1. An Ultra Low-Power Dual-Band IR UWB
Transmitter
Nikhilesh V. Bhagat
Department of Electrical and Computer Engineering
San Diego State University
San Diego, CA, 92182, U.S.A.
Email: bhagatnikhilesh@gmail.com
I. INTRODUCTION
There are two possible techniques for implementing UWB
communication are Impulse Radio (IR) and multicarrier UWB.
UWB-IR is based on transmitting ultra-short (in the order of
nanosecond) pulses. Multi-carrier or multi-band UWB (MB-
UWB) systems use orthogonal frequency division multiplexing
(OFDM) techniques to transmit the information on each of the
sub-bands. Up and down conversion is required and it is very
sensitive to frequency, clock, and phase inaccuracy. On the
other hand, nonlinear amplification destroys the orthogonality
of OFDM. With these drawbacks MB-UWB is not suitable for
low-power and low cost application. UWB-IR offers several
nice advantages. It allows unlicensed usage of several giga-
hertz of spectrum. It also offers great flexibility of spectrum
usage. Adaptive transceiver design can be used for optimizing
system performance as a function of the data rate, operation
range, available power, demanded quality of service, and user
preference. Gb/s data-rate transmission over very short range is
possible. Because of ultra short pulses used in UWB, it is very
robust against multipath, and more multipath components can
be resolved at the receiver, resulting in higher performance.
Due to the ultra-short duration pulses sub-centimeter ranging
is possible. In UWB-IR no up and down conversion is required
therefore it reduces the implementation cost, and low- power
transmitter implementation is possible. Because of the short
pulses and low power transmission, it is very hard to eavesdrop
the UWB signal issues which need to be considered. The
frequency bands of 0-960 MHz and 3.1-10.6 GHz are allocated
for the unlicensed ultrawideband (UWB) applications with
a spectral mask limitation of 41.3 dBm/MHz. The 0-960-
MHz band is available for ground radar and through-the-wall
imaging applications. Because the 56-GHz band is utilized for
the wireless-localarea- network systems, conventional UWB
systems have been recently allowed to operate in two bands,
i.e., 3.15 GHz and 610.6 GHz [2].With the emergence of
a large variety of UWB applications, the transmitter, and
particularly the transmitted pulse design, has become an active
research area within the UWB literature and the references
therein for a thorough review). For this reason, in this brief,
we consider a power-efficient UWB transmitter design and
propose a dual-band ultra low-power UWB transmitter archi-
tecture that is capable of pulse transmission in both the lower
0960-MHz and the upper 3.15-GHz bands. The pulse orders
differ for best coverage of these bands. The best coverage of
the 0960-MHz band is achieved by the Gaussian monocycle,
whereas there is a need for a much higher order pulse for
the 3.15-GHz band. Thus, an external bandpass filter (BPF)
is used to generate the higher order pulse. Pulse generation
in the proposed UWB transmitter utilizes the pulse-shaping
architecture. In this approach, higher order UWB pulses are
obtained by filtering the output of a Gaussian monopulse
using a BPF. This method contains a smaller number of
components and thus consumes less power than its counter-
parts such as pulse-combining and oscillator-aided approaches.
The transmitter architecture and its circuitry are explained in
Section II. The measurement results are presented in Section
III, followed by the performance comparisons with existing
low-power architectures in Section IV. This brief ends with
discussions and conclusive remarks in Section V.
II. TRANSMITTER DESIGN
A detailed block diagram of the entire circuit diagram is
shown in Fig. 1:
Fig. 1. The circuit diagram of Transmitter.
The Pulse generator, Glitch generator and Pulse shaper form
the basic components to generate the Guassian monocyclic

2. pulse. Information in impulse UWB techniques is send by
modulating short pulses. There are several modulation options
which depend on application, design specifications and con-
straints, operation rage, transmission and reception power con-
sumption, quality-of- service, regularity, hardware complexity,
data rate, and capacity. Some of known modulation options
in UWB-IR are Binary Phase Shift Keying (BPSK), Pulse
Amplitude Modulation (PAM), On-Off Keying (OOK), and
Pulse Position Modulation (PPM). In this design, we use the
simplest of all modulators, i.e On-Off keying modulator. It
consists of the Nand gates and Inverters. Fig. 2:
Fig. 2. The circuit diagram of On-Off Keying Modulator.
Two identical glitch generators (GGs) are shown in Fig.
3:, labeled as GGA and GGB, are designed to generate
monocycles at the rising edge of the modulated signal. The
GG consists of a combiner and an OOK modulator. The input
signal is applied to PMOSFET of GGA, and one input of the
modulator. The output of the GG is fed back to the input of the
combiner through an NMOSFET. The combined output signal
VXA is applied to the other input of the modulator. During
this transition, a short monocycle pulse is formed.
Fig. 3. The circuit diagram of Glitch Generator.
The GGA output is inverted and applied to PMOSFET
of the output pulse shaper; as a result, the pulse-generator
output becomes VDD. The output signal of GGB (which is
identical to GGA) is delayed using a four-stage inverter chain
and applied to NMOSFET that drives the output voltage to 0
V. The output pulse shaper stage transistor sizes have to be
selected carefully for correct pulse shape. Fig. 4:
Fig. 4. The circuit diagram of Pulse Shaper.
The transmitter output is then applied to the package and
off-chip printed circuit board (PCB) through a wire bond
that can be simplified as an equivalent 5-nH inductance Lwb
and 50-uF series capacitance Cps. A 3.15-GHz-band BPF is
realized using an additional off-chip BPF. Gaussian and higher
order UWB pulses are obtained before and after the BPF.
III. MEASUREMENT RESULTS
Here, the VDD is set to 5 V, and a 5-nF pulse-shaping
capacitor is selected. A Gaussian monocycle of 1.17-ns width

3. is measured. The peak-to-peak voltage is 290 mV. The output
waveforms for On-Off keying modulator, Pulse generator are
shown in Fig. 5:
Fig. 5. The output waveforms.
The Guassian monocycle pulse shown in Fig. 6:
Fig. 6. The monocycle pulse.
IV. CHALLENGES
The circuit diagram in the project as such is fairly simple
to implement. The main task is to understand the working
and the concept of IR-UWB. Also, the pulse shaper and the
analog circuit at the end needs to be designed precisely to
get a clear pulse. The transistor need to be sized accordingly.
Most of the times the trail and error method for the analog
components will give approximately correct output.
V. CONCLUSION
A low-power IR-UWB transmitter operating in 0960-MHz
band has been presented. The transmitter employs a simple
pulse generation and shaping architecture, which lead to
energy-efficient operation.