Frequency Of Output Signal Research Articles

A New Method for I/Q Impairment Detection and Evaluation in OFDM Transmitters

Detection and evaluation of impairments in the baseband section (I/Q impairments) of orthogonal frequency-division multiplexing digital transmitters are dealt with. A new measurement method is, in particular, proposed with the aim of overcoming key limitations exhibited by already-available approaches, which are generally designed for traditional digital transmitters and based on I/Q diagram analysis. The method is nonintrusive, exploits an analytical model that properly accounts for the way I/Q impairments affect the radio frequency output signal, with special regard to mirror subcarrier interference, and implements an original procedure to estimate impairment amounts. Aside from describing the analytical model along with the fundamental stages of the measurement procedure, this paper gives details of the extended experimental activity carried out on laboratory signals characterized by known I/Q impairments in order to assess the performance of the method

Experimental analysis of power supply interference rejection in commercial quasi-digital sensors

The power supply interference rejection of four commercial quasi-digital sensors (ADXL202, SMT160-30, TMP04, MAX6676) has been experimentally analyzed by using a test method that allows us to easily select the amplitude and frequency of the interfering signal. Slow and fast changes of the sensor supply voltage yield bias errors and increase the uncertainty of the output signal parameter (time interval, mark-space ratio) that carries the information about the measured physical quantity. The effects of the interference on the output information are unique when the interfering frequency equals a multiple of the output signal frequency. For the sensors analyzed, a 100 mV sine-wave interference increased the uncertainty from 14 to 140 times that obtained when the supply voltage was clean. These experimental results cannot be directly predicted from the power supply rejection ratio value and the performance figures in manufacturer's data sheets.

The possibility of utilizing the high permeability magnetic materials in construction of magnetoelastic stress and force sensors

The paper presents new possibilities in the field of construction of the magnetoelastic stress and force sensors. Two methods of applying mechanical stress to the core of the magnetoelastic sensing elements were presented. The first one is suitable for bulk magnetic materials, such as ferrites. The second method can be utilized in a case of both ribbon and bulk ring cores. Such ring-shaped cores can be made of amorphous alloys as well as ferrites. Both these methods enable achieving uniform distribution of stresses in the samples with closed magnetic circuit. The experiment was performed on high permeability Mn–Zn ferrite and Co-rich amorphous alloy. The results confirm, that magnetic properties of both ferrite and amorphous alloys change significantly under compressive stress from the external forces. The relative changes of the permeability exceed 100% for stresses up to 25 MPa. Paper presents also functional characteristics of the magnetoelastic sensor which operate in the resonant circuit configuration. Output frequency signal from the sensor operating in this configuration is suitable for further digital processing.

A Retro-Directive Antenna Array With Phase Conjugation Circuit Using Subharmonically Injection-Locked Self-Oscillating Mixers

In this paper, a novel phase conjugation circuit and its application to retro-directive antennas are presented. The phase conjugation circuit uses a balanced circuit structure with subharmonically injection locked self-oscillating mixers oscillating at /spl omega/. In the operation, an input signal at /spl omega//2 is converted to its conjugated signal with no external source required for LO signal pumping, and the output signal frequency is locked at the same frequency of the input signal. The developed phase conjugation circuit is implemented with active antennas to become a retro-directive antenna array. Both the theoretical and measured results of phase conjugation and retro-directive performance are shown in good agreement.

Translinear sinusoidal frequency tripler

By direct synthesis of a trigonometric identity, this circuit generates an output signal frequency that is three times the input signal frequency. Frequency-doubling with free 90° phase shifter is embedded in the same circuitry. Simulation results demonstrate the functionality and the performance of the circuit.

Smart Sensors with Frequency output: State-of-the-art and Future Development

State-of-the-art of frequency (duty cycle, period, tinle interval) output sensors is considercd in the Paper. The reasons of lag of frequency output signal processing fronl reaching of nlodern microelectronic technologies is surveyed. It is exhibited, that for effective solution of the problem the tight international cooperation and creation of particular infrastructure is nccessary. The International Frequency Sensor Association (IFSA) creation in 1999 was the first step to such effeclive cooperation.

The design of miniaturised displacement transducers for deep hole diameter measurement

The paper presents a new approach to the design of a miniaturised displacement transducer for deep hole measurement. By exploiting the induced eddy current effects detected by chip coils, the sensor generates a frequency output signal. The sensor chip coil can be manufactured by the similar processes to those used for manufacturing a printed circuit board (PCB) which allows them to be miniaturised. The paper elaborates on the construction and mechanism by which the displacement is directly transferred to a frequency output. It also reports on the transducer, which uses two contact probes for transmitting the displacement to a non-contact sensing element. Experimental results demonstrate the stability, linearity, measurement range and accuracy of the sensor system.

