Hartcran House, 231 Kenton Lane, Harrow, Middlesex, HA3 8RP, England
Tel: +44 (0) 20 8909 9595, Fax: +44 (0) 20 8909 2233, www.radiometrix.com
LMT2 / LMR2
Issue 1, 21 January 2013
UHF Narrow Band FM Low Cost multi channel
The LMT2 transmitter and LMR2 receiver
modules offer a multi channel, low power, and
reliable data link. This makes the LMT2/LMR2
pair ideally suited to those low power
applications where existing wideband modules
have insufficient range, or where low cost multichannel
operation
is
needed
without
compromising on RF specification or regulatory
requirement.
Figure 1: LMT2 transmitter and LMR2 receiver
Features
Conforms to EN 300 220-3 and EN 301 489-3
High performance double superhet. PLL synthesizer with TCXO
quasi-dc (peak sampling) data recovery circuit (for enhanced performance on unbalanced
datastreams)
SAW front-end filter
Data rates up to 5 kbps for standard module
Usable range over 1km
Fully screened. Low profile
Feature-rich interface (RSSI, analogue and digital baseband)
Re-programmable via RS232 interface
Low power requirements
Applications
Handheld terminals
EPOS equipment, barcode scanners
Data loggers
Industrial telemetry and telecommand
In-building environmental monitoring and control
High-end security and fire alarms
DGPS systems
Vehicle data up/download
Heavy vehicle/machinery controls
Technical Summary
Operating frequency: 433.875-434.650MHz (EU band)
458.525 - 459.1MHz (UK band)
Other custom UHF bands
32 channels
Transmit power: +10dBm (10mW) / +20dBm (100mW)
Supply range: 3.1 – 15V (TX @ 10mW and RX), 4.1 – 15V (TX @ 100mW)
Current consumption: 34mA @ 10mW, 90mA @ 100mW (transmit) and 20mA (receive)
Data bit rate: 5kbps max. (standard module)
Receiver sensitivity: -118dBm (for 12 dB SINAD)
Serial configuration by inverted RS232 at 3V CMOS level
Evaluation platforms: NBEK + LM Series carrier
Radiometrix Ltd
LMT2/LMR2 Data Sheet
page 1
Figure 2: LMT2 block diagram
Radiometrix Ltd
LMT2/LMR2 Data Sheet
page 2
Figure 3: LMT2 footpint (top view)
Pin description – LMT2
Pin
1a
Name
Vcc
2a
3a
4a
5a
0V
TXE
TXD
No pin
1b
P0/PGM
2b
3b
4b
5b
P1
P2
P3
No pin
Function
3.1 – 15V power supply (@ 10mW)
4.1 – 15V power supply (@ 100mW)
Ground
Transmit Enable (active low)
DC coupled input for 3V CMOS logic. Rin=47kΩ
Not present in LMT2
Parallel Channel select LSB
1
Serial frequency programming / configuration
Parallel Channel select
Parallel Channel select
Parallel Channel select MSB
Not present in LMT2
Notes:
1. Serial programming is by an inverted, CMOS logic level, 2400 baud RS232 datastream applied to
the P0 pin.
2. Channel select inputs have pullups (50kΩ) to 3v internal rail. Do not exceed 3V logic levels on this
port.
3. Channel select inputs are active low
4. TXE has a 100kΩ pullup to Vcc
5. All pins are on an 0.1" grid
6. The pins 5a/b are not present, but are included in footprint for compatibility with other units in this
family
7. In the 'off' state a PIN switch open circuits the RF output pin. There are no 'off' state spuri.
8. 10mW unit will operate (with marginally reduced specifications and lower (6-8mW) output power)
from a 3.0V rail. This must be well regulated and without noise or ripple, as in this state the unit's
internal regulator no longer operates, and provides no supply rejection.
