Industry standards for RF and LO leakage in mixers
I would like to consult you guys, what are the industry std for the RF and LO leakge for a mixer? I remember that the RF leakage is prefered to be ard 20-30dB loss rite? whatabt the LO part? If I have LO leakage value which is less than -20dB, is that satisfactory. If the RF leakge value is less than -20dB, from my knowledge apart from a band pass filter, what could be the additional factors that could add to this?
Thanks
It depends on the desired signal level through the mixer and the wanted carrier to interference (C/I) ratio. The RF leakage tracks the input RF level. 35 to 40 dBc is achievable. The LO leakage is at fixed level so it depends on the desired output signal level. With a LO of 0dB, and LO rejection of 40dB, the RF signal would have to be 0 dBm to maintain a 40 dBc. If the RF signal is lower, then the LO leakage must improve. With self calibation circuits, better mixer performance is possible.
perhaps you mean "isolation" rather than "leakage". The Leakage is another phenomena.
Isolation:
For receiver's down conversion mixer the LO isolation into R and I port may be more important than RF isolation into L and I port.
The L to I Iso is important because the strong signal level impact into IF Amplifier and may saturate it, also if IF Ampli work at far frequencies. To prevent this, a filter between IF port and IF amplifier is suggested.
The L to R Iso is important because the (close or far) phase noise of LO pass trough and come into R port, then it will be converted; this add an extra noise to the receiver.
The Industry standard typical values depends on the mixer bandwidth:
Look for data sheets of Miteq or Marky Mixers.
To give a rough idea, narrowband mixers may have LtoI and LtoR Iso 25 dB or more, while wideband mixer have LtoI and LtoR Iso 15 dB.
Leakage:
The leakage is the LO radiation. Often non specified into data sheets, it's non negligible. Mixers with hermetic chassis and without field replaceable connectors have lowest leakage.
Hi Mr Sergio.
Sorry but I'm confused by ur explanation, so are you saying that the ioslation and leakage actually mean the same meaning?
So does that means that if I'm looking for a RF leakge, I'm should be doing a L to R iso? when i'm looking for a LO leakage, it ,means that I shold be doing a L to I iso? So if I'm connecting a RF to port 1 of the VNA & port 2 to IF, so I'm would be doing a R to I iso instead?
You mentioned the down conversion only, how about the up conversion part?
Hi,
From my limited knowledge, when we say RF or IF leakge, it actually means that the amount of the RF and LO power being "leaked" into IF port. Does that means my statement is incorrect?
dear evoplus,
of course you may call the cross coupling between Mixer port as you prefere.
I was interested to tell that there is another phenomena that happen "on air". It's the radiated signal from the mixer.
In any case, if you use VNA , pay attention to levels. LO port shoud be driven with an appropriate level that may be difficult to acheive from a VNA.
usually Isolation don't need to be known whit low uncertainty; so a signal generator and the SA may be more useful than VNA.
I learn this part ,Thanks
It looks like the terminology was wrong. If we are talking about mixer there usually term isolation used. As better the isolation between all ports as better the mixer. Numbers about 25-30 dB are good and about 40 are excellent. Term leakage usually used for LO leakage to the input of the receiver. This numbers depends heavily on receiver topology and probably the most critical for direct conversion receivers.