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I have a question on the effect of IM2 vs IM3 in I or Q-channel individually, versus at complex baseband:
In a quadrature downconverter, assume each path (I or Q) contains an LNA and mixer which contribute IP3 or IP2. The IM3 from the LNA is at the input to the mixers, so the IM3 along with the...
Hi all,
I wanted to test the input impedance of a simple common-source transistor with inductive degeneration, and I found that Zin varies considerably with the load impedance (for example simply changing Rload from 100 to 500 ohms). This is not what I expected, because even with a finite Cgd I...
Thanks rohitkhanna, I found another picture (taken from a paper) to better explain my question:
The reasoning here is that since the diodes are reversed (and LO is out of phase), the small-signal IF currents i(t) = g(t)*v(t) add in phase at the IF node, where g(t) is the diode conductance...
Hi all, I have a quick question about how a single-balanced diode mixer works. Here is a picture of the circuit:
Suppose the RF voltage has amplitude Vrf and LO signal has amplitude Vlo, and there is a RF bypass to ground at the node between the two diodes. Then the amplitude of voltage at...
Hi volker_muehlhaus, I tried moving the port to the center of the 50 ohm line and it did produce different results, so perhaps Momentum is able to capture the effect of attaching the transistor leads at one corner? I'm not sure how to go about de-embedding the transistor side port in ADS. I just...
Enjunear - the device is this one:
In layout window I put down 4 MLIN components (1 gate pad, 1 drain pad, and 2 source pads) and sized them to fit the recommended PCB pad layout (these are shown in the picture I attached earlier). I tried rotating but the separation between each pad is too...
Thanks again guys, I've tried all the options suggested, so far it seems like putting the transistor pads at the corner of the 50 ohm line doesn't affect the performance *too* much and I should be able to get the desired results with some slight tuning. But I don't know if I'm simulating this...
Thanks pewang and enjunear for the help! In my case the transistor pads are much smaller than my 50 ohm lines. For example, my 50 ohm lines are ~3 mm in width and the transistor pin pads range from ~0.6-1.5 mm in width, so I definitely cannot just align all the pins at the center of the 50 ohm...
Hi guys,
I have a question about doing layout in microstrip. If I have a 50 ohm line that I want to attach to the gate/drain/source pins of a transistor package, can I just solder the transistor on a corner of the 50 ohm line? Or do I have to create a short length of line with width that...
Hi all,
For LNAs what are good ways to stabilize the transistor at low frequencies? I'm working on an LNA and observe that its stability factor (K) is essentially 0 around f = 0 Hz (I'm using ADS to simulate K) and then quickly jumps up to a high value before coming down again. I'm wondering if...
Thanks SunnySkyguy, it would be correct to call |S21|^2 the transducer power gain right? Which is equal to available power gain in this case since my output is ideally a conjugate match?
Hey guys,
I am designing an LNA and have a quick question regarding the different power gain definitions, e.g. available power gain (Ga), transducer power gain (Gt), etc. From my understanding Ga assumes conjugate (optimal) match at the output and depends only on the input match network...
Hi, I have a basic MOS common-drain amplifier as described below:
- Drain connected to 5 V DC
- Gate connected to an AC source on top of a 3 V DC source
- Source connected to a 200 uA current source with a resistor R connected in parallel. The parallel connection goes to ground, and the...
Hey guys,
My friend who works at this company donated to me a couple old Dell Optiplex computers in his group that have been obsolete for a few years and subject for disposal soon. I would like to turn them into cheap workstations -- afterall they can still run most engineering software...
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