In previous sections, the FBAR filter has been presented. Due to the
commercial SAW resonators are used to TC0528A resonators
20mil height FR4 board with metal thickness 35μm SAW resonators is small, the filter is designed,
The MBVD model verified by experiment SAW resonator measurement result
the results from data
frequency shift between result
-tuning the MBVD model, the response of simulation and measurement similar. Table 4.
Fig. 4.19 The layout of single SAW
Experimental Validations Using Commercial SAW Resonators
In previous sections, the FBAR filter has been presented. Due to the
commercial SAW resonators are used to resonators [81]
20mil height FR4 board with metal thickness 35μm SAW resonators is small, the filter is designed,
The MBVD model can be found
experiment of single SAW resonator resonator experiment
measurement results of single SAW resonator from datasheet, and the solid frequency shift between result
tuning the MBVD model, the response of simulation and measurement .4 shows the value of MBVD model of datasheet and
The layout of single SAW
Experimental Validations Using Commercial SAW
In previous sections, the FBAR filter
has been presented. Due to the limited capability in manufacturing commercial SAW resonators are used to
and Murata
20mil height FR4 board with metal thickness 35μm SAW resonators is small, the filter is designed,
can be found
of single SAW resonator experiment using ADS momentum
of single SAW resonator sheet, and the solid
frequency shift between results from datasheet and measurement result tuning the MBVD model, the response of simulation and measurement
shows the value of MBVD model of datasheet and The layout of single SAW
Experimental Validations Using Commercial SAW
In previous sections, the FBAR filters design with simplified parallel RLC model limited capability in manufacturing
commercial SAW resonators are used to demonstrate the design procedure. The Tai Murata SMD 0402
20mil height FR4 board with metal thickness 35μm SAW resonators is small, the filter is designed, but
can be found from the datasheet, but the value should be of single SAW resonator.
using ADS momentum
of single SAW resonator are shown in
sheet, and the solid lines are measurement result from datasheet and measurement result tuning the MBVD model, the response of simulation and measurement
shows the value of MBVD model of datasheet and The layout of single SAW resonator
Experimental Validations Using Commercial SAW
design with simplified parallel RLC model limited capability in manufacturing
demonstrate the design procedure. The Tai 0402 lumped elements
20mil height FR4 board with metal thickness 35μm. Because of the but not a tunable one
from the datasheet, but the value should be . Figure 4.19
using ADS momentum [83]. The simulation result are shown in
lines are measurement result from datasheet and measurement result tuning the MBVD model, the response of simulation and measurement
shows the value of MBVD model of datasheet and experiment
Experimental Validations Using Commercial SAW
design with simplified parallel RLC model limited capability in manufacturing
demonstrate the design procedure. The Tai lumped elements [82]
Because of the kt
a tunable one.
from the datasheet, but the value should be 9 shows the layout of single . The simulation result
are shown in Fig. 4.20. The black lines lines are measurement result
from datasheet and measurement result tuning the MBVD model, the response of simulation and measurement
shows the value of MBVD model of datasheet and after fine experiment
Experimental Validations Using Commercial SAW
design with simplified parallel RLC model limited capability in manufacturing FBARs, the
demonstrate the design procedure. The Tai [82] are used kt2 of commercial
from the datasheet, but the value should be shows the layout of single . The simulation results and the . The black lines lines are measurement results. There are from datasheet and measurement results.
tuning the MBVD model, the response of simulation and measurement can be after fine-tuning.
design with simplified parallel RLC model FBARs, the demonstrate the design procedure. The Tai-Saw are used on of commercial
from the datasheet, but the value should be shows the layout of single and the
Fig. 4.20 The simulation results and the measurement results of single SAW resonator
Table 4.4 Circuit parameters of MBVD model of datasheet and after fine-tuning
MBVD Rr (Ω) Lr (μH) Cr (fF) C0 (pF)
Datasheet 10.7 15.3 1.66 2.75
After find-tune 10.7 13.3 1.905 1.83
Table 4.5 Circuit parameters of MBVD model and simplified parallel RLC model of single SAW resonator
MBVD model
Rr (Ω) Lr (μH) Cr (fF) C0 (pF) Ls (nH)
10.7 13.3 1.905 1.83 11
RLC model
Req (Ω) Leq (pH) Ceq (nF)
713.1 14.6596 1.7265
The new MBVD model is used to design the filter. The series inductor Ls is 11nH and used to make the transmission zero in 0.998GHz. Then the simplified parallel RLC model can be calculated by (4.31)-(4.33). The values of MBVD model and simplified parallel RLC model are shown in Table 4.5. Figure 4.21 shows the input impedance response of MBVD model and simplified parallel RLC model. The series inductor Ls can improve the selectivity of higher out-band.
Solid line : Measurement Dot line : Simulation Data
Sheet
|S11| |S21|
After fine-tune
Fig. 4.21 The input impedance response of MBVD model and simplified parallel RLC model.
