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Showing papers on "Signal published in 2004"


Patent
04 May 2004
TL;DR: In this article, a method and an apparatus to analyze two measured signals that are modeled as containing desired and undesired portions such as noise, FM and AM modulation are presented, and coefficients relate the two signals according to a model defined in accordance with the present invention.
Abstract: A method and an apparatus to analyze two measured signals that are modeled as containing desired and undesired portions such as noise, FM and AM modulation. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, a transformation is used to evaluate a ratio of the two measured signals in order to find appropriate coefficients. The measured signals are then fed into a signal scrubber which uses the coefficients to remove the unwanted portions. The signal scrubbing is performed in either the time domain or in the frequency domain. The method and apparatus are particularly advantageous to blood oximetry and pulserate measurements. In another embodiment, an estimate of the pulserate is obtained by applying a set of rules to a spectral transform of the scrubbed signal. In another embodiment, an estimate of the pulserate is obtained by transforming the scrubbed signal from a first spectral domain into a second spectral domain. The pulserate is found by identifying the largest spectral peak in the second spectral domain.

1,133 citations


Patent
10 Nov 2004
TL;DR: In this paper, a method for tracking an object, including positioning a radio frequency (RF) driver to radiate an RF driving field toward the object, and fixing to the object a wireless transponder that includes a power coil and at least one sensor coil.
Abstract: A method is provided for tracking an object, including positioning a radio frequency (RF) driver to radiate an RF driving field toward the object, and fixing to the object a wireless transponder that includes a power coil and at least one sensor coil. The method also includes receiving the RF driving field using the power coil and storing electrical energy derived therefrom. A plurality of field generators are driven to generate electromagnetic fields at respective frequencies in a vicinity of the object that induce a voltage drop across the at least one sensor coil. A digital output signal is generated at the wireless transponder indicative of the voltage drop across the sensor coil, and the generation of the digital output signal is powered using the stored electrical energy. The digital output signal is transmitted from the wireless transponder using the power coil, and the transmission of the digital output signal is powered using the stored electrical energy. The digital output signal is received and processed to determine coordinates of the object.

728 citations


Patent
24 Jun 2004
TL;DR: In this article, a method for controlling a direct current motor (30) in one or several fan units (43, 20, 21), each comprising a fan, is presented. But this method is limited to the case of a single motor.
Abstract: The present invention relates to a method for control of a direct current motor (30) in one or several fan units (43, 20, 21), each comprising a fan, which method comprises: generation of a control signal from a first control unit (22) which is external in relation to the said fan unit (43, 20, 21); transmission of the said control signal to the said fan unit (43, 20, 21); reception of the transmitted control signal in the said fan unit (43, 20, 21); interpretation of the said control signal in a second control unit (26) which is arranged in association with the said fan unit (43, 20, 21); and generation, in the said second control unit (26), of a supply signal for the said direct current motor (30), on the basis of the control signal generated by the first control unit (22) and received in the fan unit and on the basis of a supply voltage. According to the invention, the method comprises transmission of the control signal together with the supply voltage over a shared communication link (44), with the control signal being superposed on the supply voltage. The invention also relates to an arrangement for such control. By means of the invention, improved control is obtained of a motor that can be utilized in a ventilated seat in a vehicle.

571 citations


Patent
Noriko Ota1
13 Feb 2004
TL;DR: In this paper, an electronic endoscope system includes an image pickup device provided at a distal end of an insertion portion, an image signal processing device, an auxiliary light source which emits less amount of light than the light emitted from the main light source; and a light guide member.
Abstract: An electronic endoscope system includes an image pickup device provided at a distal end of an insertion portion; an image signal processing device; a main light source; an auxiliary light source which emits less amount of light than the light emitted from the main light source; and a light guide member which guides illumination light emitted from one of the main light source and the auxiliary light source to the distal end of the insertion portion to thereby emit the illumination light from the distal end. When the auxiliary light source emits the illumination light instead of the main light source, the image signal processing device sets the gain of the signal output from the image pickup device to a value higher than the gain of the signal when the main light source emits the illumination light, in order to process the image signal.

567 citations


Journal ArticleDOI
TL;DR: A new approach to coherent detection is demonstrated which achieves the same high sensitivity as homodyne detection but without the need to phase lock the local oscillator laser.
Abstract: A new approach to coherent detection is demonstrated which achieves the same high sensitivity as homodyne detection but without the need to phase lock the local oscillator laser. In addition, 1470 ps/nm of chromatic dispersion is compensated with zero net penalty by electronic domain equalization, a result which has not been achieved before because zero-penalty equalization is not possible after direct detection. The method proposes the use of high-speed digital signal processing technology, and the experimental results are obtained using burst-mode sampling followed by offline signal processing.

