KR20090059958A - Signal receiver/transmitter and control mecthod thereof - Google Patents

Abstract

A signal transmitting/receiving device and a control method thereof are provided to efficiently improve signal to noise ratio by performing a DC offset detection/correction and a carrier wave leakage in applying a power source. A transmitting part(200) corrects a receiving signal about a carrier wave leakage, and modulates the corrected signal. A receiving part(400) demodulates a signal received from the transmitting part, and performs a DC offset correction about the demodulated signal. A base-band processing part(100) controls a connection setting between the transmitting part and the receiving part. The base-band processing part detects a DC offset about the signal received from the receiving part. The base-band processing part controls a DC offset correction of the receiving part and a carrier wave leakage correction of the transmitting part based on information about the detected DC offset.

Description

Signal transmitting and receiving device and control method thereof {SIGNAL RECEIVER / TRANSMITTER AND CONTROL MECTHOD THEREOF}

The present invention relates to a signal transmission and reception apparatus and a control method thereof. In particular, the present invention relates to a signal transceiving apparatus and a control method of a direct conversion method for efficiently controlling the leakage of the carrier at the time of signal transmission and the detection of DC offset (Dc-Offset) at the time of signal reception.

The present invention is derived from the research conducted as part of the IT growth engine technology development project of the Ministry of Information and Communication and the Ministry of Information and Communication Research and Development. [Task Management Number: 2005-S-404-13, Project Name: 3G Evolution Wireless Transmission Technology] .

As a technique for preventing carrier leakage in a conventional signal transmission, a method using a detection circuit for detecting a carrier leakage signal is used.

The detection circuit of the transmitting and receiving device detects the level of the carrier leakage signal in the signal generated by the frequency modulator (frequency converter), generates a detector output proportional to the detection level, and provides it to the carrier leakage elimination circuit. At this time, the carrier leakage elimination circuit controls the carrier leakage by applying an appropriate DC (direct current) level to the DC coupled low frequency port in consideration of the detector output received from the detection circuit.

In this prior art, a detection circuit for detecting the level of the carrier leakage signal and generating a detector output proportional to the detection level should be separately provided in the transmission and reception apparatus. In order to configure this detection circuit, the transmitter / receiver requires a separate amplifier, a frequency converter, and a band pass filter, and power must be supplied separately for each component.

Therefore, the carrier leakage prevention technique using the conventional detection circuit has a disadvantage in that the circuit is composed of a large amount of power consumption.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a direct conversion signal transmission / reception apparatus and a method of controlling the same, which efficiently control the leakage of a carrier during signal transmission and the detection of a DC offset when receiving a signal.

According to an aspect of the present invention for solving the above problems, the signal transmission and reception apparatus includes a transmitter for compensating for the carrier leakage to the received signal, and modulates the signal on which the carrier leakage compensation has been performed; A receiver which demodulates a signal received from the transmitter and performs DC offset compensation on the demodulated signal; And control a connection setting between the receiver and the transmitter, detect a DC offset for the signal received from the receiver, and compensate for carrier leakage or DC offset based on the information on the detected DC offset. It includes a baseband processing unit for controlling the.

Here, the baseband processing unit,

After the connection between the transmitter and the receiver is established, a first signal for measuring the DC offset of the receiver is provided to the transmitter, and a signal corresponding to the first signal is received from the receiver based on the DC offset detected. To control the DC offset compensation.

According to a feature of the present invention, a method for controlling signal transmission and reception in a signal transmission and reception apparatus includes: establishing a connection between a transmitter and a receiver included in the signal transceiver; Generating a first signal for measuring a DC offset of the receiver and transmitting the first signal to the transmitter; Detecting a first DC offset of a signal corresponding to the first signal received from the receiver; And performing control of the DC offset compensation of the receiver based on the detected first DC offset.

Here, the method for controlling the transmission and reception of the signal, generating a second signal for measuring the carrier leakage of the transmitter and transmitting to the transmitter; Detecting a second DC offset of a signal corresponding to the second signal received from the receiving unit; Performing control on carrier leakage compensation of the transmitter based on the detected second DC offset; And canceling the connection setting so that the transmitter and the receiver are connected to the antenna, respectively.

