499 results about "Automatic gain controller" patented technology

A networked digital security system is disclosed that preferably includes a centralized administrator web server coupled via a communication network such as the Internet to a plurality of customer servers and a plurality of customer work stations. The centralized web server advantageously provides a point of control and management of the networked digital security system. The customer servers and customer work stations are preferably located at the customer's monitored sites. The customer servers are coupled to one or more intelligent camera units, which are preferably fully integrated intelligent units that gather, analyze, and transmit video, audio, and associated detected alarm event information to their associated customer server and the administrator web server. The camera units also include an intelligent automatic gain controller, an encoder buffer controller, and a network bandwidth priority controller. The system supports several compression algorithm standards.

A communications apparatus used in a wireless full duplex system is disclosed. The communications apparatus includes a receiver chain connected to an antenna and an interference cancelling chain. One or more cancellation signals generated by the interference cancelling chain are fed back to the receiver chain prior to the first baseband amplifier which uses the first automatic gain control and the second automatic gain controller. Other methods and systems also are disclosed.

A wireless distribution system includes a number of remote units distributed in a coverage area to receive wireless signals and to provide the signals through the distribution system to input ports of a node where the signals are combined, a number of input power monitors operatively connected to one or more of the input ports to determine power levels of signals received at the input ports, variable gain controllers to control signals received at some or all of the input ports, a node to combine a plurality of signals from the plurality of input ports, and a controller to provide control signals to control one or more of the variable gain controllers.

A networked digital security system is disclosed that preferably includes a centralized administrator web server coupled via a communication network such as the Internet to a plurality of customer servers and-a plurality of customer work stations. The centralized web server advantageously provides a point of control and management of the networked digital security system. The customer servers and customer work stations are preferably located at the customer's monitored sites. The customer servers are coupled to one or more intelligent camera units, which are preferably fully integrated intelligent units that gather, analyze, and transmit video, audio, and associated detected alarm event information to their associated customer server and the administrator web server. The camera units also include an intelligent automatic gain controller, an encoder buffer controller, and a network bandwidth priority controller. The system supports several compression algorithm standards.

A communications apparatus used in a wireless full duplex system is disclosed. The communications apparatus includes a receiver chain connected to an antenna and an interference cancelling chain. One or more cancellation signals generated by the interference cancelling chain are fed back to the receiver chain prior to the first baseband amplifier which uses the first automatic gain control and the second automatic gain controller. Other methods and systems also are disclosed.

A digital automatic gain control (AGC) system comprising an AGC amplifier configured to scale an input signal by a scale factor, and configured to generate an analog scaled input signal. An analog-to-digital (A / D) converter is configured to sample and convert the analog scaled input signal into a digital scaled input signal. The frequency down converted digital scaled input signal is processed by a power level detector circuit to detect its power level. The logarithmic comparison circuit (LCC) is configured to compare the detected power level of the digital scaled input signal to a predetermined reference signal and configured to generate a digital error signal. Finally, an error processing circuit is configured to process the digital error signal and configured to determine the scale factor of the AGC circuit. The test results show that for any applicable QAM constellation the AGC circuit of the present invention can control the broadest fades (or decreases) in the power level of the input signal with an accuracy up to 200 dB / per second.

A GPS receiver circuit (300) for reducing insertion loss. The receiver circuit (300) includes a switch (304) for diverting input signals between a filtered pathway (312) and a short circuit pathway (310) to an amplifier (314). The amplifier (314) output feeds an automatic gain controller (316) that senses a noise level in the output of the amplifier (314) and adjusts a gain of the amplifier (314) in response to the noise level. The receiver circuit (300) also includes a threshold detector (306) with an input coupled to the output of the automatic gain controller (316) and an output coupled to the switch (304) for selecting between the filtered pathway (312) and the short circuit pathway (310), thereby removing the filter (312) from the signal path if not needed.

