WO2016151338A1 - Adaptation d'impédance d'antenne à bandes multiples à l'aide de convertisseurs d'impédance négative - Google Patents

Adaptation d'impédance d'antenne à bandes multiples à l'aide de convertisseurs d'impédance négative Download PDF

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Publication number
WO2016151338A1
WO2016151338A1 PCT/GB2016/050856 GB2016050856W WO2016151338A1 WO 2016151338 A1 WO2016151338 A1 WO 2016151338A1 GB 2016050856 W GB2016050856 W GB 2016050856W WO 2016151338 A1 WO2016151338 A1 WO 2016151338A1
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WO
WIPO (PCT)
Prior art keywords
network
matching
branch
matching network
post
Prior art date
Application number
PCT/GB2016/050856
Other languages
English (en)
Inventor
Sampson HU
Liang Wan
Original Assignee
Smart Antenna Technologies Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB1505060.2A external-priority patent/GB2536678B/en
Priority claimed from GB1505058.6A external-priority patent/GB2536676B/en
Application filed by Smart Antenna Technologies Ltd filed Critical Smart Antenna Technologies Ltd
Publication of WO2016151338A1 publication Critical patent/WO2016151338A1/fr

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/28—Impedance matching networks
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/56—Modifications of input or output impedances, not otherwise provided for
    • H03F1/565—Modifications of input or output impedances, not otherwise provided for using inductive elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/04—Frequency selective two-port networks
    • H03H11/10—Frequency selective two-port networks using negative impedance converters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/34—Networks for connecting several sources or loads working on different frequencies or frequency bands, to a common load or source
    • H03H11/342—Networks for connecting several sources or loads working on different frequencies or frequency bands, to a common load or source particularly adapted for use in common antenna systems
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/369—A negative impedance circuit being added to an amplifier circuit

