We find that many of our customers have similar questions about us as a company, our products, product application, or related subjects. To serve you better, we offer this list of frequently asked questions. If you don't find the answer you need, please don't hesitate to contact us.

We also invite you to submit questions of your own, and we will add them to this list along with our response. (You will also receive a prompt answer via email.)

What are the differences between the electrical length, the physical length, and the insertion length of an adapter?

Generally, the overall length of an adapter is considered to be its physical length from connector end to connector end. The insertion length is the length an adapter will add when inserted between two connectors.

The electrical length depends on the size and type of dielectric material used in an adapter. It is measured at the mating plane of the outer conductor and is the length of the adapter as it appears to the signal traveling through it.

In many instances, the electrical length, the insertion length, and the physical length are very close to each other. In an adapter that has no dielectric, the length of the adapter (measured at the mating plane of the outer conductor) is its electrical length. (The dielectric of air is close enough to "1" that its effects can usually be ignored.) This is not the case with most adapters which contain some dielectric material. The electrical length of the adapter needs to be calculated for that portion of the adapter that contains the dielectric. In some cases (such as with TNC connectors) the mating plane of the adapter is recessed, making its physical length quite different than its electrical length. Physical differences between female and male connectors and variations in the amount of dielectric material used in each can also make phase matched adapters appear to be of different physical lengths even though their electrical lengths are the same.

Whatever your application may be, Maury Microwave offers a wide variety of coaxial and waveguide adapter types and configurations that are designed to meet your needs. Please contact our Sales Department to discuss your specific requirements.

What are the advantages/disadvantages of stub tuners versus slide screw tuners?

Apart from their obvious physical differences, slide screw tuners perform much more predictably and are more intuitive to use than stub tuners. When the stub on a stub tuner is adjusted, the resultant change in impedance can be considerable, both in magnitude and phase. With slide screw tuners, impedance magnitude is changed by varying the probe depth, and phase is changed by varying the carriage position. Obtaining a repeatable measurement is, therefore, much easier with slide screw tuners than with stub tuners. One disadvantage of stub tuners is that the metal-to-metal contact (inherent in their design) makes them subject to greater wear than slide screw tuners (which have no metal-to-metal contact). Also, the stubs of stub tuners are actually short circuits. This can present problems if a DC short is not permissible (which is often the case when testing active devices or circuits).

The chief advantage of stub tuners is their low cost (relative to other types of tuners) which may make them a better choice in applications where the need for accuracy and repeatability is less critical.

Likewise, slide screw tuners can be an attractive lower-cost alternative to automated tuners in device characterization and load pull measurement applications.

Whatever your application may be, from stub tuners to complete automated tuner systems, Maury Microwave offers a wide variety of tuner models and configurations that are designed to meet your needs. Please contact our Sales Department to discuss your specific requirements.

What are the benefits of using connector gages?

Using a connector gage is important for two critical reasons. Checking the contact location (or depth) of a connector contact ensures that it does not 1) protrude beyond, or 2) recess below its specification. Both situations create undesirable conditions that degrade electrical performance, and protruding connector contacts have the added potential for causing serious damage to connectors and equipment.

A protruding contact will cause an "interference fit" between two connectors, resulting in poor electrical performance. As the connection is tightened, pressure against the contacts will cause them to bend, crush, or possibly even break. The cost of repairing a test port damaged by a bad connector can be very high.

A recessed contact won't cause an interference fit, so damage is not an issue, but a "gap fit" between two connectors will occur where contacts fail to meet properly. The gap creates a discontinuity and a poor mismatch condition results, which has a negative impact on electrical performance that is proportional to the size of the gap.

(The same criteria hold true for measuring the dielectric location in connectors that contain dielectric material.)

When critical electrical performance is a must, properly mated connections are essential. Measurement experts agree that the critical dimensions of each connector should always be verified before making connections. The easiest way to verify connector dimensions is with an appropriate connector gage.

Maury Microwave offers the right tools for this job, with over 30 gage types and more than 20 gage kit configurations available. Please contact our Sales Department to discuss your specific requirements.

