DE102008005204A1 - Directional coupler for a phase-independent power measurement, comprises coupling loss in forward direction and coupling loss in backward direction - Google Patents

Abstract

The directional coupler (20) comprises a coupling loss in a forward direction and the coupling loss in a backward direction. A decoupling occurs in the forward direction and the backward direction. Bypasses (291,292) are connected to impedance arrangements (210,230) with a changeable impedance, particularly ports (3,4). An independent claim is also included for a method for adjusting a directional coupler with a coupling loss in a forward direction.

Description

The The invention relates to a method for adjusting a coupling factor and / or a directivity of a coupler, as well as a coupler arrangement with at least one coupler having a plurality of ports, wherein at least a port connected to a variable impedance arrangement is.

One Coupler is a passive electronic multi-port component that has a at a port (gate) arriving electromagnetic wave in certain Ratio and with certain phasing to a part or distributed all of its ports. A coupler for conducted Shafts can be coaxial in a shielded housing, implemented in stripline technology or in two-wire technology become.

3-dB coupler or power dividers are available in the usual versions "in-phase" (in-phase) and 90 °, which are incident on a port (X1) electromagnetic Wave in equal parts on two other ports (X2, X3) in phase, or shifted by 90 °, spend, while a possibly existing fourth Port (X4) is isolated from on at the first port (X1) signals.

directional coupler give the most part to a port (X1) incoming wave at a second port (X2) while off a comparatively small part on a third port (X3) and optionally output at a fourth port (X4). Such a Four-port directional coupler usually consists of a main line with two ports (ports) X1, X2 and a secondary line with likewise two connections X3, X4, which in a certain geometric arrangement to each other.

In such a directional coupler branches a part of the on a main line ongoing electromagnetic wave from the secondary line, wherein the coupling is directional, d. H. one at the first port (X1) coupled electromagnetic wave is mainly running to the second port (X2). Part will be after the corresponding one Nebenleitungsport decoupled.

The The following considerations relate specifically to a four-port directional coupler with a wave entering at a first port X1, although it does modified for all types of couplers and for all types of feed are valid.

• 1. den (Aus-)koppelfaktor (coupling factor) C = P3/P1 (1)der den am korrespondierenden Nebenleitungsanschluss X3 ausgekoppelten Anteil (P3) der bei X1 einlaufenden Welle (P1) bestimmt,
• 2. die Isolation I = P2/P3 (2)die die Leistung einer unerwünschten Kopplung beispielsweise einer bei X2 einlaufenden Welle (P2) zum nicht korrespondierenden Nebenleitungsanschluss X3 bestimmt und
• 3. das Vorwärts-Rückwärts- oder Richtverhältnis (directivity) D = (P3/P1)/(P4/P1) = P3/P4 (3)das angibt, inwieweit eine an einem Anschluss (X1) der Hauptleitung eingespeiste elektromagnetische Welle nur auf dem korrespondierenden (X3), nicht jedoch auf dem zweiten Nebenleitungsabschluss (X4) zu beobachten ist.

A directional coupler is mainly characterized by:

• 1. the coupling factor C = P3 / P1 (1) determining the proportion (P3) of the wave (P1) arriving at X1 at the corresponding bypass line X3,
• 2. the isolation I = P2 / P3 (2) which determines the power of an undesired coupling of, for example, a wave (P2) arriving at X2 to the non-corresponding bypass line X3, and
• 3. the forward-reverse or directivity D = (P3 / P1) / (P4 / P1) = P3 / P4 (3) This indicates to what extent an electromagnetic wave fed in at one connection (X1) of the main line can only be observed on the corresponding (X3) but not on the second secondary line termination (X4).

One Directional coupler is often used from the to the Secondary terminals decoupled electromagnetic waves a measurement for those transmitted on the main Determine performance. This can be done via a secondary connection a measure of that in a first direction about the main transported power, for example the forward power of a power generator to a load, coupled or determined become. Accordingly, via a second auxiliary connection a measure of that in a second direction about the main transported power, such as the reflected power or reverse power from a load to a power generator, be decoupled or determined. Abbreviated one speaks that the ancillary lines or reverse power is coupled out.

typical Applications for the decoupled power are more Signal processing steps or measurement purposes. The measuring device can work directly on the frequency of the electromagnetic wave. It is also common to use the decoupled high-frequency Rectify voltage and only the resulting DC voltage or to measure the resulting direct current.

