Post by thread:[EE]: Rectifying 2.4Ghz "wifi" to give DC output?

On Fri, 04 Feb 2005 10:47:56 -0500, Marc Nicholas <spam_OUTmarcTakeThisOuTgeekythings.com> wrote: > Can anyone give me some guidance on a *simple* circuit for detecting 2.4Ghz > microwave (Wifi etc.) and providing DC output? It wouldn't have to be > terribly sensitive and I'd prefer it to be pretty passive :-) There was just such a project on Slashdot yesterday: http://neil.moon-beam.com/users/kris/index.htm Alex

On Fri, 04 Feb 2005 10:47:56 -0500, you wrote: >Can anyone give me some guidance on a *simple* circuit for detecting 2.4Ghz >microwave (Wifi etc.) and providing DC output? It wouldn't have to be >terribly sensitive and I'd prefer it to be pretty passive :-) A suitably fast diode detector should do the trick - not sure if normal schottky diodes are fast enough, but suitable microwave diodes shouldn't be hard to find. Can't be too difficult - see http://neil.moon-beam.com/users/kris/index.htm

That's what prompted the question -- there must be a relatively simple tunnel diode circuit that can be used. But there's no technical details or schematics on that site. I also thought about using one of MAXIM's tiny (TSOC or SOT23) ISM band downconverters, and then smoothing out their still AC output with rectifier/caps. -marc On 2/4/05 10:59 AM, "Alex Harford" <.....harfordKILLspam@spam@gmail.com> wrote: {Quote hidden}> On Fri, 04 Feb 2005 10:47:56 -0500, Marc Nicholas <marcKILLspamgeekythings.com> > wrote: >> Can anyone give me some guidance on a *simple* circuit for detecting 2.4Ghz >> microwave (Wifi etc.) and providing DC output? It wouldn't have to be >> terribly sensitive and I'd prefer it to be pretty passive :-) > > There was just such a project on Slashdot yesterday: > > http://neil.moon-beam.com/users/kris/index.htm > > Alex

On Fri, 4 Feb 2005, Marc Nicholas wrote: > That's what prompted the question -- there must be a relatively simple > tunnel diode circuit that can be used. But there's no technical details or > schematics on that site. If you want go/no go you can use a microwave bipolar transistor polarised into class B as active detector. This works well. I used 2SC2570 (ft=5GHz). The base was a lambda/4 wire stub (~6cm at your wavelength) and the collector was decoupled to get dc. The device will react to all 2.4GHz sources, such as microwaves, phones and video/audio links. There is also a 'microwave sensor' that uses a LM358 opamp (whose input stage apparently rectifies microwaves to some extent). If you want to measure I would look at Analog's log-amps which can be had for as little as $7 in ones and accept rf input directly at your frequency, providing db-proportional output. Imho, without using a band limiting circuit and a spectrum analyzer the output from your meter will not mean much (unless you are trying to optimize an antenna in 1:1 receive mode). There are a lot of sources at and around that frequency band. good luck, Peter

check this out: http://home.wanadoo.nl/erwin.gijzen/wifiswr/ Also, look for another DIY SWR meter. I can't find it now, but all it takes is a microwave diode and you get DC, which you amplify later and get a nice DC reading. hjf On Fri, 04 Feb 2005 11:36:31 -0500, Marc Nicholas <.....marcKILLspam.....geekythings.com> wrote: {Quote hidden}> That's what prompted the question -- there must be a relatively simple > tunnel diode circuit that can be used. But there's no technical details or > schematics on that site. > > I also thought about using one of MAXIM's tiny (TSOC or SOT23) ISM band > downconverters, and then smoothing out their still AC output with > rectifier/caps. > > -marc > > > On 2/4/05 10:59 AM, "Alex Harford" <EraseMEharfordspam_OUTTakeThisOuTgmail.com> wrote: > > > On Fri, 04 Feb 2005 10:47:56 -0500, Marc Nicholas <marcspam_OUTgeekythings.com> > > wrote: > >> Can anyone give me some guidance on a *simple* circuit for detecting 2.4Ghz > >> microwave (Wifi etc.) and providing DC output? It wouldn't have to be > >> terribly sensitive and I'd prefer it to be pretty passive :-) > > > > There was just such a project on Slashdot yesterday: > > > > http://neil.moon-beam.com/users/kris/index.htm > > > > Alex > > -