Definitions

  • This invention relates to antenna impedance matching circuits or networks making use of negative impedance converters. Certain aspects relate to matching networks to match antennas to RF loads or sources and, in particular, to a matching network with a negative impedance converter adapted for multi-band operation.
  • TM transverse magnetic
  • TE transverse electric
  • an electrically small TM mode antenna can be characterised by or represented as a series connected combination of a resistor, a capacitor and an inductor.
  • Figures 1 and 2 show that, at low frequencies, the reactance can equally be represented by a series connected capacitor and inductor, with the capacitor playing a dominant role in the reactance.
  • the resistor represents the resistance of the radiating element of the antenna
  • McLean's equation is a derivation from the original Chu limits equations.
  • Harrington limits Harrington, R. F.; "Effect of antenna size on gain, bandwidth and efficiency”; Journal of Research of the National Bureau of Standards - D. Radio Propagation; vol. 64D; p. 12; 29 th June 1959
  • the Chu limit can be related to the antenna bandwidth by rewriting the Q of the antenna as shown in equation 1.3:
  • f c is the antenna centre frequency at resonance and Af is the bandwidth of the antenna.
  • Passive matching networks help to match antennas, but because they involve resonating the reactive part of the antenna with passive elements, they only give a good match at specific frequencies. Away from the specific frequency, the antenna return loss decreases. This necessitates the use of multiple or reconfigurable matching networks to cover wide frequency bands.
  • using non-Foster elements could help provide continuous wideband matching because unlike Foster elements, the slope of the reactance versus frequency of a non-Foster element is always negative as shown in Figure 4.
  • non-Foster elements are able to cancel out completely the reactance of other elements and antennas because of the difference in slope and direction of rotation on the Smith chart.
  • NICs negative impedance converters
  • Linvill Linvill, J.G.; "Transistor negative-impedance converters”; Proc. IRE; vol 41 , pp 725-729; 1953.
  • the Linvill NIC consists of two transistors connected in a common base configuration. "Common base” or “common gate” refers to a specific input and output setup of a transistor in amplifier applications.
  • the RF input terminal is connected to the emitter or source of one transistor, and the RF output terminal to the emitter or source of the other transistor (in fact, since an NIC is normally a bidirectional device, it does not matter which terminal is used as the RF input and which as the RF output).
  • the reactance to be inverted is connected between the two collectors or drains, and the base or gate of each transistor is connected to the collector or drain of the other transistor in the form of a feedback path.
  • the emitters or sources form the two ports of the NIC.
  • the circuit schematic of the NIC is shown in Figure 6.
  • FIG. 7 A typical conventional Linvill type NIC matching arrangement is shown in Figure 7.
  • an active impedance matching network for an electrically-small antenna, the network comprising a plurality of electrically- parallel branches connected between at least one transmitter or receiver or transceiver and the antenna, wherein at least one of the branches comprises a pre-matching transformer, a negative impedance converter and a post-matching network connected in series with each other.
  • Each branch may cover one continuous frequency band, preferably one continuous wide frequency band.
  • the negative impedance converters may comprise series negative inductor- capacitor networks, and may be of Linvill type.
  • the transmitter or receiver or transceiver is a multi-port transmitter or receiver or transceiver, and the post-matching network at the end of each branch is connected to a different port of the transmitter or receiver or transceiver.
  • each branch has two main functions.
  • the first function is to provide an appropriate impedance level over the individual frequency band handled by the branch in question.
  • the second function is to act as an RF filter so as to reduce coupling between respective branches of the network.
  • the components of the negative impedance converter can be selected or adjusted so as to cancel or neutralize the imaginary part of the impedance apparent at the output of the pre-matching transformer.
  • the post-matching network in each branch is configured to transform the impedance, after neutralization of the imaginary part, to match the impedance of the respective transmitter or receiver or transceiver port.
  • the post-matching network at the end of each branch is connected to a single port of a single transmitter or receiver or transceiver.
  • the overall network is divided into a plurality of branches each covering a different frequency band.
  • Each branch includes a pre-matching transformer, a negative impedance converter and a post-matching network as in the first embodiment.
  • the ends of the post-matching networks may be connected together and in turn connected to the single port of the transmitter or receiver or transceiver.
  • the post-matching networks of some of the branches are connected to a first port of a single transmitter or receiver or transceiver, and the post- matching network of at least one other branch is connected to a second port of the single transmitter or receiver or transceiver.
