Abstract: Devices and methods related to unpowered switching module. A switching module can include a first input terminal, a second input terminal, and an output terminal. The output terminal can be configured to output a radio-frequency (RF) component of an input signal received on the first input terminal or the second input terminal in response to the input signal including a positive direct-current (DC) voltage.

Abstract: An apparatus includes a photonic integrated circuit having an optical phased array, where the optical phased array includes multiple unit cells. Each unit cell includes multiple antenna elements configured to transmit or receive optical signals, where a first subset of the antenna elements is oriented in a first direction and a second subset of the antenna elements is oriented in a second direction opposite the first direction. Each unit cell also includes multiple signal pathways configured to transport the optical signals to or from the antenna elements, where at least some of the signal pathways have an “H” configuration. Each unit cell further includes multiple phase modulators configured to modify phases of the optical signals being transported through the signal pathways.

Abstract: Multi-mode broadband low noise amplifiers (LNAs) are disclosed herein. In certain embodiments, an LNA includes a first amplification stage and a second amplification stage having a lower gain than the first amplification stage. The LNA is operable in a plurality of operating modes including a first mode in which the first amplification stage and the second amplification stage operate in a cascade to amplify a radio frequency (RF) receive signal, and a second mode in which the first amplification stage amplifies the RF receive signal and the second amplification stage is bypassed.

Abstract: In one embodiment, an apparatus includes: a low noise amplifier (LNA) to receive and amplify a radio frequency (RF) signal, the LNA having a first controllable gain; a mixer to downconvert the RF signal to a second frequency signal; a programmable gain amplifier (PGA) coupled to the mixer to amplify the second frequency signal, the PGA having a second controllable gain; a digitizer to digitize the second frequency signal to a digitized signal; a demodulator coupled to the digitizer to demodulate the digitized signal; an automatic gain control (AGC) circuit to control one or more of the first controllable gain and the second controllable gain; and an AGC settling circuit to cause the demodulator to begin operation in response to determining that the AGC circuit has settled.

Abstract: A transmitting and receiving device having a module (GSZ) with a configurable HF high-power amplifier (HPA) that includes a main power amplifier (DM) with a main amplifier core and at least one peak power amplifier (DP1) having an auxiliary amplifier core. A switching element connected to inputs of the main power amplifier and the at least one peak power amplifier is connected to a digital input signal divider (ET) having a plurality of outputs and an output combiner (C) is connected to outputs of the amplifier cores for the main power amplifier and the at least one peak power amplifier. A multi-harmonic transformation line (LAH) is connected at the amplifier core output of the main power amplifier and at the amplifier core output of the at least one peak power amplifier, and a circulator (Z1) is connected to the output of the output combiner or an impedance converter (AN1).

Abstract: Systems and methods for managing a network are disclosed. One method can comprise determining signal information relating to a first network device such as an access point. The signal information may be associated with signal characteristics such as a radio frequency signal strength over a communication channel. An attenuation value for one or more receiving paths of the first network device may be determined using the signal information. The one or more receiving paths of the first network device may be attenuated based on the determined attenuation value. A transmission power of the first network device may be configured based on the determined attenuation value.

Abstract: According to the present disclosure, there is provided a signal generation apparatus including: a base band module (11); a DA converter that converts digital base band signals into modulation signals corresponding to a plurality of cells; an RF converter (20) to which the modulation signals corresponding to the plurality of cells are input, and which outputs an RF signal obtained by frequency-converting the modulation signal; and an RF converter control unit (31), in which the RF converter control unit controls the base band module to reduce a power value of a digital base band signal corresponding to a predetermined cell, among the digital base band signals corresponding to the plurality of cells in the base band module so that an input level of the modulation signal input to the RF converter is equal to or lower than an input limit value of the RF converter.

Abstract: A high frequency (HF) radio configured to process an incoming call from another HF radio, the HF radio comprising: an adjustable-bandwidth tunable bandpass filter configured to provide HF signals that are within an adjustable-bandwidth Staring Frequency Band (SFB), being a subset of a HF band, the HF signals including analog calling signals that are indicative of incoming calls; a receive path configured to convert the analog calling signals to digital calling signals; a plurality of receivers configured to monitor assigned Automatic Link Establishment (ALE) channels within the SFB for the digital calling signals; and a controller configured to: establish a communication link between the HF radio and the another HF radio, in response to a given receiver of the receivers decoding a digital calling signal that is indicative of the incoming call; and select the SFB and the assigned ALE channels, based on an indication of ionospheric propagation conditions.