9. 100mW versions should not be run continuously from supply voltages > 9v
Radiometrix Ltd
LMT2/LMR2 Data Sheet
page 3
Figure 4: LMR2 block diagram
Radiometrix Ltd
LMT2/LMR2 Data Sheet
page 4
Figure 5: LMR2 footpint (top view)
Pin description – LMR2
Pin
1a
2a
3a
4a
5a
Name
Vcc
0V
RXE
RXD
AF out
Function
3.1 – 15V power supply
Ground
Receiver Enable (active high)
Data out (open collector, no pullup)
700mV p-p audio. DC coupled, approx 0.8v bias.`
1b
P0/PGM
2b
3b
4b
5b
P1
P2
P3
RSSI
Parallel Channel select LSB
1
Serial frequency programming / configuration
Parallel Channel select
Parallel Channel select
Parallel Channel select MSB
DC level between 0.5v and 2.2v. 60dB dynamic range
NOTES:
1. Serial programming is by an inverted, cmos logic level, 2400 baud RS232 datastream applied to the
P0 pin.
2. Channel select inputs have pullups (50kΩ) to 3v internal rail. Do not exceed 3v logic levels on this
port.
3. Channel select inputs are active low
4. All pins are on an 0.1" grid
5. Data recovery circuit used for RXD is not a simple 'average and compare' type. It is a peak sampling
quasi-DC coupled design, allowing a greater than usual flexibility in data format.
6. Unit will operate (with marginally reduced specifications) from a 3.0v rail. This must be well regulated
and without noise or ripple, as in this state the unit's internal regulator no longer operates, and
provides no supply rejection.
Radiometrix Ltd
LMT2/LMR2 Data Sheet
page 5
Serial interface commands
2400 baud RS232. 8 bit data, no parity, 1 start bit, 1 or 2 stop bits.
Serial data is sent to the unit on one of the parallel channel select pins (P0). It is very important that the unit
does not 'decode' switch bounce in ordinary operation as a command string, or spurious re-writing of the
e2prom will result. For this reason the user must send the 16 character string ENABLESERIALMODE
(followed by a carriage return) to activate the serial command mode before sending any of the command
strings listed below. Command mode is disabled on power down, or on reception of a # character. To
successfully program the unit, it must be enabled ('RXE high (rx) or TXE low (tx)).
GOCHAN aa
LOAD aa nnnnn
SETPAR
SETSER
RVALUE rrrr
SINGLE nnnnn
Serially select channel aa, where aa is ch0 to ch31
Set value of N register for channel aa, where aa is Channels 0 to 31
Channel selected by 4 bit parallel inputs (ch0 to ch15 only)
Channel selected by most recent GOCHAN operation
Set value for R register
Set value of N for single channel operation.
N value NOT stored in EEPROM
Process entry
Clear all buffers
Disable command mode
<cr>
/
#
aa = a two digit channel number from 00 to 31
nnnnn = synthesizer N register value (up to 65535)
rrrr = synthesizer R register value (up to 16383)
N TX =
N RX =
f RF
f Channelspacing
=
433.900MHz
= 17356
25kHz
R=
f TCXO
f channelspacing
=
13MHz
, So R=520
25kHz
f RF − 21.4MHz 433.900MHz − 21.4
=
= 16500
f Channelspacing
25kHz
Note:
Radiometrix Ltd
A pause of at least 50ms must be allowed between command strings (EEPROM
programming time).
SINGLE mode does not store the N value in EEPROM. Therefore the unit is inoperative after
a power down until either another valid SINGLE command is received, or mode is changed
by a GOCHAN, SETPAR or SETSER command. SINGLE mode is intended for frequency
agile applications.
LMT2/LMR2 Data Sheet
page 6
LMT2, LMR2 channels are spaced at 50kHz interval into two frequency groups. 50kHz spacing between
sequential channels minimises adjacent channel interference.
