RX2A

The RX2A is a miniature PCB mounting UHF radio data receiver. It is an updated version of the Radiometrix RX2 incorporating a received signal strength indicator (RSSI). It allows the simple implementation of data links at speeds up to 64kbps and distances up to 75 metres in-building or 300 metres over open ground.

Figure 1: RX2A-433-10 and TX2-433-40

Features

  • Designed to comply with harmonised radio standard EN 300 220-3 and EMC standard EN 301 489-3
  • Data rates up to 64kbps
  • Usable range up to 300m
  • Versions available on 433.92MHz and 434.42MHz
  • Fully screened

Technical Summary

  • Single conversion FM superhet
  • SAW front end filter gives >50dB image rejection
  • Operation from 2.7V to 16V @ 12mA
  • Built-in regulator for improved stability and supply noise rejection
  • -101dBm sensitivity @ 1ppm BER, 64kbps version
  • -108dBm sensitivity @ 1ppm BER, 10kbps version
  • RSSI output with 60dB range
  • Extremely low LO leakage, <-125dBm
 
Figure 2: RX2A block diagram
 

Figure 3: RX2A physical dimensions
 
Pin Description
Pin
Name
Function
1 RF IN 50W input from the antenna. DC isolated
2 RF GND RF ground pin, internally connected to the module screen and pin 4 (0V). This pin should be connected to the RF return path (coax braid, main PCB ground plane etc.)
3 RSSI Received signal strength indicator with 60dB range. See page 4 for typical characteristics
4 0V DC supply ground. Internally connected to pin 2 and module screen
5 Vcc +2.7V to +16.0V DC supply. Max ripple content 0.1Vp-p. Decoupling is not generally required
6 AF out Buffered and filtered analogue output from the FM demodulator. Standing DC bias 1.1V approx. External load should be >10kW // <100pF
7 RXD Digital output from the internal data slicer. The data is a squared version of the signal on pin 6 (AF) and is true data, i.e. as fed to the transmitter. Output is "open-collector" format with internal 10kW pull-up to Vcc (pin 5).
Absolute maximum ratings

Exceeding the values given below may cause permanent damage to the module.

Operating temperatutre - 20°C to +70°C
Storage temperatutre -40°C to +100°C
   
Vcc(pin5) -0.1V to +16V
RSSI, AF, RXD (pins 3,6,7) -0.1V to + 3V
RF IN (pin 1) ±50V DC, +10dBm RF
Performance specifications
(Vcc = 5.0V / temperature = 20ºC unless stated)
pin
min.
typ.
max.
units
notes
DC supply
Voltage
5
2.7
5
16
V
Ciurrent
5
9
10
18
mA
1
 
RF/IF
RF sensitivity for 10dB (S+N/N)
1, 6
-
-115
-
dBm
10kbps version
RF sensitivity for 10dB (S+N/N)
1, 6
-
-108
-
dBm
64kbps version
RF sensitivity for 1ppm BER
1, 6
-
-108
-
dBm
10kbps version
RF sensitivity for 1ppm BER
1, 6
-
-101
-
dBm
64kbps version
RSSI range
1, 3
-
60
-
dB
IF bandwidth
-
-
180
-
kHz
Image rejection
1
50
54
-
dB
½-IF spurious rejection
1
100
-
-
dB
IF rejection (10.7MHz)
1
100
-
-
dB
LO leakage, conducted
1
-
-125
-110
dBm
 
Baseband
Baseband bandwidth @ -3dB
6
0
-
7.8
kHz
10kbps version
Baseband bandwidth @ -3dB
6
0
-
50
kHz
64kbps version
AF level
6
350
450
550
mVp-p
2
DC offset on AF out
6
0.45
1.1
1.75
V
3
Distortion on recovered AF
6
-
1
10
%
3
Ultimate (S+N)/N
6
-
40
-
dB
Load capacitance, AFout/RXD
6, 7
-
-
100
pF
 
DYNAMIC TIMING
Power up with signal present
Power up to valid RSSI
3, 5
-
1
-
ms
Power up to stable data
5, 7
-
10
30
ms
3, 10kbps version
Power up to stable data
5, 7
-
5
10
ms
3, 64kbps version
 
