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23 Threads found on Positive s11
Hi, I have a similar antenna to the one in this hfss design and I know that there is one or more mistakes inside because it doesn't give me the right radiation and gain results . For exemple. I think that I should have a positive gain and more logical s11 results but now from this design, I have a gain of -16 dB. Maybe it's because of my radiati
The amplifiers can be expected to have |s11| < 1, respectively positive dB value of return loss, respectively negative dB value of reflection factor. Surely not negative return loss dB value.
Hi, can anybody tell me why s11 and s21 show similar variation for a waveguide below cut off frequency of the waveguide? I am getting required operation above the cut off frequency, but below the cut off frequency i am getting positive values for s11 and s21 as the frequency approaches the cut off. thanking in advance.
I used the Agilent 85033C Cal Kit. When I finished the Cal procedure, I re-checked the short, open and load terminations on the VNA's Smith Chart, and they were correct. So I am puzzled by the positive s11 response. Sure it matches because you used them for calibration, but I think it's not a broken standard, ot
It's possible that your circuit oscillates at around 75 GHz and in Transient simulation the circuit's performance is affected by this oscillation. Check your current and voltages and check for beginning s11 and s22 if their magnitudes become positive at around 75 GHz.
although S21 is the graph that will define bandwidth..... but if you want to extract Bandwidth info from s11 than for general understanding u can say ... "the band on which the magnitude or s11 is below -10db or more (-20db, -30db etc) is your bandwidth... as because where S21 has its positive peak on the same frequency the (...)
With "positive s11 parameters", you mean |s11| > 1, a vectorial s11 value outside the unity circle?
hi please , when i simulate patch antenna , i find s11 for desirable frequency (fr) <-10dB (good adaptation) , but i find phase diagram of s11 positive and always >0 deg! what that means please (physically) and is there an error §?
Hello, I'm measuring a transistor device with the goal of obtaining transit frequency from the H-21 curve. I have open and short de-embedding structures to deembed using two methods outlined in the paper below: AN IMPROVED DEEMBEDDING TECHNIQUE FOR ON-WAFER HIGH-FREQUENCY CHARACTERIZATION the first one is the simple Y_transistor = Y_dut -
Hi, I am doing a CMOS Active filter circuit using Cadence Virtuoso with 50 Ohms ports at the input and output. After the simulation the results of the filter S21 is good and as expected (high gain, high Q), but the input return loss s11 shows a positive value. I was expecting a negative s11 value... does this has something to do with (...)
I've heard that getting positive s11 parameters is a simulation issue. Can someone please help me know what settings to tweak in this file so i can get the correct s11 parameters? Please, If you can solve it, specify what you did. Thanks. By the way, in this simulation, I'm trying to use glass to "shield" the RFID UHF tag antenna from the (...)
How to measure input impedance having negative resistance using VNA?? My VNA(Agilent 8753ES) doesn't seems to plot the area of s11>1. Is VNA setting same as input impedance having positive resistance? Or there another VNA setting ?? I want to check impedance in the display right after probing the circuit. Please let me know. Thanks.
I posted it before, anyone can give a clear answer? thanks I have some planar samples and designed a free space measurement, I calibrated the rectangular horn antennas THRU-REFLECT than put the sample in the middle of system. The result gives s11 and S21, at some frequencies s11 and/or S21 have/has positive values. Is it correct ? does it (...)
Need Help, I have some planar samples and designed a free space measurement, I calibrated the rectangular horn antennas THRU-REFLECT than put the sample in the middle of system. The result gives s11 and S21, at some frequencies s11 and/or S21 have/has positive values. Is it correct ? does it have any physical meaning? Thanks for your (...)
Hi, i am new with this software. My problem is i have wrongs in my simulation with gain. s11 and S12 must not be more than zero. i simulate resonators. i have some positive values in my simulation. see picture below please check your # is passes before simulating. Maybe the convergence problem messes up the matrix
Hello, You said you designed means simulated or fabricated a prototype!!! The s11 can't be positive their may be some problem with the device model parameter or file... Yes, it is unstable (oscillations), plot the K or B1 stability factor plots or stability circle measurements on smith chart.... See more here
I'm trying to simulate microstrip array in IE3D using periodic boundary. The simulation for single element pass OK but when I insert the periodic boundary the simulation gives me negative values for the real part of the input impedance and positive values for s11 in . I should add that the array I'm simulating has thick substrate so ther
hi how can i design a microstrip board with a response like this: delta(s21)=12dB through 6~12GHz with a positive fix slope s11 and s22 less than -5dBm infact how can i implement a S parameter matrix(vs freq) in a microstrip board thanks for your help
Hi TWang I think the positive s11 results show that our simulation hasn't convergence and we should change our simulation parameters such mesh, simulation frequency, feed structure,... i hope it'll be helpful
Hi, I have modeled a partch antenna (including the feed structure). But the problem is when I plot the Return Loss (dB) over the frequency range there is a section where the return loss is > 0 db and reaches a peak of 6dB. Thats doesn't make sence to me. It's a passive structure. Just wanted to check if that make sence in any way. thank
S21 is the Gain of the two port device! Pout/Pin If it is a lossy or passsive device the gain will be zero or negative (Insertion Loss). If it is an active device it should have some gain, making it a positive S21 s11 is the Input ReturnLoss Looking in to Port 1 Pin(forward)/ Pin(reflected Back) S22 is the Output Returnloss Looking in to
When LNA’s s11 is positive in dB at some frequencies is not necessarily to oscillates, but at that frequencies is potential unstable. The reason could be the layout design (external feedback), internal feedback inside the active device, the emitter (source) degeneration, the load presented at the output, excess gain at that frequencies, etc.
Following some indicators you can see that oscillations using the VNA. For example if you see a positive s11 or S22, definitely at that frequencies the amplifier is potential unstable. Also on S21 shape if you see some sharp edges there is a potential oscillation. If you change the bias and that edges are moving in frequency this is the oscillati