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.     

A novel approach to the design and implementation of dual-band compact planar 90/spl deg/ branch-line coupler

This paper presents the design of a novel branch-line coupler that can operate at two arbitrary frequencies. The proposed circuit also features compact size and planar structure. Explicit design formulas of the proposed dual-band coupler are analytically derived. Moreover, practical issues such as the realization of branch-line impedance and optimum choice of circuit topologies are addressed. For verification purposes, both simulated and measured results of a microstrip branch-line coupler operating at 900/2000 MHz are included.     

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.     

90/spl deg/C continuous-wave operation of 1.83-/spl mu/m vertical-cavity surface-emitting lasers

Excellent lasing performance is demonstrated for a 1.83-/spl mu/m InGaAlAs-InP vertical-cavity surface-emitting laser (VCSEL) utilizing the buried tunnel junction technology. Threshold currents as low as 190 /spl mu/A at 20/spl deg/C and operating temperatures as high as 90/spl deg/C have been measured. These values are the best ones reported so far for long-wavelength VCSELs.     

Stable range enhancement in a symmetric confocal two-rod resonator with 90/spl deg/ optical rotator

We propose a method to eliminate the narrow unstable region of a symmetric two-rod resonator with a 90/spl deg/ optical rotator which is used to compensate for thermal birefringence of the laser rod. The narrow unstable region is caused by the difference between the thermal focal lengths of the radial and tangential directions of a laser rod. Using the g-diagram analysis, we find that the narrow unstable region can be removed in the resonator configuration of a symmetric confocal type. We investigate the effect of the distance between two rods of the proposed resonator on the stability and the beam quality.     

Precise 90/spl deg/ quadrature current-controlled oscillator tunable between 50-130 MHz

A VLSI continuous time sinusoidal OTA-C quadrature oscillator fabricated in a standard double-poly 0.8 /spl mu/m CMOS process is presented. The oscillator is tunable in the frequency range from 50-130 MHz. The two phases produced by the oscillator show an extremely low phase difference error (less than 2/spl deg/ over the whole frequency range). A novel current mode amplitude control scheme is developed that allows for very small amplitudes. Experimental results are provided.     

A precise 90/spl deg/ quadrature OTA-C oscillator tunable in the 50-130-MHz range

We present a very-large-scale integration continuous-time sinusoidal operational transconductance amplifiers quadrature oscillator fabricated in a standard double-poly 0.8-/spl mu/m CMOS process. The oscillator is tunable in the frequency range from 50 to 130 MHz. The two phases produced by the oscillator show a low-quadrature phase error. A novel current-mode amplitude control scheme is developed that allows for very small amplitudes. Stability of the amplitude control loop is studied as well as design considerations for its optimization. Experimental results are provided.     

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.     

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.     

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.     

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.     

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.     

Low-driving-current temperature-stable 10 Gbit/s operation of p-doped 1.3 /spl mu/m quantum dot lasers between 20 and 90/spl deg/C

Low-driving-current temperature-stable 10 Gbit/s direct modulation was achieved for optimised 200 mum-long short cavity 1.3 mum p-doped quantum dot lasers. Driving conditions were 25.2 mA_p-p for the modulation current and 23.4 mA for the bias current through the whole temperature range from 20 to 90degC     

A 2-V 23-/spl mu/A 5.3-ppm//spl deg/C curvature-compensated CMOS bandgap voltage reference

A high-order curvature-compensated CMOS bandgap reference, which utilizes a temperature-dependent resistor ratio generated by a high-resistive poly resistor and a diffusion resistor, is presented in this paper. Implemented in a standard 0.6-/spl mu/m CMOS technology with V/sub thn//spl ap/|V/sub thp/|/spl ap/0.9 V at 0/spl deg/C, the proposed voltage reference can operate down to a 2-V supply and consumes a maximum supply current of 23 /spl mu/A. A temperature coefficient of 5.3 ppm//spl deg/C at a 2-V supply and a line regulation of /spl plusmn/1.43 mV/V at 27/spl deg/C are achieved. Experimental results show that the temperature drift is reduced by approximately five times when compared with a conventional bandgap reference in the same technology.     

Broadband 180/spl deg/ bit phase shifter using a /spl lambda//2 coupled line and parallel /spl lambda//8 stubs

In this paper, a broadband 180/spl deg/ bit phase shifter using a new switched-network was presented. The new network is composed of a /spl lambda//2 coupled line and parallel /spl lambda//8 open and short stubs, which are shunted at the edge points of a coupled line, respectively. According to a desired phase shift, it provides a controllable phase dispersive characteristic by the proper determination of Z/sub m/,Z/sub s/, and R values. The 180/spl deg/ bit phase shifter operated at 3 GHz was fabricated and experimented using design graphs which provide the required Z/sub m/,Z/sub s/ values, and I/O match and phase bandwidths. The experimental performances showed broadband characteristics.     

Light-output enhancement in a nitride-based light-emitting diode with 22/spl deg/ undercut sidewalls

We successfully fabricated nitride-based light-emitting diodes (LEDs) with /spl sim/22/spl deg/ undercut sidewalls. The /spl sim/22/spl deg/ etching undercut sidewalls were achieved by controllable inductively coupled plasma reactive ion etching. With a 20-mA current injection, the output powers of the LED with /spl sim/22/spl deg/ undercut sidewalls and standard LED were 5.1 and 3 mW, respectively-a factor of 1.7 times enhancement. It was found that such undercut sidewalls could enhance the probability of escaping the photons outside from the LED in the near horizontal and in-plane directions. This simple and controllable method is beneficial to fabricate brighter LEDs.     

A slotted post-wall waveguide array with interdigital structure for 45/spl deg/ linear and dual polarization

This work proposes a dual-polarized planar antenna; two post-wall slotted waveguide arrays with orthogonal 45/spl deg/ linearly-polarized waves interdigitally share the aperture on a single layer substrate. Uniform excitation of the two-dimensional slot array is confirmed by experiment in the 25 GHz band. The isolation between two slot arrays is also investigated in terms of the relative displacement along the radiation waveguide axis in the interdigital structure. The isolation is 33.0 dB when the relative shift of slot position between the two arrays is -0.5/spl lambda//sub g/, while it is only 12.8 dB when there is no shift. The cross-polarization level in the far field is -25.2 dB for a -0.5/spl lambda//sub g/ shift, which is almost equal to that of the isolated single polarization array. It is degraded down to -9.6 dB when there is no shift.     

A 310/spl deg//3.6-dB K-band phaseshifter using paraelectric BST thin films

Ferro- and para-electric BaSrTiO/sub 3/ (/spl epsiv//sub r//spl sim/350 and tg/spl delta//spl sim/5/spl times/10/sup -2/ at 0V) thin films were deposited by low-cost sol-gel techniques. Subsequently, the films were used for fabricating coplanar waveguide phaseshifters using tunable finger-shaped capacitors. A 310/spl deg/ phaseshift was obtained at 30GHz and 35V of tuning voltage with 3.6dB of insertion loss yielding a figure of merit of 85/spl deg//dB.