Data conversion device

Details Data conversion device Data conversion device

1999-04-27

2001-06-26

Williams, Howard L. (Department: 2819)

Coded data generation or conversion

Analog to or from digital conversion

Digital to analog conversion

C341S155000, C341S147000, C341S152000

Reexamination Certificate

active

06252533

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data conversion device that is used to synthesize digital data composed of two or more components, such as a DTMF (dual-tone multi-frequency) signal used in a push-button (i.e. tone-dialing) telephone, into a single analog signal.
2. Description of the Prior Art
Conventional examples of such data conversion devices are shown in
FIGS. 1 and 2
.
FIGS. 1 and 2
are block diagrams of conventional data conversion devices that synthesize 1 kHz digital data
20
, 10 kHz digital data
21
, and 100 kHz digital data
22
into an analog signal OUT.
In the conventional data conversion device shown in
FIG. 1
, the 1 kHz digital data
20
is converted into an analog signal by a D/A (digital-to-analog) converter
23
. The analog signal output from the D/A converter
23
is then amplified by an amplifier circuit
26
by a predetermined amplification factor and fed to an adder circuit
29
. The 10 kHz digital data
21
is converted into an analog signal by a D/A converter
24
. The analog signal output from the D/A converter
24
is then amplified by an amplifier circuit
27
by a predetermined amplification factor and fed to the adder circuit
29
. The 100 kHz digital data
22
is converted into an analog signal by a D/A converter
25
. The analog signal output from the D/A converter
25
is then amplified by an amplifier circuit
28
by a predetermined amplification factor and fed to the adder circuit
29
. The adder circuit
29
, by adding together the individual analog signals output from the amplifier circuits
26
,
27
, and
28
, synthesizes those signals into a single analog signal OUT.
On the other hand, in the conventional data conversion device shown in
FIG. 2
, the 1 kHz digital data
20
is, while it is digital data, multiplied by a multiplier
30
so as to attain a predetermined amplification factor, and is then fed to an N-bit adder
33
. The 10 kHz digital data
21
is multiplied by a multiplier
31
so as to attain a predetermined amplification factor, and is then fed to the N-bit adder
33
. The 100 kHz digital data
22
is multiplied by a multiplier
32
so as to attain a predetermined amplification factor, and is then fed to the N-bit adder
33
. The N-bit adder
33
adds together the digital data output from the multipliers
30
,
31
, and
32
, and feeds the sum to a D/A converter
34
. The D/A converter
34
converts the digital data fed thereto into an analog signal so as to output a single analog signal OUT. In this way, either of the data conversion devices shown in
FIGS. 1 and 2
synthesizes digital data composed of three components
20
,
21
, and
22
of different frequencies into a single analog signal, while maintaining the frequencies of the components, and outputs the obtained single analog signal to a communications network, bus, or the like.
However, the conventional data conversion devices shown in
FIGS. 1 and 2
have the following disadvantages. When digital data composed of a plurality of components is synthesized, the data conversion device shown in
FIG. 1
requires amplifier circuits
26
,
27
, and
28
to attain a predetermined amplification factor for each signal component, and the data conversion device shown in
FIG. 2
requires multipliers
30
,
31
, and
32
one for each signal component. Thus, these conventional data conversion devices require either large-scale hardware if their function is realized on a hardware basis or large-scale software if their function is realized on a software basis.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a data conversion device that requires only small-scale hardware to convert digital data composed of two or more components into a single analog signal.
To achieve the above object, according to the present invention, a data conversion device for synthesizing digital data composed of two or more components (of which each consists of a series of one-bit digital data) so as to output a single analog signal is provided with: a switch circuit for selecting one of the components of the digital data at a time by dividing a predetermined period into intervals having predetermined lengths of time in accordance with a select signal; a timing generator for generating the select signal; a current feeding circuit for feeding a current that flows in one or another direction in accordance with the output of the switch circuit; and a current-to-voltage conversion circuit for converting the current into a voltage so as to produce an analog signal.
In this data conversion device, in accordance with the select signal output from the timing generator, the switch circuit selects one of the components of the digital data at a time by dividing a predetermined period into intervals having predetermined lengths of time. The data selected by the switch circuit is fed to the current feeding circuit. The current feeding circuit, in accordance with the data fed thereto, selects the direction of the current it outputs. The current output from the current feeding circuit is converted by the current-to-voltage conversion circuit into a voltage so as to be made into an analog signal. Thus, this data conversion device requires only a smaller-scale circuit than a conventional data conversion device, because it does not require a multiplier or amplifier circuit for each of the components of the digital data.


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patent: 5872603 (1999-02-01), Ohsawa
patent: 6052076 (2000-04-01), Patton, III et al.

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