RF transmitter uses AMI encoding

IC3 is a low-power, integrated RF transmitter (Motorola, www.motorola.com) targeting ISM applications. Its voltage-controlled oscillator is a parallel-resonant Colpitts type. The varactor diode, D1, controls the modulation, and D2 sets the center frequency. The modulation, D1, is set to approximately 60 kHz/V, and the frequency adjustment, D2, is set to 7 MHz/V. The mixer of the IC serves as a buffer; you can adjust R3 for desired output power. C2/L1 and C3/L2 conjugately match the source-to-load impedances. These values can vary, depending on the parasitics of your layout. CF1 (TDK Corp, www.tdk.com) provides final filtering of the output before transmission. IC4 synthesizes the desired carrier frequency. The IC internally divides by 512 the frequency that crystal Y1 establishes. With Pin 16 of IC3 tied low, the synthesized frequency is fOUT=(2.048 MHz/512)*65*N, where N represents the digital value present on the N bus of IC. As illustrated, N can vary from 3472 to 3487, yielding 16 discrete output channels from 902.72 to 906.62 MHz in 260-kHz steps. R4 and C4 form a lowpass filter with corner frequency set to a value substantially lower than the internal reference frequency of the synthesizer or the data stream, whichever is lower. As with any RF design, you should give careful consideration to parts placement and shielding. You should also apply generous decoupling. If desired, you can hold Pin 17 of IC3 at logic...