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

Definitions

• the present invention relates to a Wilkinson coupler integrated into a printed circuit and to a microwave device comprising such a coupler. It applies in particular to the field of telecommunications of microwave signals such as in particular radiofrequency channels and beam forming networks of transmitting and receiving antennas, for example antennas placed onboard a satellite.
• this type of coupler comprises three ports 1, 2, 3 constituting, in the divider configuration, an input port 1 and two output ports 2, 3, the input and output ports. output being reversed in the case where the coupler is used in combiner configuration.
• the coupler is terminated by a load resistor Rc mounted between the two output ports 2, 3.
• the value of the load resistor Rc is determined so that the coupler is balanced and there is no reflection in entry or exit.
• some equipment such as beamforming networks need the value of the load resistance to be accurate to between 1 and a few percent.
• the brazing material must be brought to a high brazing temperature which is difficult to achieve on an organic substrate such as the dielectric of a multilayer printed circuit; for example, the brazing temperature is of the order of 290 ° Celsius for a brazing material made of a gold-tin alloy compatible with gold endings of such resistors.
• the brazing temperature is of the order of 290 ° Celsius for a brazing material made of a gold-tin alloy compatible with gold endings of such resistors.
• This process is complex and expensive to implement and presents quality risks especially as these operations must generally be performed for a very large number, for example of the order of a thousand, individual resistors.
• the total thickness of the printed circuit obtained is greatly increased because of the thickness of the electronic component to be embedded in enough dielectric material.
• the object of the invention is to provide a Wilkinson coupler integrated in a printed circuit not having the disadvantages of existing devices, not requiring the machining of metallized holes in the printed circuit for the measurement of the load resistance and having a load resistor whose value can be adjusted with a required accuracy and measured during its adjustment.
• the invention relates to a Wiikinson coupler mounted on a printed circuit comprising a first access port connected to a second and a third access port via two metal transmission lines of the same length and a resistor. load circuit short-circuited between the second and third access ports, characterized in that the load resistor consists of three adjacent independent resistors interconnected.
• each resistor has an adjustable and measurable value individually.
• each resistor is measurable during the adjustment.
• the three independent resistors are connected via two transverse metal tracks, each transverse metal track being disposed between two adjacent resistors.
• the first resistor is connected between a first end metal terminal connected to a metal access line to the third port and the first transverse track and in that the third resistor is connected between the second transverse track and a second one. end metal terminal connected to a metal line for access to the second port.
• the first and second end metal terminals are interconnected via the two metal transmission lines connected to the first port, the two transmission lines forming a metal track connected in a loop.
• the three independent resistors are connected in a triangle.
• the three independent resistors have an identical value equal to one third of the value of the desired load resistance.
• the invention also relates to a microwave device comprising at least one such Wilkinson coupler.
• FIG. 1 a diagram of an example of a Wilkinson coupler, according to the prior art
• FIG. 2 a diagram of an example of a Wilkinson coupler, according to the invention.
• FIG. 3 a diagram of an enlargement of the load resistance of the Wilkinson coupler of FIG. 2, according to the invention
• FIGS. 4a to 4c an example of the power curves in transmission and in reflection on the three ports of a coupler, according to the invention
• FIG. 5 an example of a circuit diagram of a device for measuring the load resistance of a Wilkinson coupler, according to the invention.
• FIG. 6 an example of a microwave device comprising two Wilkinson couplers.
• the coupler example according to the invention diagrammatically shown in FIG. 2 comprises three ports 1, 2, 3 constituting, in the divider configuration, an input port 1 and two output ports 2, 3.
• the coupler and the load resistor are made by a known photolithograph process on a multilayer printed circuit comprising a substrate covered with a resistive layer and a metal layer, for example copper.
• a first etching makes it possible to make the transmission lines of the coupler and a second etching makes it possible to realize the load resistance of the coupler.
• the load resistance Rc short-circuited, must be able to be precisely measured and adjusted.
• the load resistance Rc of the coupler consists of an array of three adjacent resistors R1, R2, R3 separated by means of two transverse metal tracks 9, 10, the metal being able to be example of copper.
• a first resistor R1 is connected between a first end metal terminal 11 connected to a metal port access line 12 and a first transverse track 9, a second resistor R2 is connected between the first transverse track 9 and a second track 10, the third resistor R3 is connected between the second transverse track 10 and a second end metal terminal 13 connected to a metal line 14 for access to the port 2.
• first and the second end metal terminals 11, 13 are interconnected via the two transmission lines 4, 5 connected to the port 1, the two transmission lines 4, 5 forming a metal track connected in a loop.
