Impedance tuner with linear actuator

Abstract

The precision of the impedance tuner can be improved and the size can be reduced by using a linear actuator instead of a rotary motor. The linear actuator can be integrated with a position sensor to allow very small size and implemented with a servo system for best precision and speed. The spring-loaded arms holding the mismatch probes allow the tuner to operate in any orientation for further fitting into small spaces. The small size reduces losses by allowing direct connection to the wafer probes for on-wafer measurement systems.

Description

BACKGROUND

[0001] Mechanical impedance tuners are widely used to characterize RF devices. The most common type of impedance tuner is a slab line tuner, which typically includes a 50-ohm TEM slab line with a movable mismatch probe. Figure 1A and Figure 1B Such a tuner is shown in simplified form, with a center conductor 10 supported between opposing conductive ground planes 12, 14 that form a slab line. A mismatch probe 20 is supported for movement along the center conductor (horizontal, or parallel to the signal flow), and also in a direction transverse to the center conductor (vertical, or perpendicular to the signal flow). If the mismatch probe is moved out of the electromagnetic field of the slab line, it has little effect, allowing the slab line to appear as a good 50-ohm line. However, if the mismatch probe is moved close to the center conductor, the electromagnetic field is affected, resulting in a mismatch. The magnitude of the mismatch is controlled primarily by adjusting the distance of the mismatch probe from the center conductor. The phase of the mismatch is controlled primarily by moving the mismatch probe in a direction parallel to the center conductor. Also parallel to the center conductor is the direction of signal flow in the tuner.

[0002] Similar effects can be achieved in other transmission line environments, such as waveguides. A slide-screw tuner is a more general term for a mechanical impedance tuner that uses any type of transmission medium. Like the special case of the slab line tuner, a slide-screw tuner typically has a carriage with one or more mismatch probes mounted on it. Moving the mismatch probe into or out of the electromagnetic field changes the magnitude of the mismatch, while moving the carriage changes the phase of the mismatch. Figure 2 An isometric view of a slab line tuner is shown, with a movable carriage 514 that holds a mismatch probe 512.

[0003] In this document, a transmission medium is something that an RF signal can propagate through in a guided fashion. Examples of transmission media are slab lines, coaxial lines, microstrip lines, and various types of waveguides.

[0004] Tuners are used in radio frequency (RF) measurement systems to measure the response of a device under test (DUT) to impedance variations. The tuner can control the impedance seen at each port of the DUT at a fundamental operating frequency (Fl), and sometimes at other frequencies (F2, F3,...). Most commonly, the other frequencies (F2, F3,...) are harmonics of Fl.

[0005] Figure 3is a block diagram of an RF measurement system as a basic load-pull system. The system measures the RF performance of a DUT. The system includes two impedance tuners to control the source impedance and the load impedance seen by the DUT. Such an RF measurement system includes an RF test device (in this case an RF source and a power meter). If the system is automated, there is also a system controller that controls the tuners and the RF test device and collects and records the measured data.

[0006] The slide screw tuner can have more than one carriage. Multiple carriages allow independent impedance tuning of multiple frequencies simultaneously.

[0007] For the remainder of this document, the word "tuner" is defined as a slide screw tuner capable of tuning the magnitude and phase of the reflection coefficient at a known reference plane. The tuning is done by moving the mismatch probes on the carriages perpendicular to the signal flow direction to primarily tune the reflection magnitude and by moving the carriages (parallel to the signal flow direction) to primarily tune the reflection phase. The Z0 position of the tuner is the position designated for use when no tuning is needed. For slide screw tuners, this is usually the position where all mismatch probes are retracted, away from the electromagnetic field of the tuner. It can also be the home position. The Z0 position is usually the position where the tuner is nominally matched to the Z0 of the measurement system. In a coaxial environment, the Z0 of the measurement system is usually 50 Ohms.

[0008] For the remainder of this document, the phrase "mismatch probe" will be used to mean a mismatch probe as part of a tuner.

