A/D conversion apparatus and a radio apparatus

An A/D conversion apparatus, comprising:

• subtraction means for subtracting a first signal from a second signal, and for outputting a third signal as a subtraction result;
• first conversion means for converting the third signal into two digital signals whose frequencies are orthogonal to each other and are different from a frequency of the second signal;
• and
• second conversion means for converting the two digital signals to two analog signals, and for adding the two analog signals as the first signal whose frequency is nearly equal to the frequency of the second signal;
• wherein said second conversion means includes a plurality of current sources, a filter means for calculating a number of use of each of the plurality of current sources, and a selection means for selecting the current sources having a lower value of the number of use, the number of selected current sources corresponding to each value of the two digital signals.

A radio apparatus, comprising:

• receiving means for receiving a harmonic signal;
• subtraction means for subtracting a first signal from a second signal as the harmonic signal, and for outputting a third signal as a subtraction result;
• first conversion means for converting the third signal into a digital signal of predetermined frequency different from a frequency of the second signal;
• second conversion means for converting the digital signal into an analog signal of a frequency nearly equal to the frequency of the second signal, and for supplying the analog signal as the first signal to said subtraction means;
• wherein said second conversion means includes a plurality of current sources, a filter means for calculating a number of use of each of the plurality of current sources, and a selection means for selecting the current sources having a lower value of the number of use, the number of selected current sources corresponding to the value of the digital signal;
• and
• demodulation means for demodulating the digital signal output from said first conversion means.

A radio apparatus, comprising:

• receiving means for receiving a harmonic signal;
• subtraction means for subtracting a first signal from a second signal as the harmonic signal, and for outputting a third signal as a subtraction result;
• first conversion means for converting the third signal into two digital signals whose frequencies are orthogonal to each other and are different from a frequency of the second signal;
• second conversion means for converting the two digital signals into two analog signals, and for adding the two analog signals as the first signal whose frequency is nearly equal to the frequency of the second signal;
• wherein said second conversion means includes a plurality of current sources, a filter means for calculating a number of use of each of the plurality of current sources, and a selection means for respectively selecting the current sources having a lower value of the number of use, the number of selected current sources corresponding to each value of the two digital signals;
• and
• demodulation means for demodulating the two digital signals output from said first conversion means.

An A/D conversion apparatus, comprising:

• a subtractor configured to subtract a first signal from a second signal, and to output a third signal as a subtraction result;
• a first conversion unit configured to convert the third signal into a digital signal of predetermined frequency different from a frequency of the second signal;
• and
• a second conversion unit configured to convert the digital signal into an analog signal of a frequency nearly equal to the frequency of the second signal, and to supply the analog signal as the first signal to said subtractor;
• wherein said second conversion unit includes a plurality of current sources, a filter configured to calculate a number of use of each of the plurality of current sources, and a selection unit configured to select the current sources having a lower value of the number of use, the number of selected current sources corresponding to the value of the digital signal.

An A/D conversion apparatus, comprising:

• a subtractor configured to subtract a first signal from a second signal, and to output a third signal as a subtraction result;
• a first conversion unit configured to convert the third signal into two digital signals whose frequencies are orthogonal to each other and are different from a frequency of the second signal;
• and
• a second conversion unit configured to convert the two digital signals to two analog signals, and to add the two analog signals as the first signal whose frequency is nearly equal to the frequency of the second signal;
• wherein said second conversion unit includes a plurality of current sources, a filter configured to calculate a number of use of each of the plurality of current sources, and a selection unit configured to select the current sources having a lower value of the number of use, the number of selected current sources corresponding to each value of the two digital signals.

A radio apparatus, comprising:

• a receiver configured to receive a harmonic signal;
• a subtractor configured to subtract a first signal from a second signal as the harmonic signal, and to output a third signal as a subtraction result;
• a first conversion unit configured to convert the third signal into a digital signal of a predetermined frequency different from a frequency of the second signal;
• a second conversion unit configured to convert the digital signal into an analog signal of a frequency nearly equal to the frequency of the second signal, and to supply the analog signal as the first signal to said subtractor;
• wherein said second conversion unit includes a plurality of current sources, a filter configured to calculate a number of use of each of the plurality of current sources, and a selection unit configured to select the current sources having a lower value of the number of use, the number of selected current sources corresponding to the value of the digital signal;
• and
• a demodulation unit configured to demodulate the digital signal output from said first conversion unit.

A radio apparatus, comprising:

• a receiver configured to receive a harmonic signal;
• a subtractor configured to subtract a first signal from a second signal as the harmonic signal, and to output a third signal as a subtraction result;
• a first conversion unit configured to convert the third signal into two digital signals whose frequencies are orthogonal to each other and are different from a frequency of the second signal;
• a second conversion unit configured to convert the two digital signals into two analog signals, and to add the two analog signals as the first signal whose frequency is nearly equal to the frequency of the second signal;
• wherein said second conversion unit includes a plurality of current sources, a filter configured to calculate a number of use of each of the plurality of current sources, and a selection unit configured to respectively select the current sources having a lower value of the number of use, the number of selected current sources corresponding to each value of the two digital signals;
• and
• a demodulation unit configured to demodulate the two digital signals output from said first conversion unit.