History of RF Connectors: From SMA to 5G Antenna Interfaces
Aug 24,2025
Introduction
Most people never think twice about the small metal fittings on their WiFi router, TV set, or even a 5G smartphone. Yet these little parts—RF connectors—quietly decide whether your signal comes through strong or fades into noise. To the untrained eye, they’re nothing more than threaded bits of metal. To engineers, they’re the handshake between systems, where performance is either made or lost.
The history of RF connectors shows just how much technology has demanded from them.
This image reflects how BNC connectors, developed in the 1940s, became vital for television and radar systems, offering quick locking and reliable mid-frequency performance.
- In the 1940s, bulky designs like the BNC and N-Type connector supported broadcast TV and military radar.
- By the 1960s, shrinking electronics led to the SMA connector, still a staple in labs today.
- In the 1990s, WiFi’s rapid growth brought the RP-SMA connector, a regulatory workaround that became standard in routers.
- Now, with 5G connector types, we see both ends of the spectrum: tiny snap-on connectors inside smartphones and rugged weatherproof connectors on outdoor antennas.
Why does this matter? Because choosing the right connector is not just about “fit.” It affects:
- Signal integrity – impedance mismatches can ruin performance.
- Compliance – regulations dictate which connectors can be used.
- Reliability – the wrong choice leads to early failures or costly redesigns.
This guide walks through that evolution step by step. We’ll highlight the trade-offs behind each design, share where they’re still used today, and explain why something so small remains essential in every wireless system.
Early RF Connectors: BNC and N-Type
The BNC Connector — Fast and Handy
The image highlights the BNC connector’s signature bayonet lock, which allows quick connect and disconnect while maintaining signal stability, a reason for its popularity in test and CCTV systems.
When the BNC connector appeared in the 1940s, engineers finally had a quick way to attach and detach test leads without fumbling with wrenches. Its bayonet-style coupling was almost revolutionary at the time—push in, twist a quarter turn, and you were ready to measure. This convenience made it a favorite in research labs, broadcast studios, and later in CCTV security systems.
But there was a trade-off. While BNC was easy to handle, its frequency performance was limited. Most designs worked reliably up to about 4 GHz. Early versions also struggled with consistent impedance; some were 50 Ω, others 75 Ω, which could cause mismatches in sensitive circuits. Still, for many mid-frequency jobs, the BNC connector was good enough, and it remains common today in test equipment and video systems.
The N-Type Connector — Bigger, Stronger, More Precise
The image shows N-Type connectors as mainstays in radar, outdoor base stations, and military RF systems, handling frequencies up to 18 GHz
Around the same era, the N-type connector took a different path. Designed by Paul Neill (the same engineer whose name appears in BNC), the N-Type was made for higher-power microwave systems. Its threaded coupling ensured a secure fit, and its larger body provided better shielding and higher voltage tolerance than BNC.
Modern precision versions of the N-type connector handle frequencies up to 18 GHz and are available in both 50 Ω and 75 Ω versions. They’re a mainstay in outdoor base stations, radar systems, and satellite communication, where durability and weather resistance are essential. If you spot a chunky connector on a rooftop 5G antenna or a military-grade RF unit, chances are it’s an N-Type.
Comparison: BNC vs N-Type
| Feature | BNC Connector | N-Type Connector |
|---|---|---|
| Introduced | 1940s | 1940s–1950s |
| Coupling Method | Bayonet twist | Threaded |
| Frequency Range | Up to ~4 GHz | Up to 18 GHz (modern) |
| Impedance | 50 Ω or 75 Ω | 50 Ω / 75 Ω versions |
| Power Handling | Low–moderate | High |
| Typical Uses | Test equipment, CCTV, broadcast | Radar, base stations, satellite links |
| Strengths | Quick connect/disconnect, compact | Rugged, high power, weatherproof |
| Limitations | Limited frequency & power handling | Larger size, less convenient |
The Miniaturization Era: SMA Connectors
By the 1960s, electronics weren’t getting bigger—they were getting smaller. Radios, satellites, even the first computers were shrinking in size, and suddenly those bulky BNC and N-Type connectors felt like overkill. Reliable, yes. Space-friendly? Not at all. Engineers wanted something that could slip into compact modules without sacrificing signal quality.
The image shows SMA connectors as a game changer since the 1960s, combining compact size with high-frequency performance up to 18 GHz.