Abstract: A method and apparatus for detecting RF power comprising an input port configured to receive a high-power RF signal, at least one diamond chip attenuator, coupled to the input port, configured to attenuate the high-power RF signal, and an RF detector integrated circuit, coupled to the at least one diamond chip attenuator, configured to convert the attenuated RF signal into an output indicium representing a power level of the high-powered RF signal.

Abstract: Methods and devices for limiting the power level of low noise amplifiers (LNA) implemented in radio frequency (RF) receiver front-ends. The described methods are applicable to bypass, low and high gain modes of the LNA. According to the described methods, the decoder allows the signal to be clamped before or after being attenuated. The benefit of such methods is to improve large signal performances (e.g. IIP3, P1dB) of the RF receiver front-end, while still meeting the clamping requirements, or improve (lower) clamped output power, while still meeting large signal performances (e.g. IIP3, P1dB).

Abstract: A receiver is provided. The receiver includes a first signal path and a second signal path coupled between an input terminal and an output terminal. A first transistor in the first signal path has a control electrode coupled to a voltage source terminal and a first current electrode coupled at the input terminal. The first transistor is configured and arranged for receiving a first signal at the first input terminal having a voltage exceeding a voltage rating of the first transistor. A second transistor in the first signal path has a first current electrode coupled to a second current electrode of the first transistor and a control electrode coupled to receive a first control signal. The second transistor is configured to form an open circuit in the first signal path when the first control signal is at a first state. A first resistor network in the second signal path is configured and arranged for attenuating the first signal.

Abstract: A multi-tone multi-band tunable millimeter-wave synthesizer is provided. In some embodiments, the multi-tone multi-band tunable millimeter-wave synthesizer is configured to simultaneously generate multiple frequency tones for space-borne beacon transmitter for atmospheric radio wave propagation studies. The apparatus includes a comb generator, which puts out evenly spaced harmonic frequencies of the input signal, which are coherent, tunable, and the number of tones or combs is scalable over a wide range of frequencies. These harmonics or tones are amplified to the power level needed for radio wave propagation studies. The amplified signals are transmitted as beacon signals from a satellite to a ground receiving station.

Abstract: A receiving apparatus includes a variable gain unit to change between a first gain and a smaller second gain, and to amplify a received signal to obtain an amplified signal; a comparator to compare a power of the amplified signal with a reference value; and a controller to set a gain to the first gain while in a standby state, to reset a gain to a third gain between the first and second gains if in a standby state the power of the received signal is larger than the reference value, and then to set a gain to the first gain and return to the standby state if the power is equal to or lower than the reference value, or if not, to a fourth gain between the first and third gains.

Abstract: A device includes circuitry configured to receive a signal burst, apply one or more filters to the signal burst based to achieve a predetermined image rejection rate, apply at least one harmonic rejection mode to the signal burst, and amplify the signal burst based on a gain partitioning determination.

Abstract: A RF tuner is described for handling RF signals in a broad frequency range and a broad power range while maintaining high linearity and tolerating high power blockers. A continuous feedback loop comprising a substantially linear LNA and a radio frequency RSSI can adjust the power of the RF signal on the RF side. On the IF side, a continuous feedback loop comprising a substantially linear, variable gain transconductor and a RSSI can adjust the power of the IF signal.

Abstract: Radio Frequency (RF) signal conditioning circuitry, which includes RF detection circuitry and RF attenuation circuitry is disclosed. The RF detection circuitry receives and detects an RF sample signal to provide an RF detection signal. The RF attenuation circuitry has an attenuation circuitry input, and receives and attenuates the RF sample signal via the attenuation circuitry input to provide an attenuated RF signal. The RF attenuation circuitry presents an attenuation circuitry input impedance at the attenuation circuitry input. The attenuated RF signal and the RF detection signal are provided concurrently.

