CN108539350A - A kind of double frequency applied to RFID system is across directional coupler - Google Patents

A kind of double frequency applied to RFID system is across directional coupler Download PDF

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Publication number
CN108539350A
CN108539350A CN201810409937.2A CN201810409937A CN108539350A CN 108539350 A CN108539350 A CN 108539350A CN 201810409937 A CN201810409937 A CN 201810409937A CN 108539350 A CN108539350 A CN 108539350A
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CN
China
Prior art keywords
capacitive load
parallel coupled
coupled line
load parallel
segment
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Pending
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CN201810409937.2A
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Chinese (zh)
Inventor
刘宏梅
房少军
王钟葆
傅世强
邵特
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Dalian Maritime University
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Dalian Maritime University
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Publication date
Application filed by Dalian Maritime University filed Critical Dalian Maritime University
Priority to CN201810409937.2A priority Critical patent/CN108539350A/en
Publication of CN108539350A publication Critical patent/CN108539350A/en
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P5/00—Coupling devices of the waveguide type
    • H01P5/12—Coupling devices having more than two ports
    • H01P5/16—Conjugate devices, i.e. devices having at least one port decoupled from one other port
    • H01P5/18—Conjugate devices, i.e. devices having at least one port decoupled from one other port consisting of two coupled guides, e.g. directional couplers

Abstract

The invention discloses a kind of double frequencies applied to RFID system across directional coupler, including：Stepped impedance capacitive load parallel coupled line, the stepped impedance capacitive load parallel coupled line includes first segment capacitive load parallel coupled line, second segment capacitive load parallel coupled line and third section capacitive load parallel coupled line, and the both ends of the second segment capacitive load parallel coupled line are connected with first segment capacitive load parallel coupled line and three sections of capacitive load parallel coupled lines respectively.The coupler has the advantages that easily to realize close coupling, small, intrinsic blocking.

