ADS – APPLICATION IN FILTER DESIGN Soh Ping Jack

1.0 FILTER DESIGN PROCESS Low-pass Prototype Design Filter Specification Scaling & Conversion Done using ADS Optimization & Tuning Filter Implementation

1.2 GENERAL STEPS IN FILTER DESIGN Know your filter specifications Max Flat/Equal Ripple, LPF/HPF/BPF/BSF Desired freq of operation Passband & stopband range Max allowed attenuation (for Equal Ripple) Design your LPF Prototype Min Insertion Loss level, No of Filter Order/Elements Determine whether shunt cap model or series inductance model to use Determine elements’ values from Prototype Table

1.3 FILTER DESIGN PROCESS Low-pass Prototype Design Filter Specification Scaling & Conversion Done using MWO Optimization & Tuning Filter Implementation

1.4 GENERAL STEPS IN FILTER DESIGN Scaling & Conversion Draw LPF filter prototype Determine if there are any conversion to HPF/BPF/BSF required If yes, convert the LPF to the desired HPF/BPF/BSF filter prototype. If no, move on to step 4. Use equations to de-normalize cap & inductance values Re-draw de-normalized filter prototype

1.5 FILTER DESIGN PROCESS Low-pass Prototype Design Filter Specification Scaling & Conversion Done using ADS Optimization & Tuning Filter Implementation

To do this you have to be familiar with ADS 1.4 GENERAL STEPS IN FILTER DESIGN Filter Implementation & Optimization Draw de-normalized LPF filter prototype with elements’ values Implement filter prototype on software Optimize & tune filter to get best response To do this you have to be familiar with ADS

2.1 Working in the Circuit Schematic Environment 2.0 KNOW YOUR SOFTWARE - BASIC 2.1 Working in the Circuit Schematic Environment 2.2 Selecting & placing elements 2.3 Setting project frequency range 2.4 Changing elements’ values 2.5 Adding result Graphs & Charts

2.1 Working in the Circuit Schematic Environment 2.0 KNOW YOUR SOFTWARE - BASIC 2.1 Working in the Circuit Schematic Environment 2.2 Selecting & placing elements 2.3 Setting project frequency range 2.4 Changing elements’ values 2.5 Adding result Graphs & Charts

To open up the program, double click on the ADS icon 2.0 KNOW YOUR SOFTWARE - BASIC 2.1 Working in the ADS Environment To open up the program, double click on the ADS icon

2.0 KNOW YOUR SOFTWARE - BASIC 2.1 Working in the ADS Environment A pop-up window like this will appear after clicking “New Project”, name your project as “Filter” (or any other names) and click on “OK” button after entering the desired name

2.0 KNOW YOUR SOFTWARE - BASIC 2.1 Working in the ADS Environment A blank schematic like this will appear. It is used for the placement of components/elements

2.1 Working in the Circuit Schematic Environment 2.0 KNOW YOUR SOFTWARE - BASIC 2.1 Working in the Circuit Schematic Environment 2.2 Selecting & placing elements 2.3 Setting project frequency range 2.4 Changing elements’ values 2.5 Adding result Graphs & Charts

2.0 KNOW YOUR SOFTWARE - BASIC 2.2 Selecting and Placing Elements To select a specific element, ensure that the “Lumped Components” tab is selected. Specific element are sorted into these categories as shown in the box below

2.0 KNOW YOUR SOFTWARE - BASIC 2.2 Selecting and Placing Elements For example, to select a inductor, select “Lumped elements” category on the top drop down menu. A specific lumped element (inductor) then can be selected from the box at the bottom

2.0 KNOW YOUR SOFTWARE - BASIC 2.2 Selecting and Placing Elements To insert the desired element into the schematic, click on the specific element in the bottom box and drag till an outline of the element appear as shown. Click again to place the element

2.0 KNOW YOUR SOFTWARE - BASIC 2.2 Rotating Elements To rotate the element after placing it on the schematic, right click on the element and select “rotate” function.

2.0 KNOW YOUR SOFTWARE - BASIC 2.2 Rotating Elements The rotated element will be rotated 90 degrees after this function is applied

2.1 Working in the Circuit Schematic Environment 2.0 KNOW YOUR SOFTWARE - BASIC 2.1 Working in the Circuit Schematic Environment 2.2 Selecting & placing elements 2.3 Wiring, grounding, adding ports 2.4 Setting project frequency range 2.5 Changing elements’ values 2.6 Adding result Graphs & Charts

2.0 KNOW YOUR SOFTWARE - BASIC 2.3 Wiring and grounding To start wiring the components together, click on the wire icon and start creating connections from node to node

All connection from node to node between components will be created 2.0 KNOW YOUR SOFTWARE - BASIC 2.3 Wiring and grounding All connection from node to node between components will be created

2.0 KNOW YOUR SOFTWARE - BASIC 2.3 Wiring and grounding To insert a ground node, click on the “Insert Ground” icon at the top tool bar

The ground is then placed at the desired nodes 2.0 KNOW YOUR SOFTWARE - BASIC 2.3 Wiring and grounding The ground is then placed at the desired nodes

2.0 KNOW YOUR SOFTWARE - BASIC 2.3 Adding S-parm simulator A termination must be added to continue with the S parameter simulation. Click on the “Term” icon on the right tool bar. The termination network components are actually sinusoidal voltage components with an ideal series resistor

Click to wire all the “Term” components as shown and ground it 2.0 KNOW YOUR SOFTWARE - BASIC 2.3 Adding S-parm simulator Click to wire all the “Term” components as shown and ground it

2.0 KNOW YOUR SOFTWARE - BASIC 2.3 Adding S-parm simulator To proceed with an S parameter simulation, a simulator must be added into the schematic. The “Simulation-S_param” palette is selected from the drop down menu

2.0 KNOW YOUR SOFTWARE - BASIC 2.3 Adding S-parm simulator Select the “S P” icon and click on anywhere on the schematic to place the S-parameter simulator

2.0 KNOW YOUR SOFTWARE - BASIC 2.3 Setting project frequency range Define desired “Start Freq”, “Stop Freq” & “Freq Step”. In this case, it should be from 1.5 GHz till 4.0 GHz with steps of 0.01 GHz

2.1 Working in the Circuit Schematic Environment 2.0 KNOW YOUR SOFTWARE - BASIC 2.1 Working in the Circuit Schematic Environment 2.2 Selecting & placing elements 2.3 Setting project frequency range 2.4 Changing elements’ values 2.5 Adding result Graphs & Charts

2.0 KNOW YOUR SOFTWARE - BASIC 2.4 Changing elements’ values To edit an element’s value, double-click on the element’s default value and enter a desired value

2.0 KNOW YOUR SOFTWARE - BASIC 2.4 Elements’ Values Before starting the simulation, ensure that all the capacitor and inductor values are as shown in this figure.

2.0 KNOW YOUR SOFTWARE - BASIC 2.4 Starting the simulation To start the simulation, click on the “Simulate” button at the top toolbar.

2.1 Working in the Circuit Schematic Environment 2.0 KNOW YOUR SOFTWARE - BASIC 2.1 Working in the Circuit Schematic Environment 2.2 Selecting & placing elements 2.3 Setting project frequency range 2.4 Changing elements’ values 2.5 Adding result Graphs & Charts

2.0 KNOW YOUR SOFTWARE - BASIC 2.5 Adding result Graphs & Charts – Add Graph After clicking the “Simulate” button, a pop up window like this will appear, showing the progress of the simulation

2.0 KNOW YOUR SOFTWARE - BASIC 2.5 Adding result Graphs & Charts – Graph Types Rename the graph as preferred After simulation completion, a “Data Display Window” will appear.

2.0 KNOW YOUR SOFTWARE - BASIC 2.5 Adding result Graphs & Charts – Add Graph To display the S parameters of this simulation, a “rectangular plot” graph type is selected. Drag and drop the graph onto the display area.

2.0 KNOW YOUR SOFTWARE - BASIC 2.5 Adding result Graphs & Charts – Select Meas After inserting the appropriate graph type, it still does not know what type of parameters that is to be plotted on it. To define this, double click on the parameters “S11” and “S21”. Choose the display units (in dB) A pop-up window like this will appear, select the appropriate parameters to be displayed in rectangular form

The graph will show the results as displayed here. 2.0 KNOW YOUR SOFTWARE - BASIC 2.5 Adding result Graphs & Charts – Simulate The graph will show the results as displayed here.

Filter Design Criteria 2.0 KNOW YOUR SOFTWARE - BASIC 2.5 Adding result Graphs & Charts – Results Filter Design Criteria A good S11 will have a response at the desired design freq with < -10dB value in pass band A good S21 will have almost 0dB response in pass band, & infinite response in stop band

3.0 D.I.Y No. 1 Simulate the following design in ADS. Save the file.

3.1.1 Selecting & Setting Variables 3.1.2 Analyzing & Tuning 3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.1 Selecting & Setting Variables 3.1.2 Analyzing & Tuning

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Re-open the file that was saved earlier in DIY No 1.

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.1 Selecting & Setting Variables To start manual tuning of certain parameters in a schematic, the “Tune Parameter” in the schematic should be selected

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.1 Selecting & Setting Variables Immediately after the “Tune” button is clicked, a Status Window and a Tuning Controller window will appear

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.1 Selecting & Setting Variables Add another rectangular plot to see the changes on S11 and S21 when the Tuner is tuned.

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.1 Selecting & Setting Variables The parameters values that are to be tuned can be selected from the schematic. Once selected effectively, it will appear in the tuning controller as shown on the left

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.1 Selecting & Setting Variables The parameters values that are to be tuned can be selected from the schematic. Once selected effectively, it will appear in the tuning controller as shown on the left

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.1 Selecting & Setting Variables A variable tuning toolbar like this will appear before you. The nominal, max, min and step of tunable values/range can be set here by users

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.2 Analyzing & Tuning Ensure that the variable tuner controller slider bar is also easily accessible. Notice the difference of S11 and S21 values when sliding the values of the capacitance up and down

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.2 Analyzing & Tuning To further observe the effect of capacitance values, the “Store” button can be pressed to hold the initial (old) values before tuning

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE 3.1.2 Analyzing & Tuning The old (initial) values of capacitance are indicated by the thin line, and the current (tuned) values are shown in the graph as the thick line

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE CASE STUDY Let’s say our engineering manager has given to us the following task, which is to design a low pass filter according to the spec below:

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE CASE STUDY Design requirements LPF 5 elements symmetrical design Insertion loss > -0.5 dB from 403 MHz to 440 MHz Allow 50 MHz guard band to -3 dB roll off 2fc attenuation > 35 dB Return loss > 15 dB in pass band

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE CASE STUDY The filter below is designed:

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE CASE STUDY The transmission coefficient response is as follow:

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE CASE STUDY To zoom in the response on the Y-axis, double click on the graph and edit the “Plot Options”

3 dB rollout too far (more than 50 MHz guard band) 3.1 KNOW YOUR SOFTWARE - INTERMEDIATE CASE STUDY Zooming in on the Y-axis response; 3 dB rollout too far (more than 50 MHz guard band)

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE CASE STUDY We are supposed to have only < 50 MHz guard band, i.e 440 + 50 = 490 MHz. Use the tune tool to tune the -3dB roll off point to 490 MHz. You are allowed to change the values of cap and inductors accordingly. However, note that they must be symmetrical; i.e C1 = C2 = C3 and L1 = L2

BOLEH? AIYO!! VERY SUSAH LAH!! 3.1 KNOW YOUR SOFTWARE - INTERMEDIATE CASE STUDY BOLEH? AIYO!! VERY SUSAH LAH!!

Click on the “Variable” icon at the top tool bar 3.1 KNOW YOUR SOFTWARE - INTERMEDIATE What about using the “variable” feature? Click on the “Variable” icon at the top tool bar

Double click on the “VAR” icon to invoke the window 3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Adding Variables Double click on the “VAR” icon to invoke the window

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Adding Variables Enable the “Tuning Status” and vary the max, min and step values accordingly Add a parameter named “LCoil” and click on the “Tune/Opt/Stat/DOE” option

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Adding Variables – LCoil Add LCoil with the following limits: Min = default (leave it as it is) Max = 30 nH Step = Default (Leave it as it is) Then change the Values of the inductor (note: not the name of inductor) in the schematic to be LCoil

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Adding Variables The new variable, “LCoil” and its ranges will be shown here Change both of the inductor values to the specific variable “LCoil”

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Adding Variables Add another two variables using the way the previous “LCoil” variable is defined Cend for the left and right capacitor on the edges Cmid for the center capacitor

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Adding Variables – Cmid and Cend Add Cmid and Cend with the following limits: Min = default (leave it as it is) Max = 20 pF Step = Default (Leave it as it is) Then change the Values of the inductor (note: not the name of capacitors) in the schematic to be CMid and Cend respectively Click on the “Tune Parameters” icon to invoke the tuning tool bar

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Adding Variables – Tuning Close the previous data display window Click on “simulate” icon at the top tool bar Finally, click on the “Tune Parameters” icon to invoke the tuning tool bar Changes will be applied to the variables simultaneously (meaning: we can keep the symmetrical characteristic of the filter while tuning our components easily)

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Notice that there are now only 3 slider bars as there are only 3 parameters to be tuned

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE Tune the variables and we will still get the symmetrical LPF as required

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE TASK 1 Tune the filter to have the following characteristics: Insertion loss > -0.5 dB from 403 MHz to 440 MHz Allow 50 MHz guard band to -3 dB roll off 2fc attenuation > 35 dB Return loss > 15 dB in pass band

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE TASK 1 (Cont) The current filter characteristic is shown as follow: The level of insertion loss meets the spec of having at least -0.5 dB in passband

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE TASK 1 (Cont) The current filter characteristic is shown as follow: The level of return loss meets the spec of having at least -10 dB in passband

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE TASK 1 (Cont) (Zooming in) The current filter characteristic is shown as follow: The frequency at -3 dB cutoff should be about 490 MHz instead of 720 MHz to allow for 50 MHz rolloff margin

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE TASK 1 (Cont) (Zooming in) The current filter characteristic is shown as follow: The attenuation level at 2fc (2 x 420 MHz = 840 MHz) should have a value of > 35 dB from att level at fc.

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE TASK 1 (Cont) Tune the filter to have the following characteristics: Insertion loss > -0.5 dB from 403 MHz to 440 MHz (OK) Allow 50 MHz guard band to -3 dB roll off 2fc attenuation > 35 dB Return loss > 15 dB in pass band (OK) So how are we going to tune to meet the specs in red while keeping the specs that are already met (in green)?

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE TASK 1 (Cont) Tune the by increasing/decreasing the inductor/cap values till specs are met