Distance determination by the gamma-ray time-of-flight method

The time-of-flight method is studied using coincident annihilation gamma rays with an energy of 511 keV to find the distance from a surface at which they are scattered back for detection. The gamma rays have a good penetration ability, which makes the method suitable for industrial circumstances in which the range is rendered opaque to light by flue gas and aerosols. An accuracy of 1 cm over a distance of 2 m can be obtained by increasing the averaging time by the square of the lengthening factor. The density of the surface can be studied by recording the width of the distribution of the surface measurements. This measurement needs a prolonged averaging time, but the thickness of the slag layer on top of a steel melt can be measured with a maximum error of 1.5 cm at short distances, for example     

Thermal characteristics of optical delay in fibers used in pulsedlaser rangefinding

The transit times of light pulses as functions of temperature in nylon and acryl-coated fibers and hard-clad silica (HCS) fibers are analyzed theoretically and compared with the measured results. The effect of temperature on the transit time can be explained in terms of generally known models and the physical and thermal coefficients of the materials. The thermal effect in a core-cladding interface can have unpredictable consequences, however, as in HCS fibers. Because of the increased inhomogeneities at the interface of the core-cladding, the transit time of a light pulse increases, in contrast to that in a glass fiber, at lower temperatures. Thus the light pulses have larger angles of propagation than is shown by the numerical aperture of the fiber, and at the same time the attenuation of the fiber increases     

Speeding up the PLL frequency step response by two charge pulses

A simple method is presented for speeding up the frequency step response of a PLL-based synthesizer which uses an excess output frequency to quickly cancel the accumulated phase error. In this method, current pulses are delivered to the loop filter to overdrive the PLL and later to cancel the frequency error. Experiments confirm a good agreement between measurement results and theoretical expectations     

A practical /spl Delta/-/spl Sigma/ modulator design method based on periodical behavior analysis

A method for digital delta-sigma modulator design for fractional-N frequency synthesis is presented in this paper. The design method is based on the modulator periodical behavior analysis. The modulator is designed to maintain a constant output signal sequence length which can be controlled for all input dc levels. As a result, the quantization noise power is spread over a known, arbitrarily large number of tones within the Nyquist bandwidth. Therefore, the quantization noise power never concentrates into a few dominant spurious tones. The sequence length is controlled by applying predefined initial conditions and scaling modulator buses. Consequently, the spurious-free range can be controlled as a function of the bus width. Known modulator sequence length defines the time required for full modulator and synthesizer characterization.     

Lateral Current Confinement Determines Silicon Avalanche Transistor Operation in Short-Pulsing Mode

The transient in a Si bipolar junction transistor was investigated in high-current short-pulsing ( 2 ns) mode both experimentally and numerically. A comparison of measured and simulated waveforms clearly showed that only a small fraction of the perimeter of the emitter-base interface (in the lateral direction) takes part in the switching transient when a capacitor of relatively small value (80 pF) is discharged across the transistor to obtain a current pulse of a few nanoseconds in duration. A good agreement was found between measurements and simulations in the 2-D numerical model when the effective operating perimeter was used as a parameter in the model. The results allowed reliable analyses of the thermal regime to be performed. Possible reasons for the significant current confinement in short-pulsing mode and relatively homogeneous transistor switching with longer current pulses are discussed, and a mechanism of fast lateral turn-on spread is assumed. One conclusion of practical importance is that a short-pulsing relatively high-current mode could not be realized without current confinement in the lateral direction.     

Comparison of Two Integrated BiCMOS 950 MHz Direct I/Q Modulators

Two integrated direct I/Q modulators suitable for directupconversion with an output frequency of 950 MHz and baseband frequencies of60 to 500 kHz are fabricated in a 1.2 µm and 0.8 µm BiCMOSprocess, respectively, and their performance under various operatingconditions is discussed. The modulators use different phase shiftertopologies, one of which is based on digital CML latches and the other ondifferential pairs with resistive and capacitive emitter degeneration. Bothcircuits are operated using a single 5 V supply and they consume 50 mA or115 mA depending on the topology. The main properties of the CML modulatorare, for example, an output power of –11 ± 0.5 dBm at 100 MHzand –15 ± 2.25 dBm at 950 MHz over the temperature range of–10 to +85°C, LO suppression of 38 dBc and image rejection of41 dBc.     

High accuracy CMOS position-sensitive photodetector (PSD)

A high-accuracy position-sensitive photodetector (PSD) for integrated sensor systems is presented. A 2-axis PSD composed of a dense array of vertical phototransistors and two arrays of polysilicon resistors was implemented using standard CMOS technology. Test results show better resolution and linearity as compared to a high-quality conventional PSD     

Integrated Time-to-Digital Converters Based on Interpolation

The main features of two time-to-digital convertersbased on interpolation are presented, together with some measurementresults. The first converter is based on digital delay line interpolatorsand has been implemented in a 1.2 µm CMOS process.It has a single-shot resolution of 1 ns (-value)and a nonlinearity less than ±50 ps in the measurementrange 5 to 500 ns. The power consumption of the circuit is 15mW. The second time digitizer has analog interpolators basedon time-to-voltage conversion and has been implemented in a 1.2 µm BiCMOS process. It has a single-shot resolutionof 50 ps and a nonlinearity less than 150 ps in the measurementrange 1 to 300 ns. The power consumption of this circuit is 200mW.     

A 700 MHz laser radar receiver realized in 0.18 μm HV-CMOS

This study presents a CMOS receiver chip realized in 0.18 µm High-Voltage CMOS (HV-CMOS) technology and intended for high precision pulsed time-of-flight laser range finding utilizing high-energy sub-ns laser pulses. The IC chip includes a trans-impedance preamplifier, a post-amplifier and a timing comparator. Timing discrimination is based on leading edge detection and the trailing edge is also discriminated for measuring the width of the pulse. The transimpedance of the channel is 25 kΩ, the uncompensated walk error is 470 ps in the dynamic range of 1:21,000 and the input referred equivalent noise current 450 nA (rms).     

On-chip offset generator for accurate integral non-linearity testing of A/D converters and D/A-A/D converter pairs

It has recently shown how a constant dc offset between two low-quality test signals can be used to test the integral nonlinearity (INL) of A/D converters (ADCs) without an accurate test stimulus, and how the same method can be used to test the INL of D/A converters (DACs) as well. We propose here an on-chip offset generator for producing the constant offset and analyse its limitations. Experimental tests on the 122 × 22 μm² offset generator fabricated in 130 nm CMOS process show that it can be used to test the INL of 12-b DACs and ADCs. The generator is rail-to-rail capable so that almost the whole input/output range of converters can be tested. Moreover, if the proposed offset generator is used in a ratiometric test setup as proposed here as well, the influence of a reference voltage drift on measurement accuracy is cancelled out. Because of its small size, simple design, rail-to-rail capability and immunity to reference voltage changes, the proposed offset generator is well suited for built-in self-test usage.