Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
- Nanovna-Users
- Messages
Search
|
Re: NanoVNA for RFID design
Larry Martin
Hello tjackson382000.
10 inches is a stretch for ISO15693, but out of the question for ISO14443. I like the Feig CPR74, which puts out 250 mW. It's a module with onboard antenna and a u.fl for off-board. Feig also has higher power (and higher priced) external antenna HF readers that will make your 10 inch distance a lot more doable. Their 100x100 mm antenna works great. I have built 24 inch across conveyor systems with Feig's older readers that put out only 100 mW, so your requirement is not a pipe dream. Your should try to physically match the sizes of the reader and tag antennas, so your 3 inch tag would talk best with a reader antenna of 2 to 4 inches or so. With a bigger antenna, your tag might only read at the corners. I am not aware of NanoVNA computing a Q value for you. If it did, you would still have to question whether their method matched that of the appnote. I would concentrate on computing Q per the appnote's methodology, given the profile of the Channel 0 LOGMAG curve, which is yellow by default. One fun trick I "invented" is to connect a nonresonant loop to port 0, about the same size as my tag. LOGMAG 0 should be flat across the stimulus range. Now put your tag on there. You will see the tag's resonant frequency and get a relative indication of its Q, which lets you compare tags to see which are stronger. |
|
Re: NanoVNA for RFID design
In the early days right "off The Hill" we had both 915 MHz and 2.45 GHz
passive (beam powered) and active (coin battery) tags. The present-day SAW RFID tags are beam "powered". That was developed after AMTEK had our swing at the market. Yes, large coils would get you the range you desire for the LF tage. Dave - W?LEV Dave - W?LEV On Thu, Jun 16, 2022 at 12:49 PM Reinier Gerritsen < r.gerritsen@...> wrote: It is no problem to read 10" with 125 KHz or 13.56 MHz, but you'll need-- *Dave - W?LEV* *Just Let Darwin Work* -- Dave - W?LEV |
|
Re: NanoVNA for RFID design
It is no problem to read 10" with 125 KHz or 13.56 MHz, but you'll need large antennas. I'm not aware of any (passive) 2.45 GHz RFID system on the market now. Had a Motorola system long time ago.
toggle quoted message
Show quoted text
Reinier Op 16-6-2022 om 01:53 schreef W0LEV: If you need 10"+ reliably, use the 950 MHz or 2.45 GHz system at lower --
IDcircuits - RFID & Electronics Het Halster 40 6581 JL Malden The Netherlands +31 633702492 www.idcircuits.com r.gerritsen@... |
|
Re: NanoVNA for RFID design
On 6/15/22 4:47 PM, W0LEV wrote:
Yep! That's in an MF ISM band. If one has a Metcal soldering implement, There are a variety of apps for phones that will interrogate the card and read it back. You can watch the activity on the TinySA. |
|
Re: |S11| > 1
Bob Witte wrote the referenced book due to the requirement of EMC testing.