504 citations


Journal ArticleDOI
TL;DR: In this paper, a piezoelectric-based built-in diagnostic technique has been developed for monitoring fatigue crack growth in metallic structures, which consists of three major components: diagnostic signal generation, signal processing and damage interpretation.
Abstract: A piezoelectric based built-in diagnostic technique has been developed for monitoring fatigue crack growth in metallic structures. The technique uses diagnostic signals, generated from nearby piezoelectric actuators built into the structures, to detect crack growth. It consists of three major components: diagnostic signal generation, signal processing and damage interpretation. In diagnostic signal generation, appropriate ultrasonic guided Lamb waves were selected for actuators to maximize receiving sensor measurements. In signal processing, methods were developed to select an individual mode for damage detection and maximize signal to noise ratio in recorded sensor signals. Finally, in damage interpretation, a physics based damage index was developed relating sensor measurements to crack growth size. Fatigue tests were performed on laboratory coupons with a notch to verify the proposed technique. The damage index measured from built-in piezoceramics on the coupons showed a good correlation with the actual fatigue crack growth obtained from visual inspection. Furthermore, parametric studies were also performed to characterize the sensitivity of sensor/actuator location for the proposed technique.

476 citations


Patent
30 Apr 2004
TL;DR: In this article, a time domain communications system is proposed where a broadband of time-spaced signals, essentially monocycle-like signals, are derived from applying stepped-in-amplitude signals to a broadband antenna, in this case, a reverse bicone antenna.
Abstract: A time domain communications system wherein a broadband of time-spaced signals, essentially monocycle-like signals, are derived from applying stepped-in-amplitude signals to a broadband antenna, in this case, a reverse bicone antenna. When received, the thus transmitted signals are multiplied by a D.C. replica of each transmitted signal, and thereafter, they are, successively, short time and long time integrated to achieve detection.

431 citations


Patent
15 Jan 2004
TL;DR: An ink jet printer has a vibration detection section to receive ink jetted from the nozzles and output a detection signal having an amplitude corresponding to a vibration generated when the ink lands as mentioned in this paper.
Abstract: An ink jet printer has: a vibration detection section to receive ink jetted from the nozzles and output a detection signal having an amplitude corresponding to a vibration generated when the ink lands; a sampling section to sample an amplitude value of the detection signal by a predetermined sampling clock signal; a storing section to store an amplitude value data of the detection signal sampled by the sampling section; a judging section to judge a jet failure of the nozzles based on the amplitude value data of the detection signal in the storing section; and a control section to control to jet the ink continuously a plurality of times with a jet drive cycle which is set by multiplying a standard drive waveform time of an ink jet signal from the nozzles by an odd number not less than five when detecting a jet failure of the nozzles.

417 citations


Patent
23 Jul 2004
TL;DR: In this article, the authors present a system for protecting and managing electronic data signals that are registered in accordance with a predefined encoding scheme, while allowing access to unregistered data signals.
Abstract: Systems and methods are provided for protecting and managing electronic data signals that are registered in accordance with a predefined encoding scheme, while allowing access to unregistered data signals. In one embodiment a relatively hard-to-remove, easy-to-detect, strong watermark is inserted in a data signal. The data signal is divided into a sequence of blocks, and a digital signature for each block is embedded in the signal via a watermark. The data signal is then stored and distributed on, e.g., a compact disc, a DVD, or the like. When a user attempts to access or use a portion of the data signal, the signal is checked for the presence of a watermark containing the digital signature for the desired portion of the signal. If the watermark is found, the digital signature is extracted and used to verify the authenticity of the desired portion of the signal. If the signature-containing watermark is not found, the signal is checked for the presence of the strong watermark. If the strong watermark is found, further use of the signal is inhibited, as the presence of the strong watermark, in combination with the absence or corruption of the signature-containing watermark, provides evidence that the signal has been improperly modified. If, on the other hand, the strong mark is not found, further use of the data signal can be allowed, as the absence of the strong mark indicates that the data signal was never registered with the signature-containing watermark.

