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How to sum up two high frequency signals?

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sahar

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If you have to sum up two HF signals, which do not come with very high internal impedance, what will you do not to disturb the sum?
 

Hi,
You can use a resistive combiner.
Theses devices are totally resistive, they are linear (they do to generate harmonics), high bandwidth (a lot of GHz), you can handle power, etc. Your sigal at the output will only suffer a little of attenuation but if you know this attenuation (by S parameter characterization of your resistive combiner, you only need to know S21 dB ) you can compensated the sum of your signals at the output.
Best regards.
 

you can summing two hf signals by using a NE592 IC , i tested it to summing two signals one in 6Mhz and 5Mhz . if u need a circuit design send an email to kngemad@yahoo.com
 
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    lucky8

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I think I should add some points. Actually it is not a board and I am not building it, so I can not use some ICs. It is in the IC design level.
Actually I used sampling method but two signals load each other and I dont get the accurate sum or subtraction. Is there any idea?
 

sahar said:
I think I should add some points. Actually it is not a board and I am not building it, so I can not use some ICs. It is in the IC design level.
Actually I used sampling method but two signals load each other and I dont get the accurate sum or subtraction. Is there any idea?
Click to expand...

The best way to add two high frequency signals on chip is to perform it in current domain. The signals can be converted into current using a very linear transconductance block (degenerated MOS/BJT diff pair , BJT pair is preferred for higher frequencies if available). Then by simply tying the output nodes of the two transconductors together , the signals can be added/subtracted easily in current domain.
The implementation may vary depending on your application, but this should work...
Hope this helps.

Bharath
 

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    sahar

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if u wana add high frequency signal ,both signal should b 100 percent identical ,u cant add arbitraray signal ,so there are many method we use to add high frequency using ic ad8130 in aplication u wll find a adder circuit using this u can add other wise u can use power combiner to add both of them so using power combiner the singnals hould b identical 100 percent if they dont u cant get the maxipower at the output so u need phase shifter to adjust at one node of input signal and wire length count as wll :) i think phase shifter is best u can use one phase shifter at the end input combiner and adjust it when ever u got the maximum power at the ouput port :) best of luck
 

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