Ultra Wide-Band Technology (UWB) is a short-range, high-bandwidth communications technology that can be used for data transfer, imaging, and localization applications. UWB operates by transmitting very short pulses across a wide frequency band with low power. Key applications of UWB include high-speed wireless communications and high-resolution radar and imaging systems. Standardization efforts have developed standards for UWB personal area networks, and UWB offers advantages like high data rates and secure transmission, but also faces limitations from its low-power emissions.
2. Contents
Introduction to UWB
Narrowband, Wideband, and Ultra-Wideband
UWB Signal
Single Band and a Multi Band
UWB Modulation Schemes
Transceiver Architecture
UWB antennas
UWB-MIMO
Applications
Standardization
Advantages - Limitations
3. Ultra Wide Band (UWB)
Ultra Wide Band (UWB) is a technology for the transmission data by using techniques which cause a spreading of
the radio energy over a very wide frequency band.
with a very low power spectral density. The low power spectral density limits the interference potential with
conventional radio systems (TV, GSM, UMTS, GPS, etc.).
and the high bandwidth can allow very high data throughput for communications devices, or high precision for
location and imaging devices.
UWB radios can use frequencies from 3.1 GHz to 10.6 GHz in USA and Asia and at least 6.0 to 8.5 GHz in Europe.
The Federal Communications Commission in USA (FCC) has defined an UWB device as any device with a –10 dB
fractional bandwidth, greater than 20% or occupying at least 500 MHz of the spectrum
Most narrowband systems occupy less than 10% of the center frequency bandwidth, and are transmitted at far
greater power levels.
the FCC introduced severe broadcast power restrictions for UWB in order not interference other narrower band
systems nearby, such as 802.11a/g radio.
4. Narrowband, Wideband, and Ultra-Wideband
We can classify signal as Narrowband, Wideband, and Ultra-wideband by Fractional bandwidth and is defined by
the ratio of bandwidth at –10 dB points to center frequency or The fractional bandwidth is defined as the radio of
signal bandwidth to the center frequency.
The –10 dB point represents the spectral power of a signal at 10 dB lower than its peak power.
𝑩 𝒇 = 𝟐
𝒇 𝒉−𝒇 𝒍
𝒇 𝒉+𝒇 𝒍
× 𝟏𝟎𝟎% Narrowband 𝑩 𝒇 < 1%
Wideband 1% < 𝑩 𝒇 < 20%
Ultra-Wideband 𝑩 𝒇 > 20%
5. UWB-Signal
𝑇𝑜𝑛represents the time that the pulse exists and
𝑇𝑜𝑓𝑓represents the time that the pulse is absent.
And duty cycle is the ratio of the time that a pulse is present to the total transmission time.
𝐷𝑢𝑡𝑦 𝐶𝑦𝑐𝑙𝑒 =
𝑇𝑜𝑛
𝑇𝑜𝑛 + 𝑇𝑜𝑓𝑓
UWB systems use carrier less, short-duration (picosecond to nanosecond) pulses with a very low duty cycle (less than 0.5
percent) for transmission and reception of the information.
Low duty cycle offers a very low average transmission
power in UWB communications systems. The average
transmission power of a UWB system is on the order of
microwatts.
the short-duration UWB pulses spread their energy across a
wide range of frequencies—from near DC to several
gigahertz (GHz)—with very low power spectral density
(PSD) in in the frequency domain
6. UWB-Signal
Impulse-radio (IR) UWB ,first systems were that utilized the concept of wideband communication in power limited system.
IR UWB offers short duration pulses with fast rise and fall times, which results in wideband spectra.
For example, a pulse signal which is centered at 6 GHz and occupies a bandwidth of more than 1.2 GHz (i.e. 20% fractional
bandwidth).
These pulses are having very low energy because very low power level is permitted to UWB transmission. to carry the
information of one bit many such pulses are combined.
The IR-UWB transceiver system has advantage of simplicity and low cost.
A UWB signal can be any one of a variety of wideband signals, such as Gaussian, chirp, wavelet, or Hermite-based short-
duration pulses.