That’s when the SMA connector (SubMiniature version A) showed up. First introduced in the late ’60s, it quickly found a home in labs during the 1970s. What made it stand out? Its threaded coupling gave solid mechanical stability, and its 50-ohm design offered excellent impedance control. More importantly, it could operate up to 18 GHz—far beyond what most connectors of its day could handle.
Why SMA Was a Game Changer
- Compact footprint: At roughly a quarter inch, it fit neatly onto crowded PCBs.
- Microwave performance: Supported frequencies high enough for early radar and satellite testing.
- Consistency: Tight impedance control meant fewer headaches with mismatched systems.
- Flexibility: Worked with semi-rigid as well as flexible coaxial cables.
Where You’ll See SMA in Action
- Spectrum analyzers & VNAs: Every engineer who’s twisted one of these knows the satisfying “bite” when it locks.
- RF modules: Still the go-to choice for IoT boards and wireless transceivers.
- Defense & aerospace: Rugged enough for radar systems where failure isn’t an option.
Even today, half a century later, the SMA connector remains a workhorse. It’s the balance of size, cost, and high-frequency capability that keeps it relevant across labs and industry.
Consumer WiFi and IoT: The Rise of RP-SMA
Jump ahead to the mid-1990s, and WiFi is suddenly everywhere—homes, campuses, offices. Regulators had one big concern: people boosting range with oversized antennas and blasting signals where they shouldn’t. The workaround? Change the connector so standard antennas wouldn’t fit.
Enter the Reverse Polarity SMA (RP-SMA). At a glance, it looks just like a regular SMA. Same threading, same dimensions. The catch lies in the center pin:
- RP-SMA Male → threads on the outside, but instead of a pin, there’s a socket.
- RP-SMA Female → threads on the inside, but instead of a socket, there’s a pin.
That tiny swap was enough to make standard SMA antennas incompatible. Manufacturers could ship WiFi gear knowing users wouldn’t easily upgrade to high-gain antennas.
Why RP-SMA Took Over
- Compliance: Helped router makers meet FCC rules in the U.S.
- Economics: Reused the SMA body style, keeping costs down.
- Momentum: Once big vendors adopted it, the whole ecosystem followed.
- IoT adoption: As smart hubs and gateways popped up, RP-SMA came along for the ride.
Everyday Encounters
The image highlights RP-SMA as the regulatory standard for WiFi equipment, preventing easy antenna upgrades while ensuring compliance.
Flip a WiFi router around—you’ll almost always see RP-SMA female jacks on the back. The antennas themselves? RP-SMA male plugs. You’ll find the same setup on Zigbee hubs, Bluetooth dongles, even some USB WiFi sticks.
Watch Out For…
- Mix-ups: People buy SMA antennas thinking they’ll fit RP-SMA routers. They don’t.
- Wear and tear: The smaller design isn’t built for constant swapping. In lab setups, N-Type or SMA is still the sturdier choice.
Quick Comparison
| Feature | SMA | RP-SMA |
|---|---|---|
| First Introduced | 1960s-70s | 1990s (Wi-Fi boom) |
| Threading | ¼"-36 (standard) | ¼"-36 (same) |
| Center Contact | Male = Pin, Female = Socket | Male = Socket, Female = Pin |
| Frequency Range | Up to 18 GHz | Up to ~6 GHz (Wi-Fi/IoT focus) |
| Common Uses | Test gear, aerospace, IoT RF | Routers, gateways, consumer IoT |
| Strengths | Precision, high-frequency use | Prevents antenna swapping, cheap |
| Weaknesses | Not for casual Wi-Fi products | Limited durability, not universal |
High-Frequency and Precision: 2.92 mm, 2.4 mm, 1.85 mm Connectors
The side-by-side comparison shows SMA connectors rated to 18 GHz, 2.92 mm (K) up to 40 GHz, 2.4 mm up to 50 GHz, and 1.85 mm (V) supporting 67–70 GHz, underscoring their roles in high-frequency applications.
As wireless technology marched into the mmWave era, the trusty SMA connector finally hit its ceiling. Standard SMA designs maxed out around 18 GHz, which worked for most traditional RF systems but fell short for the new frontier—satellite links, automotive radar, and 5G testing, all demanding 40 GHz and beyond. Engineers needed something smaller, stronger, and more precise.
The 2.92 mm Connector (K Connector)
Developed in the 1980s, the 2.92 mm connector, also known as the K connector, extended usable frequency to 40 GHz. Unlike SMA, it was engineered with tighter tolerances to prevent mode conversion and signal reflections at higher frequencies. Because it retained SMA’s ¼”-36 threading, it offered partial mechanical compatibility, which eased adoption in labs.
