Types of RF Filters
A passive RF filter is a passive multiport device that allows signals to pass through at discreet frequencies but rejects any frequency outside of the specified range. Radio transmitters use low-pass filters to block harmonics that may interfere with transmission signals. These designs use specific topologies based on frequency and power handling requirements.
What to Understand About Lowpass and High Pass Filters
One problem that can be present when sending and receiving signals is load impedance on the circuits. Load impedance should match the internal impedance within the lowpass and highpass bands. This method minimizes the amount of signal reflection when there is a lot of frequency signals being sent out or received at any given time. Instead, the impedance should always remain constant no matter the amount of signal load that is going on through the transmitter or receiver.
Bandpass filters are offered with very narrow band high skirts to medium band and broad band with low loss. High power applications have a wide range of topologies such as Cavity, Combline, Interdigital, Coaxial, Suspended Substrate Stripline, Waveguide and mixed-Topologies.
Bandpass RF Filters Focus on a Specific Frequency Band
A bandpass filter design is coupled to the system between the two ports. This filter is designed to select a particular frequency band that will be allowed to pass through. It will reject all other high frequency and low frequency signals. A bandpass filter will come with important specifications that include passband that can focus on the frequency percentage or the stop/start frequencies used, the center frequency, and the rejection function that will have the steepness of the rejection as well as the rejection band widths.
Our Lowpass filters are low loss broad band filters, providing high power applications from a wide range of topologies such as Lumped Element, Coaxial, and Suspended Substrate Stripline as well as multiple topologies. Lowpass filters are mainly designed using the Chebyshev type and for those requiring sharp cutoff the modified elliptic type is used.
Lowpass RF Filters Only Accepts Low Frequencies
A lowpass RF filter will receive frequencies that are at a lower frequency as it will reject any higher gigahertz (GHz) frequencies that go over a set decibel (dB) cut off level. The lowpass filter has direct access to the port. Any frequency that is below the cutoff level will be directed to port 2. This function is accomplished by instituting insertion loss.
Insertion loss is when there is a loss of signal power when passing though the filter circuit. As the frequency's decibel range increases, the insertion loss increases until reaching the cut-off level as the lowpass filter completely rejects the frequency. To prevent the lowpass filter from having any high frequency capabilities, a re-entry mode is paced into the filter.
Our Highpass filters are broad band filters with low loss offered in high power applications with a wide range of topologies such as Lumped Element, Suspended Stripline, and Multiple Topologies.
Highpass RF Filters Allowing High Designed Frequencies
A highpass RF filter works as the opposite of the lowpass filter. Any frequency signal above the set decibel cutoff level will be allowed to pass through the filter, as it will be sent to port 3. A low frequency will be completely rejected.
The highpass filter will come with desired specifications such as insertion loss, return loss (when there is a loss in the signal's power when returned) and when there is a flatness for insertion loss (where there is a linearity to the filter) that goes above the cutoff decibel limit.
Our Notch/Bandstop filters are offered with a very narrow band high rejection to medium band through broad band filters with low loss for high power applications from a wide range of topologies such as Cavity, Combline, Interdigital, Coaxial, Suspended Substrate Stripline, Waveguide and Multiple Topologies.