Application of frequency multiplier circuit (MC1596)

When two carriers of the same frequency are input, the MC1596 can be used as a frequency multiplier. Since the output signal only contains the frequency ω1±ω2, when ω1=ω2, only the quantity 2ω1 will be output. [url=../Upload/20065901555950.gif] The balanced modulator circuit shown in Figure 1 can be used as a broadband low-frequency frequency multiplier after modification. The modification method is to add AC coupling between the two input terminals and short-circuit the terminals 2 and 3. Short-circuiting terminals 2 and 3 will improve the sensitivity and frequency multiplication gain of the circuit. Figure 2 is the modified low-frequency frequency multiplier circuit. When this circuit is used in the frequency range below lMHz, the amplitude of all spurious outputs is more than 30dB lower than the second frequency component. In order to obtain the best output spectrum purity, the differential amplifier should work in the linear region. For the circuit in Figure 2, the maximum input level should be 15mV (rms). If a 1kΩ resistor is connected between terminals 2 and 3, and a 10:1 voltage divider is used to reduce the carrier terminal signal level to 1/10 of the modulation terminal level, the circuit performance will be better. MCl596 can also be used as an RF frequency multiplier, and its performance is still quite good when operating in the UHF band. Either wideband output or tuned output can be used. In the UHF and VHF frequency bands, the MC1596's suppression effect on spurious output is not very good. Even so, when using wideband output to multiply the frequency of the 200MHz signal, the amplitude of the 400MHz component in the output signal is still the highest, and the spurious output is more than 7dB lower than the 400MHz output. Above this frequency, without output filtering, the MC1596 still performs better than the triode frequency multiplier. Figure 3 is a 150-300MHz frequency multiplier with an output filter. All spurious outputs are more than 20dB lower than the desired 300MHz output.