Data Sheet

W
E
N
Radiometrix
Hartcran House, 231 Kenton Lane, Harrow, HA3 8RP, England
27 February 2008
Wide.co.uk
9600
QR96
Tel: +44 (0) 20 8909 9595, Fax: +44 (0) 20 8909 2233
Baud Quasi DC Data Recovery Module
The Quasi DC Recovery circuit (QR96) can be
used to improve data recovery of receiver if the
raw data is transmitted without any bit
balancing. The QR96 measures the minimum
and maximum levels of the AF output of the
receiver, averages that and compares the
original AF output signal with it. The module
can be used in applications where raw (non-bit
balanced) data need to be transmitted and
received between two UARTs.
Figure 1: QR96
Features
Recovery of data signals with frequencies down to 2Hz
Tolerates time between bit transitions as long as 250ms
Permits non-bit balanced data stream like straight ASCII
Improves link margin by about 6dB, hence doubles the line of sight range on raw data
Customisable to different data, preamble timing requirements (e.g. NMEA sentences)
Supply Voltage: 3 to 5V
Small size: 18.5 x 10 x 5.5mm
Pin outs and foot print compatible with Radiometrix SIL Receivers
Compared to conventional Data Slicer circuit currently used in the most of the FSK receivers, Quasi DC
Recovery circuit can extract non-bit balanced data at RF signal level that is 6dB lower, resulting in double the
range.
Conventional Data Slicers are based on simple ‘RC integrate and compare’ method to digitise the
demodulated analogue signal, whereas, the QR96 samples positive and negative peaks of the Audio (AF)
output and then averages them, before using that voltage as the comparator reference. QR96 behaves better
on very unbalanced (raw) data, and at the start of bursts (where the simple RC takes time to acquire or
charged to the mid average point).
sales@radiometrix.com
QR96 - Short Technical Overview
www.radiometrix.com
User interface
Side view
Top view
18.5mm
3.8 mm
10mm
4
3
2
1: 0V
2: VCC
3: AF IN
4: RXD
1
4 holes of 0.7 mm dia.
pin spacing 2.54 mm
Figure 2: QR96 pin-out and dimension
QR96 pin
1
2
3
Name
0V
Vcc
AF in
4
RXD
Function
DC supply ground
3 – 5V
AF input is connected to the AF output of the receiver, requires signal level
of 0.6V – 1.2V peak to peak on top of a DC bias level of 0.5-1.5V.
Received Data output is open collector, an external 10kΩ pull-up resistor to
the VCC is required. RXD will be inverted with respect to AF In.
Note: 20ms of preamble (55hex or square wave signal) should be received from transmitter for the mark:space
ratio of the RXD to stabilise to 50:50 on standard QR96. However, data packets with gaps >250ms (e.g. GPS
NMEA data) would require extended preamble of up to 100ms.
IC1: MCP6002
Figure 3: Schematics of QR96
Application Circuits
DC supply:
3V/5V
Vcc
10kΩ
1
1
Vcc
TXD
100kΩ
3
TXD
Vcc
RF
Transmitter
GND
RF
AF
Receiver
Vcc
RXD
AF
RXD
100kΩ
QR96
10kΩ
9
2
5
GND
9
5
Figure 4: Typical wireless RS232 interface with RF modules and QR96
sales@radiometrix.com
QR96 - Short Technical Overview
www.radiometrix.com