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what is a sma pcb mount rf connector?

dl09

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i read about something called a sma connector pcb mount rf connector. i can't find much information on the internet about it. you connect sma connector pcb mount rf connector to a printed circuit board?
 

KlausST

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Hi,
..I can't find much information....

I don't agree. An internet search for "SMA connector" gives a huge ammount of informations:
* pictures, photos, videos, drawings, dimensions, technical informations, datasheets, specifications......
Even wikipeda has a page for it.

Klaus
 

dl09

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i know it's a radio frequency coaxial connector. but how do i connect sma connector to a printed circuit board?
 

KlausST

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Hi,

I don't know what you are asking for....

Maybe this: By soldering.
(The usual way to connect a part to a PCB...)

Klaus
 

dl09

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i see websites selling sma pcb-mounted connectors on the internet. at the base there are 5 pins.
there is a pin in the middle. there is 1 pin in the upper left corner. there is another pin in the upper
right corner. there is another pin in the bottom right corner. there is another pin in the bottom left corner.
what does the middle pin do? does the middle pin carry a signal?
 

KlausST

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Hi,

All electronic devices, every voltage measurement, every current measurement any electronics interface needs
* a signal
* and it's return path

So the connector connects the PCB with a coax cable
Both paths
* the inner signal
* the outer shield
Are equally important. One can not work without the other.

The antanna itself may be a rod antenna. And a rod antenna is one of a very few electric devices that can work with a single signal (Mind: not the cable, just the antenna rod). But even the antenna rod needs to be designed in length to match your systems "characteristic impedance".
An in one system (maybe an RF transmitter) all parts that carry the RF signal need to be designed for equal characteristic impedance to work optimally.
* the amplifier
* the filters
* the traces on the PCB
* the connector
* the cable
* the antenna
If your system is a 50 Ohms system, then every single of these parts need to be designed for 50 Ohms impedance.

But as others mentioned before: You need to learn the basics. Start with simple things, learn the formulas, learn the physics, learn the mathematics, do courses. If you don't learn the basics you will not get satisfactory results..and you will not get success and thus not enough motivation to keep on.

From your previous posts I see that you don't know the difference between voltage and current and how to measure it. You don't know how to read and to draw a simple schematic.

It seems your ideas come from reading unreliable internet sources. In best case incomplete without detailed descriptions... in worst case simply wrong.
They confuse you more that they give you progress.
Go for reliable informations from universities, schools, semiconductor manufacturers, reliable big companies.

Mind: A forum can't replace school or learning. To be honest ... in your current situation, without knowing the basics, I doubt that the forum is much of help to make your ideas become real working circuits.

Klaus
 

ZoroZeng

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Hi,

Maybe you can try to use below way:

0.png

The process of transferring high-frequency energy from a coaxial connector to a printed circuit board (PCB) is often referred to as signal injection, and its characteristics are difficult to describe. The efficiency of energy transfer varies greatly depending on the circuit structure. Factors such as PCB material and its thickness and operating frequency range, as well as connector design and its interaction with circuit materials can affect performance. Through the understanding of different signal injection settings and the review of some optimization examples of RF microwave signal injection methods, performance can be improved.

Achieving effective signal injection is related to design, and general broadband optimization is more challenging than narrowband. Generally, high-frequency injection becomes more difficult as the frequency increases, and at the same time, as the thickness of the circuit material increases, the complexity of the circuit structure increases and there are more problems.

*Signal injection design and optimization

The signal injection from the coaxial cable and connector to the microstrip PCB is shown in Figure 1. The electromagnetic (EM) field distribution through the coaxial cable and connector is cylindrical, while the EM field distribution in the PCB is flat or rectangular. From one propagation medium to another medium, the field distribution will change to adapt to the new environment, resulting in anomalies. The change depends on the type of medium; for example, whether the signal injection is from coaxial cables and connectors to microstrip, grounded coplanar waveguide (GCPW), or stripline. The type of coaxial cable connector also plays an important role.


1.png
Figure 1. Signal injection from coaxial cables and connectors to microstrip.

Optimization involves several variables. It is useful to understand the EM field distribution within the coaxial cable/connector, but the ground loop must also be considered as part of the propagation medium. It is usually helpful to achieve a smooth impedance transition from one propagation medium to another. Understanding the capacitive and inductive reactances at the point of impedance discontinuity allows us to understand the circuit performance. If three-dimensional (3D) EM simulation is possible, the current density distribution can be observed. In addition, it is best to consider the actual situation related to radiation loss.
2.png

Although the ground loop between the signal launch connector and the PCB may not appear to be a problem, the ground loop from the connector to the PCB is very continuous, but this is not always the case. There is usually a small surface resistance between the metal of the connector and the PCB. There is also a small difference in the electrical conductivity of the welding shop connecting different parts and the metal of these parts. At low RF and microwave frequencies, the impact of these small differences is usually small, but at higher frequencies the performance impact is significant. The actual length of the ground return path affects the transmission quality that can be achieved with a given connector and PCB combination.

