®
RO2118A
318.0 MHz
SAW
Resonator
•
•
•
•
•
Ideal for 318 MHz Transmitters
Very Low Series Resistance
Quartz Stability
Surface-Mount, Ceramic Case with 21 mm
2
Footprint
Complies with Directive 2002/95/EC (RoHS)
The RO2118A is a true one-port, surface-acoustic-wave (SAW) resonator in a surface-mount, ceramic case.
It provides reliable, fundamental-mode, quartz frequency stabilization of fixed-frequency transmitters operat-
ing at 318 MHz. This SAW is designed for AM transmitters remote control and wireless security applications
operating in the USA under FCC Part 15, in Canada under DoC RSS-210, and in Italy.
Absolute Maximum Ratings
Rating
CW RF Power Dissipation
DC Voltage Between Terminals
Case Temperature
Soldering Temperature (10 seconds / 5 cycles max.)
Value
+0
±30
-40 to +85
260
Units
dBm
VDC
°C
°C
SM-2 Case
Electrical Characteristics
Frequency (+25 °C)
Insertion Loss
Quality Factor
Temperature Stability
Unloaded Q
50
Ω
Loaded Q
Turnover Temperature
Turnover Frequency
Frequency Temperature Coefficient
Frequency Aging
RF Equivalent RLC Model
Absolute Value during the First Year
Motional Resistance
Motional Inductance
Motional Capacitance
Transducer Static Capacitance
Test Fixture Shunt Inductance
Lid Symbolization
DC Insulation Resistance between Any Two Terminals
R
M
L
M
C
M
C
O
L
TEST
5, 6, 9
2, 7
108
2.9
5, 6, 7, 9
Characteristic
Nominal Frequency
Tolerance from 318.000 MHz
Sym
f
C
∆f
C
IL
Q
U
Q
L
T
O
f
O
FTC
|f
A
|
1, 6
5
1.0
8
72.2067
3.46904
3.2
80
3.5
19
6, 7, 8
Notes
2, 3, 4, 5
2, 5, 6
5, 6, 7
10
Minimum
317.900
Typical
Maximum
318.100
±100
0.7
16,900
1,300
25
f
C
0.032
10
ppm/°C
2
ppm/yr
MΩ
Ω
µH
fF
pF
nH
40
°C
1.5
Units
MHz
kHz
dB
CAUTION: Electrostatic Sensitive Device. Observe precautions for handling.
Notes:
1.
Frequency aging is the change in f
C
with time and is specified at +65°C or less.
Aging may exceed the specification for prolonged temperatures above +65°C.
Typically, aging is greatest the first year after manufacture, decreasing in subse-
quent years.
The center frequency, f
C
, is measured at the minimum insertion loss point,
IL
MIN
, with the resonator in the 50
Ω
test system (VSWR
≤
1.2:1). The shunt
inductance, L
TEST
, is tuned for parallel resonance with C
O
at f
C
. Typically, f
OS-
CILLATOR
or f
TRANSMITTER
is approximately equal to the resonator f
C
.
One or more of the following United States patents apply: 4,454,488 and
4,616,197.
Typically, equipment utilizing this device requires emissions testing and govern-
ment approval, which is the responsibility of the equipment manufacturer.
Unless noted otherwise, case temperature T
C
= +25°C±2°C.
The design, manufacturing process, and specifications of this device are subject
to change without notice.
Derived mathematically from one or more of the following directly measured
parameters: f
C
, IL, 3 dB bandwidth, f
C
versus T
C
, and C
O
.
8.
Turnover temperature, T
O
, is the temperature of maximum (or turnover) fre-
quency, f
O
. The nominal frequency at any case temperature, T
C
, may be calcu-
lated from: f = f
O
[1 - FTC (T
O
-T
C
)
2
]. Typically
oscillator
T
O
is approximately
equal to the specified
resonator
T
O
.