Coaxial for electromagnetic waves have a usual System resistance (also called system impedance or nominal impedance) Z0 of 50 Ω real or 75 Ω real. An impedance is a generally complex AC resistor.

A designed and built for a particular system impedance coupler for a coaxial system will only work optimally if it at all its connections with sources, eg. B. a power generator, or sinks, z. As a load abge is closed, which have the system impedance. If this is not the case, the decoupling factor varies and the directivity ratio becomes poor. If the second port of the secondary line is not required in a directional coupler, since only one direction of the waves on the main line is to be measured, this can also be provided with a terminator of the size of the system impedance.

Around the mutual action of two measuring devices attached to the Secondary line for measuring the forward and reverse power double directional couplers are common, whose two secondary lines each feed only one measuring device, wherein the unused secondary line connection with the system impedance is completed.

at a required bandwidth is the design of the directional coupler geometry always a certain compromise, so that the properties mentioned never be ideal and consistent across the entire bandwidth become. In addition, manufacturing tolerances still go with a real component a, which influence the coupling factor and the directivity.

In Many high-frequency systems are interested in getting an optimal one Power transmission from a source (transmitter, radio frequency generator) on a load or sink (for example, an antenna or a plasma chamber as a load). For measuring the forward power and the reflected power becomes a directional coupler in the transmission line inserted. The accuracy of the measurement depends on the non-ideal values for the coupling factor C and the Directivity D of the directional coupler used. give way Also, the impedances of source or load from the nominal impedance from, so are the results of the measurements on the directional coupler, in particular the measurement of the power reflected from the load by observation the decoupled by the directional coupler power at the corresponding Connection of the secondary line, in addition to the correct value differ.

1a shows a high frequency system 1 in the prior art with a high frequency generator 100 as a source, a coupler arrangement 2 with a coupler designed as a directional coupler 200. as well as a load 300 as a sink. The coupler has a main line 290 with a first and second port 201 . 202 as well as a secondary line 291 with a third and fourth port 203 . 204 that with resistances 205 . 206 are completed, the nominal impedance Z0 of the high frequency system 1 or at least that of the coupler 200. correspond. At the port 203 can with a meter 207 a share of the corresponding port 201 the main line 290 incoming wave are observed; according to the port 204 a proportion of the load reflected and at the corresponding port 202 the main incoming wave with a meter 208 to be watched. The size of the share depends on the coupling factor. In an ideal coupler, the directivity is infinitely large, and it will be on the port 203 no share of the port 202 incoming wave and at the port 204 no share of the port 201 be observing incoming wave.

1b also shows a high frequency system 10 , The coupler 240 has two secondary lines 291 . 292 on. At the port 203 the first secondary line 291 will be a share of the port 201 the main line 290 fed shaft measured at the port 224 the second secondary line 292 will be a share of the port 202 the main line 290 fed wave measured. The ports 223 . 224 the second secondary line 292 are due to the impedances 225 . 226 completed, which correspond to the nominal impedance Z0.

It is known that some adjustment of the secondary line terminations can improve the matching and directivity of the directional coupler in a very narrow frequency range for a particular situation ( Michael G. Ellis, RF Directional Couplers, ANTEC, http://michaelgellis.tripod.com/direct.html ).

Out DE 101 215 35 A1 a directional coupler circuit for measuring the transmitter power is known in which the terminating impedance of the unused port of the secondary line is chosen so that the directivity of the directional coupler is improved. This improvement should occur over a frequency range. As the terminating impedance, a two-pole with a frequency-dependent change of the complex resistance value over a frequency range is proposed, such as, for example, capacitances or inductances in connection with real resistances. Further, as the impedance transformation member, a line piece having a certain length connected between the port and the two-terminal is called.

