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Graduate Research
An 8-psec 13dBm Peak EIRP Digital-to-Impulse Radiator
with an On-chip Slot Bow-Tie Antenna in Silicon
Mahdi Assefzadeh, Aydin Babakhani
(mahdi, aydin.babakhani)@rice.edu
Rice Integrated Systems
and Circuits (RISC)
Design
Introduction
There is a considerable interest in radiating ultra-short
broadband pulses in mm-wave and THz regime for
applications in 3D imaging, spectroscopy, and high-speed
wireless communication. Unfortunately, the pulse width of
the prior silicon-based radiators is not short enough and
their bandwidth is limited. In contrast with the prior art,
where a CW oscillator was modulated to generate narrow
pulses, in this work, no oscillator was used. Instead, a
direct digital-to-impulse converter with a broadband on-chip
antenna are implemented that generate and radiate
coherent impulses with duration of 8psec, peak EIRP of
13dBm, and a repetition rate up of more than 10GHz. The
radiated impulses can be locked to a digital trigger with
timing jitter of better than 270fsec. This low level of timing
jitter of the circuit makes it possible to build a coherent
sparse array of widely-spaced impulse-radiating chips.
Architecture
Current
Switch
Digital
Trigger
The design of the impulse radiator is based on the switching
of the current of an antenna structure. Having a high current
passing through a structure and by turning that current off,
the chip radiates impulses. The antenna used in this work a
slot bow-tie antenna. There is a pulse matching network
between the switching transistors and the antenna structure
for maximizing the bandwidth and the power of radiation.
Digital
Buffers
Pulse
Matching
Antenna
Structure
T0: Pulse Repetition Period
PA
tr: Digital Trigger Rise Time
Radiated
Signal
PW: Radiated Pulse Width
T0
T0
VCC
t
t
tr
9x0.6pF
PW
TLine – Cap
Pulse Matching
V2
0.3pF
10x0.1pF
VDD
10x70fF
0.3pF
Digital
Trigger
V3
8x70fF
10x0.1pF
4x5μm
Q1
V1
4x18μm
10x0.1pF
Q3
360μm
10x0.1pF
4x18μm
Q2
Equivalent
Circuit of
Antenna
Fast Switch
Pulse
Matching
A
B
Radiated Signals
Without Pulse Matching
Coherent Combining
Measurement Results
8ps
50%-50%
θ=10°
θ=0°
θ=20°
θ=30°
θ=40°
Time Domain Radiation Pattern
θ: E-Plane Degree
The precision synchronization of the
digital trigger with the radiated
impulses makes it possible to build a
coherent sparse array with widelyspaced antennas to increase the
effective
aperture
size.
To
demonstrate a coherent array, the
radiated impulses from two separate
chips are combined in the far-field.
With Pulse Matching
Conclusion
The reported digital-to-impulse radiating chip is fabricated
in a 0.13µm SiGe BiCMOS process technology with ft =
200GHz and fmax=270GHz. A micrograph of the chip is
shown in figure below. The size of the chip including the
on-chip antenna and the pads, is 0.55mm×0.85mm.
850µm
TLine-Cap Array
50%-50%
6ps
PA
Matching
550µm
Slot Bow-tie
Antenna
0
Digital
Buffers
Current
Switch
Radiation Pattern At 70GHz
Teraview’s THz-TD Spectrometer
Single-Chip Picosecond Impulse Emitter
850µm
TLine-Cap Array
Matching
550µm
PA
Slot Bow-tie
Antenna
Current
Switch
300,000X
Cost: $300K
20,000X
H-Plane
E-Plane
Weight: 200kg
2,000X
Largest dimension: 2m
1,000X
Average radiated power: μW
Pulse Width: 1psec
Measured Directivity: 15dBi
Remaining Challenge
Digital
Buffers
Cost: $1
Weight: 0.01kg
Largest dimension: 1mm
Average radiated power: mW
Pulse Width: 8psec