Lab 3. Oscillator design

Objective: 1. Varactor model

2. Resonator design

3. Reflection amplifier design Varactor model The equivalent circuit of the varactor can be found in the datasheet.

1. Create a new schematic and name it “SMV1145.dsn”. Draw a circuit as shown.

VARVAR1

Rs=0.60Ls=0.7Cp=0

EqnVar

Diode_ModelSMV1145

AllParams=Eg=1.11Xti=3Trise=Tnom=27AllowScaling=noFcsw=Vjsw=

Msw=Cjsw=Ikp=Ns=Gleaksw =Rsw=Jsw=Ffe=1Af=1Kf=0Nbvl=1Ibvl=0Nbv=1Ibv=1e-3Bv=0

Ikf=0Nr=2Isr=0Imelt=Imax=Fc=0.5M=1.1Vj=2.5 VCjo=41.8e-12Cd=Tt=0N=1Gleak=Rs=0Is=1.00e-14

PortP2Num=2

LLs

R=L=Ls nH

CCpC=Cp pF

PortP1Num=1

RRsR=Rs Ohm

DiodeDIODE1

Mode=nonlinearTrise=Temp=Region=Scale=Periph=Area=Model=SMV1145

2. In view, switch from the schematic view to the symbol view.

Draw the varactor symbol as shown.

3. Create a new schematic “varactorTest.dsn”. Go to the library.

In the component library, insert SMV1145 varactor diode.

Insert the components as shown.

SMV1145X12

1

V_DCSRC1Vdc=Vtune V

DC_FeedDC_Feed1

TermTerm1

Z=50 OhmNum=1

Insert VAR and create a new variable “vtune=1”.

VARVAR1Vtune=1.0

EqnVar

Insert a S-parameter simulation controller.

S_ParamSP1

Step=Stop=Start=

S-PARAMETERS

Double click on the S-parameter simulation controller. Set Sweep Type to 185 MHz and Frequency 185 MHz. In the Parameters tab, check both Y and Z parameters. Click OK.

ParamSweepSweep1

Step=Stop=8Start=0SimInstanceName[6]=SimInstanceName[5]=SimInstanceName[4]=SimInstanceName[3]=SimInstanceName[2]=SimInstanceName[1]="SP1"SweepVar="Vtune"

PARAMETER SWEEP

Insert a parameter sweep controller. Double click on the parameter sweep controller. Set Parameter to sweep to Vtune, Sweep Type to Linear, Start = 0 , Stop = 8 and Num. of pts. = 51. In the simulation tab, enter SP1 to Simulation 1. Click ok. Simulate.

3. In the data display window, insert the equation:

Eqn C=1/(-1*imag(Z(1,1))*2*pi*freq)

Insert a rectangular plot. Choose C and click “>>Add Vs,,>>”. Select Vtune in the varactor test dataset. Click OK. Click OK again.

1 2 3 4 5 6 70 8

1E-11

2E-11

3E-11

4E-11

0

5E-11

Vtune

C

Since the capacitance vs. vtune in the datasheet is in log scale, we need to change our plot to log scale. Double click on the plot. In the Plot Options tab, check Log. Uncheck auto scale, and enter Y-axis range as shown. Click OK.

1 2 3 4 5 6 70 8

1.0000000E-11

1.0000000E-10

1.0000000E-12

1.0000000E-10

Vtune

C

It can be seen that the simulated capacitance is almost identical from the datasheet.

Resonator Design 1. The design specification:

0 177 MHzf = Phase noise < -100 dBc/Hz @ 10 KHz

2. Create a new schematic and name it “phaseNoise” 3. From System-PLL component, insert a PhaseNoiseMod component. Insert a PM_Dmod_Tuned.

Set the parameters of both components as shown. We start with QL = 30 and

PhaseNoiseModMOD1

QL=30NF=2 dBFcorner=30 MHzRout=50 OhmFnom=f0

NoiseMod

Phase

PNoise_OL

PM_DemodTunedDEMOD1

Rout=50 OhmFnom=f0Sensitivity=180/pi

Insert a source P_1Tone and set the parameters as shown.

P_1TonePORT1

Freq=f0P=polar(dbmtow(10),0)Z=50 OhmNum=1

Insert VAR and set the variable f0 as shown.

