Quasi-optical antenna-mixer-array design for terahertz frequencies

A new quasi-optical antenna-mixer-array design for terahertz frequencies is presented. In the design, antenna and mixer are combined into an entity, based on the technology in which millimeter-wave horn antenna arrays have been fabricated in silicon wafers. It consists of a set of forward- and backward-looking horns made with a set of silicon wafers. The front side is used to receive incoming signal, and the back side is used to feed local oscillator signal. Intermediate frequency is led out from the side of the array. Signal received by the horn array is picked up by antenna probes suspended on thin silicon-oxynitride membranes inside the horns. Mixer diodes will be located on the membranes inside the horns. Modeling of such an antenna-mixer-array design is done on a scaled model at microwave frequencies. The impedance matching, RF and LO isolation, and patterns of the array have been tested and analyzed

Probe modeling for millimeter-wave integrated-circuit horn antennas

Integrated-circuit probe-excited horn-antenna arrays etched in silicon are well developed. They are a very promising class of antenna arrays for milli-meter and submillimeter applications. Further development of this technology involves integrating mixers and amplifiers into the antenna arrays. In an effort to develop an antenna-mixer array based on the existing technology, various antenna probes inside the pyramidal horns have been examined on scaled model-horns at the microwave frequencies. In this paper, modeling results and design principles of these antenna probes have been presented, which include the resonant impedance, the operating frequency, and the bandwidth of the horn antennas. These measurement results provide a guideline in designing probes for millimeter/submillimeter-wave integrated-circuit horn-antenna-mixer arrays

Aperture efficiency of chemically etched horns at 93 GHz

The aperture efficiency of monolithic two-dimensional horn imaging arrays has been optimized at 93 GHz. The imaging arrays consist of several silicon wafers into which arrays of pyramidal horns are etched chemically. Dipole antennas and detectors are suspended on thin silicon oxynitride membranes on one of the central silicon wafers about halfway down the horns. The devices are 7×7 arrays with a 1 λ opening and a 71° flare angle. Antenna impedances have been measured on a low-frequency model. A variety of millimeter-wave dipole antennas and bolometers have been designed and tested. A large-area bismuth thin-film power meter is used to obtain accurate absolute power. The measured aperture efficiency improved from 44% to 72%. The highest system coupling efficiency with a lens was 36% including lens absorption and reflection losses

Bar-grid oscillators

Grid oscillators are an attractive way of obtaining high power levels from the solid-state devices, since potentially the output powers of thousands of individual devices can be combined. The active devices do not require an external locking signal, and the power combining is done in free space. Thirty-six transistors were mounted on parallel brass bars, which provide a stable bias and have a low thermal resistance. The output power degraded gradually when the devices failed. The grid gave an effective radiated power of 3 W at 3 GHz. The directivity was 11.3 dB, and the DC-to-RF efficiency was 22%. Modulation capabilities of the grid were demonstrated. An equivalent circuit model for the grid is derived, and comparison with experimental results is shown

A 100-Element MESFET Grid Oscillator

A planar grid oscillator which combines the outputs of 100 devices quasi-optically is presented. The planar configuration is attractive because it is compatible with present-day IC fabrication techniques. In addition, the grid's structure leads to a transmission-line model that can readily be applied to the design of larger grids in the future. This approach is particularly attractive for wafer-scale integration at millimeter wavelengths. The grid oscillates near 5 GHz and can be frequency tuned with mirror spacing from 4.8 GHz to 5.2 GHz. The far-field radiation patterns for the grid are shown. From the pattern, the directivity is calculated to be 16 dB. The ERP is measured to be 25 W. The DC input power is 3 W, and the power radiated from the grid is calculated to be 0.625 W. This gives a DC-to-RF efficiency of 20%

Thin-film power-density meter for millimeter wavelengths

A quasi-optical power density meter for millimeter and submillimeter wavelengths has been developed. The device is a 2-cm^2 thin-film bismuth bolometer deposited on a mylar membrane. The resistance responsivity is 150 Ω/W, and the time constant is 1 min. The meter is calibrated at DC. The bolometer is much thinner than a wavelength, and can thus be modeled as a lumped resistance in a transmission-line equivalent circuit. The absorption coefficient is 0.5 for 189-Ω/square film. The power-density meter has been used to measure absolute power densities for millimeter-wave antenna efficiency measurements. Absolute power densities of 0.5 mW/cm^2 have been measured to an estimated accuracy of 5%

Practitioner accounts and knowledge production: an analysis of three marketing discourses

Responding to repeated calls for marketing academicians to connect with marketing actors, we offer an empirically-sourced discourse analysis of the ways in which managers portray their practices. Focusing on the micro-discourses and narratives that marketing actors draw upon to represent their work we argue that dominant representations of marketing knowledge production present a number of critical concerns for marketing theory and marketing education. We also evidence that the often promoted idea of a need to close the gap between theory - as a dominant discourse - and practice, as a way of doing marketing, is problematic to pursue. We suggest that a more fruitful agenda resides in the development of a range of polyphonic and creative micro-discourses of management, promoting context, difference and individual meaning in marketing knowledge production

Quasi-optical power-combining arrays

Semiconductor devices have limited power handling capabilities at high frequencies, particularly at millimeter-wave frequencies. A method is presented for overcoming this problem by combining the outputs of several devices quasi-optically in a resonator cavity. This method has been applied to a number of solid-state devices, including Gunn diodes and MESFETs. The devices do not require an external locking signal because they lock to a mode of the resonator cavity. Effective radiated powers of 22 watts for a 4×4 array of Gunn diodes and 25 watts for a 10×10 array of MESFETs have been achieved