[0009] For the remainder of this document, the word "carriage" will be used to mean a carriage as part of a tuner and carrying one or more mismatch probes.

[0010] In the prior art, stepper motors have been used to automate various types of slide screw tuners. Stepper motors provide rotational motion and are designed to move in discrete steps, each step triggered by a pulse. The discrete step size is known, controlled by a magnet built into the motor, so stepper motors are typically used in open loop mode. A controller is typically used to control when and how many pulses are sent to the motor. If the motor needs to move to a specific position, the controller will calculate the number of steps needed and send that number of pulses.

[0011] It is desirable for the tuner to move as fast as possible. With a stepper motor, the speed is controlled by the pulse rate, so a fast pulse rate means fast rotation of the motor. But high speed movement of a stepper motor can cause unwanted vibrations. Also, the torque of a stepper motor decreases as the speed increases, so the speed must be limited to have enough torque to successfully make the movement.

[0012] One limitation of open loop mode is that if the friction causes the motor to stall and stop before the movement is complete, the tuner will be in the wrong position and the controller will not know it. Therefore, in a few cases, a position encoder has been added to the tuner to read back the position. In this case, the stepper motor operates in open loop mode, but when the movement is complete, the position can be verified.

[0013] One limitation of using a tuner for impedance control is that losses reduce the matching range, as shown in Figure 4C The edge 35 of the reflection coefficient plot represents total reflection, or The dashed line 36 represents the available matching range of the tuner 30 itself, as shown in Figure 4A This means that the tuner can tune to any impedance within this circle. The solid line 37 represents the available matching range after adding a lossy device 31 (such as a cable) in front of the tuner 30, as shown in Figure 4B This demonstrates that losses in front of the tuner reduce the matching range. Therefore, it is generally desirable to position the tuner as close to the DUT as possible to avoid adding extra losses of connecting cables.

[0014] One important and widely used measurement environment is an on-wafer RF measurement system. A wafer is a flat substrate that is commonly used to manufacture semiconductor and other devices. A wafer typically contains many devices distributed across the surface of the wafer, and a device on a wafer is referred to as an on-wafer device. This type of system allows the DUT to be measured before it is cut or mounted in a package. In this document, the phrase "on-wafer measurement system" means an RF measurement system in which the DUT is an on-wafer device, and the connection to the DUT is made using a wafer probe. The phrase "wafer probe" means a device that connects to an on-wafer DUT or other on-wafer device. A wafer probe typically has fingers on one side that connect to the DUT, and a connector on the other side that connects to the measurement system. The connector of the measurement system is typically a coaxial connector or a waveguide flange.

[0015] One limitation of on-wafer measurement is the need for a microscope to view the DUT and the fingers of the wafer probe in order to connect the wafer probe to the DUT. The microscope can limit the distance that the tuner can be mounted from the DUT, thus requiring an extra length of transmission line to make the connection. In Figure 5In the case of Figure 1, the wafer probes 45, 46 are connected to the DUTs on the wafer 40, but the large tuners 30, 32 cannot be connected directly to the wafer probes 45, 46 because the microscope 41 gets in the way. Therefore, cables 31, 33 must be inserted to make the connection from the tuner to the wafer probe. This adds loss and therefore reduces the available matching range of the tuner. In this document, large tuner means a tuner that is too large to be connected directly to a wafer probe without interfering with the microscope. For a tuner that is connected directly to a wafer probe, this means a) that the tuner connector is connected directly to the connector of the wafer probe without the need for a cable or other extension to make the connection, and b) that the tuner connector is a normal connector mounted close to the tuner body without any length extension beyond the standard length needed for a normal connection.

[0016] For on-wafer mounting of the tuner, it is desirable to minimize the size of the tuner. One limitation to minimizing the size is the stepper motor. Even a small stepper motor is larger than the mismatch probe used in high frequency tuners, so the carriage with the stepper motor and the mismatch probe must typically be larger than desired, which makes the tuner larger. For this document, high frequency tuner is a tuner in which the minimum carriage length (in the direction of signal flow) is limited by the size of the motor. This is typically a tuner with a frequency range covering up to 26.5 GHz or higher.