An automatic gain control device for an electronic endoscope is provided and comprises a controllable gain amplifier, an A / D converter, a histogram circuit, and a CPU. The controllable gain amplifier amplifies image signals from an imaging device. Amplified image signals from the controllable gain amplifier are input to the A / D converter. A histogram of the amplified image signals from the controllable gain amplifier is produced by the histogram circuit when an image taken in a white-balance test accessory is taken. By using the CPU, the gain of the controllable gain amplifier is adjusted in accordance with the determination of whether a saturated pixel exists for signals in the tolerance range of the A / D converter, so that a linear region of the image signals from the controllable gain amplifier substantially coincides with the tolerance range.

A wireless local area network (WLAN) system can have multiple antennas to improve signal detection and decoding. A WLAN receiver in such a system includes multiple amplifiers that can appropriately size an incoming signal and an automatic gain control unit to process the received incoming signals. The amplifiers of a chain of the WLAN receiver, i.e. an antenna and associated receiver components, can be adjusted with computed gains. To optimize the wireless system detection and decoding, the automatic gain control unit can advantageously compute these gains for each amplifier in the WLAN receiver.

The invention discloses a radio frequency front end device of a receiver and a signal receiving method thereof and belongs to the field of radio communication and satellite positioning and navigation. The device comprises two mutually-independent and parallel signal channels. Each signal channel is connected as follows: a low noise amplifier, a surface acoustic wave filter, a radio amplifier, a quadrature output down-converter, a correction buffer and a multi-mode filter are connected in series; the output end of the multi-mode filter is connected with the input end of a controllable gain amplifier; the output end of the controllable gain amplifier is respectively connected with the input end of an automatic gain controller and the input end of a multi-mode analogue / digital converter; and the output end of the automatic gain controller is connected with a gain control end of the controllable gain amplifier. The invention has the advantages as follows: the radio frequency front end device has system-level and module-level reconfigurability, supports all kinds of the traditional global positioning systems to be the maximum and greatly improves the flexibility of use for users. The radio frequency front end device has strong robustness.

A transmitter and transceiver for an optical communication channel may include a data encoder, a partial response (PR) precoder, a pulse filter, and an electrical-to-optical converter to transmit a spread pulse signal over an optical communication channel. The data encoder to encode the transmit data into coded data. The precoder to correlate bits of the coded data together into a precoded signal at the output of the precoder. The pulse filter to spread out the pulses in the precoded signal into a spread-pulse signal at the output of the pulse-shaping filter. The electrical-to-optical converter to convert an electrical spread-pulse signal into light pulses at its optical output. A transceiver may further include an optical-to-electrical converter, an automatic gain controller, a matched filter, a PR finite impulse response equalizing filter, a maximum likelihood sequence estimation detector, and a data decoder in order to decode and recover the data.

The invention discloses a radio frequency automatic gain control amplifier. The radio frequency automatic gain control amplifier comprises a radio frequency receiving unit, a radio frequency amplifier control unit and an intermediate frequency amplifier, wherein the radio frequency receiving unit is composed of an adjustable low noise amplifier (LNA), a programmable gain amplifier (PGA), a down-conversion frequency mixer and a low-pass filter; the radio frequency amplifier control unit comprises a signal strength detector, a DAC (digital-to-analog converter), a comparator and a decoder; the signal strength detector is used for detecting the strength of an intermediate frequency signal; a comparator circuit is used for comparing an output signal of the signal strength detector with a fixed comparing level output from the DAC so as to output a comparison result; the decoder is used for inputting the comparison result into a gain control digital module and outputting a digital control signal so as to carry out the feedback control to the signal at the front end of the radio frequency, so that the gains of the LNA and the PGA are controlled, the signal to noise ratio of a receiving system is increased, and the requirements on dynamic ranges and high linearity of an input signal are met. The automatic gain control amplifier can be used in various radio frequency receiving chips flexibly, and particularly is applicable to radio frequency front-end circuit which has a wider input range of a radio frequency signal.