Description

A kind of double frequency applied to RFID system is across directional coupler
Technical field
The invention belongs to electronic technology fields, are related to a kind of microwave device, specially a kind of applied to the double of RFID system Frequency is across directional coupler.
Background technology
Radio frequency identification (RFID) is a kind of automatic identification technology in wireless communication field, is widely used and is purchasing The industries such as industry, manufacturing industry and logistics management.However the frequency distribution of RFID is in global ununified standard, different frequencies at present Section has respective planning and application in every country.This makes RFID be difficult to meet country variant and area in application without barrier Hinder the demand of circulation.With world economy high speed development, kinds of goods contact is more and more frequent between various countries, in order to make RFID tag can be with Applied to multiple systems, double frequency or multi-frequency polarized reading and writing device antenna are needed.
There are four types of different working frequency range for RFID system：Low frequency 125KHz, high frequency 13.56MHz, superfrequency 869MHz, 915MHz and 950MHz and microwave frequency band 2.45GHz and 5.8GHz.In the working frequency range of four kinds of RFID systems, work at the same time 915MHz and 2.45GHz reading and writing data speed ratio low-frequency range of the reading and writing device antenna in far-field range faster, and relative to 5.8GH frequency ranges can realize preferable compromise between antenna performance and cost of manufacture, therefore 0.915/2.45GHz double frequencies are read and write The research of device antenna receives more concern.
Since 0.915/2.45GHz double-frequency reader-writer antennas are circular polarisation working condition, double-frequency directional coupler is needed to make For its feeding network, to provide, amplitude is equal, excitation of 90 ° of phase differences.At present directional coupler be divided into directional coupler in the same direction, Oriented opposite coupler and across directional coupler.Directional coupler in the same direction big, narrow bandwidth deficiency with volume；Oriented opposite Coupler close coupling relatively difficult to achieve.Have the advantages that easily to realize close coupling, small, intrinsic blocking across directional coupler, compared with It is suitable for the feed circuit of reading and writing device antenna.However at present in relation to being single frequency operation across the report of directional coupler, and Research of the double frequency across directional coupler for being applied to 0.915/2.45GHz double-frequency reader-writer antennas is not found.
Invention content
The present invention is directed to the existing defect across directional coupler, proposes a kind of double frequency applied to RFID system across fixed To coupler, to solve the problems, such as to be not used to Double-Frequency System across directional coupler.
A kind of double frequency applied to RFID system of the invention across directional coupler, including：Stepped impedance capacitive load is flat Row coupling line, the stepped impedance capacitive load parallel coupled line include first segment capacitive load parallel coupled line, second segment electricity Hold load parallel coupled line and third section capacitive load parallel coupled line, the both ends of the second segment capacitive load parallel coupled line It is connected respectively with first segment capacitive load parallel coupled line and three sections of capacitive load parallel coupled lines；
The first segment capacitive load parallel coupled line includes the first coupling line, the second coupling line and flying capcitor；It is described Second segment capacitive load parallel coupled line includes third coupling line, the 4th coupling line and the second flying capcitor；The third section electricity It is identical as the structure of first segment capacitive load parallel coupled line to hold load parallel coupled line.
The first segment capacitive load parallel coupled line and third section capacitive load parallel coupled line electricity having the same are long Degree, odd and even mode characteristic impedance and flying capcitor value, the second segment capacitive load parallel coupled line has to be added with first segment capacitance Parallel coupled line odd and even mode characteristic impedance, flying capcitor value and the electricity different with third section capacitive load parallel coupled line is carried to grow Degree.
The even mould electrical length of the second segment capacitive load parallel coupled line be first segment capacitive load parallel coupled line and Two times of third section capacitive load parallel coupled line idol mould electrical length.
The difference of the equivalent strange mould electrical length of the stepped impedance capacitive load parallel coupled line and equivalent even mould electrical length is 180°。
The flying capcitor capacitance of the first segment capacitive load parallel coupled line is identical；The second segment capacitive load is parallel Second flying capcitor capacitance of coupling line is identical.
Across directional coupler, which has easily realizes a kind of double frequency applied to RFID system disclosed by the invention The advantages of close coupling, small, intrinsic blocking.
Description of the drawings
Fig. 1 is structural schematic diagram of the double frequency of the present invention applied to RFID system across directional coupler；
Fig. 2 is the structural schematic diagram of first segment capacitive load parallel coupled line of the present invention；
Fig. 3 is the structural schematic diagram of second segment capacitive load parallel coupled line of the present invention；
Fig. 4 is S parameter curve of the double frequency of the present invention applied to RFID system across directional coupler；
