Mixer's Datasheet PROBLEM
1)The input is IF or RF ?Is this for upconversion for downconversion or both? At the Typical Performance Data all the values for RF and LO as i understand referred to IF=30 MHz. Right? For example at the first line: LO(30.25MHz)-30MHz=0.25MHz(RF). But how is this possible that RF is smaller that IF? I am doing something wrong but i cannot understand.
2) I know for mixers that 1dB compression point is the maximum input power to have a linear equation between input and output. If the mixer is downconverter the input is RFpower if is upconverter the input is IFpower. At the left and up has some MAXIMUM RATINGS RFpowermax=50mwatt=17dbm and IFpowermax(P=I^2*R)=80mwatt=19dbm and the 1dbcompr.point of the mixer is 1dbm. What is going wrong?
I am beginner with RF electronic so forgive me for this stupid questions.
Kindly Regards
George1mixer.ZAD-6+.pdf
The IF is always the output. the other two sides are inputs, which are almost interchangeable but slight difference and the choice is limited by the maximum LO power input. RF input has the same range.
read Freq Mixer app notes for choice details..
The filter you add to IF output chooses whether you want lower or upper mix product. for step down or up conversion respectively.
Typically for mixers, especially double balanced ones such as this, the manufacturer does not specify overlapping R and I frequencies. In that case it's clear that for an upconverter I is input and R is output. For a downconverter R is input and I is output. For this mixer the ranges almost overlap - which is unusual. One thing I'll point out though is that if your signal extends to DC, you'll only get from the I port, both R and L are transformer coupled.
The absolute maximum rating can be considered damage threshold, which is higher than the compression point.
Also, operating at the P-1dB point will result in large distortions. How much below the P-1dB you will need to be will depend on your distortion requirement, generally though you will need to be 10+ dB below P1dB.
Hi SunnySkyGuy ! IF is input as i know when the mixer make an upconversion. When it makes a downconversion RF is the input right? I have read mini-circuits application notes they are very helpful!
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Hi pstuckey. I don't understand what do you mean overlapping? for example if IF=30MHz=constant the RF as i see here is lower.is this normal?
Yes it is higher than the compression point but this is a lot dmb higher. Is this normal? So 1dbcompoint =1dbm-10=-9dbm is the maximum input power if i don't want to have problems with the linearity? It seems to me very low :O
Kindly Regards
George
Almost any passive mixer, balanced or unbalanced, can be used as a up or down converter.
For upconverters it is typical that IF is the input and RF is the output. As the non-linear mixer generates two side bands and their harmonics over RF band, it is recommended to use a band-pass filter at RF output to obtain only the desired response.
The P-1 dB compression point means that the linear limit has been exceeded, and the conversion loss increased by 1dB. In upconverters a rule of thumb is that P-1 dB point at RF output occurs at ~ 7 dB less than LO input power. This is why e.g. Minicircuits offers several LO levels for their mixers, from ~ 3 dBm to 23 dBm. Diodes are selected for a particular LO input level,and the P-1 dB at RF output is ~7 dB lower.
For down converters, RF input may or may not be filtered to define conversion loss. The noise figure of a receiver with such mixer then differs: with a RF band-pass filter, NF is ~ 3 dB higher than for a mixer without it (SSB vers. DSB NF). Down converters also have a P-1dB linearity limit, also define by LO input.
Almost any passive mixer, balanced or unbalanced, can be used as a up or down converter.
For upconverters it is typical that IF is the input and RF is the output. As the non-linear mixer generates two side bands and their harmonics over RF band, it is recommended to use a band-pass filter at RF output to obtain only the desired response.
The P-1 dB compression point means that the linear limit has been exceeded, and the conversion loss increased by 1dB. In upconverters a rule of thumb is that P-1 dB point at RF output occurs at ~ 7 dB less than LO input power. This is why e.g. Minicircuits offers several LO levels for their mixers, from ~ 3 dBm to 23 dBm. Diodes are selected for a particular LO input level,and the P-1 dB at RF output is ~7 dB lower.
For down converters, RF input may or may not be filtered to define conversion loss.Can you please explain this with the 3db higher? I understand that with the SSB the receiver the NF will 3dB lower cause the other band is cutted. I am begginer so please explain...
Also the RF and LO frequencies at the Typical Performance Data are reffered for IF=30MHz. How is this possible the IF to be higher that the RF fre?
George
The *IF* port is (most generally) the one capable of DC to some high "RF" frequency as input or output ... when used as a phase detector, this will be a DC output, and this port will also accept DC control voltages (for 'modulation' and so forth)!
The LO and RF ports do not accept DC or low freqs as they have coupling using magnetic flux-linked transformers.
RF_Jim
Hi RF_Jim! Thanks for your advices. I have some basic knowledge of electronics and now i want to make a RF-System with microwaves devices (lna,mixer..) so i read about how these devices works , what is their specifications..but i don't analyze their electronic inside...
What you propose me to do if i want to be a good RF engineer?
George
"Practice practice practice."
Make plans, execute the plan, make mistakes then pick up the pieces and proceed anew once again!
It also helps to have some basic equipment, one does not need the latest to analyze a device such as an LNA or mixer, very basic test equipment picked up used can suffice ... recommend attending some hamfests in the area where one can pick up that kind of gear.
What matters is what is between your ears, your ability to deduce what is going on when things do not work as expected, then one learns a lot more than when things 'go right' ha ha ha ... experience is the best teacher.
Also, learn the Smith Chart, what it represents (constant Impedance circles as line lengths change the real and imaginary parts vary but rho stays the same!)
RF_Jim
Thanks bro i appreciate your advices!