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Design Notes

Cross Modulation Test System

This example demonstrates an IS95 cross modulation test system.

• An Offset QSPK (OPSK) signal with Root Raised Cosine (RRC) filtering (alpha = 0.265), centered at 1880MHz with a symbol rate of1.2288MHz is used to simulate a mobile phone transmitted signal.

• A signal tone with a power level of -30dBm centered at 1889.986MHz is used to simulate a CW jammer.

• An attenuator and a combiner are used to simulate the PCS duplexer of the mobile phone.

The following graphs are shown:

• The spectrum at the output of the mobile phone's LNA ("Spectrum at Output of RX LNA" graph).

• The spectrum of the jammer ("Jammer Intermod" graph).

• The spectrum of the transmitter ("OQPSK Signal Centered at 1880MHz" graph).

• Adjacent Channel Power Ratio (ACPR) of transmitted signal ("ACPR" graph)

           - Center frequency of 1880MHz, and bandwidth of 1.23MHz

            - Offset frequency 1.23MHz and bandwidth of 30kHz

• Cross Modulation Power ("Cross Mod Power dBm per Channel" graph)

• Total signal power of transmitted signal ("TX Signal Power graph").

As the simulation is running you can tune the IP3 of the LNA.

As you tune on IP3 you will see the cross modulation power increase or decrease.

System Diagram - Cross Modulation Test System

Graph - ACPR

DB(ACPR(VSA.M1,1880,3,1.23,3,1.23,3,30,2,1880,3,1.23,3,0,1000,0,10,0,-1,0,-1,0,0.5,0,1,0)) (dBm) Cross Modulation Test System Power DB(ACPR(VSA.M1,1880,3,1.23,3,1.23,3,30,2,1880,3,1.23,3,0,1000,0,10,0,-1,0,-1,0,0.5,0,1,0)) Cross Modulation Test System
-6.07768 -70.8323

Graph - Cross Mod Power dBm per channel

DB(PWR_vsT(TP.TP2,1888.7,3,1.25,3,1,1000,0,16,1,-1,0,-1,10,1,0,0.5,0,0,0,0,0)) (ns) Cross Modulation Test System Time DB(PWR_vsT(TP.TP2,1888.7,3,1.25,3,1,1000,0,16,1,-1,0,-1,10,1,0,0.5,0,0,0,0,0)) (dBm) Cross Modulation Test System
1.44844e+08 -95.5542

Graph - TX Signal Power

DB(PWR_vsT(TP.TP1,1880,3,1.23,3,1,1000,0,8,1,-1,0,-1,10,1,0,0.5,0,0,0,0,0)) (ns) Cross Modulation Test System Time DB(PWR_vsT(TP.TP1,1880,3,1.23,3,1,1000,0,8,1,-1,0,-1,10,1,0,0.5,0,0,0,0,0)) (dBm) Cross Modulation Test System
1.44883e+08 18.8972