This invention pertains to the electrical power flow monitoring art and, in particular, to a bidirectional, fully compensated, line coupler.
Couplers, used to sense power flow on a line, are well known in the art. Generally, such couplers are employed integral with watt meters, whereby power flow on the line is monitored. In common applications, the coupler is inserted in the line and includes an inductive loop. The loop is oriented with respect to the conductor through the line whereby an electromotive force is generated in the loop proportional to the magnitude of electromagnetic radiation flow through the line. The induced EMF signal is rectified, commonly via a diode, and filtered thus producing a DC signal representative of power flow.
Prior art couplers suffer numerous problems. Firstly, since the power tap-off is realized via inductive coupling, the couplers have been frequency sensitive. Whereas the coupler can be tuned to produce accurate readings at a given frequency, the changing induced EMF at other frequencies produces significant errors in power readings.
A further problem with known couplers is inaccurate RF signal to DC output conversion. A basic source of inacccuracy, which often limits couplers, is the precision with which the rectifiers, e.g. diodes, convert the AC induced EMF to a corresponding DC level. This is a result of the nonlinear rise time of conventional diodes. Further, couplers to date have been temperature sensitive. Therefore, as a coupler is placed in temperatures other than those at which it is calibrated, errors are produced in the power reading.