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
  • H01P5/04—Coupling devices of the waveguide type with variable factor of coupling

Definitions

• the present invention relates to the field of electronics and communication technologies.
• the present invention relates more particularly to a coaxial automatic impedance adapter.
• the displacement of the divers according to the two axes is carried out by means of piloted motors.
• the plunger For displacement along the axis Oy, ie perpendicular to the axis of the coaxial line, the plunger approaches or moves away from the central conductor locally varying the distance between the central line and the plunger, that is to say say the characteristic impedance of the line.
• the tuner has an impedance equal to 50 ⁇ .
• These automatic coaxial tuners have the major advantage of being calibrated before measuring the components.
• the input and output of the tuner are connected to a vector network analyzer.
• a control software of the vector network analyzer and the tuner makes it possible to acquire the dispersion parameters of the tuner at several frequencies.
• Calibration of the tuner being completed it is possible to very quickly characterize a power component and / or noise easily without assembly and disassembly of the measurement system.
• Coaxial tuners have excellent performance but these are quickly reduced by the insertion losses of the tuner related to the transition between the coaxial connector and the central conductor. The higher the losses at the transition, the lower the modulus of the reflection coefficient of the load impedance achieved. Therefore, it will not be possible to synthesize all the impedances of the Smith chart.
• Coaxial tuners have the advantage of being broadband and allowing the passage of DC voltages, but loss of insertions reduces their performance at high frequency. These tuners are also very bulky and heavy which presents a great disadvantage when the components are measured directly on "wafer” (cake) using microwave spikes. Indeed, given the size of the tuner, the latter is connected to the component by a cable with losses. The distance separating the tuner from the component is increased and the insertion losses between the tuner and the component as well. Under these conditions, the dead zone is then larger. In order to reduce this area, a pre-adaptation system is placed between the tip and the tuner. However, this device does not completely eliminate the limitation mentioned above. In addition, this pre-adaptation is very rigid. This considerably increases the vibrations, in the plane of the microwave peaks, induced by the displacement of the blocks.
• tuners have, as we have already mentioned, a translational movement of the blocks along the axis Ox.
• the rapid movement of these blocks (trolley + engine + plunger), whose mass is important, causes significant inertia movements and therefore vibrations.
• these vibrations quickly degrade the quality of the contacts between the tips and the component and therefore the quality of the measurement.
• this effect can cause the destruction of this one and spikes especially if the component is polarized at high voltage.
• the present invention intends to overcome the drawbacks of the prior art by proposing a coaxial tuner with double "slug” (double probes).
• This new impedance adapter best meets the characterization of power and noise transistors.
• This tuner is designed to operate for wide frequency bands and has only a lateral translational movement along the axis Ox.
• the present invention relates, in its most general sense, a coaxial impedance adapter having two probes (“slugs”) and only has a lateral translational movement along the Ox axis.
• a coaxial impedance adapter for a transmission line comprising in the longitudinal direction a conductive central line Ox axis, the adapter having two probes in the transmission line adapted to move according to a translational movement along the axis Ox, and two motors driving in translation, each, one of said probes, said motors being isolated from the probes by elastic couplings.
• said impedance adapter operates in the frequency band extending from 0.25 GHz to 240 GHz.
• said probes are of circular section and slide longitudinally in the transmission line. They adapt particularly well to transmission guides of circular section. In the case where these guides are of rectangular section or any other shape, probes of identical section will preferably be chosen in order to "fill" the zone of the waveguide.
• "resonator" probes which comprise a stack of metal layers separated by at least one insulating layer in the longitudinal direction, or "broadband” probes formed of metal cylinders whose faces side have a recess centered towards the inside of the cylinder.
• a dielectric is deposited on the center line of the impedance adapter or on the slugs (outer and inner diameter). This is to limit short circuits and improve microwave performance.
• the probes are interchangeable. It is noted that motors are isolated from the rest of the system via resilient couplings to minimize vibration.
• the principle of the double slug tuner is based on the displacement of two ends of a characteristic impedance line different from 50 ⁇ inside a cylinder closed on both sides by standard connectors.
• the principle of this tuner is based on the displacement of two impedance characteristic slugs different from 50 ⁇ in a 50 ohm coaxial line.
• said probes have a characteristic impedance different from the characteristic impedance of said transmission line, which is 50 ohms in many waveguides.
• the first slug locally decreases the impedance of the line by changing the value of the diameter D of the outer conductor.
• Automatic piloting is provided, for example by computer and / or electronic means, probes to allow accurate and reproducible positioning thereof.
• each probe is secured to a carriage by the elastic coupling, the adapter further comprising motors adapted to drive the carriages in translation in the longitudinal direction of the transmission line. The motors are then driven automatically.
• each motor is a rotary motor which rotates a precision ground screw driving a corresponding translational carriage to which an associated probe is connected.
• said motors are optimized in order to have low travel times as well as precise control of the acceleration and servo profiles.
• one of the so-called pre-adaptation probes is arranged to move over a distance of ⁇ / 2, where ⁇ is the working wavelength, and the second probe is arranged to move over a distance of ⁇ / 2 relative to said pre-adaptation probe.
• the impedance adapter has a reflection coefficient greater than 0.98 at 10 GHz.