Silicon active optical sensors: from functional photodetectors to smart sensors

We have developed new types of functional and smart optical silicon sensors, based on ITO/multichannel insulator/silicon structures, which are able to execute electronic functions such as amplifying the photocurrent (without avalanche multiplication), transforming the input optical signal into a radio frequency output signal and transforming the analogue input optical signal to a digital output form, without external active electronic components. These new functional optical sensors allow a substantial simplification of the registration of optical signals as well as of the electronic scheme to be used.

New kind of highly sensitive magnetic sensors with wide bandwidth

In physical, technical and biological systems measurements of weak magnetic fields are of great importance. A highly sensitive magnetic sensor with a frequency output signal for robust information transmission is presented. It consists of a tuned r.f. oscillator the frequency of which is determined by a weak external magnetic field in the magnetic range of picotesla to microtesla (a magnetically controlled oscillator, MCO). This low-noise magnetic-field-to-frequency converter with a large bandwidth ( > 200 kHz at −3 dB) is very simple in construction, relatively cheap in production and shows a sensitivity of more than 200 GHz T −1. It is suitable for a magnetic readout system or an integrated magnetic sensor array, especially for high-frequency magnetic heads, navigation applications and for geomagnetic measurements.

Acoustic wave sensors and their technology

In the past two decades, acoustic-wave devices have gained enormous interest for sensor applications. The delay line device, where a transmitting and a receiving interdigital transducer are realized on a (piezoelectric) substrate is the most common structure used. The sensitive part is the surface between the two transducers. By placing the device in the feedback loop of an amplifier, an acoustic-wave oscillator is formed with properties such as inherent high sensitivity, high resolution, high stability and a frequency output signal which is easy to process. A very interesting development is the large amount of wave types now available for sensor applications. Sensors have been published using Rayleigh waves, Lamb waves, Love waves, acoustic plate modes, and surface transverse waves (STW). Each of these wave types have their special advantages and disadvantages with respect to sensitivity, stability, usability in liquids or gases, and fabrication complexity. For the fabrication of the acoustic-wave devices, planar technologies are used, which will be discussed in the paper. Examples will be given of gas sensors, biochemical sensors in liquids, viscosity and density sensing and high-voltage sensing. A comparison of the usability of the different wave types will be presented.

A conditioning circuit for resistive sensors combining frequency and duty-cycle modulation of the same output signal

A signal conditioning circuit based on a relaxation oscillator is presented for use with resistive transducers. Both the frequency and the duty-cycle of the output signal carry independent information coming from a pair of different sensors. Namely, the frequency of the output signal changes linearly with the resistance deviations detected by a Wheatstone bridge, while the duty-cycle is dependent on the resistance of a second sensor.

The current–voltage characteristics of the resistive direct current superconducting quantum interference device

Partly resistive superconducting quantum interference devices (RSQUIDs) are used in noise thermometry in the liquid helium temperature range. Here we analyze one type of RSQUID that has not been thoroughly investigated until now: the direct current biased with two Josephson junctions and a resistive part connected in series with the junctions and closed by a superconducting ring. The resistive shunted model of the Josephson junctions is used for the analysis. Two cases of the RSQUID ring inductance were analyzed: (i) negligibly small and (ii) small but finite inductance. The expressions for the low frequency output signal, the current–voltage (I–V) characteristics, and the current flowing through the resistive part are obtained. In the dependence of the output frequency versus the dc current passed through the resistive part often an offset is observed experimentally. This phenomenon can be explained as an influence of an asymmetry in the critical currents of the junctions.

A new sensor principle based on the reflection of surface acoustic waves

We present a new method for surface acoustic wave (SAW) sensing which overcomes the main disadvantages of the well-known dual-delay-line oscillators, namely the insufficient sensitivity for atmospheric measurements and the strong temperature-dependent drift of the output frequency signal. Our method is based on the reflection of a SAW by a periodic array. SAW reflection occurs at discontinuities of the surface. If these discontinuities vary with the presence of the substance to be detected, the reflection coefficient of the array, and thus the amplitude of the reflected SAW, changes. With this method we have reached a sensitivity of 0.3 ppb for NO 2 with a 370 MHz device on a LiNbO 3 substrate.