416 citations


Patent
02 Jul 2004
TL;DR: In this article, a portable security alarm system including a movement detecting and signal transmitting member for mounting on or proximate to the object whose movement is to be detected, a signal receiving and alarm generating member for receiving a signal from the moving object and producing a security response, a remote control for actuating and deactuating the signal-receiving and alarm-generating member, an environmental monitoring member for sensing an environmental condition, a visual information gathering member for gathering visual information and providing a signal to the signal receiver and alarm generator, an audio output member, and components
Abstract: A portable security alarm system including a movement detecting and signal transmitting member for mounting on or proximate to the object whose movement is to be detected, a signal receiving and alarm generating member for receiving a signal from the movement detecting and signal transmitting member and producing a security response, a remote control for actuating and deactuating the signal receiving and alarm generating member, an environmental monitoring member for sensing an environmental condition and providing a signal to the signal receiving and alarm generating member, a visual information gathering member for gathering visual information and providing a signal to the signal receiving and alarm generating member, an audio output member for receiving a signal from the signal receiving and alarm generating member and generating an audio output, and components for delivering a security notification to remote recipients. A security network that includes the alarm system is also disclosed. An inertial sensor for alarm system or for activating or deactivating a device is additionally disclosed.

405 citations


Patent
17 Jun 2004
TL;DR: A tracking system for identifying contents of a container includes an electromagnetic identification apparatus that provides an electromagnetic signal indicative of container content data set; a writer for use in encoding the container signal onto the apparatus; a controller for receiving the encoded signal and for storing the signal in a master database storage apparatus; and a reader configured outside the container for communicating with the identification apparatus and for receiving an encoded signal therefrom and corresponding to the container contents data signal set as discussed by the authors.
Abstract: A tracking system for identifying contents of a container includes an electromagnetic identification apparatus that provides an electromagnetic signal indicative of a container content data set; a writer for use in encoding the container signal onto the apparatus; a controller for receiving the encoded signal and for storing the signal in a master database storage apparatus; and a reader configured outside the container for communicating with the electromagnetic identification apparatus and for receiving the encoded signal therefrom and corresponding to the container content data signal set. A system for tracking items in an assembly includes an apparatus for receiving electromagnetic identification tag signals; an apparatus for creating a first tier aggregate signature; an apparatus for storing the signature in a master database; and an apparatus for receiving modifying command signals for creating a second tier aggregate signature corresponding to a modified set of electromagnetic identification tags in an augmented assembly.

Patent
06 Aug 2004
TL;DR: In this paper, the authors describe a color changing device which includes an enclosure at least a portion of which is material which is desired to change color, and an illumination device, such as an LED or collection of LEDs which can illuminate the material.
Abstract: A color-changing device which includes an enclosure at least a portion of which is material which is desired to change color. There is also included an illumination device, such as an LED or collection of LEDs which can illuminate the material. There can also be included a controller which can take some form of input, such as from a network, or a sensor, and can convert that input into a signal to control the illumination. There is also included a method for performing such color change.

Patent
28 Jan 2004
TL;DR: In this article, a distance image sensor for removing the background light and improving the charge transfer efficiency in a device for measuring the distance to an object by measuring the time-of-flight of the light.
Abstract: A distance image sensor for removing the background light and improving the charge transfer efficiency in a device for measuring the distance to an object by measuring the time-of-flight of the light. In a distance image sensor for determining the signals of two charge storage nodes which depend on the delay time of the modulated light, a signal by the background light is received from the third charge storage node or the two charge storage nodes in a period when the modulated light does not exist, and is subtracted from the signal which depends on the delay time of the two charge storage nodes, so as to remove the influence of the background. Also by using a buried diode as a photo-detector, and using an MOS gate as gate means, the charge transfer efficiency improves. The charge transfer efficiency is also improved by using a negative feedback amplifier where a capacitor is disposed between the input and output.

Patent
18 Nov 2004
TL;DR: In this paper, the authors described a device consisting of a port adapted to connect a lead, a pulse generator connected to the port and adapted to provide a neural stimulation signal to the lead, and a signal processing module connected to a port, adapted to receive and process a nerve traffic signal from the lead into a signal indicative of the nerve traffic.
Abstract: Various aspects of the present subject matter provide a device. In various embodiments, the device comprises a port adapted to connect a lead, a pulse generator connected to the port and adapted to provide a neural stimulation signal to the lead, and a signal processing module connected to the port and adapted to receive and process a nerve traffic signal from the lead into a signal indicative of the nerve traffic. The device includes a controller connected to the pulse generator and the signal processing module. The controller is adapted to implement a stimulation protocol to provide the neural stimulation signal with desired neural stimulation parameters based on the signal indicative of the nerve traffic. Other aspects are provided herein.

