90° Polarized Rotary Joint TE10-to-TM01 Mode Guide

November 10, 2026

RF or microwave power is sent from a fixed waveguide to a rotating one through a 90° polarized rotary joint. The rotary joint maintains the required polarization relationship. A TE10-to-TM01 mode converter is often used for this. The TE10 mode changes from a square shape to a circular shape, and the TM01 mode's field pattern stays the same no matter how the joint is turned. This means that turning the joint doesn't change the signal much. This isn't always how polarized units work; it depends on the frequency band, waveguide geometry, and the design of the manufacturer. This guide talks about how it works, what it needs, how to choose, what it can be used for, and how to get a quote from ADM.

What a 90° Polarized Rotary Joint Does

Rotation, Phase, and Polarization Are Different Things

Three ideas are often mixed up by buyers. When one half of a joint turns against the other half, this is called mechanical rotation. The electrical phase tells us when the wave is traveling along the signal path. The direction of the electric field is called polarization. A rotary joint that is polarized at 90° moves a signal across the rotating interface and maintains a set polarization relationship. For example, there could be a 90° difference between the input and output orientations or between two channels. For a joint to work, it only needs to pass power. Before placing an order, I always make sure to look at the dimensional drawing, interface document, and polarization test data. This is because the product name doesn't tell you which of these three behaviors the design controls.

Polarized Versus Standard Rotary Joints

It is important for a standard waveguide rotary joint to have low loss and a stable match while the antenna turns. It doesn't need to manage the direction of the field. That requirement is added to a polarized version. Both ends of the interface must either keep the field direction the same or change it by a known angle. The receiver will see that energy as interference if the joint leaks it into the wrong polarization. If there is only one polarization in the link and a fixed polarizer comes after the rotating part, a standard joint may work well. The polarized design works best when the joint itself needs to set the polarization.

Why Polarization Control Matters in Real Systems

Dual-polarization weather radar sends and receives pulses that are both horizontal and vertical. It then compares the two returns to find the differential reflectivity, which is a quantity that is extensively discussed in radar meteorology texts. That only makes sense if the rotary joint keeps both channels balanced and far apart. Leakage between channels lowers the quality of the link because satellite terminals reuse frequency through orthogonal polarizations. The number for this problem is cross-polarization isolation. The signal that gets to the receiver is also weaker when there is a small polarization error, since the antenna and the wave that is coming in no longer line up.

TE10-to-TM01 Operating Principle

Field Characteristics of TE10 and TM01

In a rectangular waveguide, TE10 is the main mode. It has a clear linear polarization because its electric field has peaks in the middle of the wide wall and points along the narrow wall. In a circular waveguide, TM01 lives. It has an electric field going through it and a magnetic field going around it in a circle. The pattern is the same at all angles around the axis. In a 90° polarized rotary joint, it's important that the joint is symmetrical because the field doesn't change when one half turns. Loss and phase don't change. But TM01 comes with a cost. Since it doesn't have a favorite polarization direction, the polarization is set by the rectangular transitions at each end. Also, in a circular guide, the TE11 mode cuts on first, and the TM01 mode sits about 31% higher. TE11 must be blocked by a good design.

How Mode Conversion Is Built

A transition that changes the shape of the field step by step is used to change TE10 into TM01. Probes, irises, cavities, and stepped waveguide sections are all common elements. The match is changed across the frequency range by irises and steps. Each maker has their own geometry because the end result is different depending on the waveguide size, frequency band, and polarization layout. The WR-90 guide, which works from 8.2 to 12.4 GHz, is a common starting size. However, the size of the converter changes for each band. Customers should know that the ability to change from TE10 to TM01 is a design choice and not a feature that all units have. As the maker, ask them to show you the mode structure and the results that were measured.

Bearings, Chokes, and Channel Configuration

There is a small space between the fixed and rotating parts where the RF path goes. At that gap, an electrical short is made by a choke structure, which is usually a quarter-wavelength groove. This means that the two halves don't have to touch. Tight tolerances on concentricity and gap width keep the match stable at all angles, and bearings keep them in place. The torque is based on the type of bearing and seals used. Single-channel units only have one way for signals to go. When you have two channels in a unit, you need more polarization isolation, phase balance, and amplitude matching. Dual-channel designs are more difficult to make and usually cost more, but they work with radar and satellite terminals that use dual-polarization. Find out in writing what the alignment and gap tolerances are.

