DE3543744A1 - METHOD FOR ANALOG-DIGITAL CONVERSION AND DEVICE FOR IMPLEMENTING THE METHOD - Google Patents

Description

Systemteknik AB: ":: -..-: .. December 11, 1985

Vasavägen 76.:. .:. X .... '..' ^: ..'-. "'■ A 6691 ο c L 0 7 / / S-181 41 Lidingö ° ° ⁴ °' ^HH

Sweden

METHOD FOR ANALOG-DIGITAL CONVERSION AND DEVICE FOR CARRYING OUT THE METHOD

The present invention relates to a method and an apparatus for analog-to-digital conversion.

Electronic analog-to-digital converters receive as an input signal an analog signal of a value within of a predetermined amplitude interval and emit a digital signal as an output signal, usually a binary signal of a binary value corresponding to the value of the analog signal.

A critical parameter of the analog-to-digital converter is the cycle time, i.e. the time to carry out a full analog-to-digital conversion. The cycle time directly determines the conversion frequency and thus also the maximum frequency for sampling the analog signal.

The reduction of the cycle time in order to enable an increase in the sampling frequency is required Use of more expensive analog-to-digital converters and the increase in cost is highly progressive.

It is therefore an object of the present invention to provide an increased sampling frequency or sampling speed at a relatively low cost. In a process for converting an analog Signal into a digital signal, this object is achieved in a form of the invention in such a way that the The method is characterized in that the analog signal is sampled, and that the sampled values in digital form can be converted in a time sequence by means of several analog-to-digital converters, their time segments between the samples are shorter than the cycle time of the analog-digital converter.

According to another form of the present invention this task is accomplished by means of an analog-to-digital conversion device solved, which is characterized by several separate analog-to-digital converters whose

Inputs are connected to receive one and the same analog signal, and their outputs to a selector for Choice of one output each time as output for the entire device are connected. Preferred embodiments of the method and the device according to the invention are based on the following, non-independent claims.

The invention provides an analog-to-digital conversion device Done at a price about only one-tenth the cost of a conventional one Way trained analog-to-digital converter is.

The analog-to-digital conversion device according to the invention also enables closely consecutive Sampling of an analog signal within a limited period of time, which is possible with known analog-to-digital converters was not possible.

An embodiment of the invention is described in more detail below with reference to the accompanying drawing. Show it

Fig. 1 is a block diagram of an example of an analog-digital conversion device according to the invention,

2 shows the division of the cycle time of a conventional analog-digital converter,

3 shows how four analog-to-digital converters according to the invention can be used to set the sampling frequency and Figure 4 shows an alternative timing of four Analog-to-digital converters.

The embodiment of an analog-digital conversion device according to the invention shown in FIG. 1 has a plurality, n, of analog-to-digital converters 1, which are one and the same at the respective input 2 Receive analog signal by electrically connecting the inputs 2 to a single input terminal 3 to which the analog signal is fed.

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The analog-digital converters 1 each have an output 4 which is connected to a special input 5 to a selector 6 is, the number of inputs 5 corresponding to the number of analog-to-digital converters 1 and one Output connection 7 has.

A control unit for the converter 1 and the selector 6 comprises a synchronizing unit 8, each of which Converter 1 by alternating two-way traffic with this via a scanning unit 9 for each converter 1 controls and supervised. The synchronization unit 8 is also for alternating two-way traffic with superordinate, not shown Elements connected, which are included in the control unit. Finally, the synchronization unit 8 is on a control input to the selector 6 is connected.

Before describing the operation of the device According to FIG. 1, the working cycle of an analog-to-digital converter with reference to FIG. 2 is brief below described. Conventional analog-to-digital converters are of the double ramp type and this means that the cycle time contains a time segment 10 in which the sampled value of the analog signal at a certain moment is integrated, as well as a subsequent time segment 11 in which an analog reference signal in opposite Direction is integrated up to the zero crossing, the time of integration of the reference signal is a measure of the magnitude of the sampled value and is expressed digitally, usually in binary. The time period The signal integration is preceded by a period of time 12 in which the input signal value automatically increases zero is set, and the time segment 11 can be a short time segment 13 before the next working cycle follow. The time segment 10 is typically a quarter of the total cycle time, thus reducing the sampling frequency is more limited than is necessary for the actual signal integration is required.

According to the invention, a plurality of analog-to-digital converters connected essentially in parallel

is used, the time interval between samples of the analog signal can be drastically reduced.

The analog-to-digital converter in the exemplary embodiment according to Pig. 1 are according to the invention in a time sequence started whose time segments between the samples are shorter than the cycle time of the analog-digital converter. This is accomplished with the aid of the synchronizing unit 8, which controls the conversion cycles of the converters 1 starts sequentially via the relevant scanning unit 9 and by receiving finished signals from it Unit controls the selector 6 synchronized with the sequential start of the respective analog-digital converter.

As can be seen from FIG. 3, where the dashed sections correspond to the time section 10 in FIG. 2, four analog-to-digital converters ad according to FIG too high is like digital converter analog and much lower for a single, simple as ^he d price of four times as fast analog-to-digital converter.

Instead of the time segments between the samples or starting times of the analog-digital converter as in FIG. 3 The time segments can be used to equalize the time of the converter for integrating the analog signal longer than this time can be made.

The embodiment according to FIG. 3 means an essentially constant coverage of the analog signal. According to the invention, however, it is possible to distribute the start of the analog-digital converter in a different way. As can be seen from Fig. 4, for example, the conversion cycles of the four analog-to-digital converters a-d be triggered in closer succession. This means that a short period of time of an analog signal can be reduced in a very short time finely divided into digital form.

The time segments from the start of one analog-digital converter to the start of the next converter can be specified in

can be varied in any way, for example made of different lengths. The analog-to-digital converter can also be started in an aperiodic sequence, eliminating the undesirable effect of periodic Components of the analog signal on the measurement result can be eliminated.

Several modifications are within the scope of the invention of the embodiments described above possible. This means that a larger or smaller part of the control unit can consist of a microprocessor.

Claims (8)

11th December A 669 ^ 5 ^ PATENT CLAIMS 1. A method for converting an analog signal _Λ into a digital signal, characterized in that the analog signal is sampled, and that the samples are converted into digital form by means of several analog-digital converters in a time sequence that contains time segments between the samples , which are shorter than the cycle time of the analog-digital converter. 2. The method according to claim 1, characterized in that g e k e η η shows that the time segments between the samples are greater than or equal to the time of the analog-to-digital converter to integrate the analog signal. 3. The method according to claim 1, characterized in that g e k e η η draws that the time segments between the samples are smaller than the time of the analog-to-digital converter to integrate the analog signal for selected sections thereof. 4. The method according to claim 1, characterized in that g e k e η η shows that the time segments between the samples are made different in length. 5. Analog-digital conversion device, characterized by several separate analog-digital converters (1) whose inputs (2) are switched to receive one and the same analog signal, and their outputs with a selector (6) for selecting one output each time as an output for the entire device are connected. 6. Analog-to-digital conversion device according to claim 5, characterized by a Control unit (8) for the sequential start of the conversion cycles of the converters as well as one sequential with this Start synchronized control of the selector (6). 35437AA 7. Analog-to-digital conversion device according to
Claim 5 or 6, characterized in that
that the inputs (2) of the analog-digital converter (1)
are connected to each other. 8. Analog-to-digital conversion device according to one of claims 5-7, characterized in that that the control unit (8) is a microprocessor.