AD6190
P RO D UCT D ESCRIP TIO N
T he AD6190 is a complete RF/IF transceiver for operation in
the 902 MH z–928 MH z Industrial, Scientific and Medical
(“ISM”) frequency band. T ogether with a suitable spread-
spectrum controller, the AD6190 can be used to design
a spread-spectrum system compliant with FCC “Part 15”
(47CFR15.247) regulations. T he AD6190 is a fully compatible
companion chip to the Zilog Z87L00 “ZPhone” frequency-
hopping spread-spectrum controller.
LO
IF
OUT
RF
IN
AD6190
90؇
90؇
T he AD6190 includes a receive path of LNA, image-reject
mixer, IF amplifier and limiter amplifier with RSSI. T he trans-
mit path accepts a 10.7 MHz IF input signal, and uses image-
reject upconversion to the 902 MHz–928 MHz band. Frequency
control is achieved using an on-chip VCO and dual-modulus
prescaler connected to an inexpensive low frequency PLL for
channel selection and frequency hopping.
Figure 9. Im age-Reject Mixer
T he RF signal, containing both the desired signal at (FLO + FIF
)
and another possible signal at the image frequency of (FLO – FIF) is
applied to two mixers in parallel. T hese mixers are driven by
local oscillator signals in quadrature. T he mixer outputs at the
two mixer IF ports contain both the desired signal and the
image signal. H owever, the outputs of the two mixers are in
quadrature (shifted 90 degrees relative to each other). T he
outputs of the two mixers are then shifted another 90 degrees
relative to each other in a phase-shift network. T he two mixer
outputs thus contain the desired signal and the image signal
exactly 180 degrees out of phase. By adding (or subtracting) the
two signals, the undesired image signals cancel, the desired
signal components add, and image-rejection occurs. Local oscil-
lator leakage is suppressed by the use of doubly-balanced mixers.
Additionally, an on-chip voltage regulator stabilizes the VCO to
prevent LO pushing due to power supply variations.
AP P LYING TH E AD 6190
Receive Signal P ath
T he AD6190 Low Noise Amplifier (LNA) and image-reject
mixer together provide downconverter with a total gain of 24 dB
and a typical Noise Figure (NF) of 4.2 dB.
T he LNA input port exhibits an impedance of 320-j61 at
915 MH z. In order to provide an optimum match to a 50 Ω
source, the network shown in Figure 8 should be used.
T he quality of the image rejection is a function of the phase and
amplitude matching of the quadrature branches of the LO and
IF phase-shift networks. In the AD6190, image-rejection is
typically 33 dB.
The mixer output that drives the input side of the first
10.7 MHz filter should also be connected through a parallel
RLC network of 6.8 pF, 1 kΩ, and 7 pF to the power supply to
match the 330 Ω filter impedance.
82pF
50⍀
RF IN
15nH
2.2pF
T he 10.7 MH z IF signal is then filtered and amplified by a
24 dB fixed gain. T he output of this stage is further filtered, and
applied to a 6-stage limiting amplifier. T he limiter output signal
is typically 450 mV p-p into a 30 kΩ, 30 pF load, with a dc
offset level of approximately 1.76 V dc.
AD6190
Figure 8. LNA Input Matching Circuit
All 10.7 MHz IF filters are assumed to be standard 330 Ω imped-
ance ceramic types. The AD6190 RX IF signal chain and TX IF
input includes internal matching resistors for this impedance.
T he frequency plan of the AD6190 provides the lowest possible
RF implementation cost. A single conversion design is used with
a 10.7 MHz IF to take advantage of the very low cost filters
available. However, since the 902 MHz–928 MHz band is wider
than twice the IF, it is possible that undesired in-band signals
will be mixed down to the IF. T hese images could cause inter-
ference to the desired signal. It is thus necessary to provide
tunable filtering before the receive mixer, or some other ap-
proach to eliminate interference from image signals.
When used with the Zilog Z87L00 Spread-Spectrum Controller
IC, the 10.7 MHz IF signal contains the received data encoded in
FSK modulation with approximately a ±33 kHz deviation. The
Z87L00 performs the FSK demodulation in the digital domain.
T he RSSI (Received Signal Strength Indicator) signal represents
the strength of the received signal, linear in dB, and scales with
supply voltage. With a 3.3 V supply (through a 10 Ω resistor on
the VCCIF pin), an RF signal level of –100 dBm at the LNA
input will produce an RSSI voltage of approximately 900 mV.
T he RSSI voltage will increase with increasing RF input level,
at approximately 22 mV/dB to approximately 2.4 V at
–30 dBm input. T he RSSI output voltage remains above 2.4 V
for input levels up to +15 dBm.
In the AD6190, a technique known as “image-reject” (or SSB)
mixing is used. T his technique suppresses image interference by
using a pair of mixers with quadrature local oscillators. See
Figure 9.
–6–
REV. 0
5秒后页面跳转
LF353数据手册解读：特性、应用、封装、引脚说明、电气参数及替换型号推荐
A4950资料手册解读：特性、应用、封装、引脚功能、电气参数及代换型号
一文带你解读74HC244资料手册：特性、应用场景、封装方式、引脚配置说明、电气参数、推荐替代型号
AD623资料手册解读：特性、应用、封装、引脚功能及电气参数
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
技术参数
数据手册
如果您发现信息不准确，
