31results about How to "Eliminate DC offset" patented technology

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.

The invention discloses a method for network voltage amplitude, frequency and phase angle detection based on the one-phase phase-locked loop algorithm. According to the method, accurate amplitude, frequency and phase angle detection is achieved when direct current offset and harmonic waves exist in a one-phase power grid. The method comprises the steps that a network voltage signal is acquired and transmitted to a delay phase-shifting module; the delay phase-shifting module receives a network voltage frequency value obtained from the last cycle at the same time and outputs a network voltage delay signal; subtraction is carried out on the acquired network voltage signal and the network voltage delay signal to obtain a result, and the result is divided by 2 to obtain a network voltage signal free of direct current offset; the network voltage signal free of direct current offset is taken as an input signal of an enhanced phase-locked loop, and then the network voltage amplitude value, frequency value and phase angle value of the cycle are obtained. The method for network voltage amplitude, frequency and phase angle detection based on the one-phase phase-locked loop algorithm is suitable for the field of conversion of electrical energy.

The invention relates to an amplifier with ultralow direct current (DC) offset at an input end and an analog/digital (A/D) converter. The amplifier with the ultralow DC offset at the input end comprises a chopped wave modulator, a sampling instrument, a correlated double sampling (CDS) instrument and an amplifying/integration unit which are connected in sequence. A chopped wave demodulator is arranged in a circuit behind the sampling instrument. The chopped wave modulator and the chopped wave demodulator are used for eliminating residual DC offset generated due to imperfection of the CDS instrument and the other circuit components. On the other hand, the CDS instrument can also eliminate residual DC offset of the chopped wave modulator and the chopped wave demodulator. Due to the fact that the chopped wave modulator and the chopped wave demodulator modulate the residual DC offset of the CDS instrument and other circuit components at the clock frequency of 2*ck_chop to generate high-frequency modulating signals, input signals and the modulating signals do not overlap in a frequency domain. Consequently, the modulating signals can be eliminated at a low-pass filter which is connected with an output end of the amplifier with the ultralow DC offset at the input end. Therefore, the purpose of eliminating the residual DC offset of sampling signals is achieved.

The invention discloses an alternating current signal measurement device, an alternating current signal measurement system and an alternating current signal measurement method and relates to the field of alternating current electric signal measurement. The device is provided with an access part 1, a measurement part 2 and a control part 3, wherein the output end 10 of the access part 1 is connected with the input end of the measurement part 2 and is also connected with an instantaneous discharge circuit 14 controlled by the control part 3. The control part 3 can control the access part 1, the measurement part 2 and the instantaneous discharge circuit 14 to perform the instantaneous discharge operation of the output end 10, and adopts the following control steps: firstly, turning on the instantaneous discharge circuit; secondly, delaying a preset time period; and thirdly, turning off the instantaneous discharge circuit. The device of the invention accelerates the elimination of an abrupt signal which appears at the position of the output end 10 of the access part 1 and is caused by the quick change of the gain of a programmable amplifying circuit 7 in the access part 1. The device has the characteristics of reducing measurement access time, along with simple structure and convenient control.

The invention discloses a DC offset cancellation circuit, which comprises a first transistor, a second transistor, a third transistor, a fourth transistor, a first feedback capacitor, a second feedback capacitor, a first voltage control signal port, a second voltage control signal port, a signal input positive end, a signal input negative end, a signal output positive end, a signal output negative end and an operational amplifier. A first voltage control signal controls the resistance of equivalent resistors of the first and second transistors, and a second voltage control signal controls the resistance of the equivalent resistors of the third and fourth transistors to fulfill the aim of adjusting equivalent high pass off frequency; therefore, the DC offset cancellation circuit can reduce damages to useful low frequency components in the signals as much as possible at the same time of suppressing or canceling DC offset. The DC offset cancellation circuit adopts active resistors instead of passive resistors, so the area of a circuit layout is reduced, and the level of integration of the circuit is improved.

The invention discloses a logarithmic amplifier which comprises a subtracter in a folding structure, at least one amplifier in a folding structure, at least three rectifiers in a current subtracter structure, two variable capacitor arrays and three resistor arrays. The logarithmic amplifier provided by the invention has lower power and stronger anti-PVT bias capability, automatically corrects a resistance-capacitance time constant by controlling a time constant correction circuit, ensures the response speed and the ripple characteristics of an output signal in case of PVT bias, ensures the stability of the logarithmic amplifier and eliminates the direct current shift. Further, by adjusting the structures of the variable capacitor arrays, the invention improves the accuracy of the whole capacitance value and ensures that a feedback network can effectively eliminate the direct current shift of the logarithmic amplifier and ensure the stability of a feedback loop.