VARVAR1f0=177 MHz

EqnVar

Insert a HB simulation controller and set Parameter as shown. Name the output node “PNoise_OL”.

Double click on HB simulation controller, In Freq tab, enter f0 in for Frequency, 7 for Order click Add. Cleck “Nonlinear noise”. In Noise(1) tab, enter the noise frequency as shown. Enter the “PNoise_OL” for the nodes doe noise parameter calculation in Noise(2) tab. Click OK.

Simulate. In the data display window, insert a equation as shown

Eqn Pnoise = 10*log10(0.5*PNoise_OL.noise**2) Insert a rectangular plot, insert Pnoise into the Traces. Click OK.

Double click on the plot. In Plot Options tab, check Log scale for x-axis. Click OK. Insert a maker to the plot. In can be seen that the phase noise @ 10kHz is less than -100dBc as desired. Hence, the Q factor of resonator circuit must be greater than 30.

1E3 1E4 1E5 1E6 1E71E2 4E7

-150

-100

-50

-200

0

noisefreq, Hz

Pno

ise m1

m1noisefreq=Pnoise=-100.718

10.02kHz

4. Create a new schematic and name it “resonatorTest”. 5. Draw a schematic as shown. We use the capacitor and inductor component with Q

factor.

6. Insert a VAR (Variables) as shown. VARVAR1

Cc=6Vtune=3.0

EqnVar

7. Insert a S-parameter simulation controller.

S_ParamSP1

Step=Stop=350 MHzStart=10 MHz

S-PARAMETERS

Double click on the controller. In frequency Tab, choose sweep type to be Linear. Set Start, Stop and Num. of pts. to 10 MHz , 350 MHz and 101 points respectively. In Parameters tab, check all parameters, i.e. S-,Y-,Z-parameter and Group delay. Click OK.

8. Insert a Parameter Sweep controller. Double Click on the controller.

ParamSweepSweep1

Step=1Stop=15Start=3SimInstanceName[6]=SimInstanceName[5]=SimInstanceName[4]=SimInstanceName[3]=SimInstanceName[2]=SimInstanceName[1]="SP1"SweepVar="Cc"

PARAMETER SWEEP

Enter Cc as a Parameter to sweep, and Sweep type “Linear”, Set Start, Stop and Num. of pts. to 3, 15 and 13 points respectively. Click on Simulations tab, enter SP1 in Simulation1. Click OK.

Simulate.

9. In the data display window, add S11 in dB scale to a rectangular plot. Click OK.

50 100 150 200 250 3000 350

-15

-10

-5

-20

0

freq, MHzdB

(S(1

,1))

Insert the Equation for Q-factor.

Eqn Q=pi*freq*(S.delay(1,1))

Plot Q-factor in a rectangular plot. Click OK. Insert two makers into the Q-factor plot.

50 100 150 200 250 3000 350

20

40

60

80

100

0

120

freq, MHz

Q

m1

m2

m1freq=Q=33.587Cc=5.000000

173.2MHzm2freq=Q=8.564Cc=10.000000

149.4MHz

To get the Q value greater than 30, the coupling capacitor has to be less than 5 pF as it can be seen from the Q-factor plot.

Active circuit design 1. A PNP transistor 2SC3356 is chosen to be an active device

The supply voltage is 5 V. The transistor operating point is shosen to be Vce = 2.5 V with Ic = 8 mA. 2. Create a schematic and name it “bias”. 3. Insert a 2SC2256 transistor and a transistor bias utility. Connect all components

as shown.

4. In the DesignGuide menu, choose Amplifier.

Choose Transistor bias utility in Tools. Enter Vcc = 9 V, Vce = 2.5 V and Ic = 8. Click Design.

Select network number 3 for bias network. Click OK.

Back into the main schematic. Click on DA_Bias and click on push down hierarchy.

The bias circuit is shown below. All resistors will be chosen to practical values.

PortP4Num=4

PortP3Num=3

PortP2Num=2Port

P1Num=1

RR4R=489.197485 Ohm

RR3R=62.021403 Ohm

RR2R=1.385996 kOhm

RR1R=250 Ohm

Reflection oscillator design 1. Create a new schematic and call it “osctest” 2. Draw a schematic as shown. We will use real capacitors in this simulation. The

Murata GRM03 series is chosen for all capacitor values. We also use Murata LQW18 series as our inductors.

