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
ANTENNA DESIGN
For a
λ/4
dipole antenna and operating frequency,
f
(in MHz), the required antenna length,
L
(in cm),
may be calculated by using the formula
7132
L
=
.
f
For example, if the frequency is 315MHz, then the length of a
λ/4
antenna is 22.6cm. If the calculated
antenna length is too long for the application, then it may be reduced to
λ/8, λ/16,
etc. without
degrading the input return loss. However, the RF input matching circuit may need to be re-optimized.
Note that in general, the shorter the antenna, the worse the receiver sensitivity and the shorter the
detection distance. Usually, when designing a
λ/4
dipole antenna, it is better to use a single
conductive wire (diameter about 0.8 mm
to
1.6 mm) rather than a multiple core wire.
If the antenna is printed on the PCB, ensure there is neither any component nor ground plane
underneath the antenna on the backside of PCB. For an FR4 PCB (ε
r
= 4.7) and a strip-width of 30mil,
the length of the antenna,
L
(in cm), is calculated by
c
L
=
where “c” is the speed of light (3 x 1010 cm/s)
4
×
f
×
ε
r
When the PT4316 is operated in a noisy environment, it is recommended that an external SAW filter be
added between the input matching network and antenna.
PT4316 V1.6
- 13 -
August, 2007
PTC [ PRINCETON TECHNOLOGY CORP ]
