Help identifying components (RF) - Page 1
Forum section: electronics / projects

author: Alan
author_rank: Newbie
timestamp: December 28, 2012, 07:19:12 pm
content: Hi all,Attached is a small 2.4GHz RF module. Everything appears to be powered via the 3.3v LDO, the middle IC is a A7105 2.4GHz and off to the right I believe is some custom MCU as the RF chip has a 3 wire SPI interface.Now looking at the left of the PCB the RF output is where I am lost. Any idea (or similar part) what the 8 pin black component could be? It is labeled 1110 (Date code?) NJA2. Also the white component above it? Appears to have eight connections to ground and then two (in and out) for the RF trace.https://dl.dropbox.com/u/1210420/IMG_0175.jpgRegards

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 28, 2012, 08:18:52 pm
content: Quote from: Alan on December 28, 2012, 07:19:12 pmRF Amplifier?QuoteRF Filter?

author: jerry507
author_rank: Regular Contributor
timestamp: December 28, 2012, 09:05:01 pm
content: Agree with PA0PBZ. The output of the amplifier has a pi filter and an ac couple cap heading into that filter. It'll be some variety of SAW filter like this:http://www.digikey.com/product-detail/en/SF1189B-1/583-1086-1-ND/1918968Take a look here:http://ww1.microchip.com/downloads/en/DeviceDoc/75041B.pdfThat's fairly similar. There's some extra stuff I can't identify quite off hand. The RC circuit to the bottom left and the mess of passives in the upper right. The LC circuit to the upper left will be the filtered power input to the amp. Everything going into pin 2 is input conditioning.I'm not sure that your assessment of the micro is right though. Looking at the datasheet for the RF ic (http://www.avantcom.com.tw/AVANTCOM/TC/DATA/PRODUCT/SOLVE/18_3.pdf) the SPI pins go straight into that 8 pin IC. The unpopulated part on the top side of the 8 pin IC would connect a GPIO from the radio. Instead the other resistor ties it to the regulator input, 3.3V. That pin seems like a CS pin, but in this case doesn't do anything. There has to be more to it than that.What do the other header pins do?

author: gszo123
author_rank: Contributor
timestamp: December 28, 2012, 09:26:18 pm
content: The white component is probably a balun filter.Something like this:http://uk.farnell.com/johanson-technology/0783fb15a0100e/balun-filter-783mhz/dp/1885512

author: Alan
author_rank: Newbie
timestamp: December 28, 2012, 10:26:32 pm
content: Thanks for your replies guys. After doing a few more searches I think the RF power amplifier is actually a RFIC AP1110.Jerry, I am pretty sure it is some custom MCU. I have found pictures of very similar RF modules while looking for more information, others modules had the markings left on the chip. I remember seeing one post where someone had even used a logic analyser between the two devices. I'm not sure how you came to your conclusions, maybe you thought it was a bottom down view pinout in the datasheet or my image is loading in a different rotation in your browser?Regards

author: toby
author_rank: Newbie
timestamp: January 04, 2013, 10:30:41 pm
content: Quote from: gszo123 on December 28, 2012, 09:26:18 pmBut if this is a balun, shouldn't there be one microstrip line going to (the original signal) and two coming from (the signal and the 180° shifted signal) the device? My best guess is a bandpass/transmit filter.