In US 4,644,260 is described a directional coupler, in which also by changing the terminating impedance of the unused port of the secondary line whose standing wave ratio and thus the directivity of the measurement is improved. This is also done by a coaxial line of certain length or by a variety of matching networks. Although the length of the coaxial cable can also be varied here for the purpose of adaptation, this is done by tests.

It is an object of the invention to provide a method and to design a coupler arrangement such that the coupler arrangement also has a non-ideal coupler having frequency-dependent characteristics and / or manufacturing tolerances and / or a constant coupling factor and an optimal directivity in the case of source and drain impedances which deviate from the system impedance ,

• a. Anschließen einer Impedanzanordnung an zumindest einen Port des Kopplers, deren Impedanz durch zumindest ein elektronisches Steuersignal veränderbar ist;
• b. Ansteuern der Impedanzanordnung mittels eines elektronischen Steuersignals derart, dass Auskoppelfaktor und/oder Richtverhältnis des Kopplers verbessert werden.

This object is achieved by a method for setting a coupling factor and / or a directivity of a coupler, with the method steps:

• a. Connecting an impedance arrangement to at least one port of the coupler, the impedance of which can be changed by at least one electronic control signal;
• b. Controlling the impedance arrangement by means of an electronic control signal such that the coupling factor and / or directivity of the coupler are improved.

the apparatus, the problem is solved by a coupler arrangement with at least one coupler having a plurality of ports, wherein at least a port, a variable impedance impedance device connected. In this case, the impedance of the impedance arrangement is through an electronic control signal changeable. The impedance The impedance arrangement may be one or more individual ones Assemble impedances, wherein a single impedance of the impedance arrangement by one or more components, each having an impedance, can be formed.

variants of the method and embodiments of the coupler arrangement from the dependent claims.

at The coupler of the coupler arrangement may be a coupler for line or waveguide guided electromagnetic waves, especially those for measurement purposes, act. In particular, it can be a directional coupler. For example The coupler can be used as a 3 dB coupler, either as "in-phase" or 90 ° 3 dB coupler be formed.

The Wiring of at least one port of the coupler can be designed be that it consists of a variable impedance arrangement, whose impedance is changed by electronic control signals can be. For a directional coupler used for measurement purposes can not for that occupied by the meter Secondary line port can be used.

By the electronically variable impedance of the impedance arrangement can The decoupling factor and the target ratio of the coupler are optimized become. The impedance arrangement may comprise one or more elements wherein the impedance of the entire arrangement or at least one element the arrangement is variable by the control signal.

If by the control signal only the impedance of a single element or a group of elements is changed, of course also changes the total impedance of the impedance arrangement.

Of the Graduation, d. H. the impedance arrangement can be made of a real resistor and a capacitance diode. A control voltage as an electrical control signal to the capacitance diode can change their capacity.

The Impedance arrangement may alternatively or additionally a Inductance have. An electronically controllable or controllable inductance and thus controllable impedance can For example, be achieved by the permeability of the coil core of the inductance is lowered by by an additional magnetic DC field, which with generated by a direct current flowing auxiliary winding is, the magnetic flux against the saturation limit of the core material. As electronically changeable, So changeable by an electronic control signal real resistance can be used, for example, a PIN diode become.

Around both real and imaginary resistance values for to adjust the connected to a port impedance arrangement can, the impedance arrangement can be at least two influenceable Have impedances, which are connected to the port, which on the complex resistance level does not collinear. This means, that the pointers or vectors represent the impedances in the resistance plane describe, are not linearly dependent. Such Impedance arrangement, for example, a circuit consisting from a capacitance diode and a PIN diode.

The electronically variable impedance can be dependent from the operating frequency of the system in which the coupler is incorporated is, for example, the fundamental frequency of an HF power generator, depending on the impedance of at least one of the Coupler connected source or sink and / or depending set by the real characteristics of the manufactured coupler become.

