Telecommunication is widespread in all areas of society. Although digital signal processing emerges on analog counterpart, analog signal processing is an indispensable part of the telecommunication. Some analog parts, especially band selection filter and oscillator of the transceivers must be reconfigurable for more convenience. Multi-standard transceivers increase the universality of the designed transceiver circuit for all applications to implement on a single chip. For example, for more convenience 4G cellular system transceivers must be suitable more than one standard for best connectivity. GSM, GPS, WCDMA, Wi-Fi (IEEE 802.11a/b/g/n), WiMAX, Bluetooth, Zee Bee and Ultra Wideband (UWB), are certain prospective standards that can be considered as pieces in the circuit of the final wireless network. The reconfigurable filter called as frequency agile filter is one of the background circuit for the multi-standard transceivers. The frequency agile filter allows to sense different protocols with only one circuit. Such a circuit can be a signal processing part of different positioning system's bands (GPS, GLONASS, Beidou, GNSS and Galileo) to process different positioning system protocols in the same circuit. Also, the design of reconfigurable low pass filter is one of the most critical part of the Zero-IF receivers. Furthermore, frequency agile filter can be considered as a part of frequency hopping system used in military applications for secure communication. Frequency hopping spread spectrum known as (FHSS) and direct-sequence spread spectrum (DSSS) are two types of encoding system. In FHSS transmission technology, the data signal is modulated with a narrowband carrier signal hopping arbitrarily frequency to frequency. The random modulation can be predicted by only the desired receivers by the aid of frequency agile filters. In this talk, new recent CMOS realization methods for agile filters suitable for encrypted communication will be presented including the concept, topologies, IC design, layouts and simulation results. All data is taken from the recent research works performed in Istanbul Technical University. Two different technology (TSMC 0.18 mu m and AMS 0.18 mu m) are used to design frequency agile filters.