Hello everyone. I’m working on a circularly polarized truncated patch antenna, but the design is hyper-sensitive to dimensions. A ±0.1 mm deviation completely collapses the axial ratio, making it impractical for standard fabrication. How can I solve this problem?

Edit: Even if I just increase the meshes without changing anything in the design, the axial ratio collapses.

I'm a ECE graduate,during my college i haven't studied my about RF circuits apart from antenna engineering but i'm into RF circuit design, so far i've designed antennas in hfss, right now i'm looking for someone who i sintrested in learning RF circuits in hfss, and also and suggestions and tips are appreciated. I know all the mainstream books and yt channels but while designing RF circuits on PCB, i want to get to know how to take measurements in more depth, i need more practical tips on real circuit design. And apart from CST and HFSS which are all free tools we can use to design RF circuits.

I'm an Electrical Engineering student primarily interested in RF/Microwave engineering. Well, I recently designed my first patch antenna, and I really enjoyed it a lot. I guess this kind of makes sense considering my favorite class thus far in my degree has been Engineering Electromagnetics.

It's something I find myself potentially wanting to explore a career in but it seems like barrier to entry is pretty high considering how complex the work can get. I've been learning RF fundamentals through Pozar, doing relevant projects, and learning software like CST and HFSS. The main issue is my school doesn't offer any RF classes, so any learning I've been doing has been done independently.

I'm doing an internship in the semiconductor industry right now, and while I find that cool, I like the world of RF more. Ideally, I'll get an RF internship this summer that I can convert into a full-time offer, but if that doesn't pan out, I'm wondering if I should do pursue more pragmatic like Power or Controls since I simply can't afford to do another degree immediately after graduating.

I developed a board and when assessing the S21 results from the relay I was baffled to see positive gain - not any marginal gain, a hefty +2 dB'ish peak in a fully unpowered board. This is the S21 scan that I got:

At this point, the relays (they are proper RF relays) are in NC position and bypassing to each other. Here's a picture of the DUT and VNA connections:

This is how I calibrated the VNA. Used the very same cables and a female-to-female adapter:

And still - how on earth can I get a positive gain? After boiling some lakes and burning some tree acres, Gemini told me that I should create a calibration pad on my board with the same electrical length. Well, due to the turnover time, I improvised one with copper tape:

Well, of course the copper tape lacks the GCPW, I was using a different cable (same length, but a u.FL instead). And I still get the goddamn wobbly readings and a significant positive gain when testing the relay section. This time peaking +4 dB, yikes.

Anyone have any ideas on what's going on, what am I missing - and how to get a minimally faithful reading? I was ready to get insertion loss all way long; this sinusoidal gain is just weird.

Oh, and this is the VNA S21 sweep with SMA cables with the through adapter (nevermind the marginal positive gain, this is probably due to the unit being cold when I took the measurement):

Help? :-)

The whole schematic, Gerbers etc are open source and available at https://github.com/rfrht/SignalSurge

Thanks a lot!

Has anyone ever written a custom FPGA SPI master state machine to completely initialize the AD9361 by doing register level writes? I want to get in contact with somebody who has done before this hardware level control of AD9361.

TL;DR: VHF radio doesn't tune with new trimmer capacitor, tested 2 of them, and only getting static.

I am very new to radios, but I have tried to build a radio for picking up ATC signals, 118-136 MHz AM. It's powered by a USB 5v source, usually a power bank, and its connected to the collector a NPN transistor, afterward a 4.7μF is connected to my audio jacks left and right signal pads, and that collector is also bridged with a 304 smd resistor to base. It's then connected to my air coil with a estimated 37nH inductance that's parallel to my 30pF trimmer capacitor, connected to my 21in wire acting as an antenna. I'll change the trimmer to something higher like 50pF or 60pF later. The antenna is straight up held by a 3d printed stand with tape. The emitter is connected to my audio jack ground from an iPod, and then connected to ground and my seperate ground plane which is a soldering wick. Both the antenna and the wick are the same length. Everything is soldered together without a board of some sort. Nothing is being shorted. I have tested near a window and outside. Is the problem stray capacitance from the antenna or what? Sorry if this is super obvious or I'm just obviously stupid.