According to a feature of the invention, a method for controlling signal transmission and reception in a signal transmission and reception device,

Setting up a connection between a transmitter and a receiver included in the signal transceiver; Generating a first signal for measuring carrier leakage of the receiver and transmitting the first signal to the transmitter; Detecting a first DC offset of a signal corresponding to the first signal received from the receiver; And performing control on carrier leakage compensation of the transmitter based on the detected first DC offset.

Here, the method for controlling the transmission and reception of the signal, generating a second signal for measuring the DC offset of the receiver and transmitting to the transmitter; Detecting a second DC offset of a signal corresponding to the second signal received from the receiving unit; Performing control on the DC offset compensation of the receiver based on the detected second DC offset; And canceling the connection setting so that the transmitter and the receiver are connected to the antenna, respectively.

According to the present invention, by performing carrier leakage and direct current offset detection / compensation upon standby or power supply of the terminal, when transmitting and receiving a signal with another device, the signal-to-noise ratio can be effectively improved.

In addition, since the components of the transmitter / receiver that are already configured are used as they are, no additional detection circuit is required, and an effect of reducing power consumption due to the detection circuit can be expected.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have.

The signal transmission and reception apparatus according to an embodiment of the present invention operates at a constant cycle to perform carrier leakage compensation and DC offset compensation. In this case, the predetermined period includes a case in which the system switches to the standby mode when the system is powered on.

Now, a signal conversion apparatus of a direct conversion method for efficiently controlling leakage of a carrier during signal transmission and detection of a DC offset when receiving a signal (hereinafter, referred to as a "direct current offset") according to an embodiment of the present invention; and The control method will be described in detail with reference to the drawings.

1 and 2 are block diagrams illustrating a signal transmission and reception apparatus according to an embodiment of the present invention.

As shown in FIG. 1 and FIG. 2, the signal transmission and reception device according to the embodiment of the present invention includes a baseband processor 100, a transmitter 200, a local oscillator 300, and a receiver 400.

The baseband processor 100 includes a test signal generator 101, a first memory 102, a first memory controller 104, a carrier leakage compensator 106, a detection path control signal generator 108, and a second. The memory 110, the second memory controller 112, the DC offset compensator 114, and the DC offset detector 116 are included.

The test signal generator 101 generates a test signal (a zero signal or a 1-tone signal) for the carrier leakage detection and the DC offset detection, and provides the test signal to the transmitter 200.

The carrier leakage compensator 106 performs a carrier leakage compensation by controlling the DC appliers 206 and 208 of the transmitter 200 based on the DC offset information received from the DC offset detector 116. The carrier leakage compensation information is transmitted to the first memory controller 104 to be stored in the first memory 102. At this time, the carrier leakage compensation unit 106 generates a carrier leakage control signal based on the DC offset information for carrier leakage compensation, and transmits the generated carrier leakage control signal to the DC applying unit (206, 208).

 In addition, the carrier leakage compensator 106 is stored in the first memory 102 when the DC offset compensator 114 performs DC offset compensation to the DC appliers 406 and 408 of the receiver 400. Based on the carrier leakage compensation information, carrier leakage compensation is performed on the DC applying units 206 and 208 of the transmitter 200.

The first memory controller 104 transfers the carrier leakage compensation information received from the carrier leakage compensation unit 106 to the first memory 102.

The first memory 102 stores carrier leakage compensation information received from the first memory controller 104.

The detection path control signal generator 108 sets a detection path for performing carrier leakage detection and DC offset detection. In detail, the detection path control signal generator 108 generates a detection path control signal for controlling a detection path for carrier leakage detection and DC offset detection, and transmits the generated detection path control signal to the first switch of the transmitter 200. 218, the second switch 420 of the receiver 400, the third switch 306 of the local oscillator 300, and the fourth switch 308.

In addition, the detection path control signal generator 108 may output a detection path control signal for controlling the power amplifier 220 of the transmitter 200 to be turned off when the carrier leakage detection and the DC offset detection are performed. To prevent the test signal from radiating to the antenna.