Fig. 5 is the double frequency of the present invention applied to RFID system phase curve between directional coupler output port.
In figure：1, first segment capacitive load parallel coupled line, the 11, first coupling line, the 12, second coupling line, flying capcitor 1-5 includes：(the 13, first flying capcitor, the 14, second flying capcitor, 15, third flying capcitor) 2, second segment capacitive load it is parallel Coupling line, 21, third coupling line, the 22, the 4th coupling line, the second flying capcitor 2-5 include (the 23, the 4th flying capcitor, 24, the Five flying capcitors, the 25, the 6th flying capcitor)
Specific implementation mode
In order to make the objectives, technical solutions and advantages of the present invention clearer, With reference to embodiment and join According to attached drawing, the circuit structure and principle of the present invention are described further.
Fig. 1-3 is respectively that the present invention is applied to structural schematic diagram of the double frequency across directional coupler of RFID system, first 1 structural schematic diagram of section capacitive load parallel coupled line and 2 structural schematic diagram of second segment capacitive load parallel coupled line.Wherein first The odd and even mode characteristic impedance of section and third section capacitive load parallel coupled line 3 is Z1e, Z1o, parity mode electrical length be θ1e, θ1o, across It is C to connect capacitor's capacity1；The odd and even mode characteristic impedance of second segment capacitive load parallel coupled line 2 is Z2e, Z2o, parity mode electrical length For θ2e, θ2o, flying capcitor capacitance be C2。
Since first and third section of capacitive load parallel coupled line is periodical (N sections) capacitive load structure, can be equivalent to strange Ever mode characteristic impedance is Z1eq, Z1oq, parity mode electrical length be θ1eq, θ1oqParallel coupled line；Similarly second segment capacitive load is flat It is Z that row coupling line 2, which can be equivalent to odd and even mode characteristic impedance,2eq, Z2oq, parity mode electrical length be θ2eq, θ2oqParallel coupled line. Relationship between circuit parameter after its is equivalent and primary circuit parameter is as follows：
θieq=θie (1a)
Zieq=Zie (1c)
Wherein N=3, i=1,2, the working frequency that 3, f is coupler.Since the working frequency of double frequency RFID is respectively 915MHz and 2.45GHz, then f=fL=0.915GHz, double frequency are across the frequency ratio of directional couplerAdded with second segment capacitance according to the electrical length of first segment capacitive load parallel coupled line 1 Carry the relationship of 2 electrical length of parallel coupled line, i.e. 2 θ1eq=θ2eq, can calculate θ according to following formula1eqAnd θ2eqIt is big It is small.
Since double frequency RFID circular polarisation reading and writing device antennas need constant amplitude to encourage, then work(point of the double frequency across directional coupler Than k=1, the equivalent even mode impedance ratio of first and second section of capacitive load parallel coupled line can be obtained than definition according to work(pointWith Z1eqRelational expression.
According to formula (2), can obtain and different Z1eqCorresponding Z2eqValue.
Then, due to the equivalent strange mould electrical length of stepped impedance capacitive load parallel coupled line and equivalent even mould electrical length it Difference is 180 °, i.e. 2 θ1eq+θ2eqThe θ of+π=21oq+θ2oq, the equivalent strange mould of stepped impedance capacitive load parallel coupled line can be obtained Electrical length is 277.8 °.
The equivalent odd mode impedance of first and second section of capacitive load parallel coupled line can be obtained than definition also according to work(point ThanWith Z1oqRelational expression.
According to formula (3), can obtain and different Z1oqCorresponding Z2oqValue.
The equivalent odd and even mode characteristic impedance of first and second section of capacitive load parallel coupled line and equivalent parity mode electrical length are brought into Formula (1) can obtain the odd and even mode characteristic impedance Z of first segment and third section capacitive load parallel coupled line 31e, Z1o, odd even Mould electrical length θ1e, θ1o, flying capcitor capacitance C1；The odd and even mode characteristic impedance Z of second segment capacitive load parallel coupled line 22e, Z2o、 Parity mode electrical length θ2e, θ2o, flying capcitor capacitance C2。
The technical indicator that the present embodiment uses is as follows：
Frequency range：0.865GHz~0.955GHz/2.4GHz~2.483GHz
Work(point ratio：K=1；
The degree of coupling：3±1dB；
Return loss：>20dB；
Isolation：>20dB；
Output port phase difference：90°±5°.
In a specific embodiment of the present invention, which is respectively 915MHz and 2.45GHz, and the degree of coupling is 3dB (work( Divide than k=1).According to above-mentioned formula, Z is chosen1eq=120.7 Ω, θ1oq=80 °, Z1oq=23.4 Ω can obtain the ginseng of circuit Number is：Z1e=120.7 Ω, Z2e=121.7 Ω, Z1o=81 Ω, Z2o=62.9 Ω, C1=1.58pF, C2=1.6pF.According to institute The characteristic impedance obtained the double frequency of the invention with electrical length design is across directional coupler, as a result as shown in Figures 4 and 5, the present embodiment Double frequency across directional coupler working frequency range be 0.8GHz~1.0GHz and 2.3GHz~2.5GHz.In the band limits Interior, return loss and isolation are all higher than 20dB, and the degree of coupling is 3 ± 0.7dB, and phase difference is 90 ° ± 1 ° between output port.
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto, Any one skilled in the art in the technical scope disclosed by the present invention, according to the technique and scheme of the present invention and its Inventive concept is subject to equivalent substitution or change, should be covered by the protection scope of the present invention.