Can I use my calibration kit with one type of connector and then use an adapter to measure a different type of connector?

Generally, you should always calibrate your test setup in the same type of connector that you plan to use when making measurements. Inserting an adapter after the setup is calibrated effectively invalidates the calibration. However, if you must insert an adapter to facilitate a connection, remember that the adapter will add to the measurement uncertainty and its presence must be considered. The effective directivity will then be the sum of the corrected directivity plus the reflection of the adapter.

Maury Microwave offers a wide variety of coaxial and waveguide calibration kits in most popular connector types and sizes. Please contact our Sales Department to discuss your specific requirements.

What are the differences between SMA, 3.5mm, and 2.92mm connectors, and can they be mated?

A major difference between SMA, 3.5mm, and 2.92mm connectors is their frequency of operation. Some SMA connectors are rated up to 26.5 GHz, but the majority (and the devices using them) are only rated up to 18 GHz. Similarly, most 3.5mm connectors are rated to operate as high as 34 GHz, although their typical use is only up to 26.5 GHz. Most 2.92mm connectors are rated to operate as high as 40 GHz.

Another difference is that SMA connectors have a dielectric interface while 3.5mm and 2.92mm connectors are air-interface connectors. The air interface provides for a more repeatable connection with better electrical performance. (See Maury application note 5A-011.)

A 3.5mm or 2.92mm designation refers to the inside diameter of a connector's outer conductor. A 3.5mm connector's outer conductor has a 0.1378 inch (3.5mm) inside diameter, and a 2.92mm connector's outer conductor has a 0.1151 inch (2.92mm) diameter.

The center conductor diameters of 3.5mm and 2.92mm connectors also differ; being 0.0598 inches (1.520mm) and 0.0500 inches (1.270mm) respectively. The ratio between inner and outer conductors provides the 50 ohm nominal impedance of these connectors. (See Maury technical data sheet 5D-003: Handy Microwave Formulas.)

SMA connectors have a teflon dielectric interface. Adjustments to the inner and outer conductors are made to compensate for the thickness of the dielectric material. This can cause greater variation in electrical performance (due to dielectric material inconsistencies) than is typical of the relatively stable air dielectric of 3.5mm and 2.92mm connectors. The SMA connector's outer conductor diameter is usually increased to compensate for the dielectric. This reduces the wall thickness of the mating portion of the male SMA outer conductor. Reduced mating surfaces result in weakened outer conductor interfaces that are subject to compression damage when repeatedly connected. Compression of the outer conductor's mating surface degrades the electrical performance of a connector, and (because the center conductor is inserted further into the mating connector) damage to the female connector can result.

How then can all three types of connectors be mated with each other given these differences? Mating is possible because the pin portion of their male center conductors and the inside diameter of the female contacts are the same diameter in all three connectors. This enables the male pin in a 2.92mm connector to be inserted into the female contact in a 3.5mm connector and vice versa. In addition, the coupling portion of the outer conductor and the thread size and diameter are the same on all three connectors.

However, some misalignment of the outer and the inner conductors is inevitable when different connectors are mated. This misalignment creates a discontinuity that can reduce the overall electrical performance when connectors of different types are mated. (Interestingly, tests have indicated that SMA connectors mated with 3.5mm connectors may actually provide better overall performance than two mated SMA connectors. See Maury application note 5A-011)

Maury Microwave offers a wide variety of precision connectors in most popular types and sizes, including SMA, 3.5mm, and 2.92mm. Please contact our Sales Department to discuss your specific requirements.

How can I tell if my vector network analyzer (VNA) has a good calibration?

A simple (but effective) method for verifying that a proper calibration has been performed on your vector network analyzer is to check the residual source match error. Source match verification is performed using an air line (or waveguide straight section) and a fixed short circuit. The air line is connected to the VNA test port and the fixed short is connected to the air line. The scale on the analyzer is set appropriately for the display and the ripple pattern is measured. The amount of ripple measured will indicate the source match error. The smaller the ripple - the better the source match. Ideally, the source match error should be greater than 45 dB. Source match error can be of particular importance if the device-under-test (DUT) has a high VSWR. Many of Maury Microwave's calibration kits contain air lines or waveguide straight sections for this purpose. The method for verifying source match is illustrated below. See Maury Application Note 5C-026 and Technical Data Sheet 5D-025 for more on VNA calibrations.

