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I am a 2nd year ee student. I would like to pursue a career in rf/signal processing/telecommunications. This semester, I ma doing research with a professor doing a project on a wifi network. I was wondering what improvements I could make to my resume and am also hoping to get a bit of career advice. Does my resume look competitive so far for a 2nd year ee student and what jobs/internships should I try and go for now since most signal processing/rf jobs are usually for masters or phd students. I also did my first year of college in 2022 as a computer science major before switching universities in 2023 to major in electrical engineering. Thanks.

I am interested in visualizing the fringing field effects at the antenna ends. Are there any specific visualization options in HFSS that can highlight the fringing fields? Any tips would be much appreciated!

Hi all, I am Just messing with a small RF LC circuit and I realized that without adding two capacitances on either side of the parallel LC circuit I can't seem to pick up anything on the VNA. With the two capacitors though, the signal becomes very clear and I see a nice resonance.

So here I made a design of Rectangular cavity resonator in order to measure the water content of different materials. My question is that in the middle it’s a object with different material ( i.e whose water content we want to measure by looking at the Rf and bandwidth) my question is that did I introduce the cut right and introduce the brick with different Er inside it correctly? I am concerned about either to reduce my cut size as my middle brick size but I am think in real life we can have different sizes object but the cut remain to be the same please comment and guide me.

I am a 2nd year ee student in Tennessee and I am interested in RF engineering. I am doing research with a professor adjusting neural networks on the transmitter and receiver side of a wifi network. I do plan on doing a ms degree and maybe a phd. I wanted to know what else I could do to as an undergrad to do a career in Rf and good cities for rf engineering?

I hate to be annoying but if someone could please answer my previously asked question on nyquist stability test, it would mean a lot to me. thanks.

I am learning about oscillator design and encountered the Nyquist test. I wanted to check my understanding.

A_cL=A_oL/(1-A_oL*B) is the closed loop gain for a positive feedback voltage amplifier. The A_oL*B is the loop gain when the feedback network is broken and not summed into the input. If there are right half plane poles, the oscillator will be unstable. This is required to start the oscillator. As long as the loop gain is more than 1, it will have right half plane poles. Also the nyquist plot will encircle the critical point 1+0j. As long as it encircles 1+0j, it is unstable. However, for the oscillator to stabilize and maintain steady oscillations, the poles must move on to the imaginary axis at which point the loop gain A_oL*B is equal to 1 and the positive feedback amplifier is stable (i think?). The direction of the circle indicates if there are more poles than zeros or more zeroes than poles. poles allude to those of 1-A_oL*B and zeroes allude to those of A_oL*B. The number of times it encircles the critical point is given by N=Z-P where Z are zeroes as mentioned before and P are poles as mentioned before. edit: if you have N=0 then it will be stable. if you have N>0, it will be unstable and if N<0 it will also be unstable as both cases indicate an encirclement of the critical point.

This is the part i am unsure about. I thought stability was reached when the poles lie in the left half plane. the imaginary axis is a borderline case where the critical point, 1+j0, isn't necessarily encircled but the tangent of the circle passes through it.

I was reading chapter 1 of the art of electronics and i came across this circuit that explains that the boost converter results in a output capacitor (C1) voltage that is 2Vin. Can someone please explain to me how this is the case. We assume the switch closes with a duty cycle of 50%. The equivalent buck converter has the switch before the inductor and it is 0.5*Vin. Here is the picture:

booster

Anyone got any tips on how to get/companies that give out free samples (ICs, passives, etc.). (Just a lowly grad student who doesn't want to shell out their entire paycheck for one AD chip haha). So far I've had some level of success with Rogers for circuit boards and analog devices (in very limited quantities), but I'm wondering if any of y'all have other suggestions on where to find stuff. Thanks!

I have tried to R.T.F.M., but I am still not understanding this.

When building a balun/matching transformer to go from a higher-impedance antenna to a lower-impedance coax line, does one use wire inside the balun that matches the higher-impedance antenna or the lower-impedance coax? I fail to understand why there is not an impedance mismatch either way, where the balun connects to one side or the other.

Option One—use wire in the balun that matches the lower impedance of the coax. In my limited and likely faulty understanding, this would cause an impedance mismatch where the lower-impedance wire connects to the higher-impedance wire on the antenna's side of the balun.

Option Two—use wire in the balun that matches the higher impedance of the antenna. In my limited and likely faulty understanding this would cause an impedance mismatch where the higher-impedance wire connects to the lower-impedance wire on the coax's side of the balun.

