321 research outputs found

    Diode-Grid Oscillators

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    Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state devices in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. This approach is attractive because the active devices do not need an external locking signal, and the combining is done in free space. The loaded grid is a simple planar structure suitable for monolithic integration. Preliminary measurements on a nine-diode grid at 10 GHz show power-combining and frequency-locking without an external locking signal

    An LDMOS VHF class-E power amplifier using a high-Q novel variable inductor

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    In this paper, an lateral diffused metal-oxide-semiconductor-based very high-frequency class-E power amplifier has been investigated theoretically and experimentally. Simulations were verified by amplifier measurements and a record-high class-E output power was obtained at 144 MHz, which is in excellent agreement with simulations. The key of the results is the use of efficient device models, simulation tools, and the invention of a novel high-Q inductor for the output series resonance network. The latter allows for low losses in the output network and, simultaneously, a wide tuning range for maximum output power or maximum efficiency optimization

    A millimeter-wave slot-V antenna

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    A V-shaped slot antenna built on a dielectric substrate is presented. The antenna is a nonresonant, traveling-wave design, with a predicted impedance in the range from 50 Ω to 80 Ω. Calculations indicate that this antenna should have a gain of 15 dB with 3 dB beamwidths of 10° in the H plane and 64° in the E plane. Pattern measurements at 90 GHz support the theory. It should be possible to equalize the two beamwidths with a cylindrical lens. The broad bandwidth and high gain characteristics make the slot- V a good candidate for picosecond optoelectronic measurements. Fabrication is simple, and it should be possible to make this antenna at wavelengths as short as 10 μm with conventional photolithography

    A 2.7-kW, 29-MHz class-E/F/sub odd/ amplifier with a distributed active transformer

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    A Class-E/Fodd high power amplifier (PA) using the distributed active transformer (DAT) is demonstrated at 29MHz. The DAT combines the output power from four VDMOS push-pull pairs. The zero voltage switching (ZVS) condition is investigated and modified for the Class-E/Fodd amplifier with a non-ideal output transformer. All lumped elements including the DAT and the transistor package are modeled and optimized to achieve the ZVS condition and the high drain efficiency. The PA exhibits 2.7kW output power with 79% drain efficiency and 18dB gain at 29MHz

    Grid-Oscillator Beam-Steering Array

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    Recently Liao and York (see IEEE Trans. Microwave Theory Tech., vol.41, no.10, p.1810, 1993) showed that beam-steering can be achieved by detuning the end elements of a coupled-oscillator array. The advantage of this approach is that no phase shifters are required. Liao and York used a single line array of patch antennas. Here we report the results for a pair of 1×4 HEMT line-grid oscillators at 11 GHz. This array can scan from -6.5° to +5° by changing the bia

    Self-heated thermocouples for far-infrared detection

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    A novel self-heated Bi-Sb thermocouple for far-infrared detection has been developed. The detector is suitable for integration with monolithic antennas and imaging arrays. The device is fabricated in a single photolithography masking step using a photoresist-bridge technique. This bridge technique has also been used to make microbolometers with lower 1/f noise than those made by two conventional masking steps. The thermocouples have a noise equivalent power (NEP) of 7×10^−10 W/(√Hz) and a 3-dB frequency response of 150 kHz

    Approximation Techniques for Planar Periodic Structures

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    The rigorous calculation of electromagnetic properties of periodic meshes using moment methods requires considerable algebraic work and computer resources. In this paper, a number of easy to use approximation techniques for analyzing thin structures with square, rectangular, and circular holes are presented. Formulas for the effective impedante of these meshes are described which can easily take into account oblique incidence and the presence of a dielectric substrate. In addition, techniques for analyzing more complex-shaped apertures such as a cross are discussed. These methods are more accurate than existing approximation techniques and can be applied to a wide range of situations that could not be handled before

    Air-bridge microbolometer for far-infrared detection

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    A new microbolometer for far-infrared detection has been fabricated that allows an increase in sensitivity of a factor of 4 over the best previously reported bolometer. By suspending the detector in the air above its substrate a reduction in the thermal conductance out of the device by a factor of 5 has been achieved. At a modulation frequency of 100 kHz this microbolometer has an electrical noise equivalent power of 2.8×10^−11 W(Hz)^−1/2. A thermal model is also presented that accurately fits the response of the detector

    Wave techniques for noise modeling and measurement

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    The noise wave approach is applied to analysis, modeling, and measurement applications. Methods are presented for the calculation of component and network noise wave correlation matrices. Embedding calculations, relations to two-port figures-of-merit, and transformations to traditional representations are discussed. Simple expressions are derived for MESFET and HEMT noise wave parameters based on a linear equivalent circuit. A noise wave measurement technique is presented and experimentally compared with the conventional method

    Surface-Wave Losses of Coplanar Transmission Lines

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    Coplanar transmission lines lose energy to surface waves when the propagation constant of the surface-wave mode exceeds that of the transmission line. This happens when the substrate thickness is an appreciable fraction of a wavelength. The losses should become important in integrated circuits at near-millimeter wavelengths because it is hard to make the substrate thickness small compared to a wavelength. In this paper we have developed a theory based on reciprocity for predicting these losses. We also utilized the quasi-static approximation method to derive expressions for propagation constants and line impedances. Experimental measurements were made for the surface-wave losses in the two strip line, the two slot line and the three wire line, and the results obtained were consistent with the theory
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