776ft
Newbie level 6
harmonic reject mixer
I am working on harmonics reject mixer, down-convertion, working from 150kHz to 30MHz, using 6 of 8 LOs(pi/4 from each other, we use 0, 45°, 90°, 180°, 225°, and 270° LO) and us 0.7 as the ratio close to 1/√2 (0.707) with 1% error,
I used pss+pxf simulation, when the LO freq is 1M, the harmonic rejection ratio are: H1/H3=55.6dB, H1/H5=60dB, (match well with the hand calculation),
But when the LO is set to 30MHz, the ratio become H1/H3=48dB, H1/H5=49dB, the LO is ideal LO(50% duty cycle, rise and falling edge is 0.01T), from the equation of the harmonics reject it should be frequency independent, but it do decrease with the frequency, I don't know why.
Can anybody who has the similar expirence in Harmonics reject mixer design tell me why or give me some idea about it? thanks a lot.
I am working on harmonics reject mixer, down-convertion, working from 150kHz to 30MHz, using 6 of 8 LOs(pi/4 from each other, we use 0, 45°, 90°, 180°, 225°, and 270° LO) and us 0.7 as the ratio close to 1/√2 (0.707) with 1% error,
I used pss+pxf simulation, when the LO freq is 1M, the harmonic rejection ratio are: H1/H3=55.6dB, H1/H5=60dB, (match well with the hand calculation),
But when the LO is set to 30MHz, the ratio become H1/H3=48dB, H1/H5=49dB, the LO is ideal LO(50% duty cycle, rise and falling edge is 0.01T), from the equation of the harmonics reject it should be frequency independent, but it do decrease with the frequency, I don't know why.
Can anybody who has the similar expirence in Harmonics reject mixer design tell me why or give me some idea about it? thanks a lot.