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  1. J

    Crosspol is not at boresight

    I have an S band antenna for satellite communications and when I check the copol pattern from a LHCP satellite (XTAR-EUR in my case) everything is cool. When I switch it to RHCP with a coaxial switch to check for crosspol I get double crosspol nulls at sides of the signal and couldn't...
  2. J

    Eb/No to BER formula for QPSK

    Hi, I am trying to find the formula for the BER vs Eb/No curves but I only see the curves themselves as 10^-6 BER is about 10.5 Eb/No what is the formula to get these results?
  3. J

    [SOLVED] Polarizer axial ratio

    Hi. I'm trying to design a Ka band Tapered corrugated polarizer. I somewhat was able to keep phase difference stable but the S parameters differ alot. What i was trying to ask when I search the papers they only use the phase difference between the ports for axial ratio calculation but not the...
  4. J

    Spectrum Analyzer weird results from LNA

    Hi.I have designed an LNA for S-band between 2.2-2.4 GHz bands. The thing is when i test it i see this weird stuff on Spectrum analyzer like some 50 MHz signal is getting mixed in.I couldnt really work out a reason. can you give me a clue why it might be doing this ? You can see my marker is at...
  5. J

    Semi-rigid vs flexible cable for antenna feed

    I designed an antenna feed that is capable of monopulse tracking.What I wanted to ask was which cable is better to use for both monopulse and antenna feed cable.I would like to use flexible cable t-flex 405 for ease of use but I also think the phase stability is critical for tracking accuracy...
  6. J

    Horn Antenna to coax pin feed

    Hi. I've designed a waveguide to coax adaptor for an S band feed horn. The thing is when I was designing the conductor that goes into the waveguide I didn't check available product length and took Pasternack's PE4099(Candlestick SMA connector) as base for conductor and ptfe dimensions . Now I...
  7. J

    S11 smith chart contour too big

    Hi. I designed an S band LNA and fabricated it but there is a little problem. S11 and S22 of the circuit is nowhere near the simulation Here is the both measurement and simulation results. What could be the problem here ?
  8. J

    [SOLVED] LDO tps7a4701 not working as intended.

    Hi. For my LNA design I was using tps7a4701 as a regulator to supply DC voltage to circuit. I designed the pcb according to datasheet and used any-out option and it should give 4V all times. Now i get a variable output at the output of LDO. when i give Vin=3V, ı get Vout=3V and this goes all the...
  9. J

    Voltage drop at second stage LNA

    Hell everyone. I've been designing a 3-stage LNA for 2.4 GHz and today I tested the LNA but for some reason when I connect the LNA to voltage source it voltage supply drops from 4V(correct value) to 2.7V. Then i used seperate voltage sources for 3 seperate stages and it seems the second stage...
  10. J

    Using Invar material in Septum Polarizer and Feed

    Hi. For a project i had to design a septum polarizer. But they wanted it to work from +55C to -30C. If i hit these limits my crosspol drops below 30 dB if i use Aluminium.So I found this Invar which is %64 iron and %36 Nickel and has a very low thermal expension coefficient.Here is the Link...
  11. J

    TE21 monopulse coupler

    How does it work? I found a paper(https://ieeexplore.ieee.org/document/7068002/) and a company that explains it vaguely(https://docs.wixstatic.com/ugd/bdfa9d_4c310c25fbaa4b29a3e545ce45656ab3.pdf) but is there any book or formula you can point how we get the signals and how do we seperate the...
  12. J

    Contacting Rotary Joint Design

    Hi. I need to design a contacting rotary joint from DC to 18 GHz but i don't know how. I tought of a slip ring but when I think about it, a ring would act like a rat race coupler depending on the frequency.So i might get nothing from the recieve port. It will have sma connection and 2 channels...
  13. J

    [SOLVED] Relation between Frequency and bit rate.

    I know the relation between bps and Hz as a formula but i can't imagine how the data is sent. Say I have a basic psk modulation and i want to send data from a satellite down to earth for tv. They allot me 50 MHz bandwidth. How do I send my data over this 50 MHz bandwidth between 12000 MHz and...
  14. J

    Biasing with parallel (series LC) at input

    Hi.İ've been working on LNA design but I needed to connect one series, one parallel capacitance at the input of transistor. Is it ok for me to use series LC instead of only C for parallel Capacitance If I use an inductor to stop RF leaking to ground over capacitance ?
  15. J

    Ce3512k2 CEL RF Transistor non linear model.

    I found this transistor for X band LNA but i couldn't get non-linear model of the transistor. Contacted to CEL costumer service but still not a reply after 2 months. Is there anyone who used this transistor and have the non-linear parameters ?
  16. J

    NF of a LNA in AWR EM simulation

    Hi. I am designing an LNA on AWR. When I run the simulation without EM_Extract I get 0.47 dB NF. When I run it with EM on and X,Y cell size= 1 mm I get around 0.53 dB NF. When I decrease the X,Y cell size to 0.1mm it gives 0.61 dB NF. My question is which one I should consider as more...
  17. J

    [SOLVED] Importance of Unconditional Stability in LNA design.

    I'm trying to design a LNA in S band for 2.4 GHz Wlan applications , Input VSWR<1.5(probably antenna will be matched to 75 ohms) , NF<0.5 , S21=50dB. I will cascade 3 or 4 transistors for S21. I was able to get 0.45 NF for the first transistor on AWR but the transistor is unstable after 4...
  18. J

    [SOLVED] 2.3 GHz lna design parameter vs netlist

    2.3 GHz lna design sparameter vs netlist Hi. I am trying to design an LNA at 2.3 ghz with infineon's BFP 740 ultra low noise transistors. On their page there is an axamle at the same frequency. When i use sparamets i get 0.18 db NF but when i use netlist with the same matching circuit I get...

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