Abstract: A network isolation system may include a network interface, a power level detector, and a processor. The network interface may be configured to receive signals over channels, where the signals include at least one local network signal, e.g. a signal originating on a local network, and at least one non-local network signal, e.g. a signal originating on a non-local network. The power level detector may be configured to determine attenuation values of the received signals. The signal processor may be configured to discard a first signal and reallocate the channel over which the first signal was received, without processing the first signal in a frequency domain, when the attenuation value of the first signal fails to satisfy a signal threshold. In one or more implementations, the signal threshold may differentiate the local network signal from the non-local network signal based at least in part on the determined attenuation values.

Abstract: A system and method employ an arbiter-based automatic gain control (AGC) for managing a series of power adjustment circuits, such as amplifiers and/or attenuators. A central arbiter is employed for managing each stage of a series of power adjustment circuits, rather than each stage solely managing itself via a localized control loop. In one embodiment, a system comprises a series of gain stages each having at least one power adjustment circuit, such as at least one attenuator or amplifier. A power detector may be implemented to detect the power level of the output signal of each gain stage, and communicate information about the detected power levels for each stage to a central arbiter. Based at least in part on the received information, the arbiter controls each of the gain stages in a coordinated fashion.

Abstract: A circuit tuneable between first and second frequencies comprising gain control circuitry operable to control the gain of the circuit between the first and second frequencies, the gain control circuitry comprising a resistor network having: at least two resistor lines arranged in parallel, each resistor line comprising one or more resistors; and for each resistor line, a switch operable to select or deselect the corresponding resistor line; the resistor lines and switches being arranged such that the net resistance of the resistor network is the parallel sum of each of the selected resistor lines; and logic circuitry configured to control said switches so as to minimize the variation in gain of the circuit between the first and second frequencies.

Abstract: An electronic circuit arrangement for receiving low-frequency electromagnetic waves is proposed, having an inductor (L) acting as an antenna for generating a received signal, having a first receiver (2), connected to the inductor (L), for decoding a first component of the received signal and having a second receiver (3), connected to the inductor (L), for decoding a second component of the received signal, wherein at least the second receiver (3) is connected to the inductor (L) via an attenuator element (4) having adjustable attenuation, wherein at least one adjustment signal generation circuit (5, 6) is provided for generating an adjustment signal corresponding to a voltage of the received signal which is fed to the attenuator element (4) for adjusting the attenuation.

Abstract: An RFID transponder having an analog front end receiver having an attenuator coupled to receive an RF-signal from an antenna and to attenuate the RF-signal, an amplifier having a fixed amplifier gain and being coupled to receive and to amplify the attenuated RF-signal and a control unit coupled to control a gain of the attenuator, wherein the control unit is configured to control the attenuator gain in response to a level of the amplified RF-signal, the control unit is configured to have a plurality of predetermined states causing the attenuator to increase (step-up) or to decrease (step-down), its gain by a predefined step size.

Abstract: An apparatus includes an input terminal to receive a radio frequency (RF) signal and to communicate the RF signal to a low noise amplifier (LNA) via an input signal path, and a capacitor attenuator coupled to the input terminal to attenuate the RF signal by a controllable amount and having a first portion controllable to include a used part configured on the input signal path and an unused part coupled between the input signal path and an AC reference node, and a second portion coupled between the LNA and the AC reference node.

Abstract: Disclosed are circuits, techniques and methods for implementing an attenuator in a signal transmission path. In one particular implementation, an attenuation may be adjusted based, at least in part, on a control signal. In another implementation, such an attenuation may be adjusted in coarse increments by varying one or more gate voltages applied one or more transistors. In yet another implementation, adjusting said attenuation in fine increments by varying a bias voltage applied to at least one level shifter.

Abstract: A high dynamic range precision variable amplitude controller includes a gain portion configured to apply a controllable amount of amplitude adjustment to an input signal. The gain portion includes two or more amplification stages each amplification stage having branches that are cross-coupled with branches of the other amplification stage. A control portion controls the current supply to the two or more amplification stages to control the amount of amplitude adjustment by the gain portion. The amplitude controller also includes a load portion that provides balanced impedances to the cross-coupled branches of the amplification stages throughout the amplitude control range.

Abstract: A semiconductor device is provided, including an input attenuator configured to receive an antenna signal and to output a first attenuated signal, the first attenuated signal corresponding to the antenna signal attenuated by a first attenuation factor, the input attenuator being further configured to receive a control signal and to select one of a plurality of predetermined attenuation factors as said first attenuation factor depending on the control signal; an analog to digital converter configured to generate an intermediate signal by digitizing the first attenuated signal; and a digital attenuator configured to receive the intermediate signal and to output a second attenuated signal, the second attenuated signal corresponding to the intermediate signal attenuated by a second attenuation factor, the second attenuation factor being set so as to compensate a gain quantization error of the control signal.

