Tel: 886-2-66296288
Fax: 886-2-29174598
URL: http://www.princeton.com.tw
Low Power 315/433 MHz OOK/ASK Superheterodyne
Receiver with SAW-based Oscillator
PT4316
FUNCTION DESCRIPTION
The PT4316 CMOS superheterodyne receiver provides the functionality of a complete receive chain
from an antenna input to digital data output. Depending upon signal power and component selection,
data rates as high as 50 Kb/s may be achieved.
LOW NOISE AMPLIFIER (LNA)
The LNA is an on-chip cascode amplifier with a power gain of 16dB and a noise figure of 3dB. The gain
is determined by external matching networks situated ahead of the LNA and between the LNA output
and the mixer input.
An example of the input matching network and the input impedance of PT4316 for 315/434MHz bands
are shown in the following figure. The component values given in the table following the application
circuit are nominal values only. For a particular PCB layout, the user may be required to make
component adjustments in order to achieve highest sensitivity.
C3
C2
3
RFIN
C4
Frequency
(MHz)
315
433.92
LNA Input Impedance (Pin 3)
Normalized to 50Ω
4.18—j251.63
3.60—j180.20
The LNA output of PT4316 internally connects to the mixer stage so that its output impedance cannot
be measured directly. The LNA output requires a DC supply through a choke inductor. For obtaining
better LNA gain, a capacitor is recommended to be added in parallel with this inductor to implement a
resonant tank at the desired frequency as shown in the following figure. Note that the LNA might
self-oscillate and degrade the receiver sensitivity, particularly if a large inductor value is chosen. An
alternate matching method is to replace the parallel capacitor with a 330 to 1KΩ resistor, which would
reduce the resonant tank Q (quality factor) and avoid the self-oscillation.
VDD
R1
L2
C5
5
LNAOUT
C8
PT4316 V1.6
-5-
August, 2007
PTC [ PRINCETON TECHNOLOGY CORP ]