As shown in Figure 2a, when electromagnetic wave energy is transferred from the connector pins to the signal wires of the microstrip PCB, the ground loop back to the connector housing may be too long for a thick microstrip transmission line. The use of PCB materials with higher dielectric constants will increase the electrical length of the ground loop, thereby exacerbating the problem. Path lengthening will cause problems with frequency dependence, which in turn will produce local phase speed and capacitance differences. Both are related to the impedance in the transformation zone and will affect it, resulting in a difference in return loss. Ideally, the length of the ground loop should be minimized so that there is no impedance anomaly in the signal injection area. Please note that the ground point of the connector shown in Figure 2a only exists at the bottom of the circuit, and this is the worst case. Many RF connectors have the ground pin on the same layer as the signal. In this case, the ground pad is also designed on the PCB.

Figure 2b shows a grounded coplanar waveguide to microstrip signal injection circuit. Here, the main body of the circuit is a microstrip, but the signal injection area is a grounded coplanar waveguide (GCPW). Coplanar emission microstrips are useful because they can minimize ground loops and have other useful characteristics. If you use a connector with ground pins on both sides of the signal wire, the ground pin spacing has a significant impact on performance. It has been shown that this distance affects the frequency response.

3.png
Figure 2. A thick microstrip transmission line circuit and a longer ground return path to the connector (a) a signal injection circuit for a grounded coplanar waveguide to microstrip (b).

In the experiment using the coplanar waveguide to microstrip microstrip based on Rogers' 10mil thick RO4350B laminate, a connector with a different ground spacing for the coplanar waveguide port was used, but other parts were similar (see Figure 3). The ground interval of connector A is about 0.030', and the ground interval of connector B is 0.064'. In both cases, the connector is launched on the same circuit.


4.png
Figure 3. Coaxial waveguide-to-microstrip circuit testing using coaxial connectors with similar ports with different ground spacing.

The x-axis represents the frequency, 5 GHz per division. When the microwave frequency is low (< 5="" ghz), the performance is equivalent, but when the frequency is higher than 15="" ghz="", the performance of the circuit with a large ground interval becomes worse. The connector is similar, although these 2="" models have slightly different pin diameters, the connector b="" has a larger pin diameter and is designed for thicker pcb="">

A simple and effective method for optimizing signal injection is to minimize the impedance mismatch in the signal emission area. The rise in the impedance curve is basically due to an increase in inductance, while the fall in the impedance curve is due to an increase in capacitance. For the thick microstrip transmission line shown in Figure 2a (assuming that the dielectric constant of the PCB material is low, about 3.6), the wire is wider-much wider than the inner conductor of the connector. Due to the large difference in the size of the circuit wire and the connector wire, a strong capacitive mutation will occur during the transition. It is usually possible to reduce capacitive abrupt changes by tapering the circuit wire so as to reduce the size gap formed where it connects to the pins of the coaxial connector. Narrowing the PCB lead will increase its inductance (or decrease the capacitance, thereby canceling the capacitive abrupt change in the impedance curve).

The effect on different frequencies must be considered. Longer gradient lines will produce stronger sensibility for low frequencies. For example, if the return loss at low frequencies is poor and there is a capacitive impedance spike, a longer gradient line is more appropriate. Conversely, the effect of shorter gradient lines on high frequencies is greater.

For coplanar structures, capacitance increases when adjacent ground planes are close. Generally, the inductive capacitance of the signal injection area is adjusted in the corresponding frequency band by adjusting the distance between the gradual signal line and the adjacent ground plane. In some cases, the adjacent ground pads of the coplanar waveguide are wider on a section of the gradient line to adjust the lower frequency band. Then, the pitch is narrowed in the wider part of the gradient line, and the length of the narrowed part is not long, so as to affect the higher frequency band. In general, narrowing the wire gradient will increase the sensitivity. The length of the gradient line affects the frequency response. Changing the adjacent ground pad of the coplanar waveguide can change the capacitance, and the reason why the pad spacing can change the frequency response plays a major role in the change of the capacitance.

Hope these can help you. (Advertising deleted)
 
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    Kajunbee

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