Abstract: A frequency translating analog-to-digital converter for receiving an analog band-pass signal is described. The analog-to-digital converter comprises an adder/input block for receiving the analog band-pass signal and an analog band-pass feedback signal, thereby forming an analog band-pass error signal. The analog-to-digital converter has at least one analog mixer for mixing and down converting the analog band-pass error signal and thus generating a down-converted analog error signal and at least one quantization path for generating at least one digital signal.

Abstract: The invention discloses a method (700) for finding differences in path loss between a plurality of RF paths between a first (120, 130) and a second (120, 130) transceiver in a wireless communications system (100). During defined 5 intervals of time (SACCH1-SACCH4), only one RF path is used to transmit from one of said transceivers to the other of said transceivers, and the receiving transceiver measures the strength of the signal received during at least a number of said intervals, thus making it possible to compare signal strength and thereby path loss between different RF paths, which in turn 10 makes it possible to find imperfections in one or more of said RF paths.

Abstract: An electronic circuit arrangement for receiving low-frequency electromagnetic waves is proposed, having an inductor (L) acting as an antenna for generating a received signal, having a first receiver (2), connected to the inductor (L), for decoding a first component of the received signal and having a second receiver (3), connected to the inductor (L), for decoding a second component of the received signal, wherein at least the second receiver (3) is connected to the inductor (L) via an attenuator element (4) having adjustable attenuation, wherein at least one adjustment signal generation circuit (5, 6) is provided for generating an adjustment signal corresponding to a voltage of the received signal which is fed to the attenuator element (4) for adjusting the attenuation.

Abstract: Voltage controlled variable attenuators are described that are configured to be coupled to a transmission path to furnish variable attenuation of a signal, such as a radio frequency signal. In one or more implementations, the voltage controlled variable attenuator includes at least one transistor. The transistor has an open configuration for at least substantially preventing the flow of current through the transistor, and a closed configuration for at least partially allowing the flow of current through the transistor. The variable attenuator also includes a resistive component coupled to the transistor, and configured to couple to the transmission path. The resistive component is configured to at least partially mitigate non-linear effect when the transistor transitions from the open configuration to the closed configuration.

Abstract: Embodiments related to analog front-ends for wireless and wired are described and depicted.

Abstract: An electronic circuit arrangement for receiving low-frequency electromagnetic waves is proposed, having an inductor (L) acting as an antenna for generating a received signal, having a first receiver (2), connected to the inductor (L), for decoding a first component of the received signal and having a second receiver (3), connected to the inductor (L), for decoding a second component of the received signal, wherein at least the second receiver (3) is connected to the inductor (L) via an attenuator element (4) having adjustable attenuation, wherein at least one adjustment signal generation circuit (5, 6) is provided for generating an adjustment signal corresponding to a voltage of the received signal which is fed to the attenuator element (4) for adjusting the attenuation.

Abstract: Automatic Gain Control AGC circuit comprising a PIN-diode attenuator having an input and an output and a control circuit connected to the attenuator so as to read a signal at the attenuator output. The control circuit is configured to supply a feedback control signal to the attenuator based on an error signal between the signal read at the attenuator output and a reference signal, so as to modulate an attenuation level of said attenuator and maintain a substantially constant power level at the attenuator output. The control circuit particularly comprises at least a resistor and a capacitor which define a time constant of the AGC circuit, so that the AGC circuit features a main pole depending on such time constant and on a voltage of the feedback control signal. The control circuit also comprises a variable gain block, which receives the feedback control signal and which is configured to modulate the main pole proportionally to a variable gain (G) of the gain block.

Abstract: A signal conditioning device, and method thereof, that can be used to maintain an amount of signal RF level adjustment, which is applied to an input, independently of the availability of the power supplied to the device. In one embodiment, the signal condition device comprises an attenuating circuit, which can have a variable attenuator and a non-volatile attenuator. The variable attenuator is configured to provide a primary amount of signal RF level adjustment in a power-on state, and the non-volatile attenuator is configured to store as a secondary amount the primary amount of the signal RF level adjustment. The non-volatile attenuator is likewise configured so that the secondary amount can be applied when the signal conditioning device enters into a power-off state so as to modify the RF level of the input in order to maintain a relative strength of the transmission at a remote device.