The 2.4 mm Connector
Pushing performance even further, the 2.4 mm connector supported signals up to 50 GHz. Its slightly smaller geometry improved mode-free operation, meaning signals could propagate cleanly at extreme frequencies. While not backward compatible with SMA, it became the standard for high-end test equipment where every dB of loss mattered.
The 1.85 mm Connector (V Connector)
For truly cutting-edge applications, the 1.85 mm connector, often called the V connector, stepped in. With frequency support up to 65 GHz, it unlocked research into 5G FR2 bands, advanced radar systems, and mmWave imaging. Its extremely fine tolerances made it costly, but in fields like aerospace or defense, performance outweighs price.
Why These Matter
If SMA represented the miniaturization era, these precision connectors marked the dawn of ultra-high-frequency RF engineering. They enabled accurate testing of 5G hardware, supported new communication satellites, and powered research into terahertz technologies. Without them, much of today’s mmWave development simply wouldn’t be possible.
High-Frequency Connector Comparison
| Feature | SMA Connector | 2.92 mm (K) | 2.4 mm | 1.85 mm (V) |
|---|---|---|---|---|
| Introduced | 1960s-70s | 1980s | 1986 | 1980s-90s |
| Max Frequency | ~18 GHz | 40 GHz | 50 GHz | 65 GHz |
| Thread Style | ¼"-36 | ¼"-36 (partial SMA compatibility) | Custom | Custom |
| Impedance | 50 Ω | 50 Ω | 50 Ω | 50 Ω |
| Applications | General RF labs, wireless modules | 5G test, satellite comms | High-end analyzers, mmWave, defense | Advanced radar, precision test |
| Strengths | Compact, affordable | High frequency, semi-compatible | Extreme accuracy, high-end range | Highest frequency range |
| Limitations | Stops at ~18 GHz | Costly vs SMA | Not backward compatible | Expensive, delicate |
5G Era and Beyond: New Antenna Interfaces
When 5G networks began rolling out in the late 2010s, they brought two distinct frequency ranges. The first, FR1 (sub-6 GHz), reused much of the hardware legacy from 4G LTE. The second, FR2 (mmWave, 24–40 GHz and beyond), introduced an entirely new challenge: building antennas and connectors small enough to fit inside phones and IoT modules, yet precise enough to handle extremely high frequencies.
Compact Internal Connectors: U.FL, MHF, and IPEX
The image illustrates how U.FL/IPEX connectors provide space-saving solutions on PCBs, enabling antenna connections in smartphones, IoT devices, and compact RF modules.
Inside smartphones, routers, and IoT gateways, space is at a premium. That’s why manufacturers turned to U.FL, MHF, and IPEX connectors—tiny snap-on RF connectors that measure just a few millimeters across. They can’t handle much power or repeated mating cycles, but they’re perfect for short internal antenna links where size matters more than durability. If you’ve ever opened a WiFi card or 5G modem, those tiny snap connectors bridging the PCB and antenna are almost certainly U.FL or IPEX.
Outdoor Durability: N-Type Weatherproof
While handheld devices moved toward miniature solutions, outdoor 5G infrastructure demanded the opposite: ruggedness. N-Type connectors, long trusted in radar and base stations, found new life in weatherproof variants. With gaskets and sealed housings, they ensured that outdoor 5G base stations could survive rain, dust, and temperature extremes while still delivering clean signals.
Still Relevant: SMA and RP-SMA in IoT
Interestingly, not all 5G devices use futuristic connectors. Many IoT gateways, routers, and industrial modules still rely on SMA or RP-SMA connectors for sub-6 GHz bands. Why? Because they’re inexpensive, familiar, and good enough for frequencies below 6 GHz. Walk into a smart factory or data center today, and you’ll likely spot plenty of RP-SMA antenna ports on IoT hubs.
Toward Massive MIMO and 6G
The real trend in 5G connectors isn’t just frequency—it’s density. With Massive MIMO (multiple-input, multiple-output) arrays packing dozens or hundreds of antenna elements, engineers are developing ever-smaller, board-to-board interconnects. Looking ahead to 6G, expect connector technology to keep shrinking, while balancing the eternal trade-offs between size, durability, and frequency performance.