The DC offset detector 116 detects a DC offset based on the baseband signal received from the receiver 400, and transmits the detected DC offset information to the DC offset compensator 114.

The DC offset compensator 114 adjusts the DC level of the DC appliers 406 and 408 of the receiver 400 based on the DC offset information received from the DC offset detector 116 to perform DC offset compensation. The DC offset compensation information is transferred to the second memory controller 112 to be stored in the second memory 110. In this case, the DC offset compensator 114 generates and transmits a DC offset control signal for adjusting the DC level of the DC appliers 406 and 408 of the receiver 400.

In addition, the DC offset compensator 114 is stored in the second memory 110 when the carrier leakage compensator 106 compensates for the carrier leakage of the DC appliers 206 and 208 of the transmitter 200. The DC offset compensation is performed on the DC applying units 406 and 408 of the receiver 400 based on the DC offset compensation information.

The second memory controller 112 transfers the DC offset compensation information received from the DC offset compensator 114 to the second memory 110.

The second memory 110 stores the DC offset compensation information received from the second memory controller 112.

The transmitter 200 includes a digital-to-analog converter 202 and 204, a direct current applying unit 206 and 208, a modulator 210 and 212, a summer 214, a variable amplifier 216, and a first switch 218. ) And a power amplifier 220.

The digital / analog converters 202 and 204 convert the received digital signals (I / Q signals) into analog signals and transmit them to the DC applying units 206 and 208, respectively. At this time, the digital-to-analog converter 202 converts an I (Inphase; "I") signal, and the digital-to-analog converter 204 converts a Q (Quadrature; "Q") signal. Convert each to.

The direct current applying units 206 and 208 apply direct current to the baseband signals received from the digital / analog converters 202 and 204, respectively, and transmit the direct current to the modulators 210 and 212, respectively. At this time, the DC applying unit (206, 208) sets the DC level based on the carrier leakage control signal received from the baseband processing unit 100 to apply a direct current to the baseband signal.

The modulators 210 and 212 convert baseband signals received from the direct current applying units 206 and 208 into signals of a carrier frequency, and transmit them to the variable amplifier 216 through the synthesizer 214. In this case, the modulators 210 and 212 transmit a signal of a carrier frequency obtained by converting the baseband signal using the transmitted local oscillation signal or the received local oscillation signal received from the local oscillator 300 to the variable amplifier 216.

The synthesizer 214 synthesizes the signals received from the modulators 210 and 212 and transmits the synthesized signals to the variable amplifier 216.

The variable amplifier 216 adjusts the output level of the signal received from the modulators 210 and 212.

The first switch controls a detection path for detecting carrier leakage of the transmitter 200, and according to the control of the detection path control signal generator of the baseband processor 100, a second switch of the receiver 400 or a receiver on a wireless link ( Connection with the antenna (omitted) for communication.

The power amplifier 220 amplifies the signal received from the variable amplifier 216 to an output level and transmits the signal to the receiving end.

The local oscillator 300 includes a transmitting LO (Local Oscillator) (hereinafter referred to as "LO") 302, a receiving LO 304, a third switch 306 and a fourth switch 308.

Transmit LO 302 generates a transmit local oscillation signal and receive LO 304 generates a receive local oscillation signal.

The third switch 306 and the fourth switch 308 establish a connection with the transmitting LO 302 or the receiving LO 304 by the control of the detection path control signal generator 108 for the carrier leakage compensation and the DC offset compensation. Do this.

The receiver 400 includes a second switch 420, a low noise amplifier 418, demodulators 414 and 416, variable amplifiers 410 and 412, a DC applying unit, and an analog / digital converter.

The second switch controls the detection path for detecting the DC offset of the receiver 400, and communicates with the first switch 218 or the transmitting end (not shown) on the radio link under the control of the detection path control signal generator 108. Perform a connection setup with an antenna (omitted).

The low noise amplifier 418 amplifies the low noise of the received signal and transmits it to the demodulators 414 and 416.

