ISM无线电频率（RF）系统优化的方法

　　There are only two basic steps used to optimize the operation of a simple ISM transmitter （shown in Figure 1）： make sure that the reference frequency is properly tuned， and correctly match the output network of the transmitter to the antenna. A crystal oscillator is commonly used as the reference in both the transmitter and receiver circuits， so that optimization technique is addressed in the Receiver Optimization section below.

　　After establishing a starting point， adjustments are guided by measuring the transmitted power and the PA current as a function of frequency. The measurement setup is shown in Figure 3. The fixed crystal is removed from the board; an external signal generator is connected through a blocking capacitor to the crystal pin to allow the adjustment of frequencies from about 11MHz to 15MHz （for transmitted RF from 352MHz to 480MHz）。 The peak-to-peak voltage from the generator is set to about 500mV.