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  • Topic: Decibel, Ultra-wideband, Baseband
  • Pages : 23 (7550 words )
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  • Published : September 23, 2011
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Ultrawide band is a unique technology which is used for commercial communications. In this ,I will explain about UWB and how to integrate it with CMOS technology.This is by designing a UWB receiver using CMOS technology. Use Verilog to build behavioral model of LNA,mixer,bandpass filter,integrator.Instante the components in Cadence and run simulation in time domain. In this paper ,I have specified the design considerations of ultra wideband (UWB) receiver architecture. Here, a more power efficient architecture should undertake part of the signal processing

in the analog-domain. Next, the multiband UWB transceiver
is studied and power-efficient circuits is designed for the transceiver.

Ultrawide band technology is a wireless technology to transmit large amount of digital data as modulated coded impulses over a very wide spectrum of frequency with very low power for a short distance.In 2002,the Federal Communications Commission allows UWB Communication in the 3.1-10.6 GHz band having a -10 dB bandwidth greater than 500 MHz and a maximum equivalent isotropic radiated power spectral density of -41.3 dBm/MHz.UWB transmits information using very short pulses requiring a very wide instantaneous bandwidth. Bf=2(fh-fl)/fh+fl

As UWB has very large instantaneous bandwidth hence it offers substantial increase in channel capacity,which can be perceived from Shannon link formula: C=Blog(1+SNR).
The link capacity is proportional to bandwidth and and follows a logarithmic relation with signal to noise ratio.Due to linear relationship between channel capacity and bandwidth ,a very small radiation power is needed to achieve high data rate when the signal bandwidth is large.The frequency domain spectral content of UWB signal is dependent upon pulse waveform shape and pulse width.The most common UWB signals include Gaussian monocycle,Gaussian doublet,Gaussian pulse,Raleigh monocycles and Rectangular waveforms.Most popular ones are Gaussian Waveforms. Pulse Formula is given as follows:

Pg(t)=Ae to the power –(t/tau)(t/tau)where A is pulse amplitude in volts,tau is pulse width in seconds and t is time in seconds . The above is the allocated UWB spectrum.

Various modulation schemes are used for UWB communications which are Pulse Position Modulation,Binary Phase Shift Keying,Pulse Amplitude keying and On-Off Keying(OOK).These are implemented at the transmitter side. * PPM:Delay of pulses carry information about the data in PPM.It is actually a time based modulation technique.Data-bit 1 has time shift added to the reference pulse whereas Data-bit 0 is having no time shift.It uses independent pulses to carry information. * OOK:1 means that the pulse is present and 0 means that the pulse is absent.Only 1 pulse generator is needed and hence it can be easily implemented. * PAM:Information about the data is carried by the amplitude of the pulse. * BPSK:1 is defined by a positive pulse and 0 is defined by the negative pulse. ADVANTAGES OF UWB:

* Very high speed due to high bandwidth multi channel performance. * Extremely Cheap transceivers as both transmitters and receivers consists of CMOS which is affordable. * High frequency adoption flexibility

* Low Power Consumption
* Commonly used in RADAR and positioning systems
Original data is extracted by using a Demodulator at the receiver.Auto-correlation or Rake receiver is used in UWB .In Correlation Receiver operation of match filtering of incoming wave is performed first and then we obtain the result.It requires phase synchronization of the carrier of the received signal and the oscillator output at the receiver.After Correlation operation, correlation results are sent to the baseband for further processing. UWB provides coherent detector as it provides lower bit error rate . MB-OFDM UWB Receiver Specifications

Low-cost highly integrated receiver...
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