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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Effect of Parasitic Dielectric Resonators on CPW/Aperture-Coupled Dielectric Resonator Antennas

The effects of parasitic dielectric resonators on the HE (sub 11 sigma) and HE (High Efficiency) (sub 13 sigma) modes of a cylindrical dielectric resonator antenna (DRA) have been studied. The DRA was excited electromagnetically with a grounded coplanar waveguide through an aperture in the common ground plane. Strong couplings were observed for the HE (sub 11 sigma) mode with the parasitic element superimposed on the driven DRA, and for the HE (sub 13 sigma) mode with parasitic elements placed on both sides of the driven DRA. Results indicate significant enhancement in bandwidth for both modes, and good radiation patterns for the HE (sub 11 sigma) mode.

Simons, R. N.↗
NASA NTRS1985

Microstrip termination effects on dielectric resonator filters

Dielectric resonator filters coupled to microstrip lines appear to answer the requirements of high performance and small size and weight that must be satisfied for use in satellite-based radiometers. The open-circuit and short-circuit types of coupling dielectric resonators to microstrip lines were compared with respect to radiation losses at various frequencies. The filters were fabricated from 1.6 mm Duroid board. The termination impedances for the microstrip lines were measured using a calibrated HP 8510 network analyzer. The values for radiation resistance obtained experimentally for both types of coupling agreed well with the values calculated from the Lewin theory (1960). It was found that the use of short-circuit coupling results in significantly reduced radiation resistance compared to the use of open-circuit lines. Improvement increases with increased frequency.

Trew, R. J.↗
NASA NTRS2006

Multichannel X-Band Dielectric-Resonator Oscillator

A multichannel dielectric-resonator oscillator (DRO), built as a prototype of a local oscillator for an X-band transmitter or receiver, is capable of being electrically tuned among and within 26 adjacent frequency channels, each 1.16 MHz wide, in a band ranging from 7,040 to 7,070 GHz. The tunability of this oscillator is what sets it apart from other DROs, making it possible to use mass-produced oscillator units of identical design in diverse X-band applications in which there are requirements to use different fixed frequencies or to switch among frequency channels. The oscillator (see figure) includes a custom-designed voltage-controlled-oscillator (VCO) monolithic microwave integrated circuit (MMIC), a dielectric resonator disk (puck), and two varactor-coupling circuits, all laid out on a 25-mil (0.635-mm)-thick alumina substrate having a length and width of 17.8 mm. The resonator disk has a diameter of 8.89 mm and a thickness of 4.01 mm. The oscillator is mounted in an 8.9-mm-deep cavity in a metal housing. The VCO MMIC incorporates a negative- resistance oscillator amplifier along with a buffer amplifier. The resonator disk is coupled to a microstrip transmission line connected to the negative-resistance port of the VCO MMIC. The two varactor-coupling circuits include microstrip lines, laid out orthogonally to each other, for coupling with the resonator disk. Each varactor microstrip line is DC-coupled to an external port via a microwave choke. One varactor is used for coarse tuning to select a channel; the other varactor is used (1) for fine tuning across the 1.16-MHz width of each channel and (2) as a feedback port for a phase-lock loop. The resonator disk is positioned to obtain (1) the most desirable bandwidth, (2) relatively tight coupling with the microstrip connected to the coarse-tuning varactor, and (3) relatively loose coupling with the microstrip connected to the fine-tuning varactor. Measurements of performance showed that the oscillator can be switched among any of the 26 channels and can be phase-locked to a nominal frequency in any channel. The degree of nonlinearity of tuning was found not to exceed 2.5 percent. The tuning sensitivity was found to be 6.15 MHz/V at a bias offset of -2 V on the phase-lock-loop varactor. The phase noise of the oscillator in free-running operation was found to be -107 dBc/Hz (where dBc signifies decibels relative to the carrier signal) at 100 kHz away from the carrier frequency.

