Everything You Need to Know About the SMA Connector

SMA Connector for RF Signals

The SMA connector is an incredible workhorse, offering a wide variety of applications from which it can provide the perfect solution. Because of its versatility, the SMA connector is used in every industry from telecommunications to medical. In today’s spotlight series, we’ll hone in on the venerable SMA RF connector, which provides a critical function in today’s cutting edge medical devices.

What is an SMA connector?

First off, SMA stands for sub-miniature type A. Subminiature connectors are small, hence the name, and are useful in high-frequency applications. This is because SMA connectors are able to provide a steady broadband connection from the KHz range on up to 18 GHz. The inherent reliability of the SMA connector is achieved from a constant impedance of 50 ohms and also because of its low reflection. Electrical impedance is simply a measure used to find the level of opposition that gets applied to a current inside a circuit when the voltage gets applied to it. 50 ohms is considered a good middle ground in the realm of standard characteristic impedance. 

SMA connectors can achieve low reflection and good attenuation because of their shape, which helps to maintain a uniform connection contact. The SMA is coaxial, with the characteristic screw-type coupler; however, these should not be confused with standard coaxial hooking up a home’s cable or internet. To hook up an SMA to a coax requires a special adapter. 

Standard SMA Connector Specs Snapshot:

  • Utilizes a one-quarter inch and 36 thread type coupler
  • Male SMA connectors use a five-sixteenths inch hex nut. This allows the application of torque by a standard one-half inch wrench. The applied torque can be used to easily tighten or loosen the connector.
  • Female SMA connectors utilize a thread for coupling that is 4.32 millimeters long.
  • Employs a special silicon rubber O-ring. This helps to provide separation between the body and the coupler which in turn creates a barrier to outside environmental factors like dust.

Even within a specialized connector like the SMA, there are several different types. Next up, we’ll focus on a Meridian specialty, the SMA RF connector, which provides the crucial connection many different devices in the medical industry rely on to run effectively.

How SMA RF Connectors Help Medical Breakthroughs Happen

RF stands for radio frequency and applies to a range of coaxial electrical connectors. The SMA is one of the most used of the RF-type connectors. Because of the screw-type coupler, the SMA is sturdy mechanically and offers durable performance throughout the life of the system – really important considerations for life-saving medical devices. 

SMA RF connectors come in a male and female variety to provide the crucial connections high frequency medical devices need to consistently send and receive power and data. Male SMA connectors are easily recognizable because they resemble a standard coaxial connection with a center pin inside of its threaded barrel. The female connector acts more like a sleeve which helps provide a good, sturdy connection between the types. Female connectors are usually affixed to a stable device and the male is then used in a removable wire connection for the greatest flexibility within the electrical system.

The sturdiness of construction, extremely reliable performance, and how it fits perfectly into the electrical system is what makes the SMA RF connector the go-to for fields with complex requirements like the medical industry. We produce tens of thousands of SMA RF connectors for medical devices each year. Designing and producing each to exacting standards, we are able to power the devices medical staff rely on to diagnose and treat patients every day. 

Designing the Perfect SMA RF Connector

SMA RF connectors can range from a single connector, customized to provide the perfect connection in an existing system, to a custom cable assembly that provides multiple SMA connections and adapters for providing the greatest range of application. Many SMA RF connectors available today utilize a right angle design but there are also straight angle designs available, all depending on the circuit. Right angle design is a popular choice because it helps maintain the impedance we discussed earlier at a standard level. 

Meridian’s gifted engineering and design team has to calculate the dimensions and structural components of the connection to incredible preciseness. Further, our production team must be absolutely flawless in their assembly, with special attention to the soldering. Too much soldering can lead to what’s known as an impedance mismatch. Impedance mismatch can also occur when the dimensions aren’t exactly right, a mechanical failure, or even when too much air surrounds the contact within the connection. 

Imagine if any of these were to occur during a risky surgery, where hospital staff is dependent upon the many medical devices around them utilizing SMA RF connectors. 

Different Ways to Mount SMA Connectors

  • Panel Mount: this is a female mount made for tough conditions like in the military and industrial settings. With a two-hole or four-hole configuration, panel mounts are easily applied to instrumentation and wireless infrastructure.
  • Bulkhead Mount: female mount with a thread length that is usually longer than the typical 4.3 millimeters to more easily attach to a wall or panel using a nut and washer.
  • Through-Hole Mount: can be vertical or 90 degrees and comes in non-magnetic varieties that are used often in the medical field.
  • Edge Mount: vertical mount that comes in both a standard and drop in variety. 

Losing signal or power mid-procedure isn’t an option which is why our clients have come to know they can depend on Meridian for a quality product that is designed to function as intended cycle-after-cycle.

Does UL-certification matter with SMA RF Connectors?

Creating a product for a device that literally can mean life and death for a patient is a matter no custom cable manufacturer should ever take lightly. We’ve already seen where small deficiencies in the connection can lead to catastrophic failure. This is one of the many reasons we utilize UL-certified components in all of our products, including the SMA RF connector. 

UL-certified components have been tested and verified for their structural integrity, durability, and overall functionality. This allows our design team to utilize components that have known and very specific operating ranges. In this way, we can piece together the perfect amalgamation for even the most complex custom cable assembly

Meridian is proud to utilize UL-certified components and to maintain status as a UL-approved manufacturing facility, having met the stringent quality assurance and quality control (QAQC) requirements of Underwriters Laboratories (UL). We also are proud to have had and continue to maintain our certification as ISO 9001:2015. This difficult to achieve certification requires demonstrable and exceedingly high QA/QC programs that focus not just on quality of the product, but of the entire process – which includes cradle to grave design, sourcing, prototyping, mass assembly, testing, but also emphasizes customer service/satisfaction. 

Making an SMA RF Connector That Performs Flawlessly in its Application

Impedance matching is a crucial step with custom SMA connectors. The design and test teams of Meridian rely on decades of experience in custom cable manufacturing to select the perfect SMA connector to do the job, in the environment, and in conjunction with the other elements of the system – especially terminations. These different components all must work in perfect harmony for the electrical system to perform as it should. 

To produce a one-of-a-kind solution that works perfectly in its intended environment, we are fanatical in our approach to quality. As discussed, quality starts with the very first client contact, through every step of the design and manufacturing process, and then beyond with an industry-leading product warranty. We test each and every product that rolls off our assembly line so that our clients know the product they receive will perform under their exact specifications. 

How do you test SMA RF connectors?

It is indeed rare to go from design straight to volume production without many periods of testing and prototyping in between. Prototyping allows our design team to test several different configurations of the same SMA RF connectors in harsh real world conditions. Often these are even tougher than the actual circumstances the system will face every day. We call this our “advanced life testing lab” which subjects the components to all manner of freezing temps, scorching heat, salt, and other environmental factors that need to be mitigated against during the design phase. 

Aiming for as close to perfection as humanly possible, we also employ highly accurate, automated Cirrus testers. However, there are times such as when the product is entirely unique, that we must design a correspondingly unique and entirely-custom testing unit to ensure the component’s functionality, structural integrity, and above all, safety. 

How to Get a Custom SMA RF Connector Project Started

When you need the perfect solution for a medical device requiring a SMA RF connector, our team is readily available to complete the project on-time and on-budget. Our design managers work with you to understand all of the complexities surrounding your project, set production milestones, lock out the appropriate tools from our massive tool crib, and manage the entire process to ensure the product is made to your absolute satisfaction. Contact us today to go over your specs and outline your options with our dedicated sales team.