Antenna circuit for an MRI system

Technical Field

The invention relates to a method for the improvement of the MRT system antenna circuit, the antenna circuit to control the antenna device or separated from the read signal, wherein the antenna device is radially disposed in the at least one magnet and the at least one gradient coil between the object to be examined.

Background Art

MRT system of the prior art typically has a single transmitter, the transmitter is arranged to generate for applying nuclear spin is used to provide a substantially uniform high-frequency field. Corresponding, also referred to as "physical coil (BC)" a transmission antenna is embedded is normally fixed in the magnet and the gradient coil. On the contrary, in order to receive the magnetic resonance signals is close to the patient, also known as the local coil of the receiving antenna of the multi-channel device. In this each unused antenna usually by PIN diode switch to disconnect or mistuning.

The cable laying due to the complex, do not wish to the local coil is arranged at the object to be examined (that is, the patient) on the received signal and transmitted to the patient table. By means of the so-called "remote physical array" to recommend that the extremely low noise of the fixed installation of the antenna elements of the receiving antenna device. Remote physical array is, for example, US   2010/0213939 A1 to the in. As large as possible as it is expected that the patient aperture Cylindrical so used for "remote physical array" (RBA) radial installation space is limited inwards in a radial direction. Gradient system magnet or more large diameter lead to a dramatic increase in cost. RBA therefore must be close to the transmitting antenna of the receiving element (BC) is placed. Therefore, to send to the coil on the one hand and (BC) produce strong magnetic coupling between RBA, so as to improve the transmitting antenna (BC) the requirements of the detuning switch in, for example, the requirements of the reduction of loss. On the other hand, in the transmitting antenna conductor structure of (BC) will form a vortex, the vortex does not need to switch to participate in also produce loss resistance and the noise is coupled to a receiver of RBA. These loss is a special problem, since the quality of all RBA element with the requirements of the patient because the large interval of the partial coil than on the patient under the condition of the requirement of much higher.

The transmitting antenna has been proposed, and RBA receiving element is also used for transmitting. This solution has the following advantages: more RBA coarse and therefore more effective structure, because it can be used for sending the antenna (BC) elimination of the additional space. Each antenna element to obtain their own sending receiving converter. Because these conversion switch does not need to be located in the high-efficiency of the resonance circuit, but can be in the transformation (for example, conversion to the 50 ohm impedance) is arranged after, therefore, its loss share is not higher than in the usual antenna structure share loss under the situation. For each element of the receiving branches of the converter transmission to a receiver.

Figure 11 shows the arrangement of the prior art. The antenna element 102 is connected to the transmitting/receiving converter 104, the output terminal of the transmitting/receiving transducer is connected to the amplifier 110 input. The input end of the transmitting/receiving transducer is connected to the distribution network, via the corresponding transmitting/receiving converter 104 will be a plurality of antenna 102 is connected to the power distribution network. Transmit amplifier 108 is connected to the output end of the power distribution network 106 of the input end.

For the distribution of the well known solutions by the power distributor and the phase shifter is a series, for example, dispenser uygur Jin Sen (  Teiler Wikinson), Butler matrix (Butler-Matrix), having it is usually 50 ohms impedance in the wire.

This kind of a clearly defined supply network the output impedance, for example 50 ohms, in order to the output impedance of the antenna in each feed. Typically try to each of the antenna with the resistor the optimum matching in relation to the power. Because of different height and patient's position of the patient, in each antenna 102 will appear in the different load resistance. In addition it is necessary to consider the antenna 102 is of mutual coupling. So even when the antenna the travelling wave uniform distribution can also be formed under the condition of extremely non-uniform current distribution, the current distribution will then lead to the power loss of the spin excitation (SAR) and a non-uniform distribution. Usually in order to send the problem in the use of the high-pass or low-pass birdcage antenna device does not happen, since the higher local oscillation frequency mode for the resonance frequency is very far. On the other hand, in order to realize the functionality of the device must be the component of the transmitting/receiving device for decoupling each other, in order to be able to form different current distribution.

Therefore, the need for such distribution: in the power distribution network by means of an antenna device produced the time of transmission of a signal between the antenna elements each other in fixed and does not depend on the current ratio of the load.