• the advantages of the coaxial automatic tuner according to the present invention are as follows: - Microwave performance significantly better than existing systems. Indeed, according to the present invention, the system offers a very high flexibility of impedance synthesis with a high reflection coefficient.
• the frequency band that can be realized for coaxial tuners ranges from 0.25 GHz to 240 GHz.
• the proposed system proposes a very high repeatability with a high reflection coefficient - a single displacement along the transmission line exists whereas in the existing systems, there are two movements of which one of them is perpendicular to the line of transmission (with displacements very close to this line).
• the moving probe In conventional systems, the moving probe must approach the suspended central line (a few tens of microns) and this over a long distance. This causes great fragility. In our system, this problem is totally avoided.
• the tuner can even operate on an inclined plane without loss of efficiency.
• the deposition of a dielectric improves performance and avoid short circuits.
• the proposed system is much more stable (from a vibratory point of view) than conventional systems. Indeed, the motors are isolated from the rest of the system via elastic couplings. This is a very important point when measuring under spikes.
• the motors and the associated electronics have been optimized to provide low travel times and accurate control of acceleration and servo profiles (to minimize vibration problems). Under these conditions, the cost of implementation is significantly lower than existing systems.
• the system according to the invention allows a great strength of the central line. Indeed, it is maintained at a constant distance: there is no suspended line as in the tuners according to the prior art.
• the tuner according to the invention does not pose a problem for transport.
• the tuner according to the invention supports high polarization voltages thanks to the design of the tuner.
• FIG. impedance according to the prior art illustrates an exemplary arrangement of the probes in an impedance adapter according to the present invention
• FIG. 3 illustrates the operation of an impedance adapter according to the invention
• Figure 4 shows two examples of interchangeable probes used in the present invention.
• This tuner is based on the displacement of two characteristic impedance slugs different from 50 ⁇ in a 50 ohm coaxial line.
• the characteristic impedances of coaxial slugs are given by relation (1) below.
• This impedance adapter is shown in Figure 2.
• ⁇ r is the dielectric constant of the medium.
• FIG. 2 shows the cylindrical transmission line 4 comprising in the longitudinal direction and at its center a conductive central line 5.
• the transmission line 4 has a diameter of 6.91 mm and the central line 5 has a diameter of 3 mm. .
• the set "transmission line + central line" thus composed has a characteristic impedance of 50 ohms.
• the probes (“slugs”) 6a and 6b are cylindrical in shape of length 3.75 mm and outer diameter slightly smaller than the internal diameter of the transmission line, about 6.9 mm. They have a longitudinal bore at its center of diameter 3.1 mm allowing the passage of the central line 5. The probes can easily slide along the center line (see the arrows in Figure 2). Each probe has a characteristic impedance significantly different from that of the transmission line, in this case by the aforementioned dimensions, the impedance of the probes is about 2 ohms.
• Figure 4 illustrates two examples of probes that can be used in pairs.
• the probe of FIG. 4a is a "resonator" probe of cylindrical shape and composed in the longitudinal direction of two metal layers separated by an insulating layer. This arrangement reduces the frequency band so that the probe behaves like a resonator.
• the advantage of reducing the frequency band at which the slug takes effect lies in the ability to control the value of the reflection coefficient presented to the component under test not at one frequency but at several.
• the probe of FIG. 4b is made of cylindrical metal having at both end faces a progressive recess from the outside towards the center, where the conductive central line 5 slides. This recess has the effect of increasing the band of frequency of the probe. The latter behaves like a broadband probe.
• the slug locally varies the impedance of the line by changing the value of the diameter D of the outer conductor. This local variation of impedance modifies the reflection coefficient of the tuner so the impedance of it.
• the impedance of the tuner moves on a constant TOS (steady state wave) circle centered on Z 0 .
• a displacement of ⁇ / 2 makes it possible to describe the whole circle on the Smith chart.
• the radius of the circle, on the Smith chart varies. It is then impossible to cover the entire abacus with a single slug with non-parametric characteristics.
• the impedance of the tuner no longer moves on a circle with constant TOS. If we move the first slug 6b by a distance ⁇ / 2 along the conductor, we describe the entire circle on the chart around the pre-adaptation impedance.
• the adapter made was automated using two stepper motors of very high precision associated with an encoding system to achieve the removal of slugs.
• the motors rotate, each, a precision ground screw that drives a carriage.
• Each carriage mounted on a screw moves a slug.
• the tuner could be placed closer to the component under test, thus not affecting the size of the dead zone.
• automatic tuner calibration can be used to characterize a component in minutes and accurately.
• the motor (1) is linear type allowing, unlike rotary engines, to limit the vibrations generated during its operation.
• the probes 6a and 6b are each connected to a block "carriage 2 + motor 1 + guide 3" by a coupling arm 7 provided with elastic vibration absorption means. Vibration absorption is performed at the coupling arm by means of a tongue of flexible material sandwiched between the two metal parts located respectively to the block "motor + carriage + guide” and to the probe.
• the outer conductor 4 of the transmission line is provided with a slot in the longitudinal direction of the line.

Landscapes

• Control Of Motors That Do Not Use Commutators (AREA)
• Measuring Leads Or Probes (AREA)
• Measurement Of Resistance Or Impedance (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2005
  • 2005-07-18 FR FR0507607A patent/FR2888670B1/fr not_active Expired - Fee Related
• 2006
  • 2006-07-18 JP JP2008522016A patent/JP4782833B2/ja not_active Expired - Fee Related
  • 2006-07-18 WO PCT/FR2006/001759 patent/WO2007010134A1/fr active Application Filing
  • 2006-07-18 US US11/988,953 patent/US7936233B2/en not_active Expired - Fee Related
  • 2006-07-18 EP EP06778882.8A patent/EP1905120B1/de not_active Not-in-force

Non-Patent Citations (1)

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