Notes on Sanyo SAW Filters
There are two types of SAW filters, which differ in the piezoelectric substrate material, as follows:
Lithium tantalate (LiTaO3) SAW filter
TSF11
I
I I
I ... Japan
TSF12
I
I I
I ... US
Although lithium tantalate SAW filters have the low temperature coefficient of –18ppm/°C, they suffer from a large
insertion loss. However, it is possible, at the cost of increasing the number of external components required, to
minimize this insertion loss by using a matching circuit consisting of coils and other components at the SAW filter
output. At the same time as minimizing insertion loss, this technique also allows the frequency characteristics, level,
and other aspects to be varied, and thus provides increased circuit design flexibility. Also, since the SAW filter
reflected wave level is minimal, the circuit can be designed with a small in-band ripple level.
Lithium niobate (LiNbO3) SAW filter
TSF52
I
I I
I ... US
TSF53
I
I I
I ... PAL
Although lithium niobate SAW filters have the high temperature coefficient of –72ppm/°C, they feature an insertion
loss about 10dB lower than that of lithium tantalate SAW filters. Accordingly, there is no need for a matching circuit
at the SAW filter output. Although the in-band ripple is somewhat larger than with lithium tantalate SAW filters,
since they have a low impedance and a small field slew, they are relatively immune to influences from peripheral
circuit components and the geometry of the printed circuit board pattern. This allows stable out-of-band trap
characteristics to be acquired. Due to the above considerations, lithium tantalate SAW filters are used in applications
for the US and Japan that have a high IF frequency, and lithium niobate SAW filters are used in PAL and US
applications that have a low IF frequency.
Notes on SAW Filter Matching
In SAW filter input circuit matching, rather than matching the IF frequency, flatter video band characteristics can be
acquired by designing the tuning point to be in the vicinity of the audio carrier rather than near the chrominance
carrier. The situation shown in figure on the right makes it easier to acquire flat band characteristics than that in figure
on the left.
With the Tuning Set to the IF frequency
With the Tuning Set to the Vicinity of S and C
No.7779-20/21
LA7567EV
ILA06708
The high band is reduced
Frequency
SAW filter
characteristics
Frequency
The high band is extended
Coil Specifications
Toko Co., Ltd.
2-1-17 Higashi-yukigaya, Ohta-ku, Tokyo, Japan
TEL: +81-3-3727-1167
JAPAN f = 58.75MHz
US f = 45.75MHz
PAL f = 38.9MHz
VCO coil
Test production no. V291XCS-3220Z
Test production no. 291XCS-3188Z
Test production no. 292GCS-7538Z
Toko Co., Ltd.
SAW filter
Picture
(SPLIT)
TSF1137U
TSF1241
TSF5315
Sound
SAW filter
TSF5220
TSF5321
(INTER)
TSF5221
TSF5344
S
t=5t
0.12
C=24pF
ILA06709
ILA06710
S
t=6t
0.12
C=24pF
ILA06711
S
t=7t
0.12
C=24pF