Sharif Digital Repository

A new broadband frequency discriminator is introduced for demodulating the frequency modulated signals in the microwave frequency range. Direct demodulation with no need for tuning the center frequency of the resonance circuits is the most important advantage of the proposed technique. This technique uses the in-phase/quadrature demodulation, in some manner, without using any additional local oscillator for down conversion. Simulation of the proposed demodulator has been done with Advanced Design System software to evaluate and predict the system behavior. A setup based on the proposed method was designed and implemented in order to verify the accuracy of the theory. We tested the proposed... 

This paper presents application of high-Q cavity resonator in phase-shifter less technique. A mathematical analysis is presented to show the dependency of the measured phase noise in terms of loaded quality factor and resonance frequency of the high-Q cavity resonator. Experimental measurements resulted from different methods for a synthesized oscillator at 9.976 GHz show great validity and accuracy of the proposed technique. This technique needs no tuning for the phase-shifter and can introduce better sensitivity compared to the setup that uses a delay-line as a frequency discriminator element due to much lower insertion loss particularly at high carrier frequencies. The sensitivity of -113... 

In this paper, a modified method based on the frequency discriminator technique for measuring phase noise of microwave oscillators is presented. In the proposed method, the phase shifter is omitted. In contrast, a 90° hybrid with one more channel containing a phase detector, and a low-noise amplifier is added to the measurement setup. It can be said that an in-phase/quadrature phase-noise detection has been developed. With the proposed method, tuning of the variable phase shifter is not needed anymore. Therefore, the measurement is done automatically, and as a result, the measurement time is decreased. Another considerable advantage of this method is that the method is theoretically... 

In this paper a new method for measuring phase noise of microwave oscillators based on delay line frequency discriminator is proposed. Elimination of phase shifter is the major advantage of this technique over the traditional delay line technique. By using this new technique, manual or electronic tuning of phase shifter to reach phase quadrature at the phase detector input ports is not needed anymore. A 90-degree hybrid is used in this technique and another path including a phase detector and LNA is added. Finally by using a dual channel FFT analyzer and performing some processing over the sampled data of the two channels, the phase noise of the oscillator will be extracted. A setup based on... 

Inherent properties of UWB signals prevent both coherent and noncoherent processing with conventional methods used in narrow-band RADARs. In this paper, we show how to exploit the Hough transform, first developed to detect lines in an image distorted by noise, to detect moving objects from successive scans that are corrupted by noise and clutter. We discuss why conventional methods fail to process UWB pulses noncoherently/coherently and investigate different aspects of using the Hough transform in noncoherent integration of UWB signals. Simulation results to support our approach are also presented. © 2008 EuMA  

Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a novel data redirection method to mitigate the impact of node misbehavior on network...