IEEE Circuits and Systems Magazine - Q1 2022 - 57

PN sequences, which would allow
multiple transmitters to share the
same channel in which PN sequences
are allocated to different users
[41]. Typically, a longer preamble
length is needed for long-range
communication. For instance, a
30 μS preamble time is used when
the system operates under a relatively
low SNR or with high dispersions
[2]. Targeting high data rate
communication at short range, a
5 μs preamble length is used for a
channel operating under high SNR
and low channel dispersion. Under
nominal SNR, the preamble length
is set to be around 15 μs.
Receiver (Rx)
LNA
Multiplier
Integrator
Correlator
Pulse
Generator
Clock Generator
and Synchronizer
Baseband
Processor
DA
Pulse Modulator
Transmitter (Tx)
Figure 19. Architecture of UWB wireless transceiver [34] © 2006 IEEE.
B. Non-Coherent Low Power
CMOS UWB Transceiver
An innovative pulse amplitude modulation technique
with a non-coherent demodulation technique is presented
in [33]; the fully integrated transceiver (TRX) was fabricated
in a 0.18-μm CMOS process. The TRX can achieve
a transmission rate from 1Mbps to 50 Mbps with low
power consumption in non- coherent operating mode,
demonstrating the potential to be deployed in wireless
personal area networks (WPANs), intelligent sensor networks,
miniaturized biomedical imaging systems, and
versatile radar sensing systems [41].
A pulse-based UWB scheme with noncoherent demodulation
has been demonstrated in Fig. 18(a). The architecture
can enable a relatively high data rate without using
the synchronization module. The short Gaussian pulses
are generated by the pulse generator. The pulse is approximately
symmetric around its peak and is with a 2 GHz
bandwidth. The largest peak-to-peak swing is around
30 mV with an RMS error of 3%, meeting the requirements
for UWB communications. By tuning the rise time of the input
signal, the pulse width is configurable. Moreover, the
amplitude of the pulse is also tunable by the front-end circuits.
The integrated TRX is tested with chip-on-board. The
measured time-domain UWB pulse is approximately symmetrical
with a short duration interval of around 0.8 ns [33].
C. Coherent CMOS-Integrated UWB Transceiver
The impulse radio transceiver has been designed to support
inter-chip wireless channel communication meeting
peripheral component interconnect express (PCIE)
standard has been presented. The proposed chip in [34]
is fabricated in a 0.18μm CMOS process. The UWB impulse
radio transceiver architecture is shown in Fig. 19,
which comprises a UWB Gaussian pulse generator (PG),
FIRST QUARTER 2022
TX Data
RX Data
a modulator, and UWB driver amplifier (DA) for the
transmitter [34]. A Gaussian PG is used to generate UWB
Gaussian pulses. The receiver contains a UWB LNA, a
correlator consisting of a multiplier and an integrator,
an ADC, and a clock generation and synchronization
module. The LNA is connected to the antenna with a
matching network to enable maximum power transfer efficiency.
The received pulses are amplified to a suitable
energy level for further signal processing by the LNA onchip.
The signal data is recovered by the correlator and
converted to the digital domain by an ADC for further
processing. The baseband module provides multiple
controls including clock generation, synchronization,
and data processing [34]. The measured frequency spectrum
of the pulse is shown in Fig. 20, which is in accordance
with the FCC standards [34].
FCC Spectral Mask
Figure 20. Measured frequency spectrum of pulses [34]
© 2006 IEEE.
IEEE CIRCUITS AND SYSTEMS MAGAZINE
57
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