For more complex tasks, for example, the compensation of impedances connected to two main ports of a directional coupler, which deviate from the system impedance, both ports of the secondary line of this directional coupler or, correspondingly, a port of two secondary lines can also be used connected to impedance arrangements with controllable by an electronic signal impedances.

at the dimensioning of the ranges of variation of the controllable variable Impedances may be the characteristic of the directional coupler in the intended working frequency range as well as the range of possible impedance variation of the connected Sources and sinks are taken into account.

The Control voltages for at least one electronically variable Impedance can come from an electronic circuit the current operating status of the device and thus the connected impedances on at least one port of the main line, the current working frequency and the frequency-dependent Behavior and / or given by the production of real characteristics of the at least one inserted coupler knows.

The Circuit can be analog or digital and also contain a microprocessor. The circuit can be a memory contain or can access a memory containing the parameters for certain impedance values at a port of the secondary line, for the compensation, for the frequency-dependent Behavior or for the individual characteristics of the Kopplers or for other operating conditions High frequency system includes.

Of the Memory can be a permanent memory used in production described and / or installed in the device. alternative or additionally, the memory may be a writable memory be new, for example, during a calibration process is described.

Of the Calibration can be done by means of a control circuit, which measures the signals on at least one port of the coupler while the Control voltages for the electronically variable impedances be managed. In doing so, the above-mentioned circuit be used as a control circuit.

The Ratio of the coupler in a given state the connected loads and sources is best if at the respective non-corresponding port of the secondary line emerging wave is minimized, d. H. when the standing waves on the secondary line of the coupler are minimal. Is the coupler arrangement calibrated so, the parameters for the electronic variable. Impedances are taken into the memory. This also low impedance changes of observed at the coupler sources and sinks are observed.

The electronic circuit can also work as a permanent scheme. In a first step, all parameters can be set in this way or the scheme be operated so that an optimal behavior of the Directional coupler arrangement occurs, so for example, a very high Directivity. The control loop should now have a low-pass characteristic whose cutoff frequency is lower than the expected change the impedances of the connected sources and sinks at the coupler are connected. Change the conditions now the impedances of the sources or sinks, so the scheme does not can follow so quickly, so that the directional coupler arrangement due to the high directivity the impedance changes can play very accurately.

Further Features and advantages of the invention will become apparent from the following Description of embodiments of the invention, based on Figures of the drawing which show details essential to the invention, and from the claims. The individual features can each individually or in any combination be realized in a variant of the invention.

preferred Embodiments of the invention are in the drawing shown schematically and are described below with reference to the Figures of the drawing explained in more detail. It shows:

1a . 1b in each case a high-frequency system with coupler arrangements according to the prior art;

2 a schematic representation of a high-frequency system with a coupler arrangement and an impedance arrangement;

3 an embodiment of an impedance arrangement.

In the figures become the same components Reference numeral used.

2 shows a high frequency system 20 with a high frequency generator 100 as a source, a coupler arrangement 3 with a coupler designed as a directional coupler 240 as well as a load 300 as a sink. The coupler 240 has a main 290 with a first and second port 201 . 202 as well as a secondary line 291 with a third and fourth port 203 . 204 , The port 203 is with a resistance 205 completed, the nominal impedance Z0 of the high frequency system 20 or at least that of the coupler 240 equivalent. At the port 203 can with a meter 207 a share of the corresponding port 201 the main line 290 incoming wave can be observed.

Furthermore, the coupler has 240 a second secondary line 292 with a fifth and sixth port 223 . 224 on. At the port 224 the second secondary line 292 will be a share of the port 202 the main line 290 fed wave measured. This is a measuring device 228 to the port 224 connected. The port 224 the second secondary line 292 is through the resistance 226 completed, which corresponds to the nominal impedance Z0.

The drawn in the figures measuring instruments 207 . 228 may each be voltmeters, oscilloscopes or the like or analog or digital evaluation circuits with or without prior rectification of the wave. Furthermore, the input impedances of the measuring devices can replace the terminating impedances attached to the same port or, together with these, form the impedance present at the port.

The ports 203 . 204 . 223 . 224 the secondary lines 291 . 292 are also called secondary ports.

