecond Optical Pulses And FETs Integrated With Printed Circuit Antennas To Generate Millimeter Waves

Abstract: Millimeter wave radiation has been generated from FET's and HEMT's, integrated with printed circuit antennas, and illuminated with picosecond optical pulses. Modulation of the millimeter waves was achieved by applying a swept RF signal to the transistor gate. Using this technique, tunable electrical sidebands were added to the optically generated carrier providing a method of transmitting information and doing high resolution spectroscopy. Heterodyne detection demonstrated that the system continuously generated tunable radiation, constrained by the high gain antenna, from 45 to 75 GHz. ECENT experiments have shown that optoelectronic

Hybrid mode analysis of rf characteristics in semiconductors

Abstract: The method of lines has been applied to study the RF/microwave characteristics of 111-V semiconductor traveling wave electrooptic modulators. Double-rib, multilayer strip wave-guides have been investigated. It is found that Schottky barrier junction controlled structures support multi-nondispersive modes having phase velocities that closely match the optical carrier. These modes are potentially useful in ultra-fast modulators operating into the millimeter wave band.

Recent developments of microwave/millimeter-wave integrated active antenna elements

Abstract: Recent developments in solid-state devices and microwave integrated circuits have made it possible to integrate the active devices with planar antennas to form active antennas. This paper presents the recent technology advances at Texas A&M University in active antenna elements using patch, notch and circular ring antennas integrated with Gunn or FET devices.

The main results of cloud and rain remote sensing by multichannel microwave radiometry

Abstract: The basic results have been considered for multiwave remote sounding of the troposphere with clouds and rain from ground-based station in the zenith direction. The radio wave scattering by rain drops as well as variation of vapour content in the atmosphere during measurements are taken into account when processing of the experimental data. A separation of the complete attenuation in clouds with rain has been made over three components: due to vapour, cloud and rain. A relation is considered of millimeter and centimeter wave attenuation in clouds with rain between each other and with the rain intensity. A behaviour of the relation of attenuation structural functions is explained. The Diagnostic problems of millimeter wave attenuation are considered.

Recent Developments in Superconducting Receivers

Abstract: A description is given of recent work at Berkeley on superconducting mixers and detectors for infrared and millimeter wavelengths. The first report is a review article which summarizes the status of development of superconducting components for infrared and millimeter wave receivers. The next report describes accurate measurements and also theoretical modeling of an SIS quasiparticle waveguide mixer for W-band which uses very high quality Ta junctions. The best mixer noise is only 1.3 times the quantum limit. Both the mixer gain and the noise are in quantitative agreement with the quantum theory. Next, a report is given on measurements and theoretical modeling of the absorptivity (surface resistance) of high quality epitaxial films of the high {Tc} superconductor YBCO from 750 GHz to 21 THz. Finally, there are reports on the design and experimental performance of two different types of high {Tc} bolometric detectors. One is a conventional bolometer with a gold-black absorber. The other is an antenna coupled microbolometer.