An Automatic Gain Control Amplifier for Eliminating DC Offset

Abstract

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.

Description

technical field [0001] The invention belongs to the technical field of digital communication, relates to an automatic gain control amplifier, in particular to an automatic gain control amplifier for eliminating direct current offset, which is used to realize a highly integrated automatic gain control amplifier with the function of eliminating direct current offset. Background technique [0002] For wireless receivers, due to the large change in the strength of the received signal, or the deviation of the gain of the off-chip or RF front-end circuit, the amplitude of the analog baseband signal after frequency conversion changes drastically, resulting in a serious deterioration in the performance of the analog-to-digital converter. The baseband cannot be demodulated correctly, so it is necessary to introduce an automatic gain control amplifier for adjustment, so that the signal received by the analog-to-digital converter has a stable amplitude, reducing the impact of the amplit...

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Problems solved by technology

Francesco Gatta et al in IEEE Journal of Solid-State Circuits, 2004: "A Fully Integrated 0.18-μm CMOS Direct Conversion Receiver Front-End With On-Chip LO for UMTS" paper and Kim Ji-Hun et al in ICACT, 2006: The paper "A CMOS Variable Gain Amplifier with Wide Dynamic Range and Accurate dB-Linear Characteristic" was published, and the proposed integrator feedback DC offset elimination structure only uses one negative feedback, so when the variable gain amplifier works in a high gain state When the high-pass corner frequency is large, the loss of low-frequency signals is too large, so it is not suitable for high-gain and high-dynamic-range applications, or increasing the integral capacitor to achieve a lower high-pass corner frequency will consume a large chip area

"A Wideband CMOS Variable Gain Amplifier With an Exponential Gain Control" paper published by Lee Hui Dong et al. in IEEE Transactions on Microwave Theory and Techniques, 2007, and publication number CN101442325, titled "Amplifier with Bandpass Filtering Function" patent , the RC low-pass filter method is used as the negative feedback method in the elimination structure, and there is a contradiction between the degree of integration and the amount of low-frequency signal loss

The on-chip active high-impedance implementation proposed by Wang Yan Jie et al. in the 2008 IEEE Radio Frequency Integrated Circuits Symposium, 2008: "A 2.5mW Inductorless Wideband VGA with Dual Feedback DC-Offset Correction in 90nm CMOS Technology" paper is limited to 90nm And the following processes have great limitations

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