RXM-900-HP-II Linx Technologies Inc, RXM-900-HP-II Datasheet - Page 6

• Manufacturer Part Number: RXM-900-HP-II
• Description: RECEIVER RF 900MHZ 8-CH PACK
• Manufacturer: Linx Technologies Inc

Specifications of RXM-900-HP-II

• Frequency: 902MHz ~ 928MHz
• Sensitivity: -95dBm
• Data Rate - Maximum: 50 kbps
• Modulation Or Protocol: FM, FSK
• Applications: Home / Industrial Automation, Remote Access, Security Alarms
• Current - Receiving: 18mA
• Data Interface: PCB, Through Hole
• Antenna Connector: Through Hole
• Voltage - Supply: 2.7 V ~ 16 V
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 18-SIP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -
• Memory Size: -
• Other names: RXM-900-HP2; RXM-900-HP2

THEORY OF OPERATION
The HP-II-RXM is a high-performance, eight-channel, dual-conversion superhet
FM receiver capable of receiving analog or digital data.
SAW BPF
LNA
IF
IF
IF
2
1
AMP
902-928 MHz
34.7 MHz BPF
10.7 MHz BPF
10.7 MHz BPF
868-887 MHz
(See Table)
VCO
RSSI
915 MHz
PLL
P
XTO
10.7 MHz FM
LIMITING
Discriminator
AMP
DATA
18 KHz
BitPERFECT™
Active
BIT SLICER
LPF
AUDIO
Figure 10: HP Series-II Receiver Block Diagram
Digital information is modulated at the transmitter using FSK (frequency shift
keying), the binary form of frequency modulation. FSK offers significant
advantages over AM-based modulation methods, i.e., increased noise immunity
and the ability of the receiver to “capture” in the presence of multiple signals.
These advantages will be particularly appreciated in crowded bands like those in
which the HP-II operates. While FSK modulation is not the most bandwidth-
efficient manner of modulating digital data, it is an excellent choice for reliable,
low-cost, low-power RF products such as the HP Series-II.
To transmit analog information the module employs FM modulation. In this mode,
simple to complex waveforms can be introduced at the transmitter’s data pin and
recovered with minimal distortion at the receiver’s analog output pin.
The user-supplied antenna is connected at pin 1 (see Figure 1). The HP-II-RXM
RF port is matched to 50 ohms to support interface to commonly available
antennas such as those manufactured by Linx.
The RF signal coming in from the antenna is filtered by a SAW (surface acoustic
wave) filter. The purpose of the SAW BPF is to attenuate unwanted RF energy
(i.e., not in the 902-928 MHz band) that is present at the antenna. A SAW device
provides significantly steeper roll-off and higher out-of-band attenuation than
other filter types such as an LC bandpass.
Once filtered by the SAW, the signal is then amplified by a Low-Noise Amplifier
(LNA) to increase the receiver sensitivity and lower the overall noise figure of the
receiver. After the LNA, the signal is mixed with a synthesized local oscillator to
perform the first frequency conversion.