RF1238【PDF 1/2 页】SAW FILTER 318MHZ TO39-3

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RF1238

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)

318.0 MHz

SAW Filter

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 wireless 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 advanced 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.

Electrical Characteristics

TO39-3 Case

Characteristic

Sym

Notes

Minimum

Typical

Maximum

Units

Nominal Frequency at 25°C

Insertion Loss

Absolute Frequency

Tolerance from 318.0 MHz

f C

? f C

1, 2

318.0

1.7

±80

3.5

MHz

kHz

3 dB Bandwidth

BW 3

1, 2

500

700

800

kHz

Rejection

at f C - 21.4 MHz (Image)

at f C - 10.7 MHz (LO)

Ultimate

Temp. Characteristics

Operating Case Temp.

T C

-40

+85

°C

Turnover Temperature

Turnover Frequency

T O

f O

3, 4

f C +4

°C

kHz

Freq. Temp. Coefficient

FTC

0.032

ppm/°C 2

Frequency Aging

External Impedance Match Series Inductance

Shunt Capacitance (Tab Side, Non Tab Side)

IfAI

≤ 10

6.8 on Pin 1 Side, 4.7 on Pin 2 Side

ppm/yr

Lid Symbolization (in addition to Lot and/or Date Codes)

CAUTION: Electrostatic Sensitive Device. Observe precautions for handling.

Notes:

RFM RF1238

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.

The frequency f c is defined as the midpoint between the 3dB frequencies.

Where noted, specifications apply over the entire specified operating temperature range.

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 ].

Frequency aging is the change in fc 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 significantly in subsequent years.

The design, manufacturing process, and specifications of this device are subject to change without notice.

One or more of the following U.S. Patents apply: 4,54,488, 4,616,197, and others pending.

All equipment designs utilizing this product must be approved by the appropriate government agency prior to manufacture or sale.

www.RFM.com E-mail: info@rfm.com

?2008 by RF Monolithics, Inc.

Page 1 of 2

RF1238 - 3/21/08

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