• Each of the resistors R1, R2, R3 of the resistor network has an intrinsic value such that the sum of the values of the three independent resistors R1, R2, R3 is equal to the value of the load resistor Rc.
• the three resistors R1, R2, R3 may be identical and have a value equal to one third of the value of the load resistor Rc.
• R2, R3 makes it possible to change nothing from the point of view of the microwaves supplying the coupler, the three adjacent resistors R1, R2, R3 acting as a single resistor Rc short-circuited whose value is equal to the sum values of the three resistant. Because of the short circuit, the three resistors R1, R2, R3 can be considered as a network of resistors connected in a triangle. The influence of the splitting of the load resistor Rc into three resistors R1, R2, R3 on the performance of the coupler was verified by simulations.
• FIG. 4a shows that the reflection coefficients S11, S22, S33 of a signal applied respectively to the ports 1, 2 or 3 are very small at the central operating frequency of the coupler.
• the coefficient S11 is of the order of -48 dB at the frequency of 1.6 GHz. Therefore, when a signal is applied to the input port 1, there is no reflection of this signal which is fully transmitted to the ports 2 and 3.
• FIG. 4b shows that at the operating frequency, the signal transmission coefficients S23 from port 2 to port 3 and reciprocally S32 are virtually zero. Ports 2 and 3 are perfectly isolated from each other.
• FIG. 4c shows the transmission coefficients S21 and S31 between ports 1 and 2 and between ports 1 and 3.
• the power transmitted between outputs 2 and 3 and input 1 are almost equal, which means that the coupler is properly balanced.
• the difference observed between the two curves is due to divergences in calculation of the simulator used.
• the splitting of the load resistor Rc into three adjacent resistors and the addition of two metal tracks 9, 10 between two adjacent resistors R1, R2 and R2, R3 allows to be able to connect a metal connecting pin on each of the two transverse tracks 9, 10 and a metal pin on one of the tracks 11, 13 bypassing the load resistor Rc. It then becomes possible to connect a measuring device, for example of ohmmeter type, between the three connection terminals 11, 9, 10 and accurately measure, successively, the value of each of the three resistors R1, R2, R3.
• the guard point is the point A located between a first resistor R1 and a second resistor R2 and the resistance measured is a third resistor R3.
• the resistor R3 has a first end connected to the resistor R1 at a point B and a second end connected to the resistor R2 at a point C.
• a current source I is applied to the point B.
• a guard amplifier G having a first input connected to the point B, a second input connected to the point A and an output connected to the point A, detects the voltage at the first end B of the resistor R3 and applies this voltage to the guard point A. The voltage at the guard point A and at point B are then equal and there is no current in the resistor R1.
• the resistors R3 and R2 then form a conventional measuring bridge. If Im is the current flowing in the resistor R3, the current Ig that flows in the resistor R2 is such that:
• An amplifier 20 connected between points B and C makes it possible, at its output at point C, to reduce a voltage proportional to a current I which is injected at point B and which passes through resistor R3.
• a converter 21 determines the value of the resistor R3 by virtue of the ratio between the voltage at the point C which it measures and the value of the known current I.
• the value of the resistor R1 can be determined in the same way by permutating the guard point and the measuring points.
• the value of each of the resistors R1, R2, R3 can then be adjusted independently of the other two resistances to have a total resistance having a value equal to the desired load resistance value Rc. It is also possible to independently measure each of the resistors R1, R2, R3 and to adjust only one.
• the adjustment of the value of the resistors can be achieved by a known method of adjustment by laser beam, the measurement of the resistance during adjustment being carried out continuously during the adjustment of this resistance.
• the laser may be similar to those used for adjusting thin film resistors or thick layers. Its wavelength may for example be chosen to be of the order of 1.07 micrometers.
• the power of the laser beam is programmed according to the material to be adjusted and the support of the resistance.
• the support of the resistor may be for example ceramic material, or organic, or another type of material usually used in the field of printed circuits.
• the Wilkinson coupler can be used in any type of microwave device such as, for example, in the equipment of the radio frequency transmission and reception of telecommunication signal chains, in particular in the beam forming networks of the multi-beam antennas or in the linearization modules which equip amplification circuits of the telecommunication signals.
• FIG. 6 shows a diagram of a linearizer comprising two Wilkinson couplers 61, 62.
• the first coupler 61 is a divider of the power of the input signals between two channels 63, 64 of FIG. output transmission while the second coupler 62 recombines the power of the processed signals on each of the channels into a single output signal.

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• Non-Reversible Transmitting Devices (AREA)
• Microwave Amplifiers (AREA)

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• 2009
  • 2009-07-07 FR FR0903345A patent/FR2947959B1/fr active Active
• 2010
  • 2010-06-21 WO PCT/EP2010/058707 patent/WO2011003724A1/fr active Application Filing
  • 2010-06-21 JP JP2012518866A patent/JP2012532550A/ja active Pending
  • 2010-06-21 US US13/377,562 patent/US20120098617A1/en not_active Abandoned
  • 2010-06-21 EP EP10725754A patent/EP2452394A1/de not_active Withdrawn

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