Abstract: A receiver has an input stage (LNA) that comprises, in a signal direction from an input (SI) to an output (SO), an input transistor (Q1) and an attenuator (D1, D2, R7-R12, C2-C5). The attenuator provides an attenuation that depends on a control signal (VDC). The input stage comprises a transistor-biasing circuit (R2) that biases the input transistor in dependence on the control signal.

Abstract: A communication device includes a transmission signal processing unit, a driver amplifier coupled to the transmission signal processing unit, a selector coupled to the driver amplifier, a first attenuator coupled to the selector and an output portion of the communication device, a second attenuator coupled to the selector and the output portion of the communication device, and a controller coupled to the selector and the driver amplifier to switch between the first attenuator and the second attenuator based on a notification signal.

Abstract: A multi-stage Doherty power amplifier (“PA”) circuit which achieves superior efficiency over broadband range of frequencies is disclosed. Conventional multi-stage amplifiers may offer potential for efficiency enhancement but may suffer from cost penalties and severe bandwidth limitation in practice. Embodiments may employ a driver in the peaking arm which is biased in class C which may alleviate such limitations. The amplifier topology and associated circuitry described in embodiments may achieve high efficiency, smooth PA gain, and enhanced phase characteristics over a 15% fractional bandwidth with reduced costs.

Abstract: Provided is a transceiver using a millimeter-wave (MM-wave). The transceiver determines output power of a transmitting signal according to a receiving signal of a receiving end in the same device so that a possible loss value occurring in the air may be predicted. By doing so, performance of a whole link budget may be enhanced, and the transmitting signal may be rapidly controlled.

Abstract: Techniques for performing automatic gain control (AGC) at a terminal in a wireless communication network are described. In an aspect, the terminal may use different receiver gain settings to receive different types of signals in different time intervals. The terminal may determine a receiver gain setting for each signal type and may use the receiver gain setting to receive signals of that signal type. In another aspect, the terminal may determine a receiver gain setting for a future time interval based on received power levels for peer terminals expected to transmit in that time interval. The terminal may measure received power levels of signals received from a plurality of terminals. The terminal may determine a set of terminals expected to transmit in the future time interval and may determine the receiver gain setting for the future time interval based on the measured received power levels for the set of terminals.

Abstract: A wireless communication device may be configured to transmit and receive data through a physical device, such as a cable. Relatively higher transmit radio frequency (RF) signals from the wireless communication device may be shifted to a relatively lower frequency, thereby enabling the relatively lower frequency signals to be carried by the physical device. Similarly, relatively lower frequency signals from the physical device may be shifted to relatively higher frequencies, thereby enabling the wireless communication device to receive the signals from the physical device. In one embodiment, the frequency of the RF signals may be between 2.3 and 2.7 GHz and the frequency of the relatively lower frequency shifted signals may be between 900 and 1100 MHz.

Abstract: The attenuation characteristics of an attenuator largely changes depending on the frequency of an input signal. Accordingly, a difference between the amounts of attenuation of gains of each two attenuators included in a communication device is not constant. In communications using the wireless USB, the difference needs to be in a range of 2 dB±1 dB. Thus, the communication device does not meet the standards of the wireless USB unless the difference between the amounts of attenuation of the attenuators is adjusted. In this regard, provided is a communication device including first and second attenuators that attenuate a signal. The second attenuator is provided with a regulator circuit that adjusts a relation between an amount of attenuation of the signal through the first attenuator and an amount of attenuation of the signal through the second attenuator.

Abstract: Transceivers with multiple gain stages that include open loop and closed loop amplifiers are subject to differential non-linearity (DNL) errors in their total gain versus gain index curve due to the gain step variability of the open loop amplifiers. The initial and time varying DNL can be reduced by a control loop that uses the relative gain step precision of the closed loop amplifiers and of passive attenuators to establish a control loop to reduce the DNL of the total gain.