Patent
16 Nov 2004
TL;DR: In this paper, it has been determined that a sensor placed on a nail, in particular a thumbnail, exhibits the characteristics of having the red and infrared signals correlated when used for pulse oximetry, and the resulting signals correlate to arterial oxygen saturation.
Abstract: A non-invasive optical sensor which uses the motion signal to calculate the physiological characteristic being measured. For pulse oximetry, a least squares or a ratio-of-ratios technique can be applied to the motion signal itself. This is made possible by selecting a site on the patient where variations in motion produce signals of two wavelengths which are sufficiently correlated. In particular, it has been determined that a sensor placed on a nail, in particular a thumbnail, exhibits the characteristics of having the red and infrared signals correlated when used for pulse oximetry, and the resulting signals correlate to arterial oxygen saturation.

Journal ArticleDOI
TL;DR: In this article, a wavelet-based signal processing technique is developed and combined with an active sensing system to produce a near-real-time, online monitoring system for composite structures, where a layer of piezoelectric patches is used to generate an input signal with a specific wavelet waveform and to measure response signals.
Abstract: In this paper a signal processing technique is developed to detect delamination on composite structures. In particular, a wavelet-based signal processing technique is developed and combined with an active sensing system to produce a near-real-time, online monitoring system for composite structures. A layer of piezoelectric patches is used to generate an input signal with a specific wavelet waveform and to measure response signals. Then, the response signals are processed by a wavelet transform to extract damage-sensitive features from the original signals. The applicability of the proposed method to delamination identification has been demonstrated by experimental studies of a composite plate under varying temperature and boundary conditions.

Patent
24 Jun 2004
TL;DR: In this paper, the authors present a method and method for generating an electrical signal for use in biomedical applications, including two timing-interval generators, each optionally driving a multistep sequencer; analog, digital or hybrid means for combining the resulting timed signals into a complex electrical signal; optional filtering means for blocking direct current, removing selected frequency components from the resulting signal, and/or providing voltage step-up if needed.
Abstract: An method and method for generating an electrical signal for use in biomedical applications, including two timing-interval generators, each optionally driving a multistep sequencer; analog, digital or hybrid means for combining the resulting timed signals into a complex electrical signal; optional filtering means for blocking direct current, removing selected frequency components from the resulting signal, and/or providing voltage step-up if needed; and conductive means for coupling the resulting signal to a human or animal body, food, beverage or other liquid, cell or tissue culture, or pharmaceutical material, in order to relieve pain, stimulate healing or growth, enhance the production of specific biochemicals, or devitalize selected types of organisms.

Patent
23 Aug 2004
TL;DR: In this article, a digital light projector that includes a light emitter and a light processor optically coupled to the emitter is used to adaptively and interactively light a scene.
Abstract: Apparatus for adaptively and interactively lighting a scene includes a digital light projector that includes a light emitter and a digital light processor optically coupled to the emitter such that the emitter light is projected onto respective individual fields of view of a field of regard illuminating the scene in accordance with a projector control signal. A camera adjacent to the projector is operative to detect light reflected or projected from the illuminated scene and generate a signal corresponding to the detected light. A signal processor coupled to the projector and the camera is operative to receive the camera signal, process the received signal into a light projector control signal in accordance with an associated set of instructions, and apply the control signal to the light projector such that the light projected onto the respective individual fields of view of the illuminating array is controlled in accordance with the instructions.

Journal ArticleDOI
TL;DR: In this paper, a comparative study of two different electromechanical systems is presented in order to conceive autonomous portable generators capable of harvesting human mechanical energy, and the analytical models described in this paper present a high similarity and a duality in signal levels, adapted load and optimal working frequency, the two latters corresponding to the maximal electrical power generated.
Abstract: This paper presents the comparative study of two different electromechanical systems, in order to conceive autonomous portable generators capable of harvesting human mechanical energy. The first one is an electromagnetic system, made of a magnet in translation within a coil. The second one is a piezoelectric system, which is a PZT ceramic bar, polarised longitudinally, embedded at one end and constrained at the other end. The analytical models described in this paper present a high similarity and a duality in signal levels, adapted load and optimal working frequency, the two latters corresponding to the maximal electrical power generated.

