I need some urgent help with a RFID scanner I am designing for my work. It is needed ASAP and I have run into a last minute problem. My read range is terrible...like rub the chip on the pcb antenna and you might get lucky. From prototype to the final version, a display was added and the added pcb size and traces seem to be contributing to the issue. The entire scanner comprises of a main pcb which I designed. It houses the main uC, LEDs, beeper, comm stuff, etc. There is a daughter board on the "back" which is the Sonmicro SM130 RFID module. On the front is another daughter board which is a PCB antenna with on board matching circuit also from the Sonmicro. The antenna daughter board has only about 0.2 in of separation from the main board. Making this separation larger helps some but not much and cannot be larger due to case design. The antenna appears to be VERY similar to the design shown on pg 14 of **broken link removed**
I have some ferrite sheet which I tried placing between the main pcb and the antenna pcb but it seems to make it worse where as the above pdf makes it sound like it will help with close metal objects.
The interesting thing is if I put another unpowered pcb antenna on top of the powered one separated by 3mm of acrylic (the case) my read range is great. This is shown by the grayed out antenna pcb. My guess is that it is coupling with the main antenna and sort of retuning/filtering it.
I do not have access to a network analyzer or even a good oscope which isn't helpful.
The bottom picture shows the guts without the case with the temporary second antenna tapes to it.
Other than physical separation, is there anything I can do to drastically improve read range?
I have some ferrite sheet which I tried placing between the main pcb and the antenna pcb but it seems to make it worse where as the above pdf makes it sound like it will help with close metal objects.
The interesting thing is if I put another unpowered pcb antenna on top of the powered one separated by 3mm of acrylic (the case) my read range is great. This is shown by the grayed out antenna pcb. My guess is that it is coupling with the main antenna and sort of retuning/filtering it.
I do not have access to a network analyzer or even a good oscope which isn't helpful.
The bottom picture shows the guts without the case with the temporary second antenna tapes to it.
Other than physical separation, is there anything I can do to drastically improve read range?
