Antenna Low Power RF & Wireless Connectivity

Posted on Feb 4, 2014

The `green area` is where should be placed the TRF7970A `s antenna (Between 0 ohm resistors, the antenna should be connected). TRF7970A `s antenna can be done step by step according to the document `Antenna Matching for the TRF7960 RFID Reader (SLOA135) `. And here comes the part I do not understand: What role has the `red area` of the figure Why

Antenna Low Power RF & Wireless Connectivity
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is placed that part of the circuitry in the schematic TRF7970A Why do not I see this part of the circuit in TRF7970EVM`s hardware Then, If Ibuild the TRf7970`s antenna as is shown in SLOA135 (3 capacitors, 1 resistor and antenna), I should do not include the "red area" in my hardware ciruit Why the intermediate 50 ohm To tune independently and in a easier way the antena without complicating the circuit. Also RF instrumentation is calibrated to 50 ohm. How you can do it Just unsolder R3_0(0 ohm shunt) to unconnect the blue part. Red area now can be connected to external instrumentation through the SMA connector(green area). Playing with C12, C13, C14, R1 and an impedance calculator you can tune it. I included also the red area in my hardware design. Until a while ago I did not know what the "red area" do Now, you explain me this: "Blue area that matches 50 ohm to 4 ohm". If you have implemented the PCB with 3 capacitors (56, 47 and 10 pF) and a 1kohm you have implemented the red area. That is the red area. You do not need to include another red area if you can understand me. The L3 inductor represents only the antenna coil that is present in your PCB. The terminals of the PCB antenna coil should be connected to the terminals of the L3 inductor The last is a simpler approach that can enable the designer to match any coil antennas with simpler calculus. With this approach if you unconnect the blue area and have the...

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