A first signal path including a first LNA 3 and a second signal path including an antenna damping circuit 4 and a second LNA 5 are connected in parallel, and switching into either the first signal path or the second signal path is carried out to control a gain of a received signal. When a level of the received signal is higher than a first threshold, it is once attenuated by the antenna damping circuit 4 and is then amplified by a necessary quantity through the second LNA 5. Thus, the gain of the received signal is controlled in a total of the attenuation and the amplification. Consequently, a level of a signal to be input to the second LNA 5 is reduced to cause a distortion of the signal in the amplification with difficulty.

A demodulator controls gains of an RF-AGC amplifier and an IF-AGC amplifier so as to maintain an input level to the demodulator constant. In this case, the demodulator estimates a signal level of an RF input based on the sum of the gains directed to the both AGC amplifiers, and changes methods for distributing a gain to the AGC amplifiers, according to whether or not the signal level exceeds a predetermined Take Over Point. Further, a first detection and smoothing circuit detects an output level of the RF-AGC amplifier, and a second detection and smoothing circuit detects an output of a mixer. Besides, a comparison circuit controls the gain of the RF-AGC amplifier so that a difference between the output levels comes to be a predetermined value. With this structure, an automatic gain control circuit which can achieve high receiving sensitivity and low waveform distortion simultaneously can be realized even when manufacturing dispersion is caused.

In a state where a PLL circuit is not locked, a gain control signal according to the difference between a peak value of a reproduced signal and the upper or lower limit value of the dynamic range of an A / D converter is given to a variable gain amplifier. In a state where the PLL circuit is locked, a gain control signal according to the difference between the reproduced signal and a reference value that corresponds to a level to which the reproduced signal belongs is given to the variable gain amplifier for each sampling point of the A / D converter. The variable gain amplifier amplifies the reproduced signal with a gain according to the gain control signal.

An automatic gain control system combining both analog and digital gain units, both controlled by a common digital control system. The overall system gain settings are selected by a combination of analog gain settings and digital gain settings. The number of analog gain settings is less than the total number of system gain settings, so that the board or chip area required for the analog gain settings is reduced, while sufficient range is provided to maintain a good signal to noise ratio from an A / D converter. When a required gain adjustment exceeds one step of the analog gain stage, the system simultaneously adjusts the analog gain and the digital gain unit to provide a smooth transition.

An automatic gain controller and a method using the same are provided. The automatic gain controller and method analyze background noise by operating a microphone mounted in a mobile communication terminal and automatically control the gain of the signal part which is non-audible due to the background noise. Thus, a user may listen to music by using an earphone or a headphone connected to the mobile communication terminal in an environment with background noise. The method includes receiving an audio signal to be reproduced, receiving a background noise signal introduced through a microphone, controlling a gain of the audio signal by comparing the background noise signal and the audio signal and outputting the gain-controlled audio signal so that the user can listen to the gain-controlled audio signal.

The invention discloses a complementary metal oxide semiconductor (CMOS) automatic gain control amplifier for canceling direct current offset. The CMOS automatic gain control amplifier comprises a cascade amplification link, an automatic gain control feedback loop and a direct current offset canceling feedback loop. The cascade amplification link uses multistage variable gain amplification units for cascading and can achieve high gain and enlarge high gain dynamic ranges. The automatic gain control feedback loop uses a charge pump structure and has the advantages that the automatic gain control feedback loop is less influenced by process deviation and temperature deviation, is capable of accurately detecting narrow-band and wide-band signal amplitude and is suitable for achieving CMOS processes. The direct current offset canceling feedback loop uses two-stage negative feedback loops, and each of the two-stage negative feedback loops uses an integrator as low-pass negative feedback; an active device is used as an integrator input resistor, and an equivalent resistor is provided with characteristics of temperature compensation; and the automatic gain control amplifier for canceling the direct current offset is capable of effectively canceling the direct current offset superposed by a preceding stage circuit and the direct current offset of the amplification link and is provided with a lower high pass corner frequency and a higher integrated level, and the automatic gain control amplifier for canceling the direct current offset is small in low-frequency signal loss and requires no off-chip passive devices (high value resistors or capacitors and the like). The automatic gain control amplifier is applicable to wireless communication receivers with zero intermediate frequency structures in the CMOS processes.

