Bandwidth Control refers to the use of feedback to control the
communication bandwidth of a system. More specifically, in RFID a steady
state powering field is required onto which a communication signal is
modulated. The feedback allows the steady state signal to be supported
by a highly efficient resonance, whereas the smaller modulation signals
are controlled to give a fast response and high speed communication that
would otherwise be prevented.
picture shows an implementation together with the Self Adjusting
Resonance, where a feedback path has been added between the resonance
amplitude and the stimulus signal, Vs. This feedback path acts to keep
the resonance amplitude constant over the timescale of the modulation.
As such the circuit responds immediately to any load modulation, which
is now registered through the level of power input into the system.
Bandwidth Control breaks the link between the dynamics of the circuit at
modulation frequencies and those for a slowly varying powering signal.
This has particular application in full-duplex RFID, where communication
and power functions are carried out simultaneously.
beneficial results are summarised below that are described in more
detail in Applications.
technology opens up the use of highly efficient antennae for RFID, which
has a direct benefit on the power drain of the reading process. A
natural application is the hand-held reader where battery life is an
improved in two ways. Firstly, increased efficiency means that the
energising field may be increased for a given power budget. Secondly, the task of demodulating
the small communication signal is made easier because the of the low
steady state loss. The power required to sustain the energising field is
reduced and the relative amplitude of the load modulation is increased.
information available on request and detailed in