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Four-tap RF canceller evaluation for indoor in-band full-duplex wireless operation

Published in:
IEEE Radio and Wireless Symp., RWS 2017, 15-18 January 2017.
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Summary

Analog self-interference mitigation techniques are currently being investigated in a variety of operational settings for In-Band Full-Duplex (IBFD) systems. The significant multipath effects of realistic environments, such as inside buildings, can severely limit performance. The influence of different transceiver parameters on the effectiveness of a four-tap RF canceller using a tapped delay line architecture was characterized with a set of indoor measurements. The prototype canceller yielded up to 30 dB of cancellation over bandwidths ranging from 10 to 120 MHz centered at 2.45 GHz, and produced a combined analog system isolation that reached above 85 dB.
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Summary

Analog self-interference mitigation techniques are currently being investigated in a variety of operational settings for In-Band Full-Duplex (IBFD) systems. The significant multipath effects of realistic environments, such as inside buildings, can severely limit performance. The influence of different transceiver parameters on the effectiveness of a four-tap RF canceller using a...

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The threat to weather radars by wireless technology

Published in:
Amer. Meteor. Soc., Vol. 97, No. 7, 1 July 2016, pp. 1159-67, doi: 10.1175/BAMS-D-15-00048.1.

Summary

Wireless technology, such as local area telecommunication networks and surveillance cameras, causes severe interference for weather radars, because they use the same operational radio frequencies. One or two disturbances can be removed from the radar image, but the number and power of the interfering wireless devices are growing all over the world, threatening that one day the radars could not be used at all. Some agencies have already changed or are considering changing frequency bands, but now even other bands are under threat. Use of equipment at radio frequencies is regulated by laws and international agreements. Technologies have been developed for peaceful co-existence. If wireless devices use these technologies to protect weather radars, their data transmission capabilities become limited, so it is tempting to violate the regulations. Hence, it is an important task for the worldwide weather community to involve themselves in the radio-frequency management process and work in close contact with their National Radio Authorities to ensure that meteorological interests be duly taken into account in any decision making process toward the future usage of wireless devices.
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Summary

Wireless technology, such as local area telecommunication networks and surveillance cameras, causes severe interference for weather radars, because they use the same operational radio frequencies. One or two disturbances can be removed from the radar image, but the number and power of the interfering wireless devices are growing all over...

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Single antenna in-band full-duplex isolation-improvement techniques

Published in:
IEEE Int. Symp. Antennas and Propagation (APSURSI), 26 June - 1 July 2016.
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Summary

Many in-band full-duplex wireless systems transmit and receive on a single antenna to minimize redundancy and maintain compact form factors. For effective operation, all of these systems need to maximize transmit-to-receive isolation, which is limited by non-ideal antenna matching and non-zero circulator leakage. Several isolation-improvement techniques are investigated in this paper, and illustrate how RF components can be used to minimize the consequential self-interference of these systems. Two unique cancellation schemes were validated, and the isolation of a single-antenna transceiver was measured to improve by 15 and 33 dB over the 100 MHz bandwidth centered at 2.45 GHz.
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Summary

Many in-band full-duplex wireless systems transmit and receive on a single antenna to minimize redundancy and maintain compact form factors. For effective operation, all of these systems need to maximize transmit-to-receive isolation, which is limited by non-ideal antenna matching and non-zero circulator leakage. Several isolation-improvement techniques are investigated in this...