An SDARS receiver includes an analog front end configured to receive a composite signal. An A / D converter is coupled to the analog front end and converts the signal to a digitized signal. A digital down converter (DDC) is coupled to the A / D converter and down converts the digitized signal to a down converted signal. A demodulator demodulates the down converted signal. The receiver includes a digital automatic gain control (DAGC) coupled to an output of the A / D converter and before the demodulator. An automatic gain controller is coupled to the DAGC for providing an automatic gain control signal.

An automatic gain control RF signal processor for receiver systems, such as radar intercept receivers, includes an attenuator having an input for receiving an analog RF input signal, an amplifier coupled to the attenuator, a bandpass filter coupled to the amplifier output, a single ADC coupled to the bandpass filter, a digital logic circuit, and a FIFO buffer. The digital logic circuit has an input for receiving the ADC output signal, a first output coupled to a variable gain control input of the attenuator, and a second output. The logic circuit includes signal detection logic for detecting the presence of a pulse within the ADC signal, determining a peak amplitude value of the pulse, and based on the peak amplitude value generating an attenuation value at the first output that is applied to the variable gain control input of the attenuator. The sampling logic averages a number of ADC data samples to determine a moving average pulse amplitude, and compares this moving average pulse amplitude to a processing threshold value to determine a delta value with which to adjust an attenuation value for the attenuator, and to determine when to terminate a pulse and reset the attenuation value to zero. The averaging is carried out to determine whether an assigned number m of n samples is above the processing threshold value or whether the pulse should be terminated.

The invention relates to a FPGA (field programmable gate array) based digital AGC (automatic gain control) system and method of an ultra-short wave radio set. An RF (radio frequency signal) IN of a receiver is sent to a digital attenuator I to achieve an IF (intermediate frequency) signal through a mixer. One part of the IF signal enters a digital attenuator II, and the other part of the IF signal enters a detector for the detection. An IF-RSSI (received signal strength indicator), received by the detector, is converted into a digital signal by an A / D (analog / digital) converter and entered the FPGA. The signal processing is performed to the FPGA by adopting the sliding window smoothing algorithm to acquire average value of the IF signal. The FPGA judges according to the IF-RSSI. The digital attenuator I and the digital attenuator II are controlled through RFAGC (radio frequency automatic gain control), IFAGC 1(intermediate frequency automatic gain control) and IFAGC2, and a variable gain amplifier is controlled through an SPI interface to achieve constant output of the IF signal. By the use of the FPGA-based digital AGC system and method, automatic gain control on the RF signal reception is achieved within a wide dynamic range, thus the IF signal is maintained within a stable range, and smooth output of the IF signal is realized.

Disclosed is an automatic gain controller capable of reducing signal saturation or signal distortion caused by out-of-band signals of a filter extracting an object signal or delay of a control signal and capable of precisely measuring a signal level in a filter band. An AGC response control section compares a level of control voltage (“V2_I terminal” signal) outputted from a first AGC control section and inputted into a “V2_I terminal” with a level of control voltage (“V3_I terminal” signal) outputted from a second AGC control section and inputted into a “V3_I terminal”. If the control voltage, which is the “V3_I terminal” signal, outputted from the second AGC control section is less than the control voltage, which is a “V2_I terminal” signal, outputted from the first AGC control section, the AGC response control section controls an AGC amplifier by using the control voltage outputted from the second AGC control section. If the control voltage, which is the “V3_I terminal” signal, outputted from the second AGC control section is greater than the control voltage, which is the “V2_I terminal” signal, outputted from the first AGC control section, the AGC response control section controls the AGC amplifier by using the control voltage outputted from the first AGC control section.