e.g. 433MHz band
Serial or Parallel
channel select
Frequency (MHz)
0 (P3:P0 = HHHH)*
433.900
1
433.950
2
434.000
3
434.050
4
434.100
5
434.150
6
7
9
434.350
10
434.400
11
434.450
12
434.500
15 (P3:P0=LLLL)*
16
433.875
17
433.925
18
433.975
19
434.025
20
434.075
21
434.125
22
434.175
23
434.225
24
434.275
25
434.325
26
434.375
27
434.425
28
434.475
29
434.525
30
434.575
31
434.625
434.250
434.300
14
Frequency (MHz)
434.200
8
13
Serial channel select
434.550
434.600
434.650
Note: Parallel select pins: H=3V, L= 0V
Radiometrix Ltd
LMT2/LMR2 Data Sheet
page 7
Condensed specifications
Frequency
Frequency stability
Channel spacing
Number of channels
Operating temperature
Spurious radiations
Transmitter
Output power
Peak deviation
TX on switching time
Modulation type
TX modulation bandwidth
Adjacent channel TX power
TX spurious
Supply
Voltage
Current
Inputs
Size
Interface
User
RF
Recommended PCB hole size
Receiver
Sensitivity
S/N ratio
AF bandwidth (-3dB)
image
Othr spurious
Blocking
Adjacent channel
LO re-radiation
Supply
Voltage
Current
Outputs
Size
Interface
User
RF
Recommended PCB hole size
Radiometrix Ltd
433MHz EU band, and 458MHz UK band
As supplied: EU version: 433.875 - 434.65MHz (25kHz steps)
UK version 458.525 - 459.1MHz (25kHz steps)
Other custom UHF bands
±1.5kHz
25kHz
16 channels controlled by parallel port
or 32 via RS232 interface
-10 ºC to +60 ºC (Storage -30 ºC to +70 ºC)
Compliant with ETSI EN 300 220-3 and EN 301 489-3
+10dBm (10mW) ±1dB (factory adjustable 1 - 25mW)
+20dBm (100mW) ±1dB (factory adjustable 25 - 100mW)
±3kHz
30ms from TXE transition
FSK (F3D)
DC – 5kHz (3V CMOS compatible)
<-37dBm
<-45dBm (no RF output in Standby)
3.1V – 15V (1-25mW)
4.1 – 15V (25 – 100mW)
34mA @ 10mW (nominal)
65mA @ 50mW (nominal)
90mA @ 100mW (nominal)
<5µA standby (TXE high or floating)
data (CMOS/TTL compatible)
33 x 23 x 9mm
10 (8) pin 0.1" pitch dual row (5+5) header
2pin 0.1” pitch
1.2mm
-118dBm for 12dB SINAD
35dB (min), 40dB (typ) on AF output
4kHz
<-60db
<-70dbm
Better than 84dB
<-60dB
-70dBm
3.1V – 15V
20mA receive
<1µA standby (RXE low)
RSSI, audio, data (quasi DC data recovery circuit)
46 x 23 x 9 mm
10 pin 0.1" pitch dual row (5+5) header
2pin 0.1” pitch
1.2mm
LMT2/LMR2 Data Sheet
page 8
RX Received Signal Strength Indicator (RSSI)
The LMR2 has wide range RSSI that measures the strength of an incoming signal over a range of 60dB or
more. This allows assessment of link quality and available margin and is useful when performing range tests.
RSSI output (V)
The output on pin 5b of the module has a standing DC bias of up to 0.5V with no signal, rising to 2.5V at
maximum indication (RF input levels of -40dBm and above). ∆Vmin-max is typically 2V and is largely
independent of standing bias variations. Output impedance is 40kΩ. Pin 5b can drive a 100µA meter directly,
for simple monitoring.
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-140 -130 -120 -110 -100 -90
-80
-70
-60
-50
-40
RF level (dBm)
Figure 6: typical RSSI level with respect to received RF level at LMR2 antenna pin
Antenna requirements
Three types of integral antenna are recommended and approved for use with the module:
A) Whip
This is a wire, rod ,PCB track or combination connected directly to RF pin of the module.
Optimum total length is 16.4cm (1/4 wave @ 433MHz). Keep the open circuit (hot) end well
away from metal components to prevent serious de-tuning. Whips are ground plane
sensitive and will benefit from internal 1/4 wave earthed radial(s) if the product is small and
plastic cased
B) Helical
Wire coil, connected directly to RF pin, open circuit at other end. This antenna is very
efficient given it’s small size (20mm x 4mm dia.). The helical is a high Q antenna, trim the
wire length or expand the coil for optimum results. The helical de-tunes badly with proximity
to other conductive objects.
C) Loop
A loop of PCB track tuned by a fixed or variable capacitor to ground at the 'hot' end and fed
from RF pin at a point 20% from the ground end. Loops have high immunity to proximity detuning.
