| 9600 Baud Quasi DC
Data Recovery Module |
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QR96
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| 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 |
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Recovery of data signals
with frequencies down to 2Hz
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Tolerates time between
bit transitions as long as 250ms
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Permits non-bit balanced
data stream like straight ASCII
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Improves link margin
by about 6dB, hence doubles the line of sight range on raw
data
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Customisable to different
data, preamble timing requirements (e.g. NMEA sentences)
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Wide supply range
from 3.6V to 15V
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Small size: 18.5 x
10 x 5.5mm
- Pin outs and foot print compatible with
Radiometrix SIL Receivers
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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).
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User interface
Figure 2: QR96 pin-out and dimension
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| QR48 pin |
Name |
Function |
| 1 |
0V |
DC supply ground |
| 2 |
Vcc |
3.6V - 15V |
| 3 |
AF in |
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 |
| 4 |
RXD |
Received Data output is open
collector, an external 10kW pull-up
resistor to the VCC is required. RXD will be inverted with
respect to AF In |
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| 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. |
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Figure 3: Schematics of QR96
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| Application
Circuits |
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Figure 4: Typical wireless RS232 interface
with RF modules and QR96
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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
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