Microstrip-fed slot array antenna having 45/spl deg/ inclined linear polarisation

A 45/spl deg/ inclined linearly polarised slot array antenna with microstrip line feed has been developed. To simplify the feed system, series feeding is adopted to excite the radiating slots. An eight-element slot array, with an operating frequency that is of 12 GHz band, has been designed and its characteristics are investigated by the moment method analysis. Measured results are also presented to validate the numerical evaluations.     

A CMOS smart temperature sensor with a 3/spl sigma/ inaccuracy of /spl plusmn/0.5/spl deg/C from -50/spl deg/C to 120/spl deg/C

A low-cost temperature sensor with on-chip sigma-delta ADC and digital bus interface was realized in a 0.5 /spl mu/m CMOS process. Substrate PNP transistors are used for temperature sensing and for generating the ADC's reference voltage. To obtain a high initial accuracy in the readout circuitry, chopper amplifiers and dynamic element matching are used. High linearity is obtained by using second-order curvature correction. With these measures, the sensor's temperature error is dominated by spread on the base-emitter voltage of the PNP transistors. This is trimmed after packaging by comparing the sensor's output with the die temperature measured using an extra on-chip calibration transistor. Compared to traditional calibration techniques, this procedure is much faster and therefore reduces production costs. The sensor is accurate to within /spl plusmn/0.5/spl deg/C (3/spl sigma/) from -50/spl deg/C to 120/spl deg/C.     

45/spl deg/ slanted fibre Bragg grating design with prism coupled holographic exposure

A holographic technique for forming 45/spl deg/ tilted fibre gratings using two 45/spl deg/-90/spl deg/, -45/spl deg/ fused silica prisms is described. The technique reduces fringe distortion due to the lens effects of the fibre during exposure. Details of the experimental system and grating performance are given.     

Low-crosstalk and high-efficiency optical interconnection using 45/spl deg/-ended connection rods

A new architecture for an optical interconnection system that can be applied in a waveguide-embedded optical printed circuit board is demonstrated. 45/spl deg/-ended optical connection rods were used to guide light paths perpendicularly between surface-emitting lasers (or photodiode) and waveguides. A 1.25 Gbit/s data link was successfully demonstrated.     

Obliquely arranged feed waveguide for alternating-phase fed single-Layer slotted waveguide array

An alternating phase fed waveguide array with an oblique arrangement of feed waveguide is proposed. It belongs to single-layer waveguide arrays developed by the authors. Conventional arrays with radiation waveguides arranged perpendicularly to the feed waveguide suffer from accumulated reflection from coupling windows after round-trip propagation at the input port. In the proposed oblique arrangement, the reflections from each coupling window will not accumulate in phase but be diffused away out of phase. First, the design of obliquely arrayed T-junctions is conducted using two-dimensional finite element method (FEM). Then basic operations of the reflection canceling as well as improved voltage standing-wave ratio at the antenna input are confirmed by experiments. Almost the same radiation patterns and gain as the conventional arrays are observed in the measurements     

PCB-compatible optical interconnection using 45/spl deg/-ended connection rods and via-holed waveguides

In this paper, a new architecture for a chip-to-chip optical interconnection system is demonstrated that can be applied in a waveguide-embedded optical printed circuit board (PCB). The experiment used 45/spl deg/-ended optical connection rods as a medium to guide light paths perpendicularly between vertical-cavity surface-emitting lasers (VCSELs), or photodiodes (PDs) and a waveguide. A polymer film of multimode waveguides with cores of 100/spl times/65 /spl mu/m was sandwiched between conventional PCBs. Via holes were made with a diameter of about 140 /spl mu/m by CO/sub 2/-laser drilling through the PCB and the waveguide. Optical connection rods were made of a multimode silica fiber ribbon segment with a core diameter of 62.5 and 100 /spl mu/m. One end of the fiber segment was cut 45/spl deg/ and the other end 90/spl deg/ by a mechanical polishing method. These fiber rods were inserted into the via holes formed in the PCB, adjusting the insertion depth to locate the 45/spl deg/ end of rods near the waveguide cores. From this interconnection system, a total coupling efficiency of about -8 dB was achieved between VCSELs and PDs through connection rods and a 2.5 Gb/s /spl times/ 12-ch data link demonstrated through waveguides with a channel pitch of 250 /spl mu/m in the optical PCB.     