Typical pluses Gaussian monocycle, and these pluses the first derivative of a Gaussian pulse and is given by:
𝑃 𝑡 =
𝑡
𝜏
𝑒−(
𝑡
𝜏)2
where represents 𝒕 time and 𝝉 is a time decay constant that determines the temporal width of the pulse
7. In Figure above 500-picosecond pulse generates a large bandwidth in the frequency domain with a center frequency
of 2 GHz.
the lowest and highest cutoff frequencies at –10 dB are approximately 1.2 GHz and 2.8 GHz, respectively, which lead
to a fractional bandwidth of 80 percent; this is much larger than the minimum required by the FCC:
𝑩 𝒇 = 𝟐
𝟐.𝟖−𝟏.𝟐
𝟐.𝟖+𝟏.𝟐
× 𝟏𝟎𝟎% = 𝟖𝟎%
8. Single Band and Multi Band
The Single Band (Direct-Sequence UWB (DS-UWB)) :
supports the idea of impulse radio that is the original
approach to UWB by using narrow pulses that occupy a
large portion of the spectrum.
The Multi Band OFDM(MB-OFDM) approach
divides the available UWB frequency spectrum
(3.1 GHz to 10.6 GHz) into multiple smaller and no
overlapping bands with bandwidths greater than
500 MHz .
Direct-sequence UWB is a single-band approach that uses
narrow UWB pulses and time-domain signal processing
combined with DSSS techniques to transmit and receive
information.
The DS-UWB technique is scalable and can achieve data
rates in excess of 1 Gbps.
This approach is similar to the narrowband
frequency-hopping technique.
offers the advantage of avoiding transmission over
certain bands.
9. UWB Modulation Methods
The modulation methods used in UWB systems are :
Pulse Position Modulation (PPM)
On-Off Keying modulation (OOK)
Pulse Amplitude Modulation (PAM)
Pulse Width Modulation (PWM)
10. Pulse Position Modulation (PPM) : When the transmitted bit is 0,
pulse does not shift. When bit is 1, pulse shift a specific amount
δ, where δ is called modulation index.
On-Off Keying modulation (OOK): When the transmitted bit is 1,
a pulse is transmitted. When the bit is 0, no pulse is transmitted.
UWB Modulation Methods
11. UWB Modulation Methods
Pulse Amplitude Modulation (PAM) : When the transmitted
bit is 1, a positive pulse is transmitted. When the bit is 0, a
negative pulse is transmitted.
Pulse Width Modulation (PWM) : When the transmitted bit
is 1, a wide pulse is transmitted. When the bit is 0, a narrow
pulse is transmitted.
12. Transceiver Architecture
UWB transmission is carrier less, meaning that data is not modulated on a continuous waveform
with a specific carrier frequency, as in narrowband and wideband technologies.
Carrier less transmission requires fewer RF components than carrier based transmission.
The UWB transceiver architecture is considerably less complicated than that of the narrowband transceiver.
The transmission of low-powered pulses eliminates the need for a power amplifier
13. There are Several Classes Of Transceivers ,
The Coherent Transceivers:
On the transmitter side, the pulse generator has to control the transmitted pulse shape
finely and is generally able to handle its polarity.
On the other side, the receiver is able to estimate the composite channel impulse
response.
This estimation is then used as a comparison pattern to demodulate the received signal
and all modulation schemes can be used.
Correct operation of the transceiver is ensured by a good quality time base on both the
transmitter and receiver sides.
14. The Non-coherent Transceivers
It is generally less efficient but more attractive if cost or power consumption
Signal detection is based on energy detection performed on the incoming signal.
Time base requirements are generally relaxed, allowing the use of low cost oscillators.
Differentially Coherent Transceivers
On the transmit side, a differential modulation scheme is used in order to resolve the resulting bit ambiguity.
On the receiver to keep a delayed version of the incoming signal and use it as reference to be compared with
the current signal.
15. UWB Antenna
The antenna acts as a filter for the generated UWB signal, and only allows those signal components that radiate to
be passed.
UWB antennas differ from their narrowband antennas in one basic concept.
In narrowband antennas tuned to particular center frequencies and have relatively narrow bandwidths.
In contrast, UWB antenna designs seek much broader bandwidths and require no resonating operation.
UWB antennas should be linear in phase and should have
a fixed phase center.
The antenna gain should be smooth across the frequency
band in order to avoid dispersion of the transmitted
pulse.
16. The Ringing Effect
The Ringing Effect : after the UWB antenna deform the transmitted signal . the antenna response to a plus
of very short duration, as is typical in UWB , is seen as ripple after the plus . this effect is consequence of
the antenna geometry and translates into a frequency dispersion or time delay, which reduces the
transmission speed.
