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How to block RF signal?

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shaikss

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Hi,

I have designed two rectifier topologies. One topology works well and provides good efficiency for voltage range 600mV to 800mV. The other topology provides better efficiency for 850mV to 1.2V. Now, I want to integrate these two topologies by sensing the input/output voltage/current.

If I sense the output voltage, I can know the input voltage range. So, depending on this, I can enable either of the above topologies.

When I enable any of the above topologies, I should be able to block/cut the RF signal going to another topology as the same RF signal is going to both topologies.

I have attached two topologies.

How can I do this?
 

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jiripolivka

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If you need to block RF at the output point, you can best use a low-pass filter there. One capacitor alone forms a RC integrator circuit with the source resistance (your rectifier), so use the largest suitable value.
 

shaikss

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If you need to block RF at the output point, you can best use a low-pass filter there. One capacitor alone forms a RC integrator circuit with the source resistance (your rectifier), so use the largest suitable value.

I want to block RF signal to other topology at the input end but not at the output end.
 

albbg

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You can use an RF switch. Just connect the two "RF-" toghether and route the two "RF+" to the two outputs of a SPDT switch with the common connected to the antenna (or to your input sensor).
 

albbg

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So do the same at the input. As you block the RF signal, what then can your circuit rectify?

I've understood he wants supply only one of the two rectifier at a time, depending from the rectified output voltage. Then at a given instant only one of the two has to be supplied by the RF signal while the other one will be disconnected from the RF input (that is the RF to it will be blocked). That's why I suggested the use of a switch (that can be controlled by the output voltage)
 

shaikss

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I've understood he wants supply only one of the two rectifier at a time, depending from the rectified output voltage. Then at a given instant only one of the two has to be supplied by the RF signal while the other one will be disconnected from the RF input (that is the RF to it will be blocked). That's why I suggested the use of a switch (that can be controlled by the output voltage)

I tried to use SPDT switch using NMOS. I do see some negative voltage for the other topology. The important thing is that I am designing rectifier for passive tag. So, I don't have any voltage source except the rectified dc voltage source. So, I need to go for SPDT switch using PMOS. But SPDT switch with PMOS is throwing issues.

PS: 2.png is the circuit I tested the SPDT switch using NMOS and 1.png is the corresponding waveform. I don't understand how to avoid those negative voltages in 1.png. 3.png is the waveforms which I tested my integrating the complete rectifier architecture. Here, 4T_out is the rectifier output which I have enabled. 5.png is the waveforms of SPDT switch using PMOS. 6.png is the test circuit for SPDT switch using PMOS.
 

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albbg

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I've to give a better look to your simulation and circuit; it seems that only the negative halfwave is passing through the NMOS.
However I don't think you really need the lower side mosfets. You could directly connect togehter rf-_en and rf-_enb to rf_en-
 

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