Signal applied with supply on
RSSI response time (rise/fall)
1, 3
-
100
-
ms
Signal to stable data
1, 7
-
5
30
ms
3, 10kbps version
Signal to stable data
1, 7
-
5
10
ms
3, 64kbps version
 
Time between data transitions
7
0.1
-
15
ms
4, 10kbps version
Time between data transitions
7
15.6
-
1500
ms
4, 64kbps version
Mark:space ratio
7
20
50
80
%
5
   
Notes: 1. Current increases at higher RF input levels (>-20dBm and above).
  2. For received signal with ±40kHz FM deviation
  3. Typical figures are for signal at centre frequency, max. figures are for ±50kHz offset
  4. For 50:50 mark to space ratio (i.e. squarewave)
  5. Average over 30ms (10kbps version) or 3ms (64kbps version) at maximum data rate
Power supply requirements

The RX2A incorporates a built-in regulator which delivers a constant 2.8V to the module circuitry when the external supply voltage is 2.85V or greater, with 40dB or more of supply ripple rejection. This ensures constant performance up to the maximum permitted supply rail and removes the need for external supply decoupling except in cases where the supply rail is extremely poor (ripple/noise content >0.1Vp-p).

Note, however, that for supply voltages lower than 2.85V the regulator is effectively inoperative and supply ripple rejection is considerably reduced. Under these conditions the ripple/noise on the supply rail should be below 10mVp-p to avoid problems. If the quality of the supply is in doubt, it is recommended that a 10mF low-ESR tantalum or similar capacitor be added between the module supply pin (Vcc) and ground, together with a 10W series feed resistor between the Vcc pin and the supply rail.
 
Received Signal Strength Indicator (RSSI)

The module incorporates a wide range RSSI which measures the strength of an incoming signal over a range of approximately 60dB. This allows assessment of link quality and available margin and is useful when performing range tests.

Please note that the actual RSSI voltage at any given RF input level varies somewhat between units. The RSSI facility is intended as a relative indicator only - it is not designed to be, or suitable as, an accurate and repeatable measure of absolute signal level or transmitter-receiver distance.

The output on pin 3 of the module has a standing DC bias of 0.15V-0.45V (0.25V typ.) with no signal, rising to 0.9-1.3V (1.15V typ.) at maximum indication. The RSSI output source impedance is high (~50kW) and external loading should therefore be kept to a minimum.

To ensure a fast response the RSSI has limited internal decoupling of 1nF to ground. This may result in a small amount of ripple on the DC output at pin 3 of the module. If this is a problem further decoupling may be added at the expense of response speed, in the form of a capacitor from pin 3 to ground. For example, adding 10nF here will increase RSSI response time from 100µs to around 1ms. The value of this capacitor may be increased without limit.
Typical RSSI characteristic is shown below (this is for indicative purposes only and is not a guarantee of actual RSSI characteristics):
Figure 4: Typical RSSI response curve
 
Module mounting considerations

The module may be mounted vertically or bent horizontal to the motherboard. Good RF layout practice should be observed - in particular, any ground return required by the antenna or feed should be connected directly to the RF GND pin at the antenna end of the module, and not to the OV pin which is intended as a DC ground only. All connecting tracks should be kept as short as possible to avoid any problems with stray RF pickup.

If the connection between module and antenna does not form part of the antenna itself, it should be made using 50W microstrip line or coax or a combination of both. It is desirable (but not essential) to fill all unused PCB area around the module with ground plane.

The module may be potted if required in a viscous compound which cannot enter the screen can.

Warning: DO NOT wash the module. It is not hermetically sealed.
Figure 5: Module mounting options
Variants and ordering information

The RX2A receiver is manufactured in several variants depending on the :

Data rate:    
Slower version: 7.8kHz baseband B/W data rate up to 10kbps (suffix -10)
Faster version: 50kHz baseband B/W data rate up to 64kbps (suffix -64)

Frequency:  433.92MHz (suffix -433)
                    434.42MHz (suffix -434)

The following variants are standard:

RX2A-433-10 (433.92MHz, 10kbps)
RX2A-433-64 (433.92MHz, 64kbps)

For other variants please contact our Sales Department

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:
Licensing policy manual