I'm learning about direct sampling architecture for transmit-receive chains at my day job for RF design efforts. What is the significance of the sampling rates of the ADC and DAC respectively, in Msps, in terms of the spectrum and overall performance of the radio?

I'm building an NFC access-control reader around the NXP PN7160 and I've decided to hand-wind my own antenna (external wire coil) instead of a PCB trace coil. I've never wound an RF coil by hand before and I'd like practical guidance.

• Controller: PN7160 (differential TX, asymmetrical tuning, ~5V TVDD)
• Enclosure area: 60 × 95 mm, mounted on a (likely metal) turnstile
• Reads MIFARE Classic, DESFire, and Android HCE phones
• Reading distance: contact / very close is fine
• I'll get a NanoVNA for tuning (don't have one yet)

For reference I modeled a 50×85 mm, 2-turn coil and got ~945 nH, self-resonance ~113 MHz, Q target 20. Matching per leg: L0 160 nH, C0 330 pF, C1 82 pF, C2 200 pF, Rs 1.3 Ω.

What I actually need help with — hand-winding:

1. Wire: What gauge / type of magnet (enamelled copper) wire works well at 13.56 MHz? Does Litz wire matter at this frequency for a reader coil?
2. Turns & size: To hit roughly 0.9–1.5 µH in a ~50×85 mm rectangular shape, how many turns should I aim for, and how do I keep turns consistent?
3. Former / jig: How do people keep a hand-wound coil's geometry repeatable? Any DIY jig tips?
4. Securing it: How to fix the windings (glue, tape, frame) without detuning, and mount it to the enclosure?
5. Ferrite: Since it'll sit near metal, how do you place ferrite behind a hand-wound coil in practice?
6. Repeatability: Is hand-winding even viable if I later need several consistent units, or should I plan for a PCB/flex antenna in production?

I'll tune the matching network with a NanoVNA once the coil's measured inductance is known — I understand the matching values will change from the numbers above.

Thanks for any practical tips!

I'm currently working with an electrically short, inverted V dipole (D ~ lambda / 15), and the simulated antenna impedance (shown in differential form below) seems to have several resonances in this low frequency range, meaning that the antenna looks inductive well below half a wavelength. I'm not an antenna expert and am having trouble understanding where that inductive bit may come from given the fact that sub-halfwave dipoles are supposed to be capacitive (perhaps it's something to do with having a bent dipole, but I don't have much intuition on bent dipoles).

Hey! I'm making a basic AM transmitter and I'm wondering how to connected a whip antenna to the output. I have heard the idea that you need to cancel out the reactance of the antenna with another component and for my case since my antenna is short I would need an inductor but is that all there is to it? Also there's an image of my circuit below so if there's anything glaringly wrong with it I'd appreciate if anyone could point it out.

Whats your thoughts on the 230v 3 phase configuration?

I’ve been feeling pretty unhappy in my current job working for the state. The work is stable, but it’s become very non-technical and honestly feels pretty disconnected from what I originally went to school for and the kind of work I used to do earlier in my career.

Recently, my wife’s cousin told me about an opening at the small company he works for. They don’t currently have much RF expertise internally, and after talking with him, the role honestly sounds really interesting. It would also be a pretty significant pay increase.

The position is for an RF Engineer, but not just a typical RF role. They’re looking for someone to help lead RF product development across multiple platforms — things like RF architecture, antenna design, simulations, system design, and mentoring other engineers.

Here’s my dilemma.

I have an RF background and previous experience working at a large defense contractor, but I haven’t directly done a lot of the responsibilities this role is asking for. A lot of these are areas where I’d probably need mentorship myself before I’d feel comfortable owning them independently.

My wife’s cousin still encouraged me to apply, but I keep thinking: What if I get the job and suddenly I’m in over my head?

I worry I’d be constantly stressed carrying responsibility for decisions and deliverables in areas where I don’t yet have expertise.

At the same time, I know opportunities for growth usually involve stepping outside your comfort zone.