To avoid ringing, resistive antennas with low Q-values should be
used. The resistive loading will cause the unwanted signal
component to die away quickly, leaving a pulse much closer to the
desired shape.
𝑄 =
𝑓𝑜
𝑓𝐻 − 𝑓𝐿
where 𝑓𝑜, 𝑓𝐻, and 𝑓𝐿 are the center frequency and the upper and lower
The antenna bandwidth can also be increased by making the Q-
value small.
the low Q-value implies that the efficiency of a resistive antenna is
generally quite poor.
17. UWB Antenna
There are three types of antenna used with UWB:
Base Station Antenna
Its used for networks such as high speed data or for low data-rate systems, including location and tracking systems.
The base station antenna may be designed for indoor or outdoor the application.
Base station antennas may be either directive or omnidirectional. Directional antennas(radio links) , or
omnidirectional antennas (mobile applications).
Portable Antenna :
the antenna is small and low cost .
the antenna is omnidirectional. And its can be constructed on a printed circuit board
Antenna Arrays
In UWB radar applications, linear and planar antenna arrays may be formed with very sparsely spaced
elements.
high resolution phased array antennas, with a beam which may be readily steered.
The ratio of the wideband peak side lobe level to the peak main lobe level is a function of the number
of antenna elements rather than the element spacing.
18. There are several antenna topologies or types that are using in UWB such as horn antenna ,
Biconical antenna ,Helix antenna ,Bowtie antenna ,spiral antenna.
Antenna Topologies Out-Door
Applications
In-Door Applications
Vivaldi antenna suitable Not-suitable
1.has a directional radiation pattern.
log periodic and spiral Antennas
Operate in the 3.1-10.6 GHz
suitable Not Recommended,
1. hey have large physical dimensions.
2. severe ringing effect.
planar or printed monopole antenna N/A Suitable.
19. Vivaldi antenna Spiral and conical spiral antenna
Log-periodic antenna
Mono-conical and bi-conical antenna
20. UWB-MIMO
We can using MIMO together with UWB helps in extending the communication range as well as
offers higher link reliability. The benefits of UWB-MIMO can be summarized as following:
1. interference mitigation/suppression,
2. higher data rates,
3. improved link quality
4. extended coverage,
5. reduced analog hardware requirements, and concurrent localization.
And design specifications for UWB-MIMO antenna :
21. UWB Applications
Communications Devices.
Imaging Devices.
Vehicular Radar Systems.
For communications devices, the FCC has assigned different emission limits for indoor and outdoor UWB
devices. The spectral mask for outdoor devices is 10 dB lower than that for indoor devices, between
1.61 GHz and 3.1 GHz.
Vehicular radar systems are allowed to emit –41.3 dBm/MHz only in them 22 GHz to 29 GHz frequency
range. The center frequency of their signal should be higher than 24.075 GHz.
22. Communications Devices
The high-data-rate capability of UWB systems for short distances has numerous applications for home
networking and multimedia-rich communications in the form of WPAN applications. UWB systems could
replace cables connecting camcorders and VCRs, as well as other consumer electronics applications, such as
laptops, DVDs, digital cameras, and portable HDTV monitors. No other available wireless technologies—
such as Bluetooth or 802.11a/b—are capable of transferring streaming video.
23. Radar Systems.
Radar is considered one of the most powerful applications of UWB technology. The fine positioning
characteristics of narrow UWB pulses enables them to offer high-resolution radar (within centimeters) for
military and civilian applications. Also, because of the very wide frequency spectrum band, UWB signals can
easily penetrate various obstacles. This property makes UWB-based ground-penetrating radar (GPR) a useful
asset for rescue and disaster recovery teams for detecting survivors buried under rubble in disaster
situations.
24. Summarizes UWB applications in data communications, radar, and localization.
25. Standardization
Wireless Personal Area Networks using UWB as PHY options
IEEE standard of 802.15.3a for high data rate
DS-UWB vs. MB-OFDM-UWB
Proposal with drawn on Jan 2006
IEEE standard of 802.15.4a for low data rate
Communications
High precision ranging and location
26. Advantages - Limitations
Advantages
UWB technology has very high potential in real life applications, due to its high bandwidth
and low power.
Very interesting application in wireless content transfer, especially for HD videos.
Secure transmission, low probability of interception or detection and anti-jam immunity.
Limitations
Emissions below conventional level.
Not appropriate for a WAN (Wide Area Network) deployment such as
wireless broadband access.
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