A two-beam slotted leaky waveguide array for mobile reception ofdual-polarization DBS

A two-beam slotted leaky waveguide array for mobile reception of dual-polarization direct broadcast from satellite (DBS) is realized in a single-layer structure. Two feed waveguides attached at both ends of cross-slotted radiating waveguides excite the leaky waves propagating in opposite directions. Each of them radiates either of two circularly polarized waves in symmetrical beam directions. Balanced design of two beams for each polarization imposes symmetry in the array design of slots. The slot coupling distribution is optimized for the maximum gain under this symmetry condition. A model antenna in about a 300-mm square is fabricated for experiments in the 12-GHz band. Antenna efficiency of 71% and 64% is obtained for each beam in different polarizations     

Topology design and fabrication of an efficient double 90/spl deg/ photonic Crystal waveguide bend

We have designed and fabricated a novel 90/spl deg/ bend in a photonic crystal waveguide. The design was obtained using topology optimization and the fabricated waveguide displays a bend loss for transverse-electric-polarized light of less than 1 dB per bend in a 200-nm wavelength range.     

A Ka-band InP MMIC 180/spl deg/ phase switch

A new type of Ka band (26 to 36 GHz) 180 degree phase switch (bi-phase modulator) monolithic microwave integrated circuit has been developed for the EC funded FARADAY radio astronomy project. This integral component forms part of a chip set for a very low noise switching radiometer operating at a temperature of approximately 15 K. To maximize the sensitivity of the radiometer lattice-matched indium phosphide HEMT technology has been used: all of the active components of the radiometer, with the exception of the detectors, have been manufactured on a single wafer process. Design principles are described, together with a comparison of modeled and measured results. The results show an average insertion loss of 3.5 dB, return loss of better than 10 dB and an average phase difference close to 170/spl deg//spl plusmn/10/spl deg/ the 26-36 GHz band.     

High efficiency 90/spl deg/ silica waveguide bend using an air hole photonic crystal region

We propose the hybrid integration of an air hole photonic crystal (PhC) structure with a high /spl Delta/ (0.75%) single-mode silica waveguide to achieve an ultracompact high efficiency 90/spl deg/ bend for transverse-magnetic polarized light. Diffraction from the periodic boundary between the PhC and silica waveguide regions is shown to seriously degrade the optical efficiency of the bend. A microgenetic algorithm (/spl mu/GA) combined with a two-dimensional finite-difference time-domain method is used to modify the PhC and its boundary layer to suppress this diffraction which in turn maximizes bend efficiency. The final optimized structure has a 99.4% bend efficiency at a wavelength of 1.55 /spl mu/m and occupies an area of only 27 /spl times/ 27 /spl mu/m.     

Performance of a planar filter using a 0/spl deg/ feed structure

The advantage of using a 0/spl deg/ feed structure in filter design is that two extra transmission zeros are created in the stopband while the passband response remains unchanged. This feed structure is analyzed by using transmission matrices. A new lumped-circuit model for a coupled resonator filter is then proposed to take into account the effects of this feed structure. Finally, the feed structure is applied to the design of a cross-coupled filter. All the theoretical analysis and design procedures have been successfully verified by experiment results.     

Slotted waveguide linear array with polarisation control

The design of an experimental dual-mode waveguide linear array antenna is described and measurements on a 10-element model are presented. The antenna comprises a `notched? wall dual-mode waveguide containing an array of suitably located transverse/longitudinal slot pairs. Polarisation control is achieved by feeding the array through a 3 dB hybrid followed by a phase shifter.     

A wideband compact parallel-strip 180/spl deg/ Wilkinson power divider for push-pull circuitries

A Wilkinson power divider with a differential output implemented in parallel-strip-line (PSL) is proposed. Taking full advantages of the PSL technology and a three-stage cascaded design, more than 170% impedance and isolation bandwidths are obtained. Inherent to the PSL structure, the 180/spl deg/ differential output is frequency-independent. A class-B push-pull power amplifier employing the devised concept is designed, showing a peak efficiency of 44% over a 4-GHz bandwidth. Without exploiting any extra and external low-pass filters, the proposed design can produce startling second-harmonic suppressions (more than 50dB) over the whole working dynamics and operated bandwidth.     