toggle quoted message
Show quoted text
Any accredited lab must present measurement uncertainty of the lab in any RE test report. Without that, the report is not accepted. Dave - W?LEV On Wed, Jun 15, 2022 at 11:55 PM Frank K4FMH <frankmhowell@...> wrote:
Chuck,-- *Dave - W?LEV* *Just Let Darwin Work* --
Dave - W?LEV |
|
Re: |S11| > 1
Frank:
toggle quoted message
Show quoted text
Thanks for the tip about Bob Witte’s books. Chuck KF8TI On Jun 15, 2022, at 7:55 PM, Frank K4FMH <frankmhowell@...> wrote: |
|
Re: |S11| > 1
Chuck,
Take a read of Bob Witte’s measurement equipment books, written when he was at HP. Joe Carr’s tests and measurements book is another one rendering a cogent treatment of measurement errors without going very deep into the statistical deep-end. This work is based upon formal true-score theory: the central issue of which is whether the observed score’s errors are correlated with the true score and/or the observed score. 73, Frank K4FMH |
|
Re: NanoVNA for RFID design
If you need 10"+ reliably, use the 950 MHz or 2.45 GHz system at lower
toggle quoted message
Show quoted text
power, not these inductively coupled systems. Dave - W?LEV On Wed, Jun 15, 2022 at 5:04 PM Tim Dawson <tadawson@...> wrote:
Things like automated package/baggage sorting use RFID at times, and-- *Dave - W?LEV* *Just Let Darwin Work* --
Dave - W?LEV |
|
Re: NanoVNA for RFID design
The whole goal of the LF inductively coupled RFID systems is very short
toggle quoted message
Show quoted text
range. 10" is a stretch for these systems in normal applications. If you want more range, make the coils physically larger while keeping to the specifications for the silicon properly addressed. Dave = W?LEV Dave - W?LEV On Wed, Jun 15, 2022 at 4:39 PM Chuck, KF0CT <chu_r@...> wrote:
But why would anyone want an RFID reader that can read cards over 10" away-- *Dave - W?LEV* *Just Let Darwin Work* --
Dave - W?LEV |
|
Re: NanoVNA for RFID design
Yep! That's in an MF ISM band. If one has a Metcal soldering implement,
toggle quoted message
Show quoted text
it also operated in this band. Those having a TinySA, this offers an easy "target" for checking MF operation. Dave - W?LEV On Wed, Jun 15, 2022 at 1:26 PM W1RS <Deflatermaus@...> wrote:
Nice story on the history! I agree that the coupling for the RFID is-- *Dave - W?LEV* *Just Let Darwin Work* --
Dave - W?LEV |
|
Re: NanoVNA for RFID design
Thank you
________________________________ From: [email protected] <[email protected]> on behalf of Jim Lux <jim@...> Sent: Wednesday, June 15, 2022 6:45 PM To: [email protected] <[email protected]> Subject: Re: [nanovna-users] NanoVNA for RFID design On 6/15/22 9:39 AM, Chuck, KF0CT wrote: But why would anyone want an RFID reader that can read cards over 10" away except to read someone's Credit card or Debit card without the person knowing about it... then you just watch them type in their pin number and you have complete access to their credit/debit card.... A good use case is where you use the badge to authenticate into a computer (using an actual contact badge reader that uses the cryptographic chip in the badge), but then just need to make sure that the user is in the vicinity. If you require the badge to be resident in the computer, it makes it hard to use multiple computers at the same time. A typical PIV-II credential has both an RFID (which returns only the serial number of the badge) and an actual chip (like in a credit card). ISO14443A/B ISO ISO15693 are two of the specs ISO/IEC 15693 systems operate at the 13.56 MHzfrequency <>, and offer maximum read distance of 1–1.5 meters They do both ASK and FSK. As far as NanoVNAs go, it's a useful tool to develop and test these kind of systems - 13.56 MHz is easily choked with ferrites to remove the cables and instrument from interacting with the system. So you can set up a test card (which has the antenna, but a SMA or MMCX connector on it) and a test reader (just the antenna, with connector). And this is at a frequency for which the NanoVNA is perfect. You can easily set up a scripted environment, have a user wearing the badge on a neck lanyard and move around while logging S21. |
|
Re: NanoVNA for RFID design
On 6/15/22 10:04 AM, Tim Dawson wrote:
Things like automated package/baggage sorting use RFID at times, and distances to objects on a moving belt canrequire this kind of reach. Exactly - there are document management systems that put RFID stickers on each page or folder of the paper document (think mortgages and similar docs).? Then they have a reader that goes in front of a box of several hundred/thousand docs and inventories the box.? Imagine in your mind a 20 foot high shelving unit with a robotic device that places and retrieves boxes. |
|
Re: NanoVNA for RFID design
On 6/15/22 9:39 AM, Chuck, KF0CT wrote:
But why would anyone want an RFID reader that can read cards over 10" away except to read someone's Credit card or Debit card without the person knowing about it... then you just watch them type in their pin number and you have complete access to their credit/debit card.... A good use case is where you use the badge to authenticate into a computer (using an actual contact badge reader that uses the cryptographic chip in the badge), but then just need to make sure that the user is in the vicinity.? If you require the badge to be resident in the computer, it makes it hard to use multiple computers at the same time. A typical PIV-II credential has both an RFID (which returns only the serial number of the badge) and an actual chip (like in a credit card). ISO14443A/B ISO ISO15693 are two of the specs ISO/IEC 15693 systems operate at the 13.56?MHzfrequency <>, and offer maximum read distance of 1–1.5 meters They do both ASK and FSK. As far as NanoVNAs go, it's a useful tool to develop and test these kind of systems - 13.56 MHz is easily choked with ferrites to remove the cables and instrument from interacting with the system.? So you can set up a test card (which has the antenna, but a SMA or MMCX connector on it) and a test reader (just the antenna, with connector).? And this is at a frequency for which the NanoVNA is perfect.? You can easily set up a scripted environment, have a user wearing the badge on a neck lanyard and move around while logging S21. |
|
Re: NanoVNA for RFID design
TY
________________________________ From: [email protected] <[email protected]> on behalf of Tim Dawson <tadawson@...> Sent: Wednesday, June 15, 2022 5:04 PM To: [email protected] <[email protected]> Subject: Re: [nanovna-users] NanoVNA for RFID design Things like automated package/baggage sorting use RFID at times, and distances to objects on a moving belt canrequire this kind of reach. - Tim On June 15, 2022 11:39:33 AM CDT, "Chuck, KF0CT" <chu_r@...> wrote: But why would anyone want an RFID reader that can read cards over 10" away except to read someone's Credit card or Debit card without the person knowing about it... then you just watch them type in their pin number and you have complete access to their credit/debit card....-- Sent from my Android device with K-9 Mail. Please excuse my brevity. |
|
Re: NanoVNA for RFID design
RFID expert here. I had a quick look at the AN. It is quite complex to grasp in 60 seconds. I did some 13.56 MHz antenna design before, but these were all for a 50 Ohm system impedance, so you can have a few meter of coax cable between reader and antenna.
toggle quoted message
Show quoted text
Your primary goal is to measure the inductance of the loop antenna and the add resonating capacitors. Adding a parallel resistor may be needed to lower the bandwidth, otherwise the tag's modulated backscatter signal will be attenuated. There is a trade-off. A high Q allows for a high antenna current which gives you a large activation range. However, the tag signal will be attenuated. If the reader is really sensitive, that may be fine. You can also tune the antenna to one of the two sidebands. This will give an increased range since transmitter power is still fine and the reception of either lower or upper sideband is also fine. Some reader chips try to decode both sidebands and select the strongest. As a rule of thumb, range is approximately equal to reader antenna size. A large tag antenna size and optimized antenna tuning may give you some extra range, but I doubt you'll be able to reach 10". I tested two different reader chips and they had quite different performance. I just forgot which parts, but I'm pretty sure the STM chip was one of them. I'm on holiday now, no access to my notes from many years ago. To chear you up, it was not that difficult as it looked. But you'll have to have a firm grip on VNA measurement techniques to know what you are measuring. A VNA alway gives an answer, but it could be very wrong... Luckily, at 13.56 MHz, a few cm of wire does not shift the phase too much and it allows for some tolerance. The margins at 915 MHz are much smaller. Another rule of thumb that may help in initial loop design is that every mm is approximately 1 nH of inductance. Calculate one turn and multiply by the number of turns squared. Good luck! Reinier Op 14-6-2022 om 22:20 schreef tjackson382000: I'm sure that at least a few here are familiar with the following section from the STMicro application note "AN4974: Antenna matching for ST25R3911B/ST25R391x devices", since it calls for the use of a VNA and the ST25R391x is an RFID reader chip, supporting several standards. What I'm confused about is line 4. And I'm not sure of the nanoVNA setting for line 5 (Q factor measurement). Can anyone brief me on what the author is saying there exactly? I'm by now familiar with the open/short/50ohm calibration procedure of course, but intermediate level in re-exploring the many curvy zen mysteries of... the dreaded Smith Chart and applying the procedures within AN4974. |
|
Re: NanoVNA for RFID design
Things like automated package/baggage sorting use RFID at times, and distances to objects on a moving belt canrequire this kind of reach.
