hossein hashemi - Academia.edu (original) (raw)

Papers by hossein hashemi

This paper reports the results of extensive measurements and analysis of the indoor radio propaga... more This paper reports the results of extensive measurements and analysis of the indoor radio propagation channel's temporal variations. The empirical data base consists of 192 one-min recordings of CW envelope fading waveforms with both antennas stationary. Measurements were carried out in an office environment at 1100 MHz with four transmitter-receiver antenna separations of 5,10,20, and 30 m. Effects of controlled degrees of motion with 0, 1, 2, 3, or 4 individuals walking around the high antenna only, around the low antenna only, and around both antennas were investigated. The reported results include amplitude fading distributions, correlation properties, level crossing rates, duration of fades statistics, and spectrum widths of the frequency domain data. The results can be used in fixed wireless computer communication applications, and in supplementing the available spatial variation models of the indoor radio propagation channel.

... D. Tho11 is with Northern Telecom, Wireless Development Center, Calgruy, Alberta, Canada T2E ... more ... D. Tho11 is with Northern Telecom, Wireless Development Center, Calgruy, Alberta, Canada T2E 7V7. ... Page 2. HASHEMI AND THOLL: STATISTICAL MODELING AND SIMULATION OF RMS DELAY SPREAD OF INDOOR RADIO PROPAGATION CHANNELS 111 ...

IEEE Transactions on Vehicular Technology, 1994

IEEE Journal of Solid-state Circuits, 2007

An oscillator with a high-order ( 2) resonator has multiple stable modes of oscillations. The sta... more An oscillator with a high-order ( 2) resonator has multiple stable modes of oscillations. The stable modes for one such oscillator, having a fourth-order resonator, are found using a nonlinear analysis. By using a proper nonlinear active topology and tank component values, the fourth-order oscillator can generate either of the two distinct frequencies 1 or 2 . A method is introduced to dynamically switch between the stable modes of oscillations. It is shown that the phase noise of this fourth-order oscillator, when generating only one of its resonant frequencies, is comparable to the phase noise of a second-order oscillator using the same active topology and resonator quality factor. Furthermore, the fourth-order oscillator has better phase noise and/or higher tuning range in VCO implementations compared to the commonly used switched resonator oscillators. The claims have been verified experimentally through an integrated oscillator prototype with 1 = 2 4 GHz and 2 = 4 7 GHz fabricated in a standard 0.18 m CMOS technology. The oscillator draws 1.89 mA current of 1.8 V supply. The 1 MHz offset phase noises of the fourth-order oscillator for 1 = 2 4 GHz and 2 = 4 7 GHz are 122.4 dBc/Hz and 123.4 dBc/Hz, respectively.

IEEE Journal of Solid-state Circuits, 2007

A fully integrated CMOS ultra-wideband 4-channel timed array receiver for high-resolution imaging... more A fully integrated CMOS ultra-wideband 4-channel timed array receiver for high-resolution imaging application is presented. A path-sharing true time delay architecture is implemented to reduce the chip area for integrated circuits. The true time delay resolution is 15 ps and the maximum delay is 225 ps. The receiver provides 11 scan angles with almost 9 degrees of spatial resolution for an antenna spacing of 3 cm. The design bandwidth is from 1 to 15 GHz corresponding to less than 1 cm depth resolution in free space. The chip is implemented in 0.13 m CMOS with eight metal layers, and the chip size is 3.1 mm by 3.2 mm. Measurement results for the standalone CMOS chip as well as the integrated planar antenna array and the CMOS chip are reported.

IEEE Communications Magazine, 2008

This article covers the basic principles of true-time-delay (TTD)-based space-time array processo... more This article covers the basic principles of true-time-delay (TTD)-based space-time array processors and ultra-wideband beamformers. General considerations regarding the need for TTD array processing, optimum array size, antenna spacing, and array patterns are discussed for communication and imaging UWB arrays. Several recent integrated circuit implementations of UWB TTD-based beamformers are presented. A few commercial applications that warrant UWB TTD-based array processing, with emphasis on imaging and sensing, are also described.

