Philips Semiconductors
Product specification
Low power FM IF system
SA614A
demodulation, the maximum data rate is somewhat limited. An
optimized at 0.22µV for 12dB SINAD with minor change in the RSSI
internal capacitor limits the RSSI frequency response to about
100kHz. At high data rates the rise and fall times will not be
symmetrical.
linearity.
Any application which requires optimized RSSI linearity, such as
spectrum analyzers, cellular radio, and certain types of telemetry,
will require careful attention to limiter interstage component
selection. This will be especially true with high IF frequencies which
require insertion loss or impedance reduction for stability.
The RSSI output is a current-to-voltage converter similar to the
audio outputs. However, an external resistor is required. With a
91kΩ resistor, the output characteristic is 0.5V for a 10dB change in
the input amplitude.
At low frequencies the RSSI makes an excellent logarithmic AC
voltmeter.
Additional Circuitry
Internal to the SA614A are voltage and current regulators which
have been temperature compensated to maintain the performance
of the device over a wide temperature range. These regulators are
not accessible to the user.
For data applications the RSSI is effective as an amplitude shift
keyed (ASK) data slicer. If a comparator is applied to the RSSI and
the threshold set slightly above the no signal level, when an in-band
signal is received the comparator will be sliced. Unlike FSK
200
Q = 100
Φ
175
150
125
100
75
Q = 80
Q = 60
Q = 20
Q = 10
50
25
0
0.95
0.975
1.0
1.025
1.05
SR00334
w
wI
Dw
wI
Figure 12. Phase vs Normalized IF Frequency
+ 1 )
11
1997 Nov 07
NXP [ NXP ]