The demodulators 414 and 416 convert the signals (I / Q signals) received from the low noise amplifier 418 into baseband signals and transmit them to the variable amplifiers 410 and 412, respectively. In this case, the demodulators 414 and 416 convert the carrier signal into a baseband signal by using the transmitted local oscillation signal or the received local oscillation signal received from the local oscillator 300, and convert the converted baseband signals into variable amplification units, respectively. 410, 412.

Here, the demodulator 414 converts the I signal among the received signals into a baseband signal, and the demodulator 416 converts the Q signal among the received signals into a baseband signal.

The variable amplifiers 410 and 412 adjust the output levels of the signals received from the demodulators 414 and 416, respectively.

The DC applying units 406 and 408 apply DC to the baseband signals received from the variable amplifiers 410 and 412, respectively, and transmit the DC signals to the analog / digital converters 402 and 404. At this time, the DC applying unit 406, 408 sets the DC level based on the DC offset control signal received from the baseband processing unit 100 to apply a DC to the baseband signal.

The analog / digital converters 402 and 404 convert the analog signals received from the direct current applying units 406 and 408 into digital signals and transmit them to the baseband processor 100.

The signal transmitting and receiving device according to an embodiment of the present invention can efficiently improve the signal-to-noise ratio when transmitting and receiving signals with other devices by performing carrier leakage and DC offset detection / compensation upon standby or power supply. There is this. In addition, since the components of the transmitter / receiver that are already configured are used as they are, no additional detection circuit is required, and power consumption due to the detection circuit can be reduced.

In addition, since there is no need to add a separate configuration device, there is a great advantage to simplify the configuration of the system.

3 is a flowchart illustrating a carrier leakage detection control method of a signal transmission and reception apparatus according to an embodiment of the present invention.

As shown in FIG. 3, the baseband processor 100 of the apparatus for transmitting and receiving a signal according to an embodiment of the present invention sets a detection path for detecting carrier leakage of the transmitter 200 (S100).

Specifically, the baseband processing unit 100 generates a detection path control signal to detect carrier leakage, and thus, the first switch 218 of the transmitter 200, the second switch 420 of the receiver 400, and the local part. The third switch 306 and the fourth switch 308 of the oscillator 300 is transmitted to the power amplifier 220 of the transmitter 200. In this case, the first switch 218 of the transmitter 200 and the second switch 420 of the receiver 400 perform interconnection based on the received detection path control signal, and perform a third switch of the local oscillator 300. 306 and fourth switch 308 are coupled to transmit LO 302.

After setting the detection path, the baseband processor 100 generates a test signal (signal of 0) and transmits the test signal to the transmitter 200. In this case, the test signal (signal 0) is a signal 0 in all bands and is a signal for measuring the DC offset of the receiver.

The transmitter 200 receives a test signal (signal 0) from the baseband processor 100 and performs digital / analog conversion, DC application, conversion to a carrier wave, and variable amplification on the received test signal (signal 0). To perform. Then, the performed test signal is transmitted to the second switch 420 through the first switch 218.

The receiver 400 transmits the generated baseband signal to the baseband processor 100 after low noise amplification, demodulation, variable amplification, direct current application, and analog / digital conversion are performed on the signal received from the second switch 420. do.

The baseband processor 100 receives a baseband signal corresponding to the test signal (signal 0) from the receiver 400 and detects a DC offset with respect to the received baseband signal (S102). The baseband processor 100 controls the DC applying units 406 and 408 of the receiver 400 based on the detected DC offset to compensate for the DC level (S104). At this time, the baseband processor 100 stores the compensated DC offset information.

Thereafter, the baseband processor 100 changes the test signal from a signal of 0 to a 1-tone signal (S106), and the baseband processor 100 transmits the changed test signal (1-tone signal) to the transmitter ( 200). Here, the 1-Ton signal refers to a signal for one of a plurality of bands used by a signal transmitting and receiving device, and in a state in which a DC offset compensation value of the receiver 400 is set, the carrier leakage of the transmitter 200 is set. It is a signal to measure.

The transmitter 200 receives a test signal (1-tone signal) from the baseband processor 100, and converts the digital signal into analog / analog conversion, direct current application, and conversion to a carrier wave. Perform amplification. Then, the performed test signal is transmitted to the second switch 420 through the first switch 218.

