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  1. U

    Heterodyne detection, non-linear mixer and minimum detectable signal (2-way radar)

    I've been working on a transceiver system with BGT24LTR11 chips at it's core and I was unable to achieve necessary signal to noise ratio. I want to know whether it's theoretically possible and for that I need to understand how the terms in the title all intertwined. The following...
  2. U

    Magnitude function analog circuit (square root of sum of two squares)

    I have output of quadrature mixer and I need it's magnitude for current application. I want to build a circuit that does A = sqrt(I^2+Q^2), and it should also have duty cycle of 10%, so it should be triggered by that function. Can someone point me to a resource (website, book, journal, etc.)...
  3. U

    [SOLVED] How to estimate TSS of a mixer+LNA given noise figure and voltage conversion gain?

    https://www.infineon.com/dgdl/Infineon-BGT24LTR11N16-DS-v01_03-EN.pdf?fileId=5546d4625696ed7601569d2ae3a9158a I'm evaluating BGT24LTR11 RF transceiver and I want to do theoretical calculation of how well it behaves as a detector and I need to find it's TSS for that. All what's specified in the...
  4. U

    [SOLVED] Modulation scheme of this pulsed/two-frequency radar system

    https://imgur.com/aW3aDLV I'm trying to figure out how does this radar system works. Transmit Gunn diode is driven by mixing oscillator logic 3% duty cycle pulse with delta f logic, triggered on the falling edge of oscillator logic by a circuit with two MOSFETs, several resistors and one MOSFET...
  5. U

    Keysight ADS significant discrepancy between circuit simulation and Momentum 11 GHz!

    I'm designing a basic stepped impedance LPF, with -3dB at 34GHz. I simulated it with transmission lines first, then with microstrip lines. I get -3dB at 34GHz, as expected. Next, I import it into Momentum, use appropriate ports but my -3dB corner now shows at 22.8, that is, I am off from circuit...
  6. U

    How to terminate microstrip line with Z0 = 50Ω?

    If I have a microstrip line with characteristic impedance of Z0 = 50Ω, how do I terminate it with 50Ω to ground? In the literature it's always assumed load exists but how do I implement it, ideally with non-radiating microstrip/vias. Would putting 50Ω RF resistor work too? Resistor would add...
  7. U

    [SOLVED] Keysight ADS - patch antenna input impedance (possible incorrect EM setup)

    I'm simulating a patch antenna array but I don't understand the output. Keysight ADS LineCalc and Rogers MWI-2019 were used for synthesis and ADS Momentum was used for far-field radiation/pattern simulation. Here, a single patch was designed, accounting for effective dielectric constant...
  8. U

    Patch antenna "series-shunt" feed array impedance matching

    I'm trying to understand how is attached feedline matched. Thin lines are 100Ω transmission line. Matching structure looks somewhat similar to one shown here: Z0 = sqrt(Zs*ZL), ZL = Z0^2/Zs Going right to left, 100Ω source, through 70Ω quarter wavelength Z0, load is equal to 50Ω, or two 100Ω...
  9. U

    Data acquisition hardware for a ~50 kHz signal to import it to PC/do FFT

    As the title says, I have FMCW system and it outputs single-ended IF signal, frequency ranges from 1 kHz to 50 kHz (and a sync). Now, I want to capture it on PC, import it to Matlab and do an FFT or have an MCU do FFT. Now, my web searching skills clearly fail me because all I get are expensive...
  10. U

    [SOLVED] Significant discrepancy between ADS and Momentum simulations

    I designed a simple 90 degree branchline coupler in ADS, tuned it to my liking (my values were very close to theoretical). Now, I simulate the structure in Momentum and my curves are all off, I get 3 dB less since it got shifted by several GHz. Any suggestion and ideas why might my results be so...
  11. U

    Simulating X-band antenna in ADS Momentum, is it accurate to assume sheet metal?

    Due to skin effect of 0.6 um, most of the current flows on the edge, so will it be a good idea to assume sheet metal to reduce simulation time drastically? I've simulated several single-patch antennas and I didn't see a big change but if I try to simulate full-sized antenna with thick metal, ADS...
  12. U

    Open-circuit microstrip termination/match to air line

    I need to check EM properties of my antenna feed network, so to save time, I want to replace patches with equivalent open-circuit "loads", each with input impedance of 50Ω. How would I go about it? I can use stub matching to design a termination given the load, but how do I do that if my load...
  13. U

    RF capacitors with high Q/low ESR don't list ESR above 2 GHz

    I'm selecting a DC blocking cap to be used in X-band. Basically, I have a 50Ω RF line - DC blocking cap - 50Ω line. I'll use this as an example. **broken link removed** I want large capacitance and looking at the graphs of ESR/Q vs frequency, it seems that Q will go down with higher frequency...
  14. U

    Cascading 2 RF LNA, do I need to AC-couple them? Does DC-bias stays the same?

    I've used a single LNA and biased it according to specs. Now, if I want to put 2 of them in series, do I need to AC couple RF lines between them? Do I need to change my DC-bias?
  15. U

    [SOLVED] How to model absorbing material in ADS Momentum (reflectivity of 20 dB or more)?

    In ADS, one can define a dielectric material with ε*=ε'+jε'' and µ*=µ'+jµ'' with loss tangent being tan D = ε''/ε'. However, ε'' = conductivity/angular frequency, so the higher tan D, the higher conductivity is? How does it relate with reflectivity? I looked at the reflective materials and...
  16. U

    Has anyone been able to implement board-to-board (aperture) proximity coupling w/DGS?

    I know there are papers on improving characteristics of microstip antennas by putting a slot in ground planes to increase characteristic impedance but I haven't seen them use couple two traces from board to board.
  17. U

    ADS Momentum stacking multi layer and single-layer component simulations

    I'm simulating a 3-layer board (energy is coupled by a 'waveguide' from layer 1 to 3) followed by a coupled line bandpass filter. I've simulated coupler and am satisfied with the results. I've also simulated a bandpass filter (albeit, on a single-layer board) and am satisfied with it. I stack...
  18. U

    Through-hole via in Agilent Momentum

    I want to insert multi-layer via into and I drew one using this tutorial. https://abhargava.files.wordpress.com/2013/10/via-simulations-using-ads.pdf The problem is that in the tutorial, they simulate via filled with conductor. What I want is a through hole via with metal thickness of several...
  19. U

    [SOLVED] ADS Momentum G2 - cannot create EM model of microstip structure

    I have a filter simulated in Momentum. I want to use the filter as a circuit element to simulate it in chain with active components in ADS. I followed this video step by step to create EM model of my filter but when I actually import the filter EM model from my library, all I get is .ds file...
  20. U

    ADS or Microwave Office variable sweep

    I'm trying to do a variable sweep in ADS (or Microwave Office). I have 6 variables and I want to sweep them over frequency with the same percentage increments. So, variable A*0.9, variable B*0.9 through Variable A*1.1, variable B*1.1 in 1% percent increments (20 data points). ParamSweep seems...

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