IEEE Journal of Solid-state Circuits, 2006

Ultra-wideband (UWB) beam-forming, a special class of multiple-antenna systems, allows for high a... more Ultra-wideband (UWB) beam-forming, a special class of multiple-antenna systems, allows for high azimuth and depth resolutions in ranging and imaging applications. This paper reports a fully integrated UWB beam-former featuring controllable true time delay and power gain. Several system and circuit level parameters and characterization methods influencing the design and testing of UWB beam-formers are discussed. A UWB beam-former prototype for imaging applications has been fabricated with the potential to yield 20 mm of range resolution and a 7 angular resolution from a four-element array with 10 mm element spacing. The UWB beam-former accomplishes a 4-bit delay variation for a total of 64 ps of achievable group delay with a 4-ps resolution, a 5-dB gain variation in 1-dB steps, and a worst case 3-dB gain bandwidth of 13 GHz. Overall operation is achieved by the integration of a 3-bit tapped delay trombone-type structure with a 4-ps variable delay resolution, a 1-bit, 32-ps fixed delay coplanar-type structure, and a variable-gain distributed amplifier. The prototype chip fabricated in a 0.18 m BiCMOS SiGe process occupies 1.6 mm 2 of silicon area and consumes 87.5 mW from a 2.5-V supply at the maximum gain setting of 10 dB.

IEEE Journal of Solid-state Circuits, 2008

... Harish Krishnaswamy, Student Member, IEEE, and Hossein Hashemi, Member, IEEE ... the amplitud... more ... Harish Krishnaswamy, Student Member, IEEE, and Hossein Hashemi, Member, IEEE ... the amplitude for mA for different element phase shifts.2 The sustainable phase shift ... AND HASHEMI: VARIABLE-PHASE RING OSCILLATOR AND PLL ARCHITECTURE FOR INTEGRATED ...

The variable-phase ring oscillator (VPRO) and phase-locked loop (PLL) architecture for integrated... more The variable-phase ring oscillator (VPRO) and phase-locked loop (PLL) architecture for integrated phased arrays enables the elimination of mixers, power splitters/combiners and phase shifters and hence allows for compact and power-efficient implementations. This paper extends the architecture to ultra-wideband (UWB) applications through architectural and circuit innovations. The implementation of a wideband VPRO enables the generation of UWB signals through the PLL which are inherently phase-shifted to accomplish beam-steering. The VPRO operates at half of the desired frequency range, and a squarer is interposed between the VPRO and the power amplifier of each channel. This doubles the bandwidth and the inter-channel phase shift and enables the architecture to cover the ±180° phase-shift range required for full beam-steering coverage. In addition, a waveform-adaptive, tunable-narrowband design paradigm is introduced that greatly simplifies the design of UWB RF blocks. A fully-integrated, 4-channel, 24-27 GHz, phased-array transmitter, useful for vehicular radar applications, is implemented in 0.13 μm CMOS to validate these claims.

A coplanar stripline (CPS) based oscillator topology is introduced that is capable of achieving a... more A coplanar stripline (CPS) based oscillator topology is introduced that is capable of achieving a low phase noise at extremely high frequencies. This oscillator uses a symmetric current sharing active topology and a high quality factor CPS design in a standard CMOS process without relying on any advanced process features such as the thick analog metal layer option. A 26

A fully integrated 24GHz 4-channel phased-array transceiver in 0.13μm CMOS is reported. The archi... more A fully integrated 24GHz 4-channel phased-array transceiver in 0.13μm CMOS is reported. The architecture is based on a variable-phase ring oscillator in a PLL that modulates the baseband for each antenna in the TX mode and downconverts the received signal from all antennas in the RX mode without using RF mixers, signal-path phase shifters, or any power combining network. The 2.3 × 2.1 mm2 chip achieves an array transmit EIRP > 23.8dBm, RX gain > 42dB, and can scan the beam continuously

This paper presents an on-chip multiphase LO generation and distribution technique used to implem... more This paper presents an on-chip multiphase LO generation and distribution technique used to implement a fully-integrated 24-GHz 8-path phased-array receiver in silicon. Sixteen LO phases are generated by an LC ring oscillator and distributed by a symmetric network to all eight paths. The 8-path array achieves a phase shifting resolution of 22.5 o and a total array gain of 61dB. Index Terms -RF receiver, phased-array, wireless communication, beam forming, multiple antenna systems, transmission lines.

