investigation of hpm effects in voltage controlled oscillators
DESCRIPTION
Investigation of HPM Effects in Voltage Controlled Oscillators. Dr. John Rodgers and Cristina Allen University of Maryland Mid Progress Report July, 2010 Submitted to Dr. Bill Zimmerman Voss Scientific. ZX95-988 VCO Characteristics. I-V Curve (Diode-Like). Slope = 26.29 MHz/V. - PowerPoint PPT PresentationTRANSCRIPT
Investigation of HPM Effects in Voltage Controlled Oscillators
Dr. John Rodgers and Cristina AllenUniversity of Maryland
Mid Progress ReportJuly, 2010
Submitted to Dr. Bill ZimmermanVoss Scientific
ZX95-988 VCO Characteristics
-1.00 -0.86 -0.72 -0.58 -0.44 -0.30 -0.16 -0.02-0.1
-0.08
-0.06
-0.04
-0.02
6.93889390390723E-17
0.0200000000000001
Tuning Voltage (V)
Curr
ent (
A)
I-V Curve (Diode-Like)
-0.5 -0.1 0.3 0.7 1.1 1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9800
850
900
950
1000
1050
1100
Tuning Voltage (V)
Freq
uenc
y (M
Hz)
VCO Tuning Curve
Slope = 26.29 MHz/V
ZX95-988 VCO Characteristics
893.148481 893.217147666675 893.28581433335-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
Normal VCO Output Spectrum (Vtune = 0)
Frequency (MHz)
Spec
tral
Pow
er (d
Bm)
-0.5 -0.136666675331071 0.226666649337858-18-16-14-12-10
-8-6-4-20
VCO Phase Noise Line Width (3dB)~ 50 Hz
893.2 MHz + Delta F (kHz)Sp
ectr
al P
ower
(dBm
)
VCO Experiment
Bias TVCORF Oscillator
(Pulse Modulated)
25 GSa/sDigitizer
TuningInput
RFOutput
DC Bias5 VDC
•The nonlinear I-V characteristic of the tuning input provided evidence that this port may be unstable under pulsed RF excitation.•We characterized the VCO operation when the tuning voltage consists of an RF pulse superimposed on a DC bias.
1. A wideband bias tee was utilized to combine the DC and RF signals.2. The RF amplitude was stepped in 50 mV increments from 50 –
1000mV. The pulse width was fixed at 100 ms. Carrier frequencies 500 < f < 4000 MHz were investigated.
3. The VCO output waveform was digitized and recorded for each frequency and amplitude step. Subsequently, the FFT of the time-domain signal was calculated to give the RF spectrum.
4. Composite spectrograms were constructed to analyze how the VCO output varied with excitation parameters.
Results when RF was injected at frequencies near the VCO fundamental showing a frequency pulling and
broadening effect(Representative Spectrograms)
Freq 887MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000
893
893.2
893.4
893.6
893.8
894
Freq 903MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000893.2
893.4
893.6
893.8
894
894.2
894.4
894.6
Injected Carrier f = 887 MHz
Note: Normal VCO output frequency for Vtune = 0 is approximately 893.8MHz
Injected Carrier f = 903 MHz
More examples of effects when injected frequency is close to VCO fundamental frequency
Freq 891MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000891
891.5
892
892.5
893
893.5
894Freq 893MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000893
893.2
893.4
893.6
893.8
894
894.2
894.4
Freq 895MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000893.2
893.4
893.6
893.8
894
894.2
894.4
894.6
894.8
895
895.2Freq 897MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000
893
893.5
894
894.5
895
895.5
896
896.5
897
Phase Locking
Phase Locking
Spectral Broadening
Results with RF near the second harmonic of the VCO fundamental (1.784-1.804GHz)
Freq 1798MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000892.6
892.8
893
893.2
893.4
893.6
893.8
894
894.2
894.4
894.6Freq 1788MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000
893.3
893.4
893.5
893.6
893.7
893.8
893.9
894
894.1
Results with RF near the third harmonic of the VCO fundamental frequency (2.681-2.701GHz)
Freq 2691MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000893.5
893.6
893.7
893.8
893.9
894
894.1
894.2
894.3
Freq 2701MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000893
893.5
894
894.5
895
Freq 2681MHz / Vt 0V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000893.2
893.4
893.6
893.8
894
894.2
894.4
894.6
Freq 2746MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000
914.4
914.6
914.8
915
915.2
915.4
915.6
915.8
Supplemental Data
• The following series of slides shows examples of the results for various tuning voltages and injection frequencies:
Fundamental Frequency Range(908-928MHz)
Note: Average VCO output for Vtune = 0.5V is 915.2MHz
Freq 924MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000915
915.05
915.1
915.15
915.2
915.25
915.3
915.35
915.4
915.45
Fundamental Frequency Injection(908-928 MHz)
Behavior when injected frequency is close to VCO output frequency @ Vt = 0.5VFreq 912MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000912
912.5
913
913.5
914
914.5
915
915.5Freq 914MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000
914
914.5
915
915.5
916
Freq 916MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000914.4
914.6
914.8
915
915.2
915.4
915.6
915.8
916
916.2Freq 918MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000915
915.5
916
916.5
917
917.5
918
Second Harmonic Frequency(1.826-1.846GHz)
Freq 1828MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000914.95
915
915.05
915.1
915.15
915.2
915.25
915.3
915.35
915.4
915.45Freq 1840MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000914.8
914.9
915
915.1
915.2
915.3
915.4
915.5
915.6
915.7
Representative of 1.826,1.828, and 1.832GHz
Representative of 1.836-1.846GHz
Second Harmonic Frequency(1.826-1.846GHz)
Only plot that deviated from representative plot. Injected frequency is the second harmonic of VCO output.