To change the value, double click at the capacitor.

Change all capacitor values and inductor value as shown.

GRM03C14PartNumber=GRM0335C1E680JD01

GRM03C16PartNumber=GRM0335C1E560JD01pb_nec_2SC3356_19921101

Q8

GRM03C15PartNumber=GRM0335C1E101JD01

GRM03C17PartNumber=GRM0335C1E220JD01

RR5R=50 Ohm

TermTerm1

Z=50 OhmNum=1

DC_BlockDC_Block1

VARVAR1Vtune=1

EqnVar

RR2R=1.4 kOhm

RR3R=60 Ohm

RR1R=250 Ohm

RR4R=500 Ohm

LQW18L4PartNumber=LQW18ANR33G00

V_DCSRC1Vdc=5.0 V

CC12C=1000 pF

Click simulate. In the data display plot, plot magnitude and phase of S11.

0

5

-5

10

dB

(S(1

,1))

m1freq=dB(S(1,1))=9.809

158.8MHz

20 40 60 80 100 120 140 160 180 200 220 2400 260

-100

-50

-150

0

freq, MHz

ph

ase

(S(1

,1))

It can be seen that the S11 is greater than 1 (0dB) around desired frequency and the phase slope is negative. Hence, the circuit will oscillate when a resonator is connect at the port.

58 pF

68 pF

330 nH 100 pF

Complete oscillator circuit

1. Deactivate all S-parameter components 2. Add the resonator part as shown. Insert a OscPort between the resonator and the

active device port. Set the capacitor and the inductor values as shown.

Insert a HB simulation controller. Double click on the HB simulation controller. Check on Nonlinear noise and Oscillator. In Params Tab, enter 8 for Fundamental oversample. In Freq Tab, enter 160 MHz for Frequency and 7 for Order.

10 pF 100 pF 7 kOhm

33 nH

In Noise(1) tab, enter Log Sweep Type. Enter 10 Hz, 10 MHz and 10 for Start, Stop and Pts./decade respectively. In Noise (2) tab, enter “vout” for nodes for noise parameter calculation.

Click OK. Simulate. In the data display window, insert a rectangular plot. Add dBm(vout) vs freq to Traces. Click OK.

0.2 0.4 0.6 0.8 1.00.0 1.2

-120

-100

-80

-60

-40

-20

-140

0

freq, GHz

dBm

(vou

t)

m2

m2freq=plot_vs(dBm(vout), freq)=-19.858

159.4MHz

It can be seen from the plot that the frequency of oscillation is 159.4 mHz at Vtune = 1 V. Double click on the HB simulation controller. In the sweep tab, enter Vtune for Parameter to sweep. Choose Linear as the Sweep type. Enter 0.5, 5, and 11 for Start, Stop and Num ot pts. respectively. Click ok and simulate.

In the data display window, enter the equation

Eqn mix2 = freq[::,1] Insert a rectangular plot. Add mix2 vs HB.Vtune. into Traces. Click OK. It can be seen that the output frequency varies between 152.3 MHz and 200.3 MHz with 0.5 to 5 V of the tuning voltage.

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.50.5 5.0

1.6E8

1.7E8

1.8E8

1.9E8

2.0E8

1.5E8

2.1E8

HB.Vtune

mix

2

m3

m4

m3indep(m3)=plot_vs(mix2, HB.Vtune)=1.523E8

0.500m4indep(m4)=plot_vs(mix2, HB.Vtune)=2.003E8

5.000

Insert a rectangular plot, Add pnmx vs noisefreq to Traces. Click OK. Double click on the plot. In plot option tab, change X-axis to Log scale. Click Ok.

1E2 1E3 1E4 1E5 1E61E1 1E7

-150

-100

-50

-200

0

noisefreq, Hz

pnm

x m5

m5indep(m5)=plot_vs(pnmx, noisefreq)=-104.148Vtune=5.000000

1.000E4

It can be seen that the phase noise at 10 KHz is about -100 dBc as desired.