  • the post-matching networks of some of the branches are connected to a port of a first transmitter or receiver or transceiver, and the post-matching network of at least one other branch is connected to a port of at least one further transmitter or receiver or transceiver.
  • the pre-matching transformer in each branch has two functions. One is to provide the proper impedance level over the relevant frequency band so that the respective NIC can easily cancel the transformed imaginary part of the impedance. The other is to act as an RF filter and to reduce coupling between the branches.
  • the NIC in each branch serves to neutralise the imaginary part of the impedance after transformation by the pre-matching transformer.
  • the NIC may be a negative L-C network.
  • the post-matching network in each branch serves to transform the impedance after neutralisation to match the transmitter or receiver or transceiver port impedance.
  • the post-matching networks can act as filters to help reduce coupling between the branches.
  • a matching network for connecting an electrically small antenna to an RF source or load
  • the matching network comprising a negative impedance converter, a pre-matching network for connecting the negative impedance converter to the antenna and a post-matching network for connecting the negative impedance converter to the RF source or load
  • the post-matching network comprises a plurality of parallel branches between the negative impedance converter and the RF source or load, each branch including a separate post-matching impedance transforming circuit and each branch configured to carry a different frequency band.
  • the RF source or load may be at least one transmitter, receiver and/or transceiver.
  • the pre-matching network which may be configured as an impedance transformer, and the negative impedance converter serve to pre-match the antenna before a splitter, diplexer or multiplexer is used to separate the different frequency bands onto the different branches.
  • the post-matching impedance transforming circuit in each branch can be a passive matching circuit and serves to provide a good impedance match in each frequency band. For a typical RF source or load, such as a transceiver, it is desired to match to 50 ⁇ .
  • Tuneable or switchable components such as variable capacitors or variable inductors, may be included in the respective branches to allow independent tuning of the different frequency bands.
  • the matching network comprises two branches
  • one branch may be provided with a series capacitor and the other branch may be provided with a series inductor so as to allow duplexing, i.e. splitting the RF signal into different frequency bands.
  • the component count is reduced (as compared with a system that requires a negative impedance converter in each branch), and this helps to reduce cost; ii) the noise figure is reduced; iii) the complexity of the matching network is reduced, thus saving space; and
  • a matching network for connecting an electrically small antenna to an RF source or load
  • the matching network comprising a first branch provided with a negative impedance converter, a pre-matching network for connecting the negative impedance converter to the antenna and a post-matching network for connecting the negative impedance converter to the RF source or load, and at least one further branch, for connecting the antenna to the RF source or load parallel to the first branch, the at least one further branch provided with a passive matching network, wherein the first branch and the at least one further branch are configured to carry different frequency bands.
  • the passive matching network in the at least one further branch may advantageously be provided on each side with a band-stop, band-pass, high-pass or low- pass filter so as to prevent RF signals intended for passage through the first branch from passing also through the passive matching network in the at least one further branch.
  • the pre-matching network in both the second and third aspects may be a passive circuit, and/or may include filters, and/or may include an impedance transformer such as an NIC.
  • the first and second branches are intended to cover two wide continuous frequency bands simultaneously.
  • the impedance decoupling between the two branches is critical.
  • the pre-matching network in the first branch and at least some of the components in the passive matching network in the second branch provide impedance decoupling seen from the antenna side.
  • the post-matching network in the first branch and at least some other components in the passive matching network in the second branch provide impedance decoupling seen from the transceiver side.
  • the NIC cancels the impedance after pre-matching in the first branch.
  • the NIC impedance itself has a low-pass or band-pass characteristic, it can help to improve the impedance decoupling.
  • Figure 1 shows an electrically small antenna connected to a 50 ohm signal port
  • FIG. 1 shows the antenna of Figure 1 represented as an equivalent series connected resistor, capacitor and inductor
  • Figure 3 shows the arrangement of Figure 2 provided with a passive impedance matching network, together with a plot of reactance against angular frequency;
  • Figure 4 shows the arrangement of Figure 2 provided with a non-Foster matching network comprising a negative capacitance, together with a plot of reactance against angular frequency;
  • Figure 5 illustrates an antenna circumscribed by a sphere of radius a
  • FIG. 6 is a schematic of a conventional Linvill-type negative impedance converter (NIC);
  • Figure 7 shows a conventional NIC arrangement for matching an antenna to a transceiver
  • Figure 8 shows a first embodiment of a first aspect of the present application in schematic outline
  • Figure 9 shows a detailed implementation of a variant of the embodiment of
  • Figures 10a, 10b and 10c show the matching performance of the implementation of Figure 9 at each transceiver port
  • Figure 11 shows a second embodiment of the first aspect of the present application in schematic outline
  • Figure 12 shows a particular implementation of the embodiment of Figure 11 ;
  • Figure 13 shows the matching performance of the implementation of Figure 12 at the transceiver port
  • Figure 14 shows a third embodiment of the first aspect of the present application in schematic outline
  • Figure 15 shows a matching network of a first embodiment of a second aspect of the present application
  • Figure 16 shows a matching network of a second embodiment of the second aspect of the present application
  • Figure 17 shows a matching network of an embodiment of a third aspect of the present application.
  • Figure 18 shows a variation of the matching network of Figure 17 with additional frequency filters
  • Figure 19 is a plot comparing the performance of the Figure 15 and Figure 17 embodiments.
  • Figure 20 shows the return loss and efficiency for the Figure 16 embodiment when a tuneable element is placed in the upper branch
  • Figure 21 shows the return loss and efficiency for the Figure 16 embodiment when a tuneable element is placed in the lower branch.
  • a first embodiment is shown in Figure 8.
  • An antenna 1 is connected to an antenna port 2, and a transceiver 3 has a plurality of transceiver ports 4, 5, 6.
  • the transceiver ports 4, 5, 6 may be ports of different transceivers 3.
  • the antenna port 2 is connected to the transceiver ports 4, 5, 6 by way of a network comprising a plurality of electrically-parallel branches 7, 8, 9.
  • Three branches 7, 8, 9 are shown in Figure 8, but it will be appreciated that other numbers of branches may be implemented as required.
  • Each branch 7, 8, 9 includes a pre-matching transformer 10, 1 1 , 12 connected to the antenna port 2, and a post-matching network 13, 14, 15 connected to a respective transceiver port 4, 5, 6.
  • An NIC (which in some embodiments may be a negative inductor- capacitor network) 16, 17, 18 is provided between the pre-matching transformer 10, 1 1 , 12 and the post-matching network 13, 14, 15 in each branch 7, 8, 9.
  • FIG. 9 shows a detailed implementation of a variant of the embodiment of Figure 8.
  • An antenna 1 is connected to an antenna port 2, and a transceiver has a plurality of transceiver ports 4, 5, 6.
  • the antenna port 2 is connected to the transceiver ports 4, 5, 6 by way of a network comprising a plurality of electrically-parallel branches 7, 8, 20.
  • Three branches 7, 8, 20 are shown in Figure 9, but it will be appreciated that other numbers of branches may be implemented as required.
  • Each of branches 7 and 8 includes a pre-matching transformer 10, 1 1 connected to the antenna port 2, and a post- matching network 13, 14 connected to a respective transceiver port 4, 5.
  • Branch 20 is a passive matching branch, including a passive matching network 21. Branch 20 does not include an NIC.
  • Figures 10a, 10b and 10c respectively show the matching performance at transceiver ports 5, 6 and 4. The plots show the return loss 16, the noise figure 18 and the total efficiency 17.
  • Figure 10a shows the low-frequency band matching performance (including return loss 16, total efficiency 17, and noise figure 18) covered by branch 7 in Figure 9.
  • Figure 10b shows the matching performance covered by branch 8.
  • Figure 10c shows the matching performance covered by branch 20 of Figure 9. It can be seen that Figure 10a covers the whole LTE low band (700MHz-960MHz) with NIC circuit 16, and Figure 10b covers most of the LTE middle and high frequency bands (2050MHz-2700MHz) with NIC circuit 17.
  • Figure 10c covers the GPS/GNSS bands (1550MHz-1650MHz) with passive matching circuit 21.
  • FIG. 1 A second embodiment is shown in Figure 1 1.
  • An antenna 1 is connected to an antenna port 2, and a transceiver 3 has a single transceiver port 4.
  • the antenna port 2 is connected to the transceiver port 4 by way of a network comprising a plurality of electrically-parallel branches 7, 8, 9.
  • Three branches 7, 8, 9 are shown in Figure 1 1 , but it will be appreciated that other numbers of branches may be implemented as required.
  • Each branch 7, 8, 9 includes a pre-matching transformer 10, 1 1 , 12 connected to the antenna port 2, and a post-matching network 13, 14, 15 connected to the transceiver port 4.
  • An NIC (which in some embodiments may be a negative inductor-capacitor network) 16, 17, 18 is provided between the pre-matching transformer 10, 1 1 , 12 and the post-matching network 13, 14, 15 in each branch 7, 8, 9.
  • FIG 12 shows a detailed implementation of a variant of the embodiment of Figure 11.
  • An antenna 1 is connected to an antenna port 2, and a transceiver has a single transceiver port 4.
  • the antenna port 2 is connected to the transceiver port 4 by way of a network comprising a plurality of electrically-parallel branches 7, 8, 20.
  • Three branches 7, 8, 20 are shown in Figure 12, but it will be appreciated that other numbers of branches may be implemented as required.
  • Each of branches 7 and 8 includes a pre-matching transformer 10, 11 connected to the antenna port 2, and a post-matching network 13, 14 connected to the transceiver port 4.
  • NIC which in some embodiments may be a negative inductor-capacitor network
  • Branch 20 is a passive matching branch, including a passive matching network 21.
  • Branch 20 does not include an NIC.
  • Figure 13 shows the matching performance at the transceiver port 4. The plot shows the return loss 16, the total efficiency 17 and the noise figure 18, and shows that the LTE low band (700MHz-960MHz), middle and high frequency bands (1800MHz- 2700MHz), and the GPS/GNSS bands (1550MHz-1650MHz) bands can be handled simultaneously.
  • a third embodiment is shown in Figure 14.
  • An antenna 1 is connected to an antenna port 2, and a transceiver 3 has two transceiver ports 4, 5.
  • the antenna port 2 is connected to the transceiver ports 4, 5 by way of a network comprising a plurality of electrically-parallel branches 7, 8, 9.
  • Three branches 7, 8, 9 are shown in Figure 14, but it will be appreciated that other numbers of branches may be implemented as required.
  • Each branch 7, 8, 9 includes a pre-matching transformer 10, 1 1 , 12 connected to the antenna port 2, and a post-matching network 13, 14, 15.
  • Post-matching networks 13 and 14 are both connected to transceiver port 4, while post-matching network 15 is connected to transceiver port 5.
  • An NIC (which in some embodiments may be a negative inductor-capacitor network) 16, 17, 18 is provided between the pre-matching transformer 10, 1 1 , 12 and the post-matching network 13, 14, 15 in each branch 7, 8, 9.
  • at least one of the branches 7, 8, 9 may comprise a passive matching network.
  • Figure 15 shows a fourth embodiment in which an electrically small antenna 31 is connected to an RF source or load 32 by a matching network comprising an impedance transformer or pre-matching network 34, a negative impedance converter (NIC) 33, and a passive post-matching network 39 comprising first and second parallel branches 35, 36.
  • a matching network comprising an impedance transformer or pre-matching network 34, a negative impedance converter (NIC) 33, and a passive post-matching network 39 comprising first and second parallel branches 35, 36.
  • Each branch 35, 36 is configured to carry a different frequency band, and each branch 35, 36 is provided with a respective passive post-matching circuit 37, 38 for matching the impedance to the RF source or load 32 at the relevant frequency band.
  • the embodiment of Figure 15 is well-suited to applications where the separation between the frequency bands is large.
  • Figure 16 shows a fifth embodiment in which an electrically small antenna 31 is connected to an RF source or load 32 by a matching network comprising an impedance transformer or pre-matching network 34, an NIC 33, and a passive post-matching network 39 comprising first and second parallel branches 35, 36.
  • Each branch 35, 36 is configured to carry a different frequency band, and each branch 35, 36 is provided with a respective passive post-matching circuit 37, 38 for matching the impedance to the RF source or load 32 at the relevant frequency band.
  • the first branch 35 is additionally provided with a tuneable element 40, which may for example be a series inductor, while the second branch 36 is additionally provided with a tuneable element 41 which may for example be a series capacitor.
  • the embodiment of Figure 16 is well-suited to applications where the separation between the frequency bands is small and where independent control is required.
  • Figure 17 shows a sixth embodiment in which an electrically small antenna 31 is connected to an RF source or load 32 by a first branch 35 including an impedance transformer or pre-matching network 34, an NIC 33 and a first passive post-matching network 37 for connecting the NIC 33 to the RF source or load 32.
  • the antenna 31 is additionally connected to the RF source or load 32 by a second branch 36, which includes a passive matching network 38 but no NIC.
  • the first and second branches 35, 36 are configured to carry different frequency bands.
  • FIG 18 shows a variation of the embodiment of Figure 17, with like parts being labelled as in Figure 17.
  • band-stop filters 40, 41 are provided, one on either side of the passive matching network 38.
  • the band-stop filters 40, 41 serve to block RF signals in the frequency range fi to f2, which is handled in the first branch 35, from passing through the passive matching network 38 in the second branch 36.
  • the passive matching network 38 is intended to handle RF signals in the frequency range f3 to .
  • function of the band-stop filters 40, 41 may in some alternative embodiments be provided by band-pass filters, which allow passage of the band f3 to but block the band fi to h. Where appropriate, high-pass or low-pass filters may be used.
  • Figure 19 shows a comparison between the embodiments of Figures 15 and 17, using the same antennas 31 and with the NICs 33 biased to the same DC conditions.
  • the use of a single NIC 33 in both cases is that the NIC 33 provides some matching to the antenna 31 by improving the impedance of the antenna 31.
  • the matching by way of the NIC 33 is not complete, it does improve the antenna impedance to a level where the passive matching by the post-matching circuits 37, 38 can provide an improved match to meet specified requirements.
  • the dashed lines are the results for the Figure 15 embodiment, while the solid lines are the results for the Figure 17 embodiment.
  • tuneable elements such as tuneable or switchable capacitors or inductors, varactors, MEMS capacitors, switchable inductors etc.
  • tuneable elements such as tuneable or switchable capacitors or inductors, varactors, MEMS capacitors, switchable inductors etc.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transceivers (AREA)

Abstract

La présente invention concerne un réseau d'adaptation d'impédance active pour une antenne électriquement petite. Le réseau comprend une pluralité de dérivations électriquement parallèles connectées entre un émetteur-récepteur et l'antenne. Au moins une dérivation comprend un transformateur de pré-adaptation, un convertisseur d'impédance négative et un réseau de post-adaptation connectés en série les uns aux autres. L'invention concerne également un réseau d'adaptation pour connecter une antenne électriquement petite à une source ou charge RF. Le réseau d'adaptation comprend un convertisseur d'impédance négative, un réseau de pré-adaptation pour connecter le convertisseur d'impédance négative à l'antenne et un réseau de post-adaptation pour connecter le convertisseur d'impédance négative à la source ou charge RF. Le réseau de post-adaptation comprend une pluralité de dérivations parallèles entre le convertisseur d'impédance négative et la source ou charge RF. Chaque dérivation comprend un circuit de transformation d'impédance de post-adaptation séparé, et chaque dérivation est conçue pour porter une bande de fréquence différente.
PCT/GB2016/050856 2015-03-25 2016-03-24 Adaptation d'impédance d'antenne à bandes multiples à l'aide de convertisseurs d'impédance négative WO2016151338A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB1505060.2 2015-03-25
GB1505060.2A GB2536678B (en) 2015-03-25 2015-03-25 Reconfigurable multi-band circuit network with negative impedance converter
GB1505058.6 2015-03-25
GB1505058.6A GB2536676B (en) 2015-03-25 2015-03-25 Multi-band antenna impedance matching using negative impedance converters

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WO2016151338A1 true WO2016151338A1 (fr) 2016-09-29

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Publication number Priority date Publication date Assignee Title
US10340878B2 (en) 2017-11-14 2019-07-02 Richwave Technology Corp. Carrier aggregation circuit allowing carrier waves with different frequencies to share the same amplifier

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US20080238789A1 (en) * 2007-03-30 2008-10-02 Sony Ericsson Mobile Communications Ab Antenna interface circuits including multiple impedance matching networks that are respectively associated with multiple frequency bands and electronic devices incorporating the same
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WO1999012231A1 (fr) * 1997-09-04 1999-03-11 Ail Systems, Inc. Dispositif et procede d'adaptation de large bande d'antennes electriquement petites
US20080238789A1 (en) * 2007-03-30 2008-10-02 Sony Ericsson Mobile Communications Ab Antenna interface circuits including multiple impedance matching networks that are respectively associated with multiple frequency bands and electronic devices incorporating the same
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SUSSMAN-FORT S E ET AL: "Non-Foster Impedance Matching for Transmit Applications", ANTENNA TECHNOLOGY SMALL ANTENNAS AND NOVEL METAMATERIALS, 2006 IEEE I NTERNATIONAL WORKSHOP ON CROWNE PLAZA HOTEL, WHITE PLAINS, NEW YORK MARCH 6-8, 2006, PISCATAWAY, NJ, USA,IEEE, 6 March 2006 (2006-03-06), pages 53 - 56, XP010910727, ISBN: 978-0-7803-9443-8, DOI: 10.1109/IWAT.2006.1608973 *
SUSSMAN-FORT S E ET AL: "Non-Foster Impedance Matching of Electrically-Small Antennas", IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, IEEE SERVICE CENTER, PISCATAWAY, NJ, US, vol. 57, no. 8, 1 August 2009 (2009-08-01), pages 2230 - 2241, XP011269388, ISSN: 0018-926X, DOI: 10.1109/TAP.2009.2024494 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10340878B2 (en) 2017-11-14 2019-07-02 Richwave Technology Corp. Carrier aggregation circuit allowing carrier waves with different frequencies to share the same amplifier

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