In the plurality of coils can be, for example, the same current through the series circuit to obtain. Even if each coil through the capacitor added in order to form the series resonant circuit, the resonant circuit is also can be connected in series. However, in high-frequency under the condition of the series circuit of the distributed capacitance in the usual is not applicable.

Content of the invention

Therefore, the invention aims to solve the technical problem is that, at the time of transmission of a signal by means of an antenna device in the antenna element as far as possible produced is fixed and does not depend on the current ratio of the load, and will not present the disadvantages of the series circuit.

The technical problem of the present invention through a is constructed for magnetic resonance tomography apparatus of the antenna device of the plurality of antenna element feed and the read antenna circuit to solve. Antenna circuit is constructed to the 1st receiving and/or transmitting circuit is connected with the 1st circuit joint. Antenna circuit is constructed so as to be connected to the antenna device antenna element 1st 1st day of the line of the joint and the structure of the antenna device is connected to the antenna element 2nd 2nd day of the joint line. Antenna circuit comprises phase-shifting the signal 90° or 270° and each having a predetermined transmittance 1st phase shifter element and a 2nd phase shifter element. 1st the 1st phase shifter element 1st 2nd phase shifter and the joint is connected to the 1st circuit joint. The 1st phase shifter element 1st day 2nd joint is connected to the line side of the joint and joint 2nd 2nd phase shifter element is connected to the 2nd day of the joint line. If the determined voltage is applied in the 1st circuit joint, because of the electric current the phase shift is 90° or 270° in the 1st and 2nd type of antenna element in accordance with the applied current. By selecting the phase shifter element admittance of the current ratio can be determined.

The technical problem of the present invention is also achieved by an is constructed for magnetic resonance tomography apparatus of the antenna device of the plurality of antenna element feed and/or of the read antenna circuit to solve. Antenna circuit comprises the 1st is constructed for receiving and/or transmitting circuit is connected with the circuit terminal 1st and 2nd and is constructed for receiving and/or transmitting circuit is connected with the 2nd circuit joint. Furthermore, antenna circuit is constructed so as to be connected to the antenna device antenna element 1st 1st day of the joint line. Antenna circuit comprises phase-shifting the signal 90° or 270° and each having a predetermined transmittance 1st phase shifter element and a 2nd phase shifter element. 1st the 1st phase shifter element 1st circuit is connected to the joint of the joint and joint 1st 2nd phase shifter element is connected to the 2nd circuit joint. The 1st phase shifter element 1st 2nd day is connected to the joint of the joint line, and the 2nd phase shifter element 1st 2nd day is connected to the joint of the joint line. In the antenna circuit, is connected to the antenna side of the antenna element of the joint by the electric current in the circuit is multiplied by the corresponding joint of the voltage of the phase shifter element is determined and the admittance of.

Phase shifter element can be a two-port network (Zweitor). In the phase shift 90° or 270° under the condition of two port network parameters of the signal of the input end (that is, electric current and/or voltage) with respect to the two port network in phase on the output terminal of the 90° or 270°. Phase shifter element can be caused by corresponding to the 90° or 270° phase shift of the delay. Phase shifter element can be formed for the delay line. Two port network can have four joint, two joint is the signal joint and the other two joints are measuring joint.

By the phase shifter element from the load on the phase between current and voltage. The load as to absorb the phase shift between the current and the voltage for the reactive load of 0 °, the phase shift is approximately 90°. Phase shifter element does not change the performance, and is produced in the two-port network at the input of the wave and the inflows to the output end of the two-port network flows out of the phase shift between the waves, that is to "delay".

Furthermore, the antenna circuit can be configured to the antenna device to feed and reading, the antenna device is disposed radially between the at least one magnet and at least one gradient coil of an object to be examined and between (such as patient's). The antenna device can be constructed as a birdcage antenna. Preferably, the antenna device is configured to be cylindrical and is arranged between the magnet and the patient.

Antenna circuit can have a phase shift of the signal 90° or 270° and has a predetermined admittance of the 3rd phase shifter element, wherein the 3rd phase shifter element circuit 1st 1st joint is connected to the joint and joint 2nd 3rd phase shifter element is connected to the 3rd day of the joint line. Antenna circuit forming the two input switches to the three antenna power distribution network.