Technical Specifications and Verification

Electrical Parameters to Review

It's not enough to just match the center frequency. Check the full frequency range that it can work with, as well as the insertion loss, return loss (VSWR), and cross-polarization isolation. Because arcing and heating depend on these things, you need to add peak power, average power, pulse width, and duty cycle for radar. In two-channel units, phase stability and amplitude balance are important. Ask for rotational variation, or WOW, as engineers like to call it. It checks how much loss and phase change there is as the joint turns. When a datasheet only shows one loss number, it can hide a change in pitch or temperature. Ask for performance curves for the whole band, along with the test conditions that went into making each curve.

Mechanical and Environmental Ratings

As quickly as bad RF data can stop a project, so can a bad fit. Check the type of waveguide flange, the mounting pattern, the shaft configuration, the maximum load that the shaft can handle, and the starting torque. Check the speed of rotation and the rated service life in turns. For use outside, check the temperature range, sealing, and corrosion protection. A lot of people who buy things for the military look at MIL-STD-810 methods for temperature, humidity, vibration, shock, and salt fog. Find out what methods the supplier actually used on this item. If your market needs it, ask for RoHS or REACH paperwork. In the quote request, you should describe the installation area so that the supplier can match the materials and sealants.

Testing and Documentation

More can be learned from test evidence than from nominal values. The S-parameters that show insertion loss, return loss, VSWR, and channel isolation are measured by a vector network analyzer. To get WOW, run these tests across the whole band at a few different angles of rotation and again while the joint turns. At their rated peak power, high-power units may need to be broken down. Changing the temperature, the humidity, the vibration, and checking for leaks are all examples of environmental screening. Before you give your approval, you should get dimensional drawings, an interface control document, material data, certificates, installation instructions, test reports, and warranty terms. Our lab equipment at ADM can measure up to 110 GHz, and all of our products are ISO 9001 certified and RoHS compliant.

Comparison, Selection, and Common Mistakes

Compared With Other Rotary Joint Types

Coaxial rotary joints are small, cover a wide frequency range with less power, and don't need to be changed from one mode to another. Their limits are how much power they can handle and how much they lose at higher microwave frequencies, where waveguides work better. Most waveguide rotary joints can handle more power with little loss, but they can't change the polarization on their own. A 90° polarized rotary joint gives you more control over the polarization, but it also costs more and is harder to make. One-signal links work best with single-channel designs, while dual-polarization systems work best with dual-channel designs. It might be enough to have a coaxial or standard joint if the polarization is set by another part of the chain. Not product names, but full designs, specs, interfaces, and support throughout the lifecycle.

A Step-by-Step Selection Process

Start with the RF needs, such as the frequency range, polarization, channel count, VSWR, insertion loss, and isolation targets for the TE10 to TM01. Next, make sure that the power, pulse conditions, rotation speed, torque, service life, and mounting limits are all right. Then, rank your priorities by how they will be used. A lot of the time, peak power and sealing come first in radar programs. A lot of the time, loss and isolation come first at satellite terminals. Frequency coverage and repeatability may be the most important things for laboratory systems. Lastly, you should look at the supplier's help with design reviews, resources for machining and alignment, test equipment, quality system, and experience exporting. Before the quote, I think we should have a short engineering call. Just a few minutes of talking can save you from having to redesign something later.

Mistakes That Cost Time and Money

Putting faith in the label is the first mistake. It's possible that a "90° rotary joint" doesn't include TE10-to-TM01 conversion, so check the test results and the mode structure. The second one only matches frequency and doesn't take into account loss, power, isolation, or changes in angle. The third is not taking weather and temperature into account when installing things outside. Other mistakes include using flanges that don't work with each other, putting too much weight on the shaft, and picking a supplier based only on price. Lack of tests or poor documentation can be hidden by a low quote. Before approving the purchase, you should trade drawings and technical reviews, and you should compare every interface dimension to your own CAD model.

