3,462 research outputs found

    The Experimental UWB Link

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    The experimental results from simple ultra wideband link are presented. The UWB link consisting of typical broadband microwave circuits built of commercially available components is able to send and detect unmodulated broadband electrical pulses with 20 MHz pulse repetition frequency. The system operates with approximately 60% of fractional bandwidth in 4GHz band with spectral density of -140dBW/Hz

    A digital polar transmitter for multi-band OFDM Ultra-WideBand

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    Linear power amplifiers used to implement the Ultra-Wideband standard must be backed off from optimum power efficiency to meet the standard specifications and the power efficiency suffers. The problem of low efficiency can be mitigated by polar modulation. Digital polar architectures have been employed on numerous wireless standards like GSM, EDGE, and WLAN, where the fractional bandwidths achieved are only about 1%, and the power levels achieved are often in the vicinity of 20 dBm. Can the architecture be employed on wireless standards with low-power and high fractional bandwidth requirements and yet achieve good power efficiency? To answer these question, this thesis studies the application of a digital polar transmitter architecture with parallel amplifier stages for UWB. The concept of the digital transmitter is motivated and inspired by three factors. First, unrelenting advances in the CMOS technology in deep-submicron process and the prevalence of low-cost Digital Signal processing have resulted in the realization of higher level of integration using digitally intensive approaches. Furthermore, the architecture is an evolution of polar modulation, which is known for high power efficiency in other wireless applications. Finally, the architecture is operated as a digital-to-analog converter which circumvents the use of converters in conventional transmitters. Modeling and simulation of the system architecture is performed on the Agilent Advanced Design System Ptolemy simulation platform. First, by studying the envelope signal, we found that envelope clipping results in a reduction in the peak-to-average power ratio which in turn improves the error vector magnitude performance (figure of merit for the study). In addition, we have demonstrated that a resolution of three bits suffices for the digital polar transmitter when envelope clipping is performed. Next, this thesis covers a theoretical derivation for the estimate of the error vector magnitude based on the resolution, quantization and phase noise errors. An analysis on the process variations - which result in gain and delay mismatches - for a digital transmitter architecture with four bits ensues. The above studies allow RF designers to estimate the number of bits required and the amount of distortion that can be tolerated in the system. Next, a study on the circuit implementation was conducted. A DPA that comprises 7 parallel RF amplifiers driven by a constant RF phase-modulated signal and 7 cascode transistors (individually connected in series with the bottom amplifiers) digitally controlled by a 3-bit digitized envelope signal to reconstruct the UWB signal at the output. Through the use of NFET models from the IBM 130-nm technology, our simulation reveals that our DPA is able to achieve an EVM of - 22 dB. The DPA simulations have been performed at 3.432 GHz centre frequency with a channel bandwidth of 528 MHz, which translates to a fractional bandwidth of 15.4%. Drain efficiencies of 13.2/19.5/21.0% have been obtained while delivering -1.9/2.5/5.5 dBm of output power and consuming 5/9/17 mW of power. In addition, we performed a yield analysis on the digital polar amplifier, based on unit-weighted and binary-weighted architecture, when gain variations are introduced in all the individual stages. The dynamic element matching method is also introduced for the unit-weighted digital polar transmitter. Monte Carlo simulations reveal that when the gain of the amplifiers are allowed to vary at a mean of 1 with a standard deviation of 0.2, the binary-weighted architecture obtained a yield of 79%, while the yields of the unit-weighted architectures are in the neighbourhood of 95%. Moreover, the dynamic element matching technique demonstrates an improvement in the yield by approximately 3%. Finally, a hardware implementation for this architecture based on software-defined arbitrary waveform generators is studied. In this section, we demonstrate that the error vector magnitude results obtained with a four-stage binary-weighted digital polar transmitter under ideal combining conditions fulfill the European Computer Manufacturers Association requirements. The proposed experimental setup, believed to be the first ever attempted, confirm the feasibility of a digital polar transmitter architecture for Ultra-Wideband. In addition, we propose a number of power combining techniques suitable for the hardware implementation. Spatial power combining, in particular, shows a high potential for the digital polar transmitter architecture. The above studies demonstrate the feasibility of the digital polar architecture with good power efficiency for a wideband wireless standard with low-power and high fractional bandwidth requirements

    A Compact Ultra Wide-Band Radar System for See-Through-Wall Applications

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    A compact Ultra wide-band (UWB) radar system for through-wall applications has been developed. Lightweight, portable and low in power consumption, it is configurable for both bistatic and monostatic operation. It uses low cost, off-the-shelf surface mount components, and is ideally suited for ranging, 3d-imaging, and wall characterization. Tests show excellent pulse width generation, resulting in very broadband transmission (0.7 – 5.6 GHz) and good receiver dynamic range, resulting in accurate measurement capabilities

    The Experimental UWB Link

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    The experimental results from simple ultra wideband link are presented. The UWB link consisting of typical broadband microwave circuits built of commercially available components is able to send and detect unmodulated broadband electrical pulses with 20 MHz pulse repetition frequency. The system operates with approximately 60% of fractional bandwidth in 4GHz band with spectral density of -140dBW/Hz

    A Scalable 6-to-18 GHz Concurrent Dual-Band Quad-Beam Phased-Array Receiver in CMOS

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    This paper reports a 6-to-18 GHz integrated phased- array receiver implemented in 130-nm CMOS. The receiver is easily scalable to build a very large-scale phased-array system. It concurrently forms four independent beams at two different frequencies from 6 to 18 GHz. The nominal conversion gain of the receiver ranges from 16 to 24 dB over the entire band while the worst-case cross-band and cross-polarization rejections are achieved 48 dB and 63 dB, respectively. Phase shifting is performed in the LO path by a digital phase rotator with the worst-case RMS phase error and amplitude variation of 0.5° and 0.4 dB, respectively, over the entire band. A four-element phased-array receiver system is implemented based on four receiver chips. The measured array patterns agree well with the theoretical ones with a peak-to-null ratio of over 21.5 dB

    A two-stage power amplifier design for ultra-wideband applications

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    In this paper, a two-stage 0.18 μm CMOS power amplifier (PA) for ultra-wideband (UWB) 3 to 5 GHz based on common source inductive degeneration with an auxiliary amplifier is proposed. In this proposal, an auxiliary amplifier is used to place the 2nd harmonic in the core amplified in order to make up for the gain progression phenomena at the main amplifier output node. Simulation results show a power gain of 16 dB with a gain flatness of 0.4 dB and an input 1 dB compression of about -5 dBm from 3 to 5 GHz using a 1.8 V power supply consuming 25 mW. Power added efficiency (PAE) of around 47% at 4 GHz with 50 Ω load impedance was also observed
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