In 2 exists at the port 204 According to the invention connected impedance arrangement 210 from two electronically controllable impedances 211 . 212 which do not interact collinearly in the complex resistance plane. By supplying a control voltage from the electronic circuit 250 can these two impedances 211 . 212 be tuned, which port 204 is completed with a specific, set complex resistor. This means that through the circuit 250 the total impedance of the impedance arrangement 210 can be adjusted, resulting from the impedances 211 . 212 composed.

Symmetrical to the port 204 is port 223 with an impedance arrangement 230 consisting of two impedances 231 . 232 completed, also from the electronic circuit 250 be controlled.

The electronic circuit 250 receives further information, such as the frequency-dependent behavior of the coupler 240 , the current operating frequency of the generator 100 , the frequency-dependent complex internal resistance of the generator 100 and the frequency-dependent impedance of the load 300 , The static quantities, such as the frequency-dependent behavior of the coupler 240 or the frequency-dependent impedance of the generator 100 or an antenna as a load 300 can be stored in a memory. This can be done in digital or analog form. The memory may be permanent or rewritable. The memory can be in the circuit 250 contained or arranged externally. In the embodiment shown, the memory 251 in the circuit 250 arranged.

In one embodiment of the invention, the coupler assembly 3 calibrated. These are the measuring devices 207 . 228 with the electronic circuit 250 connected a low pass filter 252 having. At a frequency of the generator 100 or over a certain frequency range and under certain external conditions, such as a defined ohmic resistance or a faultless antenna as a load 300 become the impedances 211 . 212 . 231 . 232 each controlled so that the desired measurements on the ports 203 and 224 issue. These drive values are stored in the memory 251 stored and used in normal operation. If the working conditions deviate from the default, the measured values at the ports become 203 and 224 very sensitive to it.

In an embodiment of the invention, not shown, only one secondary line of the coupler 240 equipped with the variable impedances, ie, only one secondary line is an impedance arrangement 210 . 230 connected. However, it can be an impedance arrangement at both ports of the secondary line 210 . 230 be connected.

In one embodiment of the invention, a coupler 200. with only one secondary line 291 be provided. It can be connected to both ports of the secondary line 291 each an impedance arrangement 210 . 230 be connected. However, it can also be an impedance arrangement only to one port 210 . 230 be connected.

3 shows an embodiment for the impedance arrangement 210 , At the port 204 the secondary line 291 is a couple 213 of two antiserially arranged capacitance diodes 217 . 218 connected to ground, depending on the out of the electronic circuit 250 coming control voltage, which is at the central point or connection point of the pair 213 is set to represent a more or less large capacity. Via an inductance 214 is another couple 215 antiserial capacitance diodes 219 . 220 as well as a real resistance 216 to the port 204 connected, whose second pole is grounded. By a control voltage at the central point of the diode pair 215 also from the electronic circuit 250 can come, also the capacity of this pair 215 to be influenced. The inductance 214 , the variable capacitance of the diode pair 215 and the parallel resistance to the capacitance 216 Together they form an impedance that is not collinear in the complex resistance plane to the capacitance of the diode pair 213 is. It follows that the impedances of an impedance arrangement can each be made up of a plurality of components.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10121535 A1 [0018]
• US 4644260 [0019]

Cited non-patent literature

• Michael G. Ellis, RF Directional Couplers, ANTEC, http://michaelgellis.tripod.com/direct.html [0017]

Claims (24)

