LM1863 datasheet(5/14 Pages) NSC

5 / 14 page

Performance Characteristics of Applications Circuit

TLH5185 – 12

TLH5185 – 13

TLH5185 – 14

TLH5185 – 15

Cross modulation is

measured using the

following dummy an-

tenna

The following procedure was used to measure cross modulation

1 Tune the radio to the center frequency of interest and tune VGEN to this same frequency

2 Set at 0 dB audio reference with VGEN e10 mV RMS and 30% AM mod fMOD e 1 kHz

3 Remove the modulation from VGEN1 and set the level of VGEN1

4 Set the modulation level of VGEN2 e 80% at fMOD e 1 kHz and tune VGEN2 g 40 kHz away from

center frequency

5 Increase the level of VGEN2 until b40 dB of audio is recovered The level of VGEN2 is the cross

modulation measurement

TLH5185 – 16

Additional Performance Information

THD for 80% modulation for fMODe1 kHZ at

VGENe1V is 05%

VGENe10 mV is 04%

Tweet k2% at all input levels

Typical time for valid stop indication k 50 ms

Note

Tweet is an audio tone produced by the 2nd and 3rd harmonic of the IF beating against the received

signal It is measured as an equivalent modulation level ie 30% tweet has the same amplitude at the

detector as a desired signal with 30% modulation

LM1863 Datasheet(PDF) 5 Page - National Semiconductor (TI)