IEEE Circuits and Systems Magazine - Q1 2022 - 44

relatively low complexity and low cost; however, it is hard
to realize localization and multi-object detection. FMCW
radar and UWB radar demonstrate excellent capabilities
for localization, Doppler detection on macro-movements,
and accurate sensing on tiny motions. UWB transceivers
need to operate under the FCC mask. This survey will focus
on integrated wideband RF transceiver techniques for
FMCW multimodal radar sensing, as well as efficient UWB
communications and sensing for IoE applications.
B. Wideband RF Transceiver System Analysis for
Radar Sensing Applications
For integrated wideband RF transceiver design for radar
applications, the link budget analysis is usually implemented
firstly to estimate the circuit design parameters based
on the specific sensing scenario. Based on the radar theory
[79]-[81], the power of the echoed signal is expressed as
P
P
where PT
and PR
T
R
=
GG
4
r
TRmv
34
2
^h RLs
,
the echoed power by the antenna. GT
(1)
represent the transmitted power and
and GR
the transmitter and receiver antenna gains. Ls
mented by the mixer on-chip, which can be evaluated
as (/ ).
10 log BWB The power of the de-chirped signal PD
can be expressed as [81]
PP GG GDe
The PD
DR FE=+ ++ IF
.
based on the tunable RF frontend GFE
amplifier GIF
(3)
usually needs to be amplified to around 0 dBm
and the IF buffer
for further digital signal processing [81], [88].
III. Integrated FMCW Radar Sensor for
Versatile Sensing and Imaging
represent
accounts
for the total system loss. v is the radar cross-section. R
represents the one-sided range between the radar and the
target. The term m stands for the center wavelength of the
transmitted signal [81]. The received power PR
It is promising to leverage integrated wideband RF
transceivers to achieve precise localization, energyefficient
communications, and pervasive multimodal
sensing applications. The wideband radar sensors, including
UWB radar and FMCW radar, can be compatible
with existing communication standards. Therefore,
accurate radar sensing and efficient communications
are expected to be realized based on ultra-compact integrated
wideband RF transceivers operating in accordance
with FCC standards.
With the significant progress of semiconductor techis
estimated
based on (1). The receiver's noise figure is represented
as the term NF. The thermal noise floor is estimated as [81]
PB (2)
n =- ++dBm NF
17410log10 (),
where B represents the bandwidth. The term GDe
resents the compression gain of the de-chirping implerepTable
I.
Comparison of Different Radar Sensors.
Feature
Localization
Frequency
Multi-Object
Detection
Tiny Motion
Detection
Through Wall
Detection
System
Complexity
Cost
44
FMCW
Excellent
Flexible
Yes
Excellent
Yes
Medium to
High
Medium to
High
IEEE CIRCUITS AND SYSTEMS MAGAZINE
UWB Pulse
Excellent
FCC mask
Yes
Excellent
Yes
Medium to
High
Medium to
High
SingleTone
CW
Hard
Flexible
Hard
Excellent
Yes
Low
Low
niques, essential electronic components of radar can
be realized in chip scale with a high level of integration
[32]-[73], [78]-[89], [138]. The highly integrated radar
sensors can be deployed in the ceilings, walls, or corners
in various scenarios in large quantities with ultracompact
size and low cost [68]. FMCW radar sensors
have demonstrated their promising capabilities for
versatile sensing and imaging. The FMCW radar sensors
are deployed for synthetic aperture radar (SAR)
imaging, localization, as well as specific gesture or motion
recognition. Moreover, integrated FMCW radar sensors
can be deployed to realize multimode vital signs
monitoring and accurate detection of falls for pervasive
IoE healthcare. It is promising to leverage beamforming
to focus the beams on the subjects with wide FoV
coverage and improved SNR. Noncontact radar sensing
devices and radar signal processing algorithms
are optimized jointly to support precise health status
monitoring, precise localization, and efficient communications
[19], [31], [32], [79]-[81], [92], [93], [95]-[99].
Besides, the wideband chirped signal demonstrates excellent
characteristic on detecting tiny motions caused
by vital signs with high resolution. A phased-array
chirp-based integrated radar sensor can operate with
a compact size and relatively low power consumption.
Moreover, it can support sensing in a wide coverage
range with sufficient steering step precision [79]-[81].
Based on phased-array FMCW transceiver architecture,
wide FoV radar sensing with a fine steering step can be
realized [79], [81].
FIRST QUARTER 2022
IEEE Circuits and Systems Magazine - Q1 2022

Table of Contents for the Digital Edition of IEEE Circuits and Systems Magazine - Q1 2022
