Author Topic: LoRa SX1262 Matching Circuit  (Read 1851 times)

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Offline JeWe37Topic starter

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LoRa SX1262 Matching Circuit
« on: January 23, 2020, 07:50:48 pm »
So I have been working on a board which includes an SX1262 LoRa Transciever IC for communications. I am configuring it for 22dBm TXCO 868MHz operation(Europe, the 869.4-.65MHz band allows 500mW) but only need it to transmit. Due to space constraints I decided to go with 0201 components rather 0402 components, as Semtech recommends(https://lora-developers.semtech.com/knowledge-base/forum/viewthread/191/ https://semtech.my.salesforce.com/sfc/p/#E0000000JelG/a/2R000000HSSf/GT2IXjK2nH8bw6JdEXfFBd.HmFATeLOpL402mZwpSho) and decided to drop the RF switch which has no use if one is only transmitting. On the PCB I am aiming to keep the signal path straight, albeit while diverging from that occasionally for caps to ground. I have also taken care to match my RF transmission lines to 50 Ohms using the parameters provided by my PCB manufacturer. Additionally attempted to verify that the components were going to produce roughly the same characteristics by using QUCS to model the relevant parts of each(i.e. the impedance matching and filtering) giving me the picture shown below for the transmission gain in dB, which I hope is close enough.
This is my first more in depth RF Project and I would be thankful if anyone could confirm that what I did was sufficient or point me towards other theoretical tests I can conduct, as I want to avoid blowing an additional $80 on a second prototype board.
 

Offline Peter_SB

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Re: LoRa SX1262 Matching Circuit
« Reply #1 on: February 06, 2020, 03:01:12 pm »
From my experience you will have to measure and adjust the matching circuit once you get the PCBs. There are always slight deviations from what the reference design suggest. Ref design is good starting point but verification is always needed.
 
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Offline JeWe37Topic starter

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Re: LoRa SX1262 Matching Circuit
« Reply #2 on: February 06, 2020, 09:26:18 pm »
Right, I expected that, but I am hoping that given the frequency isn't excessive and that the tolerances should be fairly large those deviations will not be deal breakers. I will definitely test it, but rework could be difficult given the component size. I don't need to certify it nor is power overly critical, so as long as leakage does not get into the illegal range I should be good.
 


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