[0017] Embodiments of the invention improve or eliminate many of the limitations described above. BRIEF DESCRIPTION OF DRAWINGS

[0018] The features and advantages of the present disclosure will be readily appreciated by persons skilled in the art from the following detailed description, taken in connection with the accompanying drawings, in which:

[0019] Figure 1A is a schematic end view of an impedance tuner slabline and mismatch probe arrangement. Figure 1B is a schematic diagram illustrating movement of the mismatch probe in the vertical direction (transverse to the center conductor and signal flow) and the horizontal direction (parallel to the center conductor and signal flow).

[0020] Figure 2 is an isometric view of a slabline tuner with a movable carriage 514 carrying a mismatch probe 512.

[0021] Figure 3 is a block diagram of a typical RF measurement system in which a source tuner controls the source impedance seen by the DUT and a load tuner controls the load impedance seen by the DUT.

[0022] Figure 4A 、 Figure 4B and Figure 4CThe effect of losses placed in front of the tuner is shown. The match range 36 of the tuner 30 can be close, but never perfect at the edge 35 of the reflection coefficient chart. If lossy equipment 31, such as a cable, is placed in front of the tuner 30, the resulting match range 37 shrinks.

[0023] Figure 5 It is shown how small a tuner 38, 39 can be connected directly to the wafer probes 45, 46 when the wafer probes are connected to DUTs on the wafer 40, because the tuners are small enough to fit without interference from the microscope 41.

[0024] Figure 6 It is shown how small a tuner 38, 39 can be connected directly to the wafer probes 45, 46 when the wafer probes are connected to DUTs on the wafer 40, because the tuners are small enough to fit without interference from the microscope 41.

[0025] Figure 7 is a schematic diagram of a linear actuator. The fixed member 304 is mounted on some type of floor or chassis 302. The force generator 308 provides a propulsive force to move the driven member 310, where the motion is constrained to be linear by the guide system 306.

[0026] Figures 8A-8E Examples of several types of linear actuators are shown. Figure 8A A solenoid actuator is shown. Figure 8B A pneumatic actuator is shown. Figure 8C A piezoelectric actuator is shown. Figure 8D A voice coil actuator is shown. Figure 8E A linear motor actuator is shown.

[0027] Figure 9A An embodiment of an impedance tuner is shown, where a piezoelectric actuator 522 is used to drive the motion of the carriage 514, and another piezoelectric actuator 520 is used to drive the motion of the mismatch probe 512.

[0028] Figure 9B An embodiment of an impedance tuner is shown, where a linear motor actuator 526 is used to drive the motion of the carriage 514, and another linear motor actuator 524 is used to drive the motion of the mismatch probe 512.

[0029] Figure 10A is a schematic diagram of a linear actuator with position measurement built in. It is similar to Figure 7 except that the position sensor 312 is mounted on the fixed member 304, so that the position sensor 312 can read the position of the driven member 310.

[0030] Figure 10Bis a schematic of a linear actuator with built-in position measurement. In this case, the position sensor is a linear encoder.

[0031] Figure 11 A block diagram of a servo system is shown. The bold connection 410 between the actuator 404 and the driven component 406 represents a mechanical connection.

[0032] Figure 12 A block diagram of multiple servo systems is shown, where each individual servo system controls one of the axes of motion in the impedance tuner.

[0033] Figure 13 is an isometric view of the small tuners 47, 48, which are oriented sideways to avoid interfering with the microscope 41, in order to be directly connected to the wafer probes 45, 46, which are connected to the DUTs on the wafer 40.

[0034] Figure 14 is a schematic end view of an impedance tuner, which comprises a plate-like line with ground planes 12, 14 and a center conductor 10, and which comprises a mismatch probe 20. The mismatch probe motion transverse to the center conductor 10 is horizontal motion, where the tuner is oriented sideways, and where the mismatch probe 20 is held by an arm 22, which is spring loaded by a spring 24 pushing against a ball bearing 26.

