Figure 2-15. Direct-angle-modulated transmitter.
LEARNING EVENT 25: BASEBAND CIRCUITS
1. The baseband input signal is applied to the voltage-controlled oscillator (VCO).
The VCO's output
frequency of 34 MHz is varied in proportion to the baseband input frequency.
2. The amplifier amplifies the modulated subcarrier and applies the signal to the phase detector stage.
LEARNING EVENT 26: HARMONIC MIXER
The injection voltage from the multiplier stages is applied to a x4 multiplying circuit within the harmonic mixer
stage. The multiplied output is mixed with the transmit frequency from the reflex klystron after the transmit
frequency has been coupled through an isolator and a directional coupler. The output from the harmonic mixer
is a 34-MHz IF that is amplified and coupled to the phase detector.
LEARNING EVENT 27: PHASE-LOCK LOOP
1. The inputs to the phase detector consist of a modulated subcarrier and a nominal IF of 34 MHz, which is the
difference between the transmit frequency and the multiplied
2-17
SS0031
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