RF Mixer working mechanism

[wccheng]

Dear all,

I have read some paper discussing about the RF mixer. I have found that some of them working in the multiplication method. Some of them working as chopping method.

Actually, what is the different between two mechanisms? Could you introduce some books talking about this in detail?

Best Regards,

wccheng

 

[rittu]

Hi
If I am correct, in multiplier mode the LO signals are sinusoids with amplitudes such that it can switch the transistors from sat to linear region. In this case only multiplication of the RF signal frequency and the LO frequency occurs.
In the chopping mode the LO signals are square waves with amplitude close to supply voltage which can switch the transistors from sat to cutoff as a result the input RF frequency is multiplied by the fourier series of the square wave LO signal.
Other kind of mixer is subsampling mixer.
Some good books are " The design of CMOS RF IC" by Thomas Lee and "RF microelectronics" by Razavi
I hope this helps
Rittu

 

[wccheng]

Dear Rittu,

I am very thankful for your helping. Actually, what is the advantage and disadvantage between these two mechanisms?

Best Regards,

wccheng

 

[sunwiss]

Hi
Chopping method should be one type of multiplication. The classical chopping mixer is Gilbert cell, which topology is simple. Performance trade-off is good.
Multipling mixer often consists of many devices, which topology is complex. They often realize frequency conversion through current multiplicaion.

 

[wccheng]

Dear sunwiss,

Does any typical circuit is working in multiplication?

Best Regards,

wccheng

 

[CTT]

sunwiss,

multiplication also very noisy because most of its devices
are operating at the same time.

wccheng, you can refer to B. Gilbert's on translinear loop
for multiplication with BJTs.

CTT