JPH0358206B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an A/D conversion circuit, and in particular can be used for coarse quantization of a plurality of analog signals and fine quantization of one analog signal by switching. It relates to an A/D conversion circuit.

[Conventional technology]

Digital transmission methods, which quantize analog signals and transmit them as digital signals, are widely used in various fields, and are also used when transmitting various observation data from artificial satellites. Artificial satellites such as earth observation satellites are equipped with multiple observation instruments, and some of the observation data obtained by these instruments can be transmitted using coarse quantization of, for example, 3 bits; Some information requires precise quantization of bits. Furthermore, these observation data are not necessarily observed and transmitted simultaneously, but are often configured to be observed alternately over time due to satellite power constraints. In such a case, one set of 6-bit data (for example, observation data from an optical sensor) or two sets of 3-bit data (for example, data from a micro- Conventionally, when performing quantization with different numbers of bits, a separate A/D was used for each.
Either prepare converters (one 6-bit and two 3-bit), or use only the upper bits of the output of the A/D converter that performs fine quantization and also use it for coarse quantization. Saves one D converter (6 bits,
3 bits each).

[Problems to be solved by the invention]

In the conventional configuration described above, when performing 6-bit quantization, no 3-bit A/D converter is used, and when performing 3-bit quantization, no 6-bit A/D converter is used. Otherwise, the lower 3 bits will be wasted, and in the case of equipment mounted on a satellite, which has strict restrictions, there is a problem in terms of weight and power consumption design. An object of the present invention is to provide an A/D conversion circuit that can be used by switching between coarse quantization of a plurality of analog signals and fine quantization of one analog signal, and which can reduce the above-mentioned waste of weight and power consumption. It is.

[Means to solve the problem]

The A/D conversion circuit according to the present invention includes at least two first and second A/D converters that quantize an analog signal and convert it into a digital signal, and converts the output of the first A/D converter into an analog signal. difference signal generating means for converting into a signal to obtain a difference signal between the first analog signal and the first analog signal input to the first A/D converter; and a switching means for switching between quantization of a second analog signal independent of the first analog signal.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.
FIG. 1 is a block diagram of an embodiment of the present invention, in which the first and second A/Rs each perform 3-bit quantization.
D converters 1 and 2, and a D/A converter 3 that converts the digital output of the A/D converter 1 into an analog value.
and a differential amplifier 4 with a gain of 1 (0 dB) to find the difference between the output of the D/A converter 3 and the analog signal input of the A/D converter 1, and the use of the second A/D converter 2 is switched. It is composed of a switching circuit 5. A/D
Converters 1 and 2 are parallel comparison type A/D converters each consisting of 2 ³ -1=7 comparators 6 and encoders 7, and the switching circuit 5 is connected to the input circuit and the reference voltage of the comparator 6. By switching in conjunction with the subtraction input voltage of the differential amplifier 4, it is possible to switch between 3-bit coarse quantization using two parallel circuits and 6-bit precise quantization using one circuit.

In FIG. 1, when the switching circuit 5 is connected to the a side as shown in the figure, the first analog signal 101 is converted to nE ₀ /8 (n is 1
The 3-bit outputs A ₁ , A ₂ ,
_A3 , and the second analog signal 102 passes through the differential amplifier 4 as it is and is sent to the A/D converter 2.
Similarly, it is quantized into 3-bit outputs B ₁ , B ₂ , and B ₃ . On the other hand, when the switching circuit 5 is connected to the b side, the output of the A/D converter 1 is converted to an analog signal 103 by the D/A converter 3; The lower limit value of each region is 1, that is, 0 and 7 threshold voltages. Therefore, the differential amplifier 4 calculates the difference between the analog signals 101 and 103, and the A/D converter 2 further quantizes this into a 3-bit digital signal, resulting in 6-bit quantization, and A ₁ ,A ₂ ,
A ₃ becomes the output of the upper 3 bits, and B ₁ , B ₂ , and B ₃ become the output of the lower 3 bits. At this time, the value of the resistance R of the switching circuit 5 is set to R=7× so that the interval between the threshold voltages of the A/D converter 2 is 1/8 of the threshold interval of the A/D converter 1. ((8r) is selected. With this configuration, one analog information It is possible to switch between 6-bit precise quantization of 2 analog signals and 3-bit coarse quantization of 2 analog signals, which has the effect of eliminating waste in terms of both weight and power consumption.

FIG. 2 is a block diagram of another embodiment of the invention, in which circuits that are the same as in FIG. 1 are designated by the same reference numerals. The difference between this circuit and FIG. 1 is that the switching circuit 8 switches only the input circuit of the A/D converter 2;
The differential amplifier 9 that calculates the difference between the output 103 of the D/A converter 3 and the input 101 of the A/D converter 1 outputs 16 dB (8 dB).
It is clear that the A/D converter 2 has a voltage gain of be.

The above embodiment deals with the case where the input analog signal is only for positive voltage, but even if the input analog signal is for positive and negative voltages, the analog output of the D/A converter 3 is the same as that of the A/D converter 1. A completely similar configuration is possible by setting the threshold value to an intermediate value. or,
Both A/D converters 1 and 2 are of parallel comparison type that performs 3-bit quantization, but A/D converters other than 3-bit parallel comparison type may be used, and two A/D converters may be used. The number of quantization bits of the converters does not necessarily have to be the same. Furthermore, the same configuration is possible even if three or more A/D converters are used instead of two,
Multiple coarse quantizations and one fine quantization can be switched and used. Note that switching between fine quantization and coarse quantization can be associated with input switching and sampling, so that the switching operation can be performed at high speed.

〔Effect of the invention〕

As explained in detail above, according to the A/D conversion circuit of the present invention, the A/D conversion circuit performs one precise quantization.
It has the effect of being able to switch between precise quantization and multiple coarse quantizations with almost the same circuit scale as a converter, and when used in artificial satellites, it has the advantage of reducing waste in terms of both weight and power consumption.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
The figure is a block diagram of another embodiment of the present invention, in which reference numbers 1 and 2 are A/D converters, and 3 is a D/D converter.
A converter, 4 and 9 are differential amplifiers, 5 and 8 are switching circuits, 6 is a comparator, and 7 is an encoder.

Claims (1)

[Claims] 1 At least two first and second A/Ds that quantize analog signals and convert them into digital signals.
a converter, and a difference signal generating means for converting the output of the first A/D converter into an analog signal to obtain a difference signal between the first analog signal and the first analog signal input to the first A/D converter. , switching means for switching the second A/D converter between quantization of the difference signal and quantization of a second analog signal independent of the first analog signal. An A/D conversion circuit characterized by: