參數(shù)資料
型號: TR8100
廠商: RF Monolithics, Inc.
英文描述: 916.50 MHz Hybrid Transceiver
中文描述: 916.50兆赫混合收發(fā)器
文件頁數(shù): 5/14頁
文件大?。?/td> 431K
代理商: TR8100
RF Monolithics, Inc.
RFM Europe
1999 by RF Monolithics, Inc. The stylized RFM logo are registered trademarks of RF Monolithics, Inc.
Phone: (972) 233-2903
Phone: 44 1963 251383
Fax: (972) 387-8148
Fax: 44 1963 251510
E-mail: info@rfm.com Page 5 of 14
http://www.rfm.com
TR8100-021307
Figure 2
Receiver Chain
The output of the SAW filter drives amplifier RFA1. This amplifier includes
provisions for detecting the onset of saturation (AGC Set), and for switch-
ing between 35 dB of gain and 5 dB of gain (Gain Select). AGC Set is an
input to the AGC Control function, and Gain Select is the AGC Control
function output. ON/OFF control to RFA1 (and RFA2) is generated by the
Pulse Generator & RF Amp Bias function. The output of RFA1 drives the
SAW delay line, which has a nominal delay of 0.5 μs.
The second amplifier, RFA2, provides 51 dB of gain below saturation. The
output of RFA2 drives a full-wave detector with 19 dB of threshold gain.
The onset of saturation in each section of RFA2 is detected and summed
to provide a logarithmic response. This is added to the output of the full-
wave detector to produce an overall detector response that is square law
for low signal levels, and transitions into a log response for high signal lev-
els. This combination provides excellent threshold sensitivity and more
than 70 dB of detector dynamic range. In combination with the 30 dB of
AGC range in RFA1, more than 100 dB of receiver dynamic range is
achieved.
The detector output drives a gyrator filter. The filter provides a three-pole,
0.05 degree equiripple low-pass response with excellent group delay flat-
ness and minimal pulse ringing. The 3 dB bandwidth of the filter can be set
from 4.5 kHz to 1.8 MHz with an external resistor.
The filter is followed by a base-band amplifier which boosts the detected
signal to the BBOUT pin with the receiver RF amplifiers operating at a
50%-50% duty cycle, the BBOUT signal changes about 10 mV/dB, with a
peak-to-peak signal level of up to 450 mV. The detected signal is riding on
a 1.5 Vdc level that varies somewhat with supply voltage, temperature,
etc. BBOUT is coupled to the CMPIN pin, or to an external data recovery
process (DSP), by a series capacitor. The correct value of the series
capacitor depends on data rate, data run length, and other factors as dis-
cussed in the
ASH Transceiver Designer’s
Guide.
When an external data recovery process is used with AGC, BBOUT must
be coupled to the external data recovery process and to CMPIN by sepa-
rate series coupling capacitors. The AGC reset function is driven by the
signal applied to CMPIN.
Data Slicers
The CMPIN pin drives two data slicers, which convert the analog signal
from BBOUT back into a digital stream. The best data slicer configuration
depends on the system operating parameters. Data slicer DS1 is a capac-
itively-coupled comparator with provisions for an adjustable threshold.
DS1 provides the best performance at low signal-to-noise conditions. The
threshold, or squelch, offsets the comparator’s slicing level from 0 to 90
mV, and is set with a resistor between the RREF and THLD1 pins. This
threshold allows a trade-off between receiver sensitivity and output noise
density in the no-signal condition. For best sensitivity, the threshold is set
to zero but a minimum of 9 mv should be used for proper AGC action. In
this case, noise is output continuously when no signal is present. This, in
turn, requires the circuit being driven by the RXDATA pin to be able to pro-
cess noise (and signals) continuously.
This can be a problem if RXDATA is driving a circuit that must sleep when
data is not present to conserve power, or when it its necessary to minimize
false interrupts to a multitasking processor. In this case, noise can be
greatly reduced by increasing the threshold level, but at the expense of
sensitivity. The best 3 dB bandwidth for the low-pass filter is also affected
by the threshold level setting of DS1. The bandwidth must be increased as
the threshold is increased to minimize data pulse-width variations with sig-
nal amplitude.
3G ASH Transceiver Block Diagram
RFA1
RFA2
TXA1
TXA2
SAW
Delay Line
SAW
CR Filter
Log
Antenna
RFIO
ESD
Choke
Detector
Low-Pass
Filter
BB
AGC
Control
Peak
Detector
Local Oscillator,
Pulse Generator
& RF Amp Bias
LPFADJ
RXDATA
CN
TRL1
CN
TRL0
R
REF
THLD2
THLD1
Gain Select
AGC Set
AGC Reset
Threshold
Control
BBOUT
DS2
DS1
AND
dB Below
Peak Thld
Ref
Thld
PKDET
Ref
AGC
C
BBO
C
PKD
R
LPF
R
TH2
R
TH1
R
TXM
20
8
17
18
14
15
9
5
6
4
7
13
11
12
VCC1: Pin 2
VCC3: Pin 3
VCC2: Pin 16
GND1: Pin 1
GND2: Pin 10
TX
MOD
19
CN
FGR
X
X
Data/Clock
Recovery
RXDCLK
Temperature
Master Oscillator
Selection
Power Down Control
Programming
and
Control
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