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參數(shù)資料
| 型號： | RF2917 |
| 廠商： | RF MICRO DEVICES INC |
| 元件分類： | 通信及網(wǎng)絡(luò) |
| 英文描述： | 433/868/915MHZ FM/FSK RECEIVER |
| 中文描述： | SPECIALTY TELECOM CIRCUIT, PQFP32 |
| 封裝： | 5 X 5 MM, PLASTIC, LQFP-32 |
| 文件頁數(shù)： | 7/14頁 |
| 文件大小： | 408K |
| 代理商： | RF2917 |
11-135
RF2917
Rev B2 010118
11
T
RF2917 T heory of Operation and Applic ation Information
The RF2917 is part of a family of low-power RF trans-
ceiver IC’s developed for wireless data communication
devices operating in the European 433/868MHz ISM
bands or the U.S. 915MHz ISM band. This IC has
been implemented in a 15GHz silicon bipolar process
technology that allows low-power transceiver operation
in a variety of commercial wireless products. The
RF2917 realizes a highly integrated, single-conversion
FM/FSK receiver with the addition of a reference crys-
tal, intermediate frequency (IF) filtering, and a few pas-
sive components. The LNA (low noise amplifier) input
of the RF2917 is easily matched to a front-end filter or
antenna by means of a DC blocking capacitor and
reactive components. The receiver local oscillator (LO)
is generated by an internalized VCO, PLL and phase
discriminator in conjunction with the external reference
crystal, loop filter and VCO resonator components.
The receiver IF section is optimized to interface with
low cost 10.7MHz ceramic filters, and its -3dB band-
width of 25MHz also allows it to be used (with lower
gain) at higher frequencies with other types of filters.
FM/FSK SYSTEMS
The receiver output functionality is determined by the
tri-state MUTE input. The three output configurations
are linear FM, FSK and mute. An on-chip 1.6MHz RC
filter, which follows the demodulator output, filters the
harmonics of the IF signal from the output data.
When in the FM mode, the FM OUT signal is the buff-
ered output from the quadrature demodulator. The out-
put signal has a fixed DC offset of V
CC
-1.0V, while the
AC level is dependent on the FM deviation, with a max-
imum level of 240mV
P-P
. For optimum operation in
either FM or FSK mode, FM deviation needs to exceed
(with margin) the carrier frequency error anticipated
between the receiver and transmitter.
When in the FSK mode, the FM OUT signal is clipped,
having a rail-to-rail output level. The FM OUT pin is
only capable of driving rail-to-rail output into a very
high impedance and small capacitance, with the
amount of capacitance determining the FM OUT band-
width. For a 3pF load, the bandwidth is in excess of
500kHz. The rail-to-rail output is also limited by the fre-
quency deviation and bandwidth of the IF filters. With
the 180kHz bandwidth filters on the evaluation boards,
the rail-to-rail output is limited to less than 140kHz.
Choosing the right IF bandwidth and deviation versus
data rate (modulation index) is important in evaluating
the applicability of the RF2917 for a given data rate.
AM SYSTEMS
The RF2919 is recommended for use in ASK/OOK
applications, however, the RF2917 may be utilized in
an AM system by using the RSSI (received signal
strength indicator) output to recover the modulation.
The FM output mode should be selected for AM opera-
tion because of the higher RSSI resolution in FM
mode.
RSSI
The RSSI output signal is supplied from a current
source and therefore requires a resistor to convert it to
a voltage. The RSSI is linear over the same range of
input power for both FM and FSK modes, but the FM
mode has higher RSSI resolution. For a 51k
resistive
mode and from 0.8V to 1.5V in FSK mode (3.6V sup-
ply). A small parallel capacitor is suggested to limit the
bandwidth and filter noise.
APPLICATION AND LAYOUT CONSIDERATIONS
The RX IN pin is DC-biased, requiring a DC blocking
capacitor. If the RF filter has DC blocking characteris-
tics, such as a ceramic dielectric filter, then a DC block-
ing capacitor is not necessary. When in power down
mode, the RX IN impedance increases. Therefore, in a
half-duplex application, the RF2917 RX IN may share
the RF filter with a transmitter output having a similar
high impedance power down characteristic. Care must
be taken in this case to account for loading effects of
the transmitter on the receiver, and vice versa, in
matching the filter to both the transmitter and receiver.
The VCO is a very sensitive block in this system. RF
signals feeding back into the VCO by either radiation or
coupling of traces may cause the PLL to become
unlocked. The trace(s) for the anode of the tuning var-
actor should also be kept short. The layout of the reso-
nators and varactor are very important. The capacitor
and varactor should be closest to the RF2917 pins and
the trace length should be as short as possible. The
inductors can be placed further away and any trace
inductance can be compensated by reducing the value
of the inductors. Printed inductors may also be used
with careful design. For best results, the physical layout
should be as symmetrical as possible.
When using loop bandwidths lower than the 5kHz
shown on the evaluation board, better supply filtering
at the resonators (and lower V
CC
noise as well) will
help reduce the phase noise of the VCO; a series
resistor of 100
to 200
and a 1
μ
F or larger capacitor
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PDF描述 |
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| RF2919 | 433/868/915MHZ ASK/OOK RECEIVER |
| RF2926 | UHF DUAL CONVERSION TRANSCEIVER |
| RF2938 | 2.4GHZ SPREAD-SPECTRUM TRANSCEIVER |
| RF2942 | UHF QUADRATURE MODULATOR AND TRANSMITTER |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| RF2919 | 制造商:RFMD 制造商全稱:RF Micro Devices 功能描述:433/868/915MHZ ASK/OOK RECEIVER |
| RF2926 | 制造商:RFMD 制造商全稱:RF Micro Devices 功能描述:UHF DUAL CONVERSION TRANSCEIVER |
| RF2926-000 | 制造商:TE Connectivity 功能描述:FEMTOSMDC005F-2 - Tape and Reel |
| RF2926PCBA | 制造商:RFMD 制造商全稱:RF Micro Devices 功能描述:UHF DUAL CONVERSION TRANSCEIVER |
| RF2938 | 制造商:RF Micro Devices Inc 功能描述:Telecommunication IC |
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