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A single-frequency adaptive noise canceller (SF-ANC) using the LMS algorithm can be used to remove power-line interference from electrocardiograms (ECG's) [l-21. The procedure is computationally rapid, provides a zero at the notch frequency and can often be carried out in close to real time. In this paper we study the performance of a SF-ANC and present some important but little understood experimental results which can be helpful in designing a real-time ANC. We show that an SF-ANC based on the LMS algorothim will not only attenuate signal components near the interference frequency but also amplify signal components far away from the interference frequency . We also demonstrate that the signal-to-noise-ratio(SNR) at the output is independent of the SNR at the input and that performance of an SF-ANC will be adversely affected by the arrival of a large magnitude signal such as the QRS complex in ECG's.

In the paper the correlation properties of wavelet transform coefficients are studied. By employing a high correlation property of the wavelet transform coefficients along the same prediction channels, a hybrid image coding system is proposed and designed. The simulation results show that the developed coding scheme is superior to its counterparts.

Uniform distribution of radiated power is a necessary requirement in many aerial applications. Radio beacons and television transmitting aerials are examples of such a requirement. Aerials made from slotted circular waveguides have found application in engineering practice. We have computed the azimuth distribution of radiation from waveguides with eight and twelve, transverse slots. Combined with existing literature, the design of aerials with extremely high azimuth uniformity is possible.

An investigation into the performance of spherical-reflector antennas with Gregorian correctors is described with particular reference to their application in satellite-communications ground stations. Feeds comprising corrugated scalar horns propagatinga balanced HE11 hybrid mode are considered, this choice eliminates cross-polarisation components of field in the spherical-reflector aperture. The theoretical performance of the spherical reflector with various subreflector profiles is estimated by using the aperture-field method to calculate the antenna-gain factor, far-field radiation pattern and overall efficiency as functions of the subreflector and feed positions. An optimum subreflector profile is chosen on the basis of maximum overall efficiency for a particular feed and antenna-scan angle. It is concluded that, for conventional scalar horns, the side-lobe level of the far-field radiation pattern is rather high, being about −11.5 dB with a corresponding gain factor of 0.85 and an overall efficiency of 0.65 for a scan angle of ±7°. Much lower side-lobe levels can be achieved, together with high gain factors, but only with lower overall efficiency. The spherical-reflector-antenna performance is compared to that of a front-fed paraboloid with the same feed and a higher efficiency is predicted for the former antenna. Preliminary consideration is given to the design of a dualmode feed so as to provide an additional tracking pattern, also to initial mechanical-design aspects.