Analog to digital conversion apparatus
View Patent ↗An up-converter 124 frequency-up-converts an analog signal Sm. A down-converter 121 frequency-down-converts analog signal Sm. A signal selection block 125 selects one of the frequency-up-converted signal Sfu and frequency-down-converted signal Sfd. The signal Se selected by the signal selection block 125 is provided to the primary winding of a transformer 127 . A signal induced in the secondary winding of the transformer 127 is provided to an A/D converter 128 to produce a digital signal Dm. For example, if the analog signal Sm has DC or a low frequency close to DC, the signal Sfu is selected as the signal Se. If the analog signal Sm does no have DC nor a low frequency close to DC, the signal Sfd is selected as the signal Se.
1. An analog to digital conversion apparatus comprising:
an analog to digital converter;
a low bandpass filter for limiting a band of an input analog signal as satisfying a Nyquist condition defined by a sampling frequency of the analog to digital converter;
an up-converter for frequency-up-converting an output signal of the low bandpass filter; and
a transformer receiving an output of the up-converter at the primary winding and for providing the A/D converter with an analog signal induced at the secondary winding wherein the frequency-up-conversion is conducted as an alias arises at the A/D converter corresponds to the output signal of the low bandpass filter.
2. The analog to digital conversion apparatus as recited in claim 1 further comprising:
a down-converter for frequency-down-converting the input analog signal; and
a signal selection block for selecting one of the output signals of the up-converter and down-converter to provide it to the transformer.
3. The analog to digital conversion apparatus as recited in claim 1 wherein the up-converter conducts the frequency-up-conversion by multiplying the input analog signal by a local signal of which frequency is the same as the sampling frequency of the A/D converter.
4. The analog to digital conversion apparatus as recited in claim 2 wherein the up-converter conducts the frequency-up-conversion by multiplying the input analog signal by a local signal of which frequency is the same as the sampling frequency of the A/D converter.
5. A signal analyzer comprising:
an analog to digital converter;
a digital signal processor connected to the analog to digital converter for enabling measurements of a signal under test,
a low bandpass filter for limiting a band of an input analog signal as satisfying a Nyquist condition defined by a sampling frequency of the analog to digital converter;
an up-converter for frequency-up-converting an output signal of the low bandpass filter; and
a transformer receiving an output of the up-converter at the primary winding and for providing the A/D converter with an analog signal induced at the secondary winding wherein the frequency-up-conversion is conducted as an alias arises at the A/D converter corresponds to the output signal of the low bandpass filter.
6. The signal analyzer as recited in claim 5 further comprising:
a down-converter for frequency-down-converting the input analog signal; and
a signal selection block for selecting one of the output signals of the up-converter and down-converter to provide it to the transformer.
7. The signal analyzer as recited in claim 5 wherein the up-converter conducts the frequency-up-conversion by multiplying the input analog signal by a local signal of which frequency is the same as the sampling frequency of the A/D converter.
8. The signal analyzer as recited in claim 6 wherein the up-converter conducts the frequency-up-conversion by multiplying the input analog signal by a local signal of which frequency is the same as the sampling frequency of the A/D converter.