Philips Semiconductors

Product specification

SA614A

Low power FM IF system

1997 Nov 07

11

optimized at 0.22

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.

At low frequencies the RSSI makes an excellent logarithmic AC

voltmeter.

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

demodulation, the maximum data rate is somewhat limited. An

internal capacitor limits the RSSI frequency response to about

100kHz. At high data rates the rise and fall times will not be

symmetrical.

The RSSI output is a current-to-voltage converter similar to the

audio outputs. However, an external resistor is required. With a

91k

the input amplitude.

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.

200

175

150

125

100

75

50

25

0

0.95

0.975

1.0

1.025

1.05

Φ

Q = 100

Q = 80

Q = 60

Q = 20

Q = 10

SR00334

Figure 12. Phase vs Normalized IF Frequency w

w

I

+ 1 ) Dw

w

I