Applications, Customization, and Procurement

Where These Joints Are Used

Radar for tracking, weather, surveillance, and communication, satellite terminals, microwave and millimeter-wave test systems, remote sensing equipment, defense platforms, aerospace assemblies, and OEM antenna integration are all common uses. Radar for weather and air traffic needs to have two stable channels. When the platform moves, satellite terminals on ships or planes need to have low loss and clean isolation. Repetition is important to test systems. Aviation and aerospace, shipboard systems, weather monitoring, security check systems, UAVs, and finding your way are all things that ADM does. Each use changes the order of importance of peak power, loss, phase stability, sealing, size, qualification testing, and tracking.

Customization, Cost, and Lead Time

The cost and lead time are based on the frequency, waveguide size, channel count, complexity of the conversion, power rating, materials, sealing, rotation life, testing, and tooling. A full quote request includes RF targets, mechanical drawings, the environment, the amount, the date of delivery, and the requirements for compliance. Buyers can get goods directly from the manufacturer, from an OEM, from a distributor, in bulk, or as part of a project. The engineers who can change a design can get to it the fastest through direct manufacturer supply. ADM provides OEM services, quick prototype turnaround, and technical support that includes help with setup and fixing problems. Also, check the schedule for the prototype, the production capacity, the export documents, the support for spare parts, and the continuity of the supply.

Final Selection Checklist

Check these three groups one last time before you ask for a quote.

RF and mode requirements: Confirm the frequency range, TE10-to-TM01 requirement, polarization orientation, insertion loss, VSWR, isolation, phase stability, channel configuration, and power rating. Give each item a target value, and ask the supplier to show a measured result taken under the same test condition. Explain any gap between target and measured data.
Mechanical and environmental requirements: Review interfaces, mounting, rotation speed, torque, service life, temperature, humidity, corrosion, vibration, and weatherproofing. Compare each item with your drawing and your installation site, not only with the nominal rating on a datasheet. Outdoor and airborne units need the closest attention here. Ask which tests support each claimed rating.
Supplier and procurement requirements: Verify microwave experience, quality certifications, test reports, customization ability, delivery commitments, warranty coverage, packaging, and compliance documents. Ask how the supplier handles design changes after the first prototype, and how it supports spare parts and repeat orders over the life of your program. Clear answers build confidence.

These checks show if a design meets the needs of both your system and your program.

Conclusion

A 90° polarized rotary joint moves RF power across a rotating interface while maintaining a clear polarization relationship. A TE10-to-TM01 converter is one way to make sure steady performance while the interface is rotating. Since TM01 has an axisymmetric field, turning the joint doesn't change much, but the design has to stop modes like TE11 from happening. The choice is based on the whole frequency range, insertion loss, VSWR, isolation, power, and mechanical limits. Swept and rotating measurements are used to back up all of these factors. When polarization is set by another part of the chain, both coaxial and standard waveguide joints can still be used. Some common mistakes are believing what the label says, matching frequency only, and not caring about the environment. In radar, satellite, aerospace, and test applications, risk is lower when the mode structure is checked, all documents are complete, and requirements are made clear.

FAQ

Q1: What does a 90° polarized rotary joint do?

It keeps a clear polarization relationship while sending microwave signals between fixed and rotating parts. This keeps the antenna in place, stops cross-polarization, and keeps dual-polarization working even when the antenna turns.

Q2: Does every polarized rotary joint use TE10-to-TM01 conversion?

No. How a mode acts depends on the shape of the waveguide, the frequency band, and the design made by the manufacturer. Be sure the mode structure is correct and the supplier can show you measured data before you use a product as a TE10-to-TM01 design.

Q3: Should I choose a single-channel or dual-channel design?

Choose a single channel for a single signal path. For dual-polarization radar or satellite terminals, choose dual-channel because the system results are affected by how well the two paths are isolated, balanced, and matched in terms of amplitude.

Q4: What information does ADM need for a quotation?

As well as the delivery date and frequency range, please send the power profile, interfaces, environment, quantity, and mode requirement. Drawings help the review go faster. It's also helpful to include a short note on your application.

Request a 90° Polarized Rotary Joint Quote from ADM

If you email ADM at craig@admicrowave.com with your needs, our engineers will look over your 90° polarized rotary joint project. We have been making microwaves for more than 20 years, are ISO 9001 certified, follow RoHS rules, and can test up to 110 GHz. We can help with OEM development, make quick prototypes, and give technical advice. Let us know what frequency range, polarization, power, and delivery you need, and we'll send you a quote as a supplier of 90° polarized rotary joints.