---------- Forwarded message ---------- Date: Fri, 4 Feb 2005 20:49:06 +0200 (IST) From: Peter L. Peres <@spam@plpKILLspamplp.home.org> To: Microcontroller discussion list - Public. <KILLspampiclistKILLspammit.edu> Subject: Re: [EE]: Rectifying 2.4Ghz "wifi" to give DC output? >was a lambda/4 wire stub (~6cm at your wavelength) and the collector That is of course ~3cm at your wavelength. Peter

part 1 1642 bytes content-type:TEXT/PLAIN; charset=X-UNKNOWN; format=flowed (decoded quoted-printable) Where on earth can one buy suitable microwave diodes in small qty? :-( -marc On Fri, 4 Feb 2005, [ISO-8859-1] Hern�n Freschi wrote: {Quote hidden}> check this out: http://home.wanadoo.nl/erwin.gijzen/wifiswr/ > Also, look for another DIY SWR meter. I can't find it now, but all it > takes is a microwave diode and you get DC, which you amplify later and > get a nice DC reading. > > hjf > > > On Fri, 04 Feb 2005 11:36:31 -0500, Marc Nicholas <RemoveMEmarcTakeThisOuTgeekythings.com> wrote: >> That's what prompted the question -- there must be a relatively simple >> tunnel diode circuit that can be used. But there's no technical details or >> schematics on that site. >> >> I also thought about using one of MAXIM's tiny (TSOC or SOT23) ISM band >> downconverters, and then smoothing out their still AC output with >> rectifier/caps. >> >> -marc >> >> >> On 2/4/05 10:59 AM, "Alex Harford" <spamBeGoneharfordspamBeGonegmail.com> wrote: >> >>> On Fri, 04 Feb 2005 10:47:56 -0500, Marc Nicholas <TakeThisOuTmarcEraseMEspam_OUTgeekythings.com> >>> wrote: >>>> Can anyone give me some guidance on a *simple* circuit for detecting 2.4Ghz >>>> microwave (Wifi etc.) and providing DC output? It wouldn't have to be >>>> terribly sensitive and I'd prefer it to be pretty passive :-) >>> >>> There was just such a project on Slashdot yesterday: >>> >>> http://neil.moon-beam.com/users/kris/index.htm >>> >>> Alex >> >> --

On Fri, 4 Feb 2005, Peter L. Peres wrote: > If you want to measure I would look at Analog's log-amps which can be had for > as little as $7 in ones and accept rf input directly at your frequency, > providing db-proportional output. These a MSOPs, so tiny...which will be good coupled with the PIC10F and a bunch of SMD LEDs for level. :-) Thanks! -marc

directv is very popular nowadays... and all those antennas have LNBs with just the kind of diode you need. so you could climb to your neighbour's roof and... oh you said BUY. never mind. ;) hjf On Fri, 4 Feb 2005 13:57:23 -0500 (EST), Marc Nicholas <RemoveMEmarcTakeThisOuTgeekythings.com> wrote: {Quote hidden}> Where on earth can one buy suitable microwave diodes in small qty? :-( > > -marc > > On Fri, 4 Feb 2005, [ISO-8859-1] Hernán Freschi wrote: > > > check this out: http://home.wanadoo.nl/erwin.gijzen/wifiswr/ > > Also, look for another DIY SWR meter. I can't find it now, but all it > > takes is a microwave diode and you get DC, which you amplify later and > > get a nice DC reading. > > > > hjf > > > > > > On Fri, 04 Feb 2005 11:36:31 -0500, Marc Nicholas <marcEraseME.....geekythings.com> wrote: > >> That's what prompted the question -- there must be a relatively simple > >> tunnel diode circuit that can be used. But there's no technical details or > >> schematics on that site. > >> > >> I also thought about using one of MAXIM's tiny (TSOC or SOT23) ISM band > >> downconverters, and then smoothing out their still AC output with > >> rectifier/caps. > >> > >> -marc > >> > >> > >> On 2/4/05 10:59 AM, "Alex Harford" <EraseMEharfordgmail.com> wrote: > >> > >>> On Fri, 04 Feb 2005 10:47:56 -0500, Marc Nicholas <RemoveMEmarcEraseMEEraseMEgeekythings.com> > >>> wrote: > >>>> Can anyone give me some guidance on a *simple* circuit for detecting 2.4Ghz > >>>> microwave (Wifi etc.) and providing DC output? It wouldn't have to be > >>>> terribly sensitive and I'd prefer it to be pretty passive :-) > >>> > >>> There was just such a project on Slashdot yesterday: > >>> > >>> http://neil.moon-beam.com/users/kris/index.htm > >>> > >>> Alex > >> > >> --

