RF and Microwave Terminations or RF loads are the RF passive component used to absorb incident power at an RF port with a minimal signal reflection back into the RF system circuit. This reduction in refection is achieved by terminating the RF port by using suitable power handling RF terminators at their characteristic impedance.
There are many RF and microwave component manufacturers that offer coaxial, SMD, and wave-guide termination with lower to very high RF power handling for a wide range of RF and Microwave applications. RF terminators are generally available with male connectors, however, for special applications, female RF terminators are also available with all types of RF connector options.
In this article, we cover the following details about RF and Microwave termination, which will help the designers and RF system users to select the suitable RF termination from the RF component manufacturers from any part of the world.
RF and Microwave coaxial, SMD, or waveguide termination are used to absorb RF energy and prevent RF signals from reflecting back to the RF circuit from unused open ports. RF terminators are available from lower power like 0.25 Watts, 0.5 Watts, 1 Watt, to the higher powers like 50, 100, 250, and 1000 Watts peak / CW power handling.
RF load or terminations are generally available with all the types of RF connector options like 2.4mm, 2.92mm, 7/16 DIN, SMA, N, SMB, SMC, BNC, Mini SMB, Mini SMP, QMA, SMP, TNC, etc.
To handle the power dissipation in high-power RF terminations, it is generally attached with aluminium, brass nickel-plated or stainless steel or beryllium copper finned heat sink.
RF terminators are classified on the basis of their structure, Power handling, matching type, and connector type used. There are many RF terminator manufacturers available who are specialized in specific filed of RF termination manufacturing.
In general RF and microwave terminations are of 3 types, Chip (SMD) RF termination, coaxial RF termination, waveguide RF termination.
Chip RF terminators are manufactured using thin-film technology and classified as flanged, leaded, panel mount, surface mount, crew terminals, stand-alone, and through-hole on the base of its terminals, form factors, and mounting styles.
RF and microwave terminations are available with different RF connectors like SMA, SMB, SMC, SSMA, SSMB, SMP, TNC, Triax, Twinax, BMA, BMMA, BNC, FME, Type G, MCX, MHV, MMCX, 1.85 mm, 2.4 mm, 2.92 mm, 3.5 mm, and 7 mm, Type C, Type F, Type N, QMA, QWS, and SC. RF terminators are also available for Ultra high frequency (UHF) and low-frequency applications with suitable connectors.
RF and microwave terminations are available with RF impedance of 50 Ohm, 75 Ohm for low power, medium power, and high power handling applications.
RF & microwave terminators are available in both Matched and Unmatched types. In matched type, the impedance of the RF terminator is matched to the output connector of the RF system where we need to connect the RF terminator. Impedance matching is the process of making an impedance match between the load impedance to the source impedance.
The impedance value of the RF terminator will not be a standard value for the specific applications, designers can contact the manufacturers for any specific impedance matching requirements.
The prime application of the RF terminator is to terminate the open RF ports to avoid the RF power reflection to the system. For any multi-port RF system, all the free/open/unused RF ports should be terminated to absorb the RF signal reaches to it.
RF terminations are available in various form factors like chips, coaxial, waveguide type, with power ratings of low to very high value with matched and unmatched to terminate the RF open ports. By terminating the open ports, RF systems will get a perfect impedance match and the performance of the system will be improved.
RF Terminations are used in measurement systems as dummy loads to ensure an accurate measurement. Terminations are used in directional couplers to terminate the reflected power port and in the RF circulators to make it an Isolator.
Below are the key specifications that need to consider in the selection of RF and Microwave Terminators in the design of the RF and microwave systems.
The frequency range of operation is the frequencies over which RF terminations are designed to operate. RF designers need to select RF terminators covering the full range of frequency of operation of the RF circuit.
VSWR and return loss indicate the reflection of the RF signal back into the circuit. Ideally, there should not be any reflection for the perfect operation of the RF circuit.
Return loss is the measure of the mismatch between the RF terminations and the impedance of the system. Ideal to select the RF termination with VSWR near 1 and a lower figure for the return loss.
The Average Power in watt of the RF and microwave termination needs to be more than the output power of the RF circuits. In General, RF terminators should need the proper heat sink to handle the maxim expected power from the RF circuit otherwise high power may lead to the breakdown of the RF terminator.
In general, RF terminators are available in 50 Ohm impedance terminations and 75 Ohms impedance options. In addition, specific RF terminations are available from manufactures with custom values of impedance based on the RF system requirements.
The impedance of the RF termination needs to perfectly match the characteristic impedance of the RF port on which it is being used.
Temperature handling of the RF terminator is one of the prime specifications that need to consider in the selection of an RF terminator. During high power of operation at the extreme temperature conditions, terminators generate higher temperature and it may cause to the break down of the terminators and this lead to the reflection of the RF power back to the systems and system may get damaged.
The ideal operating range of the RF terminator is -40ºC to +85ºC for the general RF and Microwave system applications.
RF terminators are available in different packages like a waveguide, surface mount, connectors, etc designers need to select the RF termination as per the customer design requirements.
Customers need to select the terminators as per space and size available in the RF circuit or the systems for the best space optimization of the RF systems.
RF and microwave terminators are the passive components used to terminate the RF signals from an RF system. The connector interface and gender of the RF terminator can be customized as per the requirement of the customer’s design needs from the different RF component manufacturers.
We hope this article about RF and Microwave terminator helps you to understand the Function of RF terminators, their application, and Selection parameters for a suitable communication system.
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