in the following equation and so forth belong to the part of the harmonic orders which will interfere with the signal therefore if the interfering harmonic orders are eliminated the snr value can be increased to increase the circuit performance the present invention adopts this principle to achieve the objective of harmonic rejection accordingly the following equation can be utilized to eliminate the harmonic orders from the above mentioned equation lo t the above mentioned equations v out t can completely filter out the third order harmonic same methods can be used to filter out the fifth order harmonic the seventh order harmonic the ninth order harmonic and so forth please refer to fig2 the function block diagram shows a harmonic rejecting mixing apparatus according to one embodiment of the present invention as shown in fig2 the harmonic rejecting mixing apparatus 200 comprises a mixing circuit 201 a first circuit 202 a second circuit 203 a third circuit 204 and a summation unit 205 the mixing circuit 201 further comprises a mixing unit 2012 for receiving a signal s and a f 0 and performing mixing of the signal s and the f 0 via the mixing unit 2012 to generate a signal s 1 the first circuit 202 further comprises a gain unit 2021 and a mixing unit 2022 for receiving the signal s and the 3f 0 and performing mixing of the signal s and the 3f 0 via the gain unit.