At 16.26 2005.02.04 +0000, you wrote: >On Fri, 04 Feb 2005 10:47:56 -0500, you wrote: > >>Can anyone give me some guidance on a *simple* circuit for detecting 2.4Ghz >>microwave (Wifi etc.) and providing DC output? It wouldn't have to be >>terribly sensitive and I'd prefer it to be pretty passive :-) > >A suitably fast diode detector should do the trick only if the level is higher than the dropout voltage, right?

On Fri, 4 Feb 2005, Marc Nicholas wrote: > On Fri, 4 Feb 2005, Peter L. Peres wrote: > >> If you want to measure I would look at Analog's log-amps which can be had >> for as little as $7 in ones and accept rf input directly at your >> frequency, providing db-proportional output. > > These a MSOPs, so tiny...which will be good coupled with the PIC10F and a > bunch of SMD LEDs for level. :-) They exist in SOIC too I think. I just looked a few days ago. These products are clearly oriented towards cell phone use, thus the size and the reasonable budgetary price. Peter

On Sat, 5 Feb 2005, ThePicMan wrote: > At 16.26 2005.02.04 +0000, you wrote: >> On Fri, 04 Feb 2005 10:47:56 -0500, you wrote: >> >>> Can anyone give me some guidance on a *simple* circuit for detecting 2.4Ghz >>> microwave (Wifi etc.) and providing DC output? It wouldn't have to be >>> terribly sensitive and I'd prefer it to be pretty passive :-) >> >> A suitably fast diode detector should do the trick > > only if the level is higher than the dropout voltage, right? No, you polarise the detector with dc from a battery so the dropout voltage becomes very small. That would be class B operation. Peter

At 20.48 2005.02.05 +0200, you wrote: >On Sat, 5 Feb 2005, ThePicMan wrote: > >>At 16.26 2005.02.04 +0000, you wrote: >>>On Fri, 04 Feb 2005 10:47:56 -0500, you wrote: >>> >>>>Can anyone give me some guidance on a *simple* circuit for detecting 2.4Ghz >>>>microwave (Wifi etc.) and providing DC output? It wouldn't have to be >>>>terribly sensitive and I'd prefer it to be pretty passive :-) >>> >>>A suitably fast diode detector should do the trick >> >>only if the level is higher than the dropout voltage, right? > >No, you polarise the detector with dc from a battery so the dropout voltage becomes very small. That would be class B operation. adding a resistor connected to Vcc? by the way, this reduces the signal strength a bit, because it lowers the impedance.. right? >Peter >-

On Sun, 6 Feb 2005, ThePicMan wrote: > adding a resistor connected to Vcc? > > by the way, this reduces the signal strength a bit, because it lowers > the impedance.. right? Yes, actually a voltage divider, or, the best solution, a temperature compensated bias source (i.e. a diode and two resistors). The impedance needs to be matched to the dipole. This is low impedance (75 to 150 ohms). The 2SC2570 was specially developed for untuned trunk and cable distribution amps and has about the right input and output (!) impedances for use with coax cables. Expected gain is 7 to 22dB per stage but when rectifying single ended substract 6dB. Peter