My scenario is that I have a 300-ohm-impedance balanced antenna and an L.N.A. designed for a 50-ohm-impedance unbalanced input. I would like to build a 6:1 balun to connect them. I found this design: https://vk6ysf.com/balun_6-1_V2.htm

I understand that solid-core 20-A.W.G. wire is a decent enough match for 50-ohm coax. If I follow the design in the link, above, with 20-A.W.G. wire, how does it not cause an impedance mismatch where the 20-gauge wire coming from the balun meets the antenna?

I apologize if this is a stupid question.

Hey there, RFElectronics! o/

The attached circuit is a RX Mute circuit that I sourced from a amateur radio transceiver (FT-450).

What I grasped from this circuit it pretty much grounds the RX chain from the radio when the transistor Q8 is biased. This is a circuit that works in HF frequencies (0-30 MHz).

I would like to reuse this circuit in VHF/UHF frequencies (144-450 MHz). That said:

1. Do I have to change the values of C26 and C28?
2. The Q8 BJT is a last-time buy 2SC2714. I would like to replace it with something else and make the design future-proof. The thing is, this transistor has no directly compatbile parts, being the key feature a hefty 30V Vce. Considering that I'll be using 5V bias voltage at the collector, can I safely replace it with a transistor with a Vce in say, 10V ballpark?
3. Any considerations for inductor L7 due to VHF/UHF?
4. Any other notes?

For what is worth, this isn't a 1-800-domyjob, this is an open source BPF/AMP for ham radio, and soon to see the first commits in Github.

Appreciate your time!

Hi Good folks,

I feel like this sub can help, and I appreciate any advice given! I am a senior antenna engineer, have a couple of novel industry antenna patents under my belt, about 5 years of experience. I am looking for a more research forward position in a company with a good culture that is focused on phased array design, mainly on either east or west coast, though my preference is DC and Redmond. I should be able to get a SC, but I have never had one before.

I have experience with metamaterials (lenses, and TAs), phased arrays (mainly K, Ka, but I have worked on Sub X-band Puma array designs), Cassegrain, and prime-reflector design.

What set of topics I should master before I am able to do something like that by myself? If I can handle the simulation on ansys with no restrictions would I be able to design one?

I want to EM Simulate the transistor layout interconnect to the gate of the MOSFET

In the EM simulation I want to simulate to up to 30 GHz say and have the interconnect be a S parameter Box I connect in my regular circuit simulation connected my transistor

I have to exclude the 0 Hz, or DC point from the EM Simulation because when I connect the S Parameters of the EM simulation to the transistor it won't bias up if I don't - correct ?

Hello!

So i git interested in rf around a year ago when i was designing an antenna for the first time, which was super cool and that's how i got interested in the field. However, idk what should i focus on. Some kind people have sent me books in various topics starting from antenna analysis to communication system design. However, as i began reading them, i was not sure that i was learning anything as every formula felt a little detached from anything realand i didn't immediately see the practical usage for them, so i was kinda abandoning one book after another.

Should i then focus on some sort of projects not lose motivation? If yes, what kind of? I had try to build a simple superheterodyne receiver and it was semi-successful

Thanks in advance!

Hello everyone,

I would like to ask for your kind help with the antenna simulation.

Could somebody tell me how to properly feed a helix antenna in 4NEC2? I need a reflector behind it and don't want to use the perfect ground option.

Thanks in advance!

https://preview.redd.it/ef1bfrxye73e1.png?width=568&format=png&auto=webp&s=9b62e3707938e0e54d1940c38a71716d138b3b8d

fcc regulations aside, is there any specific reasoning that you could not have 10 different wave lengths and antennas all receiving at the same time with display? barring the equipment was there to support the endeavor. in something like a pyramid pattern visually speaking.

I found out that QucsStudio 5.8 was released last saturday and it changed it´s name to uSimmics.

Home - QucsStudio

I never figured out why it is 2Vcc. Can someone please explain this?

With a resistor, it’s VCC.

A picture is better:

https://preview.redd.it/562iv7i8xw2e1.jpg?width=809&format=pjpg&auto=webp&s=5e38705ab7e070c748fe0af24fa314b667bb8b41

So... I my thoughts... the 12V USB output is really dirty and some how affecting the output of the Phone's 3.5mm audio line. The stuff coming out is white noise or a fairly constant static. If I unhook the power from the phone, the noise goes away and the audio coming from the 3.5mm jack is clean.

