Generation of Ultra-Wide-Band Pulse Signal

IRJMST Volume 5 Issue 1 Online ISSN 2250 - 1959

International Research Journal of Management Science & Technology http:www.irjmst.com Page 263

Generation of Ultra-Wide-Band Pulse Signal

Vikash kumar1

Dr. Hari sumiran Singh2 1Research Scholar Faculty of Science(Electronics)

Magadh University

Shiv-Mani Sadan Purvi Rupaspur

Sahay nagar Patna-801506

[email protected] 2Assosiate Profesor J.D.W. CollegeBaily Road

Patna-800023

[email protected]

Abstract –Ultra-wideband (UWB) communication techniques have attracted a great

interest in both academia and industry in the past few years for applications in short-

range wireless mobile systems. This is due to the potential advantages of UWB

transmissions such as low power, high rate, immunity to multi-path propagation, less

complex transceiver hardware, and low interference. However, tremendous R&D efforts

are required to face various technical challenges in developing UWB wireless systems,

including UWB channel characterization, transceiver design, coexistence and inter

working with other narrowband wireless systems, design of the link and network layers to

benefit from UWB transmission characteristics.A method for generating sub nano second

pulse signals with time-jitter as low as 100 ps was described and theoreticaly analyzed.

Keywords—ultra wide band(UWB), Gaussian pulse

I. INTRODUCTION

Ultra-Wide-Band (UWB) wireless technology became in recent years one of very promising

technologies after recognition of their commercial potential [1]. World wide interest in UWB

wireless increased greatly after year 2002, when US Federal Communication Comission (FCC)

gave first authorization for it. In INDIA the National Frequency Allocation Plan 2011 (NFAP-

2011) has the following provision for UWB IND73 “Use of Ultra Wide Band (UWB) equipment

may be considered in the frequency band6.0–7.25 GHz with maximum (Equivalent Isotropic

Radiated Power) EIRP density of -41 dBm/MHz in any 1MHz bandwidth with maximum 500

MHz on non exclusive and non protection basis.” Other names for this techniques are somewhere

in use: impulse communications, impulse radio, subnanosecond communications, as well as

carrier-free , nonsinusoidal communications etc.[2]

How UWB Works:

mailto:[email protected]

mailto:[email protected]


International Research Journal of Management Science & Technology http:www.irjmst.com 64

Since the capacity of a communications channel in a non-fading environment is expressed as:

C = B * log2 (1+S/N)

Where

C = channel capacity (bit/s)

B = channel bandwidth „BW‟ (Hz)

S = signal power (watts)

N = noise power (watts)

According to above equation, the capacity can be

increased by either increasing B or S/N. It is obvious

that the capacity can be increased more by increasing

B rather than S/N.

UWB systems could also suffer from interference from other wireless technologies that

exist in the vicinity of operation, but this problem can be mitigated by using adaptive selection of

frequency bands in multi band UWB systems.

According to actual FCC statement, UWB is any signal that occupies at least of 500 MHz of

bandwidth in the spectrum range between 3.1 and 10.6 GHz. Because this technology is

developping very fast we could expect some changes in the regulation area. In the practice,

signals covering the spectrum range from 1to5 GHz and higher are considered as UWB also.

Additional requirement is that the fractional bandwidth, defined as

LH

LH

ff

ffFB 2

(1)

is higher than 0.25, where: fH is the upper and fL lower frequency limits, which define frequency

range containing dominant part of total signal energy. It is evident that this definition avoids

requirement for definition of the center frequency. In practice it is often defined by the relation

2

LHC

fff

(2)

Speaking in the time-domaine, UWB technique involves transmitting, receiving and processing

of stream of low power (in the region of microwatts), very short pulses in the order of 10

picoseconds to 1000 picoseconds.[3]



UWB signal has usualy the shape the Gaussian monocycle (Fig. 1.), sinusoidal monocycle or

"bunch" of few sinusoidals.We consider two important technologies, which are under intensive

development: UWB communications and pulse radar rnging, imaging and sensing systems. In

communications systems the main issue is how to optimaly transfer voice, video nad data

informations. Most used method to carry the information is the pulse time-modulation, which,

however, poses strong requirements on UWB pulse timing-jitter (Fig. 2.).

