I have designed different filters including microstrip, substrate-integrated waveguide (SIW) (in different resonator shapes such as hexagon, rectangle, circle, square)), coaxial cavity (in different resonator shapes such as hexagon, rectangle, circle, square), and waveguide (both rectangular and cylindercal).

Microwave filter design involves the creation of a device that can selectively allow certain frequencies to pass through while attenuating or blocking others. The design process typically includes the determination of filter specifications, selection of filter topology, component selection, and optimization. The presence or absence of transmission zeros in the filter design plays a significant role in its characteristics and performance. Let's explore the process and steps of microwave filter design both with and without transmission zeros.

Microwave filters are awesome devices that allow specific frequencies to pass through while blocking others. Designing these filters involves a series of steps to create something amazing. Let's dive into the process, both with and without transmission zeros.

Step 1: Figure out what you want

Start by determining the specifications for your filter. Do you need a low-pass, high-pass, bandpass, or bandstop filter? Set the frequency range you want to allow and block, and consider parameters like insertion loss and return loss. These specifications will guide your design.

Step 2: Pick the right filter type

Choose a filter topology that matches your specifications. There are different types like Butterworth, Chebyshev, elliptic, and Bessel filters. Think about how sharp you want the cutoff to be and the trade-offs between passband and stopband characteristics.

Step 3: Select the perfect components

Now it's time to pick the components for your filter. You'll need inductors, capacitors, and transmission lines. Choose their values based on the desired filter response and the frequency range you're working with.

Step 4: Design without transmission zeros

If you're designing a filter without transmission zeros, your focus is on achieving the desired frequency response. That means minimizing passband ripple, maximizing stopband attenuation, and nailing the cutoff frequency. You'll calculate the component values using equations, design software, or optimization algorithms.

Step 5: Design with transmission zeros

When you want to add transmission zeros to your filter, it's time to level up. These zeros help improve selectivity and stopband characteristics. You'll need to select suitable transmission zeros, adjust their positions and strengths, and even add extra components like resonators or transmission line stubs.

Step 6: Optimize and test your creation

Once the initial design is ready, optimize it by fine-tuning the component values and tweaking the filter response. You can use optimization techniques and simulation tools to make it perfect. Afterward, fabricate your filter and test it using measurement techniques like network analyzers to ensure it meets your desired specifications.

In a nutshell, designing microwave filters involves selecting the right topology, choosing components, and optimizing the design to match your specifications. Adding transmission zeros takes it up a notch, enhancing the filter's performance. So go ahead and create something amazing!

SIW Filter Design

Cascaded Triplet Substrate Integrated Waveguide Filter at 28 GHz.

Designing SIW filters with a spike-free response is a challenging process. As RF engineers, which design rules should we follow to make your filter spike free, both in-band and out-band? What is the main source of spikes in SIW filters?

Magnetic cross-coupling (positive coupling) can be used to create sharp roll-off at the higher band. Electric field distribution and 3D model of my designed filter at 28 GHz are shown in the following. To design this 3rd order filter with a cascaded triplet(CT) structure at 28GHz using #Synmatrix and #HFSS, I used #Rogers3003 with a relative dielectric constant of 3. The filter insertion loss is less than 2 dB and 3 poles are visible clearly. Synmatrix software empowers RF innovations and significantly aids engineers in designing different types of filters more efficiently.

#SIW#mmwave#MicrowaveFilter#Filter#CT_Structure#TransmissionZero#SharpRollOff#SubstrateIntegratedWaveguide

Electric cross-coupling (negative coupling) can be used to create sharp roll-off at the lower band. Electric field distribution and 3D model of my designed filter at 28 GHz are shown in the following. To design this 3rd order filter with a cascaded triplet(CT) structure at 28GHz, I used #Rogers3003 with a relative dielectric constant of 3. The filter insertion loss is less than 2 dB and 3 poles are visible clearly.