My 3.5mm audio cable is a few inches short from dash to AUX jack, so I happen to have one of those 1-to-2 3.5mm jack splitter... I intent to use it as an cable extender.

But just for the heck, of it, I hooked it up as shown in the 2nd configuration and ... suddenly, the noise is gone.

Is it because the power is dirty that I'm getting noise from in the 1st configuration?

Why does the noise go away in the 2nd configuration?

I'm going to try an audio cable with a choke on it to see if it makes a different using the 1st configuration. But I don't think it will do anything since I think the noise is from the phone rather being introduced by the 3.5mm cable.

EDIT:

• The phone has an FM radio and it uses the cable as an antenna.
• Car is a Prius. The 12V is feed by a HV battery DC to DC converter. The alternator in the car feeds the HV battery. Noise is heard with or without the internal combustion engine running.

This is kind of a long shot. I realize RF PCB design is a niche area and not many people do it. It seems like softare defined radio is more popular. So far, I have only encountered PCB design books that explain PCB design in a general sense without accounting much for issues that arise in RF.

Can you please recommend books and online resources that teach you how to design PCBs in RF?

I have an update from my post yesterday.

With the help of u/erlendse and u/Defiant_Homework4577 I came to understand (I have never studied R.F. engineering) that the shapes of coax connectors really matter. By, let me call it, adapting two of the grommets, I was able to fit everything in the plastic box and use coax connectors straight through to the board. See picture (still not winning any beauty contests, I know).

https://preview.redd.it/gst4ov6ogr2e1.jpg?width=1836&format=pjpg&auto=webp&s=5086b74102aa70d1d3e385222e28f8fcb0325de6

The strange behavior disappeared. Absent the D.C. voltage no signal passes, and with it signal passes.

Thank you for your help!

I am generally happy with this result and I think it will help with the new antenna I'm putting up in the backyard that will have a 100-foot or so coax run to the combiner/amplifier.

One potential issue remains. The two weakest channels, which I receive well enough without an L.N.A., are unreceivable with the L.N.A. as it is now. I think, but do not know for sure, that the L.N.A. is amplifying too much noise into those frequencies for the TVs' tuners. I have already halved the voltage to the L.N.A., to six volts, which is on the lower end of its voltage range for variable-gain amplification. See https://www.amazon.com/HiLetgo-0-1-2000MHz-WideBand-Amplifier-Noise/dp/B01N2NJSGV/ ("When the power supply voltage changes in 5-8 v, it can be used as a variable gain amplifier, gain increases with the increase of the power supply voltage, which suitable for radio frequency receive front-end circuit, using DA control power supply voltage, to control the gain of the amplifier, automatic gain control").

I am considering four things:

1. lowering the voltage further
2. building a 6:1 balun to connect the 300-ohm antenna to the 50-ohm L.N.A. Right now I have a 4:1 matching transformer meant to go from a 300-ohm antenna to 75-ohm RG-6. (The only cheap PCBs I could find for LNAs were all 50-ohm with S.M.A. connectors. My initial research indicated that building a matching transformer to go from 75 ohms to 50 ohms would be a wash; I'd lose as much from the additional transformer as I am now losing to reflection. The idea now would be not to use the 4:1 at all, and just build a 6:1 to go directly from the antenna to the L.N.A.)
3. placing FM and 4G/5G/L.T.E. filters before the L.N.A. input.
4. running the D.C. and ground (brown and white-brown) wires around the perimeter of the box instead of directly over the PCBs.

Are any of these likely to make a difference?

Is there something else I should try?

Once again, I thank you for your time and consideration.

Hello everyone. I’m currently a test technician that just got a new position working in labs instead of the production/manufacturing side. I can tell after about a month that two things are true; 1) this is awesome and I’m enjoying it a lot and 2) I have a lot to learn. My main focus is of course RF. I have good trouble shooting experience but what I don’t have is a ton of knowledge in developing ways to test new parts to replace obsolete parts. For example, because of a lack of some other equipment that is currently in another country, we used a radio, 2 tone audio signal generator, an antenna coupler, an antenna simulator, and various coils and capacitors to induce a 5k voltage on the output of the coupler to test HV relays. I had never heard of an Rp number until this. I have zero college experience with this (I plan to change that). I’ve learned everything necessary to learn the basics of my job rather well. I have a passion for physics and that translates over lol

I was hoping that I could start filling gaps and gain better understanding. Please, any and all suggestions are welcome. You guys look like you have a fantastic group here. Thank you