3rd phase shifter element can be connected to the joint 1st 2nd circuit joint and 3rd phase shifter element can be connected to the joint 2nd 1st day of the joint line. In the antenna circuit in a signal can be distributed to a plurality of antenna elements on the circuit connector and a plurality of signal is connected to one antenna element. When the should have when circle , this point is particularly worth desired.

Antenna circuit can have a 1st number is K is connected to the structure for receiving and/or transmitting circuit connector and a quantity of 2nd L is constructed in order to connect to the antenna connector of the antenna element. K can be the number of 1st a circuit connector is connected to the different receiving and/or transmitting circuit or can be at least a portion of the circuit connector is connected to the same receiving and/or transmitting circuit joint. 2nd 1st L K is larger than the number of the number. The joint of each antenna via the phase shifter element and the at least one circuit joint are connected, phase-shifting the signal of the phase shifter element 90° or 270° and has predetermined admittance. At least one antenna through the joint can be of the two phase shifter element is connected to the circuit connector. Formed by this antenna element of the antenna device are coupled to each other but can make use of different current control of power distribution network.

At least two phase shifter element can have different admittance. In order to produce the circular field the form is preferred.

Antenna circuit can have a two circuit connector, wherein the following signal is connected to the 1st circuit connector, the current and the voltage in the signal in-phase. The following signal is connected to the 2nd circuit connector, in in the signal, relative to the current and/or voltage applied to the 1st circuit connector of the mobile signal on phase of the 90°. Phase displacement can be by means of a so-called 90° hybrid device to generate. The antenna circuit is also suitable for use in generating circularly polarized. The antenna is preferably a so-called birdcage antenna.

Antenna circuit may be provided with three antenna side of the joint, these joint and the antenna (such as a birdcage antenna) of which is connected with three antenna element.

Can be any capable of compensating for the phase difference of the phase shifter device is connected to the at least one antenna connector. By using the phase shifter of the transmission device can be to receive the converter, lead, in the matching circuit (for example because of delay) phase shift is compensated.

1st day of the joint line can be configured to be connected to the form of the parallel resonant circuit 1st antenna or antenna element. 2nd day of the line side of the connector can be configured to connect it to form at least one series resonant circuit of the antenna or antenna element. The generated between the voltage and current to phase shift of 90 °, thereby forming a so-called quarter wave long-line (Viertelwellenleitung). Therefore, in principle, can also be through two of the parallel resonant circuit directly connected in parallel circuit forced produce the same current. However, in order to to have adjustable weights of a plurality of input terminals of the current summation, must be through the phase shifter can be revoked oscillation circuit wiring phase shift, thereby once again converted to a parallel circuit of the series circuit.

Produce the 90° phase-shift and with a characteristic impedance Z₀ is connected with the phase shifter element to the impedance of the Z transform for its countdown Z₀²/Z. The frustum is connected with the two-port network into its dual-network. For example, the parallel circuit (that is, the parallel circuit R-L-C) conversion for series circuit (R '-L-C series circuit).

The connector can be antenna via a plurality of series connection of the phase shifter element and the at least one circuit is connected with the joint, wherein the phase shifter element phase shift of the signal 90° or 270° and are respectively provided with predetermined admittance.

Multi-stage distribution network thus obtained. Can be controlled by using the power distribution network in the axial direction, for example, having a plurality of antennas on birdcage antenna. The antenna element of the antenna circuit is provided to ensure mutual decoupling and nevertheless also can be a predetermined current or a predetermined voltage.

Antenna circuit can have a plurality of circuit connector, a plurality of antenna side of the joint and a plurality of the circuit connector and the joint is connected between the antenna phase shifter element. Each of the phase shifter element can be through the capacitor to form. In each of the circuit connector can be connected to the inductance. In each of the antenna can be connected to the joint of the inductance. Such measuring inductance and capacitance, and the antenna circuit is obtained between the joint of the signal of the 90° or 270° phase shift. ∏ circuit through the phase shifter element can be expressed, the ∏ circuit is a two-port network, wherein the two-port network and the capacitor is connected through the joint of two-port network respectively through the coil and is connected to earth ground. Circuit connector or joint of the inductance of the antenna on the size of the is connected in parallel through the equivalent circuit to determine the inductance of, the inductance is connected to the antenna circuit of the corresponding joint.

