RF switches are not that easy to understand. Buying them is difficult because you have to look at operating parameters. This is what makes the choice a proper one. RF switches should only be bought after you take a look at the really important factors, the ones that we will highlight below. Before you go on the internet and buy RF switches, consider the following parameters:
Frequency Range
RF applications, just as microwave applications, can range in frequencies from 100 MHz (used as semiconductors) to 60 GHz (used for satellite communications). A broadband accessory will increase test system flexibility because it extends the frequency coverage. Even so, the frequency used is clearly applicant dependent and the broader operating frequency will always be sacrificed in order to meet critical parameters of more importance for the user.
Return Loss
This can appear because of an impedance mismatch that appears between the circuits. When faced with microwave frequency, material properties and network element dimensions will play a really important role in figuring out impedance mismatch and match. The RF switches that have good return loss performance will guarantee a proper power transfer throughout the network.
Insertion Loss
This can be considered as being critical for testing purposes. The losses that are higher than 2 dB will always attenuate peak signals and will increase failing and rising edge times. When low insertion loss is noticed, this is possible because connector numbers are minimized and the use of through-paths is also minimized.
Isolation
We can define isolation as being attenuation degree from unwanted signal that is detected at interest port. It is important when a frequency is high. If you have high isolation, signal influence from another channel is reduced. This would sustain measured signal integrity and will reduce the measurement uncertainties in the system.
Switch Speed
This is defined as being the time that is necessary in order to modify switch arm (port) state from OFF to ON or vice-versa. It is obvious why it is needed.
Settling Time
The settling time of the RF switch will be highlighted in the switch performance as there is a higher need for precision and accuracy. You measure this time at a level that is really close to a final value. In most cases the value is 0.01 dB to 0.05 dB.
Power Handling
This will define the ability of an RF switch to properly handle power and will usually be highly dependent on materials and designs used. You have various power handling ratings like cold switching, hot switching, peak power and average power.
Termination
In many different applications a load termination of 50 ohm is critical as every single transmission that is unused will be able to resonate. Such a fact is highly important when you design a system that works with high frequencies because switch isolation will drop. If the switch is connected to a device that is active, the power of the unterminated path that is reflected has the potential of damaging the source.