Fig. 1a-Gaussian monocycle

Fig. 1b. Frequency spectrum of Gaussian monocycle

Mostly considered types of modulations are: pulse position modulation, pulse amplitude modulation, on-

of-keying and bi-phase-shift keying modulations, as well as pseudo-random and chaotic modulations.

Special attention has been payed last years to apply chaos theory and practice in UWB communication

technology.

Pseudo-random (Fig. 3.) and chaotic time modulation are similar in some way. These are both very

robust regarding signal interception and detection, because they "smoothes" the frequency spectrum and

make it appear as a pure "white noise", as it can be seen comparing spectra on Fig. 2b. and Fig. 3b. This

enables more secure communication and makes have virtually unlimited number of channels.

In estimating UWB technology one has to compare its advantages and draw-backs.[4]

There are many important advantages of UWB techniques;

(1) In data communication applications the system is working with modulated subnanosecond pulse

trains having duty-cycle of less than 10 %. As a result we can deal with broad, noise-like frequency

spectrum, having very low average power, capable to work in noisy and crowded environment. The well

designed system shows high degree of interference resistivity, becuse any interfering signal affects only a

small portion of the signal. On the other hand, due to very low power of the UWB signal its interference to



other systems could by practicaly neglected. Many factors have to be analyzed to estimate system

interference performances regarding other systems: distance between devices, modulation techniques used

and propagation loss in a channel.

(2) UWB signal has the high probability to get through obstacles (walls) or to penetrate in the material,

which make it suitable for many applications.

(3) UWB subnanosecond signal can be used for very precise distance, displacement and profile

measurements, important in technical and medical diagnostics.

(4) It would be possibble to inject UWB signals in existing cable systems, becuse its power beyond the

noise level in these systems. Some companies are considering such possibility [6].

The main drawback of UWB technology is potential interference with other wireless communication

systems such as Global Positioning System (GPS), as well as other systems using narrow band.

Fig. 2a. Pulse-position modulation (PPM)

Fig. 2a. Pulse-position modulation (PPM)

Fig. 3a. Pseudo-random time modulation

Fig. 3b. Frequency spectrum of pseudo-random time modulation

100 ns

200 ps

0 1

Time (ns)

Power (dB)



II. CHARACTERISTICS AND METHODS OF GENERATIONS OF UWB PULSE SIGNALS

Pulse Generator

Due to low transmit output power of -41.3dBm/MHz over the 3.1 - 10.6 GHz band, the UWB

pulse waveform is required to satisfy the spectral mask regulation. There are several pulse shapes

for UWB communications. The optimal choice of UWB pulse shape depends on the pulse

duration, frequency spectrum, and the application. The most common pulse shape found in the

literature is Gaussian pulse because its shape is easily generated [8], and it is less sensitive to

inter-symbol interference [7]. The expression of a general Gaussian pulse is given by

[5]

Fig-4

The basic UWB pulse-based is easily generated by the first derivative of Gaussian pulse referred

to monocycle; however, the power spectral density of the first derivative Gaussian pulse does not

meet the FCC mask regulatory requirement. One solution is to modulate the monocycle pulse

with the carrier to shift the center frequency and vary the value of σ to adjust the bandwidth.

Although the transmit power requirement in the band is met, modulation will increase complexity

and power consumption.



0 833n 1.67u 2.5u 3.33u 4.17u 5u-900m

-600m

-300m

0

300m

600m

900m

Xa: 4.967u Xb: 91.67n

Yc: 900.0m Yd:-900.0m

a-b: 4.875u

c-d: 1.800

freq: 205.1k

Ref=Ground X=833n/Div Y=voltage

d

cb a

A

L2

2000nHC21nF

+ V315V

Q22N3796 R2

47R

0 833n 1.67u 2.5u 3.33u 4.17u 5u-21m

-14m

-7m

0

7m

14m

21m

Xa: 5.000u Xb: 0.000

Yc: 21.00m Yd:-21.00m

a-b: 5.000u

c-d: 42.00m

freq: 200.0k


d

cb a

A

An alternative approach is the higher-order derivatives of the Gaussian pulse [9]. In the time

domain, the higher-order derivatives of the Gaussian pulse appear as sinusoidal waveforms

modulated by a Gaussian pulse-shaped envelope. It is clear that increasing the order of the

derivatives results in the increment of the number of zero-crossing in time, corresponding to a

higher carrier frequency sinusoids modulated by an equivalent Gaussian envelope as shown in

Fig. 4. By selecting the optimal order of the derivative and a pulse width, the transmit power

requirement and the maximum bandwidth can be obtained. It shows that at least the 5th

derivative should be used for indoor systems while at least the 7th derivative should be used for

outdoor systems [9]. Pulse shapes or the derivative operation can be implemented by the

highpass filtering.

