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參數(shù)資料
| 型號： | TR3005 |
| 廠商： | RF Monolithics, Inc. |
| 英文描述： | 403.50 MHz Hybrid Transceiver |
| 中文描述： | 403.50兆赫混合收發(fā)器 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 196K |
| 代理商： | TR3005 |
sig nal-to-noise con di ions. The thresh old, or squelch, off sets the
com para or’s slic ng level from 0 to 90 mV, and is set with a re sis or
be ween the RREF and THLD1 pins. This thresh old al ows a trade-
off be ween re ceiver sen si iv ty and out put noise den sity in the
no-signal con di ion. For best sen si iv ty, the thresh old is set to 0. In
this case, noise is out put con in u ously when no sig nal is pres ent.
This, in turn, re quires the cir cuit be ng driven by the RXDATA pin to
be able to pro cess noise (and sig nals) con in u ously.
This can be a prob em if RXDATA is driv ng a cir cuit that must
“sleep” when data is not pres ent to con serve power, or when it its
nec es sary to min mize false in er upts to a multitasking pro ces sor.
In this case, noise can be greatly re duced by in creas ng the thresh
old level, but at the ex pense of sen si iv ty. The best 3 dB band width
for the low-pass fil er is also af ected by the thresh old level set ing of
DS1. The band width must be in creased as the thresh old is in
creased to min mize data pulse-width vari a ions with sig nal am pli
tude.
Data slicer DS2 can over come this com pro mise once the sig nal
level is high enough to en able its op er a ion. DS2 is a “dB- below-
peak” slicer. The peak de ec or charges rap dly to the peak value of
each data pulse, and de cays slowly in be ween data pulses (1:1000
ra io). The slicer trip point can be set from 0 to 120 mV be ow this
peak value with a re sis or be ween RREF and THLD2. A thresh old
of 60 mV is the most com mon set ing, which equates to “6 dB be ow
peak” when RFA1 and RFA2 are run ning a 50%-50% duty cy cle.
Slicing at the “6 dB-below-peak” point re duces the sig nal am pli ude
to data pulse-width vari a ion, al ow ng a lower 3 dB fil er band width
to be used for im proved sen si iv ty.
DS2 is best for ASK mod u a ion where the trans mit ed wave orm
has been shaped to min mize sig nal band width. How ever, DS2 is
sub ect to be ng tem po arily “blinded” by strong noise pulses, which
can cause burst data er ors. Note that DS1 is ac ive when DS2 is
used, as RXDATA is the log cal AND of the DS1 and DS2 out puts.
DS2 can be dis abled by leav ng THLD2 dis con nected. A non-zero
DS1 thresh old is re quired for proper AGC op er a ion.
AGC Con rol
The out put of the Peak De ec or also pro vides an AGC Re set sig nal
to the AGC Con rol func ion through the AGC com para or. The pur
pose of the AGC func ion is to ex end the dy namic range of the re
ceiver, so that two trans ceiv ers can op er ate close to gether when
run ning ASK and/or high data rate mod u a ion. The on set of sat u a
tion in the out put stage of RFA1 is de ected and gen er ates the AGC
Set sig nal to the AGC Con rol func ion. The AGC Con rol func ion
then se ects the 5 dB gain mode for RFA1. The AGC Com para or
will send a re set sig nal when the Peak De ec or out put (mul i plied by
0.8) falls be ow the thresh old volt age for DS1.
A ca pac or at the AGCCAP pin avoids AGC “chat er ng” dur ng the
time it takes for the sig nal to prop a gate through the low-pass fil er
and charge the peak de ec or. The AGC ca pac or also al ows the
hold-in time to be set lon ger than the peak de ec or de cay time to
avoid AGC chat er ng dur ng runs of “0” bits in the re ceived data
stream. Note that AGC op er a ion re quires the peak de ec or to be
func ion ng, even if DS2 is not be ng used. AGC op er a ion can be
de eated by con nect ng the AGCCAP pin to Vcc. The AGC can be
latched ON once en gaged by con nect ng a 150 kilohm re sis or be
tween the AGCCAP pin and ground in lieu of a ca pac or.
