Module Mounting considerations
1.
2.
3.
4.
5.
The module may be mounted vertically or bent horizontal to the motherboard.
No conductive items should be placed within 4 mm of the modules’ component side to prevent
detuning.
Observe RF layout practice between the module and it’s antenna i.e. < 10 mm unscreened track,
use 50Ω microstrip or coax for >10mm
It is desirable, but not essential, to earth plane all unused area around the module.
Mount as far as possible from high frequency interference sources, Microprocessors with
external busses are totally incompatible with sensitive radio receivers and must be keep at least
1 metre from the receive antenna. Single chip micros are not a problem.
In some applications it is advantageous to remote the receiver and it’s antenna away from the
main equipment. This avoids any interference problems and allows flexibility in the sighting of
the receive
antenna for optimum RF performance.
6.
Using the DETECT output
Pin 3 of the module may be used in several ways:-
1.
2.
3.
Pulled up to pin 5 (Vcc) with a 47 kΩ resistor unmutes the AF and DATA outputs for normal
operation.
Pulled down to 0 Volts with a 47 kΩ mutes the AF and DATA Outputs (both go to 0V).
To drive the base of a PNP transistor (see fig 2) to derive a logic compatible carrier detect. The
data detect output on pin 3 may be used for duty cycle power saving control in portable
equipment where battery life is a problem. By pulsing the receiver on/off the average supply
current may often be reduced by a factor of 20 or more depending upon the system
requirements the data detect output is
valid 1.5 ms (2.5 ms worst case) after application
of the supply and is used to inhibit the power saving while data decoding is done.
Internal data slicer
A CMOS compatible data output is available on pin 7, this output is normally used to drive a digital
decoder IC or a microprocessor which is performing the data decoding. The data slicer in the receive
module is designed to accept data with a wide range of pulse widths and mark: space ratio’s, see
specification table for limiting values. The data slicer has a 10 ms transient response time this is the
settling time of the adaptive comparator, i.e. the first 10 ms of signal may be corrupt at the data output.
System coding
The transmit and receive modules have no internal digital coding/decoding thus allowing the flexibility
to send many types of data. Encoder and decoder IC’s are required to give the system a high degree of
protection from false triggers due to noise/interference/neighbouring systems and often for security
reasons. There are wide range of suitable encoder/decoder IC’s which may be used with the modules,
including :-
MM57C200, MM57410,National Semiconductor
UM3750, UMC
HT12 series, Holtek
MC145026 series, Motorola
AS2787, Austria Mikro Systeme International GmbH
Additionally IR. remote control, DTMF, Selcall and modem IC’s can be easily interfaced to the modules.
Radiometrix Ltd, SILRX-UHF Data Sheet
page 8
RADIOMETRIX [ RADIOMETRIX LTD ]
