An automatic TV tuner alignment system

Abstract

A new approach to automatic TV tuner alignment is presented. It contains two aspects, i.e. hardware (consisting of piecewise-linear transcoders) and software algorithms (which optimize the transfer functions of these transcoders with respect to measured data points). This approach allows one to choose the desired tuner performance and it yields a major improvement of the performance/price ratio compared to the conventional solution. More precisely, the performance is defined by the maximum frequency mistuning of each RF filter. For given transcoder memory sizes, the proposed approach improves the performance (i.e. decreases mistunings) by a factor of 2.7 to 4.5. Or, for a given performance, it reduces the transcoder memory sizes by a factor of 2. The target performance considered is a maximum frequency mistuning of 600 kHz in the overall frequency band of operation. This target is reached with a memory containing only 90 bits per RF filter. The proposed approach is also a good candidate for future high-definition TV standards, which will require lower frequency mistunings. Besides its use in TV tuner alignment, it is attractive in all systems requiring very simple and/or fast adaptive transcoders. It may be applied to the automatic electronic tuning of integrated active filters and phase shifters.