Design considerations for direct-conversion receivers

Razavi, Behzad

doi:10.1109/82.592569

Cited by 963 publications

(390 citation statements)

References 17 publications

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“…Digital implementation of direct conversion between the baseband and the radio frequency not only greatly simplifies the architecture of the transceiver, it also brings higher precision of measurements, as well as reductions in size, weight, cost, and maintenance of the instrument. However, while digital transceivers have been in practice for years [Razavi, 1997], it is with a great deal of caution that direct-to-RF technology was considered for the HF receiver design in the Digisonde. Digital receivers that directly digitize the RF signals can easily be saturated by strong interferers, since ADCs have a limited dynamic range, rendering the receivers insensitive to smaller message signals.…”

Section: Digital Transceiver For the Digisonde-4dmentioning

confidence: 99%

New Digisonde for research and monitoring applications

et al. 2009

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[1] The new Digisonde-4D, while preserving the basic principles of the Digisonde family, introduces important hardware and software changes that implement the latest capabilities of new digital radio frequency (RF) circuitry and embedded computers. The ''D'' refers to digital transmitters and receivers in which no analog circuitry is used for conversion between the baseband and the RF. In conjunction with the new hardware design, new software solutions offer significantly enhanced measurement flexibility, enhanced signal selectivity, and new types of data, e.g., the complete set of time domain samples of all four antenna signals suitable for independent scientific analysis. With the new method of mitigating in-band RF interference, the ionogram running time can be made as short as a couple of seconds. The h 0 (f) precision ranging technique with an accuracy of better than 1 km can be used on a routine basis. The 4D model runs the new ARTIST-5 ionogram autoscaling software which reports in real time the required data for assimilation in ionospheric models. The paper highlights technical advances of the new Digisonde for research and monitoring applications.

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Section: Digital Transceiver For the Digisonde-4dmentioning

confidence: 99%

New Digisonde for research and monitoring applications

et al. 2009

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“…several benefits for I/Q mismatch, flicker noise and DC-offset [Raz97], but we will here concentrate on the idealized case We have noted in the "Why I/Q" section that an I/Q receiver is required if the frequency is the same on both of the mixer inputs, while as we have argued, we can avoid an I/Q conversion in the analog domain when we have a frequency offset. To show this in the heterodyning case, we write…”

Section: Sfcw With Frequency Offsetmentioning

confidence: 99%

UWB waveform generator for digital CMOS radar

Bjorndal

Hamran

Lande³

2015

2015 IEEE International Symposium on Circuits and Systems (ISCAS)

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Small, low cost, radar systems have exciting applications in monitoring and imaging for the industrial, healthcare and Internet of Things (IoT) sectors. We here explore, and show the feasibility of, several single bit square wave radar architectures; that benefits from the continuous improvement in digital technologies for system-on-chip digital integration. By analysis, simulation and measurements we explore novel and harmonic-rich continuous wave (CW), stepped-frequency CW (SFCW) and frequency-modulated CW (FMCW) architectures, where harmonics can not only be suppressed but even utilized for improvements in down-range resolution without increasing on airbandwidth. In addition, due to the flexible digital CMOS implementation, the system is proved by measurement, to feasibly implement pseudo-random noise-sequence and pulsed radars, simply by swapping out the digital baseband processing. Single bit quantization is explored in detail, showing the benefits of simple implementation, the feasibility of continuous time design and only slightly degraded signal quality in noisy environments compared to an idealized analog system. Several iterations of a proof-of-concept 90 nm CMOS chip is developed, achieving a time resolution of 65 ps at nominal 1.2 V supply with a novel Digital-to-Time converter architecture. In pulsed mode, the chip features programmable pulses with a minimum width of 130 ps and a time step of 65 ps. In CW mode, we can transmit arbitrary signals up to 3.8 GHz all the way down to DC. With a continuous time single bit receiver, the backscattered signal can be mixed with the on-chip XOR gate and integrated with the on-chip counters, to provide a system-on-chip CW platform.iii

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“…The above references do not consider the effect of the in-phase and quadrature (I/Q) phase imbalance. The I/Q imbalance is due to the mismatch of the amplitude and phase components between the I-branch and Q-branch [6]. It is known that the I/Q imbalance can severely degrade the performance of OFDM systems.…”

Section: Introductionmentioning

confidence: 99%

Joint estimation of CFO and receiver I/Q imbalance using virtual subcarriers for OFDM systems

Chang

Chung

Phoong

et al. 2012

2012 IEEE 23rd International Symposium on Personal, Indoor and Mobile Radio Communications - (PIMRC)

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Abstract-In this paper, we study the estimation of carrier frequency offset (CFO) in the presence of the receiver in-phase and quadrature-phase (I/Q) imbalance for orthogonal frequency division multiplexing (OFDM) systems. By minimizing the energy of the samples on the virtual subcarriers, our proposed algorithm can jointly estimate the CFO and I/Q parameters using one OFDM block. When the CFO is small, a closed-form solution can be obtained. Simulation results show that our proposed method can provide a good performance for both of the I/Q and CFO estimation and it compares favorably with a recent method.

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Design considerations for direct-conversion receivers

Cited by 963 publications

References 17 publications

New Digisonde for research and monitoring applications

New Digisonde for research and monitoring applications

UWB waveform generator for digital CMOS radar

Joint estimation of CFO and receiver I/Q imbalance using virtual subcarriers for OFDM systems

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