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Part Number: CC2520
The refdesign CC2520EMK is a two layer design with 0.8mm between TOP and GND plane.
Our PCB there the CC2520 is used is a six layer with 0.15mm between these two planes.
Can you please investigate if there are a ref-design with 0.15 or 0.17 instead of 0.8mm?
We have big problems to get the power out to the antenna. The EMV value of the Zigbee is bad. Difficulties finding the right values in the Discrete balun when the distance is 0.15 instead 0.8mm.
It is even harder when we can not find Differential impedance at the output 17 and 19 of the CC2520. We have found it in a datasheet from Johanson! and not in CC2520 see attached picture below. In your CC2500 it is easily found also see below.
So two questions to you:
If you are using the t-line inductors as used in original design with two layers then this will have problems if the GND plane reference is changed from 0.8 mm to 0.15 mm.
Can you use discrete components instead of the t-line integrated inductors ?
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In reply to RGW:
CC2520 is not a linear amplifier where optimum gain is achieved when the load is the complex conjugate of the amplifier output impedance. The optimum load impedance is found utilizing load pull techniques and then verified by tuning and measurements.
The load should be close to 70+j95 in the band 2405-2480MHz band.
Thanks for the fast answer!
The product are already on the field. So we hoped to fix this impedance problem by changing values on the capacitors within the Balun. It seems difficult.
We have to high EMV getting not acceptable when we transmit over 0 dbm it is over 4%.
Approx load impedance:
CC2500: 80 + j74
CC2520: 70 + j95 (Impedance has changed slightly from CC2500)
Will take this new value into to our calculation program, simulating the Balun, and after that the 3-port VNA.
We have tried with 35-j43
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