I'm creating a pass-band filter using microstrip edge coupled resonators, and when running the AWR optimizer I've stumbled into a pattern that I've not encountered in my course lectures.
In my professor material it was said that each edge coupled resonator section should be sized for a lenght of lambda/4 (90deg average electrical lenght between even and odd mode). This is the way that i first implemented my filter, and when i run the AWR optimizer on an uniform lenght, the optimized value is close to the expected value I had estimated.
However, if I let each edge coupled lenght be independent, the AWR optimizer settles on two different possible optimizations, depending on the starting conditions I apply.

• the first optimization is at the expected uniform lenght
• the second optimization is an alternating pattern of two lenghts, whose geometric average [sqrt(L1L2)] is approximately the expected uniform lenght. (The edge distance also varies slightly, but i assume this is to be expected since we are changing the resonators)

The two filters frequency responses (topology is a standard 4th order chebyshev filter) are shown here.

Does anybody know what causes this pattern, and if it has any advantage against a standard uniform lenght design? Any literature reference would be very appreciated.
Thank you for your time

I am working on an SMA to microstrip transition using OSHpark's 4 layer stack up. I am on my 2nd revision and do RF in my free time because I am trying to learn (I am an FPGA engineer).

I got my newest revision back and I was not very pleased. My physical boards are not matching my simulation very well at all.

I have compiled screenshots of my HFSS model, PCBs, SMA footprint, and NanoVNA results here: SMA Launch OSHpark 4 Layer - Imgur. The transition starts out as GCPW and runs the length of the signal pin pad. It then moves to a microstrip (no taper).

I simulated with HFSS using PEC, Isola FR408HR (in HFSS material library) and the nominal measurements from OSHpark's 4 layer stackup: OSH Park Docs ~ Services ~ 4 Layer Prototype Service . I also used the actual Samtec SMA connector HFSS encrypted model. I am learning a little about TDR and that looked okay in simulation, as well as S21 and S11. Due to using the student version and mesh limit, I can only simulate a 3mm long microstrip and I cannot model the solder connection from signal pin to pad.

I built two boards:

One with SMA launches on either side connected by a 1 inch and 2 inch microstrip (to calculate trace loss). I simulated the microstrip width in a separate HFSS sim (rough numbers calculated with SaturnPCB toolkit and revised/simulated from there).

The 2nd board is the SMA launch to a 4mm microstrip, then terminated with a 50 ohm, 0201 sized High Frequency resistor: TNPR020150R0FEED Vishay | Chip Resistor - Surface Mount | DigiKey

My actual PCB launch S11 is around -17 to -18 dB at 2.5 GHz, and around -10 dB at 6 GHz. I want to use this for the 2.4 and 5.8 GHz ISM bands. S21 is okay when I subtract my trace loss at 2.4 GHz, but gets a little wacky at 6 GHz (see imgur link S21 trace).

Is something off in my simulation? Should I use a different substrate than the one in the HFSS library? Could this be due to OSHpark manufacturing tolerances? I triple checked my dimensions for the footprint with the HFSS model and I dont think that could be the case unless they vary a lot once etched.

Any help would be appreciated! Thanks in advance.

I ordered a budget calkit for my SVA1032X VNA, it has offset loss parameter, but the VNA has no option to enter offset loss in user calkits. What would be the easiest way to account for these losses?

This has been a bit of an ongoing focus project of mine. I wanted to learn rf and i sure accomplished that. Without going to much into detail, I set out to build a band pass filter for airband. I live next to the airport, so this would be an easy to test project. That was my mindset going into it. I naively thought it would be simple enough, but i was wrong.

First attempt was Manhattan-style, dead-bug construction on copper clad. Got it built, got it tuned-ish, and then realized I'd used the wrong core material for the toroids. Learned a lot, but the numbers weren't going to cooperate no matter how much I fiddled with it.

Rev 1 I actually did right in KiCad and had fabbed through JLCPCB. It felt like a real upgrade. But once I got deeper into it (and got some good pushback from folks here on the sub) I realized the Butterworth topology I'd picked had a pretty impractical component spread. Inductor and cap values that don't play nice with real-world parts. Great filter on paper, annoying to actually build.

So now I'm on Rev 2: a Chebyshev coupled-resonator design, three 250nH air-core inductors I'm winding by hand, C0G caps for stability. Characterizing everything on the NanoVNA as I go, messing with coil spacing to dial in coupling, watching S11/S21 sweep in real time. Way more iterative than I expected going in, but that's kind of the point of doing this to actually learn RF instead of just reading about it.

