Noise suppression method for an AM radio receiver using digital signal processing
Recently, electromagnetic interference in AM radio receivers associated with noise generated from the power control unit (DC-DC converters/inverters) and other power electronics devices, such as an electric power steering (EPS) control modules, in hybrid vehicles (HVs) has become a serious problem. In order to address this problem, most noise suppression methods use either noise filters (for noise sources) or shield wiring and ferrite cores (for noise propagation paths). We have proposed a noise suppression method through digital signal processing in an AM radio receiver. In this method, the received AM radio signal containing HV noise is first quadrature demodulated. Next, a replica signal of the noise is generated using the noise signal in the quadrature component. The replica signal is then subtracted from the AM radio signal containing the noise of the in-phase component. In this paper, first, we show the noise canceling method. And then, we construct a prototype of the radio receiver system based on the method. Finally, we demonstrate that the system can reduce the DC-DC converter noise and the EPS noise superimposed at the same time on the AM radio signal by more than 15 dB.
Inverter noise canceller for AM radio reception using PI algorithm
Electric vehicles and hybrid vehicles have been popularized in recent years. In such a vehicle, an inverter circuit which converts a direct current to an alternating current is mounted. Due to the noise from the inverter, reception quality of AM radio is deteriorated. This paper proposes a novel noise cancellation system composed of a noise sensor and an adaptive filter which is controlled based on PI (Power Inversion) algorithm. Numerical results show that the inverter noises can be reduced by the proposed system.
APPLICATION OF THE FINITE ELEMENT METHOD TO ROTARY-WING AEROELASTICITY.
Recent research in rotary-wing aeroelasticity has indicated that all fundamental problems in this area are inherently nonlinear. The non-linearities in this problem are due to the inclusion of finite slopes, due to moderate deflections, in the structural, inertia and aerodynamic operators associated with this aeroelastic problem. In this paper the equations of motion, which are both time and space dependent, for the aeroelastic problem are first formulated in P.D.E. form. Next the equations are linearized about a suitable equilibrium position. The spatial dependence in these equations is discretized using a local Galerkin method of weighted residuals resulting in a finite element formulation of the aeroelastic problem. As an illustration the method is applied to the coupled flap-lag problem of a helicopter rotor blade in hover. Comparison of the solutions with previously published solutions establishes the convergence properties of the method. It is concluded that this formulation is a practical tool for solving rotary-wing aeroelastic stability or response problems.