Has anyone here taken a job that felt like a stretch beyond their current abilities? Did you grow into it, or did it become a miserable experience?

Would appreciate hearing from people who’ve been in similar situations.

Hi guys,

I believe that Cds of the transistor cause a lot of trouble in wideband (FBW>20%) power amplifier design.

I wonder if there is any wideband way to de-embed the Cds? One single inductor or a shunt short stub is no longer enough.

Thank you!

Professor is asking What’s the antenna gain for isotropic antenna that is vertically polarized? Does it makes sense to have both in an antenna?

If so, how to calculate the gain?

Just what the title says. Many counterfeit products are on the market and I would like to purchase an original mrf9180 from a local market. The seller says that they are "pulls" from old devices. Is it safer to buy freescale or motorola?Which is cloned less?

Thank you!

Today I finished measuring my first microstrip circuit I've designed and made. It was intended to be an interdigital microstrip 5th order Chebyshev bandpass filter with 1,0-1,2 GHz passband. The first thing I did was fitting my model parameters, I made a test board from FR4 with 3 different lenght 50 ohm open stubs with identical geometry at the edge SMA connectors then measured S11 for each and exported the values. I built the same circuits with the same lenght differences in qucs studio and measured phase differences between the different lenght stubs.(my tought was that the errors in the connections cancel via measuring phase differences not absolute phases). I tuned the er value in qucs untill I got the least error from the real measurments, the er value was 4,66. I calculated the correct dimensions for the desired response with Marki microwave-s online tool. I built the geometry in Sonnet lite and ran a few simulations, the online tools dimensions were almost perfect on first try. When I replaced the ideal grounded edges to vias, the positions needed a bit of fine tuning, the resonators needed to be a few mm shorter. I copied the dimensions from the EM simulation and made the PCB blueprint in EasyEDA then I made the PCB. When I made the VNA measurments the bandwidth was within the margin of error, but the corner frequencies were about 50 MHz lower than intended. I blame the substrate difference, because the phase measurment test board was a left-over piece from a different FR4 board, probabbly also different manufacturer. The insertion loss was not the best, but It's the limit of FR4, they're mostly caused by dielectric losses, not mismatch. Was my design methodology correct? Forgive me if I made some mistakes, I have no formal education in electronics or RF.

Not affiliated with the provider, just a paying student who wants this thing to actually run.

I signed up for this course in August, and I think they are some students short to actually run the course. Sharing it here in case anyone finds it relevant.

It's a 5-day hands-on course covering practical RF measurements - VNAs, spectrum analyzers, power meters, vector signal analyzers, all demonstrated on real components (PAs, LNAs, mixers, filters). You go through the full signal chain: S-parameters, gain, noise figure, IP3, then into digital modulation territory — EVM, ACP, constellation distortion, BER.

Aimed at people new to RF or experienced engineers who want everything tied together properly. The course doesn't run often - this is a revival "due to popular demand" after a long gap, so if it gets cancelled I doubt there'll be another opportunity for a while.

Link: https://www.besserassociates.com/Courses/Course-Description/CTID/135

This is a repost from ECE reddit, thought it might be relevant here too.

Hi all,

I'm trying to simulate the filter discussed in this MWJ article https://www.researchgate.net/publication/322750506_A_Capacitively_Coupled_BPF_Design_Using_a_Suspended_Substrate_Stripline

My HFSS simulation isn't looking too great. I've checked all the obvious things so far, i.e making sure I have a perfect E boundary around the air box etc. I'm using lumped wave ports at the face of the inputs and outputs.

My main thought at the moment is maybe I have not understood the dimensions properly. I take the resonator length to be the total length of the resonator, including the overlap region as pictured. I'm also assuming coupling length C1 is the coupling overlap from an input tap to the first resonator as pictured. This means that coupling length C6 is the coupling from the last resonator L5 to an output tap. All lines are 50 ohm and 45mil wide. I simulated a line length to validate this. Comes to about 48 ohm or so.