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Multitap RF canceller for in-band full-duplex wireless communications

Published in:
IEEE Wirel. Commun., Vol. 15, No. 6, June 2016, pp. 4321-34.
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Summary

In-band full-duplex wireless communications are challenging because they require the mitigation of self-interference caused by the co-located transmitter to operate effectively. This paper presents a novel tapped delay line RF canceller architecture with multiple non-uniform pre-weighted taps to improve system isolation by cancelling both the direct antenna coupling as well as multipath effects that comprise a typical interference channel. A four-tap canceller prototype was measured over several different operating conditions, and was found to provide an average of 30 dB signal cancellation over a 30 MHz bandwidth centered at 2.45 GHz in isolated scenarios. When combined with an omni-directional high-isolation antenna, the canceller improved the overall analog isolation to 90 dB for these cases. In an indoor setting, the canceller suppressed a +30 dBm OFDM signal by 22 dB over a 20 MHz bandwidth centered at 2.45 GHz, and produced 78 dB of total analog isolation. This complete evaluation demonstrates not only the performance limitations of an optimized multitap RF canceller, but also establishes the amount of analog interference suppression that can be expected for the different environments considered.
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Summary

In-band full-duplex wireless communications are challenging because they require the mitigation of self-interference caused by the co-located transmitter to operate effectively. This paper presents a novel tapped delay line RF canceller architecture with multiple non-uniform pre-weighted taps to improve system isolation by cancelling both the direct antenna coupling as well...

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Competing cognitive resilient networks

Published in:
IEEE Trans. Cognit. Commun. and Netw., Vol. 2, No. 1, March 2016, pp. 95-109.

Summary

We introduce competing cognitive resilient network (CCRN) of mobile radios challenged to optimize data throughput and networking efficiency under dynamic spectrum access and adversarial threats (e.g., jamming). Unlike the conventional approaches, CCRN features both communicator and jamming nodes in a friendly coalition to take joint actions against hostile networking entities. In particular, this paper showcases hypothetical blue force and red force CCRNs and their competition for open spectrum resources. We present state-agnostic and stateful solution approaches based on the decision theoretic framework. The state-agnostic approach builds on multiarmed bandit to develop an optimal strategy that enables the exploratory-exploitative actions from sequential sampling of channel rewards. The stateful approach makes an explicit model of states and actions from an underlying Markov decision process and uses multiagent Q-learning to compute optimal node actions. We provide a theoretical framework for CCRN and propose new algorithms for both approaches. Simulation results indicate that the proposed algorithms outperform some of the most important algorithms known to date.
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Summary

We introduce competing cognitive resilient network (CCRN) of mobile radios challenged to optimize data throughput and networking efficiency under dynamic spectrum access and adversarial threats (e.g., jamming). Unlike the conventional approaches, CCRN features both communicator and jamming nodes in a friendly coalition to take joint actions against hostile networking entities...

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Comb generator design for SWaP-constrained applications

Published in:
2016 IEEE Radio and Wireless Symp., RWS 2016, 24-27 January 2016.
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Summary

Many wireless devices have requirements that emphasize low size, weight and power for increased functionality and extended lifetimes. The additional complexity of these devices mandates the need to dynamically verify that all sub-system functions are fully operational. These tests can only be performed internal to the unit, and a circuit that could be utilized to meet this demand should be constructed to be as simple as possible. This paper presents both a novel set of equations to represent a compact comb generator circuit using a step recovery diode as well as unique sequential measurements of a prototype to provide greater insight into the design. The analyzed circuit requires no bias voltage, and effectively produces harmonics up to 2 GHz with a 2 MHz input signal, which is sufficient for adding built-in-test capability to most wireless devices.
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Summary

Many wireless devices have requirements that emphasize low size, weight and power for increased functionality and extended lifetimes. The additional complexity of these devices mandates the need to dynamically verify that all sub-system functions are fully operational. These tests can only be performed internal to the unit, and a circuit...

