Tham khảo tài liệu 'ultra wideband communications novel trends system, architecture and implementation part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Ultra Wideband Impulse Radio Superregenerative Reception 115 Lastly and paramount to this chapter SR receivers are very well suited to UWB IR communications due to the low duty cycle of the received signals. Traditionally SR receivers have had three major drawbacks Excessive reception bandwidth when applied to narrowband communications. Because of their relatively short sensitivity periods their RF bandwidth is much wider than the signal modulation bandwidth making them more sensitive to noise and interference compared to other systems. Frequency instability in tank LC implementations due to temperature changes mechanical shock etc. This problem which is not exclusive of SR receivers can be overcome via stable frequency references such as coaxial ceramic resonators or acoustic wave devices . SAW BAW and FBAR . Re-radiation part of the RF energy generated in SR oscillators tends to be radiated by the receiver antenna becoming a source of interference. However this effect can be minimized through a well-designed low-noise isolation amplifier. Input voltaje V b RF Damping factor z Output voltaje Vo ------o- Build-up from noise -e Sensitivity period Build-up from signal Fig. 1. a Block diagram of an SR receiver and b input signal instantaneous damping factor generated by the quench oscillator and output voltage in the linear mode of operation. Ơ 1 1 Ơ 1 O 1 __UdLA __ t Fig. 2. Characteristic signals in a classical SR receiver operating in the linear mode. 116 Ultra Wideband Communications Novel Trends - System Architecture and Implementation 3. Superregenerative architectures for narrowband wideband and UWB signal reception Although SR receivers have traditionally been used in short-range narrowband communications new modes for their operation have been proposed and evaluated over the past few years. In this section we describe and compare these operation modes and their corresponding receiver architectures to evaluate their suitability for UWB IR signal .