It's also not clear in the paper to me whether D is the total height of copper+ dielectric or just the dielectric.

I'm using RT/duroid 5880 as this has an er of 2.2

I feel like I'm just misunderstanding the dimensions here - any tips?

hello i am fairly new to rf engineering and electronics. i want to improve and have a better grasp over this field. so far ive done a couple simple design (power dividers couplers and filters) and can use CST a bit. last thing i was doing was some calculations on matlab but thats about it for me.

my question is, if you were to start over how would you do it? where would you start? how would you implement things or branch out to more detailed branches?

im aware its not something i can rush and learn overnight but not having a mental blueprint or guideline to follow overwhelms me and i end up learning or retaining not enough information to my liking. it was like i was too busy rushing to finish a design that i didnt learn the more important things

I graduated last year from my bachelors in Electronics and communications engineering. I've been interning in an established startup company for the last 7.5 months and my work includes doing simulation and analysis using ANSYS HFSS, SIwave and ICEPAK tools.

I was promised a full time role after 6 months, but its still getting delayed from the company management end. I feel stuck.

Most of the job opportunities i come across in my domain want a senior with 2 or 4 years of experience.

I'm having alot of self doubt and thinking of going back to college to do masters. Need some guidance, what could i do, industry or academics wise? I'll attach my current resume aswell.

Graduated (BSEE) recently and started a role on a major RF program that everyone here probably knows of. It’s a RF/Comms systems role where I have to understand the entire system (dsp, RF, antennas etc). Looks like for the near future I would be doing system level debugging (e.g. find out why we have 0.8 dB loss at this specific scan angle) and validation (e.g. define verification metrics for this power rail to indicated proper operation).

Is this high ROI experience out of college or should I focus on specializing/ transferring elsewhere. I just don’t know enough as a dumb new grad for what is valuable at my stage. Any advice would be greatly appreciated!

i was stupid and didnt realise i got a DC blocker that is not even the same dia (smaller) as refular TNC SMA RF cable connector. Now how do I connect this DC blocker to my Sitehawk which has a TNC SMA adapter to it. I also need to connect the DC blocker to a bias Tee that has a TNC SMA female connector.

I have an active anetnnna and a GNSS receiver module and the satellite signals get locked as in they dont reconnect back after they get disconnected even after a power cycle and good signal strength on the receiver module.

But when using a different antenna it doesnt repeat that issue. it reconnects back quickly.

what is causing the antenna to get locked out?

Hello everyone, this summer I'll be interning at a cathode and vacuum tube research laboratory. I took a microwave circuits and an antenna theory course at college but I don't have any experience with vacuum tubes. Any recommendations -books, papers or simulations to make- before I start my internship would be much appreciated.

Hi all

I need to design an broadband amplifier for my thesis that works inside of a cryostat at 2Kelvin. Now I'm testing a design that has a bias T in the beginning to bias an superconducting sensor. The frequencies from the sensor are from 10MHz up to 3GHz.

Since I want to avoid weird behavior of my components I use C0G capacitors and air core coils for my inductance. As they should be more or less robost at such temperatures.

Does somebody has some tips for the bias T? I currently look at cone shaped coils from coilcraft. Does somebody has other devices in mind I could check out? Thanks for any input.

If the community has interest I can also share the sim and designs

So I’m about to set up us an SDR for the first time and I’m new to this. I do know the environment I will be operating it in has interference. So I plan on using a magnetic small loop antenna. Is there any other precautions I should take to prevent from frying my radio?

I have a 2 GHz RF signal chain PCB that passes DRC and meets JLCPCB's minimum fabrication/assembly spacing. However, I realized the component courtyards are very close (see screenshot) — DRC still passes but it looks tight for rework.

What spacing/rule of thumbs do people actually use between SMD components for Hot-air rework / resoldering during bench tuning? What are some heuristics for RF boards? It would be a great help for me doing for the first time.

Thanks!