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PT4316 V1.6

- 7 -

August, 2007

Low Power 315/433 MHz OOK/ASK Superheterodyne

Receiver with SAW-based Oscillator

PT4316

IF LOW-PASS FILTER

The built-in IF filter is composed of three Sallen-Key low-pass filter stages and it has a -3dB bandwidth

of 3.1MHz. One stage Sallen-Key filter and frequency response of three cascaded filters as following

figure.

SAW OSCILLATOR

The SAW oscillator is configured as a Colpitts oscillator but consists of 3 cascaded amplifiers instead

of a single amplifier. Although the circuit configuration is quite similar to the conventional Colpitts

oscillator, this configuration is capable of generating a much higher value of negative resistance. The

one-port SAW resonator is connected between pin 15 (OSCIN) and pin 16 (OSCOUT).

The capacitor connected from pin 15 (OSCIN) to ground is used for adjusting the oscillation frequency.

In general, this capacitor is unnecessary if the frequency drift can be ignored. The figures at below, an

equivalent circuit of a SAW resonator and its component valuesare, are shown for reference.

*Optional

*C11

SAW Resonator

16

OSCIN

OSCOUT

15

C1

L1

C0

R1

SAW resonator equivalent circuit

Part Number

Center Frequency(MHz)

R1 (

Ω)

L1 (

µH)

C1 (pF)

C0 (pF)

MFSRA316.2

316.2

19

119.06

0.00213

2.4

MFSRA435.2

435.2

20

86.47

0.00155

2.0