Difference between RF filter and RF duplexer | Filter Vs Duplexer
This page compares RF filter Vs RF duplexer and describes difference between RF filter and RF duplexer with respect to various comparison parameters.
RF Filter
The component used to filter out undesired RF signals in the particular band is called RF filter. It is mainly used to block few range of frequency and pass the others. Based on functionality various filter types have been developed viz. low pass, high pass, band pass and band stop. It helps to improve SNR (Signal to Noise Ratio) of the system.
The figure depicts LPF response. As shown this filter type passes signal frequencies below certain cut-off frequency and block all the frequencies above it. It is mainly used to remove high frequency components from the RF signal.
The figure depicts HPF response. As shown this filter type passes frequencies above certain cut-off frequency and block all the frequencies below it. It is mainly used to eliminate low frequency components from the RF signal.
The figure depicts BPF response. As shown this filter type passes frequencies within particular band and block signals outside this frequency band. It is mainly used to select desired frequency range and reject other frequencies outside this band.
The figure depicts BSF response. As shown this filter type passes frequencies outside the particular band and block all the frequencies in particular band. It is mainly used to remove undesired signals from specific band.
Based on transmission line type and its construction, RF and microwave filters are divided into microstrip filter, interdigital filter, coaxial line filter, waveguide filter, comb line filter, hairpin filter type, spiral cavity type filter, cemamic di-electric filter, lumped filter etc.
The common specifications of RF filter are as follows.
• RF Center Frequency
• Passband Bandwidth
• In Band Insertion loss
• Out of band suppression
• Passband ripple
RF Duplexer
The device which allows RF transceiver with single antenna to operate simultaneously on same frequency. It allows receiver to continue receiving the signals while transmitter is transmitting the signals and vice versa. It consists of filters and other RF components which helps to segregate signals by frequency, time or polarization.
➨For example, in FDD topology, duplexer uses filters which helps to separate incoming signal and outgoing signal by frequency.
FDD based duplexer allows transmitter and receiver to operate at the same time on different frequencies without any kind of
interferences. This is shown in the figure for GSM system.
➨In TDD topology, duplexer uses switch or filter which helps to separate incoming signal and
outgoing signal by time. In this case, transmitter and receiver uses same frequency band but performs their
respective operation in different time slots.
In addition to simultaneous transmission and reception, RF duplexers provides
isolation to the output of the transmitter and prevents damage to the receiver. Hence
it protects sensitive components of the receiver.
Refer SAW duplexer basics >> and
advantages and disadvantages of RF duplexer
for more information.
➨As mentioned above, both RF filter and duplexer are used in wireless systems for different functions.