Adjusting Resonance is so called because the new resonant circuit
naturally adjusts to any stimulus frequency over a designed band,
independent of the efficiency level. An example is shown comprising
a conventional resonant circuit with an additional MOSFET and a second
waveform is stimulated in the resonance, the MOSFET is turned on for a
fraction of the full duty cycle, depending on the amplitude of the
resonance and the constant gate voltage Vg. Here the MOSFET is being
used as an analogue element, charged through the inductance of the
antenna - this gives efficient operation without switching losses
and high frequency noise. Any frequency within the
following two limits will cause the circuit to 'resonate':
circuit is adjusted to the stimulus frequency, the amplitude of the
resonance is adjusted through Vg; for example, as Vg is reduced to
negative voltage the amplitude of the resonance ramps up. Control can be
either external or via feedback from the resonance amplitude.
beneficial results are summarised below that are described in more
detail in Applications.
of aligning two narrow resonances to transfer power or information is
simplified. Now one or both may be made to operate over a fixed band,
with overlapping bands the only necessity.
of a conventional resonance by the environment (metal, temperature, etc)
will shift the operating band of the resonance. However, provided the
band still encompasses the target operating frequency, normal operation
will still be possible.
to detuning, frequency shifts resulting from component variation at
manufacture will have no detrimental effect on operation if the target
operating frequency is still encompassed.
cases multiple frequencies of operation are required, for example when
EMC licensing bands change across country borders. This may be
accommodated by the width of the operating frequency band.
Adjusting Resonance tunes to the stimulus, Vs. This may be driven
directly from a highly stable source, such as a crystal oscillator, with
a very low phase noise. Excellent read range in RFID applications may be
achieved with this arrangement.
properties come with no major cost overhead. In fact, savings are
expected through the relaxation of component tolerance at manufacture.
summary, the self adjusting resonance breaks the conventional limit
between bandwidth and efficiency. Moving away from a classic linear
resonator provides a whole host of attractive attributes that will
improve the performance of many RF products.
information available on request and detailed in