(a) (b)
Fig. 4.22 The design circuit of SAW filter with simplified parallel RLC model and MBVD model, (a) Simplified parallel RLC model. (b) MBVD model
The SAW filter with 2nd order Chebyshev response and FBW = 0.05% is designed.
From (4.37) and (4.38), the required values of filter are calculated. Figure 4.22 shows the design circuit of SAW filter with simplified parallel RLC model and MBVD model.
The SMD capacitors and inductors are used to design the coupling coefficient and external quality factor. The simulation results are shown in Fig. 4.23. The in-band responses have good match. The out-band responses are different because of the transmission zero.
Figure 4.22 shows the ideal circuit of filter, but the layout in experiment will induce additional effect. Figure 4.24 shows the layout in real experiment. The value of
Port 1 C Port 2
m
Ls SAW
Ls SAW
Cq C
q
Fig.
capacitors
shows the circuit parameters of ideal simplified RLC model, ideal BVD model layout experiment. The circuit photos are shown in
simulation results of SAW filter are shown in simulation results are
modes near 0.9965GHz, 1.0015GHz, and 1.004GHz 4.26, those spurious modes become more obvious
Fig. 4.23 The simulation result of SAW filter
capacitors and inductors are changed because of considering the layout effect.
shows the circuit parameters of ideal simplified RLC model, ideal BVD model layout experiment. The circuit photos are shown in
simulation results of SAW filter are shown in simulation results are
modes near 0.9965GHz, 1.0015GHz, and 1.004GHz , those spurious modes become more obvious
simulation result of SAW filter
Fig. 4.24 The layout of real experiment of SAW filter.
and inductors are changed because of considering the layout effect.
shows the circuit parameters of ideal simplified RLC model, ideal BVD model layout experiment. The circuit photos are shown in
simulation results of SAW filter are shown in simulation results are in good agreement
modes near 0.9965GHz, 1.0015GHz, and 1.004GHz , those spurious modes become more obvious
simulation result of SAW filter MBVD model
The layout of real experiment of SAW filter.
and inductors are changed because of considering the layout effect.
shows the circuit parameters of ideal simplified RLC model, ideal BVD model layout experiment. The circuit photos are shown in
simulation results of SAW filter are shown in in good agreement
modes near 0.9965GHz, 1.0015GHz, and 1.004GHz , those spurious modes become more obvious
simulation result of SAW filter with simplified parallel RLC model and MBVD model
The layout of real experiment of SAW filter.
and inductors are changed because of considering the layout effect.
shows the circuit parameters of ideal simplified RLC model, ideal BVD model layout experiment. The circuit photos are shown in
simulation results of SAW filter are shown in in good agreement. From modes near 0.9965GHz, 1.0015GHz, and 1.004GHz
, those spurious modes become more obvious
with simplified parallel RLC model and MBVD model
The layout of real experiment of SAW filter.
and inductors are changed because of considering the layout effect.
shows the circuit parameters of ideal simplified RLC model, ideal BVD model layout experiment. The circuit photos are shown in Fig. 4
simulation results of SAW filter are shown in Fig. 4.26 From Fig. 4.20
modes near 0.9965GHz, 1.0015GHz, and 1.004GHz on single SAW resonator
, those spurious modes become more obvious and may come from SAW resonator with simplified parallel RLC model and
The layout of real experiment of SAW filter.
and inductors are changed because of considering the layout effect.
shows the circuit parameters of ideal simplified RLC model, ideal BVD model
4.25. The measurement and 26. The measurement and 20, there are some spurious on single SAW resonator
and may come from SAW resonator with simplified parallel RLC model and
and inductors are changed because of considering the layout effect. Table shows the circuit parameters of ideal simplified RLC model, ideal BVD model, and real
. The measurement and . The measurement and , there are some spurious on single SAW resonator. In and may come from SAW resonator with simplified parallel RLC model and
Table 4.6
and may come from SAW resonator.
Table
Ideal circuit of parallel RLC model
Fig.
The spurious mode near 0.999GHz may be induced from the connection of SAW resonators and lump
Table 4.6 Circuit parameters of ideal circuit and real layout experiment of SAW
Ideal circuit of parallel RLC model Ideal circuit of MBVD model
Real layout experiment
Fig. 4.25 The circuit photos of single SAW resonator and
Fig.
The spurious mode near 0.999GHz may be induced from the connection of SAW resonators and lump
Circuit parameters of ideal circuit and real layout experiment of SAW
Ideal circuit of parallel RLC model Ideal circuit of MBVD model
Real layout experiment
(a)
The circuit photos of single SAW resonator and
Fig. 4.26 The measurement and simulation result
The spurious mode near 0.999GHz may be induced from the connection of SAW resonators and lump elements.
Circuit parameters of ideal circuit and real layout experiment of SAW
Ideal circuit of parallel RLC model Ideal circuit of MBVD model
Real layout experiment
The circuit photos of single SAW resonator and resonator
The measurement and simulation result
The spurious mode near 0.999GHz may be induced from the connection of SAW elements.