Antenna circuit can have a 1st, 2nd, 3rd and 4th circuit connector, a plurality of antenna side of the joint and a plurality of the circuit connector and the joint is connected between the antenna phase shifter element. Phase shifter element can be through the capacitor to form. In the 1st and 2nd 1st circuit connector can be connected to the balanced-to-unbalanced converter (Balun), and the 4th 3rd and 2nd circuit connector can be connected to the balanced-to-unbalanced converter. In each of the antenna can be connected to the joint of the inductance. Such measuring balanced-to-unbalanced converter 1st, 2nd balanced-to-unbalanced converter, inductance and capacitance, and the antenna circuit is obtained between the joint of the signal of the 90° or 270° phase shift.

A particularly simple manner by the antenna circuit structure.

In the antenna circuit joint can be connected to the input end of the receiving amplifier.

The present invention also relates to a antenna circuit described in front of the antenna device. Antenna device preferably can be a birdcage antenna.

Description of drawings

Description of drawings shown in the following detailed discussion in the attached Figure of the non-restrictive understanding and other advantages of the embodiment. In the attached drawing:

Figure 1 shows an antenna according to the invention circuit the principle of 1st circuit;

Figure 2 has shown the in accordance with the antenna circuit of the present invention the principle of 2nd circuit;

Figure 3 shows a 1st embodiment of the power distribution network;

Figure 4 shows a 2nd embodiment of the power distribution network;

Figure 5 shows a power distribution network with the phase shifter;

Figure 6 shows the two-stage power distribution network;

Figure 7 shows the equivalent circuit of the phase shifter element;

Figure 8 shows a simplified circuit 1st;

Figure 9 shows a simplified circuit 2nd;

Fig. 10 a is shown when receiving the embodiment of using antenna circuit; and

Figure 11 shows the antenna circuit according to prior art.

Mode of execution

Figure 1 shows an antenna according to the invention circuit the 1st circuit principle. Will provide voltage u_q and current i_q the voltage source is connected to the circuit connector 12. The 1st phase shifter element 4 and 2nd phase shifter element 6 is connected to the circuit connector 12. Phase shifter element 4, 6 make the signal (the voltage and current) generated phase shift of 90°. The 1st phase shifter element 4 is connected to the 1st antenna element 8, and the 2nd phase shifter element 6 is connected to the 2nd antenna element 10.

1st antenna element 8 and 2nd antenna element 10 can form a series resonant circuit. Antenna elements are respectively, by being configured to have a 90° or 270° phase shift of the quarter-wave long-term phase shifter element 4, 6 is connected to the common node. Set up:

i₁ = j   Y₁   u_q;

i₂ = j   Y₂   u_q.

In this, the applied voltage in the circuit connector u_q conversion in each phase shifter element or each quarter-wave long-term at the ends of the applied current to i₁ or i₂. By selecting different lead admittance Y, can adjust any, of the variable ratio is determined. If the has extremely low internal resistance of the transmitter (voltage source 2) is connected to the circuit connector 12, that is, branch node, all current is fixedly applied to the is connected to the output terminal of the antenna element (coil). However, if with limited impedance of the power supply is connected to the circuit connector, is applied to the circuit of the common voltage of the joint, at least at the output end is also fixed to the than the current is applied. At the output end on (that is, antenna element) through the load change or inductive coupling the voltage change caused by the

i_q = j   Y₁ u₁ +j   Y₂ u₂

The change in the circuit connections and as the electric current causes voltage u_q reduced. However, the change in all antenna elements play a role. Therefore, elements of the vector of the electric current through the front of the load only by coefficient scaling, this can be by adjusting to balance the power of the transmitter.

