The diode losses are accurately measured by the technique described in Section 2. 2.3. The measurements themselves are accurate to within 2% at diode loss levels corresponding to incident power levels of two watts or more. Since the diode losses at these power levels are typically less than 10% of the absorbed microwave power, the measurement uncertainty with respect to the absorbed microwave power corresponds to a probable error of 0. 2%. This of course, is considerably better than the measurement of the microwave power input and no further refinement is necessary. The measurement of the circuit losses (other than those in the diode itself) represent the remainder of the energy output of the system. Getting an estimate of these losses can be approached in two ways. One of these is by computer simulation to be discussed in Section 2.3. In the mathematical model the skin resistances in the circuit are modeled and given a value. An accurate computation of power losses is then provided by the computer simulation of the overall functioning of the rectenna element. Typically, all of the circuit losses amount to 2. 15%, of which 1.9% represents circuit losses in the microwave input filter, and 0. 25% is the remainder. However, the validity of the results from computer simulation depend upon the assumptions made with respect to skin resistance. Another approach to establishing these losses is to make an insertion loss measurement upon the input filter which the computer simulation (as well as simpler analysis) indicates is the major portion of the circuit losses. These losses were measured to be 2.37%± 0.3% at the fundamental frequency, and seen to be 0.47% higher than those obtained by computer simulation. They are believed to be more valid because no assumptions of the skin resistance were needed. We have decided to use the measured value of 2.37% for the input filter losses and to add to this the 0. 25% for the rest of the circuit losses as determined by computer simulation. Thus, the circuit losses are established as 2. 62% and the probable error associated with this is 0. 4%. The probable error of the individual measurements is listed below : P.E. of microwave pDwer input measurement ±0.6% of absorbed microwave power P.E. of diode dissipation losses ±0.2 of absorbed microwave power P.E. of circuit losses ±0.4% of absorbed microwave power P. E. of D. C. power output measurement ±0. 2% of absorbed microwave power From the listing, the composite probable error of balancing microwave power input against the sum of de power output, diode losses, and circuit losses may be computed. It is found to be ±0. 75%. In Table 2-1, the DC power output, diode losses, and circuit losses are given in terms of their ratio to the absorbed microwave power in the
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