III A METHOD TO GENERATE ULTRA WIDE BAND PULSE SIGNAL

Bit

Sequence



0 833n 1.67u 2.5u 3.33u 4.17u 5u-2m

-1m

0

1m

2m

3m

4m

Xa: 5.000u Xb: 0.000

Yc: 4.000m Yd:-2.000m

a-b: 5.000u

c-d: 6.000m

freq: 200.0k


d

cb a

A

L2

2nHC21pF

+ V315V

Q22N3796 R2

47R

L2

0.2nHC21pF

+ V315V

Q22N3796 R2

47R

Bit

Sequence

Bit

Sequence



0 833n 1.67u 2.5u 3.33u 4.17u 5u-2.4m

-1.6m

-800u

0

800u

1.6m

2.4m

Xa: 5.000u Xb: 0.000

Yc: 2.400m Yd:-2.400m

a-b: 5.000u

c-d: 4.800m

freq: 200.0k


d

cb a

A

L2

1nHC2

0.2pF

+ V315V

Q22N3796 R2

47R+

C310pF

C110nF

+V

Vs5V

D1LED1

Q22N3796

Q12N3796

GndTrgOutRst Ctl

ThrDisVcc

U1555

R72000k

R647R

R52000k

R447R

R3500k

R2

1000K

R147R

Bit

Sequence



0 833n 1.67u 2.5u 3.33u 4.17u 5u120m

120m

120m

120m

120m

120m

120m

Xa: 4.967u Xb: 91.67n

Yc: 120.0m Yd: 120.0m

a-b: 4.875u

c-d: 2.400n

freq: 205.1k

Ref=Ground X=833n/Div Y=power

d

cb a

A

IV- CONCLUSION

A sub-nanosecond pulsar is a key enabling component for low power UWB applications. The

characteristics of the UWB pulse should be carefully designed to fully utilize the power spectrum

efficiently. Depending on how the technology is deployed, proper spectral filtering is required to

comply with the FCC power spectral mask. Novel impulse generators and pulse-shaping design

techniques must be further explored and developed to achieve more cost-effective,

miniaturized UWB pulse sources. The measurements presented in this article were taken on the

prototype developed by the author to keep abreast with the emerging technology.

V- References

[1] G. R. Alello; Ultra Wide-Band Wireless Systems,IEEE Microvwe, June 2003, pp. 36-47

[2] The National Frequency Allocation Plan 2011 [NFAP- 2011]

[3] Kumar, M., A. Basu, and S. K. Koul, Electromagnetic short pulse generation techniques,"

The 2010 International Symposium on Electromagnetic Theory (EMTS 2010), Berlin, Germany,

Aug. 16{19, 2010)

[4]Improvement of Ultra-Wide-Band Signal Timing B. Vojnovid, B. Medved Rogina Laboratory

for Stochastic Signals and Processes Research, Electronic Division [5] Pulsed RF circuits for

ultra wideband communication and Radar Application Ahmed Maher El-Gabaly Queen's

university Kingston,Ontario, Canada August- 2011

[6] S. Stroh; Ultra-Widwband: Multimedia Unplugged, IEEE Spectrum, September 2003, pp.24-

27.

[8] J. R. Andrews; UWB Signal Sources, Antennas and Propagation, Application Note AN-14a,

Picosecond Pulse Labs., Boulder, CO, August 2003, pp.1-11.

[7] D. Wentzl off, Pulse-Based Ultra-Wideband Transmitters for Digital Communication, Ph.D.

thesis, Massachusetts Institute of Technology, 2002.



[8] M. Ghavami, Ultra Wideband Signals and Systems in Communications Engineering, John

Wiley and Sons, Inc., New York, 2007.

[9] H. Sheng, P. Orlik, A.M. Haimovich, Jr. Cimini, L.J., and J. Zhang, “On the Spectral and

Power Requirements for Ultra-Wideband Transmission,” in Proc. IEEE Int. ommunications

Conf., 2003, vol.1, pp.738–742.

Generation of Ultra-Wide-Band Pulse Signal

Documents

Transcript of Generation of Ultra-Wide-Band Pulse Signal