RF Monolithics, Inc.
Phone: (972) 233-2903
Fax: (972) 387-8148
E-mail: info@rfm.com
Page 1 of 2
RFM Europe
Phone: 44 1963 251383
Fax: 44 1963 251510
http://www.rfm.com
1999 by RF Monolithics, Inc. The stylized RFM logo are registered trademarks of RF Monolithics, Inc.
RF1238-102401
Electrical Characteristics
Characteristic
Sym
Notes
Minimum
Typical
Maximum
Units
Nominal Frequency at 25C
Absolute Frequency
f
C
1, 2
318.0
MHz
Tolerance from 318.0 MHz
f
C
80
kHz
Insertion Loss
IL
1
1.7
3.5
dB
3 dB Bandwidth
BW
3
1, 2
500
700
800
kHz
Rejection
at f
C
- 21.4 MHz (Image)
1
40
50
dB
at f
C
- 10.7 MHz (LO)
15
40
Ultimate
80
Temp. Characteristics
Operating Case Temp.
T
C
3, 4
-40
+85
C
Turnover Temperature
T
O
30
45
60
C
Turnover Frequency
f
O
f
C
+4
kHz
Freq. Temp. Coefficient
FTC
0.032
ppm/C
2
Frequency Aging
IfAI
5
10
ppm/yr
External Impedance Match
Series Inductance
L
1
86
nH
Shunt Capacitance (Tab Side, Non Tab Side)
C
6.8 on Pin 1 Side, 4.7 on Pin 2 Side
pF
Lid Symbolization (in addition to Lot and/or Date Codes)
RFM RF1238
TO39-3 Case
Ideal Front-End Filter for 318.0 MHz Wireless Receivers
Low-Loss, Coupled-Resonator Quartz Design
Simple External Impedance Matching
Rugged TO39 Hermetic Package
Complies with Directive 2002/95/EC (RoHS)
The RF1238 is a low-loss, compact, and economical surface-acoustic-wave (SAW) filter designed to provide
front-end selectivity in 318.0 MHz receivers. Receiver designs using this filter include superhet with
10.7 MHz or 500 kHz IF, direct conversion and superregen. Typical applications of these receivers are wire-
less remote-control and security devices operating in the USA under FCC Part 15, in Canada under DoC
RSS-210, and in Australia.
This coupled-resonator filter (CRF) uses selective null placement to provide suppression, typically greater
than 40 dB, of the LO and image spurious responses of superhet receivers with 10.7 MHz IF. RFM's ad-
vanced SAW design and fabrication technology is utilized to achieve high performance and very low loss with
simple external impedance matching (not included). Quartz construction provides excellent frequency stability
over a wide temperature range.
318.0 MHz
SAW Filter
RF1238
CAUTION: Electrostatic Sensitive Device. Observe precautions for handling.
Notes:
1. Unless noted otherwise, all measurements are made with the filter installed in the specified test fixture which is connected to a 50
test system with
VSWR
1.2:1. The test fixture L and C are adjusted for minimum insertion loss at the filter center frequency, f
c
. Note that insertion loss, bandwidth,
and passband shape are dependent on the impedance matching component values and quality.
2. The frequency f
c
is defined as the midpoint between the 3dB frequencies.
3. Where noted, specifications apply over the entire specified operating temperature range.
4. The turnover temperature, T
O
, is the temperature of maximum (or turnover) frequency, f
o
. The nominal frequency at any case temperature, T
c
, may
be calculated from: f = f
o
[1 - FTC (T
o
- T
c
)
2
].
5. Frequency aging is the change in fc with time and is specified at +65C or less. Aging may exceed the specification for prolonged temperatures
above +65C. Typically, aging is greatest the first year after manufacture, decreasing significantly in subsequent years.
6. The design, manufacturing process, and specifications of this device are subject to change without notice.
7. One or more of the following U.S. Patents apply: 4,54,488, 4,616,197, and others pending.
8. All equipment designs utilizing this product must be approved by the appropriate government agency prior to manufacture or sale.
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