The receiver 400 transmits the generated baseband signal to the baseband processor 100 after low noise amplification, demodulation, variable amplification, direct current application, and analog / digital conversion are performed on the signal received from the second switch 420. do.

The baseband processor 100 receives a baseband signal corresponding to the test signal (1-tone signal) from the receiver 400, and detects a DC offset with respect to the received baseband signal (S108). At this time, since the DC offset detection / compensation for the test signal 0 has already been performed, only the amount of change due to the DC offset mismatch is detected.

The baseband processor 100 compensates for the carrier leakage so that the DC offset with respect to the test signal (1-tone signal) is minimized. Specifically, the baseband processing unit 100 controls the DC applying unit of the transmitter 200 to adjust the DC level (S110).

At this time, the baseband processor 100 stores information on carrier leakage compensation.

Subsequently, the transmitter 200 transmits a signal of which carrier leakage is compensated through a DC level which is previously adjusted with respect to the baseband signal received from the baseband processor 100.

Through such a carrier leakage detection control, the signal transmission and reception device has an advantage of detecting / compensating the influence of the carrier leakage of the transmitter 200 and subsequently improving the signal-to-noise ratio of the transmission signal transmitted to the receiver of another device. .

Hereinafter, a detection and control method for a DC offset of a signal transceiver according to an exemplary embodiment of the present invention will be described with reference to FIG. 4. The detection and control method for the DC offset according to an embodiment of the present invention may be performed in conjunction with the carrier leakage detection control method of FIG.

4 is a flowchart illustrating a method for detecting and controlling a DC offset in a signal transmission and reception apparatus according to an embodiment of the present invention.

As shown in FIG. 4, the baseband processor 100 of the apparatus for transmitting and receiving a signal according to an embodiment of the present invention performs detection path connection setting for detecting a DC offset of the receiver 400 (S200).

Specifically, the baseband processor 100 generates a detection path control signal for detecting a DC offset, and thus, the first switch 218 of the transmitter 200, the second switch 420 of the receiver 400, and the local oscillator. The third switch 306 and the fourth switch 308 of 300 and the power amplifier 220 of the transmitter 200 is transmitted.

In this case, the first switch 218 of the transmitter 200 and the second switch 420 of the receiver 400 perform interconnection based on the received detection path control signal, and perform a third switch of the local oscillator 300. 306 and fourth switch 308 are coupled to receive LO 304.

After setting the detection path, the baseband processor 100 generates a test signal (1-tone signal) and transmits the test signal to the transmitter 200. At this time, the test signal (1-tone signal) is a signal for measuring the carrier leakage of the transmitter.

The transmitter 200 receives a test signal (1-tone signal) from the baseband processor 100, and converts the digital signal into analog / analog conversion, direct current application, and conversion to a carrier wave. Perform amplification. Then, the performed test signal is transmitted to the second switch 420 through the first switch 218.

The receiver 400 transmits the generated baseband signal to the baseband processor 100 after low noise amplification, demodulation, variable amplification, direct current application, and analog / digital conversion are performed on the signal received from the second switch.

The baseband processor 100 receives a baseband signal corresponding to the test signal (1-tone signal) from the receiver 400, and detects a DC offset with respect to the received baseband signal (S202). Then, the baseband processor 100 adjusts the DC level of the transmitter 200 to minimize the detected DC offset (S204). In detail, the baseband processor 100 controls the DC applying units 206 and 208 of the transmitter 200 to control the carrier leakage of the transmitter 200 to minimize the detected DC offset. At this time, the baseband processor 100 stores carrier leakage compensation information that compensates for the DC level in the transmitter 200.

Thereafter, the baseband processing unit 100 changes the test signal from the 1-tone signal to a test signal having all bands 0 (S206), and the baseband processing unit 100 transmits the changed test signal (signal 0). 200). At this time, the test signal (signal 0) is a signal for measuring the DC offset of the receiver in a state where the carrier leakage compensation value of the transmitter is set.

