1. Design of a High-Precision
Complex Quadrature Modulator
Computer Logical Design Laboratory
S1160126 Hirota Takahashi
Supervisor: Tsuneo Tsukahara

2. Contents
• Introduction
– Background
– Purpose of This Research
• Approach
– Proposed Circuits
– Simulation Results
• Future Tasks and Schedule
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3. Devices using wireless
communication
Cloud Computing
Radio-wave resources are limited
Cognitive Radio (CR)
Key Technology
Software Defined Radio (SDR)
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4. Blockdiagram of a SDR
Transceiver
Subject of This Research
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5. Degradations of Error Vector
Magnitude
( Sine Wave ) Main factors degraded Error Vector Magnitude ?
LO Amplitude Error
LO Phase Error
inherent correction
mechanism
High-Precision Complex
Quadrature Demodulator
(HP-CQDEMOD)
( Cosine Wave )
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6. Fundamental Architecture
Pair of Gilbert Mixers has the effect of LO signal Phase Error
Decrease of IRR
IRR: Image Rejection Ratio 6

7. Harvey-Type Quadrature Mixer
*J. Harvey et al, 14th Int’l
Conference on VLSI
Design, 2001
I/Q mixer-core has common-transconductor.
Phase errors can be compensated.
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8. Switching Characteristics
Current Switching Current Switching
w/o LO Phase Errors w/ LO Phase Errors
I/Q cross points keep difference of 90 degrees.
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9. Undesired Image Signal
Created by Amplitude Errors
Undesired effect caused by amplitude errors
in negative frequency region.
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10. Undesired Image Signal Create
by Amplitude Errors
Complex filter can suppress the image signal.
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11. Schematic of PPF
3 stages PPF
Inputs Outputs
*M. J. Gingell, Electrical Commun.,
Vol48, 1973
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12. Simulation Condition
It is designed by using 0.18um process offered from ROHM.
And it is simulated with “spectre” provided by VDEC.
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13. Simulation Result @ RF=3GHz
> 100dB Improved
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14. Future Tasks
• Research and design a wide-band polyphase filter or
a flexible complex band-pass filter.
• Design quadrature modulator working on low power
consumption under low voltage (1.5-1.8V).
• Run simulations when elements have some few
mismatches. (Using Monte Carlo Method)
• Fabricate chips experimentally and evaluate them.
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15. Publication
[1] T. Tsushima and T. Tsukahara, "A High-
Precision Complex Quadrature Modulator,“
The 2010 IEICE Society Conference, IEICE
[2] T. Tsushima and T. Tsukahara, "Design of a
High-Precision Complex Quadrature
Modulator," The Papers of Technical
Meeting on Electronic Circuits, IEE Japan
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