The reference Figure 2, Figure 2 shows an antenna according to the invention circuit the 2nd principle circuit, on the basis of the electric current from the plurality of input end of the addition. 1st current source 18 will be voltage 1st u_q1 feed 1st phase shifter 4, the 1st phase shifter the current i₁ feed-in antenna side of the joint 14. 2nd current 20 the voltage u_q2 supplied to the 2nd phase shifter element 6, the 2nd phase shifter element the current i₂ provided to the antenna side of the joint 14. The current i₁ and i₂ the and the feed-in antenna element 16. Formed by this power distribution network having a plurality of input terminals. In this use the following facts, in other words, a phase shifter element or quarter-wave long-term output terminal indicating that the virtual current source, the current source can be added through the parallel circuit, but will not anti-role by each input for the current ratio.

Figure 3 shows as a power distribution network 22 a of the antenna circuit, has two input end of the or circuit side 24, 26 and three output end of the connector or antenna 40, 42, 44. Antenna element 46, 48, 50 connected to each output. In the equivalent circuit diagram by the antenna element having capacitance, inductance, resistance and an induction voltage of the series circuit. The voltage u_q1 is connected to the 1st input terminal 24 and the voltage u_q2 is connected to the 2nd input terminal 26. Distribution network 22 has a plurality of phase shifter element 28, 30, 32, 34, 36, 38. Phase shifter element 28 the 1st input end 24 and the 1st output terminal 40 is connected. Another phase shifter element 30 the 1st input end 24 and the 2nd output terminal 42 is connected to a phase shifter element and 32 will be 3rd 1st is connected with the input end of the output end. 2nd input terminal 26 via the phase shifter element 34 and the 1st output terminal 40 is connected. Furthermore, input 2nd 26 via the phase shifter element 36 and 2nd output terminal 42 is connected to the other via a phase shifter element 38 and 3rd output terminal 44 is connected. Input end 24, 26 form a circuit output end of the joint and 40, 42, 44 form the antenna side of the joint.

For output current i₁, i₂ and i₃ is the equation:

i₁ = j   Y₁₁   u_q1 +j   Y₁₂   u_q2;

i₂ = j   Y₂₁   u_q1 +j   Y₂₂   u_q2;

i₃ = j   Y₃₁   u_q1 +j   Y₃₂   u_q2.

Phase shifter element 28, 30, 32, 34, 36, 38 can provide 90° or 270° phase shift and is configured as a quarter-wave long-term.

The reference Figure 4, showing the use of the mixing device 90° circular polarization distribution network. As previously in reference to Figure 3 of the distribution network, as described in structure 22. Antenna element 46, 48, 50 arranged in a cylindrical birdcage antenna device. The antenna device can be cooled. 90° mixing device 60 is connected to the input end 24, 26. The signal is fed to the input end of the 1st as follows, the voltage and current in the signal having the same phase. The input end of the 1st 24 moves the feed-in on the signal of the 90° phase of the input signal fed to the 2nd 26. Transmitter 64 is connected to the 90° hybrid device 60 of the input end. Furthermore, 90° mixing device 60 and the impedance 62 is connected. The branch node through the only can not produce any between the phase of the output current, or with each other because the current is in-phase (90 °, -90°)or inverting (270 °, -90 °). If the phase shift of the signal to the at least two input nodes power supply, can be expressed by a superimposed the arbitrary plural value of the current ratio (komplexwertig).

The input end of the power distribution network corresponding to the classical birdcage antenna feeding port (Speisetoren) and by the sole in a conventional manner by means of the sender of the 90° hybrid device to the power supply. In the transmission of the six real in the matrix Y is the weight coefficient selected for the wire of the reciprocal of the wave impedance Z. If the weight coefficient Y should be zero, that is, the wave impedance infinite, can cancel the phase shifter element or the quarter-wave long-term. If Y should be a negative symbol, to each phase shifter element 28, 30, 32, 34, 36, 38 the use instead of 270° phase shift of 90°. Figure 4 only has the use of the three separate multi-mode feeds into the stick birdcage antenna generates circular polarization MR sending field. According to the feed voltage (0° and 90°) the plural ratio and the antenna current (0 °, 120 °, 240°) on the input end of the and the 50 ohm, for power matching the scaling of the all electric conductance, can be derived the following six wire the desired wave impedance or admittance:

Y₁₁ = 1/70 . 7   1 /    ;

Y₂₁ = Y₃₁ =-1/100   1 /    ;

Y₁₂ = 1/70 . 7   1 /    ;

Y₂₂ =-1/70 . 7   1 /    ;

Y₃₂ = 0, that is, is not connected.