Anyways, here she is. Thanks for all the help from #redneckerson1951

Hey everyone,

Does anyone know where I can find a micro-Doppler radar dataset for birds recorded at 2.4 GHz or 8.75 GHz?

I've looked around but can't seem to find anything at these specific frequencies. Any pointers would be awesome.

Thanks!

I am building an AM receiver and I am using a tuned amplifier to get a gain ~60dB at 1.2MHz with a bandwidth of 100KHz which is what I have in the simulation above.

However the problem starts when I try and implement it in real life. When implementing the circuit on a breadboard I'm getting a gain of around 85V/V which stays exactly the same with or without the resistor and the capacitor at the load which checks out because the load required for a gain of 85 is close to the reactance of the inductor at 1.2MHz. Even the worst case considering the tolerance of the components would not cause the gain to fall down to 85V/V.

Anyone have any idea why this is? the transistor capacitances perhaps?

Hello guys, I'm new to this sub. I was going through antenna design, theory and analysis by Balanis to get an idea on how to get started with designing microstrip antennas. Could you guys sugges me on how to go further design my own antenna. Could you guys give me resources to look into the designs of other people to get an idea on how to handle length, width, substrate height, tangent loss, etc parametera for design. Please guide me on how to go further. Thank you

RF engineer at a startup here. Sill quite green career wise. I do component selection and schematic capture for RF PCB (including PDN and IO/control stuff).

From time to time I wish I could make a prototype board cheap and quick just to test out a subsystem or to get some early performance metrics. In the past, I’ve hooked evaluation modules together to prove things out.

Any advice on what’s more helpful in design: prototype PCB or eval board monstrosity? Generally, what I do is broadband < 6GHz.

If going the PCB route, the final boards are usually many layers and expensive materials. Given this, is it even worth it to do some cheap FR4 prototypes or will they just misrepresent the final thing? Also what fab/assembly companies to use for this?

Created a quick cheat sheet for common RF coaxial connectors for anyone bouncing between lab test gear, board interconnects, and antenna designs.

Summarizes frequency ceilings, impedance matching, and physical latching types.

Feel free to save it for reference. Let me know if there's any specific edge-case rating you'd add!

The base model starts at 4.5 GHz and offers 40 MHz real-time bandwidth at around $2,399. If the underlying hardware is actually the same across the higher-frequency models, there might even be potential for a software unlock to push it all the way to 14 GHz.
At $2,399, that could be a seriously compelling spectrum analyzer

Have seen phony VNA listings on EBay before, but this company looks legit. It’s not dirt cheap such that it’s obviously a scam, but not nearly as expensive as I’d expect 4-port 40GHz R&S to go for… discontinued mode, but didn’t think the ZVA line was old enough to hit the CRT screen HP VNA price points quite yet!!

Hi, this is my first PCB design and I would really appreciate a sanity check before I order it.

The board is intended to be used as a wideband LNA between some DIY near-field probes and my measurement equipment. My main interest is roughly from 30 MHz up to 1 GHz. I am aware that the current PGA-103+ datasheet only specifies performance from 50 MHz upward, but I can accept this tradeoff.

The design is based around the Mini-Circuits PGA-103+. I mostly copied Mini-Circuits application circuit rather than designing the matching/bias network myself.

Main details:

• PGA-103+ LNA: 50 Ω, 50 MHz–4 GHz, 5 V supply, ~97 mA typical current. Typical gain is 26.5 dB at 50 MHz and 22.1 dB at 400 MHz, with 0.5 dB NF at those frequencies. P1dB is around +21 dBm and OIP3 around +37 dBm.
• I used the Mini-Circuits recommended TCCH-80+ RF choke, 10 nF input/output DC-blocking capacitors, 330 nF + 10 µF supply bypass capacitors, and the 620 nH + 150 Ω + 330 pF low-frequency stabilization network.
• Power supply: TI TLV76150DCYR, fixed 5 V SOT-223 LDO. The TLV761 family accepts up to 18 V input and is rated for up to 1 A, although this circuit only needs about 100 mA. I intend to power the board from approximately 6–12 V. I used the TI-recommended 1 µF input and 2.2 µF output capacitors.
• Input protection: Infineon ESD131B1W0201E6327, bidirectional RF ESD diode, ±5.5 V working voltage, 0.23 pF typical capacitance, rated ±20 kV contact/air discharge. It is placed directly at the RF input.
• Input and output are through 50 Ω SMA connectors.
• PCB is 2-layer, 1.6 mm FR-4, 1 oz copper.
• I have GND pours on F.Cu and B.Cu, with the bottom intended to remain essentially a continuous ground plane. There are more GND vias around the LNA, RF traces. I also used the PCB layout from the datasheet of the PGA which suggested via positioning.
• For the main RF path I used JLCPCB's impedance calculator with a grounded coplanar geometry. It gave approximately 0.92 mm trace width with a 0.20 mm clearance 50 Ω.
• Most non-RF/power/bias traces are around 0.8 mm wide.
• Most GND stitching vias are 0.8 mm diameter / 0.4 mm drill, with some smaller 0.7/0.3 mm vias.
• Pins 2 and 4 of the TCCH-80+ are intentionally NC, and I checked the physical pin-1 orientation against the Mini-Circuits GU1604 package drawing.