What is TRL calibration?

Traditional, full, two-port calibration methods typically use three impedance standards and one transmission standard to calibrate a vector network analyzer (VNA). The standards normally used in this method are shorts, opens, loads, and thrus (making this what is often referred to as a SOLT calibration).

A thru-reflect-line (TRL) two-port calibration kit uses at least three standards to define the calibrated reference plane. The measured parameters of the thru, reflect, and line standards in a TRL calibration kit perform the same function as a SOLT calibration. A variation of the TRL method is the line-reflect-line (LRL) calibration, wherein one line section represents the thru portion of the calibration. LRL kits are typically used in coaxial applications where frequency bandwidth and mechanical limitations may prohibit the use of a single line section. The line section of a TRL calibration should be 1/4 wavelength, or 90∞ (the exact length is not critical as long as it is known) and should not be multiples of 1/2 wavelengths or 180∞. A phase difference between 18∞ and 162∞ has proven to be adequate in some cases, however the National Institute of Standards and Technology (NIST) and Hewlett-Packard both recommend that the phase difference remain between 30∞ and 150∞. For more information on TRL / LRL calibrations, see Maury application note 5A-017.

Either type of kit may be used, depending on the available calibration standards and the VNA's functionality. Some of the trade-offs (advantages versus disadvantages) are as follows:

SOLT calibration standards can be difficult - if not impossible - to build in many non-coaxial measurement applications (such as in-fixture, wafer and waveguide measurements). Also, the TRL method may be the only option when calibration standards for proprietary or unique connectors are not readily available.

In many cases (particularly waveguide), it is easier to manufacture a superior impedance standard for a TRL calibration kit than for a SOLT calibration kit. The line section effectively represents the impedance standard in TRL calibration. Therefore, standards for a straight section (in waveguide) and a beadles air line (in coaxial) can be defined by their mechanical specifications. Also, it is often easier to build to (and verify) mechanical dimensions than to traditional impedance standards (or loads) which are usually verified by comparison to another standard.

Some disadvantages of the TRL calibration are; a) this method can only be used to perform two-port calibrations, and b) the length of the air lines may prohibit performance of a TRL calibration at low frequencies. (Maury Microwave's TRL / LRL coaxial tri-kits are designed to overcome these disadvantages by including precision fixed loads, which can be used to perform one-port calibrations and calibrations at low frequencies.)

Maury Microwave offers a wide variety of coaxial and waveguide calibration kits in most popular connector types and sizes, including TRL kits. See Maury data sheets 2Z-042 (7mm), 2Z-043 (Type N) and 2Z-044 (7-16) for specifications. Please contact our Sales Department to discuss your specific requirements.

What is the power handling capability of Maury Microwave adapters?

Generally, Maury Microwave's adapters and connectors are designed for low power laboratory applications where high power requirements are typically not needed. Typical power handling for most of our common types of connectors are listed here.

Caution! This is a general guideline and is not intended as a guarantee that the power levels shown can be realized and are safe in every application.

For waveguide-to-coaxial adapters, the power handling capability of the connector usually determines the rating of the adapter, so the same formulas will apply. This is also true for most between-series coaxial-to-coaxial adapters.

Maury Microwave does offer special waveguide-to-coaxial adapters designed for high power applications. Please contact our Sales Department to discuss your specific requirements.

Does Maury Microwave manufacture line stretchers?

Maury Microwave manufactures a wide variety of variable impedance tuning devices such as double or triple stub tuners, slide screw tuners, sliding loads, shorts, and opens. Unfortunately, we no longer manufacture line stretchers. Microlab FXR (Tel:973 992-7700) is a company that still manufactures line stretchers.

How do I import Maury load pull data into Agilent's ADS?

Agilent has developed an ADS DesignGuide that enables you to import your Maury loadpull files into ADS. To learn more about this capability, see the Agilent on-line ADS Design Guide at: http://eesof.tm.agilent.com/