Design of frequency selective limiting circuit

This paper explains the design of frequencyselective limiting circuit. The circuit is typically based on nonlinear matched reflection-mode bandstop resonator. This type of Frequency Selective Limiters achieves fast switching, high-level of power limiting, and flexible channel bandwidth. For single channel limiting, a device with one resonator (first order) produced a band-stop response centred at 2 GHz with 250 MHz of limiting bandwidth, 0 dBm limiting threshold, and 32 dB limiting level and it gave an all-pass response with less than 2.5 dB insertion loss at low RF powers. Multi-resonator filter has been used in order to improve the performance of the device. The prototype will produce intermodulation distortions and response time. Simulated results show an excellent highly selective bandstop performance at high powers with a near all-pass response at low signal powers

Tuning Range and Power Handling Analysis of DTC-based Matching Networks for Reconfigurable High Power RF Circuits

This paper presents the analysis of tuning range and power handling of digitally tunable capacitors (DTCs) in reconfigurable high power RF circuits. The proposed scheme can be applied to reconfigurable RF system design e.g. smart antenna, Software Defined Radio (SDR) and Cognitive Radio (CR) systems. The power handling of the DTC can be enhanced by connecting the DTC in series with a fixed capacitor. The combination of a DTC and a fixed capacitors leads to modified tuning range of the total capacitance. Both the power handling and the tuning range are described in this paper by empirical equations in such a way, that a proper combination of DTCs and fixed capacitors can be determined for the design of any reconfigurable RF system. As an example of applications, a frequency band reconfigurable power amplifier was designed and fabricated. The reconfigurable input– and output matching networks utilize DTCs and fixed capacitors as tuning elements