Himanshu Khatri, Lawrence E. Larson

1
Himanshu Khatri, Lawrence E. Larson Donald
LieDepartment of Electrical and Computer
Engineering Jacobs School of Engineering,
University of California San Diego, CA 92093
Monolithic Filter for Receiver Interference
Suppression
Motivation
Filter Topology
Simulations
3-pole band pass filter
Inverter transformation
Variation with Q

• Factors affecting the electrical characteristics
  of bond wires are
• Bond wire quality factor
• Coefficient of mutual coupling
• Self inductance of the bond wire

Merging negative capacitances
Adding bond wire inductances

• TX leakage desensitizes the receiver and cross
  modulates with the jammer producing in-band
  interference
• This requires high linearity (power hungry) LNA
  and expensive off-chip SAW filter
• Our research aims at a practical approach for
  on-chip filtering to eventually replace SAW
  filters in some applications

Final Schematic
Variation with L
Variation with k
Requires only on-chip MIM capacitors. No spiral
inductors!
BPF Specifications (WCDMA)
Bond Wire Issues Mutual Coupling

• Rx band 2.11G 2.17G
• Tx band 1.92G 1.98G
• Rx-Tx Selectivity 21dB
• Noise Figure 3dB
• Group Delay Variation 20 nsec
• IIP3 25 dBm

• Coupling between adjacent bond wires within the
  section results in frequency translation

Layout

• Coupling across the sections leads to pole
  splitting in the pass band

Filter Transfer Function
Chebyshev Eq. Low Pass Filter
Filter Specifications
Bandpass Specification ?center 2.14G ?pass
2.10G Amax -0.5dB ?stop 1.98G Amin -40dB

• Coupling with I/O increases insertion loss

The chip has been sent for fabrication on Jazz
SiGe120 process and is expected to be back in
June 05 for testing.
Chebyshev LP response Opass 1 Amax
-0.5dB Ostop 4.2 Amin -40dB n 3
Conclusion
Solution Ground Shielding Avoid coupling with
I/O and across the sections
A passive filter with low noise can be
constructed using only on-chip MIM capacitors and
bond wire inductors. The simulations show that
such a filter is capable of providing the desired
selectivity with some insertion loss. With high
density capacitors and high quality bond wires
this on-chip filter has the potential to replace
SAW filter.
Pole Frequency Q 2.14 GHz
43.0965 2.14 GHz 43.0965 2.10 GHz
92.149 2.10 GHz 92.149 2.178
GHz 92.149 2.178 GHz 92.149
Pole Frequency Q 0.6265
0.5 1.0689 1.7062 1.0689
1.7062