CN102176689A - Method for determining isolation between antennas - Google Patents

Abstract

The invention provides a method for determining isolation between antennas, which comprises the following steps of: modeling the antennas of which the isolation needs to be computed; enabling the antennas of which the isolation needs to be computed to be equivalent to a multi-port microwave network, wherein each antenna corresponds to a port; and then, computing the isolation between the antennas by using a formula, wherein C represents the isolation between the antennas, S11 and S21 respectively represent S parameters between two ports, and theta represents the phase position corresponding to S11. The method provided by the invention, which is used for directly computing the isolation between the antennas through the formula, is quick and convenient and avoids the defects that the isolation between antennas is acquired through complicated tests and many interference factors exist in the tests in the past, so that the result is closer to the theoretical condition, and the workload is greatly lowered. The invention provides a definite data index for analyzing electromagnetic energy crosstalk generated after different radio frequency devices pass through antennas.

Description

A kind of definite method of isolation between antennas

Technical field

The present invention relates to a kind of isolation analytical method of the antenna of multimachine on the same stage.

Background technology

Isolation between antennas is the important indicator that characterizes the antenna coupled characteristic.In the engineering, the definition normal power and the voltage of isolation between antennas are represented.

Represent that with the power of dual-mode antenna the formula of isolation between antennas is in the engineering:

C represents the size of the antenna degree of coupling, P _rThe power of representing reception antenna to receive, P _tThe transmitting power of expression transmitting antenna.

Can also represent isolation between antennas with voltage in the engineering, establish U ₁, U ₂Be respectively the port voltage of transmitting antenna and reception antenna, its unit is μ V, redefines antenna receiving-sending power, then formula with voltage and impedance

Can be expressed as U _D, U _S1Be respectively U ₁With U ₂Turn to the later value of dB μ V.

Multiple antenna is worked on same platform, and radiation receives mutually, forms a complex electromagnetic environments.In this complex electromagnetic environments, can the antenna of different subsystems operate as normal and not to be subjected to the influence of other aerial radiation be a major issue of overall system Electro Magnetic Compatibility assessment.With power and voltage definition isolation between antennas, the engineering staff can obtain the result of isolation between antennas by test.In view of the complexity of electromagnetic environment, electromagnetic compatibility test (comprising the isolation between antennas test) all has higher requirement to test environment and testing equipment, and the mistake of any one link all may cause result's deviation.So, obtaining isolation between antennas by concrete test, workload is big, the data acquisition cycle is long and the error possibility is big.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, a kind of definite method of easy and simple to handle, quick, isolation between antennas that error is little is provided.

Technical solution of the present invention is: a kind of definite method of isolation between antennas, step is: the antenna that calculate isolation is carried out modeling, the antenna equivalence that will calculate isolation by modeling is a multiport microwave network, and the corresponding port of each antenna utilizes formula then

Calculate the isolation of antenna, C is the isolation of antenna in the formula, S ₁₁And S ₂₁Be respectively two S parameters between the port, θ is and benchmark port S parameter S ₁₁Corresponding phase place.

The present invention's advantage compared with prior art is:

(1) the inventive method without test, calculates the isolation of antenna based on the S parameter of antenna emulation by formula, the used parameter of formula is to obtain by software emulation, quick and convenient, avoided obtaining by loaded down with trivial details test the approach of isolation between antennas in the past, saved workload greatly;

(2) isolation between antennas computational methods of the present invention are based on the S parameter of antenna emulation, and computational speed is fast, obtain isolation between antennas than test and saved the time greatly, improved operating efficiency in research work greatly;

(3) the inventive method is calculated by emulation and formula and is tried to achieve isolation between antennas, effective departure factor, and numerous disturbing factor in avoiding testing makes the result more near theoretical case.

Description of drawings

Fig. 1 is the wave parameter schematic diagram of two-port network of the present invention;

Fig. 2 is the microwave network schematic diagram for antenna equivalence of the present invention;

Fig. 3 is the FB(flow block) of the inventive method.

Embodiment

The present invention is based on the method for S parameter evaluation isolation between antennas, be actually the data such as S parameter that obtain antenna by simulation software, calculate by formula and directly draw isolation between antennas.The derivation of equation of calculating isolation between antennas is that the antenna system equivalence is become microwave network, according to the relation of power, voltage and the S parameter of dual-mode antenna port, derives by engineering isolation defined formula commonly used, and the adding modifying factor, specifically derivation is as follows:

The S parameter is one of scattering parameter of describing microwave network, expression be relation between network port incident wave and the scattered wave.Two-port network as shown in Figure 1, its port signal is respectively (a ₁, b ₁) and (a ₂, b ₂), a ₁And a ₂Be the normalized value of field intensity complex amplitude, be called normalized incident-wave (incoming wave), b ₁And b ₂Be the normalized value of field intensity complex amplitude also, be called normalization reflected wave (removing ripple).The network scattering parameter is that to connect the situation of matched load at each port undefined, and it has clear physical meaning.When port 2 (Fig. 2 right side) when connecing matched load, a ₂=0, S ₁₁And S ₂₁Definition is respectively:

S ₁₁And S ₂₁Expression respectively, when port 2 connect matched load, the reflection coefficient of port one (Fig. 2 left side) and port one were to the transmission coefficient of port 2 ripples.

