8/6/2019 Design of Tunable Filters

1/32

Designing High Performance, Low

Cost Tunable Bandpass Filters

Authored by:

Stefano Biagiotti, Giancarlo Guida, Alain MichelAnsoft Corporation

Ansoft 2003 / Global Seminars: Delivering Performance

Presentation #13

8/6/2019 Design of Tunable Filters

2/32

Overview

w Short description of previous generation filter designsw Electrical performances, technology, highlights - lowlights

w Filter enhancement

w New performances, cost reduction, reproducibility

w Implementation

w Filter synthesis

w Tuning range verification

w Sensitivity analysis

w Completion of the circuit

w NL analysis

w Statistical analysis

w EM analysis

w HFSS + DESIGNER

w Benefits

w Conclusions

8/6/2019 Design of Tunable Filters

3/32

Old Filter: Physical Implementation

PCB with 16 diodes

mounted by hand

Handmade coil (Ag. 2mm)

Resistive TRIMMERS

CapacitiveTRIMMERS

Filter to redesign

8/6/2019 Design of Tunable Filters

4/32

Old Filter: Electrical Performance(for Each Stage)

w Frequency range 118 - 137MHz

w Bandwidth 5MHz

w Insertion Loss > -2.5dB

w Return Loss < -15dB

w Out of band rejection > -45dB @ F0 20MHz

w Voltage tuning 1 - 10V

w Allowed max input power > 25dBm

Number of devices producedNumber of devices producedper year about 300per year about 300

8/6/2019 Design of Tunable Filters

5/32

Old Filter: Highlights, Lowlights

w Highlightsw High value of quality factor

w Electrical performances well matched

w Mechanical dimensions

w Lowlights

w 90% hand-made

w Manual filter tuning needed for each device

w Reproducibility

w Production time

Average time to manufactureAverage time to manufacture

a single device was 1.5 houra single device was 1.5 hour

8/6/2019 Design of Tunable Filters

6/32

Reasons to Modernize

w Obsolescence of componentsw Obsolescence of components used for the main project

and new product specification involved also redesigning atunable pass band filter.

w Costsw The new Radio Ground Station had to cost much less;

which provided more incentive to redesign the filter.

w Outsourcingw Devices require high reproducibility in order to be

manufactured by outsourcing, hence, designers mustavoid manual tuning operations whenever possible.

8/6/2019 Design of Tunable Filters

7/32

New Filter Specifications(for Each Stage)

w New performances:

w Frequency range 108 - 156MHz

w Bandwidth < 10MHz

w Insertion Loss > -2.5dB (-3dB 108 - 118MHz)

w Return Loss < -15dB

w Out of band rejection < -45dB @ F0 + 42.8MHz

w Voltage tuning 2 - 18V

w Allowed max input power > 25dBm

w Cost reduction:w Minimize manual tuning; automate manufacturing

w Reproducibility:

w Technology selection

8/6/2019 Design of Tunable Filters

8/32

New Filter Topology

w Why Combline Transformer topology?

We can tune the

filter with some

VARICAP diodes

One of the best topologies for small tolerances!!

With MS Tech.

we avoid one of

the manual tuning

processes

8/6/2019 Design of Tunable Filters

9/32

Filter Synthesis: Enter specifications

8/6/2019 Design of Tunable Filters

10/32

Port1

Port2

Filter Synthesis Output

We can complete thelayout by changing the

CAPs footprint...

Port1 Port2

4321

C1

Q=Q1

C1

Q=Q1

Layout Output

Schematic Output

8/6/2019 Design of Tunable Filters

11/32

CAPs properties window from layout

Footprint Library

Filter Synthesis CompletionChanging the current footprint of

the capacitors

8/6/2019 Design of Tunable Filters

12/32

Port1 Port2

4321

C1

Q=Q1

C1

Q=Q1

Filter Synthesis: Circuit Simulation

Simulation results of circuit

created from Filter Synthesis

8/6/2019 Design of Tunable Filters

13/32

Tuning Verification: Capacitor range

The tuning is used to validate the frequency range of the filter.

Choose Sweep/Accumulate or Real Time tuning

8/6/2019 Design of Tunable Filters

14/32

Tuning Verification: Varicap Bias range

We can also complete the schematic

by changing the CAPs Q factor...

8/6/2019 Design of Tunable Filters

15/32

Sensitivity Analysis

124.9MHz 134MHz

8/6/2019 Design of Tunable Filters

16/32

Sensitivity Analysis@124.9MHz

0.04dB

0.6dB0.25dB

7.5dB

S2 +/-0.1mm

w1 +/-0.1mm

w2 +/-0.1mm

W2 critical size!

S1 +/-0.1mm

8/6/2019 Design of Tunable Filters

17/32

Circuit Completion: Schematic and Layout

8/6/2019 Design of Tunable Filters

18/32

Circuit Completion : NL Simulation

8/6/2019 Design of Tunable Filters

19/32

Circuit Completion: Tuning biasVs=2.3VF=108MHz

Vs=16.5VF=156MHz

Vs=7.3VF=130MHz

S21

S11, S21, S22

8/6/2019 Design of Tunable Filters

20/32

Circuit Completion : Layout

8/6/2019 Design of Tunable Filters

21/32

Statistical Analysis: Define Setup

Add parameters to

Statistical Analysis

Add Statistical

Analysis setup

Define Goal

8/6/2019 Design of Tunable Filters

22/32

Statistical Analysis Freq=108MHz

Yield=55% for S11

8/6/2019 Design of Tunable Filters

23/32

Statistical Analysis Freq=156MHz

Yield=46% for S11

8/6/2019 Design of Tunable Filters

24/32

EM Analysis: full board simulation

Automatic generation of the full board forAutomatic generation of the full board for

EM cosimulation or cooptimizationEM cosimulation or cooptimization

8/6/2019 Design of Tunable Filters

25/32

EM Analysis: Compare Simulation

Port1 Port2

PBFLayout

n2 n11

n111 n214

n118 n223

n125

n138 n239

n247 n248

n149 n150

n261 n162

n163 n264

n265

n178 n180

n283 n284

n185 n187

U1EM Layout

BB439

D1

BB439D2

BB439D3

BB439

D4

BB439D5

BB439

D6

BB439

D7

BB439D8

RCI_0

603_

4703G

47

0kOhm

RCI_0603_

4703G

470kOhm

GRM39

C0G120J050

12pF

GRM39

C0G120J050

12pF

+-

Vs

+-

Vs

EM setup Analysis andEM setup Analysis and

Frequency areFrequency are

automatically set or definedautomatically set or defined

by the userby the user

8/6/2019 Design of Tunable Filters

26/32

Ansoft Designer + HFSS

How can we test the prototype?

SMA Connector

We need a 3D full wave

model to take in count itseffects on the device...

HFSS v9 Model

8/6/2019 Design of Tunable Filters

27/32

Ansoft Designer + HFSS

SMA effects

8/6/2019 Design of Tunable Filters

28/32

DESIGNER + HFSS

HFSS results for SMA connectorHFSS results for SMA connector

8/6/2019 Design of Tunable Filters

29/32

New Filter: Physical Implementation (1)

Data exportData exportfor direct manufacturingfor direct manufacturingExtended Gerber and NC Drill filesExtended Gerber and NC Drill files

8/6/2019 Design of Tunable Filters

30/32

New Filter: Physical Implementation (2)

8/6/2019 Design of Tunable Filters

31/32

Benefits

w Low cost device (about 20 EURO)

w Production time 10min (compared to 1.5 hour)!

w Extremely reproducible (no manual tuning)!

w Electrical performances matched very well!

Number of devices producedNumber of devices produced

per year about 1000per year about 1000

8/6/2019 Design of Tunable Filters

32/32

Conclusionsw We have presented a design and development of a MS PBF using

ANSOFTs EDA software.w With DESIGNER v1.1 we have been able to do:

w Filter synthesis

w Linear simulation (S-parameter extraction)

w Tuning

w Non Linear simulation (VARICAPs effect, Intermodulation)

w Statistical Analysis

w Layout planar EM analysis

w Easy integration in a design of a 3D full wave simulation (SMAconnector) made in ANSOFT HFSS

By applying software tools early in the development process,By applying software tools early in the development process,problems can be quickly identified and resolved prior toproblems can be quickly identified and resolved prior to

production, greatly decreasing time to market!!production, greatly decreasing time to market!!