The invention relates to a sensor and a detector on the basis of avalanche photodiodes. The sensor comprises a plurality of APD (avalanche photodiode) sensors. The multiple APD sensors are parallelly sequentially stacked on one another and include single-tube APD sensors or array APD sensors. The detector comprises the sensor and a multi-channel reading circuit. The multi-channel reading circuit comprises current-to-voltage amplification modules and baseline restoration modules, is electrically coupled with the sensor and is used for reading out current signals outputted by the sensor. The sensor and the detector have the advantages that the sensor is configured with the multiple APD sensors which are parallelly sequentially stacked on one another, and accordingly the sensor and the detector are high in quantum efficiency under the condition of sub-nanosecond time resolution; the detector is configured with the multi-channel reading circuit, weak signals outputted by the APD sensors can be read out, the APD sensors can be effectively matched with one another, accordingly, the time resolution performance of the APD detector can be improved, and the integration level of the APD detector can be upgraded.

The invention discloses a signal processing apparatus applied to time-varying signals. The signal processing apparatus comprises a summator and a weighting integrator. The summator is used for receiving a first input signal and an integrated signal and generating a first output signal, wherein the first output signal is equal to a result obtained by subjecting the first input signal and the integrated signal to subtraction. The weighting integrator is used for receiving the first output signal and generating the integrated signal and comprises a weighting function generator, a multiplier and an accumulator, wherein the weighting function generator is used for receiving the first output signal and generating a weighting function when the first output signal passes by the position nearby a zero crossing point, the multiplier is used for multiplying the weighting function by the first output signal, and the accumulator is connected with the multiplier and used for accumulating the result obtained by multiplying the weighting function by the first output signal and generating the integrated signal according to the accumulated result. The signal processing apparatus applied to the time-varying signals has the advantage that direct-current offset in a photoelectronic signal can be eliminated.

The invention discloses a reset-free burst signal detection circuit, and the circuit is characterized in that a burst detection function is realized by charging a load capacitor through a three-input transconductance amplifier after a burst signal high-frequency component is loaded on a common-mode level of the burst signal high-frequency component. The direct-current offset of the signal can be eliminated by loading the high-frequency component of the signal to the common-mode level of the signal; for a three-input transconductance amplifier, the transconductance amplifier outputs current to charge a load capacitor in the presence of an emergent alternating current signal, so the voltage of an output node is increased, and an emergent detection signal is generated. The burst detection circuit has the advantages that reset signals are not needed, the structure is simple, the working speed is high, and power consumption is low; the number of components is reduced, the occupied chip area is smaller, the circuit integration degree is improved, the cost is reduced, and burst signal detection is easily achieved.

The invention relates to the field of integrated circuits, in particular to a digital-assisted direct-current offset cancellation circuit and a digital control method thereof. The direct-current offset cancellation circuit comprises a variable gain amplifier, a comparator with a rail-rail input voltage range, a digital control module and a 11-bit digital-to-analog converter, and an electric signal is input into the variable gain amplifier; a comparator with a rail-rail input voltage range samples differential voltage output by the variable gain amplifier in a given time window, polarity and corresponding times of the sampled differential voltage are recorded in a digital control module, the digital control module selects a direct current compensation mode according to recorded information and updates the differential voltage, the updated differential voltage is used as the input of a 11-bit digital-to-analog converter, and the output end of the 11-bit digital-to-analog converter is connected with the input end of a variable gain amplifier; and according to the invention, the direct-current offset of the receiver can be effectively eliminated.

The invention discloses a broadband low-noise high-linearity wide-range demodulation system, and relates to the technical field of broadband demodulation. The system comprises a receiving unit and a transmitting unit, the receiving unit comprises a low-noise amplification module, the low-noise amplification module is connected with a voltage-current conversion module, the voltage-current conversion module is connected with two down-conversion modules, the down-conversion modules are connected with a transimpedance amplification module, the transimpedance amplification module is connected with a first low-pass filtering module, and the first low-pass filtering module is connected with a second low-pass filtering module. The first low-pass filtering module is connected with a variable gain amplification module, the variable gain amplification module is connected with analog-to-digital conversion modules, the two analog-to-digital conversion modules are connected with a first integrated unit, and the transmitting unit comprises a resistor. The low-pass filter is closely followed after the transimpedance amplification module, so that out-of-band blocking is further suppressed, the pressure of the analog-to-digital converter is reduced, the bandwidth of the filter can be accurately calibrated, and controllable current is injected into the input side of the variable gain amplification module.