Microwave Filter Design Software

10.12.2020by admin

The same RF filter design is incorporated using built in micro strip line elements in RF/microwave design software such as Agilent EESoF or ADS or microwave office from AWR. Step 4: Following is the realization of RF filter as micro-strip based on specifications mentioned at the beginning of this article.
Free EDA software. Click here to go to our main page on computer-aided design. Note: all of the links on this page were working, on 4 July 2018. It today's date is later than that, all bets are off. On this page we provide links to free EDA software. Not all of it has been checked out by us, so buyer beware.
This webinar given by Dan Swanson from DGS Associates showcases a narrowband, high-Q cavity combline filter design example using the AWR Design Environment platform and SW Filter Design software. Step 1 determines the required coupling coefficients and external Q for the filter.

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RFSim99 is a freeware RF simulation software utility. It’s small, fast, and reliable. I should make it clear that it performs basic RF simulation only, and is nothing like Genesys/ADS, Microwave Office, Ansoft Designer, HFSS, or of that ilk, so if you want a full-on EM solver, this is not your program.

What is RF Filter

The most flexible and powerful Microwave and RF Filter and Multiplexer Design Software Prof. Nevzat Yildirim, E-Mail: nyil@metu.edu.tr (Presented at the workshop 'State of the Art Filter Design using EM and Circuit Simulation Techniques' in MTT-S'97, Denver, Colorado, USA) FILPRO at the MTT-S'97, Denver. We can design high Q cavity filters, planar filters on ceramic substrates and printed circuit board filters using standard SMT components. Microwave design software. There is the option of combining an EM model e.g. Sonnet, with a linear mode LINC2 and HSPICE instead of purchasing a single integrated package.

RF filter is used to pass radio frequencies within the desired bandand blocks the undesired or unwanted radio frequencies in a wireless communication chain.The filters can be various types based on requirement. For example in the RF up conversion chain below, used to convert70 MHz IF input to 6GHz RF output filters are employed as per need in the design.

At the input 52-88 MHz low pass filter is used using discrete components. This signalbeats with 1112.5 MHz signal gives 1182.5 MHz signal output and other products from the mixer.After first mixer BPF (band pass filter) which passes 1182.5 MHz with bandwidth of 36MHz isemployed. Later after second stage of mixing, 5925 to 6425 MHz microstrip based parallelcoupled band pass filter is incorporated.

In the first stage of mixing, local oscillator of fixed value 1112.5MHz is passed through microstrip based 3-4 stagehairpin RF filter can be used. The round corner edge coupled band pass filter of microstrip type is used to filter theoutput of synthesizer of value 4680 to 5375MHz.

RF Filter design example

This article describes basic steps in microwave and RF filter design.The example mentioned here is for micro-strip based LP filter. To illustrate RF filter design we will takeRF Low Pass Filter with the following specifications:
Impedance: 50 Ohm
Cutoff frequency (Fc): 3 GHz
Equi-ripple: 0.5dB
Rejection: 40 dB at 2*Fc

Step 1: First determine normalized frequency, which in this case is w/wc,equals to 2 (6GHz/3GHz). Determine filter type based on ripple required,which in this case is about 0.5dB, hence chebyshev type of filter will be ideal choice.

Now based on normalized frequency (2) and attenuation (40dB) and using the filterresponse curve (chebysev LPF with 0.5 dB ripple), determine filter order (N) required forthe design. Filter response will have normalized frequency on X axis and Attenuation onY axis. Different filter orders are plotted against these two. Doing so from 40dB andnormalized frequency of 2 we get filter order of value 5 from the curve for our rf filterdesign.

Based on filter order N (here 5) and using Filter coefficients table as mentioned abovefor Chebysev LPF for 0.5dB ripple we will determine filter coefficients,which are g1=1.7058,g2=1.2296,g3=2.5408,g4=1.2296,g5=1.7058,g6=1.The figure above mentions low Pass Chebysev Filter Coefficients for 0.5dB ripple forvarious orders of the filter. Following figure mentions LPF with order N using discreteL and C components.

Step 2: Now use Richard transformation to replace inductor by short circuitline and capacitor by open circuit line. Length of the lines should be λ/8.Figure 4 below is obtained after Richard- transformation is applied to discretecircuit in figure 4 for rf filter design.

Step 3: Now convert all the short circuited stubs, which are in series into shunt connected open circuit stubs. This can be achieved using Kudora's identities. This is depicted in figures 6-9 below. To apply Kudora's identity unit elements are introduced in the circuit where ever required as shown in figures below.

In figure 6, unit element is inserted at the input and output without changing rest of the elements.Now Z1 and Z5 are converted from open circuit shunt elements to the short circuit series elements.

Now two more unit elements are inserted at the source and destination.And using Kudora's identities z1,z2,z4 and z5 elements are converted fromS.C. series elements to the O.C. shunt elements

The same RF filter design is incorporated using built in micro strip line elements in RF/microwave design software such as Agilent EESoF or ADS or microwave office from AWR.

Step 4: Following is the realization of RF filter as micro-strip based on specifications mentioned at the beginning of this article.

Step 5: This microstrip layout mentioned in figure.10 is etched on the respective dielectric based on frequency of operation as mentioned and tested with connectors using scalar network analyzer (SNA).

Conclusion

The same method has to be used for band pass and high pass RF filter design.Only thing has to be taken care is to choose filter order N using normalized frequency versus attenuation curve. Based on this order N, appropriate filter coefficients have to be derived from table with required ripple.

RF Filter Related Links

RF Filter calculator
RF filter manufacturers
RF filter types
RF filter applications
RF filter selection guide
RF filter terminologies

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