Table of Contents
What is a cavity filter?
A microwave cavity filter is a microwave filter using a resonant cavity structure.
A UHF cavity bandpass filter can be equivalent to an inductor in parallel with a capacitor, thereby forming a resonant stage and realizing the function of microwave filtering.
Advantages of Cavity Filters
Compared with other types of microwave filters (bandpass filters), cavity filters have a solid structure, stable and reliable performance, high Q value, and good heat dissipation, and their high-end parasitic passband is far away. Therefore, cavity filters are used in significant communication base stations. Applications are widespread.
Best Cavity filters include coaxial, comb, interdigital, waveguide, and other structural forms. They have a high Q value and are suitable for high-frequency filter production. They generally cover frequencies from 0.1G to 42 G. They have a stable structure and large power capacity. , excellent performance, and other characteristics.
Cavity filter customization steps
- Use CoupleFil or other tool software to determine the filter order, zero point configuration, and topology according to constraints such as insertion loss and suppression, and then obtain the coupling bandwidth (the coupling bandwidth divided by the center frequency is the hi normalized coupling coefficient) and external quality facto Qe
- According to the filter frequency, use AppCAD software to obtain the approximate size of the single cavity. Then use HFSS to first determine the size of the single cavity, and then simulate the coupling part of the filter to obtain the specific size of the coupling window and the structural form and size of the tap. (At this point, the cavity filter simulation design environment is completed);
- According to the coupling coefficient and Qe, use the circuit design simulation software in HFSS or ADS to perform circuit simulation to further verify parameters such as insertion loss and suppression, and make minor adjustments to the coupling coefficient.
- According to the dimensions obtained in the previous step, use 3D design software such as SolidWorks or pro/e to establish a 3D model, draw engineering drawings, and submit them to the machining factory. The standby processing parts will be returned, installed, and debugged (a network analyzer is required). According to the debugging, The results determine whether the design process needs to be iterated and then surface treatments (such as black paint) applied to the filter as needed.
Best Cavity Filter specification requirements (example)
- Center frequency: 1.0GHz (435Mhz)
- Bandwidth: 20MHz (2Mhz)
- Suppression: >35dB@(1020~1040)MHz
- Insertion loss: <1dB Return loss: >20dB
Cavity Filter design typical application
It has a good frequency selection filtering effect in circuits and electronic high-frequency systems and can suppress unwanted signals and noise outside the frequency band.
Used in aviation, aerospace, radar, communications, electronic countermeasures, radio and television, and various electronic test equipment
Cavity Filter Instructions for use
Pay attention to the shell being well grounded when using it, otherwise, it will affect the out-of-band suppression and flatness indicators.
Input/output ports can be used interchangeably
DIY Cavity Filter Customize Free Quote
We can supply customized Coaxial Cavity filters, free samples, and other services. MOQ≥1
We are delighted to respond to any requests; please send your questions and orders.
Please provide insertion loss, rejection, rejection frequency bands, and connector type to better customize the exact cavity resonator filter for you.
Cavity BP bandpass filter Tips
You discuss customization with some factories. You hope the sample is above picture, a 433Mhz spiral filter characteristic diagram.
Finally, what you get for testing result is above picture, the 433Mhz spiral filter characteristic diagram.
- Choosing a trustful supplier. Have you ever encountered such a problem when customizing cavity filters from the factory? The output waveform effect you want is different from the effect you actually test. If you customize with us, we will send you the test results on the instrument before shipping. We will ship the goods only after your confirmation.
- Understand your frequency range and bandwidth needs. Cavity filters are designed to operate at specific frequencies and passbands, so make sure the filter you select meets the requirements of your application and system. To calculate a filter’s passband, use the formula passband = center frequency x bandwidth percentage. For example, if you need a filter with a 1% bandwidth at 915 MHz, the passband would be 915 MHz x 0.01 = 9.15 MHz, implying that the filter should cover the frequency range 910.425 MHz to 919.575 MHz.
- Understand your insertion loss and rejection needs. The amount of signal power lost when passing through the filter is referred to as insertion loss, and the amount of signal power attenuated outside the passband is referred to as rejection. To achieve optimal performance and avoid interference, you want to minimize insertion loss and maximize rejection. You can look at the filter’s specifications to see what its insertion loss and rejection values are at different frequencies.
- Understand your power handling and temperature stability needs. Power handling refers to the maximum amount of RF power that the filter can handle without damage or degradation, and temperature stability refers to the filter’s ability to maintain performance over a wide temperature range. You want a filter that can handle your expected power levels and operate in your environment without affecting its characteristics.
- Compare various cavity filter types and models. Cavity filters can be implemented using a variety of technologies and architectures, including combline, helical, interdigital, waveguide, coaxial, and dielectric resonators. In terms of size, cost, performance, and complexity, each type has advantages and disadvantages. You can compare different types and models of cavity filters online or offline by looking at their features, specifications, reviews, and prices.
- If you have any questions or concerns, consult with experts or manufacturers. Cavity filters are sophisticated devices that necessitate careful design and tuning to achieve the best results. If you are unsure about which filter to purchase or how to properly use it, you can seek advice from experts or manufacturers with experience and knowledge in this field. They can assist you in selecting the best filter for your needs and, if necessary, provide technical support and guidance.