With the antenna system equivalence is microwave network, and as shown in Figure 2, the input port of transmitting antenna and reception antenna equivalence respectively is the port one and the port 2 of network.For antenna, S ₁₁When the port incoming wave that can be understood as reception antenna was zero, the ratio of the field intensity amplitude of the echo of transmitting antenna port and incident wave also can be understood as the return loss of transmitting antenna; S ₂₁When the port incoming wave that can be understood as reception antenna is zero, the ripple that reception antenna receives from transmitting antenna and the ratio of transmitting antenna port incoming wave field intensity amplitude.

s ₂₁Represent that 2 ports connect matched load, a ₂=0 o'clock, port one was to the transmission coefficient of port 2.The pass of the voltage of two ports and a and b is

U wherein ₁And u ₂It is respectively the voltage complex amplitude of port one and port 2.If use u respectively ⁺And u ^-Expression incident voltage and reflected voltage, then

Wherein

Be the incident voltage of transmitting antenna port,

Be the reception voltage of reception antenna port,

It is the reflected voltage of transmitting antenna port.Voltage in the engineering survey in the isolation between antennas voltage definition is the port total voltage, and definition is

Promptly

U in the formula ₁, u ₂The port total voltage complex amplitude of representing transmitting antenna and reception antenna respectively.When 2 ports connect matched load, that is a ₂=0 o'clock, have

Therefore have

Γ refers to the end reflection coefficient of transmitting antenna in the formula, and θ refers to the initial phase of end reflection coefficient.Then the isolation between antennas based on the S parameter is $C=\frac{20\lg \left|S_{21}\right|}{\sqrt{1+{\left|S_{11}\right|}^2+2\left|S_{11}\right|}\cos \mathrm{\θ}}.$

More than provided the formula that uses the S calculation of parameter isolation between antennas of antenna, by this formula, the researcher can assess the isolation of antenna.

As shown in Figure 3, utilize the formula based on the S parameter to calculate isolation between antennas, concrete implementation step divided for three steps, comprising: the extraction of the software emulation of computation model, the used data of formula, utilize formula to calculate isolation between antennas.

The step of software emulation computation model following (is example with FEKO Electromagnetic Simulation software):

1) opens FEKO software, in working interface, utilize body, face, line modeling tool in the CAD modeling option (Geometry option), set up the model that will calculate antenna structure, this step is finished the foundation of antenna geometries and the material properties of definite antenna each several part.The operator of first use software can carry example with reference to " FEKO5.4 electromagnetic field analysis technology and example detailed annotation " or software, wherein comprised various antenna structure modeling process, the operator only need repeat wherein that modeling procedure just can make up needed model.

2) will define the port and the excitation of antenna after antenna geometries and material properties are determined, this step makes the simple geometric structure possess the function of antenna, is equivalent to define the port of microwave network among Fig. 1.Finish in the port option on the project that the is defined in hurdle of port, wire port, edge port, three kinds of forms of micro-strip port are arranged.The user should be according to the feed principle of antenna, in location definition port form accurately.Setting energisation mode selects Voltage Source just can in the Excitation option.The operator of first use software can carry example with reference to " FEKO5.4 electromagnetic field analysis technology and example detailed annotation " or software, the port setting up procedure that has wherein comprised various antenna, the operator only need find corresponding antenna form, repeats its port and step is set just can finishes this step port setting.

3) to find the solution frequency configuration before the calculating; Frequency configuration is finished in the Frequency option, is provided with and frequency range setting continuously comprising single-frequency point.If calculate the isolation between antennas of certain frequency, select the setting of single-frequency point and in the frequency options hurdle, import calculated rate; If calculate the isolation between antennas of certain frequency range, select continuous frequency range setting and input calculating frequency range in the frequency options hurdle.

4) mesh generation setting, the accuracy relation of this step and calculating is close.Subdivision size one hurdle in the Mesh option is provided with and calculates 1/6～1/10 of wavelength.

5) definition result output, this step is selected the S parameter options in the Calculation option, the S parameter is set in pop-up box, and the port number of definition is identical with the quantity of computation model middle port, the definition of port Impedance will with the input impedance matching of antenna port, generally get 50 ohm.

Click the simulation calculation option and carry out simulation calculation.

The step of the used data extract of formula is as follows:

Emulation is opened the POSTFEKO interface after finishing, and it is the result treatment interface; In the result checks, select the S parameter, check and extract the S parameter and the corresponding phase place thereof of corresponding frequency place antenna.

It is as follows to utilize formula to calculate the isolation between antennas step:

Data substitution isolation between antennas computing formula such as emulation gained S parameter and phase places, calculate isolation between antennas.

The content that is not described in detail in the specification of the present invention belongs to those skilled in the art's known technology.

Claims (1)

1. definite method of an isolation between antennas, it is characterized in that step is: the antenna that calculate isolation is carried out modeling, the antenna equivalence that will calculate isolation by modeling is a multiport microwave network, and the corresponding port of each antenna utilizes formula then

Calculate the isolation of antenna, C is the isolation of antenna in the formula, S ₁₁And S ₂₁Be respectively two S parameters between the port, θ is and benchmark port S parameter S ₁₁Corresponding phase place.

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