Increasing the Range of the MRD2EVM Microreader

Ashley - 

as the uRDR does not use the TMS3705 i am uncertain exactly how the SCBA031 would directly help you, but the concept does - amplifying will help downlink, but you must be helped here on exactly what is appropriate.

What sort of range are you looking for and where did you get 70mm HDX tag?

Depending on the range requirement you communicate back...then we can answer further which way to go here.  

Josh

Thanks for helping.

The tag is actually a TMS37157 with a 70mm diameter coil

I have tried several combinations of reader and antenna.  If I connect the microreader to an RFM007 high power reader, with a large G02E antenna, I can get ranges or around 0.8m (with good orientation), slightly more range with a G01E antenna (approaching 1.0m).

I would like to achieve 1.0m range.  So the RFM007 approach is possible, but it is expensive, power hungry and is now declared obsolete.  Also, I would like to use the "Get Last Low Bit Frequency" feature of the microreader, which is not possible when it is connected to the RFM007 (I am currently using an external circuit to measure tag preamble frequency).

We are currently testing a 600mm x 1000mm reader antenna with a microreader connected to a RFM007 - range is less than 1.0m and tuning is difficult

A microreader on its own (without an RFM007) and a 200m x 900mm reader antenna achieves a range of around 600mm and I can see the range is being limited by the downlink signal power.  So simply increasing the power from the microreader seems logical - if it is possible!  However, I not sure if the operating range will then be limited by the sensitivity of the microreader.

I have used the TMS3705 previously and can see it has a balanced output drive, but I suspect the microreader has a single ended drive, so I was going to investigate adding a UCC27425 (one inverting and one non-inverting) rather than a UCC27424 (dual non-inverting) described in the app note.

I would welcome your thoughts on this approach, or your advice on any alternative approaches.

Regards

Ashley

Ashley -

The RI-RFM-007B is still an active device. 

attached here is the example of using the -ADR2 basestation controller (MSP430) connected to the -007B and some read range examples which are made with RFM operating at ~1/2 its full power and with various sized antennas and some larger prototype tags, two of which are in the size area of what you have made. 

7450.PaLFI_Power_Reader_Rev3.pdf

you will see that almost 1m range was achieved, but its still a bit short and then also shorter still when using the MSP430 access command with and without the battery.

Josh

Many thanks and very interesting, I can see my ranges were similar to those in the document for similar tag and reader antenna sizes (the RI-ANT_GO1E and 85mm circular tag antenna).  I also noticed you stated that the RFM was only operating a half power.

We are using the TMS37157 as it is the only part easy to purchase as a raw device – we do not need any of the special external data access features of the devices

Regarding the RFM007; Mouser sent us an “End of Life Notification” on June 5^th 2014, for the RI-RFM-007B.  But even if it was not end-of-life, we would like to use a cheaper smaller alternative and the microreader does have some useful features (esp the "Get Last Low Bit Frequency") and USB interface.

What are your thoughts on trying to add an external power “boost” for the microreader downlink to increase range to around 1metre and any thoughts on whether we would then be limited by the sensitivity of the microreader (and then whether we could add an external LNA)?

Ashley

I don't like reviving old threads, but I am in a very similar situation and I'm looking for means of increasing the power output of the MRD2EVM without resorting to the expensive RFM007 module.

Can you share here the solution you adopted (assuming you found a solution) ?
Any new suggestions?

Thanks
George

Hi Josh,

We have a custom target board using the TMS37157 and the Neosid transponder coil. The target board is battery-less and we have a microcontroller attached. We are using the MSP access commands to read a sensor through the microcontroller.  We might be able to go with a larger antenna on the target board but would prefer to keep with this transponder coil due to space requirements.

Actually we are not interested in a long range, the target will be at around 25mm range. The problem we have is that the target board moves across the reader coil at a fast speed while we are sending out repeated MSP access commands. We are able to read the sensor correctly with the current setup even while the target board is moving at high speed but the transponder coil needs to be very accurately aligned with the coil edge (we have a rectangular coil) for the read to be successful. Unfortunately it is not easy to ensure perfect alignment at all times so we are looking at increasing the power output hoping that this will solve this alignment issue.

Can the  RI-RFM-003C perform MSP access commands ?

Thanks,

George