A single-layer slotted leaky waveguide array antenna for mobilereception of direct broadcast from satellite

This paper proposes a single-layer slotted leaky waveguide array antenna for mobile DBS reception. A single-layer feed structure is proposed, where the feed waveguide is in the same layer as the radiating waveguides. This results in the simple fabrication of slotted waveguide arrays, suitable for mass production. Short radiating leaky waveguides are used to get a large beam-tilting angle of about 50° for the horizontal installation of the antenna and a beamwidth broad enough to dispense with mechanical steering in the elevation plane. A prototype antenna sized 30 cm by 21 cm has a maximum of 74% efficiency and more than 69% efficiency within the DBS band. It also has a broad l-dB beamwidth of 7.5° in the elevation plane, which enables clear DBS reception by a picture tube display over about one-third the area of Japan without elevation tracking     

A Broadbanded Solid-State Microwave Maser Operating at 77.4/spl deg/K

This paper considers several aspects of the problem of obtaining solid-state microwave maser action at 77.4/spl deg/K. A maser cavity, designed to have a large filling factor, high unloaded Q, and tunability over a two per cent range is described. Using this cavity, a study was made of ruby as a maser material at 77.4/spl deg/K. An important result of this study is the determination of the optimum Cr/sup +++/ concentration for 77.4/spl deg/K maser action. A well-known broadbanding technique was applied to the maser to increase its gain-bandwidth product. Two high-Q microwave cavities spaced three-quarters wavelength apart were placed in front of the maser cavity to produce the broadbanding. The experimental results are given, and the usefulness of this technique as a method of improving maser performance is evaluated. The broadbanded maser had a midband gain of 14.5 dB and a bandwidth of 7.5 Mc/s at a signal frequency of 9.3 Gc/s. Approximately 31 watts of pump power at 23.4 Gc/s were required.     

A 360/spl deg/ Reflection-Type Diode Phase Modulator (Correspondence)

A 360/spl deg/ phase modulator using two series-tuned varactors in a parallel connection is described. The design minimizes the change in total phase shfit with frequency and gives a small attenuation ripple. The modulator is centered at 2 GHz and gives a total phase shift at 360/spl deg/ at the center frequency, an attenuation ripple of 1.3 dB over a 10-percent bandwidth and a 7/spl deg/ decrease of phase shift at the band edges.     

Nitride-based LEDs with 800/spl deg/C grown p-AlInGaN-GaN double-cap layers

GaN-based light-emitting diodes (LEDs) with various p-cap layers were prepared. It was found that surface morphologies of the LEDs with 800/spl deg/C grown cap layers were rough due to the low lateral growth rate of GaN. It was also found that 20-mA forward voltage of the LED with 800/spl deg/C grown p-AlInGaN-GaN double-cap layer was only 3.05 V. Furthermore, it was found that we could achieve a high output power and a long lifetime by using the 800/spl deg/C grown p-AlInGaN-GaN double-cap layer.     

High-power 2.3-/spl mu/m GaSb-based linear laser array

High-power 2.3-/spl mu/m In(Al)GaAsSb-GaSb type-I double quantum-well diode laser arrays were fabricated and characterized. Linear laser arrays with 19 100-/spl mu/m-wide elements on a 1-cm-long bar generated 10 W in continuous-wave (CW) mode and 18.5 W in quasi-CW mode (30 /spl mu/s/300 Hz) at a heatsink temperature of 18/spl deg/C. Array power conversion efficiency peaked at 30 A and was about 9%. Device internal efficiency was about 50%. Individual laser differential gain with respect to current was about twice as high as in InP-based laser heterostructures, demonstrating the potential of GaSb-based material system for high-power CW room-temperature laser diode arrays.     

High-efficiency broad-band transmission through a double-60/spl deg/ bend in a planar photonic Crystal single-line defect waveguide

We present two designs to improve the transmission of a conventional double-60/spl deg/ bend in a single-line defect planar photonic crystal waveguide by locally optimizing the shape and the size of air holes of a photonic crystal lattice at the corners. We fabricate these devices on a silicon-on-insulator substrate and characterized them using tunable laser sources over a wavelength range from /spl lambda/=1.259 /spl mu/m to /spl lambda/=1.641 /spl mu/m. As we show, over a 9% bandwidth, less than 1-dB loss/bend was observed. In order to theoretically validate these experimental results, the three-dimensional finite-difference time-domain simulations are performed and found to agree with the experimental results.