Claims (5)

1. a kind of double frequency applied to RFID system is across directional coupler, it is characterised in that including：Stepped impedance capacitive load Parallel coupled line, the stepped impedance capacitive load parallel coupled line include first segment capacitive load parallel coupled line (1), second Section capacitive load parallel coupled line (2) and third section capacitive load parallel coupled line (3), the parallel coupling of the second segment capacitive load The both ends of zygonema (2) are connected with first segment capacitive load parallel coupled line (1) and three sections of capacitive load parallel coupled lines (3) respectively It connects；
The first segment capacitive load parallel coupled line (1) includes the first coupling line (11), the second coupling line (12) and bridging electricity Hold (1-5)；The second segment capacitive load parallel coupled line (2) includes third coupling line (21), the 4th coupling line (22) and Two flying capcitors (2-5)；The third section capacitive load parallel coupled line (3) and first segment capacitive load parallel coupled line (1) Structure it is identical.
2. a kind of double frequency applied to RFID system according to claim 1 is across directional coupler, it is characterised in that：Institute State first segment capacitive load parallel coupled line (1) and third section capacitive load parallel coupled line (3) electrical length having the same, strange Ever mode characteristic impedance and flying capcitor value, the second segment capacitive load parallel coupled line (2) have and first segment capacitive load Parallel coupled line (1) and different odd and even mode characteristic impedance, flying capcitor value and the electricity of third section capacitive load parallel coupled line (3) Length.
3. a kind of double frequency applied to RFID system according to claim 1 is across directional coupler, it is characterised in that：Institute The even mould electrical length for stating second segment capacitive load parallel coupled line (2) is first segment capacitive load parallel coupled line (1) and third Two times of the even mould electrical length of section capacitive load parallel coupled line (3).
4. a kind of double frequency applied to RFID system according to claim 1 is across directional coupler, it is characterised in that：Institute The difference of the equivalent strange mould electrical length and equivalent even mould electrical length of stating stepped impedance capacitive load parallel coupled line is 180 °.
5. a kind of double frequency applied to RFID system according to claim 1 is across directional coupler, it is characterised in that：Institute Flying capcitor (1-5) capacitance for stating first segment capacitive load parallel coupled line (1) is identical；The parallel coupling of the second segment capacitive load The second flying capcitor (2-5) capacitance of zygonema (2) is identical.
CN201810409937.2A 2018-05-02 2018-05-02 A kind of double frequency applied to RFID system is across directional coupler Pending CN108539350A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110854483A (en) * 2019-11-28 2020-02-28 辽宁工程技术大学 Broadband miniaturized 90-degree phase shifter and design method thereof
CN111478007A (en) * 2020-03-19 2020-07-31 北京邮电大学 Low-frequency crossing and high-frequency reversing multifunctional multiplexing dual-frequency directional coupler
CN113659354A (en) * 2021-08-10 2021-11-16 大连海事大学 3X 3 norlon matrix based on crossing directional coupling lines

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5423081A (en) * 1993-08-16 1995-06-06 Hughes Aircraft Company Cellular power amplifier power level control circuitry
CN103338016A (en) * 2013-06-06 2013-10-02 中国科学院上海微系统与信息技术研究所 Lumped-parameter 90-degree quadrature coupler with harmonic suppression function
CN103972632A (en) * 2014-05-23 2014-08-06 大连海事大学 Frequency-tunable micro-strip crossing directional coupler
CN106816678A (en) * 2017-01-18 2017-06-09 大连海事大学 It is a kind of with any output amplitude and phase across directional coupler
CN107819176A (en) * 2016-09-14 2018-03-20 南京航空航天大学 The double frequency coupler of double frequency coupler and broadband based on symmetrical stepped impedance parallel coupled line

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5423081A (en) * 1993-08-16 1995-06-06 Hughes Aircraft Company Cellular power amplifier power level control circuitry
CN103338016A (en) * 2013-06-06 2013-10-02 中国科学院上海微系统与信息技术研究所 Lumped-parameter 90-degree quadrature coupler with harmonic suppression function
CN103972632A (en) * 2014-05-23 2014-08-06 大连海事大学 Frequency-tunable micro-strip crossing directional coupler
CN107819176A (en) * 2016-09-14 2018-03-20 南京航空航天大学 The double frequency coupler of double frequency coupler and broadband based on symmetrical stepped impedance parallel coupled line
CN106816678A (en) * 2017-01-18 2017-06-09 大连海事大学 It is a kind of with any output amplitude and phase across directional coupler

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110854483A (en) * 2019-11-28 2020-02-28 辽宁工程技术大学 Broadband miniaturized 90-degree phase shifter and design method thereof
CN111478007A (en) * 2020-03-19 2020-07-31 北京邮电大学 Low-frequency crossing and high-frequency reversing multifunctional multiplexing dual-frequency directional coupler
CN111478007B (en) * 2020-03-19 2021-04-23 北京邮电大学 Low-frequency crossing and high-frequency reversing multifunctional multiplexing dual-frequency directional coupler
CN113659354A (en) * 2021-08-10 2021-11-16 大连海事大学 3X 3 norlon matrix based on crossing directional coupling lines
CN113659354B (en) * 2021-08-10 2022-11-18 大连海事大学 3X 3 norlon matrix based on crossing directional coupling lines

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Application publication date: 20180914