ANALOG-TO-DIGITAL CONVERTER COUPLED TO A DYNAMIC LINEARITY CORRECTOR
Publication Date: 2017-May-04
The IP.com Prior Art Database
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Kenneth D. Poulton
Keysight technologies Inc.
An analog-to-digital converter (ADC) is typically used to convert an analog signal into digital data that can be processed in the digital domain. For example, an audio signal generated from a microphone can be converted into digital data bits that can then be used for carrying out various digital signal processing (DSP) functions such as equalization and filtering. Performing such functions in the digital domain is desirable for various reasons such as allowing various circuit parameters to be readily modified without changes in hardware, and also in terms of providing a consistent and repeatable level of performance. However, various characteristics of an ADC (such as resolution, accuracy, quantization error, sampling rate, and non-linearity) can prove inadequate in some applications and lead to distortion being present in the digital signal output of the ADC.
One device that is used for addressing distortions created as a result of a non-linear transfer function characteristic of an ADC (and of other devices coupled to the ADC) is known as a digital linearity corrector. A first type of digital linearity corrector, which is a static linearity corrector, can be used to correct distortions caused by errors in a static transfer function of an ADC. The distortions in this case are independent of signal frequency. A second type of digital linearity corrector, which is a dynamic digital linearity corrector, can be used to correct frequency-dependent distortions.
The static linearity corrector and/or the dynamic digital linearity corrector can not only be used to correct signal distortions caused by an ADC but can also be used to address signal distortions caused by a digital-to-analog converter (DAC). In contrast to an ADC, a DAC is typically used to convert a digital signal into an analog signal. For example, a digital signal generated in a transmitter unit, by using the ADC as referred to above, can be converted in a receiver unit into an analog signal that is a replica of the analog signal generated by the microphone in the transmitter unit.
Fig. 1 below shows a dynamic digital linearity corrector coupled ahead of a DAC. The dynamic linearity corrector is used here to digitally pre-distort a signal in order to nullify distortion created by the DAC. The procedure, which can be referred to as digital pre-distortion (DPD), can be used to compensate for various kinds of nonlinearities in one or more analog components of a signal. US Patent 8,842,033 B1 titled “Dynamic Linearity Corrector for Digital-Analog Converters” (inventor Valentin Abramzon, issued September 23, 2014) discloses details of the circuit shown below in Fig. 1.
Fig. 1 Dynamic digital linearity corrector circuit coupled to a DAC
In contrast to Fig. 1, which shows a dynamic digital linearity corrector coupled ahead of a DAC in order to provid...