Freq 1830MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000914.8
914.9
915
915.1
915.2
915.3
915.4
Third Harmonic Range(2.744-2.764GHz)
Freq 2754MHz / Vt 0.5V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000
914.4
914.6
914.8
915
915.2
915.4
915.6
915.8
Fundamental Frequency (925-945MHz)
Freq 927MHz / Vt 1V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000932.5
932.55
932.6
932.65
932.7
932.75
932.8
932.85
932.9
932.95
933Freq 939MHz / Vt 1V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000932.2
932.3
932.4
932.5
932.6
932.7
932.8
932.9
933
933.1
933.2
Representative of 925-925MHz Representative of 935-945MHz
Note: VCO frequency for Vt = 1.0V is 932.75MHz
Vt = 1.0 VBehavior when injected frequency is close to VCO output frequency
Freq 931MHz / Vt 1V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000931
931.2
931.4
931.6
931.8
932
932.2
932.4
932.6
932.8
933Freq 933MHz / Vt 1V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000932.4
932.5
932.6
932.7
932.8
932.9
933
933.1
933.2
933.3
Freq 935MHz / Vt 1V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000932.5
933
933.5
934
934.5
935
Second Harmonic Frequency(1.860-1.880GHz)
Only plot that deviated from representative plot. Injected frequency is double VCO output frequency (actual second harmonic of VCO output).
Freq 1866MHz / Vt 1V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000932.2
932.3
932.4
932.5
932.6
932.7
932.8
932.9
933
933.1
933.2
Third Harmonic Frequency(2.795-2.815GHz)
Freq 2805MHz / Vt 1V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000931.5
932
932.5
933
933.5
934
Third Harmonic Frequency(2.795-2.815GHz)
Only plot that deviated from representative plot. Injected frequency is third VCO output frequency (actual third harmonic of VCO output).
Freq 2799MHz / Vt 1V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000931.5
932
932.5
933
933.5
934
Third Harmonic Frequency(2.795-2.815GHz)
This plot had the overall shape of the representative plot, but showed a the highest spectral broadening.
Freq 2801MHz / Vt 1V
RF Voltage (V)
Freq
uenc
y (M
Hz)
100 200 300 400 500 600 700 800 900 1000931.5
932
932.5
933
933.5
934
Conclusions• RF coupled into the diode at the tuning voltage input drives
the P-N junction into nonlinearity. This process generates spurious voltages which produce unstable VCO operation.
• The VCO is particularly sensitive to RF pulses when the carrier frequency is near harmonics of the VCO output.
• In the most sensitive cases, RF pulse amplitudes as low as 100 mV were enough to drive instability in the VCO.
• The effects observed in the experiments can be categorized generally as follows:1. Spectral broadening2. Phase locking of the VCO to the RF carrier frequency3. Generation of nonlinear frequency products
Current and Near-Future Efforts
• We are now developing nonlinear circuit models based on the results of the data presented here.
• Initially, we will model direct injection of RF into the tuning voltage input and compare the numerical and experimental results. This will provide initial validation of the circuit models.
• The VCO circuit will be tested in the UMD radiation chamber where the RF coupling, transmission and effects will be characterized.
• Finally, the results of the chamber tests will be compared with simulations using a combination of the deterministic circuit effects models and the Voss coupling models.