Common 5G Connector Types
| Connector Type | Size / Form Factor | Frequency Range | Typical Application | Strengths | Limitations |
|---|---|---|---|---|---|
| U.FL / IPEX / MHF | Ultra-small snap-on | Up to ~6 GHz (some to 15 GHz) | Smartphones, IoT modules, Wi-Fi cards | Tiny, cheap, easy for PCB integration | Fragile, low mating cycles |
| N-Type | Large threaded, weatherproof sealed | Up to 18 GHz | Outdoor 5G base stations, antennas | Rugged, waterproof, high-power handling | Bulky, not suited for handhelds |
| SMA / RP-SMA | Small threaded | Up to 18 GHz | IoT hubs, routers, sub-6 GHz devices | Affordable, widely available | Not ideal for mmWave bands |
| 2.92 mm / 2.4 mm / 1.85 mm | Precision connectors | 40–65 GHz | 5G FR2 test, satellite comms | Extreme accuracy, lab-grade | Expensive, delicate |
Timeline of RF Connector Evolution
Looking at the history of RF connectors, it’s clear that every new design emerged as a direct response to changing technology. Early connectors like BNC and N-Type solved broadcast and military needs in the 1940s. The SMA connector arrived in the 1960s as electronics shrank, followed by RP-SMA in the 1990s to meet WiFi regulations. Then, as engineers pushed into mmWave frequencies in the 2000s and beyond, precision connectors like 2.92 mm, 2.4 mm, and 1.85 mm became essential. Finally, the rollout of 5G in the 2020s brought both miniature snap-on interfaces for mobile devices and ruggedized connectors for outdoor base stations.
This timeline isn’t just history—it’s a roadmap showing how performance requirements, regulation, and cost shaped the evolution of SMA and other connectors. It also hints at where things may go as 6G and satellite internet push demands even higher.
RF Connector Evolution Timeline
| Era/Decade | Connector Types | Key Features | Typical Applications |
|---|---|---|---|
| 1940s | BNC, N-Type | Quick bayonet coupling (BNC); threaded, high-power rugged design (N-Type) | Broadcast TV, test labs, radar systems |
| 1960s-70s | SMA Connector | Compact, threaded, up to 18 GHz, precise 50 Ω impedance | Spectrum analyzers, RF modules, aerospace |
| 1980s | 2.92 mm (K Connector) | Extended frequency to 40 GHz, partial SMA compatibility | Microwave test systems, satellite links |
| 1986 | 2.4 mm Connector | Mode-free operation up to 50 GHz | High-end VNAs, precision analyzers |
| 1990s | RP-SMA Connector | Reverse polarity for WiFi compliance | WiFi routers, IoT gateways, wireless cards |
| 1990s-2000s | 1.85 mm (V Connector) | Up to 65 GHz, ultra-precision | 5G prototype testing, radar, mmWave imaging |
| 2010s | Advanced SMA variants | Improved durability, extended frequency | RF test equipment, IoT development |
| 2020s | 5G-specific interfaces (U.FL, IPEX, MHF, Weatherproof N-Type) | Ultra-miniature connectors for devices; rugged connectors for outdoor 5G | Smartphones, 5G base stations, IoT modules |
Timeline of RF Connector Evolution
When you line up the last 80 years of RF connectors, a clear pattern emerges: every new design was born because the old one hit a wall. The 1940s gave us BNC for labs and N-Type for radar. The 1960s brought the SMA connector as electronics shrank. By the 1990s, RP-SMA took over WiFi gear, while labs chasing higher frequencies moved on to 2.92 mm and 2.4 mm connectors. Fast-forward to the 2020s, and we now juggle two extremes—tiny snap-on connectors for smartphones, and heavy-duty weatherproof types for outdoor 5G towers.
In other words: the connector story isn’t random. It’s a roadmap showing how performance demands, regulation, and cost shaped the evolution of SMA and beyond. And it hints at what’s next as 6G and satellite internet push even harder.
RF Connector Timeline (Snapshot)
| Decade | New Arrivals | Why They Mattered | Where They Showed Up |
|---|---|---|---|
| 1940s | BNC, N-Type | BNC made lab work faster; N-Type handled radar & power | Broadcast TV, test benches, radar sites |
| 1960s-70s | SMA | Compact, 50 Ω, hit 18 GHz | Spectrum analyzers, satellites |
| 1980s | 2.92 mm (K) | Took signals to 40 GHz | Microwave test systems |
| 1986 | 2.4 mm | Mode-free up to 50 GHz | High-end VNAs |
| 1990s | RP-SMA | Regulatory twist for Wi-Fi | Routers, IoT gateways |
| 1990s-2000s | 1.85 mm (V) | Reached 65 GHz | Radar, mmWave imaging |
| 2010s | Advanced SMA | Ruggedized, extended use | RF test gear |
| 2020s | U.FL, IPEX, Weatherproof N-Type | Ultra-miniature for phones; rugged for towers | 5G phones, base stations |
Practical Takeaways for Engineers and Buyers
Studying history is fun, but here’s the real question: what do you do when you actually need to choose a connector? I’ve seen teams burn weeks because someone ordered the wrong RP-SMA antennas, or spec’d BNCs for a 10 GHz system (instant disaster). So here’s a no-nonsense guide.