Mysoor, Narayan↗
NASA NTRS1990

The effect of coupling line loss in microstrip to dielectric resonator coupling

The interaction between a dielectric resonator and a microstrip transmission line is fundamentally a field phenomenon. However, the model of Figure 1b widely is used to represent the arrangement in Figure 1a, and predicts the behavior encountered in practice. The microstrip line of length l = n(lambda)/4 between the input and coupling planes and the lambda/4 open-circuit stub usually is assumed to be lossless. This paper considers the effect of coupling line loss on the unloaded-Q and coupling coefficient beta of the combination. It shows that transmission line loss can cause the decrease in unloaded-Q that has been observed to occur with tight coupling, and limits the coupling coefficient to a much lower value than would be obtained with a lossless coupling line.

Hearn, C. P.↗
NASA NTRS1991

Low-loss coupling to dielectric resonators

A compilation is presented of experimental observations and arguments concerning the use of dielectric resonators in applications requiring both tight coupling (beta greater than 10) and high unloaded Q, such as low loss bandpass filters. The microstrip coupled dielectric resonator is the primary focus, but an alternative coupling technique is discussed and comparatively evaluated. It is concluded that coupling factors as large as 65 are achievable.

Hearn, C. P.↗
NASA NTRS1987

Measurement and analysis of cryogenic sapphire dielectric resonators and DROs

Presented are the experimental and computational results of a study on a new kind of dielectric resonator oscillator (DRO). It consists of a cooled, cylindrically symmetric sapphire resonator surrounded by a metallic shield and is capable of higher Q's than any other dielectric resonator. Isolation of fields to the sapphire by the special nature of the electromagnetic mode allows the very low loss of the sapphire itself to be expressed. Calculations show that the plethora of modes in such resonators can be effectively reduced through the use of a ring resonator with appropriate dimensions. Experimental results show Q's ranging from 3 x 10 to the 8th at 77 K to 10 to the 9th at 4.2 K. Performance is estimated for several types of DROs incorporating these resonators. Phase noise reductions in X-band sources are indicated at values substantially lower than those previously available.

Dick, G. J.↗
NASA NTRS1990

An electronically tuned, stable 8415 MHz dielectric resonator FET oscillator for space applications

A voltage-controlled 8415-MHz FET oscillator stabilized by a dielectric resonator is described. The oscillator provides over 3.2-MHz linear electronic tuning range with a flat power output equal to +1.8 dBm (27 C, nominal), a single-sideband noise-to-carrier ratio of -68 dBc/Hz at 1 kHz off carrier, and a frequency-temperature coefficient of 0.54 parts per million/C over a -24 C to 75 C range. The oscillator withstood 150 Krads (Si) of gamma radiation with no significant performance degradation. The overall performance of the FET oscillator is far superior in many ways to that of an equivalent bipolar oscillator for space applications. For space applications, the FET dielectric resonator oscillator (DRO) is preferred over bipolar DRO because of its lower DC power consumption, better thermal frequency stability, linear electronic tunability, and higher RF output power capability.

Mysoor, Narayan R.↗
NASA NTRS1993

Ultra-stable, low phase noise dielectric resonator stabilized oscillators for military and commercial systems

EPSD has designed, fabricated and tested, ultra-stable, low phase noise microwave dielectric resonator oscillators (DRO's) at S, X, Ku, and K-bands, for potential application to high dynamic range and low radar cross section target detection radar systems. The phase noise and the temperature stability surpass commercially available DROs. Low phase noise signals are critical for CW Doppler radars, at both very close-in and large offset frequencies from the carrier. The oscillators were built without any temperature compensation techniques and exhibited a temperature stability of 25 parts per million (ppm) over an extended temperature range. The oscillators are lightweight, small and low cost compared to BAW & SAW oscillators, and can impact commercial systems such as telecommunications, built-in-test equipment, cellular phone and satellite communications systems. The key to obtaining this performance was a high Q factor resonant structure (RS) and careful circuit design techniques. The high Q RS consists of a dielectric resonator (DR) supported by a low loss spacer inside a metal cavity. The S and the X-band resonant structures demonstrated loaded Q values of 20,300 and 12,700, respectively.

Mizan, Muhammad↗
NASA NTRS1993

Lumped elements characterize Q in dielectric resonators

It has been earlier observed (Podcameni et al., 1981) that, as the coupling factor between a microstrip-coupled dielectric resonator and the line becomes much larger than unity, the unloaded quality factor (Q) of the resonator decreases. In this paper it is shown that this effect can be explained using lumped-element models of the coupling line, when the dielectric resonator is either overcoupled or undercoupled to the line.