Circuit parameters of ideal circuit and real layout experiment of SAW filter
Cq (pF) Ideal circuit of parallel RLC model 2.2
5 36
The circuit photos of single SAW resonator and resonator. (b) SAW filter
The measurement and simulation result
The spurious mode near 0.999GHz may be induced from the connection of SAW Circuit parameters of ideal circuit and real layout experiment of SAW
(pF) C
The circuit photos of single SAW resonator and SAW filter.
(b) SAW filter.
The measurement and simulation results
The spurious mode near 0.999GHz may be induced from the connection of SAW Circuit parameters of ideal circuit and real layout experiment of SAW
Cm (pF)
s of SAW filter
The spurious mode near 0.999GHz may be induced from the connection of SAW Circuit parameters of ideal circuit and real layout experiment of SAW
Ls(nH) Circuit parameters of ideal circuit and real layout experiment of SAW
ingle SAW
The spurious mode near 0.999GHz may be induced from the connection of SAW
Chapter 5
Reconfigurable Filters Using Tunable Film Bulk Acoustic Resonators
In this chapter, reconfigurable filters using tunable film bulk acoustic resonators (TFBARs) [64] have been presented. The TFBAR filters are designed by coupled resonator theory of filter design. The parallel RLC model can be used to simplify the basic resonator topology of TFBAR in series with inductor; while the coupling coefficient can be realized by capacitors. The external quality factor can be designed by lumped elements. The basic theories of TFBARs will be introduced first. Then, the design of TFBARs and reconfigurable filters will be shown. Finally, the reconfigurable filters using tunable FBARs will be applied to LTE bands.
5.1. Basic Theories of Tunable FBARs
Figure 5.1 shows the 3-D view of the complete structure and the cross-sectional view of basic structure of tunable FBARs (TFBARs) [64]. In real fabrication, the complete structure has been considered, while only the basic structure is taken into account in simulation and theory derivation. In Fig. 5.1 (b), the basic TFBAR structure includes a top electrode, a semiconducting piezoelectric layer with controlled doping concentration, a general piezoelectric layer without doping and a bottom electrode. The
(a)
(b)
Fig. 5.1 Structure of a single TFBAR resonator. (a) 3-D view of complete structure.
(b) Cross section of basic structure.
thickness of piezoelectric layer with doping, piezoelectric layer without doping, and electrode is dN, dp, and dt, respectively.
For filter design, the electrical characteristic of piezoelectric is necessary and useful.
When the electrical voltage V is applied on top electrode, the displacement current I will be induced. The electrical input impedance can be derived by Zin = V/I. The basic theory of piezoelectric layers has been presented in Section 4.1 and (4.18) can be adopted to solve for the stress T from the given electric flux density D. For the basic TFBAR structure shown in Fig. 5.1 (b), the boundary conditions are
(1) T and u are continuous at z = d1, z = d2, and z = d3 (2) T = 0 at z = 0 and z = d4
Top Electrode
Membrane
Bottom Electrode Piezoelectric Materail
Silicon Substrate
Air Gap Depletion Layer
The derivation to the stress T in each layer and the resultant input impedance is given in the Appendix. In the present case, there is additional layer for semiconducting piezoelectric layer with doping. Hence, additional parameters will be introduced, they are
where subscript N denotes the semiconducting piezoelectric layer with doping. And the impedance of acoustic wave Za and its phase velocity va are
N frequency fa by Zin=∞. The effective electromechanical coupling coefficient of TFBAR kt.eff2 is affected by ratio of thickness of piezoelectric layer and electrode (dt / HT ; HT=dp+dN). The kt.eff2
can be estimated by (4.25) [69].
For general FBAR filter design, the modified Butterworth-Van Dyke (MBVD) model of FBARs is commonly used, shown in Fig. 4.2 (b) [71]. The MBVD model can also be used in TFBARs and be obtained by [72]
r r r r
r r r
r Q
L R f
R
Q ω L 2π
=
⇒
= (5.7)
r a
r a
r r a
a R
Q L R f
R R
Q L ⇒ = −
+
=
π
ω 2
0 0
(5.8)
Here, the C0 is the parallel capacitance between two electrodes. Two kinds of piezoelectric material are sandwiched by two electrodes. The Cr and Lr can be calculated by the resonance frequency fr and anti-resonance frequency fa. The Rr and R0
are determined from the quality factor Qr and Qa of TFBARs, respectively.
In the dissertation, the anti-resonance frequency (fa) is the main response for designing the present filters by coupling capacitors. Similarly to that in Chapter 4, the building topology of TFBAR in series with Ls is defined as a resonator of filter. The parallel RLC model can be used to simplify its response near the anti-resonance, similar as Fig. 4.3. The relationship between the TFBAR in series with Ls and parallel RLC model is readily available from (4.31)-(4.33).