Things That Matter Most
- Frequency: Below 6 GHz? Stick with SMA or RP-SMA. For 28–40 GHz mmWave? Think 2.92 mm or 2.4 mm. Beyond 50 GHz, only 1.85 mm will survive.
- Power: Outdoor systems? N-Type wins every time. Tiny U.FLs are great for smartphones but don’t try running high power through them.
- Environment: If it’s outdoors, go weatherproof. I’ve seen standard SMAs corrode in a single winter.
- Use Case:
- Lab → SMA, 2.92 mm, 2.4 mm
- WiFi & IoT → RP-SMA
- 5G base stations → N-Type or precision mmWave
Mistakes I See All the Time
- SMA vs RP-SMA mix-ups: They look the same, but the pins don’t match.
- Forgetting weatherproofing: A connector might work fine on your desk, but stick it on a tower and it dies in months.
- Overkill or underkill: Buying a 65 GHz connector for a 2.4 GHz system is just burning money.
- Ignoring wear limits: U.FLs last maybe 30 insertions. Fine for assembly lines, terrible for field swapping.
Connector Selection Guide
| Application Scenario | Recommended Connector(s) | Why It Works | Pitfalls to Avoid |
|---|---|---|---|
| Lab testing up to 18 GHz | SMA | Compact, affordable, widely available | Don’t push beyond 18 GHz |
| Wi-Fi routers / IoT hubs | RP-SMA | Meets regulatory requirements, easy antenna swaps | Don’t confuse with standard SMA |
| Outdoor base stations | Weatherproof N-Type | Rugged, handles high power, weather-resistant | Bulky size may not fit compact devices |
| mmWave testing (28–40 GHz) | 2.92 mm (K Connector) | High precision, partial SMA compatibility | More expensive than SMA |
| High-end analyzers (up to 50 GHz) | 2.4 mm | Mode-free operation at very high frequency | Not backward-compatible |
| Cutting-edge radar / 65 GHz research | 1.85 mm (V Connector) | Supports extreme frequencies | Very expensive, fragile |
| Smartphones, Wi-Fi cards, IoT modules | U.FL / IPEX | Tiny, easy PCB integration | Fragile, very limited mating cycles |
In short: don’t treat connectors as an afterthought. The right RF connector balances frequency, power, durability, and cost. The wrong one risks poor signal integrity, failed compliance tests, or unnecessary expense.
Conclusion
The journey of the RF connector isn’t just about bits of metal and threads. It mirrors the story of wireless communication itself. From the chunky BNC and N-Type connectors that kept 1940s broadcast gear running, to the SMA connector of the 1960s that made high-frequency testing practical, to the quirky RP-SMA of the WiFi boom—every stage solved a problem that engineers were wrestling with at the time.
Once the industry started pushing into mmWave bands, we suddenly needed ultra-precise connectors like the 2.92 mm, 2.4 mm, and 1.85 mm (V connector). And in today’s 5G era, we live with two extremes: feather-light U.FL and IPEX connectors hiding inside smartphones, and heavy-duty weatherproof N-Type connectors bolted onto base stations.
So where does it all go from here? My bet: smaller, faster, and tougher. With 6G, satellite internet, and massive IoT deployments on the horizon, connectors will keep shrinking while handling ever higher frequencies. What won’t change is their role. A connector is never “just a connector.” It’s the handshake between systems—the place where your project either holds up or falls apart.
If you’re an engineer, buyer, or even just a curious techie, knowing the history of RF connectors isn’t trivia. It’s practical knowledge that saves money, prevents downtime, and keeps your signal clean.
Want to dig deeper? Check out our RF Connector Selection Guide for hands-on advice about picking the right connector for your next build.
Bonfon Office Building, Longgang District, Shenzhen City, Guangdong Province, China
A China-based OEM/ODM RF communications supplier
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