Hearn, Chase P.↗
NASA NTRS1993

Bandwidth enhancement of dielectric resonator antennas

An experimental investigation of bandwidth enhancement of dielectric resonator antennas (DRA) using parasitic elements is reported. Substantial bandwidth enhancement for the HE(sub 11delta) mode of the stacked geometry and for the HE(sub 13delta) mode of the coplanar collinear geometry was demonstrated. Excellent radiation patterns for the HE(sub 11delta) mode were also recorded.

Lee, Richard Q.↗
NASA NTRS1988

An electronically tuned, stable 8415-MHz dielectric resonator FET oscillator for space applications

A voltage-controlled 8415 MHz FET oscillator stabilized by a dielectric resonator is described. The oscillator provides a linear electronic tuning range of over 3.2 MHz with a flat power output equal to +1.8 dBm (27 C nominal), a single-sideband noise to carrier ratio of -68 dBc/Hz at 1 kHz off carrier, and a frequency temperature coefficient of 0.54 part per million/C over a -24 to 75 C range. The oscillator withstood 150 krads(Si) of gamma radiation with no significant performance degradation. The overall performance of the oscillator is in many ways far superior to that of an equivalent bipolar oscillator for space applications.

Lakshminarayana, M.↗
NASA NTRS1992

Planar dielectric resonator stabilized HEMT oscillator integrated with CPW/aperture coupled patch antenna

A design of an active antenna with a dielectric resonator stabilized high-electron-mobility transistor (HEMT) oscillator (DRO) and an aperture-coupled patch antenna is reported. The circuit is fabricated using coplanar waveguide (CPW) with the oscillator and the antenna on opposite sides of the substrate. The active antenna was demonstrated at 7.6 GHz; however, the design can be scaled to higher frequencies. Excellent oscillator characteristics and radiation patterns were obtained.

Simons, Rainee N.↗
NASA NTRS1992

Planar dielectric resonator stabilized HEMT oscillator integrated with CPW/aperture coupled patch antenna

A new design of an active antenna with a dielectric resonator stabilized high electron mobility transistor (HEMT) oscillator (DRO) and an aperture-coupled patch antenna is reported. The circuit is fabricated using coplanar waveguide (CPW) with the oscillator and the antenna on opposite sides of the substrate. The active antenna was demonstrated at 7.6 GHz; however, the design can be scaled to higher frequencies. Excellent oscillator characteristics and radiation patterns were obtained.

Simons, Rainee N.↗
NASA NTRS1988

Maser Oscillator With Dielectric Resonators

Two-resonator design yields low phase noise. Oscillator exhibits phase noise intermediate between phase noises of unstablized microwave oscillators and stabilized ruby-maser oscillators with superconducting cavities. Contains two total-internal-reflection dielectric resonators in normally-conductive copper cavity. Two-resonator maser design provides phase stability, isolation between pump and output channels, and variable maser coupling.

Dick, G. John↗
NASA NTRS1988

Low noise cryogenic dielectric resonator oscillator

A microwave oscillator is provided which can operate at a temperature of many degrees above absolute zero while providing very low phase noise that has heretofore generally required temperatures within a few degrees K. The oscillator includes a ring-shaped resonant element of ruby (sapphire plus chromium) or iron sapphire crystal, lying adjacent to a resonator element of sapphire, so that the regenerator element lies directly in the magnetic field of the resonator element. The resonator element is substantially devoid of contact with electrically conductive material. Microwave energy of a pump frequency (e.g., 31 GHz) is outputted from the regenerator element, while signal energy (e.g., 10 GHz) is outputted from the resonator element.

Dick, G. John↗
NASA NTRS2016

Point-Wise Phase Matching for Nonlinear Frequency Generation in Dielectric Resonators

An optical resonator fabricated from a uniaxial birefringent crystal, such as beta barium borate. The crystal is cut with the optical axis not perpendicular to a face of the cut crystal. In some cases the optical axis lies in the plane of the cut crystal face. An incident (input) electromagnetic signal (which can range from the infrared through the visible to the ultraviolet) is applied to the resonator. An output signal is recovered which has a frequency that is an integer multiple of the frequency of the input signal. In some cases a prism is used to evanescently couple the input and the output signals to the resonator.

Yu, Nan↗