RF switches are prevalent in many RF systems for a variety of uses. Switches are commonly used to switch between a receive or transmit channel at the port of an antenna, switch between filter channels, or used in matrices to switch test channels for high throughput automated testing or to extend the port count of a vector network analyzer.
We offer several popular types of RF switches including Electromechanical Relay Switches that have a minimum frequency of DC and a maximum frequency range between 4 GHz and 18 GHz, PIN Diode Switches that feature a single pole single throw (SPST) design with a maximum insertion loss between 1.2 dB and 3.5 dB, and Manual Switches that employ a make before break configuration with manual toggle actuators.
RF switches may be integrated in RF semiconductor devices as solid-state switches, discrete solid-state, or micro electrical mechanical machine (MEMS) switches may be relatively large connectorized components that rely on embedded motors to engage the switch mechanisms for different paths. RF switches may have one to many paths they may switch between and may also switch from multiple inputs to a series of outputs simultaneously. Configuring several switches to allow for any input path to switch to any of the output paths of the switch enables the creation of a multiplexer or demultiplexer. If only one input can be switched to a given output at a time, this is known as a blocking matrix switch.
Hence, the complexity of RF switches may be very high, and may have a large number of input and output ports. For example, there are commercially available switch matrices with over 128 ports, which are used in antenna array testing. Testing simple RF switches can be as simple as connecting the switch to a VNA and gathering the transmission and reflection parameters from both ports at either of the switch states. With more complex switches, each port needs to be tested in each of the switch states. There are also some applications where understanding the dynamics of the switch during an on-to-off and off-to-on switching action are also important to prevent various peak load situations that may cause undesirable peak power levels seen at the device or along the signal path.
Therefore, beyond multiport VNA testing of a switch, which may be done with a VNA with a switch matrix accessory, signal generators and spectrum analyzers/power meters may also be used to test dynamic switch performance in some cases. The critical performance parameters commonly specified for RF switches are as follows:
- Impedance (on and off state)
- Bandwidth
- Insertion Loss
- Return loss (also over temperature, known as IL temperature coefficient)
- VSWR
- Isolation
- Crosstalk
- Switching speed or switching time (rise time and fall time)
- Power handling or RF input power (continuous wave or peak)
- DC Power dissipation
- Positive operating voltage and biasing (solid state switches)
- Hot switching capability
- Switch actuation power/voltage/current or signal (may be analog or digital)
- Reflective or termination
- Input third order intercept (solid state)
- Third order intermodulation (electromechanical)
- 1 dB compression point or 0.1 dB compression point
- Minimum operating life in number of cycles
- Temperature range of operation
As some RF switches are used in mission critical applications, rigorously testing the switch’s reliability and performance in extreme environments is also essential. In these cases, accelerated stress testing is often performed to determine a minimum operational lifespan based on a number of switching cycles. Also, some RF switches may need to be switched while signal power is applied, known as hot switching, which may result in different power handling capability than the switch in a static on or off position. For switches with multiple RF paths, isolation testing using a multiport VNA is crucial as some switch technologies may allow for some signal power to leak from one path to another.
Learn more about Fairview Microwave’s RF Switches.