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  1. Leiser

    IMD asymmetry

    Thanks very much for you prompt answer. I tried but didn't work. It seems some ESD protection diodes from different batches are responsible for the IMR asymmetry. I changed them and it work.
  2. 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.
  3. 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...
  4. Leiser

    common-base LNA

    You are right. I have checked it and there is an inductor with a series resistor to ground at the RFin pin, as you said (just at the input of the transformer)That is the d.c. path for the emitter. I have also removed D4 and the amplifier keeps amplifying, I think they are used as some kind of...
  5. Leiser

    common-base LNA

    Good advice! I have done the layout according with a common-base configuration. It's more clear now and easy to understand. After checking I thought these diodes could work as a power supply reverse polarity protection for Q1, but C9 confused me. Well, if you have any comment they will be...
  6. 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...
  7. 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...
  8. Leiser

    Friis equation in ADS

    Hi, I have been able to calculate the NF with the Y-factor in ADS using an Harmonic balance simulation. Using the s-parameters simulation it didn't work.
  9. 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...
  10. 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...
  11. 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...
  12. Leiser

    how to know what type of PCB/substrate is

    thanks for you comments. Just a question, what does TMM stand for? I'll find out more information about Rogers 4003. I attach a pic of the amplifier. http://files.engineering.com/getfile.aspx?folder=2e90570e-29da-4e0c-9aae-94a9d9c2ac29&file=SDARS_amplifier.JPG
  13. Leiser

    how to know what type of PCB/substrate is

    you are absolutely right, in fact, last friday I talked to a colleague and showed me a PCB made with Rogers material and looked like FR-4 as it had green soldermask. I did what you proposed, and scraped off the top solder and I saw the material underneath using a microscope and I compared it...
  14. Leiser

    how to know what type of PCB/substrate is

    Thanks very much for you comments. For what I have seem it looks FR4. I have got some Arlon and Rogers boards and their substrate colour is tan to white whereas the board I am working with it is greenish. NF specification for SDARS SIRIUS is 09dB. Frequency band is 2320 to 2332MHz and 32 dB...
  15. 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.
  16. Leiser

    ADS question

    You are right. However, OEMs ask for AGCs that trigger at a fixed power. Some car receivers send the IF to the antenna block to adjust antenna impedance and amplifier gain, but it is not usual. I guess at the end of the day all comes to price, specially in Automotive market.
  17. Leiser

    ADS question

    Hi, thanks all for your comments. I will review the principle behind S-parameters. My question arose, because I was taking the S-parameters with the network analyzer for which you have to set the power level. For exemple, my design has an AGC in a FM amplifier, so I measure S21 for diferent...
  18. 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,
  19. Leiser

    ADS

    Thanks zappedagain, it really worked and I got my first closed-loop traces. Great!
  20. Leiser

    ADS

    Correct, but I do not have the pin diode model for ADS and I am modelling it as a R(I). The problem is that I don´t know how relate I to the op-amp output.

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