Method for setting a coupling factor and / or a directivity of a coupler ( 200. . 240 ), with the process steps: a. Connecting an impedance arrangement that can be changed by at least one electronic control signal ( 210 . 230 ) to at least one port ( 204 . 223 ) of the coupler ( 200. . 204 ); b. Driving the impedance arrangement ( 210 . 230 ) by means of an electronic control signal such that the coupling factor and / or directivity of the coupler ( 200. . 240 ) be improved. Method according to claim 1, characterized in that the impedance arrangement ( 211 . 230 ) to a secondary port ( 204 . 223 ) is connected. Method according to claim 1 or 2, characterized in that the impedance arrangement ( 210 . 230 ) is driven with a control voltage. Method according to one of the preceding claims, characterized in that at least two by at least one electronic control signal variable impedances ( 211 . 212 . 231 . 232 ) to at least one port ( 204 . 223 ) and the impedances ( 211 . 212 . 231 . 232 ). Method according to one of the preceding claims, characterized in that the impedance of the impedance arrangement ( 210 . 230 ) depending on the operating frequency of a system in which the coupler ( 200. . 204 ), depending on the impedance of at least one of the couplers ( 200. . 204 ) connected source ( 100 ) or sink ( 300 ) and / or depending on the real characteristics of the coupler ( 200. . 204 ) is set. Method according to one of the preceding claims, characterized in that the operating state of the system into which the coupler ( 260 . 240 ), the operating frequency of the system and / or the frequency-dependent behavior of the system is detected and / or stored. Method according to one of the preceding claims, characterized in that the characteristic of the coupler ( 200. . 240 ) is stored. Method according to one of the preceding claims, characterized in that a calibration process is carried out by signals on at least one port ( 203 . 224 ) of the coupler ( 200. . 240 ), while the control signal (s) for the impedance (s) are controlled in such a way that the desired behavior of the coupler ( 200. . 240 ) entry. Method according to one of the preceding claims, characterized in that a frequency-dependent calibration curve is produced. Method according to one of the preceding claims, characterized in that the impedances ( 211 . 212 . 231 . 232 ) of the impedance arrangement ( 210 . 230 ) are constantly controlled or regulated so that the desired behavior of the coupler ( 200. . 240 ) occurs. Coupler arrangement ( 3 ) with at least one coupler ( 200. . 240 ), which has multiple ports ( 201 . 202 . 203 . 204 . 223 . 224 ), wherein at least one port ( 204 . 223 . 203 . 224 ) an impedance arrangement ( 210 . 230 ) is connected with variable impedance, characterized in that the impedance of the impedance arrangement is variable by an electronic control signal. Coupler arrangement according to one of the preceding claims, characterized in that an electronic circuit ( 250 ) for controlling the impedance arrangement ( 210 . 230 ) is provided. Coupler arrangement according to one of the preceding claims, characterized in that the electronic circuit ( 250 ) a memory ( 251 ). Coupler arrangement according to one of the preceding claims, characterized in that the electronic circuit ( 250 ) is designed as a control circuit. Coupler arrangement according to one of the preceding claims, characterized in that the control circuit comprises a low-pass filter ( 252 ). Coupler arrangement according to one of the preceding claims, characterized in that the electronic circuit ( 250 ) is designed as a digital or analog circuit. Coupler arrangement according to one of the preceding claims, characterized in that the impedance arrangement ( 210 . 230 ) to one not by a measuring device ( 207 . 228 ) occupied secondary port ( 204 . 223 ) connected. Coupler arrangement according to one of the preceding claims, characterized in that the impedance arrangement ( 210 . 230 ) at least two impedances ( 211 . 212 . 231 . 232 ) having. Coupler arrangement according to claim 14, characterized in that the impedance arrangement ( 210 . 230 ) at least two variable impedances ( 211 . 212 . 231 . 232 ), in the complex xen resistance level are not collinear. Coupler arrangement according to one of the preceding claims, characterized in that the impedance arrangement ( 210 . 230 ) a resistor ( 216 ) and a capacitance diode ( 217 - 220 ). Coupler arrangement according to one of the preceding claims, characterized in that the impedance arrangement ( 210 . 230 ) has an inductance with a core and an auxiliary winding. Coupler arrangement according to one of the preceding claims, characterized in that the impedance arrangement ( 210 . 230 ) has a controllable resistance. Coupler arrangement according to one of the preceding claims, characterized in that at several ports ( 204 . 223 . 203 . 224 ) of the coupler ( 200. . 240 ) an impedance arrangement changeable by an electronic control signal ( 210 . 230 ) connected. Coupler arrangement according to one of the preceding claims, characterized in that the coupler ( 200. . 240 ) is designed as a 3 dB coupler, in particular as an in-phase 3 dB coupler or 90 ° 3dB coupler.