A variable gain amplifier (VGA) circuit and an automatic gain control (AGC) method thereof are disclosed. The VGA circuit includes an amplifier circuit and an AGC circuit. The amplifier circuit amplifies an input signal to an output signal according to a predetermined gain and the AGC circuit is connected to the amplifier circuit for regulating the predetermined gain. The AGC circuit further includes a peak detector detecting a peak of the output signal, a replica of the peak detector for detecting a peak of a reference signal, and a comparator for comparing the peak of the output signal with the peak of the reference signal to provide a control signal and then providing the control signal to the amplifier circuit to regulate the predetermined gain.

The invention relates to an amplitude detection and automatic gain control (AGC) circuit. An input signal is taken from a common-mod circuit and an input signal amplitude detection circuit which are respectively connected with a level-shifting circuit, and the level-shifting circuit is connected with an AGC circuit which is connected with an automatic gain circuit. The amplitude detection AGC circuit mainly has the effects that the AGC circuit can detect the amplitude of the input signal and adjusts an AGC voltage according to an amplitude value thereof to further adjust the gain of a transimpedance amplifier, and a large input signal has little output distortion.

The invention discloses a device for eliminating echoes of mobile terminals, which comprises an echo canceller, an automatic gain controller and a noise suppression module, wherein the echo canceller is used for eliminating part of echo signals thereof according to the correlation between upstream signals and downstream signals and then sending output signals to the noise suppression module; the noise suppression module is used for receiving the output signals sent by the echo canceller, filtering noises of environment and residual noises not eliminated by the echo canceller and sending the output signals to the automatic gain controller; the automatic gain controller is used for comparing the downstream signals with the output signals sent by the noise suppression module in real time to conclude a decrement and adding the decrement to the upstream signals to eliminate the residual echoes thereof. The device for eliminating echoes of mobile terminals of the invention solves the problem of destroying normal voice signals when eliminating echoes, such as too great voice attenuation, changes of operation mode into simplex, discontinuous voices, distortion and so on.

The invention discloses an automatic gain control (AGG) self-excited oscillation driving circuit of a micro-solid modal gyroscope, which comprises an oscillation circuit formed by five parts including a charge amplifier, a phase shifter, an amplifier, a band-pass filter and an automatic gain controller, wherein a gyroscope vibration signal is firstly received and enhanced by the charge amplifier, and then phase adjustment is carried out on a signal output by the charge amplifier by the phase shifter, so that the self-excited oscillation condition of a closed loop drive circuit can be met; the signal is amplified by the amplifier, and then frequency-selecting is carried out on the amplified signal by the band-pass filter; after passing through the band-pass filter, the signal enters the automatic gain controller; the automatic gain controller is used for controlling gain according to the difference value between the obtained signal amplitude value and reference signal amplitude value; and finally, a sine driving signal with constant amplitude and stable frequency can be obtained, and a whole closed loop drive system is ensured to be stable. The AGG self-excited oscillation driving circuit can be used for providing the driving signal with constant amplitude and stable frequency to the micro-solid modal gyroscope, so that the problems of the existing closed loop drive circuit can be solved.

In a direction conversion receiver, a quadrature demodulator produces differential signals in a baseband on the basis of a local signal of a frequency synthesizer, with the differential signals being inputted through a first low pass filter, a gain control amplifier and an amplifier to a control unit and a direct current component between the differential signals being extracted in a second low pass filter. In addition, an offset compensating section reduces an offset voltage while the control unit outputs a control signal for the control of the gain control amplifier. The second low pass filter includes a time constant circuit for determining a time constant through the use of resistors and a capacitor, and a time constant changing section. A time constant control unit controls the time constant changing section for a predetermined period of time after the control unit outputs data for the change of a frequency of the local signal so that the time constant of the time constant circuit decreases. This shortens the time needed for the settlement of automatic gain control and prevents the deterioration of demodulation accuracy during a call.