Thin-film resistive SQUIDS

Different all thin-film partly resistive superconducting quantum interference devices (RSQUIDs) for noise thermometry in the liquid helium temperature range were designed and investigated. Three different types of RSQUID were realised: (i) dc RSQUID, (ii) rf RSQUID, and (iii) RSQUID with two quantization loops (double RSQUID). Shunted tunnel junctions were used as weak links. The resistive parts have been made as a Cu thin film combined with Nb thin films either as a sandwich or a planar element. The devices using a rf pump have integrated rf coupling coils. Resistances of the resistive parts in the range from 2.69 /spl mu//spl Omega/ to 246 /spl mu//spl Omega/ were obtained. The output signal was /spl ap/50 /spl mu/V for the dc RSQUIDs, up to 80 /spl mu/V for the rf RSQUIDs, and up to 1.2 mV for the double RSQUIDs. The linear dependences of the output signal frequency versus a dc current passed through the resistive part were observed up to 40 MHz. The double RSQUIDS described have a clear advantage in the output signal compared to the other RSQUIDs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optimum Bias Conditions for K-Band Microwave Mixing Using YBaCuO Step-Edge Microbridge Josephson Junction

Characteristics of the K-band microwave mixing using a YBaCuO step-edge microbridge Josephson junction were systematically investigated, and the optimum bias conditions were experimentally determined. A large intermediate frequency (IF) output signal was observed at every midway between the Shapiro steps, and the maximum IF output was obtained between the 0th and 1st steps (0-1) for the local oscillation (LO) power level of I0/Ic=0.2-0.3 (absolute LO power of -49.9 dBm). The maximum conversion efficiency was estimated to be -26.6 dB. Although the IF output (0-1) was observed for a wide range of LO power, it vanished or decreased radically under some peculiar conditions (I0/Ic?0 and ?(I0/Ic)/?ILO?0). These characteristics were qualitatively accounted for by the basic Josephson-mixing theory.

Cavity differential-absolute-pressure transducer with frequency output

A new construction of the differential resonator microwave transducer is considered, having a number of advantages over other transducers: high sensitivity, protection against interference, simple construction, high mechanical strength, etc. The very simple electrical measuring circuit gives, without amplification, a frequency output signal of sufficiently large amplitude. The differential principle makes it possible to exclude a number of errors associated with temperature, vibro-shock loading, etc., playing a large role in absolute pressure transducers used in flying equipment, working in challenging climatic conditions and under severe vibro-shock loading.

A novel highly sensitive magnetic sensor

Abstract A highly sensitive magnetic sensor with a frequency output signal is introduced. The sensor can easily be integrated in an electrical circuit. It consists of a self-starting tunnel-diode oscillator in which the necessary inductance is obtained by an electrically conductive magnetic thin-film core. The resistance and inductance of this thin-film core are changed drastically by a small external magnetic field in the range pT to μT. Hereby one gets a tuned r.f. oscillator whose frequency is determined by a weak external magnetic field applied to the thin-film core (magnetically controlled oscillator (MCO)). This low-noise magnetic-field-to-frequency converter is very simple in construction and shows a sensitivity of more than 100 GHz/T. It is suitable for a magnetic readout system or an integrated magnetic sensor array especially for high-frequency magnetic heads.

An all thin-film resistive DC SQUID-a current-controlled oscillator

An all thin-film resistive SQUID with two Josephson tunnel junctions has been designed, fabricated and studied. As well as the two junctions, this device consists of a low ohmic (1.9*10-6 Omega ) resistive part connected by superconducting leads to both junctions in a loop with very low ( approximately 10-11 H) inductance. A direct current flowing through the resistive part fixes the voltage difference between the two Josephson junctions that are additionally fed by a bias current. The voltage difference is converted into a signal frequency that can be picked up from the SQUID with a conversion factor of ( phi o)-1=483.6 MHz mu V-1, defined only by the electron charge and Planck's constant. An output signal level (peak-to-peak) of about 50 mu V has been obtained. The low frequency range (below 100 kHz) of the output signal frequency has been investigated. The possibilities of considerably extending this frequency range are also discussed.

Integrated smart two-dimensional thermal flow sensor with Seebeck-voltage-to-frequency conversion

A smart sensor has been developed for the measurements of both flow direction and velocity. The sensor uses a thermal principle, which allows complete integration together with electronic circuitry on one chip. A groove is etched to create thermal isolation between the sensor and the chip edge to obtain an essential variable (the flow temperature). On the edge a voltage-to-frequency (V/f) converter is placed as a first step towards a digital output. The V/f converter is able to convert voltages in the range of 1 μV to 1 mV. The frequency output signal is a direct measure for the wind velocity. The presence of a multiplexer enables direction measurement and calibration of the sensor.

Operation of monocrystalline silicon resonator in a measuring circuit

Abstract The monocrystalline silicon fibre sensor shows very high sensitivity and precision. For its operation it is necessary to stimulate oscillation, to transform this oscillation and to register the frequency of the electrical output signal. An electronic circuit, which resolves these aims, has been developed. The operation of the electronic circuit with a functional group ensuring the amplification of the fibre resonator signal is investigated. The conditions of auto-oscillation, phase and amplitude balance are analysed. A version of the realized circuit is discussed.