Abstract: A variable attenuator and method of attenuating a signal is presented. The variable attenuator contains an input that receives an input signal to be attenuated. A voltage divider between a resistor and parallel MOSFETs provides the attenuated input signal. The MOSFETs have different sizes and have gates that are connected to a control signal through different resistances such that the larger the MOSFET, the larger the resistance. The control signal is dependent on the output of the attenuator. The arrangement extends the linearity of the attenuation over a wide voltage range of the control signal and decreases the intermodulation distortion of the attenuator.

Abstract: A radio frequency detection system is provided that includes at least two radio frequency detection devices, which have an antenna each with a detection range for a radio frequency identification and detect the radio frequency identification information provided in the detection range. The radio frequency detection system is designed to attenuate a detection range of a detecting radio frequency detection device in the detection range of the at least one other radio frequency detection device by means of a compensation member such that the radio frequency identification cannot be detected by the detecting radio frequency detection device in the detection area of the at least one other radio frequency detection device.

Abstract: A wireless communication apparatus for demodulating modulated information which is transmitted from a wireless tag so as to read out the modulated information, includes: an antenna which transmits a transmission signal to the wireless tag and receives a signal transmitted from the wireless tag as a reception signal; a demodulator which demodulates the reception signal to output a demodulated signal; a signal output unit which outputs a proportional signal proportional to the transmission signal; and a controller which calculates the proportional signal and the demodulated signal to output an calculated signal, and calculates the calculated signal and the reception signal.

Abstract: An identification information reader includes an antenna commonly used for transmission of a radio wave to a radio frequency identification tag and reception of a radio wave that has been modulated with at least identification information and transmitted from a radio frequency identification tag, a transmitter which outputs a radio wave to be transmitted from the antenna, a receiver which demodulates a radio wave received by the antenna to acquire at least the identification information, a directional coupler which is connected between the transmitter and the receiver, guides the radio wave output from the transmitter to the antenna and guides the radio wave received by the antenna to the receiver, and an attenuator which is connected between the antenna and the directional coupler and attenuates the radio wave guided to the receiver to reduce saturation of the receiver due to an increase in voltage standing wave ratio of the antenna.

Abstract: A radio frequency receiver includes a receiver circuit for processing RF signals, an antenna to receive millimeter wave RF signals, and an attenuator circuit, coupled between the receiver circuit and antenna. In one embodiment, the attenuator circuit may be used to determine a signal strength of the millimeter wave RF signals, compare this signal strength to a first threshold value. If the signal strength is above the first threshold value, a level of attenuation applied to the millimeter wave RF signals may then be increased.

Abstract: A system for providing automatic gain control (AGC) comprises a signal path with an RF input, a plurality of power detectors in communication with the signal path, each of the power detectors operable to measure a total broadband power level of a signal in the signal path, each of the power detectors positioned to monitor a point in the signal path corresponding to a change in signal bandwidth, a control system operable to receive from each of the power detectors information associated with the power level and to adjust attenuation in the signal path in response to the information to achieve desired gain control.

Abstract: The present invention is directed to systems and methods for providing an AGC circuit for maintaining a constant output power level from an amplifier. More specifically, the AGC circuit includes a circuitry for determining whether an input signal is a QAM or a CW signal. A QAM/CW gain switch is then controlled depending upon the input signal. Depending upon the mode of the QAM/CW gain switch, the AGC circuit either attenuates the power level of the signal or bypasses the signal. The bypassed or attenuated signal is then compared to a reference signal so that the AGC circuit produces an adjusting voltage accordingly. The amplifier finally receives the adjusting voltage and attenuates the output power level of the signal.

Abstract: Systems for suppressing image noise are provided. In this regard, one embodiment includes a system for suppressing image noise comprising a low noise amplifier (LNA) configured to amplify a received RF signal, an RF variable gain attenuator with an image rejection filter with programmable bandwidth configured to suppress image noise and image interference, and an RF mixer configured to perform frequency translation.

Abstract: A received analog spread-spectrum signal is selectively attenuated prior to digitization, where the amount of attenuation is based on the amplitude of the digitized signal before the digitized signal is filtered to compensate for interference that may exist in the received signal. By selectively attenuating the signal only when the digitized signal is relatively large, the receiver can be implemented using a relatively small analog-to-digital converter (ADC) than would otherwise be the case for a particular signal processing application. Taking advantage of the signal-concentration characteristics of spread-spectrum receivers, embodiments of the present invention can be designed to operate with signal having negative signal-to-noise ratios at the A/D conversion step.