Download A Wide Locking Range Differential Colpitts Injection

LC-Tank Colpitts Injection-Locked Frequency
Divider With Record Locking Range
S.-L. Jang, Senior Member, IEEE, S.-H. Huang, C.-F. Lee, and
M.-H. Juang, Senior Member, IEEE
Presenter: 楊 子 岳
2017/5/23
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Abstract
• The ILFD is based on a VCO with two embedded injection
MOSFETs for coupling external signal to the resonators.
• The new VCO is composed of two single-ended VCOs coupled
with cross-coupled MOSFETs and a transformer.
• Supply voltage of 1.5 V, free-running frequency is tunable from
5.85 to 6.17 GHz.
• Incident power of 0 dBm the locking range is about 7.1 GHz
(65.4%) from the incident frequency 7.3 to 14.4 GHz.
• The ILFD has a record locking range percentage among
published divide-by-2 LC-tank ILFDs.
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Outline
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•
•
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Introduction
Circuit Design
Measurement Results
Conclusion
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Introduction
• The main concern for the frequency divider design is large
locking range with low power consumption.
• For high speed and low power operation LC-tank ILFD is the
most suitable one among various types of frequency dividers
because operating frequency is determined by the resonant
frequency.
• The ILFD is based on a new VCO topology and two injection
MOSFETs for coupling external injection signal to lock the
VCO output signal.
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Circuit Design
• Schematic of a single-ended VCO and its equivalent LC resonator
•Transistors (M5,M6) are configured to
provide negative resistance Rin to
compensate for the tank loss.
•The VCO provides two unbalanced
outputs from the terminals of inductor
L2 . The varactors are used to tune
VCO output frequency.
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Circuit Design
• Schematic of the proposed ILFD
The cross-coupled transistors are
used to couple the two single-ended
VCOs to form a differential VCO and
also provide a net negative
resistance to the VCO to compensate
for the loss due to the resistance in
inductors, varactors, and injection
MOSFETs.
L1,L2 are used to couple
differentially the two single-ended
VCOs.
k is the coupling coefficient
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Circuit Design
• To obtain a wide-locking range:
1) firstly appropriately choosing the location of injection
MOSFET is important, because the location affects the
efficiency of injection.
2) Secondly, the size of Min is optimized, as the channel width
W of Min is increased , the resonator Q-factor is degraded
and the voltage swing of ILFD output decreases, these lead to
the increase in locking range, however if W is too large, the
ILFD can not oscillate because two output ports of inductor
are shorted.
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Circuit Design
• Simulated
Fig. 2. Simulated ac input
gate voltage (bottom plot)
of M and ac output voltages
(top plots) of the buffers at
injection-locked condition
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Measurement Results
Fig. 4. Measured freerunning frequency tuning
range of the ILFD circuit.
•tunable from 5.85 to 6.17
GHz with a tuning voltage
from 0 to 1.5 V when dc bias
voltage Vinj is 1.5 V
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Measurement Results
Fig. 5. Measured and
simulated relationship
between input sensitivity and
operating frequency at the
supply voltage of 1.5 V
At 1.5 V, a signal power of 0
dBm provides a locking
range of 7.1 GHz, from 7.3
to 14.4 GHz
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Measurement Results
Fig. 6. Measured phase noises of the
free-running, injection-locked and
injection-reference. Injection power =
0 dBm, f = 6.13 GHz.
The phase noise of freerunning oscillator at 1 MHz
offset is about 104.5 dBc/Hz.
After external power
injection,the phase noise of
ILFD is about 134.8 dBc/Hz
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Conclusion
• A new LC oscillator based ILFD has been proposed and
fabricated in TSMC 0.18 um CMOS technology.
• It consists of two single-ended Colpitts VCOs coupled with
cross-coupled MOSFETs and transformer to form a
differential circuit.
• The free-running frequency operates from 5.85 to 6.17 GHz
at the supply voltage of 1.5 V and power consumption of 7.65
mW. The locking range is from 7.3 to 14.4 GHz which is up to
65.4% when input power is 0 dBm.
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Thanks for your attention
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