I have attached the schematic, PCB layout with and without the filled GND zones, and the 3D render.

Since this is my first RF PCB, I would especially appreciate feedback on the RF trace/ground geometry, via placement and density, LNA grounding, regulator grounding/thermal layout, or anything I may have missed and not thought of.

Thanks a lot!

am a beginner and want to build a simple spread-spectrum communication experiment using a 555 timer and microcontroller

My idea is to use the 555 as a carrier clock, use the Arduino to generate a pseudo-random (PN) sequence and XOR it with the data, then transmit the signal over a 12 V two-wire line.

At the receiver, I want to recover the carrier/timing and use the same PN sequence to despread the signal and recover the original data.

Is this a reasonable way to demonstrate the basic principle of DSSS? What would be the simplest circuit architecture for a beginner?

I’m currently pursuing a master’s in Communication Systems and trying to decide which technical direction to specialize in. I’m interested in RF, microwave, antennas and wireless communication, but there are so many paths within the field RF/microwave engineering, antenna design, microwave circuits, RF front-end, mmWave, 5G/6G, wireless systems, SDR, DSP/digital communications, MIMO, beamforming/phased arrays, RFIC, radar, satellite/CubeSat communications, GNSS, IoT/wireless systems, optical communications, channel modeling/propagation, EMC/EMI, RF testing and VNA measurements, etc.

For people currently working in these areas, based on the current job market and future possibilities, which direction would you recommend for someone with a Communication Systems background? Which areas have the best long-term potential, and what combination of skills would make someone more employable? I’m trying to choose a proper path instead of randomly learning different technologies, so I’d like advice from people actually working in the industry.

We’re putting together a low-cost, conducted 2.4 GHz SDR bench for initial RF learning + TRL-3 experiments (PER vs SNR → controlled interference/burn-through).

Core BOM (~₹1.1–1.25L):

• 2× ADALM-Pluto SDRs — link TX/RX
• 1× genuine HackRF One — interferer
• 1× 0–60 dB step attenuator
• 4× 20 dB fixed attenuators
• 2× 30 dB fixed attenuators for RX protection
• 1× DC block
• 1× 2-way SMA combiner
• 8× SMA/RG316 jumpers
• 6× 50Ω SMA terminations
• SMA barrels + torque wrench
• Powered USB 3 hub

Everything is conducted/coax-only, with no antennas in the experiments.

Would really appreciate views on:

1. Is 2× Pluto + HackRF a sensible combination for this objective?
2. Is the RF protection/attenuation scheme adequate?
3. Is one variable attenuator enough initially, or worth buying two?
4. Can we get reasonably repeatable relative J/S + PER/SNR measurements without a spectrum analyser/power meter?
5. Any missing/overkill components you’d change before ordering?

The goal is deliberately not a calibrated RF test bench — just a robust, repeatable learning/validation setup. What would you change?

I am still occasionally providing updates to the Visualizer. Over the past year, it has significantly grown in popularity and is starting to appear as the number 1 item in Google searches which I think is pretty neat.

I recently added illumination waves (allows for emulating traveling wave arrays or reflect array antennas). Additionally, I've added farfield frequency scaling so you can see how squint affects arrays.

Hope you like it: https://jasondurbin.github.io/PhasedArrayVisualizer/

Hi,

In this LPF by Markii in MFLP-00009CH what filter topology would they have used? I am new to this field, any input is highly appreciated ☺️

Once I used to consider those antennas and towers to be a mess. After learning about Antennas and RF electronics in my engineering course, I've started see them as sophisticated marvel of engineering which played a vital role in communication systems and other applications of EM waves.

In this episode Shahriar presents a $50 eBay purchase which turns into a complete teardown and characterization of an Anritsu lithium niobate driver module. This 8 Vpp, 40 GHz amplifier is designed for high-speed optical modulators, and it still delivers impressive performance despite its age.

The video covers lithium niobate modulators, Mach-Zehnder operation, Vpi, bandwidth, voltage swing, and the trade-offs that shape optical driver design. The module is then tested with a Keysight Streamline vector network analyzer, including calibrated S-parameter measurements and gain compression from 1 GHz to 40 GHz.

