TR3100 Datasheet, PDF (5/12 Pages) RF Monolithics, Inc – 433.92 MHz Hybrid Transceiver

Antenna
RFIO
20
Tuning
SAW
CR Filter
Tuning/ESD
TX CN CN
IN TRL1 TRL0
R_TXM
TXMOD 8 17 18
Modulation
& Bias Control
TXA2
TXA1
ASH Transceiver Block Diagram
Power Down
Control
Log
VCC1: Pin 2
VCC2: Pin 16
GND1: Pin 1
GND2: Pin 10
GND3: Pin 19
RREF: Pin 11
CMPIN: Pin 6
BBOUT
RFA1
SAW
Delay Line
RFA2
Detector
Low-Pass
Filter
LPFADJ 9
R_LPF
BB
5
Peak
Ref
6 Detector
C_BBO
PKDET 4
C_PKD
DS2
dB Below
Peak Thld
AND ₇
RXDATA
AGC Set
Gain Select
Pulse Generator
& RF Amp Bias
PRATE 14
15 PWIDTH
R_PR
R_PW
AGC
Control
AGCCAP 3
C_AGC
AGC Reset
AGC
DS1
Ref
Thld
Threshold
Control
13
THLD1
R_TH1
11 12
THLD2
R_TH2
R_REF
Figure 2
Since an amplifier-sequenced receiver is inherently a sampling
receiver, the overall cycle time between the start of one RFA1 ON
sequence and the start of the next RFA1 ON sequence should be
set to sample the narrowest RF data pulse at least 10 times.
Otherwise, significant edge jitter will be added to the detected data
pulse.
ASH Transceiver Block Diagram
Figure 2 is the general block diagram of the ASH transceiver.
Please refer to Figure 2 for the following discussions.
Antenna Port
The only external RF components needed for the transceiver are
the antenna and its matching components. Antennas presenting
an impedance in the range of 35 to 72 ohms resistive can be
satisfactorily matched to the RFIO pin with a series matching coil
and a shunt matching/ESD protection coil. Other antenna
impedances can be matched using two or three components. For
some impedances, two inductors and a capacitor will be required.
A DC path from RFIO to ground is required for ESD protection.
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 switching 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 levels. 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 flatness 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. When the receiver RF amplifiers
are 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
685 mV. For lower duty cycles, the mV/dB slope and peak-to-peak
signal level are proportionately less. The detected signal is riding
on a 1.1 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, etc.) by a series capacitor.
The correct value of the series capacitor depends on data rate,
data run length, and other factors as discussed 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 CMPIN by separate series coupling capacitors. The AGC
reset function is driven by the signal applied to CMPIN.
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©2008 by RF Monolithics, Inc.
Page 5 of 12
TR3100 - 4/4/08