Feature
Ultimate performance
Easy of design set-up
Size
Immunity proximity effects
Range open ground to similar antenna
Radiometrix Ltd
A
whip
***
***
*
*
500m
B
helical
**
**
***
**
200
LMT2/LMR2 Data Sheet
C
loop
*
*
**
***
100
page 9
The antenna choice and position directly controls the system range. Keep it clear of other metal in the
system, particularly the 'hot' end. The best position by far, is sticking out the top of the product. This is often
not desirable for practical/ergonomic reasons thus a compromise may need to be reached. If an internal
antenna must be used, try to keep it away from other metal components, particularly large ones like
transformers, batteries and PCB tracks/earth plane. The space around the antenna is as important as the
antenna itself.
0.5 mm enameled copper wire
close wound on 3.2 mm diameter former
RF
433 MHz = 24 turns
A. Helical antenna
Feed point 15% to 25% of total loop length
RF-GND
track width = 1mm
2
C2
C3
C1
4 to 10 cm inside area
RF
C4
B. Loop antenna
16.4cm
wire, rod, PCB-track or a combination
of these three
RF
C. Whip antenna
433 MHz = 16.4 cm total from RF pin.
Figure 7: Antenna types
Ordering Information:
Part No.
Description
LMT2-433-5
LMR2-433-5
LMT2-458-5
LMR2-458-5
Transmitter
Receiver
Transmitter
Receiver
Frequency band
(MHz)
433.875-434.650
433.875-434.650
458.525 - 459.1
458.525 - 459.1
RF power
(mW)
10
LMT2-433-5-12k5
LMR2-433-5-12k5
LMT2-458-5-12k5
LMR2-458-5-12k5
Transmitter
Receiver
Transmitter
Receiver
433.875-434.650
433.875-434.650
458.525 - 459.1
458.525 - 459.1
10
LMT2-433-10
LMR2-433-10
LMT2-458-10
LMR2-458-10
Transmitter
Receiver
Transmitter
Receiver
433.875-434.650
433.875-434.650
458.525 - 459.1
458.525 - 459.1
10
100
100
100
Channel spacing
(kHz)
25
25
25
25
Data rate
(kbps)
5
5
5
5
12.5
12.5
12.5
12.5
5
5
5
5
25
25
25
25
10
10
10
10
Note: Also available on the other UHF band frequencies subject to SAW filter availability. e.g. 315, 419, 429,
448, 465MHz etc.
Radiometrix Ltd
LMT2/LMR2 Data Sheet
page 10
Radiometrix Ltd
Hartcran House
231 Kenton Lane
Harrow, Middlesex
HA3 8RP
ENGLAND
Tel: +44 (0) 20 8909 9595
Fax: +44 (0) 20 8909 2233
[email protected]
www.radiometrix.com
Copyright notice
This product data sheet is the original work and copyrighted property of Radiometrix Ltd. Reproduction in
whole or in part must give clear acknowledgement to the copyright owner.
Limitation of liability
The information furnished by Radiometrix Ltd is believed to be accurate and reliable. Radiometrix Ltd
reserves the right to make changes or improvements in the design, specification or manufacture of its
subassembly products without notice. Radiometrix Ltd does not assume any liability arising from the
application or use of any product or circuit described herein, nor for any infringements of patents or other
rights of third parties which may result from the use of its products. This data sheet neither states nor
implies warranty of any kind, including fitness for any particular application. These radio devices may be
subject to radio interference and may not function as intended if interference is present. We do NOT
recommend their use for life critical applications.
The Intrastat commodity code for all our modules is: 8542 6000.
R&TTE Directive
After 7 April 2001 the manufacturer can only place finished product on the market under the provisions of
the R&TTE Directive. Equipment within the scope of the R&TTE Directive may demonstrate compliance
to the essential requirements specified in Article 3 of the Directive, as appropriate to the particular
equipment.
Further details are available on The Office of Communications (Ofcom) web site:
http://www.ofcom.org.uk/radiocomms/ifi/
Information Requests
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London SE1 9HA
Tel: +44 (0)845 456 3000 or 020 7981 3040
Fax: +44 (0)20 7783 4033
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Tel. +45 33896300
Fax +45 33896330
[email protected]
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