RF components placement on a PCB in Layout. - Page 1
Forum section: electronics / rf-microwave

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: February 07, 2018, 01:55:38 pm
content: Hi everyone, can anyone say,What should be the clearance/isolation between a GPS chip antenna and 1621 MHz patch antenna in PCB layout, to reduce the interference of received signals?Thanks in advance.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: February 08, 2018, 12:30:45 pm
content: Simulation, simulation, and simulation. That is how you find out. This depends on a lot of things, and someone with a lot of experience might be able to look at something and go "that'll probably be fine", but the only way to be confident in it is to simulate.

author: cowana
author_rank: Frequent Contributor
timestamp: February 08, 2018, 01:01:14 pm
content: Is the 1621MHz patch transmitting, or just receiving?If it's transmiting, you'll need significant separation to avoid overloading the first LNA of the GPS receiver. If it's receiving, the biggest issue will either be detuning of the GPS chip antenna, or unintentional transmission (via LO leakage) from the 1621MHz patch.

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: February 10, 2018, 08:17:46 am
content: The patch antenna is both transmitting and receiving.Can you tell me the range of separation between both antennas, is it in mm or cm or m range?

author: hagster
author_rank: Frequent Contributor
timestamp: February 10, 2018, 08:29:36 am
content: There are no simple answers to this.The RF coupling between the two antennas will be both radiated(near field) and conducted. Hence hard to calculate.The duty cycle of your tx will have a be effect. So long as its not damaging the GPS should recover when the tx is off.The out of band emmisions will have an effect.The input filtering of the GPS engine will have an effect. Note you can possibly add a SAW filter to help with this.Through bitter experience, i know that GPS engines are sensitive to on board interference from other high frequency signals on board such as clock harmonics etc. Take great care with layout and earth loops and decoupling. Etc etc.

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: February 15, 2018, 10:11:44 am
content: Can anyone tell meThe circuitry involved in interfacing a single dual-band antenna to two different modules in a single circuitThanks in advance

author: ogden
author_rank: Super Contributor
timestamp: February 15, 2018, 10:22:42 am
content: Quote from: madhu.wesly01 on February 15, 2018, 10:11:44 amIt's diplexer.

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: February 17, 2018, 02:40:14 pm
content: @odgenI request you to elaborate more on the circuitry.Will the circuit have diplexer and its supporting circuitry ?Can you please provide me any resources or reference design for understanding the hardware involved

author: ogden
author_rank: Super Contributor
timestamp: February 17, 2018, 06:27:41 pm
content: Quote from: madhu.wesly01 on February 17, 2018, 02:40:14 pmYou arerequestingme to elaborate you circuitry? On what grounds? I am not your slave LOLp.s. I gave you direction:diplexer. Supposing that you study subject and use your head to think how it can possibly solve your problem. If you have further questions regardingdiplexer specifics- I will not hesitate to share my knowledge as far as I know.

author: cowana
author_rank: Frequent Contributor
timestamp: February 18, 2018, 10:43:32 am
content: Quote from: madhu.wesly01 on February 17, 2018, 02:40:14 pmThat really isn't how this forum works. As Ogden said, the bulk of the design needs to come from you, after which this is an excellent place to seek review and suggestions.You're not going to find one 'off the shelf' solution that perfectly matches your requirements. The optimal implementation for your application will depend on a lot of factors, including the following for each band:Maximum transmit/receive powerSignal bandwidthMaximum allowable attenuationOut of band rejection requiredPhysical available size/weight for diplexerDevice operating temperature constraints...etc

author: Howardlong
author_rank: Super Contributor
timestamp: February 18, 2018, 11:51:01 am
content: http://www.instantdegrees.com/

author: Kilo Tango
author_rank: Regular Contributor
timestamp: February 18, 2018, 12:47:52 pm
content: Possibly an "unfortunate phrasing " due to non english speaker.https://www.microwaves101.com/encyclopedias/diplexersKen

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: March 06, 2018, 06:43:52 am
content: Hi,I am not sure on the following two issues, could any one tell if I can perform these in my layout design:a. Can I draw RF traces near tin plated steel mounting holes?b. Can anyone tell me the issues faced if RF traces of different frequency travel on the same layer with a clearance of approximately 4 mm?If Yes, Any precautions to be followed while performing the above??Regards,

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 06, 2018, 11:07:54 am
content: http://www.cypress.com/file/136236/downloadQuote from: TheUnnamedNewbie on February 08, 2018, 12:30:45 pmany suggestion on software simulation?

author: ogden
author_rank: Super Contributor
timestamp: March 07, 2018, 11:44:35 am
content: Quote from: Kilo Tango on February 18, 2018, 12:47:52 pmRight. That article refer to diplexers so where's catch of your comment?Regarding non-englisch speaker you were indeed right.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: March 07, 2018, 04:31:51 pm
content: Quote from: Mechatrommer on March 06, 2018, 11:07:54 amFor my work I use "professional" tools, by which I mean tools that are unfortunately outside of the budget of the average hobbyist.For full 3D simulation we use HFSS - transitions from high metal layers to the gate/drain/source connections of the transistors on chip. Full verification of system before tapeout but these are simulations that take days or weeks. Non-planar structures such as wave guide launchers, SIW, etc.General RF design is in Keysight ADS/Momentum. This is also the tool where we put everything together (either this or in Cadence Virtuoso). Things we use this for would be on-chip inductors and transformers during the design (once we have a design that seems to work, we use HFSS to do a full 3D simulation to make sure, but this takes a lot longer). I've also used it for distributed filters and matching networks. This is the core tool I use for doing PCB transmission lines - We would put a rough idea of the transmission line in Altium or Allegro, and then export the design and put the actual line in with ADS so we can verify and simulate performance.I have little experience with "free" tools, though I hear a lot of people talk about QUCS. I've never used it myself, so I don't know if it is actually any good. The pictures I've seen look like it is going after a free version of ADS.

author: Howardlong
author_rank: Super Contributor
timestamp: March 08, 2018, 11:28:27 am
content: To be clear, the problem with the OP's questions are that they are looking for a black and white answer to a scenario with so many unknowns.It's like trying to assemble a 1000 piece jigsaw puzzle, but you only have two pieces.