Consider the following parameters to select the most suitable switch for a specific application.
1. RF Circuit – The three most common circuit configurations are (1) single-pole-double-throw (SPDT), (2) Transfer (DPDT), and (3) multiposition.
Select the simplest circuit to meet system requirements.
2. Actuator – The Pulse Latching Actuator is recommended. Actuation requires a pulse length equal to or greater than the switching time. This type of switch requires current only during switching and for a very short period of time. A pulse width of 30 milleseconds minimum will more than satisfy current requirements. There is also no need to supply DC power to hold the selected position. However, pulse latching can be operated with continuous DC power supplied to the unit with no degradation or decrease in life expectancy.
A latching switch with internally cut off current circuitry can be obtained from CEI in some models if your system is not equipped with pulse command circuitry. This option will disconnect the drive circuit so that DC current will not be consumed after switching has been accomplished.
The Fail-Safe Actuator is used where system requirements dictate the switch return to the normally closed or fail-safe position when actuator power is removed. Most Charter Engineering fail-safe switches utlize magnetics rather than springs for fail-safe holding power.
The Mometary or normally open Actuator is used where system requirements require all output ports of the switch to be disconnected from the input port until a voltage is applied to a selected position.
3. Frequency – Specify the actual frequency to be used as minimum bandwidth. This often results in reduced testing time and associated costs.
Generally, electromechanical switches are capable of higher-frequencies and greater bandwidths than necessary for the intended usage.
The following table correlates frequency and connector type:
| Frequency 40.0 GHz 26.5 GHz 21.0 GHz 18.0 GHz 16.5 GHz 14.0 GHz 12.4 GHz 12.4 GHz 6.5 GHz |
Connector 2.92 mm SMA SMA SMA TNC N N TNC SC |
Note Standard Standard Standard Standard Special Order Special Order Standard Standard Standard |
RF Connectors – Type SMA is the recommended connector expect for high power requirements. The normal frequency limit is 26.5 GHz; however, Charter Engineering can supply switches which function up to 40.0 GHz.
The Type N connector is recommended
for optimum RF performance and operation at
power levels greater than the SMA power rating.
See CW Power Capability vs. Frequency Chart.
The type TNC connector is recommended where power levels and frequency are high and the package is small.
The Type SC connector is recommended for high power applications in which large diameter cables are used for extremely low loss. SC is normally used up to 1000 MHz, but Charter Engineering has modified the design to operate up to 6.5 GHz and in special cases up to 10.0 GHz.
Type BNC connectors can also be supplied upon request.