A New carrier recovery subsystem for binary PSK systems using synchronized push-pull oscillator is described. A property that the push-pull oscillator has two stable states of which the phase difference is π, can be well applied for this purpose. This new subsystem does not include phase-locked loop (PLL), therefore pull-in time and pull-in range are not limited by the loop delay of PLL. The circuit of this push-pull oscillator is very simple. Yet, it is proven to achieve rather good performance, if a limiter which normalizes the input amplitude, when practically deformed on account of the band-limiting, is attached. Our experiments have had good agreement with the theory and computer simulation.

This paper describes a new method to estimate traffic load of communication nodes, such as switching systems. The new method uses the system identification, which is often used in designing control systems of real systems. First, this paper makes clear that, under certain conditions, the input and output relation of a communication system, which is composed of a number of communication nodes, is formulated into a dynamic state equation that is classed as a time-invariant, single-input single-output, discrete-time system. Next, it is explained that traffic load information is estimated by identifying the dynamic state equations of the communication system. Then, the traffic load estimator is synthesized using the system identification in it. Finally, it is clarified by computation simulations that the proposed method is very applicable in estimating the traffic load of each communication node.