Help : RF to DC converters

[sbhalerao]

Hi to all,
I have previously posted a request for help on hte same topic and I did get some great replies!! Thanks to all you guys!!!
My basic approac remains as follows:-
I take the RF power using a microstrip patch antenna, rectify and get DC power to run a sensor node...
Till now I have been able to get around 0.2 V at the output and I need ~3 V.
I am receiving RF power through the antenna and rectifying using a Agilent Zero bias Schottky diode. I have paid due attention to impedance matching.. Again very low power is needed at output (around 1 microwatt) - so all I want is 3 V and very less current .. I want help on the following issues:-
1) Could a high Q circuit between antenna and rectifier circuit help to give desired voltage multiplication???
2) I thought of using a dc-dc charge pump... Can such a charge pump be used when supply voltage toit is only 0.2 v?? (I have seen charge pumps with supply voltage of around 1.2 V).. Again the problem is dc biasing as I am powering the sensor node with the RF energy!!!
Thanking you in advance.
Pheonix

 

[seadolphine2000]

Take the DC output (0.2V) and use a compartor circuit (Op-Amp) with the gnd as reference. when your output(0.2V) is above the gnd(0V), you will get an output from the Op-Amp equals VCC (5V).

 

[IanP]

Here you can find examples of convertion from 0.3V to 3V at 1mA:
ftp://ftp.sii.co.jp/pub/ic/speed_dt/dt_sht_e/power/S882Z_E.pdf
So your task will be to boost-up input voltage from 0.2 to 0.3 (if possible???) ..
Regards,
IanP

 

[divan]

you cann't take this way if you need power more than few uW.
if you need 2-3 V @ 2-3 uA you have feed from antenna not at 50 ohm but at highter impedance point , for ex at 200-300 ohm - closely to the edge. And You can use diode voltage multiplier, search google for reference, try *rectenna* or *RFID Tag*
Agilent have some appnotes about this, as i remember.

 

[biff44]

Yes, I agree with the multiplying diode. First get the impedance up as high as you can so there is a lot of RF voltage available (but less current), then use multiple diodes to multiply the voltage.

 

[sbhalerao]

you cann't take this way if you need power more than few uW.
if you need 2-3 V @ 2-3 uA you have feed from antenna not at 50 ohm but at highter impedance point , for ex at 200-300 ohm - closely to the edge. And You can use diode voltage multiplier, search google for reference, try *rectenna* or *RFID Tag*
@gilent have some appnotes about this, as i remember.

You are correct!!! That's what I intend to do... I am constructing a rectenna and I have gone through the Agilent application notes... I want to make a rectenna which works at 2.4 GHz and I want onlya few uW (even 0.5 uW will do!!!) - but I need pretty high voltage (around 1 or 2 V) , the current in uA is acceptable...
My real problem is the design of the antenna.. I am *not* particularly comfortable working with antennas.. So could you tell me how I could get more voltage ( I understand this has to do with the impedance atwhich antenna is being fed).. I would be glad if you could elaborate more on this and provide some links ( I read Kraus, Milligan and Carr - but did not find techniques of getting higher voltages)...
Could I use a balun in this case?? I mean I could use it as a tranformer (to get higher voltage just after antenna).. I would like to know if balun can be made small enough to be used in a RFID tag??
Thanking you for all your help especially divan...
I would also like to know how I could get a suitable antenna (My choice is a microstrip antenna)
Regards..
Pheonix..

 

[myebook]

Hi

My project is about rectenna, too. I can get 1.2 v from my design. For getting high voltage there is no any coverter, you just should increase the efficiency of your system, following tips may can help you:
1- Use a high gain microstrip antenna around 6 dBi
2-In the resonase frequeny f the antenna desin a matched rectifier.
3-Use two BSF in two sides of the diode to eliminate all the RF (in the load side) and harmonics of the fundamental frequency (in antenna side).

I popose that at first stage do not use the antenna, insteade, a signal generator at the frequncy that is matched with the rectifier can help you to test the rectifier.

Regards

 

[Maverickmax]

Hi

I am interested in your project. Would you kindly share your project details with us?

MM

 

[faroo56]

it is a very interesting project, I also work with Wireless nodes which i am thinking to use Energy Harvestinmg to power the nodes.
There is a company who does make this kind of product they demo their stuff to us and they could power LED by RF energy harvesting.
I will send you the name of the company as soon as i remember their name.

 

[Maverickmax]

That would be brillant. I look forward to receive details. Please email to manozjoshi@gmail.com

Thank you

MM

 

[faroo56]

here is a very nice paper regarding this.

 

[bingjiang99]

I have been working on the similar stuff for a while. I am pretty sure that this can work (my one did work great). Several things need to be paid attention: 1) Your impedance matching network didn't work well. The initial guss of the matching should start with the spice model from datasheet. 2) the rectifier structure. You can find a lot of RFID stuff from IEEE.

Good luck,

 

[myebook]

Hi Sbhalerao,

My project in MSE was rectenna. The voltageyou can get is very low, in most of the papers you can see the voltage of around 2v. the most critical point is the matching betwen the elements of the rectenn: antena and diode+filter, load and diode+filter. If you design multi section matching circuit you will have a broadband circuit that can help you in matching.

Good Luck

Added after 1 minutes:

Also a high gain antenna can help you.

 

[sriniv1422]

Hi ,

Iam also working on the rectenna design for livestock identification.

Could any one of you let me know what is the correct way of doing impedance matching and finding out the Rin and Cin of the voltage multiplier circuit.

I am having problems in trying to simualte the input impedance of this multiplier circuit.

There is a very recent paper titled " Power rectifier analysis and design".
Jari pascal.

IEEE transactions on circuits and systems -- vol52 ,No12 ,Dec 2005


thanks
srinivasan.

 

[myebook]

Dear Everybody,

Harmonic rejection property in antennas can miaturize the rectenna system and because of eliminating thbe BPF between the antenna and the diode the efficiency will be increased. My IEEE paper on this regard is in the attachment.

 

[caihalo]

hello everybody especially to sbhalerao. Have you complete design your rectenna which got the DC output 1 volt.? im here to know how your design because im also design the rectenna. So please help me and anybody who success in built the rectenna which got 1volt DC output please inform at my email
HALO_bandit99@yahoo.com or at my ym HALO_bandit99.
tq a lot...

 

[myebook]

you can use the diodes in series to increase the output voltage. take a look at page 5 of the attached paper from Itoh, they got 1V output!

 

[myebook]

A simple tutorial to start schmatic of ADS:

 

[caihalo]

hello
to myebook...
in your rectifying circuit, what type of the schottky diode that have you use in your rectenna?

Added after 1 hours 16 minutes:

anybody can share their rectenna specification which operate at 2.45GHZ and can get the DC output 1volt or more. tq

 

[myebook]

the diode introduced in the previysely attached paper fro Itoh.