[0035] Figure 15 A tuner mounted to an XYZ positioner with a stand is shown, to allow the tuner to be directly connected to a wafer probe at the correct angle of the wafer probe. DETAILED DESCRIPTION

[0036] In the following detailed description and in the several figures, identical elements are identified with the same reference numerals. The drawings are not to scale, and relative feature sizes can be exaggerated for the purpose of illustration.

[0037] Exemplary embodiments of the present invention include small tuners that can be oriented at any angle to fit the available space. Orientation in this context can refer to vertical, sideways, upside down, or any angle in between. Orientation refers to the direction of motion of the mismatch probe transverse to the direction of signal flow. Thus, vertical orientation means that the motion of the mismatch probe is vertical. In this context, small tuners mean tuners that can be directly connected to wafer probes without interfering with the microscope when the wafer probes are connected to DUTs on a wafer. This is in contrast to the prior art, where the tuner is connected to the wafer probe at an angle, and the tuner is placed in a way that it does not interfere with the microscope. This is shown in Figure 1, where the tuner 1 is connected to the wafer probe 2 at an angle, and the tuner is placed in a way that it does not interfere with the microscope 3. Figure 6The small tuners 38, 39 are shown in FIG. 1 connected directly to the wafer probes 45, 46 on the wafer 40, and the small tuners 38, 39 are capable of being connected directly to the wafer probes without any extension cables. The direct connection includes the tuner connector 39A of the tuner 39 being connected directly to the connector 45A of the wafer probe 45, and the tuner connector 38A of the tuner 38 being connected directly to the connector 46A of the wafer probe 46. This is in contrast to the large tuners 30, 32 in FIG. 1, where extension cables 31, 33 are needed to connect the tuners 30, 32 to the wafer probes 45, 46. The cable 31 goes from the tuner connector 30A to the wafer probe connector 46A. The cable 33 goes from the tuner connector 32A to the wafer probe connector 45A. In Figure 5 the small tuners, the tuner height 48 can also be less than 3 inches. Other embodiments include impedance tuners of conventional size that use linear actuators instead of stepper motors or other sources of rotational motion. Figure 6

[0038] Motors used in the prior art provide rotational motion, which then requires a gear mechanism to convert the rotational motion to linear motion. Thus, the mechanical connection from the motor to the mismatched probe is indirect, increasing the likelihood of gap errors. This mechanism also increases the size and cost of the tuner. In Figure 2 for example, the gear mechanism includes a lead screw. A motor 518 rotates the lead screw 520 to move the carriage 514 parallel to the center conductor 506. Mounted on the carriage 514 is another motor 516, which drives a lead screw to move the mismatched probe 512 vertically perpendicular to the center conductor. In high frequency tuners, the carriage must be larger than is needed to carry the mismatched probe because the carriage must also carry the motor. Figure 2 Only one carriage and only one motor on the carriage is shown, but many tuners have carriages with two mismatched probes, so two motors are mounted on the carriage. Many tuners also have multiple carriages.

[0039] Exemplary embodiments of the present invention use linear actuators instead of rotational motors to provide linear motion directly. A linear actuator is a mechanism that produces force directly in one linear direction to move a driven component, which is constrained to guide to keep the motion in a straight line. There is no conversion from rotational motion to linear motion. By providing direct linear motion, the linear actuator eliminates the gear mechanism needed to convert rotational motion to linear motion. Thus, the linear actuator also eliminates the gap inherent in converting rotational motion to linear motion. Linear actuators are also generally smaller than the mechanisms used in the prior art that are driven by rotational motors. For the remainder of this document, the word "actuator" will mean a linear actuator. Embodiments with actuators allow the size of the tuner to be reduced as well as improve accuracy by eliminating gap errors.