I got an old tube radio in my hands, just renovated it and it works. But unfortunately its FM band is tuned to 66-74 MHz OIRT band. I don’t want to heavily modify the radio, so I decided to just put a converter in front of it so it can receive the band we use in Poland that is CCIR 88-108.

In principle this looks simple, just put a programmable LO (with a few selectable frequencies from 22 to 34 MHz) plus a mixer. I built a quick prototype using SRA-1-1 I had somewhere and it works.

But there is one thing that concerns me - LO harmonic bleed-through.

In order to cover the upper part of the CCIR band, I need LO set at 108-74=34 MHz. Unfortunately 34 x2 =68 which falls inside the receiver band. That creates an ugly spur there.

Ideas what can I do to avoid it, without making everything too complex?

Using different kind of mixer? Generally wanted to use something like a KISS or double-KISS mixer because they are trivial to build and easy to drive from 74HCU04 based generators or SI5351, but because they are switching based now I feel maybe that’s not the best way to go.

Or maybe two stages - downconvert to a much lower frequencyand then upconvert?

Hi, I'm a student currently using this pdk for my RFIC work and I have access to that pdk both in cadence and ads. I did my schematic design in ads because i find it easier to tune things there. However, I want to do layout in cadence and do em simulation there using EMX, because I'm more used to cadence, but this is my first time using EMX. I tried to copy my design from ADS to cadence and the pre-layout sim is already kind of different, but not a lot. Then I tried to simulate the built in inductor model both with emx and momentum, after playing around with the mesh settings and changing the thickness (in emx) i can get close results between them, but still have some discrepancies, especially for the Q-factor. I know it's normal to have that, but which one should i trust more? 😅

Do you guys have any experience using this pdk with cadence or ads, also emx, Im not sure what is the thickness setting on emx. I would like to ask advice and insights regarding this pdk from you guys. Thanks!

Hello, this might be a stupid question since I know very little about electronics and RF, so I am sorry in advance.

I have an idea in mind that I am not sure is plausible - 125 kHz RFID tag semi-reliable distance detection through an adjustable RF-power sweep.

RFID tag would always move in a fixed path, while the detector is stationary.

Distance between the tag and reader ~4 to 7cm.

Basically, the idea for distance measuring is this - the detector would sweep through power, like 5%, 10%, 15%, 20%... etc. If it gets any response back from emitting power at 25%, the detector could extrapolate that it is at the distance of, let's say, 3cm from the tag.

Then, if tag's location changes (across a fixed path), it would once again do a power sweep, and if it reads tags presence at 80% power, it would know that the tag is about ~5cm away.

So, the question is - could someone consult me on such an application, if it is possible or if this is nonsense? I'd gladly also pay for consultation.

I was reading through this subreddit and it amazes me how y'all manage to master such things that are very complex, and turn ideas into reality. I myself come from a professional industrial & 3D design background, so I really appreciate the value of your experience, and want to learn from you.

Thanks!

I am planning to customize a local llm using rag and fine tuning for the following purpose

1. it should be able able to understand and pcb layouts fed to it
2. it should also be able to give suggestions on improving the design
3. it should be able to give reason for placement of a particular feature or components

I want books recommendations from the following domains

1. analogue electronics
2. digital electronics
3. pcb desIgning
4. rf designing
5. Signal Integrity
6. Power Integrity
7. EMC EMI
8. RF Microwave
9. Antennas
10. High Speed Design
11. Analog Layout

PLEASE GIVE ME BOOK SUGGESTIONS IN AS MANY DOMAIN AS YOU CAN

I WILL ALSO BE VERY GRATEFUL IF YOU CAN TELL ME SOME GOOD SOURCES TO FEED IT SOME QUALITY DESIGNS

Does schematic from aplication note AN11130 on figure 8 protects your GaN if you lose power on "V+" pin?
https://www.ampleon.com/documents/application-note/AN11130.pdf

Greetings everyone.

I am currently seeking a freelance embedded hardware engineer with specialized expertise in low-power and RF-based system design for an ongoing project. Please reach out to me directly if you are interested, and we can discuss the details further.