Patent
15 Jan 2004
TL;DR: In this paper, a detector for providing position detection of objects over a sensor with a first and second set of conductor lines forming a grid with a plurality of junctions there between at which the conductor lines do not contact, includes a signal generator providing a signal to at least one conductor line of the first set of lines, and circuitry detecting output arising from one or both of an electromagnetic stylus and one or more fingers when present.
Abstract: A detector for providing position detection of objects over a sensor with a first and second set of conductor lines forming a grid with a plurality of junctions there between at which the conductor lines do not contact, includes a signal generator providing a signal to at least one conductor line of the first set of conductor lines, and circuitry detecting output arising from one or both of an electromagnetic stylus and one or more fingers when present. The output arising from each of the one or more fingers is detected from at least one conductor line of the second set of conductor lines in response to the signal provided to the at least one conductor line of the first set of conductor lines. The circuitry detects positions of one or both the electromagnetic stylus and each of the one or more fingers when present responsive to the output detected.

Journal ArticleDOI
TL;DR: Preliminary studies in which the fast signal is measured in 10 healthy volunteers during finger-tapping, tactile stimulation, and electrical median nerve stimulation are presented, and the suppression of competing signals such as the heartbeat-associated intensity changes is enhanced.

Patent
Chia-Cheng Ho1
25 Aug 2004
TL;DR: In this article, a transceiver with a matching circuit, a duplexer, a circulator, a control unit, and a coupler is presented. And the matching circuit adjusts the matching impedance according to an adjusting signal and generates a reflection signal.
Abstract: The present invention provides a device and method for antenna matching applied in a transceiver. Wherein, the transceiver has a transmission module and a receiving module. The antenna matching device includes a matching circuit, a duplexer, a circulator, a control unit, and a coupler. Wherein, the matching circuit adjusts the matching impedance according to an adjusting signal and generates a reflection signal. The duplexer receives the reflection signal and a receiving signal and respectively sent the received two signals to the control unit and the receiving module according to their frequencies. The control unit, according to the reflection signal, estimates the adjusting signal for adjusting the matching circuit to an optimal state of the load impedance of the matching antenna, such that the antenna gain may is maximized, and a best efficiency is obtained no matter during receiving or transmission.

Journal ArticleDOI
TL;DR: This note presents an alternative stability analysis for a modified ANF that permits the presence of harmonics in the incoming signal and this stability analysis is simpler and alleviates the problem complexity even in the case of pure sinusoidal signal.
Abstract: Online frequency estimation of a pure sinusoidal signal is a classical problem that has many practical applications. Recently an ANF with global convergence property has been developed for this purpose. There exist some practical applications in which signals are not pure sinusoidal and contain harmonics. Therefore, online frequency estimation of periodic but not necessarily sinusoidal signals espoused by such applications becomes quite important. This note presents an alternative stability analysis for a modified ANF that permits the presence of harmonics in the incoming signal. Also, this stability analysis is simpler and alleviates the problem complexity even in the case of pure sinusoidal signal. Simulation results confirm theoretical issues.

Patent
15 Apr 2004
TL;DR: An apparatus for measuring a bio signal including an apparatus that is insertable into an ear to be in close contact with an internal surface of the ear, the bio signal measurement unit having a photo plethysmography (PPG) measurement module, and an output unit for displaying the bio information generated from the control unit as mentioned in this paper.
Abstract: An apparatus for measuring a bio signal including a bio signal measurement unit, which is insertable into an ear to be in close contact with an internal surface of the ear, the bio signal measurement unit having a photo plethysmography (PPG) measurement module for radiating light of different wavelengths onto the internal surface of the ear, detecting light transmitted through the ear, and outputting a PPG signal including bio information, a control unit having a PPG signal processor for generating the bio information using the PPG signal measured by the PPG measurement module, and an output unit for displaying the bio information generated from the control unit.

Patent
02 Nov 2004
TL;DR: In this article, the authors propose to use location definitions associated with the received unique ID to recall saved devices states, commands sets, macros and even to dynamically generate commands based on the location information.
Abstract: A controlling device such as a remote control has programming for transmitting a signal response to a plurality of control environments, each environment including a signaling device. Each signaling device in receipt of the signal request sends a signal response having a unique ID which is chosen to be characteristically attenuated by the surroundings of the environment. Because the controlling device can only be in one environment at a given time, and given the attenuation characteristics of the signal response from each signaling device, only one signal response will be received by the controlling device in each environment. Location definitions associated with the received unique ID may be used by programming in the controlling device to recall saved devices states, commands sets, macros, and even to dynamically generate commands based on the location information.