IEEE Transactions on Microwave Theory and Techniques, 2002

The concept of concurrent multiband low-noise-amplifiers (LNAs) is introduced. A systematic way t... more The concept of concurrent multiband low-noise-amplifiers (LNAs) is introduced. A systematic way to design concurrent multiband integrated LNAs in general is developed. Applications of concurrent multiband LNAs in concurrent multiband receivers together with receiver architecture are discussed. Experimental results of a dual-band LNA implemented in a 0.35m CMOS technology as a demonstration of the concept and theory is presented.

IEEE Transactions on Microwave Theory and Techniques, 2005

A local-oscillator phase-shifting approach is introduced to implement a fully integrated 24-GHz p... more A local-oscillator phase-shifting approach is introduced to implement a fully integrated 24-GHz phased-array receiver using an SiGe technology. Sixteen phases of the local oscillator are generated in one oscillator core, resulting in a raw beam-forming accuracy of 4 bits. These phases are distributed to all eight receiving paths of the array by a symmetric network. The appropriate phase for each path is selected using high-frequency analog multiplexers. The raw beam-steering resolution of the array is better than 10 for a forward-looking angle, while the array spatial selectivity, without any amplitude correction, is better than 20 dB. The overall gain of the array is 61 dB, while the array improves the input signal-to-noise ratio by 9 dB.

Proceedings of The IEEE, 2005

Silicon offers a new set of possibilities and challenges for RF, microwave, and millimeter-wave a... more Silicon offers a new set of possibilities and challenges for RF, microwave, and millimeter-wave applications. While the high cutoff frequencies of the SiGe heterojunction bipolar transistors and the ever-shrinking feature sizes of MOSFETs hold a lot of promise, new design techniques need to be devised to deal with the realities of these technologies, such as low breakdown voltages, lossy substrates, low-Q passives, long interconnect parasitics, and high-frequency coupling issues. As an example of complete system integration in silicon, this paper presents the first fully integrated 24-GHz eight-element phased array receiver in 0.18-m silicon-germanium and the first fully integrated 24-GHz four-element phased array transmitter with integrated power amplifiers in 0.18-m CMOS. The transmitter and receiver are capable of beam forming and can be used for communication, ranging, positioning, and sensing applications.

IEEE Communications Magazine, 2004

A new concurrent dual-band receiver architecture is introduced that is capable of simultaneous op... more A new concurrent dual-band receiver architecture is introduced that is capable of simultaneous operation at two different frequency bands. The concurrent operation results in higher bandwidth, lower total power dissipation and less sensitivity to channel variations. The architecture uses a novel concurrent dual-band low noise amplifier (LNA), combined with an elaborate frequency conversion scheme to reject the image bands. A

IEEE Journal of Solid-state Circuits, 2004

This paper reports the first fully integrated 24-GHz eight-element phased-array receiver in a SiG... more This paper reports the first fully integrated 24-GHz eight-element phased-array receiver in a SiGe BiCMOS technology. The receiver utilizes a heterodyne topology and the signal combining is performed at an IF of 4.8 GHz. The phase-shifting with 4 bits of resolution is realized at the LO port of the first down-conversion mixer. A ring LC voltage-controlled oscillator (VCO) generates 16 different phases of the LO. An integrated 19.2-GHz frequency synthesizer locks the VCO frequency to a 75-MHz external reference. Each signal path achieves a gain of 43 dB, a noise figure of 7.4 dB, and an IIP3 of 11 dBm. The eight-path array achieves an array gain of 61 dB and a peak-to-null ratio of 20 dB and improves the signal-to-noise ratio at the output by 9 dB.

A fully integrated 8-channel phased-array receiver at 24 GHz is demonstrated. Each channel achiev... more A fully integrated 8-channel phased-array receiver at 24 GHz is demonstrated. Each channel achieves a gain of 43 dB, noise figure of 8 dB, and an IIP3 of -11dBm, consuming 29 mA of current from a 2.5 V supply. The 8-channel array has a beam-forming resolution of 22.5°, a peak-to- ratio of 20 dB (4-bits), a total array gain of

IEEE Transactions on Vehicular Technology, 1994

IEEE Journal of Solid-state Circuits, 2007

IEEE Communications Magazine, 2008

IEEE Journal of Solid-state Circuits, 2006

IEEE Journal of Solid-state Circuits, 2008

IEEE Transactions on Microwave Theory and Techniques, 2002

IEEE Transactions on Microwave Theory and Techniques, 2005

Proceedings of The IEEE, 2005

IEEE Communications Magazine, 2004

IEEE Journal of Solid-state Circuits, 2004