[0040] Figure 7 ​A schematic diagram of an actuator is shown. The ground / chassis 302 is typically the machine frame or larger moving part on which the actuator is mounted. The fixed member 304 is the part of the actuator that remains fixed during motion; it is the frame of the actuator and mounting. The guide system 306 is shown in this example as a rolling element bearing, although many types of guide systems are alternatively employed. The force generator 308 is the propulsion mechanism, which is typically a transducer that converts an input (e.g. electrical) into a force and thus motion. The driven member 310 is the part that moves in the direction of the guide. In a tuner, the driven member can be a carriage, with the fixed member mounted on the tuner chassis, i.e. instead of a lead screw drive or a gear drive. In a tuner, the driven member can also be a mismatch probe, with the fixed member mounted on a carriage.

[0041] Figures 8A-8E Examples of some different types of linear actuators that can be employed in impedance tuner applications are shown. Figure 8A A solenoid actuator is shown, Figure 8B A pneumatic actuator is shown, Figure 8C A piezoelectric actuator is shown, Figure 8D A voice coil actuator is shown, and Figure 8E A linear motor actuator is shown.

[0042] An example embodiment of an impedance tuner uses a piezoelectric linear actuator. Figure 9A An isometric view of a tuner is shown that includes one piezoelectric actuator 522 to drive horizontal motion of a carriage 514 parallel to a center conductor 506, and a second piezoelectric actuator 520 to drive vertical motion of a mismatch probe 512. The vertical motion moves the mismatch probe closer to or further from the electromagnetic field, e.g. closer to or further from the tuner center conductor, perpendicular to the signal flow. Piezoelectric actuators convert electrical signals into precisely controlled physical displacements. They produce large forces compared to their volume, and can be very small. This is particularly suitable for high frequencies where the mismatch probe is small and the required range of motion is small. High frequencies are applied to tuners where the length of the drive mechanism for the carriage (in the direction of the signal flow) is longer than the total length of the mismatch probe on the carriage. This is typically tuners covering frequency ranges up to 26.5 GHz or higher. Piezoelectric actuators allow for the design of small tuners for optimal on-wafer connections.

[0043] Another example embodiment uses a voice coil as a linear actuator. A common example of a voice coil actuator is the actuator used in audio speakers. Figure 8DAnother example is shown. A push coil 322 is attached to a fixed member 320 and slides in a guide bearing 324. A position sensor 326 is integrated into the assembly. The voice coil produces very fast motion, but the range of motion is limited. This also applies to high frequencies where the mismatch probe is small and the required range of motion is small.

[0044] Another example embodiment uses a linear motor actuator. Linear motors have magnets and coils arranged flat to directly provide linear motion. Figure 8E An example is shown in FIG. 5. Figure 9B An isometric view of a tuner is shown, including one linear motor actuator 526 for driving the horizontal motion of the carriage 514 and another linear motor actuator 524 for driving the vertical motion of the mismatch probe 512.

[0045] Another example embodiment is to build the position sensor into the actuator. Figure 10A A schematic diagram of a linear actuator with a position sensor is shown. As the driven member 310 moves, the position sensor 312 reads the position of the driven member 310. Typically, the position sensor 312 can read the position continuously and provide the position data to the controller in real time as the driven member 310 moves.

[0046] An example embodiment of a position sensor is a position encoder. A rotary encoder reads and feeds back the position of a rotary motion, such as the position of a motor. A linear encoder reads and feeds back the position of a linear motion. In this document, the word encoder refers to a rotary or linear position encoder - a device configured to read the position of the carriage or the mismatch probe - to provide feedback with position data. Figure 10B A schematic diagram of a linear actuator with a linear encoder is shown. In this embodiment, the encoder includes two components - a scale 314 attached to the driven member 310 and a sensor 316 attached to the fixed member 304. As the driven member 310 moves, the sensor 316 reads the scale 314 to measure the position of the driven member 310. Alternatively, the scale can be attached to the fixed member 304 and the sensor 316 attached to the driven member.

[0047] In the prior art, a separate encoder is installed on the tuner for position feedback after the movement is completed. The separate encoder increases the size of the tuner. One embodiment of the present invention is to integrate the position sensor into the actuator used in the tuner. This has the advantage of reducing the size, as a separate position sensor is not needed. Also, the position sensor is more directly connected to the drive mechanism for better stability and smaller backlash, and thus better accuracy.

[0048] If the actuator is operated in an open loop arrangement, the position sensor can be used to verify the position after the motion is completed. But when the actuator is used in a closed loop arrangement, as in a servo system, greater benefits are realized. A "servo system" is one in which closed loop feedback is used to calculate the optimal control signal applied to the actuator versus time during movement to produce smooth acceleration, maximum possible velocity, and then smooth deceleration. Figure 11 A block diagram of a servo system is shown. The thick line 410 is the mechanical connection between the force generator and the driven part of the actuator. The thin lines between the other blocks represent signal connections. The servo controller 402 sends a signal to the actuator 404 to initiate motion of the driven part 406. A position sensor 408 measures the position of the driven part and feeds it back to the servo controller. In real time, the servo controller calculates how to continuously adjust the signal sent to the actuator. The calculation is made using the "servo equation". During movement, the first derivative of position with respect to time is velocity, and the second derivative of position with respect to time is acceleration. The servo equation will use the position feedback, and can also use velocity, and even acceleration to make the movement as smooth, fast, and accurate as possible.

[0049] Figure 12 A block diagram of multiple servo systems is shown, where each individual servo system controls one of the axes of motion in the impedance tuner. In this example, the tuner includes a carriage that mounts two mismatched probes. A servo system 412 controls the movement and positioning of the carriage. Servo systems 414 and 416 control the movement and positioning of the respective probes.

[0050] In the prior art, the tuner is typically oriented so that the board line is vertical, and the mismatched probes enter the board line from the top. These prior art tuners require a vertical orientation for best accuracy. But to make the tuner fit into tight spaces, another embodiment of the invention is a tuner that can be oriented in any direction. For example, if the tuner is mounted sideways, it can better directly connect to the wafer probes and avoid conflict with a microscope in the setup on the wafer. This is shown in Figure 13 where the tuners 47, 48 are oriented sideways to directly connect to the wafer probes 45, 46, which are connected to DUTs on the wafer 40, with enough clearance from the microscope 41.

[0051] To make the tuner able to be mounted in any direction, one embodiment of the invention is a spring-loaded arm that holds the mismatched probe so that the direction of gravity does not affect its position accuracy. In this context, a spring-loaded arm is a support arm that holds the mismatched probe, and the arm is spring-loaded laterally against the side of the transmission medium. Lateral against the side of the transmission medium means perpendicular to the signal flow and perpendicular to the direction of the mismatched probe motion. This concept is shown in Figure 14In FIG. 2, the two ground planes 12, 14 are oriented laterally, and the mismatch probe 20 is moved horizontally perpendicular to the center conductor 10. The support arm 22 holding the mismatch probe is spring loaded with a spring 24 that is held centered against a ball bearing 26. The spring loading is not limited to Figure 14 a simple spring in FIG. 2, Figure 14 The concept is illustrated simply. The actual spring loading method should be chosen to best fit the specific mechanical design of the tuner.

[0052] In a wafer measurement system, the wafer probe position must be adjustable in 3 dimensions (3D) to properly connect to the devices on the wafer. The three dimensions can be labeled x, y, and z, where x and y are the horizontal dimensions, and z is the vertical dimension. This 3D positioning is usually done by mounting the wafer probe on a 3-axis positioner, called an XYZ positioner. To connect the tuner directly to the wafer probe to minimize losses, the tuner and probe must move together. Therefore, in this case, the mismatch probe can be rigidly mounted to the tuner, and the tuner can be mounted to the XYZ positioner. The mounting of the tuner to the positioner can be done with an appropriate bracket or support that holds the tuner at the correct angle to mate with the wafer probe. Figure 15 An exemplary embodiment of this mounting method is shown. The wafer probe 46 is rigidly connected to the tuner 47, which in turn is mounted to the XYZ positioner 602 by a bracket 604. The XYZ positioner moves the tuner and probe along the three axes to precisely position the wafer probe 46 to the devices on the wafer 40. Figure 15 A microscope used in typical applications is not shown in FIG. 2. The type of bracket 604 or support depends on the requirements of the specific application.

[0053] While the forgoing has described and illustrated certain embodiments of the subject matter, one skilled in the art will be able to devise various modifications and alternatives without departing from the scope and spirit of the application.

Claims

1. A sliding screw tuner having a fixed ground or chassis, a mismatch probe, and at least one linear actuator, and wherein: the mismatch probe is configured to move in a first direction along a signal flow of a transmission medium and a second direction perpendicular to the signal flow, and whereby at least one of the first and second movement directions is effected by the at least one linear actuator; and wherein the transmission medium is a stripline or waveguide, and the at least one linear actuator includes a mechanism configured to produce a force in one linear direction to move the mismatch probe without requiring a conversion from rotational to linear motion, and a constraint system to keep the motion on a straight line.

2. The tuner of claim 1, wherein a first linear actuator is configured to move a carriage to move parallel to the signal flow, and a second linear actuator is mounted on the carriage and configured to move the mismatch probe to move perpendicular to the signal flow.

3. The tuner of claim 1, further comprising at least one position sensor configured to measure a position in at least one direction of movement.

4. The tuner of claim 3, wherein the movement of the mismatch probe in at least one direction is controlled by a servo system.

5. The tuner of claim 3, wherein the at least one position sensor is an encoder.

6. The tuner of claim 1, wherein the at least one linear actuator is integrated with a position sensor.

7. The tuner of claim 1, wherein the at least one linear actuator includes a piezoelectric actuator.

8. The tuner of claim 1, wherein the at least one linear actuator includes a voice coil actuator.

9. The tuner of claim 1, wherein the at least one linear actuator includes a linear motor actuator.

10. The tuner of claim 1, wherein the mismatch probe is mounted to an arm that is laterally spring loaded against a side of the transmission medium so that a direction of gravity does not affect a position accuracy of the mismatch probe.

11. The tuner of claim 1, wherein the tuner is a small form factor tuner configured to be directly connected to a wafer probe when the wafer probe is connected to a device under test (DUT) on a wafer without interfering with a microscope viewing the connection of the wafer probe to the DUT on the wafer.

12. The tuner of claim 1, wherein the tuner has a height dimension less than three inches.

13. The tuner of claim 1, wherein the tuner is a high frequency tuner having a frequency range covering up to 26.5 GHz or higher.

14. A tuner comprising: a transmission medium, wherein the transmission medium is one of a stripline or waveguide; a mismatch probe configured to move in a direction along a signal flow of the transmission medium and perpendicular to the signal flow; and a linear actuator configured to move the mismatch probe in the direction along the signal flow of the transmission medium and perpendicular to the signal flow. wherein the mismatch probe is held by an arm that is laterally spring loaded against a side of the transmission medium so that the direction of gravity does not affect the positional accuracy of the mismatch probe.

15. The tuner of claim 14, wherein the transmission medium is a slab line.

16. The tuner of claim 14, wherein the transmission medium is a waveguide.

17. A measurement system comprising: a slide screw impedance tuner having a fixed floor or chassis and using a linear actuator for at least one direction of motion; and a transmission medium that is a slab line or a waveguide and the linear actuator includes a mechanism configured to produce a force in one linear direction to move a mismatch probe without the need for a conversion from rotational to linear motion and a restraint system to keep the motion on a straight line.

18. The system of claim 17, wherein the tuner includes a first linear actuator configured to move a carriage so as to move parallel to a signal flow and a second linear actuator mounted on the carriage so as to move perpendicular to the signal flow.

19. The system of claim 17, wherein at least one position sensor is used to measure a position in at least one direction of motion.

20. The system of claim 17, wherein the impedance tuner includes a linear actuator integrated with a position sensor.

21. The system of claim 19, wherein at least one position sensor is an encoder.

22. The system of claim 19, wherein at least one direction of motion in the impedance tuner is controlled by a servo system.