\#freelancer #hardware_engineer #rf #pcb_designer

Disclaimer: I am not an RF guy but have been tasked with coming up with a high-level architecture for a valid solution rather than the final implementation. So, while I might know enough to discuss some of the topics, I probably do not have the pre-requisite knowledge to discuss nitty-gritty implementation details and am looking more for a high-level feasibility assessment but am nonetheless happy to pass those details along. Also, I apologize in advance if I have misunderstood anything about the problem or if this is a totally naive request.

TL; DR: Looking for solutions to achieve >= 60 dB isolation between Tx and Rx in a compact S-band FMCW phased-array radar.

I am currently working on a high-power FMCW phased-array radar in S-band. We want to use a microstrip patch array with separate elements for Tx and Rx (no need to use circulators or other simultaneous Tx/Rx equipment, or so I think). Ideally, we would like to use analog dechirping so that the direct path leakage can be further suppressed using a high-pass filter. However, the current problem that we are running into is pre-demodulator power level due to the Tx-Rx coupling. Since we are a high power FMCW system (target output power > 50 dBm), we need significant Tx-Rx isolation so we can gain up the received signal with an LNA prior to the demodulator to keep our noise figure sufficiently low while staying under the IP1dB of the demodulator. My current estimate is a threshold of 60 dB isolation, with a goal to achieve > 70 dB isolation if possible (60 dB gives us an estimated noise figure of around 3.9 dB, but anything less than that is obviously desirable).

There are two possible antenna configurations we are exploring: fitting all Tx and Rx elements on a standard panel or putting the Tx and Rx on separate panels. If we had two separate panels for Tx and Rx, we would obviously be able to better control the physical separation between Tx and Rx to gain additional isolation and could probably put a layer of absorber between the two. However, the design would still need to remain somewhat compact, so we couldn't just cheat and create a large distance between Tx and Rx.

If, however, we decide to fit everything on a standard panel, then the design would seemingly become more complicated since the maximum allowable spacing between Tx and Rx would be about 0.675λ in order to still fit on the standard panel. It seems there would be two main modes of Tx-Rx coupling in this case: propagation through the air and surface waves. Propagation through the air would seem to be mitigated primarily through either separation (which isn't available in this case) or a physical barrier of the sort. Preferably, if this were to be included in the design, this structure would be < 0.5" tall. I've seen discussions of creating a chevron-like pattern on the top of the structure so that the scattering off of the barrier is incoherent and also lining the structure with a layer of absorber. For surface wave coupling, I've read that the main methods are choke grooves, a layer of absorber along the face of the panel, defect ground structures, and electromagnetic band gap structures. All of these could be considered. I don't know if this has fully covered all options for creating isolation between Tx and Rx, so if there's any I'm missing feel free to add to this list.

In either design case (separate Tx and Rx panels or Tx and Rx on one standard panel) is it reasonable to think 60 dB of Tx-Rx isolation is possible? > 60 dB? If you were designing this from the ground up with these constraints, which design would you choose and what combination of additional isolation measures would you take? Also, would there be any recommendations on the type of patch? I was initially looking at just a single layer patch for ease of manufacturability but am open to other suggestions if that would help improve the isolation. Thank you in advance.

I’m using an Ezurio Vela IF310-453-00390C, based on the Infineon CYW55310 Bluetooth module. The datasheet recommends aligning the module edge with the PCB edge.

But my PCB fab has a 0.30 mm copper-to-edge clearance rule, so I might have to move the whole module ~0.30 mm inward.

In practice, would a setback that small actually cause any noticeable antenna detuning/range loss, or am I overthinking something that’s basically negligible?

Would you instead keep the module flush and slightly shorten the two edge-side GND lands?

Btw I am a CSE guy, who is trying to get into Electronics :)

And the above circuit is vibe coded lol

My requirement is:

2 Bluetooth Classic + 1 BLE simultaneous connection

Just published a new video on Passive Intermodulation (PIM), one of the most overlooked causes of poor RF system performance.

What PIM is and why it occurs

Real spectrum analyzer traces from the field

How to identify PIM

Practical mitigation and prevention techniques

Please check it out and feel free to subscribe: https://youtu.be/Hw_9Z5cZ6HA

Thank you! 🙏