Computer-Aided Design of Lossless Crossover Networks
Conventional crossover network design tends to be an empirical art, due mainly to the complex load impedance, and to drive unit amplitude response irregularities. This paper presents a new computer-aided design method, which is not based on the normal optimization routines, and as such does not require a circuit topology from which to start optimization. Instead, assuming a lossless network and working from the Thevenin equivalent of the impedance of the network as seen from the load, the real and imaginary parts of this impedance, being related by the Hilbert Transform, may be calculated to give the desired power transfer to the load. From the knowledge of the load impedance, the voltage response can thus be determined. A rational function approximation is then made to this impedance curve, from which a lossless network terminated in a resistor (the cable plus generator resistance) may be synthesised using standard circuit theory techniques. Input to the program is simply measured data of the load impedance, the target response and the drive unit response. At present the technique does not take into account the practicalities of component tolerance and losses.
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