ads – application in filter design soh ping jack

ADS – APPLICATION IN FILTER DESIGN

Soh Ping Jack

2

1.0 FILTER DESIGN PROCESS

Filter Specification

Low-pass Prototype

Design

Scaling & Conversion

Filter Implementation

Optimization & Tuning

Done using ADS

3

1.2 GENERAL STEPS IN FILTER DESIGN

A. Know your filter specifications

1. Max Flat/Equal Ripple,

2. LPF/HPF/BPF/BSF

3. Desired freq of operation

4. Passband & stopband range

5. Max allowed attenuation (for Equal Ripple)

B. Design your LPF Prototype

1. Min Insertion Loss level, No of Filter Order/Elements

2. Determine whether shunt cap model or series inductance model to

use

3. Determine elements’ values from Prototype Table

4


Filter Filter SpecificationSpecification

Low-pass Low-pass Prototype Prototype

DesignDesign

Scaling & Conversion

Filter Filter ImplementationImplementation

Optimization Optimization & Tuning& Tuning

Done using Done using MWOMWO

5


C. Scaling & Conversion

1. Draw LPF filter prototype

2. Determine if there are any conversion to

HPF/BPF/BSF required

3. If yes, convert the LPF to the desired HPF/BPF/BSF

filter prototype. If no, move on to step 4.

4. Use equations to de-normalize cap & inductance

values

5. Re-draw de-normalized filter prototype

6


Filter Filter SpecificationSpecification

Low-pass Low-pass Prototype Prototype

DesignDesign

Scaling & Scaling & ConversionConversion

Filter Implementation

Optimization & Tuning

Done using ADS

7


D. Filter Implementation & Optimization

1. Draw de-normalized LPF filter prototype

with elements’ values

2. Implement filter prototype on software

3. Optimize & tune filter to get best response

To do this you have to be familiar with ADS

8

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

9


2.1 Working in the Circuit

Schematic Environment

2.22.2 Selecting & placing elements Selecting & placing elements

2.32.3 Setting project frequency Setting project frequency

rangerange

2.42.4 Changing elements’ valuesChanging elements’ values

2.52.5 Adding result Graphs & ChartsAdding result Graphs & Charts

10


2.1 Working in the ADS Environment

To open up the program, double click on the ADS icon

11


2.1 Working in the ADS EnvironmentA 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

12


2.1 Working in the ADS Environment

A blank schematic like this will

appear. It is used for the

placement of

components/elements

13


2.12.1 Working in the Circuit Working in the Circuit

Schematic EnvironmentSchematic Environment

2.2 Selecting & placing elements


rangerange



14


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

15



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

16



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

17


2.2 Rotating Elements

To rotate the element after placing it on the schematic,

right click on the element and select “rotate” function.

18


2.2 Rotating Elements

The rotated element will be rotated 90 degrees after this

function is applied

19


2.12.1 Working in the Circuit Schematic Working in the Circuit Schematic

EnvironmentEnvironment

2.22.2 Selecting & placing elementsSelecting & placing elements

2.3 Wiring, grounding, adding ports

2.42.4 Setting project frequency rangeSetting project frequency range



20


2.3 Wiring and grounding

To start wiring the components together, click on

the wire icon and start creating connections from

node to node

21



All connection from node to node between components

will be created

22



To insert a ground node, click on the “Insert Ground” icon

at the top tool bar

23



The ground is then placed at the desired nodes

24


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

25



Click to wire all the “Term” components as shown and

ground it

26



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

27



Select the “S P” icon and click on anywhere on the

schematic to place the S-parameter simulator

28


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

29






rangerange



30



To edit an element’s value, double-click on the element’s

default value and enter a desired value

31


2.4 Elements’ Values

Before starting the simulation, ensure that all the capacitor and inductor values

are as shown in this figure.

LL2

R=L=6.436 nH

LL1

R=L=6.436 nH

CC3C=0.9833 pF

CC2C=0.9833 pF

CC1C=3.182 pF

TermTerm1

Z=50 OhmNum=1

TermTerm2

Z=50 OhmNum=2

32


2.4 Starting the simulation

To start the simulation, click on the “Simulate” button at

the top toolbar.

33






rangerange


2.5 Adding result Graphs & Charts

34


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

35


2.5 Adding result Graphs & Charts – Graph Types

After simulation completion, a “Data Display Window” will appear.

Rename the graph as preferred

36


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.

37


2.5 Adding result Graphs & Charts – Select Meas

A pop-up window like this will appear, select the appropriate parameters to

be displayed in rectangular form

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)

38


2.5 Adding result Graphs & Charts – Simulate

The graph will show the results as displayed here.

39

m1freq=dB(S(1,1))=-3.017

2.000GHz

m2freq=dB(S(1,1))=-12.473

1.510GHz

m3freq=dB(S(1,1))=-0.148

2.800GHz

m4freq=dB(S(2,1))=-14.747

2.800GHz

1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.81.4 4.0

-30

-25

-20

-15

-10

-5

-35

0

freq, GHz

dB(S

(1,1

))

Readout

m1

Readout

m2

2.800G-148.1m

m3dB

(S(2

,1))

2.800G-14.75

m4

m1freq=dB(S(1,1))=-3.017

2.000GHz

m2freq=dB(S(1,1))=-12.473

1.510GHz

m3freq=dB(S(1,1))=-0.148

2.800GHz

m4freq=dB(S(2,1))=-14.747

2.800GHz


2.5 Adding result Graphs & Charts – Results

Filter Design CriteriaA good S11 will have a response at the desired design freq with < -10dB value

in pass bandA good S21 will have almost 0dB

response in pass band, & infinite response in stop band

40

3.0 D.I.Y No. 1

Simulate the following design in ADS. Save the file.

LL2

R=L=6.436 nH

LL1

R=L=6.436 nH

CC3C=0.9833 pF

CC2C=0.9833 pF

CC1C=3.182 pF

TermTerm1

Z=50 OhmNum=1

TermTerm2

Z=50 OhmNum=2

41

3.1 KNOW YOUR SOFTWARE - INTERMEDIATE

3.1.1 Selecting & Setting Variables

3.1.2 Analyzing & Tuning

42


Re-open the file that was saved earlier in DIY No 1.

LL2

R=L=6.436 nH

LL1

R=L=6.436 nH

CC3C=0.9833 pF

CC2C=0.9833 pF

CC1C=3.182 pF

TermTerm1

Z=50 OhmNum=1

TermTerm2

Z=50 OhmNum=2

43



To start manual tuning of certain parameters in a schematic, the “Tune Parameter” in the schematic should

be selected

44



Immediately after the “Tune” button is clicked, a Status Window and a Tuning Controller window will

appear

45



Add another rectangular plot to see the changes on S11 and S21 when the

Tuner is tuned.

46



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

47



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

48



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

49



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

50



To further observe the effect of capacitance values, the “Store” button can be pressed to hold the initial (old)

values before tuning

51



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

52


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:

53


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

54


CASE STUDY

The filter below is designed:

LL2

R=L=17.0 nH

LL1

R=L=17.0 nH

CC3C=6.2 pF

CC1C=6.2 pF

TermTerm1

Z=50 OhmNum=1

CC2C=10.0 pF

TermTerm2

Z=50 OhmNum=2

S_ParamSP1

Step=0.01 GHzStop=2.0 GHzStart=400 MHz

S-PARAMETERS

55


CASE STUDY

The transmission coefficient response is as follow:

0.6 0.8 1.0 1.2 1.4 1.6 1.80.4 2.0

-50

-40

-30

-20

-10

-60

0

freq, GHz

dB(S

(2,1

))

56


CASE STUDY

To zoom in the response on the Y-axis, double click

on the graph and edit the “Plot Options”

57


CASE STUDY

Zooming in on the Y-axis response;

0.6 0.8 1.0 1.2 1.4 1.6 1.80.4 2.0

-2.9-2.8-2.7-2.6-2.5-2.4-2.3-2.2-2.1-2.0-1.9-1.8-1.7-1.6-1.5-1.4-1.3-1.2-1.1-1.0-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.1

-3.0

0.0

freq, GHz

dB(S

(2,1

))

Readout

m1

Readout

m2

720.0M-3.136

m3

m1freq=dB(S(2,1))=-0.018

400.0MHz

m2freq=dB(S(2,1))=-0.080

440.0MHz

m3freq=dB(S(2,1))=-3.136

720.0MHz

3 dB rollout too far (more than 50 MHz

guard band)

58


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

59


CASE STUDY

BOLEH? AIYO!! VERY SUSAH LAH!!

60


What about using the “variable” feature?

Click on the “Variable” icon at the top tool bar

61


Adding Variables

Double click on the “VAR” icon to invoke the

window

62


Adding Variables

Add a parameter named “LCoil” and click on the “Tune/Opt/Stat/DOE”

option

Enable the “Tuning Status” and vary the max,

min and step values accordingly

63


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

64


Adding Variables

Change both of the inductor values to the

specific variable “LCoil”

The new variable, “LCoil” and its ranges will be

shown here

65


Adding Variables

Add another two variables using the way the

previous “LCoil” variable is defined

1. Cend for the left and right capacitor on the

edges

2. Cmid for the center capacitor

66


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

67


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)

68


Notice that there are now only 3 slider bars as

there are only 3 parameters to be tuned

69


Tune the variables and we will still get the

symmetrical LPF as required

70


TASK 1

Tune the filter to have the following characteristics: Insertion loss > -0.5 dB from 403 MHz to 440 MHz



Return loss > 15 dB in pass band

71


TASK 1 (Cont)

The current filter characteristic is shown as follow:

0.6 0.8 1.0 1.2 1.4 1.6 1.80.4 2.0

-50

-40

-30

-20

-10

-60

0

freq, GHz

dB(S

(2,1

))

400.0M-18.38m

m1

440.0M-80.24m

m2

550.0M-173.0m

m3

Readout

m4

dB(S

(1,1

))

500.0M-13.74

m5m1freq=dB(S(2,1))=-0.018

400.0MHz

m2freq=dB(S(2,1))=-0.080

440.0MHz

m3freq=dB(S(2,1))=-0.175

490.0MHz

m4freq=dB(S(2,1))=-5.440

750.0MHz

m5freq=dB(S(1,1))=-13.743

500.0MHz

The level of insertion loss meets the spec of having at least -0.5 dB

in passband

72

0.6 0.8 1.0 1.2 1.4 1.6 1.80.4 2.0

-50

-40

-30

-20

-10

-60

0

freq, GHz

dB(S

(2,1

))

400.0M-18.38m

m1

440.0M-80.24m

m2

550.0M-173.0m

m3

Readout

m4

Readout

m10

dB(S

(1,1

))

500.0M-13.74

m5

m1freq=dB(S(2,1))=-0.018

400.0MHz

m2freq=dB(S(2,1))=-0.080

440.0MHz

m3freq=dB(S(2,1))=-0.175

490.0MHz

m4freq=dB(S(2,1))=-5.440

750.0MHz

m5freq=dB(S(1,1))=-19.886

420.0MHz

m10freq=dB(S(2,1))=-12.768

840.0MHz


TASK 1 (Cont)


The level of return loss meets the spec of

having at least -10 dB in passband

73

0.6 0.8 1.0 1.2 1.4 1.6 1.80.4 2.0

-2.9-2.8-2.7-2.6-2.5-2.4-2.3-2.2-2.1-2.0-1.9-1.8-1.7-1.6-1.5-1.4-1.3-1.2-1.1-1.0-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.1

-3.0

0.0

freq, GHz

dB(S

(2,1

))

Readout

m6

Readout

m7

Readout

m8

720.0M-3.136

m9

m6freq=dB(S(2,1))=-0.018

400.0MHz

m7freq=dB(S(2,1))=-0.080

440.0MHz

m8freq=dB(S(2,1))=-0.175

490.0MHz

m9freq=dB(S(2,1))=-3.136

720.0MHz


TASK 1 (Cont) (Zooming in)


The frequency at -3 dB cutoff should be about 490 MHz instead of 720

MHz to allow for 50 MHz rolloff margin

74

m1freq=dB(S(2,1))=-0.018

400.0MHz

m2freq=dB(S(2,1))=-0.080

440.0MHz

m3freq=dB(S(2,1))=-0.175

490.0MHz

m4freq=dB(S(2,1))=-5.440

750.0MHz

m5freq=dB(S(1,1))=-13.743

500.0MHz0.6 0.8 1.0 1.2 1.4 1.6 1.80.4 2.0

-50

-40

-30

-20

-10

-60

0

freq, GHz

dB

(S(2

,1))

400.0M-18.38m

m1

440.0M-80.24m

m2

550.0M-173.0m

m3

Readout

m4

Readout

m10

dB

(S(1

,1))

500.0M-13.74

m5m1freq=dB(S(2,1))=-0.018

400.0MHz

m2freq=dB(S(2,1))=-0.080

440.0MHz

m3freq=dB(S(2,1))=-0.175

490.0MHz

m4freq=dB(S(2,1))=-5.440

750.0MHz

m5freq=dB(S(1,1))=-13.743

500.0MHz

m10freq=dB(S(2,1))=-12.768

840.0MHzm10freq=dB(S(2,1))=-12.768

840.0MHz


TASK 1 (Cont) (Zooming in)


The attenuation level at 2fc (2 x 420 MHz = 840

MHz) should have a value of > 35 dB from

att level at fc.

75


TASK 1 (Cont)

Tune the filter to have the following characteristics: Insertion loss > -0.5 dB from 403 MHz to 440

MHz (OK)



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)?

76


TASK 1 (Cont)Tune the by increasing/decreasing the inductor/cap values till specs are met

ads – application in filter design soh ping jack

Documents