IEEE Circuits and Systems Magazine - Q1 2021 - 47

Table 3.
Comparison of power consumption of several state-of-the-art radars.
[16]

[4]

[18]

[19]

[17]

Freq (GHz)

6.8-8.2

7.2-8.5

2-5

10

15

VDD (V)

1/1.1

1.8

1.9

1.2

1.2

Chip content

ADC, LPF, HPF,
PA, DCO,
LNA/mixer

OSC, PLLs, PMU,
DAC preamp, LNA
comparators, HPF,
digital backend
and control logic

Switch, LNA, buffer,
S&H circ, T&H, integrator,
VGA, pulse gener. timing
circu, power splitter,
output buff.

4ch RX RFFEs,
4 ch RXBBs, SPI,
DLL MPS, DDSs,
PLLs, PSs, PAs

ADC, VGA, BPF,
Rx RFFE, DA-PA,
chirp synthesizer
and DSP
reservation

Peak DC power

19mW

N/A

N/A

141 mW/ch

148 mW

DC power during
active detection

0.68mW

118 mW

695 mW

141 mW/ch

148 mW

Table abbreviations:
ADC: analogue to digital converter, LPF: low pass filter, HPF: high pass filter, LNA: low noise amplifier, DCO: digitally controlled oscillator, PA: power amplifier,
OSC: oscillator, PLL: phased locked loop, PMU: power management unit, DAC: digital to analog converter, T & H: track and hold amplifiers, S & H: sample and
hold block, VGA: variable gain amplifier, 4ch RX RFFE: 4 channels receiver RF front end block, 4ch RXBBs: 4channels receiver baseband block, SPI: serial
peripheral interphase, DLL MPS: delay locked loop based on multiphase synthesizer, DDS: direct digital synthesizer, PS: phase shifter, BPF: bandpass filter,
DA-PA: driver amplifier-power amplifier, DSP: digital signal processing.

leakage power leakage from the QC and the stationary
background reflection clutter. Experimental assessments for the detection of human vital signs at 75 cm
was demonstrated, with the heartbeat and respiration
signals clearly observed. Meanwhile, the thesis in [8]
introduces a unique architecture based on multidimensional signal processing for directional sensing and remote localization. This architecture integrates CW Doppler radar with array signal processing based on 2-D
Infinite Impulse Response (IIR) Spatial Band Pass (SBP)
digital filters. The proposed architecture consists of a
wideband omnidirectional Uniform Linear Array (ULA)
consisting of 64 receiver antennas. It spatially samples
the reflected RF waves with each antenna having its
own RF front end. Each front end consists of an LNA,
band pass filter (BPF), gain amplifier (GA), and phase
shifter (PS) to generate the in-phase and quadrature
components. These signals are then down converted
to baseband using mixers which multiply the output
of the PS with a copy of the transmitted signal. This
copy is generated using a voltage-controlled oscillator (VCO) and 65-way splitter. This step is followed
by baseband amplification and low pass filtering. The
baseband signals are then down sampled using dedicated down-sampling ADCs at each antenna. After that,
the signals are digitally processed using 2-D IIR SBP
beamformer to provide information of the surrounding targets. Although the main application of this work
is in micro unmanned aerial system (UAS) detection
and automated cyber physical system (CPS), the radar
signal extraction methods can be applied to vital sign
signal extraction.
FIRST QUARTER 2021

Next, in [20], a CW radar and its corresponding processing techniques are used to detect cardiopulmonary
activities of human body. Detection is performed at several body positions and scenarios. Meanwhile, a human
sensing application radar is presented in [21] using a
CW Doppler radar. The CW radar generates a 3 GHz CW
signal which is then amplified through a power amplifier before being transmitted via a Vivaldi antenna. In
the receiver side, the received signal is amplified by an
LNA. The CW radar utilizes a super-heterodyne receiver
to eliminate out-of-band noise and nonlinear distortions by converting the received signal into intermediate frequency (IF) signals, followed by the application
of a BPF. Next, the IF signal is digitized, and the sampled
data is sent to the FPGA-based digital downconverter.
The structure of the CW radar is shown in Figure 3. Note
that the architecture of the super-heterodyne receiver
is more complex compared to the radar architecture
shown in Figure 5, which enables direct mixing of the
Table 4.
Radar types for vital sign detection.
Radar Type

Reference

CW

[1], [3], [8], [20], [21], [22], [23], [24], [25],
[26], [27], [28], [29], [30], [31], [32], [33],
[34], [35]

UWB-IR

[2], [10], [21], [36], [37], [38], [39], [4],
[40], [41], [42], [43], [44], [45], [46], [47],
[48], [49], [50]

FMCW

[8], [7], [51], [52], [53], [54], [109],

SFCW

[2], [9],[55], [56], [57] [58]
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