Frequency discriminators are RF or microwave devices that are used to detect a signal with a particular frequency. They carry performance specifications such as frequency range, sensitivity, rise time, video bandwidth, input voltage standing wave ratio (VSWR), power output, and power supply. Sensitivity is normally taken as the minimum input signal required to produce a specified output signal with a specified signal-to-noise (S/N) ratio. Rise time is the time required for a variable to change from its baseline value to a given percentage of its intended final value. Input VSWR expresses the amount of reflected energy at the input of the device. Operating temperature is also an important parameter to consider when selecting frequency discriminators.
Frequency discriminators differ in terms of form factor. Choices include surface mount technology, through-hole technology, flat pack, connectorized, and waveguide assembly. Surface mount technology (SMT) adds frequency discriminators to a printed circuit board (PCB) by soldering the leads to the top surface of the board. Through-hole technology (THT) mounts components by inserting the leads through holes in the board and then soldering the leads in place on the opposite side of the board. Flat pack (FPAK) frequency discriminators have gull wing or flat leads on two or four sides. Connectorized devices attach with coaxial connectors. Waveguide assemblies are circular, elliptical, or rectangular metal tubes or pipes through which electromagnetic waves are propagated.
Connectorized frequency discriminators use a variety of RF connectors. Choices include BNC, TNC, MCX, MMCX, SMA, SMB, SMP, Type F, Type N, UHF, mini-UHF, 1.6 / 5.6 and 7-16. Bayonet Neil-Concelman (BNC) connectors are used widely in video and RF applications to 2 GHz. Threaded Neil-Concelman (TNC) connectors are similar in size to BNC connectors, but feature a threaded coupling nut for applications that require performance up to 11 GHz. Miniature coaxial (MCX) connectors provide broadband capability through 6 GHz and are used in applications where weight and physical space are limited. Micro-miniature coaxial (MMCX) connectors are smaller than MCX connectors and feature a more robust interface for greater durability. Frequency discriminators that use specialized or proprietary connectors are also available.
Standards for frequency discriminators include RoHS and WEEE. Restriction of Hazardous Substances (RoHS) is a European Union (EU) directive that requires all manufacturers of electronic and electrical equipment sold in Europe to demonstrate that their products contain only minimal levels of the following hazardous substances: lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyl and polybrominated diphenyl ether. Waste Electrical and Electronics Equipment (WEEE) is an EU directive designed to encourage the reuse, recycling and recovery of electrical and electronic equipment. WEEE-compliant frequency discriminators are also designed to improve the environmental impact and performance of this equipment.