Re ceiver Pulse Gen er a or and RF Am pli ier Bias
The re ceiver am pli ier-sequence op er a ion is con rolled by the Pulse
Gen er a or & RF Am pli ier Bias mod ule, which in turn is con rolled by
the PRATE and PWIDTH in put pins, and the Power Down (sleep)
Con rol Sig nal from the Mod u a ion & Bias Con rol func ion.
In the low data rate mode, the in er val be ween the fall ng edge of
one RFA1 ON pulse to the ris ng edge of the next RFA1 ON pulse
t
PRI
is set by a re sis or be ween the PRATE pin and ground. The in
ter val can be ad usted be ween 0.1 and 5 μs. In the high data rate
mode (se ected at the PWIDTH pin) the re ceiver RF am pli i ers op er
ate at a nom nal 50%-50% duty cy cle. In this case, the start-to-start
pe iod t
PRC
for ON pulses to RFA1 are con rolled by the PRATE re
sis or over a range of 0.1 to 1.1 μs.
In the low data rate mode, the PWIDTH pin sets the width of the ON
pulse t
PW1
to RFA1 with a re sis or to ground (the ON pulse width
t
PW2
to RFA2 is set at 1.1 times the pulse width to RFA1 in the low
data rate mode). The ON pulse width t
PW1
can be ad usted be ween
0.55 and 1 μs. How ever, when the PWIDTH pin is con nected to Vcc
through a 1 M re sis or, the RF am pli i ers op er ate at a nom nal
50%-50% duty cy cle, fa cil at ng high data rate op er a ion. In this
case, the RF am pli i ers are con rolled by the PRATE re sis or as de
scribed above.
Both re ceiver RF am pli i ers are turned off by the Power Down Con
trol Sig nal, which is in voked in the sleep and trans mit modes.
Trans mit er Chain
The trans mit er chain con sists of a SAW de ay line os cil a or fol
lowed by a mod u ated buffer am pli ier. The SAW fil er sup presses
trans mit er har mon cs to the an enna. Note that the same SAW de
vices used in the am pli ier-sequenced re ceiver are re used in the
trans mit modes.
Trans mit er op er a ion sup ports two mod u a ion for mats, on-off
keyed (OOK) mod u a ion, and am pli ude-shift keyed (ASK) mod u a
tion. When OOK mod u a ion is cho sen, the trans mit er out put turns
com pletely off be ween “1” data pulses. When ASK mod u a ion is
cho sen, a “1” pulse is rep e sented by a higher trans mit ed power
level, and a “0” is rep e sented by a lower trans mit ed power level.
OOK mod u a ion pro vides com pat bil ty with first-generation ASH
tech nol ogy, and pro vides for power con ser va ion. ASK mod u a ion
must be used for high data rates (data pulses less than 30 μs). ASK
mod u a ion also re duces the ef ects of some types of in er er ence
and al ows the trans mit ed pulses to be shaped to con rol mod u a
tion band width.
The mod u a ion for mat is cho sen by the state of the CNTRL0 and
the CNTRL1 mode con rol pins, as dis cussed be ow. When ei her
mod u a ion for mat is cho sen, the re ceiver RF am pli i ers are turned
off. In the OOK mode, the de ay line os cil a or am pli ier TXA1 and
buffer am pli ier TXA2 are turned off when the volt age to the TXMOD
in put falls be ow 220 mV. In the OOK mode, the data rate is lim ted
by the turn-on and turn-off times of the de ay line os cil a or, which
are 12 and 6 μs re spec ively. In the ASK mode TXA1 is bi ased ON
con in u ously, and the out put of TXA2 is mod u ated by the TXMOD
in put current. Min mum out put power oc curs in the ASK mode when
the mod u a ion driver sinks about 10 μA of cur ent from the TXMOD
pin.
The trans mit er RF out put power is pro por ional to the in put cur ent
to the TXMOD pin. A se ies re sis or is used to ad ust the peak trans
mit er out put power. 0 dBm out put power re quires about 250 μA of
in put cur ent.
Trans ceiver Mode Con rol
The four trans ceiver op er at ng modes – re ceive, trans mit ASK,
trans mit OOK, and power-down (sleep), are con rolled by the Mod u
la ion & Bias Con rol func ion, and are se ected with the CNTRL1
6
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