2 research outputs found
Analogue circuits for low power communication
Low power electronic circuits are required to extend the operational
time of battery operated devices. They are also necessary
to reduce the power consumption of equipment in general, especially
as the world tries to cut energy usage. The first section
of this thesis explores fundamental and implementation limits for
low power circuits. The energy requirements of amplification are
presented and a lower bound on the energy required to transmit
information over a point to point link is proposed.
It is evident from the low power limits survey that when a transistor
is biased, significant thermodynamic energy is required to
reduce the resistance of the channel. A transmitter is presented
that turns on a transistor for 0.1 % of transmitted time. This
transmitter approximates a Gaussian pulse by allowing the impulse
response of two 2nd order transmitting elements to sum in
free space. The transmitter is of low complexity and the receiver
architecture ensures that no on-line tuning is required. Measured
results indicate that by using coherent detection a 1 Mbps, 50
mm distance link with a bit error rate of 10−3 can be achieved.
The bandwidth of the transmitted pulse is 30-37.5 MHz and 30
dB of out of band attenuation is provided.
An analogue Gabor transform is described which splits a signal
into parallel paths of a lower bandwidth. This enables post processing
at lower clock rates, which can reduce energy dissipation.
An implementation of the transform using sub-threshold CMOS
continuous time filters is presented. A novel method for designing
low power gmC filters using simple models of identical transconductors
is used to specify transistor sizes. Measured results show
that the transform consumes 7 μW for an input signal bandwidth
of 4 kHz