2.3 ghz ads_oscillator

ZHANG Hualiang, December 19, 2004

ADS Application Notes

Wireless Communication Laboratory Department of Electrical and Electronic Engineering Hong Kong University of Science and Technology

The Design of Oscillator Using ADS


Introduction This application note describes the design procedure of oscillator working at 2.3GHz using agilent’s ADS. In this notes, I will show the design procedures step by step.

Design procedures

1. Open ADS program. Choose “File New Project” to open a new project.


2. In the new schematic of the project, we use the library icon to get the transistor model for the oscillator

3. In this oscillator design we will use nec_NE76184A_19921216 as the FET transistor. So we choose the model for the transistor from the RF_transistor_library Packaged GaAs FETs pf_nec_NE76184A_19921216.

Icon for the transistor


4. We are now going to construct the circuit for input output matching and biasing network. Because we need to use the transmission line to do the interconnect, all these line’s parameters can be defined by using the TLines_Microstrip category as shown in the below figures.

Then we need to start the S-parameters simulation. The setup for the S-parameters simulation can be found in the Simulation_S_param category. We need to define frequency range, and terms for simulation.

The icon for Microstrip Lines Icon for defining the substrate Icons for different lines

Defining frequency range in the simulation


The complete circuit schematic for the input and output matching and biasing network is given below

MLINT L4

L=Lm mi lW=115.0 milSubst="MSub1"

MLINTL5

L=Lout mi lW=115.0 m ilSubst="MSub1"

MLOCT L6

L=Lopen m ilW=115.0 m ilSubst="MSub1"

M T EET ee1

W3=115.0 milW2=115.0 milW1=115.0 milSubst="MSub1"

T ermT erm1

Z=50 OhmNum=1DC_Feed

DC_Feed2V_DCSRC2Vdc=3 V

VARVAR1

Ls2=1513.36Ls1=1356.59Lg=1117.89

EqnVar

VARVAR2

Lout=137.386Lopen=53.3712Lm=612.6666

EqnVar

S_ParamSP1

Step=0.01 GHzStop=3.5 GHzStart=1.5 GHz

S-PARAMETERS

MSUBMSub1

Rough=0 m ilT anD=0.017T =1.38 milHu=3.9e+034 milCond=5.8E+7Mur=1Er=4.5H=62.0 mil

MSub

DC_FeedDC_Feed1

pf_nec_NE76184A_19921216A1

MLEFT L1

L=Lg m ilW=115.0 m ilSubst="MSub1"

MLINT L2

L=Ls1 milW=115.0 m ilSubst="MSub1"

MLINT L3

L=Ls2 mi lW=115.0 m ilSubst="MSub1"

V_DCSRC1Vdc=-0.5 V

To further prove the performance of the designed oscillator, we need to do the harmonic simulation to see the overall frequency performance of the oscillator. The setup for the harmonic simulation can be found in the Simulation_S_param category. We need to define frequency range, and terms for simulation.

Defining harmonic Simulation frequency


The complete circuit schematic for the harmonic balance simulation is given below

Vout

VARVAR2

Lout=137.386Lopen=53.3712Lm=612.6666

EqnVar

VARVAR1

Ls2=1513.36Ls1=1356.59Lg=1117.89

EqnVar

MSUBMSub1

Rough=0 milTanD=0.017T=1.38 milHu=3.9e+034 milCond=5.8E+7Mur=1Er=4.5H=62.0 mil

MSub

HarmonicBalanceHB1

OscPortName="Osc1"OscMode=y esArcLev elMaxStep=10.0MaxIters=10Ov ersample[1]=2Order[1]=3Freq[1]=2.3 GHz

HARMONIC BALANCE

OscPortOsc1

MaxLoopGainStep=FundIndex=1Steps=10NumOctav es=2Z=1.1 OhmV=

V_DCSRC1Vdc=-0.5 V

MLINTL3

L=Ls2 milW=115.0 milSubst="MSub1"

MLINTL2

L=Ls1 milW=115.0 milSubst="MSub1"

MLEFTL1

L=Lg milW =115.0 milSubst="MSub1" pf _nec_NE76184A_19921216

A1

DC_FeedDC_Feed1

RR1R=50 Ohm

V_DCSRC2Vdc=3 V

DC_FeedDC_Feed2

MTEETee1

W 3=115.0 milW 2=115.0 milW 1=115.0 milSubst="MSub1"

MLOCTL6

L=Lopen milW=115.0 milSubst="MSub1"

MLINTL5

L=Lout milW=115.0 milSubst="MSub1"

MLINTL4

L=Lm milW=115.0 milSubst="MSub1"

5. Start circuit simulation. After constructing the circuit schematic, we can simulate the circuit. First we select Simulate Simulate the circuit


Then the data widow is prompted, you can choose the display mode for the simulation results (in Table, polar axis, smith chart …) , and can choose the desired S-parameter in dB, dBm…..

The final results is similar to the figure given below

Icons for selecting different display mode

Icons for selecting different S-parameters

Icons for selecting different units

Icons for selecting markers

markers


The results of harmonic balance simulation is also given below.

m3harmindex=dBm(Vout)=6.799

1m4harmindex=dBm(Vout)=19.542

0

0.5 1.0 1.5 2.0 2.50.0 3.0

-20

-10

0

10

-30

20

harmindex

dBm

(Vou

t)

m3

m4

From it we can see that the amplitude of peak oscillation frequency is 6.799dBm.

Conclusion An oscillator designed on 2.3GHz is given in this notes based on the ADS simulation. It can be seen that by the help of the ADS various simulations can be done easily. Both the cost and the iterations of the design process have been decreased by using this powerful EDA tool.

Amplitude of the first harmonic (the oscillation frequency )

2.3 ghz ads_oscillator

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