23. The system of claim 17, wherein the linear actuator of the tuner includes a piezoelectric linear actuator.

24. The system of claim 17, wherein the tuner includes at least one linear actuator that is a voice coil actuator.

25. The system of claim 17, wherein the tuner includes at least one linear actuator that is a linear motor actuator.

26. The system of claim 17, wherein the tuner includes at least one mismatch probe mounted on an arm that is laterally spring loaded against a side of the transmission medium so that the direction of gravity does not affect the positional accuracy of the mismatch probe.

27. The system of claim 17, wherein the tuner is mounted in an orientation other than vertical.

28. The system of claim 17, wherein the system is a wafer on measurement system and wherein at least one tuner is directly connected to a wafer probe, wherein the tuner is a small form factor tuner configured to be directly connected to the wafer probe without interfering with microscope viewing of the wafer forming a connection to the probe while the wafer probe is connected to a device under test (DUT) on a wafer.

29. The system of claim 28, further comprising: an XYZ positioner; and a wafer probe. wherein the impedance tuner and the wafer probe are mounted to the XYZ positioner to position the wafer probe relative to the wafer.

30. A sliding screw impedance tuner comprising: a mismatch probe; a transmission medium; at least one linear actuator coupled to the mismatch probe; the mismatch probe is configured to move in a first direction along a signal flow of the transmission medium and a second direction perpendicular to the signal flow; wherein the transmission medium is one of a slab line or a waveguide and the at least one linear actuator includes a mechanism configured to generate a force in one linear direction to move the mismatch probe without a conversion from rotational motion to linear motion and a constraint system to keep the motion on a straight line; and wherein at least one of the first and second movement directions of the mismatch probe is achieved by the at least one linear actuator.

31. The impedance tuner of claim 30, wherein the at least one linear actuator comprises: a first linear actuator configured to move a carriage supporting the mismatch probe parallel to the signal flow, and a second linear actuator mounted on the carriage and configured to move the mismatch probe perpendicular to the signal flow.

32. The impedance tuner of claim 30 or 31, further comprising: at least one position sensor configured to measure a probe or carriage position in at least one direction of motion.

33. The impedance tuner of claim 32, wherein a servo system is utilized to control the motion of the mismatch probe in at least one direction.

34. The impedance tuner of claim 32, wherein the at least one position sensor is an encoder.

35. The impedance tuner of claim 30 or 31, wherein the at least one linear actuator is integrated with a position sensor.

36. The impedance tuner of claim 30 or 31, wherein the at least one linear actuator comprises one of a piezoelectric actuator, a voice coil actuator, and a linear motor actuator.

37. The impedance tuner of claim 30 or 31, wherein the mismatch probe is mounted to an arm that is laterally spring loaded against one side of the transmission medium such that the direction of gravity does not affect the positional accuracy of the mismatch probe.

38. The impedance tuner of claim 30 or 31, wherein the tuner is a small form factor tuner configured to be directly connected to a wafer probe that is connected to a device under test (DUT) on the wafer without interfering with a microscope viewing the connection of the wafer to the probe.

39. The impedance tuner of claim 38, wherein the tuner is a component of a measurement system that includes an XYZ positioner; and wherein the impedance tuner and the wafer probe are mounted to the XYZ positioner to position the wafer probe relative to the wafer.

40. The impedance tuner of claim 30 or 31, wherein the tuner has a height dimension less than three inches.

41. The impedance tuner of claim 30 or 31, wherein the tuner is a high frequency tuner having a frequency range covering up to 26.5 GHz or higher.

42. The impedance tuner of claim 30 or 31, wherein the transmission medium is a stripline.

43. The impedance tuner of claim 30 or 31, wherein the transmission medium is a waveguide.

44. The impedance tuner of claim 30 or 31, wherein the impedance tuner is a component of a measurement system.

45. The impedance tuner of claim 30 or 31, wherein the tuner is mounted in an orientation other than vertical.

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