Coupling circuit

#The present invention relates to circuits for connecting the output terminals of a signal source across a load impedance.

#The operation of many electrical and electronic systems relies on the application of a voltage across a load from a voltage source and it is recognized in the art that the performance of such systems depends on the quality of the coupling between the source and the load, i.e. the extent to which the voltage across the load corresponds to, or equals, the open circuit source voltage or an amplified version of the source voltage.

#Ideal coupling would result in the appearance of a voltage, or possibly a current, exactly proportional to the open circuit source voltage across the load with respect to both time and frequency domain characteristics as the source signal.

#FIG. 1 is a block diagram illustrating a system for providing improved coupling in accordance with the present invention.

#FIG. 2 is a circuit diagram illustrating a circuit according to the present invention, connected to a signal source and a load.

#FIG. 3 is a detailed circuit diagram illustrating a preferred embodiment of the circuit according to the present invention.

#FIG. 1 is a block diagram illustrating a system which includes a voltage source 2, a load 6, and circuit components 4 and 8 for coupling the source to the load. Each block is represented by its Fourier transform, or frequency domain, function. Thus, voltage source 2 has the transfer function V.sub.i (s) and load 6 has the transfer function with the reactive component g(s). Conventional arrangements for coupling source 2 to load 6 would be composed of a circuit device as represented by block 4. According to principles known in the art, block 4 would be constructed to cause V.sub.L (s) to have a value as close as possible to V.sub.i (s) and to cause V.sub.i (s) to have a value as close as possible to the open circuit output voltage of source 2. However, it will unavoidably occur that the voltage coupling between source 2 and load 6 will be influenced by transfer functions with the reactive components f(s) and g(s), which will introduce some difference between the open circuit voltage provided by source 2 and V.sub.L (s).

#In the prior art, efforts have been made to compensate for such difference by the provision of additional components which are capable of eliminating, or at least substantially reducing, that difference at a defined frequency.

#According to the present invention, coupling unit 4 is supplemented by a waveform preservation, or compensation, element or unit 8 having the transfer function with the reactive component r(s), which is capable of substantially completely compensating for the influence of f(s) and g(s) on V.sub.L (s) over a broad frequency band. Specifically, this result will be completely achieved if: