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ADS Application Notes The Design of Oscillator Using ADS

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					                                   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
                                                                 ZHANG Hualiang, December 19, 2004


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.
                                                            ZHANG Hualiang, December 19, 2004

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
                                                                ZHANG Hualiang, December 19, 2004

   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.

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




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.




                                                                                  Defining
                                                                                  frequency range in
                                                                                  the simulation
                                                                                           ZHANG Hualiang, December 19, 2004

  The complete circuit schematic for the input and output matching and biasing network is given below
                                                                                   M LOC
                                                                                   T L6
                                                                                   Subst="M Sub1"
                                                                                   W=115.0 m il
                                                                                   L=Lopen m il




                                                                                                                                  T erm
                                                       M LIN                 M T EE                      M LIN                    T erm 1
                           DC_Feed                     T L4                  T ee1                       T L5                     Num =1
                           DC_Feed2                    Subst="M Sub1"        Subst="M Sub1"              Subst="M Sub1"           Z=50 Ohm
           V_DC                                        W=115.0 m il          W1=115.0 m il               W=115.0 m il
           SRC2                                        L=Lm m i l            W2=115.0 m il               L=Lout m i l
           Vdc=3 V                                                           W3=115.0 m il




                                                                                  Var
                                                                                         VAR
                                                                                  Eqn
                                                                                         VAR1
                                                                                                                          S-PA RA METERS
                                                                                         Lg=1117.89
                                                                                         Ls1=1356.59              S_Param
                                                                                         Ls2=1513.36              SP1
                                                                                                                  Start=1.5 GHz
                                                                                                                  Stop=3.5 GHz
                                                                                                                  Step=0.01 GHz
                                                                                  Var
                                                                                  Eqn    VAR
              M LEF                                                                      VAR2
              T L1                                                                       Lm =612.6666
              Subst="M Sub1"              pf_nec_NE76184A_19921216                       Lopen=53.3712
              W=115.0 m il                A1                                             Lout=137.386              MSub
              L=Lg m il
                                                                                                                  M SUB
                                                                                                                  M Sub1
                                                                                                                  H=62.0 m il
                                                                                                                  Er=4.5
                                                                                                                  M ur=1
              V_DC                            M LIN                     M LIN                                     Cond=5.8E+7
              SRC1                            T L2                      T L3                                      Hu=3.9e+034 m il
              Vdc=-0.5 V       DC_Feed        Subst="M Sub1"            Subst="M Sub1"                            T =1.38 m il
                               DC_Feed1       W=115.0 m il              W=115.0 m il                              T anD=0.017
                                              L=Ls1 m il                L=Ls2 m i l                               Rough=0 m il




 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
                                                                                                            ZHANG Hualiang, December 19, 2004

The complete circuit schematic for the harmonic balance simulation is given below
                                                                                            MLOC
                                                                                            TL6
                                                                                            Subs t="MSub1"
                                                                                            W =115.0 m il
                                                                                            L=Lopen m il




                                                                                                                                     Vout
                                                                                                                                                          R
                                                               MLIN                    MTEE                          MLIN                                 R1
                       DC_Feed                                 TL4                     Tee1                          TL5                                  R=50 Ohm
                       DC_Feed2                                Subst="MSub1"           Subst="MSub1"                 Subst="MSub1"
          V_DC                                                 W =115.0 m il           W 1=115.0 m il                W =115.0 m il
          SR C2                                                L=Lm mil                W 2=115.0 m il                L=Lout m il
          Vdc=3 V                                                                      W 3=115.0 m il




                                         Os cPort
                                         Os c1
                                         V=
                                         Z=1.1 Ohm                                                            HARM ONIC BALANCE             Va r     VAR
                                                                                                                                            Eq n
                                         Num Octav es=2                                                                                              VAR1
                                         Steps =10                                                      Harm onicBalanc e                            Lg=1117.89
                                         FundIndex=1                                                    HB1                                          Ls 1=1356.59
                                         MaxLoopGainStep=                                               Freq[1]=2.3 GHz                              Ls 2=1513.36
                                                                                                        Order[1]=3
                                                                                                        Ov ers am ple[1]=2
                                                                                                        MaxIters=10
                                                                                                        Arc Lev elMaxStep=10.0
                                                                                                        Os cMode=y es
                                                                                                        Os cPortN am e="Osc 1"
          MLEF
          TL1
          Subs t="MSub1"                pf _nec _NE76184A_19921216                                                                            Var
                                                                                                                                                      VAR
                                                                                                                                              Eq n
          W =115.0 m il                 A1                                                                                                            VAR2
          L=Lg mil                                                                                                                                    Lm =612.6666
                                                                                                             MSub                                     Lopen=53.3712
                                                                                                                                                      Lout=137.386
                                                                                                            MSU B
                                                                                                            MSub1
                                                                                                            H =62.0 m il
          V_DC                               MLIN                      MLIN
                                                                                                            Er=4.5
          SR C1                              TL2                       TL3                                  Mur=1
          Vdc=-0.5 V        DC _Feed         Subst="MSub1"             Subst="MSub1"
                            DC _Feed1                                                                       C ond=5.8E+7
                                             W =115.0 m il             W =115.0 m il                        H u=3.9e+034 m il
                                             L=Ls 1 mil                L=Ls 2 m il                          T=1.38 m il
                                                                                                            TanD =0.017
                                                                                                            R ough=0 mil



   5. Start circuit simulation.
   After constructing the circuit schematic, we can simulate the circuit. First we select Simulate
   Simulate the circuit
                                                             ZHANG Hualiang, December 19, 2004

   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…..

                                                                         Icons for selecting
                                                                         different display
                                                                         mode



                                                                              Icons for
                                                                              selecting
                                                                              different S-
                                                                              parameters



                                                                                Icons for
                                                                                selecting
                                                                                different
                                                                                units




                                                                                  Icons for
                                                                                  selecting
The final results is similar to the figure given below
                                                                                  markers




                                                                              markers
                                                                          ZHANG Hualiang, December 19, 2004

   The results of harmonic balance simulation is also given below.


                                 m4                       m3
                                 harmindex=0              harmindex=1
                                 dBm(Vout)=19.542         dBm(Vout)=6.799
                           m4                                                      Amplitude of the first
                     20                                                            harmonic (the
                                                                                   oscillation frequency )
                     10
                                           m3
         dBm(Vout)




                      0


                     -10


                     -20


                     -30
                           0.0       0.5   1.0      1.5       2.0   2.5      3.0

                                                 harmindex


   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.

				
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Description: Oscillator is used to generate electrical signals repeated (usually a sine wave or square wave) of electronic components. The composition of the circuit called the oscillation circuit. Able to convert DC output AC signal with a certain frequency electronic circuit or device. Many different types of incentives by the oscillation can be divided into self-excited oscillator, he oscillator; according to the circuit structure can be divided into RC oscillator, inductor-capacitor oscillator, crystal oscillator, tuning fork oscillator, etc.; according to output waveform can be divided into a sine wave, square wave, sawtooth and other oscillator. Widely used in electronic industry, medical, scientific research and so on.