Reactance buffered loop antenna and method for making the same

A buffered loop antenna, having a plurality of selectable loop circumferences, the loop antenna being coupled to a receiver having signal and ground inputs coupled to an antenna resonating capacitor for resonating the loop antenna to a predetermined frequency, said loop antenna comprising:

• a first conductor, having a first end coupled to the receiver signal input and a second end, said first conductor forming a first portion of the loop antenna;
• a second conductor, having a first end coupled to the receiver ground and a second end, said second conductor forming a second portion of the loop antenna;
• reactance buffer means, comprising
• a reactance buffer input coupled to said second end of said first conductor,
• a plurality of taps linearly disposed along a longitudinal axis of said reactance buffer the distance between the outermost of said plurality of taps providing a predetermined length corresponding to the loop circumference adjustment, and
• a plurality of reactance elements, arranged non-serially between said reactance buffer input and each of said plurality of taps, wherein one or more of said reactance elements are coupled between said input and a corresponding one of said taps to provide a substantially constant reactance when measured between said reactance buffer input and each of said plurality of taps;
• and
• coupling means, coupled to said second end of said second conductor, for coupling said second conductor to any of said plurality of taps,
• whereby the resonant frequency of the loop antenna remains substantially constant when any of said plurality of taps is selected to adjust the loop circumference.

A wristband loop antenna for a wrist worn electronic device, the device including a receiver having signal and ground inputs coupled to an antenna resonating capacitor for resonating the loop antenna to a predetermined frequency, said wristband loop antenna comprising:

• a first wristband section, including
• a first conductor, having a first end for coupling to the receiver signal input and a second end, said first conductor forming a first portion of the loop antenna within said first wristband second, and
• reactance buffer means, comprising
• a reactance buffer input coupled to said second end of said first conductor,
• a plurality of taps linearly disposed along a longitudinal axis of said reactance buffer the distance between the outermost of said plurality of taps providing a predetermined length corresponding to the loop antenna diameter adjustment, and
• a plurality of reactance elements, arranged non-serially between said reactance buffer input and each of said plurality of taps, wherein one or more of said reactance elements are coupled between said input and a corresponding one of said taps to provide a substantially constant reactance when measured between said reactance buffer input and each of said plurality of taps;
• and
• a second wristband section including
• a second conductor, having a first end coupled to the receiver ground and a second end, said second conductor forming a second portion of the loop antenna within said second wristband section, and
• coupling means, coupled to said second end of said second conductor, for coupling said second conductor to any of said plurality of taps, whereby when the wristband length is adjusted by selecting any of said plurality of taps, the resonant frequency of said loop antenna remains substantially unchanged.

A wrist worn receiving device, comprising:

• a receiver located within a housing;
• and
• a wrist band, including first and second wrist band sections coupled to said housing, for securing the housing to a users wrist,
• said first wristband section forming a first portion of a loop antenna, and including a reactance buffer having an input coupled to said receiver, and a plurality of outputs linearly disposed along a longitudinal axis of said first wristband section opposite said housing, said reactance buffer comprising a plurality of reactance elements, arranged non-serially between said reactance buffer input and each of said plurality of outputs, wherein one or more of said reactance elements are coupled between said input and a corresponding one of said outputs for providing a substantially constant reactance measured between said reactance buffer input and each of said reactance buffer outputs,
• said second wristband section forming a second portion of the loop antenna, and including a coupling means, coupled to said receiver and affixed to said second wristband section opposite said housing, said coupling means providing selective coupling to said plurality of reactance buffer outputs when securing the housing to the users wrist,
• whereby the length of said wristband is freely adjustable to fit the users wrist by coupling said coupling means to a corresponding one of said plurality of reactance buffer outputs, and whereby the resonant frequency of said loop antenna remains substantially unchanged when said coupling means is coupled to any of said plurality of outputs.