Because of the limited mixing device 90° the output impedance, could not be fixed to maintain the ratio of the two input voltages from the generated in and of the ratio of the linear polarization of the antenna. Therefore, the asymmetric load lead to magnetic field polarization ellipticity. This point in the present conventional birdcage antenna was the case, by means of these birdcage antenna power supply by the transmitter of the mixing device to feed.

The reference Figure 5, in the branch of the antenna with an additional phase shifter.

As described in such as the power distribution network of structure 22 of the output end of the 1st 40 is connected with the branch of the antenna, the antenna branch has a phase shifter 72, sending and receiving converter 70, lead wire 68, matching circuit 66 and antenna element 46. It is important that, on the input end can be the distribution node (Verteilknoten) and antenna element between the adding of the (Summationsknoten) on node in the branch of the phase shifter element or quarter-wave long-term application to an arbitrary phase shifter. Can be used, for example, in practice the impedance matching network or transmitting/receiving converter is arranged in between the same. Because each of these local network should be one of the and almost (reziprok) but easy of a loss-free, so the general may be expressed as a series circuit with the impedance conversion phase shifter. In accordance with the function of this invention, can request, inserting another phase shifter device 72, so that the distribution network 22 and a series oscillation circuit of the antenna elements of each output node 40, 42 between all phase and is of 0° or 180°.

Can, for example, the antenna element 46 inaction series oscillation circuit as a parallel oscillating circuit to feed. In this final through the signal (the voltage and current) of the (near the 90°) phase shift to form a quarter-wave long-term. Therefore, in principle, can also be through two of the parallel resonant circuit directly connected in parallel circuit forced produce the same current. However, in order to to have adjustable weights of a plurality of input terminals of the current summation, must by means of a phase shifter device 72 can be revoked oscillation circuit wiring phase shift, thereby once again converted into the parallel circuit of the series circuit.

The required Figure 6 under the condition used for interpretation by the 8 × 4 antenna element structure of a two-stage distribution network of the device.

The 1st a plurality of phase shifter element 78 is connected to the 1st input terminal 74. The 2nd a plurality of phase shifter element 80 is connected to the 2nd input end 76. A plurality of phase shifter element through the 1st 78 and 2nd a plurality of phase shifter element 80 to the antenna elements for generating the desired signal and mutual decoupling. Supplying power to the antenna branches through the phase shifter element 82, 86 for a plurality of antenna elements 92, 94 the decoupling feed. Through other phase shifter element 84, 88 separating antenna element 92, 94 in each of the. Antenna device 90 is cylindrical of a 8 × 4 antenna elements, wherein the antenna element is substantially in the axial direction are connected in parallel.

For two-dimensional structure of the device for transmitting/receiving antenna extension 90 must to a large number of individual antenna elements 92, 94 the power supply. With a (arranged as the azimuth angle direction is eight times and the longitudinal to four times the) 32 in a channel of the antenna device, if the simulation typically circular polarization birdcage antenna, the should be provided with 32 of the two branches (Verteilbaum) distribution tree.

These large HF is connected to the central node of the problems will arise in practice. However, the distribution network can be layered structure. In 1st distribution layer 78, 78 in the input end of the two transmitted to eight circumferential row allocation (Umfangsreihen). For this all has eight two nodes of the wire. Subsequently each having a quarter-wave long-term eight summing node once again converted to voltage node.

Can have four phase shifter element or quarter wavelength branch 84, 88 of the 2nd layer is connected to the voltage node each, the four phase shifter or a quarter wavelength branch to the row of four antenna element 92, 94 in-phase with each other to feed. In Figure 6 it is shown in the voltage level of the node and branch all the connected in parallel there is no phase shift to each other. Phase shifter element 78, 80, 82, 84, 86, 88 can be formed to have a 90° or 270° phase shift of the quarter-wave long-term. Connected to the 1st a plurality of phase shifter element is connected to the 78 and 2nd a plurality of phase shifter element 80 of the wire form of the current node, a plurality of paths to the same phase into the current node.

