Patent No. 5204613 RF power sensor having improved linearity over greater dynamic range

 

Patent No. 5204613

RF power sensor having improved linearity over greater dynamic range (Cripps, et al., Apr 20, 1993)

Abstract

A radio frequency ("RF") power sensor providing RF signal power sensing with reduced dependency upon its input signal power level includes multiple series-connected diodes for detecting the power of an input RF signal and providing an output voltage representing that power. The multiple series-connected diodes couple the input node shunted by an input load resistor to the output node shunted by an output filter capacitor. Using multiple series-connected diodes results in reduced reverse bias voltages across the diodes (presented by the charged output filter capacitor), thereby increasing their junction capacitances. These increased junction capacitances, in turn, result in reduced fractional changes thereof (e.g. capacitance "modulation") over changes in the input RF signal power. This reduction in fractional capacitance changes as a function of input signal power variations, further in turn, results in reduced input signal power dependency of the sensors' impedances and sensitivities. Therefore, the power detection performed by the diodes becomes more predictable, e.g. more linear, over a broader input RF signal power range.

Notes:

RF power sensor having improved linearity over greater dynamic range. Filed May 1991, granted April 1993. Again, coupled with a computer that could scan the frequencies and store the readings in memory and modified to detect the pulsed or variable continuous waves might be useful in detection of the psychotronic attacks. The patent says that the device can be built with a variety of different parts. Also says that it can be modified with more detector diodes in series which should increase both sensitivity and accuracy.

SUMMARY OF THE INVENTION

An RF power sensor in accordance with the present invention provides RF signal power sensing with reduced dependency upon input RF signal power. The effects of inherently power-dependent components within the power sensor are reduced, thereby giving the power sensor a wider accurate dynamic range.

The present invention includes at least two series-connected detector diodes coupling the input node, shunted by a load resistance, and the output node, shunted by a bypass capacitance. The multiple series-connected diodes have increased junction capacitances due to reduced reverse junction bias voltages. The increased junction capacitances experience reduced fractional capacitance changes due to changes in the input RF signal power level. This causes the fractional junction capacitance changes as a function of input RF signal power variations to be reduced, thereby resulting in reduced input RF signal power dependency of the diode's junction capacitances, and therefore the power sensor in general. Thus, the power detection performed by the diodes becomes more linear as a function of input RF signal power.

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It should be understood that the present invention is not limited to the use of only two detector diodes in series. As desired, more than two series-connected detector diodes can be used in accordance with the present invention. It should be further understood that a power sensor in accordance with the present invention can be fabricated from various forms of detector diodes, such as discrete diodes in chip or packaged forms, or monolithic diodes within a common integrated circuit. Moreover, the passive components (e.g. particularly the tuning inductance and bypass capacitances) can be realized with discrete, lumped component elements, or alternatively, with discrete, lumped component elements in combination with parasitic elements.

It should be still further understood that circuit realizations of a power sensor in accordance with the present invention can include discrete packaged devices interconnected on a printed circuit board, chip and thin film or thick film devices interconnected in a hybrid circuit form, or in monolithic integrated circuit form. For example, a circuit realization of a power sensor in accordance with the present invention can be achieved according to design and fabrication techniques disclosed in U.S. Pat. No. 4,360,865.

Various alternatives to the embodiments of the present invention described herein can be employed in practicing the present invention. It is intended that the following claims define the scope of the present invention, and that structures and methods within the scope of these claims and their equivalents be covered thereby.