Patent
30 Aug 2004
TL;DR: A physiological parameter tracking system has a reference parameter calculator configured to provide an appropriate reference parameter responsive to a physiological signal input as discussed by the authors, and a physiological measurement output is a physiological parameter derived from the physiological signal inputs during a favorable condition and an estimate of the physiological parameter according to the reference parameter during an unfavorable condition.
Abstract: A physiological parameter tracking system has a reference parameter calculator configured to provide a reference parameter responsive to a physiological signal input. A physiological measurement output is a physiological parameter derived from the physiological signal input during a favorable condition and an estimate of the physiological parameter according to the reference parameter during an unfavorable condition.

Journal ArticleDOI
TL;DR: A differential absorption lidar has been built to measure CO2 concentration in the atmosphere, using a pulsed single-frequency Ho:Tm:YLF laser at a 2.05-microm wavelength and a coherent heterodyne receiver to achieve sensitive detection.
Abstract: A differential absorption lidar has been built to measure CO2 concentration in the atmosphere The transmitter is a pulsed single-frequency Ho:Tm:YLF laser at a 205-μm wavelength A coherent heterodyne receiver was used to achieve sensitive detection, with the additional capability for wind profiling by a Doppler technique Signal processing includes an algorithm for power measurement of a heterodyne signal Results show a precision of the CO2 concentration measurement of 1%–2% 1σ standard deviation over column lengths ranging from 12 to 28 km by an average of 1000 pulse pairs A preliminary assessment of instrument sensitivity was made with an 8-h-long measurement set, along with correlative measurements with an in situ sensor, to determine that a CO2 trend could be detected

Patent
Paul W. Dent1, Sven Mattisson1
23 Apr 2004
TL;DR: In this paper, a transceiver includes a transmitter and a homodyne receiver, wherein the receiver is used to process both antenna-received and antenna-reflected signals, and an adjustable matching network disposed in the transmit signal path is adjusted based on the characterization to reduce the mismatch.
Abstract: A transceiver includes a transmitter and a homodyne receiver, wherein the receiver is used to process both antenna-received and antenna-reflected signals. Thus, during a receive mode, for example, the receiver downconverts antenna-received signals to baseband signals, which are then processed to recover receive signal information. Then, during a transmit mode for example, antenna-reflected transmit signals are fed back to the receiver, which is retuned to the desired transmit frequency, and thus downconverts the reflected transmit signals to baseband signals. These baseband signals are then processed to obtain a characterization of impedance mismatch between the transceiver's transmitter and the associated antenna. An adjustable matching network disposed in the transmit signal path thus may be adjusted based on the characterization to reduce the mismatch. Such configurations may be used with either single-band or multi-band embodiments of the transceiver, and the transceiver may be used in both TDMA and CDMA communication systems.

Patent
29 Oct 2004
TL;DR: In this article, a patient physiological parameter monitoring apparatus for a subject includes a sensor assembly having at least one responsive element that produces a first signal upon detection of a change in temperature.
Abstract: A patient physiological parameter monitoring apparatus for a subject includes a sensor assembly having at least one responsive element that produces a first signal upon detection of a change in temperature. The assembly also includes a conveter for converting the first signal into an electrical signal, and a transmitter for wirelessly transmitting converted electrical signals upon demand based upon receipt of a transmitted signal from an interrogation device. Preferably, at least a portion of the sensor assembly is disposable to permit single use or single subject use and can be further used to track location information of medical equipment in addition to subjects.

Journal ArticleDOI
TL;DR: A tutorial review of complex signal processing for wireless applications emphasizing a graphical and pictorial description rather than an equation-based approach is presented.
Abstract: Wireless systems often make use of the quadrature relationship between pairs of signals to effectively cancel out-of-band and interfering in-band signal components. The understanding of these systems is often simplified by considering both the signals and system transfer functions as "complex" quantities. The complex approach is especially useful in highly integrated multistandard receivers where the use of narrow-band fixed-coefficient filters at the RF and high IF must be minimized. This paper first presents a tutorial review of complex signal processing for wireless applications. The review emphasizes a graphical and pictorial description rather than an equation-based approach. Next, a number of classical modulation architectures are described using this formulation. Finally, more recent developments such as complex filters, image-reject mixers, low-IF receivers, and oversampling analog-digital converters are discussed.