Abstract A digital-to-analog converter circuit for converting digitized audio signals to analog form having improved phase characteristics and a reduced noise level while employing a less costly low-pass filter than conventional circuits. A digital-to-analog converter converts an analog signal, which has frequency components within a range lower than a first frequency, to analog form. A sample-and-hold circuit samples and holds the output of the digital-to-analog converter at a second frequency more than twice as high as the first frequency. Frequency components in the output of the sample-and-hold circuit above a third frequency between the first and second frequencies are phase inverted. The output of the sample-and-hold circuit and the output of the inverting circuit are summed and applied to a low-pass filter, the output of which provides the analog output from the circuit.
A digital-to-analog converter circuit comprising a digital-to-analog converter for converting into an analog audio signal within a range of effective signal frequencies lower than a first frequency; sample-and-hold means for sampling and holding an output signal of said digital-to-analog converter at a second frequency more than twice as high as said first frequency; means for phase inverting components in an output of said sample-and-hold means of a frequency higher than a third frequency between said first and second frequencies; and means for summing said output of said sample-and-hold means and an output of said inverting means.
Claim 2
Dependent Claim
96 words
A digital-to-analog converter circuit comprising a digital-to-analog converter for converting into an analog audio signal within a range of effective signal frequencies lower than a first frequency; sample-and-hold means for sampling and holding an output signal of said digital-to-analog converter at a second frequency more than twice as high as said first frequency; means for phase inverting components in an output of said sample-and-hold means of a frequency higher than a third frequency between said first and second frequencies; and means for summing said output of said sample-and-hold means and an output of said inverting means.
Claim 3
Dependent Claim
27 words
The digital-to-analog converter circuit as claimed in claim 1, further comprising a low-pass filter, an output signal of said summing means being supplied to said low-pass filter.
Claim 4
Dependent Claim
28 words
The digital-to-analog converter circuit as claimed in claim 1, wherein said phase inverting means comprises a high-pass filter and an inverter connected in series with said high-pass filter.