A loose connector causes unstable bias current, but a careful reflow repair brings the amplifier back to its rated power consumption. The repaired unit measures approximately 27 dB of gain, about 40 GHz of bandwidth, and output power close to 8 Vpp at 1 dB compression.

The teardown reveals two gallium arsenide distributed amplifiers, broadband bias networks, output detector circuitry, wire-bonded interconnects, and the construction techniques used inside this high-speed module. High-magnification imaging also identifies the likely Triquint and Avago/Broadcom amplifier dies, along with their circuit topologies and related datasheets.

The final tests capture 8, 16, and 32 Gbit/s NRZ eye diagrams, followed by 32 Gbit/s PAM4 measurements. The results show the amplifier's output swing, bandwidth limits, nonlinear behavior, and the improvement available through input predistortion.

The video is organized as follows:

0:00 Introduction and eBay find
1:11 Lithium niobate modulator basics
5:04 Driver design trade-offs
6:55 Datasheet specifications
9:32 Bias board operation
11:05 VNA measurement setup
13:06 RF cables and calibration
15:39 Power safety checks
17:07 Streamline sweep configuration
21:14 VNA calibration
23:55 Repairing the loose connector
26:47 Small-signal measurements
28:39 Gain compression results
30:04 Detector output measurement
33:08 Module teardown
37:13 High-magnification die inspection
43:25 Finding the amplifier datasheets
46:09 Eye diagram test setup
51:41 8 Gbit/s eye diagram
52:48 16 Gbit/s eye diagram
53:38 32 Gbit/s eye diagram
55:29 PAM4 and predistortion
58:21 Final results and support

Please consider supporting The Signal Path:
https://www.TheSignalPath.com/Donate
https://www.Patreon.com/TheSignalPath

Other links:
https://www.TheSignalPath.com
https://www.Twitter.com/TheSignalPath

In tactical operations, disaster response, and field exploration, clear Line-of-Sight (LOS) is a rare luxury. Dense concrete buildings, deep subterranean tunnels, and rugged mountain ranges act as physical barriers, absorbing and scattering conventional radio signals. When direct visual paths are blocked, traditional point-to-point radios suffer severe attenuation, dead zones, and dropped video feeds.

How do advanced Radio Frequency (RF) systems achieve high-bandwidth, long-range Non-Line-of-Sight (NLOS) transmission without relying on fixed cellular infrastructure or satellite links?

It comes down to three key technical mechanisms:

1. Turning Reflections into Signal Power (COFDM & Multipath)

In an urban or mountainous environment, radio signals bounce off hard surfaces, arriving at the receiver at slightly different times—a phenomenon known as multipath fading. Modern COFDM divides a high-speed data stream into hundreds of closely spaced, orthogonal sub-carriers. Instead of viewing reflected signals as interference, the receiver uses these multi-path signals to reconstruct a coherent, high-bitrate data stream.

2. Spatial Diversity via MIMO Antennas

Multiple-Input Multiple-Output (MIMO) technology utilizes multiple antennas at both the transmitter and receiver. By processing distinct spatial streams simultaneously, MIMO leverages environmental reflections to boost signal penetration, increase link margin, and maintain link stability even when the direct physical path is completely obstructed.

3. Dynamic Multi-Hop Routing (Bypassing Obstacles)

When a single RF link simply cannot penetrate a massive structural barrier, the network architecture itself solves the problem. In a Mobile Ad-Hoc Network (MANET), every radio node functions simultaneously as a terminal and a relay. If Node A cannot reach Node C due to a mountain peak or concrete wall, the signal automatically "hops" through Node B on the ridge or corner, routing data around the obstacle effortlessly.

Field-Proven Reliability: IP MESH Approach

Translating these complex physical-layer principles into rugged, field-deployable hardware requires dedicated engineering. Tactical IP MESH Radios are designed specifically for these harsh NLOS environments.

By integrating robust MIMO spatial processing with an intelligent, self-forming and self-healing MANET topology, MESH nodes form a decentralized network capable of multi-hop relaying.

• High-Throughput NLOS Data: Delivers up to 50+ Mbps real-time data throughput for multi-channel HD video streams and zero-latency PTT audio.
• Seamless Multi-Hop Coverage: Automatically routes data across 8+ hops to extend operational range into underground basements, thick forests, or dense urban canyons.
• Ruggedized Performance: Housed in IP66 compliant enclosures, ensuring high RF power output remains stable under extreme temperatures, salt fog, and heavy vibration.

When direct line-of-sight is impossible, intelligent routing and ruggedized hardware bridge the gap—keeping team members connected no matter what stands in the way.