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Simultaneous Transmit and Receive (STAR) mobile testbed

Published in:
2016 IEEE Radio and Wireless Symp., RWS 2016, 24-27 January 2016.
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Summary

Simultaneous Transmit and Receive (STAR) systems typically utilize multiple cancellation layers to improve system isolation and avoid self-interference. The design of these different layers must be evaluated both individually and as a whole to determine their effectiveness in various environments. A flexible and reusable mobile testbed was constructed to aid in the development and assessment of these different STAR technologies for both stationary and non-stationary applications. The usefulness of this platform was confirmed during the integration of an example STAR system that measured greater than 100 dB of total system isolation over a 30 MHz bandwidth centered at 2.45 GHz.
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Summary

Simultaneous Transmit and Receive (STAR) systems typically utilize multiple cancellation layers to improve system isolation and avoid self-interference. The design of these different layers must be evaluated both individually and as a whole to determine their effectiveness in various environments. A flexible and reusable mobile testbed was constructed to aid...

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Simultaneous transmit and receive (STAR) system architecture using multiple analog cancellation layers

Published in:
2015 IEEE MTT-S Int. Microwave Symp. (IMS 2015) 17-22 May 2015.
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Summary

Simultaneous Transmit and Receive operation requires a high amount of transmit-to-receive isolation in order to avoid self-interference. This isolation is best achieved by utilizing multiple cancellation techniques. The combination of adaptive multiple-input multiple-output spatial cancellation with a high-isolation antenna and RF canceller produces a novel system architecture that focuses on cancellation in the analog domain before the receiver's low-noise amplifier. A prototype of this system has been implemented on a moving vehicle, and measurements have proven that this design is capable of providing more than 90 dB of total isolation in realistic multi path environments over a 30 MHz bandwidth centered at 2.45 GHz. Index Terms-Adaptive systems, full-duplex wireless communication, interference cancellation, multiaccess communication, simultaneous transmit and receive, STAR.
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Summary

Simultaneous Transmit and Receive operation requires a high amount of transmit-to-receive isolation in order to avoid self-interference. This isolation is best achieved by utilizing multiple cancellation techniques. The combination of adaptive multiple-input multiple-output spatial cancellation with a high-isolation antenna and RF canceller produces a novel system architecture that focuses on...

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Higher order cochlea-like channelizing filters

Published in:
IEEE Trans. Microw. Theory Tech., Vol. 56, No. 7, July 2008, pp. 1675-1683.
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Summary

A design method is presented for contiguous-channel multiplexing filters with many channels covering a wide bandwidth. The circuit topology extends previous work on cochlea-like channelizers by introducing multiple resonator-channel filter sections. The new design provides increased stopband rejection, lower insertion loss, and improved passband shape compared with the earlier version while retaining a simple design method and a compact layout, and requires no post-fabrication tuning. Results of a three-pole ten-channel channelizer covering from 182 MHz to 1.13 GHz with 17.5% bandwidth channels and 1.1-dB insertion loss are presented, and agree well with theory. A discussion of the power handling of planar channelizers is also presented.
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Summary

A design method is presented for contiguous-channel multiplexing filters with many channels covering a wide bandwidth. The circuit topology extends previous work on cochlea-like channelizers by introducing multiple resonator-channel filter sections. The new design provides increased stopband rejection, lower insertion loss, and improved passband shape compared with the earlier version...

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A low-loss double-tuned transformer

Published in:
IEEE Microw. Wirel. Compon. Lett., Vol. 17, No. 11, November 2007, pp. 772-774.
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Summary

In this letter, we present a state-of-the-art, planar double-tuned transformer using high- , micromachined spiral inductors and integrated capacitors. This circuit provides a 4:1 impedance transformation over a 30% bandwidth centered at 4.06 GHz, with a minimum insertion loss of 1.50 dB. The fabricated circuit occupies a total area of 440 500 m2 and finds application in power amplifier and other matching applications. An accurate lumped-element circuit model and design tradeoffs are presented. We believe this is the first implementation of a planar microwave double-tuned transformer.
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Summary

In this letter, we present a state-of-the-art, planar double-tuned transformer using high- , micromachined spiral inductors and integrated capacitors. This circuit provides a 4:1 impedance transformation over a 30% bandwidth centered at 4.06 GHz, with a minimum insertion loss of 1.50 dB. The fabricated circuit occupies a total area of...

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