Through the antenna circuit does not remove the possibility of the electric current in the antenna element of the coupling. Nevertheless, current can still be in accordance with the proportion of pre-defined flows into the single antenna element.

Figure 7 shows a circuit in accordance with the antenna of the present invention is the equivalent circuit diagram. Phase shifter element through the capacitor 202 is formed, the capacitor is connected with the input end of which is connected with the earth ground inductance 210,214. Other phase shifter element through the capacitor through the inductor 204,206,208 and 214,216,218, 220, 222,224 form. Inductance 210 and 214 is connected in parallel with the and can be integrated as the inductance 230. Inductance 218,222 can also be integrated as the inductor 232. Inductance 230 and 232 with the power-distribution network of the joint is located in the input end of the corresponding on the same electrical potential.

On the output side, the inductance 216 and 224 are connected in parallel, so it can be integrated as the inductor 236. In another output terminal, connected in parallel with the inductance 212 and 220 can be integrated as the inductance 234. That is, the inductor 234 and 236 is connected to the output terminal or is connected to the power distribution network is connected with the output end of the wire.

Therefore a high-pass ∏ assembly is connected to the phase shifter to generate branch the realization of special low-overhead. N M to the distributor only need to assign M×N capacitor. In this each weight coefficient, the admittance Y, to Y=2 πfC through the capacitor according to a predetermined. Located in each phase shifter element on the input end and the output end of the shunt inductance can be combined, thus only required inductance M+N.

US7573036 similar to the system shown in the as Peru Time, capacitance for example can be implemented as a double-sided circuit board. In this will be connected to the supply node of the conductor lines extending one side of the conductor and current adding node extends on the other side of the circuit. The corresponding weight coefficient realized as having the coupling capacitance of the adjustable level or surface is located between the hole (Schirmlage) of the shielding position.

Figure 9 shows two connected with the balanced-to-unbalanced converter power distribution network. By means of a balanced-to-unbalanced converter 240 (the balanced-to-unbalanced converter is provided with 180° phase shift of the phase shifter), each in a power distribution network can also be realized on the input signal of the opposite phase. Figure 9 essentially corresponds to the circuit structure of the Figure 8 circuit structure, the capacitor 238 said phase shifter element, inductor 244,246 said phase shifter element the input side of the parallel circuit of the inductor inductance and 248,250,252 said phase shifter output of the component side of the parallel circuit of the inductor. Inductance 244,246 are respectively connected to balanced-to-unbalanced converter 240, 242 of the output end.

To arrive at a 2 × M and N input end of the adding node power distribution network. Weight coefficient can be through a pair of inverting input terminal is connected to the coupling capacitance of the determined difference, wherein the two the same capacitor 238 in weight coefficient is zero.

For signal distribution of the known structure is Butler matrix, the matrix not only allow excitation two circular polarization birdcage fundamental mode, also allows the excitation has higher oscillation frequency of all of the higher order mode.

N is Butler matrix input port and the output port N substantially similar between the Fourier transform. According to   Gundlach Meike, technical manuals HF, Butler matrix is professional known by the public. Butler matrix with basic function corresponding to the Plural value of the FFT, and the establishment of a complex value (Strombelegung) current distribution. On the contrary is real value Fourier transform, use of or As the basic function. Therefore, the corresponding switch matrix with sin or cos amplitude weighted output signal, and the output terminal of the is not generated between 0° or 180° different phase.

N is in the circumferential direction the number of antenna element is on the, for example 8 or 12 or 16. This is also possible in principle the number of Fourier modes. M means the operation of the circumferential mode number. For example M=1 is rotated to the left the uniform birdcage mode, and M=-1 is of rightward rotation uniform birdcage mode. Higher mode has more of short cycle on the space in the direction of the current and hence field less penetration in the target. In order to reduce the number of the transmitter, in practice a excitation only a subset of the possible models N meter

As plural value fast Fourier transform (FFT) implementation of the similar, N input end and the output end has a need of Butler matrix N/2 ×ld (N) an overhead of mixing device 90°. Butler matrix corresponding to the input end of a plurality of current distribution Has been generated the current distribution with different azimuth angle and the radial direction of the circular pole melts the field of the structure. supply network in accordance with the present invention by means of the discrete Fourier transform in real terms can be realized, the method is, according to the or To choose the current weight. In order to simulation the channel N of Butler matrix, is the preamplifier N mixing device 90° is connected to the one and the same, with 2N N output end and input end of the power distribution network. For 2 × N×N N power in order to of the first rising expenses for than higher of the Butler matrix. For this, through each branch only one capacitor and the minimal overhead.