toggle quoted message
Show quoted text
- Tim On June 15, 2022 11:39:33 AM CDT, "Chuck, KF0CT" <chu_r@...> wrote:
But why would anyone want an RFID reader that can read cards over 10" away except to read someone's Credit card or Debit card without the person knowing about it... then you just watch them type in their pin number and you have complete access to their credit/debit card.... --
Sent from my Android device with K-9 Mail. Please excuse my brevity. |
|
Re: NanoVNA for RFID design
But why would anyone want an RFID reader that can read cards over 10" away except to read someone's Credit card or Debit card without the person knowing about it... then you just watch them type in their pin number and you have complete access to their credit/debit card....
________________________________ From: [email protected] <[email protected]> on behalf of tjackson382000 <tedj1@...> Sent: Tuesday, June 14, 2022 8:20 PM To: [email protected] <[email protected]> Subject: [nanovna-users] NanoVNA for RFID design I'm sure that at least a few here are familiar with the following section from the STMicro application note "AN4974: Antenna matching for ST25R3911B/ST25R391x devices", since it calls for the use of a VNA and the ST25R391x is an RFID reader chip, supporting several standards. What I'm confused about is line 4. And I'm not sure of the nanoVNA setting for line 5 (Q factor measurement). Can anyone brief me on what the author is saying there exactly? I'm by now familiar with the open/short/50ohm calibration procedure of course, but intermediate level in re-exploring the many curvy zen mysteries of... the dreaded Smith Chart and applying the procedures within AN4974. Also, does anyone here have actual experience with the design of reader impedance matching and tag antenna design for those chips? In other words, has anyone ever survived AN4974 and lived to tell about it? Finally, I need to design an RFID system (I chose the ISO-15693 standard for its relatively long range, although I would LOVE to hear about any other standard for which cheap front end chip solutions exist). Requires a 3" diameter tag antenna and any diameter below 5.5" for the reader antenna and a read range of up to 10" and must merely read out its unique UID code when detected. Am I dreaming? Sound feasible? Many thanks to anyone who might be willing to offer a little experience and advice, and I'd discuss compensation if an expert is willing. 7.3 Verification of the Q factor in the frequency domain The Q factor can be measured using a vector network analyzer and an ISO10373-6 Class 1-3 calibration coil. The following steps should be carried out: 1. The network analyzer shall be calibrated for a frequency sweep from about 10 to 20 MHz 2. S11 measurement in log mag format shall be displayed. 3. The calibration coil is connected to the VNA. 4. “Short” calibration of the coil and conversion to “Z: Reflection” 5. Set marker 1 and enable the bandwidth/Q factor measurement 6. Place the PCD antenna on the measurement coil Note: If the reader is plugged and powered, ensure that register 0x27 is set to 0xFF to avoid an high power transfer to the VNA ports, which can damage the VNA. 7. Adjust the suitable trim value via the register map (register 0x21) in the GUI of the reader 8. Place a 3 ? resistor between the RFO pin to simulate the chip resistance during operation. 9. Press “max search” to align the marker on the resonance frequency peak of the PCD antenna Figure 33 shows the results of such a measurement. #applications #coils #design #matching #nanovna |
|
Re: NanoVNA for RFID design
True. Antenna is a misnomer, and the tag and reader coils act together as a 'loosely coupled transformer', I think is a proper term. And yes, the ISO 15693 standard includes a 13.56 MHz carrier. The tag is energized by the field produced by the modulated primary coil, and the tag responds by modulating (intermittently shorting) its own secondary coil (amplitude shift keying), which is detected via induction by the primary coil and its associated front-end electronics. Thanks for all the background. Fascinating technology. But... any answer to my actual questions, please? Lol.
|
|
Re: 2port measurement determining Zdut with S11 and S21
Hello all of you,
Op za 11 jun. 2022 om 22:11 schreef Victor Reijs < pe1atn.victor.reijs@...>: Thanks for all the feedback provided. If I gain more experience, I willHere is my web page on my experiences. I think S21 and Y21 methods look promising using my NanoVNA-H: All the best, Victor |
Frank K4FMH
tjackson382000
to navigate to use esc to dismiss