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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.
L1
C1
R1
C0
OSCIN
15
16
OSCOUT
SAW resonator equivalent circuit
SAW Resonator
*C11
*Optional
Part Number
MFSRA316.2
MFSRA435.2
Center Frequency(MHz)
316.2
435.2
R1 (Ω)
19
20
L1 (µH)
119.06
86.47
C1 (pF)
0.00213
0.00155
C0 (pF)
2.4
2.0
PT4316 V1.6
-7-
August, 2007
PTC [ PRINCETON TECHNOLOGY CORP ]
