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  • Users: Leiser
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  1. Leiser

    IMD asymmetry

    Hello, I am measuring IMR3 of a DAB band III LNA from production. Some boards show IMR3 asymmetry and others not. Does anyone know what could be the cause? The LNA is implemented by a MIMIC MGA-62563. Also the IMR3 has drop for the case of asymmetry. I attach the two plots.
  2. Leiser

    GPS LNA+antenna stability measure

    Hello, I have a question. I have to measure the stability of a GPS LNA + antenna set from a supplier. I have measured stability without the antenna, only for the LNA, from DC to 8GHz. It turns that it is not stable from DC to 800MHz. Do you know in what frequency range GPS stability is usually...
  3. Leiser

    common-base LNA

    Hi, I am investigating the schematic of a FM common-base amplifier. It has two diodes that I do not know what are they used for. D4 are two BAV99 diodes in a SOT323 package. I think they are used as an ESD protection. Does anyone know why are connected in such a way? Pin 4 of the transformer...
  4. Leiser

    Altium PCB EM simulation in Feko

    Hello, I am trying to import in Feko a 4-layer PCB made in Altium to do an EM simulation of some filters. I have been talked that the way to do it is to export the part of the layout from Altium to .step and aftwerwards to .igs. The problem we have found is that both top and bottom layers were...
  5. Leiser

    Friis equation in ADS

    Hi, I am trying to measure with ADS the noise figure of a 3dB attenuator. I was expecting to see 3dB noise figure but ADS says 0dB. I have also measured the NF of a filter with 3dB of insertion loss but the result is also 0. This components are from ADS library. I am using a S-parameter...
  6. Leiser

    RF transistor for first 2.3GHz amplifier stage

    Hi, I would like to know what technology do you recommend for a first stage 2.3GHz LNA amplifier. I am looking for a transitor with 0.3dB max. NF at 2.3GHz. It is also high linearity, ~27dBm OIP3, 16dBm output power at P1dB, Gain aorund 16dB. I have checked transistors from Avago, like...
  7. Leiser

    Microwave microstrip simulation

    Hi, I'm trying to simulate a 0.114pF shunt capacitor using a short circuit stub at 1.5GHz microstrip. Doing the calculation it turns that a 51.7mm 50R transmission line is needed. I have compared the S11 parameters of the lumped capacitor to the transmission line and are the same. Then I have...
  8. Leiser

    how to know what type of PCB/substrate is

    hi, I have an LNA for a 2.2GHz application. I would like to know what type of PCB/substrate uses. Is there any way to know, measure for example dielectric contant..... Thanks.
  9. Leiser

    ADS question

    Hi, does anyone know how in S-parameter simulation set the power level of the input? I want to get the S21 for an amplifier for diferent input power levels. Thanks,
  10. Leiser

    ADS

    Hi, I am simulating an AGC circuit with ADS. I have modelled the pin diode as a resistor whose value depends on a variable. The value of the resistor depends on the output voltage of a op-amp, set as a comparator. I am having some problems when relating that variable to the op-amp output...
  11. Leiser

    ADS question

    Hi, I am simulating an LNA for NF. I loaded the antenna S parameters to the input port. But when running the simulation there was a problem "No DC convergence" I am using a spice model for the main transistor. Simulating the LNA with 50R is ok, but the problem comes when loading the antenna S11...
  12. Leiser

    RF filtering question

    Hi, I have to filter RF signals from DC lines. I was thinking using capacitors connected to those lines and ground, shunt capacitors. I have to filter signals from AM, 150KHz to 2GHz. I was thinking just using small capacitors which SRF is around 2GHz. But looking at some circuits I have seen...
  13. Leiser

    SMD test fixture

    Hi! does anyone know a affordable smd test fixture to measure SMD components with a network analyzer? I am looking for a test fixture where I can place SMD components up to 0402 with N-type or SMA connectors. Something similar to this, but simpler http://www.coilcraft.com/smda.cfm Thanks!
  14. Leiser

    AGC circuit

    Hi all, I am designing an AGC circuit for an FM receiver amplifier. I am struggling with the detector, because the AGC is not constant with frequency. I get more attenuation for the higher part of the band than the lower. I was wondering if you could recommend me any book about AGCs and in...
  15. Leiser

    FM amplififier-PCB cost reduction

    Hello, I designed a FM "LNA" using a two-layer PCB and worked fined. I was thinking to reduce the cost of the PCB by using a one-layer PCB and removing the ground plane on the bottom layer. I would route the ground connections on the top layer. I have found with PCB manufacturer that cost...
  16. Leiser

    Antenna matching

    Hi, I have to match a DAB antenna to my LNA. The antenna S11 is very bad as it´s very narrow band. Attached you will find the S11. I was wondering if anybody has experience matching antennas and can help me with that, as I´m trying to design a filter that has minimum transmission losses...
  17. Leiser

    RF layout impact simulation

    Hi, As everybody knows, the simulation doesn´t really math to the real thing in the lab. I am starting to design LNAs up to 2GHz with ADS. When I do the layout in PROTEL I do it adding all my knowledge about the impact it has in RF performance, but lately I have been thinking if there is any...
  18. Leiser

    VSWR question

    Hi all, I have a question about VSWR. Sometimes VSWR is specified as a ratio, for example. 2.0:1 what does exactly mean this ratio? and would that mean if it was 1:2.0 Thanks!
  19. Leiser

    Amplifier TV specs for reception

    Hi all, I have some customer specifications for a receiver TV amplifier. Noise figure is stated as a max. of 4dB. Does anyone know why is it higher than for the FM band which is 1.5dB? And a second question. Can anyone guide on the possibility of doing a TV receiver amplifier using an...
  20. Leiser

    common-base BJT LNA

    Hi all, happy new year! I have my first question this year. I am trying to understand how a common-base BJT LNA works. The circuit I am analysing uses a transformer feedback. Does anyone know any literature, web site, articles about this type of amplifiers? Does anyone know what are the...

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