System-on-a-Chip UWB Radar Sensor for Contactless Respiratory Monitoring: Technology and Applications - Ultra-Wideband and 60 GHz Communications for Biomedical Applications - page 69

over the last years as the predominant technology of the microelectronics industry
[ 7 ]. Device scaling results in consistent improvements of the device density and
performance, enabling the System-on-a-Chip (SoC) implementation of highly minia-
turized and low-cost sensors. Therefore, in addition to the performance requirements,
the physical cointegration of radar microchip and antennas has to also consider the
manufacturing costs during the design phase [ 8 , 9 ].
One of the main technical challenges for the SoC CMOS implementation of
UWB radars is related with the on-chip generation of extremely short (few hundred
picoseconds) radio-frequency pulses with large amplitude and high energy efficiency
[ 10 ]. Thanks to the successful implementation of the most critical building blocks
[ 11 , 12 ], our research group recently presented the first implementation, including
experimental evidence and compliance to FCC UWB spectrum mask, of a SoC
UWB pulse radar based on a correlation receiver, in 90 nm CMOS technology by
STMicroelectronics [ 13 , 14 ]. In particular, the work reported by Zito et al. [ 13 ]
focuses on the technical aspects regarding the SoC implementation of the radar
microchip in 90 nm bulk CMOS technology, whereas the work reported by Zito et al.
[ 14 ] focuses on the extension of the field operational tests for contactless detection
of respiratory rate in adults and infants. In the following sections we report the key
aspects and main results of this on-going research carried out by our group.
System-on-a-Chip Complementary Metal-Oxide Semiconductor
Ultra-Wideband Pulse Radar Sensor
Pulse radars operate by sending short electromagnetic pulses, and by receiving the
echoes reflected by the target. The time delay between the transmitted and received
pulses is proportional to the distance from the target to the radar. Examples of pulse
radars for the detection of vital parameters implemented in hybrid-form circuits by
means of discrete components are reported in literature [ 15 , 16 ]. In this section we
report the key aspects of the design of the first implementation, including experimen-
tal evidence and FCC UWB mask compliance, of the SoC UWB pulse radar based
on a correlation receiver, in 90 nm CMOS technology by STMicroelectronics [ 13 ].
In detail, the principle of operation is highlighted in section “Operating Principle”.
The design of the building blocks and their experimental results are summarized in
section “Building Blocks”. The SoC UWB radar in 90 nm CMOS technology and
the results of the experimental characterization of the radar sensor are reported in
section “SoC UWB Pulse Radar”.
Operating Principle
The block diagram of the UWB radar sensor is shown in Fig. 1 a. The receiver
is based on a correlation topology. The operating principle of this radar can be