The transmitter 200 receives a test signal (signal 0) from the baseband processor 100 and performs digital / analog conversion, DC application, conversion to a carrier wave, and variable amplification on the received test signal (signal 0). To perform. Then, the performed test signal is transmitted to the second switch 420 through the first switch 218.

The receiver 400 transmits the generated baseband signal to the baseband processor 100 after low noise amplification, demodulation, variable amplification, direct current application, and analog / digital conversion are performed on the signal received from the second switch 420. do.

The baseband processor 100 receives a baseband signal corresponding to the test signal (signal 0) from the receiver 400 and detects a DC offset with respect to the received baseband signal (S208).

Since the baseband processor 100 has already performed carrier leakage compensation on the test signal (1-tone signal), the baseband processor 100 adjusts the DC level of the receiver 400 to minimize the DC offset of the test signal (signal 0) ( S210). In detail, the baseband processor 100 controls the DC applying units 406 and 408 of the receiver 400 to compensate for the DC offset.

Thereafter, the receiver 400 transmits a signal of which the DC offset is compensated through the DC level which is previously adjusted to the baseband processor 100.

Through the DC offset detection / compensation, the signal transceiving device compensates for the DC offset of the receiver 400, thereby improving the signal-to-noise ratio for a signal received from a transmitting end of another device.

The embodiments of the present invention described above are not implemented only through the apparatus and the method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Implementation may be easily implemented by those skilled in the art from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 and 2 are block diagrams illustrating a signal transmission and reception apparatus according to an embodiment of the present invention.

3 is a flowchart illustrating a carrier leakage detection control method of a signal transmission and reception apparatus according to an embodiment of the present invention.

4 is a flowchart illustrating a method for detecting and controlling a DC offset in a signal transmission and reception apparatus according to an embodiment of the present invention.

Claims (8)

A transmitter for compensating carrier leakage for the received signal and modulating a signal on which carrier leakage compensation has been performed; A receiver which demodulates a signal received from the transmitter and performs DC offset compensation on the demodulated signal; And Control the connection setting between the receiver and the transmitter, detect a DC offset for the signal received from the receiver, and perform carrier leakage compensation or DC offset compensation on the receiver based on information on the detected DC offset. Baseband processor to control Signal transmitting and receiving device comprising a. The method of claim 1, The baseband processing unit, After the connection between the transmitter and the receiver is established, a first signal for measuring the DC offset of the receiver is provided to the transmitter, and a signal corresponding to the first signal is received from the receiver based on the DC offset detected. Signal transmitting and receiving device for controlling the DC offset compensation by. The method of claim 2 The baseband processing unit, A signal transmitting / receiving apparatus for providing a second signal for measuring carrier leakage of the transmitter to the transmitter, and controlling a carrier leakage compensation based on a DC offset detected by receiving a signal corresponding to the second signal from the receiver; . The method according to claim 2 or 3, Further comprising a local oscillator comprising a transmitting local oscillator and a receiving local oscillator, The baseband processing unit, And a local oscillator controlling the local oscillator to provide a transmission local oscillation signal for the carrier leakage compensation to the transmitter and the receiver. The method of claim 1, The baseband processing unit, After the connection between the transmitter and the receiver is established, a first signal for measuring carrier leakage of the transmitter is provided to the transmitter, and a signal corresponding to the first signal is received from the receiver based on the detected DC offset. And a signal transmitting and receiving device for controlling the carrier leakage compensation. The method of claim 5, The baseband processing unit, A signal transmitting / receiving apparatus for providing a second signal for measuring a DC offset of the receiver to the transmitter, and controlling a DC offset compensation based on a DC offset detected by receiving a signal corresponding to the second signal from the receiver; . The method according to claim 5 or 6, Further comprising a local oscillator comprising a transmitting local oscillator and a receiving local oscillator, The baseband processing unit, And a local oscillator controlling the local oscillator to provide a reception local oscillation signal for the DC offset compensation to the transmitter and the receiver. The method according to any one of claims 1 to 3, 5 and 6, The transmitter and the receiver, respectively It includes a DC applying unit for applying a DC power of a predetermined DC level to the received signal, And the baseband processor controls the DC level of the DC applying unit for the carrier leakage compensation or the DC offset compensation.

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