Philips Semiconductors

Product specification

SA626

Low voltage high performance mixer FM IF system

with high-speed RSSI

1997 Sept 25

12

RF GENERATOR

HP8903A DISTORTION

ANALYZER

SCOPE

DC VOLTMETER

240MHz

DE-EMPHASIS

FILTER

RSSI

AUDIO

SA626 DEMO BOARD

LO / GENERATOR

229.3MHz

C–MESSAGE

SR00479

Figure 10. SA626 Application Circuit Test Set Up

NOTES:

1. C-message: The C-message and de-emphasis filter combination has a peak gain of 10 for accurate measurements. Without the gain, the

measurements may be affected by the noise of the scope and HP8903A analyzer. The de-emphasis filter has a fixed -6dB/Octave slope

between 300Hz and 3kHz.

2. Ceramic filters: The ceramic filter can be SFE10.7MA5-A made by Murata which has 280kHz IF bandwidth.

3. RF generator: Set your RF generator at 240.000MHz, use a 1kHz modulation frequency and a 125kHz deviation.

4. Sensitivity: The measured typical sensitivity for 12dB SINAD should be 0.54

µV or –112dBm at the RF input.

5. Layout: The layout is very critical in the performance of the receiver. We highly recommend our demo board layout.

6. RSSI: The smallest RSSI voltage (i.e., when no RF input is present and the input is terminated) is a measure of the quality of the layout and

design. If the lowest RSSI voltage is 500mV or higher, it means the receiver is in regenerative mode. In that case, the receiver sensitivity

will be worse than expected.

7. Supply bypass and shielding: All of the inductors, the quad tank, and their shield must be grounded. A 0.1

µF bypass capacitor on the

supply pin improves sensitivity.