If not all N one mode is excited, which is a transmitter control N M<N may be a subset of the mode, can reduce the defect. On the other hand, what is more important is, the mode is not used to form the input end, so that then will be a short circuit. This can be realized through the asymmetric load can be suppressed as much as possible with higher local oscillation frequency of the inductive current component not expected. The current is applied to the model in addition, real value Fourier supply network is another advantage of the: in a multi-channel feed case each mode is matched with the input, each input can be matched with the corresponding transmitter individually.

The reference Figure 10, Figure 10 to explain how the antenna circuit can be used in the received signal. Figure 10 shows a distribution network described in front of the antenna element 22 and 46, 48. The antenna element 46, 48 of the received signal by the phase shifter element 28, 30, 34, 36 is guided to the circuit node 24, 26, amplifier 302,303 are respectively connected to the antenna node. Set up:Z_in <<Z_opt. In accordance with the present invention with regard to produce the 90° or 270° phase shifter shifting the phase of the parallel circuit of the circuit is not only applicable for the antenna of the transmitter assigned to the antenna element 46, 48, and can be used for forming linear combinations of the received signal. For example, when a larger number of antenna element signal through a relatively small number of receiver to processing, with the advantages of this point. Another advantage is that, because the same electrical length is in the output end and each connected to the input terminal of the same, can also use a common preamplifier decoupling, that is, through a pre-amplifier, the input impedance to attenuate the resonance of the antenna. Only must the necessary to ensure that using an additional phase shifter device for branch node or circuit connector 24, 26 of the pre-amplifier 302,304 expressed with the signal source 46, 48 compared with the impedance of the low impedance.

Finally, it is indicated, and the description of this invention of the embodiment of the present invention, in principle, not limited to the specific physical implementation. For the professional in particular, it is obvious that, the invention can be partially or completely in software and/or hardware and/or for a plurality of physical products (in this especially computer program product) to realize the distributed on.

The Figure mark list

2   voltage source

4   1st phase shifter element

6   2nd phase shifter element

8   antenna element

10   antenna element

12   circuit connector

14   antenna side joint

16   antenna element

18   1st voltage source

20   2nd voltage source

22   power distribution network

24   1st circuit connector

26   2nd circuit connector

28   phase shifter element

30   phase shifter element

32   phase shifter element

34   phase shifter element

36   phase shifter element

38   phase shifter element

40   1st antenna side joint

42   2nd antenna side joint

44 line side joint   3rd day

46   1st antenna element

48   2nd antenna element

50   3rd antenna element

52   capacitance

54   inductance

56   impedance

58   induction voltage

60     90° mixing device

62   terminal impedance

64   transmitter

66   matching circuit

68   leads

70   sending and receiving converter

72   phase shifter device

74   input end

76   input end

78   a plurality of phase shifter element

80   a plurality of phase shifter element

82   phase shifter element

84   a plurality of phase shifter element

86   phase shifter element

88   a plurality of phase shifter element

90   antenna device

92   a plurality of antenna elements

94   a plurality of antenna elements

102   antenna element

104   sends the receiving converter

106   power distribution network

108   transmitter

110   receiver

200   distribution network

202   capacitance

204   capacitance

206   capacitance

208   capacitance

210   inductance

212   inductance

214   inductance

216   inductance

218   inductance

220   inductance

222   inductance

224   inductance

230   inductance

232   inductance

234   inductance

236   inductance

238   capacitance

240   1st balanced-to-unbalanced converter

242   2nd balanced-to-unbalanced converter

244   inductance

246   inductance

248   inductance

250   inductance

252   inductance

302   amplifier

304   amplifier