RU75521U1 - ANALOG-DIGITAL CONVERTER (ADC) FOR PROCESSING SIGNALS WITH A BIG DYNAMIC RANGE - Google Patents

Abstract

The invention relates to radio engineering, in particular, to analog-to-digital converters (ADCs) for processing signals with a large dynamic range and without loss of weak signals under noise, and can be used in digital measuring devices and other radio engineering devices. An analog-to-digital converter contains a multi-bit ADC 1 with a discrete value d (1) and a branch connected to it at the input, consisting of an analog signal amplifier and a single-bit ADC 2 with a discrete value d (2), the value of which should be several times exceed the value of d (1), while the gain of the amplifier is chosen equal to Kus = d (2) / d (1). The input signal is simultaneously fed to the multi-bit ADC 1 and to the amplifier, the output of which is fed to the input of the single-bit ADC 2, from the output of which the signal is fed to further processing instead of the low-order signal of the multi-bit ADC 1.

Description

The invention relates to radio engineering, in particular, to analog-to-digital converters (ADCs) for processing signals with a large dynamic range and a large value of the standard deviation (RMS) of noise without loss of weak signals under noise, and can be used in digital measuring instruments and other radio devices.

ADCs are known that use single measurements without subsequent accumulation, which is typical of digital measuring instruments, while the signal measurement accuracy is 0.5 code unit. For processing signals with a large dynamic range, multi-bit ADCs are used, which leads to a sharp reduction in the amplitude of one discrete. So for a 24-bit ADC, the value of one discrete is 596 nV at a full scale of 10 V, while Johnson noise at a bandwidth of 10 kHz, a temperature of 25 ° C and R = 2.2 kOhm is 600 nV [1].

To determine the amplitude of a weak signal under noise, broadband multi-bit ADCs with digital filters are used, which reduce the standard deviation of noise with decreasing digital filter bandwidth [2]. But in this case, since the discrete value is small,

the accuracy of the measurement is influenced by the systematic errors of the ADC, such as delaying the edges of the pulse, the noise of the transition, etc., and the smaller the discrete ADC, the greater the influence of systematic errors.

Known ADCs using an increase in the gain of analog cascades at the input [3], which are the prototype of the proposed ADC. But in this case, the dynamic range of the processed signals decreases, because due to amplification, large signals are previously included in the limitation. The disadvantage of this scheme is the impossibility of simultaneously processing both weak signals and strong signals, since amplification leads to an earlier limitation of the ADC.

The objective of the invention is the creation of an ADC with increased accuracy of processing analog signals with a large dynamic range and a large standard deviation of noise without losing weak signals under noise and without reducing the dynamic range.

To achieve this technical result, the circuit of the analog-to-digital converter (Figure 1) contains a multi-bit ADC 1 with a discrete value d (1) and a branch connected to it at the input, consisting of an analog signal amplifier and a single-bit ADC 2 with a discrete value d (2) , the value of which, depending on the standard deviation of the noise, should several times exceed the value of d (1), while the gain of the amplifier is chosen equal to Kus = d (2) / d (1).

Figure 1 presents the ADC circuit for processing signals with a large dynamic range.

Figure 2 shows a view of the characteristics of the ADC 1.

Figure 3 shows a view of the characteristics of the ADC 2.

The input signal (Figure 1) is simultaneously fed to a multi-bit ADC 1 and to an amplifier, the output of which is fed to the input of a single-bit ADC 2, from the output of which the signal is fed to further processing instead of the low-order signal of a multi-bit ADC 1. As shown in Figure 2, when a signal with a large amplitude arrives, the accuracy of its determination is ensured by a multi-bit ADC 1, which does not limit the amplitude data, but when a signal with a small amplitude under noise arrives, it can be lost due to systematic errors ( it systematic errors is shown in Figure 2 as Δ), so it is determined by a one-bit ADC 2 after amplification, as shown in Figure 3. It should be noted that the zone of systematic errors during amplification remains equal to Δ. At the same time, for clarity, figure 3 shows the definition of the signal when the discretion d (2) of the ADC 2 is quadrupled compared with d (1) ADC 1 and with an amplifier gain of four. In fact, this value should be chosen much larger to reduce the influence of systematic errors.

This scheme solves all the tasks. The use of two ADCs, multi-bit and single-bit with an amplifier, provides signal processing with a large dynamic range and a large standard deviation of noise. The use of a multi-bit ADC 1 with a discrete value d (1) provides an upper limit for determining signal amplitudes.

The determination of weak signals under noise is provided through the use of an input signal amplifier with a gain Kus = d (2) / d (1) and a single-bit ADC 2 with a discrete d (2) several times greater than d (1). Since the discrete value d (2) of a single-bit ADC 2 is increased several times, the influence of systematic errors is reduced, which is especially evident when determining signals whose magnitude is comparable to the ADC discrete, therefore, this invention improves the accuracy of processing weak analog signals.

The ADC performed according to the invention with the use of two signal processing branches and the choice of the discrete ratio of the ADC 1 and ADC 2 in accordance with the standard deviation of noise of the processed signals allowed, without complicating the circuit, to process the signals in a large dynamic range defined upward by the bit depth of the multi-bit ADC 1, and down the accuracy of the single-bit ADC 2.

Literature:

1. Analog-digital conversion, Kester W., March 2004, ADI Central Application Department, p.2.13,2.42-2.43.

2. The study of analog-to-digital converters for digital signal processing using coherent readings, B. Koleman, P. Miyigan, J. Reidy, P. Unix, (translation P-06423).

3. Methods of differential measurement with delta-sigma ADC Linear Technologies, part 2, A. Kozlov, G. Korolev, “CHIP NEWS Ukraine / Microelectronic Engineering”, No. 3, 2007, p. 49.

Claims (1)

A multi-bit analog-to-digital converter (ADC 1) with a discrete value d (1) for processing signals with a large dynamic range, characterized in that it further comprises an analog signal amplifier and a single-bit analog-to-digital converter (ADC 2) with a discrete value d (2) several times higher than d (1), and the amplifier is connected at the input to ADC 1, and at the output from ADC 2 and has a gain Kus = d (2) / d (1).