This equivalent RLC model approximates resonator performance near the reso-
nant frequency and is provided for reference only. The capacitance C
O
is the
static (nonmotional) capacitance between the two terminals measured at low
frequency (10 MHz) with a capacitance meter. The measurement includes para-
sitic capacitance with "NC” pads unconnected. Case parasitic capacitance is
approximately 0.05 pF. Transducer parallel capacitance can by calculated as:
C
P
≈
C
O
- 0.05 pF.
2.
9.
3.
4.
5.
6.
7.
RF Monolithics, Inc.
Phone: (972) 233-2903
Fax: (972) 387-8148
RFM Europe
Phone: 44 1963 251383
Fax: 44 1963 251510
©1999 by RF Monolithics, Inc. The stylized RFM logo are registered trademarks of RF Monolithics, Inc.
E-mail: info@rfm.com
http://www.rfm.com
RO2118A-061901
Page 1 of 2
318.0 MHz
Electrical Connections
The SAW resonator is bidirectional and may be in-
stalled with either orientation. The two terminals
are interchangeable and unnumbered. The callout
NC indicates no internal connection. The NC pads
assist with mechanical positioning and stability.
External grounding of the NC pads is recommend-
ed to help reduce parasitic capacitance in the cir-
cuit.
SAW Resonator
Terminal
Equivalent LC Mode
l
0.05 pF*
NC
NC
Co = Cp + 0.05 pF
Cp
*Case Parasitics
Terminal
Rm
Lm
Cm
Temperature Characteristics
The curve shown on the right
f
C
= f
O
, T
C
= T
O
0
(f-fo ) / fo (ppm)
Typical Test Circuit
The test circuit inductor, L
TEST
, is tuned to resonate with the static capaci-
tance, C
O
, at F
C
.
accounts for resonator contri-
bution only and does not in-
clude LC component tempera-
ture contributions
.
0
-50
-100
-150
-200
0 +20 +40 +60 +80
-50
-100
-150
-200
-80 -60 -40 -20
ELECTRICAL TEST
From 50
Ω
Network Analyzer
To 50
Ω
Network Analyzer
Typical Circuit Board
Land Pattern
∆
T = T
C
- T
O
( °C )
The circuit board land pattern shown below is one possible design. The op-
timum land pattern is dependent on the circuit board assembly process
which varies by manufacturer. The distance between adjacent land edges
should be at a maximum to minimize parasitic capacitance. Trace lengths
from terminal lands to other components should be short and wide to mini-
mize parasitic series inductances.
(4 Places)
Typical Dimension:
0.010 to 0.047 inch
(0.25 to 1.20 mm)
Case Design
The case material is black alumina with contrasting symbolization. All pads
are nominally centered with respect to the base and consist of 40 to
70 microinches electroless gold on 60-350 micorinches electroless nickel.
Typical Application Circuits
Typical Low-Power Transmitter Application
+9VDC
Modulation
Input
200k
Ω
C1
L1
47
(Antenna)
ROXXXXA
Bottom View
470
C2
RF Bypass
Millimeters
Dimensions
Min
A
B
C
D
Output
Inches
Min
0.226
0.147
0.075
0.037
0.033
0.046
0.037
0.017
0.017
0.200
0.015
0.120
Max
0.236
0.157
0.085
0.043
0.047
0.060
0.043
0.023
0.023
0.210
0.025
0.130
Max
5.99
3.99
2.16
1.10
1.20
1.53
1.10
0.59
0.59
5.33
0.64
3.30
5.74
3.73
1.91
0.94
0.83
1.16
0.94
0.43
0.43
5.08
0.38
3.05
Typical Local Oscillator Application
E
F
G
H
K
M
N
+VDC
C1
L1
+VDC
ROXXXXA
Bottom View
C2
RF Bypass
P
RF Monolithics, Inc.
Phone: (972) 233-2903
Fax: (972) 387-8148
RFM Europe
Phone: 44 1963 251383
Fax: 44 1963 251510
©1999 by RF Monolithics, Inc. The stylized RFM logo are registered trademarks of RF Monolithics, Inc.
E-mail: info@rfm.com
http://www.rfm.com
RO2118A-061901
Page 2 of 2
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