The controlled oscillator synthesizer is sometimes preferred over the direct one because

Solution (By Examveda Team)

The controlled oscillator synthesizer is sometimes preferred over the direct one because of its improved frequency stability. Let’s break this down in more detail.

Controlled Oscillator Synthesizer:
A controlled oscillator synthesizer is a type of frequency synthesizer where the output frequency is controlled by a reference signal, often a voltage-controlled oscillator (VCO). This system allows for the generation of a wide range of frequencies with high precision.

Direct Oscillator Synthesizer:
On the other hand, a direct oscillator synthesizer generates frequencies by directly using a single oscillator and typically relies on components like crystals to define the output frequency.

Explanation of the Correct Answer:
Option B: Its frequency stability is better
The controlled oscillator synthesizer is preferred over the direct one primarily because it offers better frequency stability. This means that it maintains a consistent frequency output over time, even when external factors like temperature, voltage variations, or aging affect the system. The voltage-controlled oscillator in the controlled synthesizer is designed to be highly stable, often incorporating advanced feedback mechanisms that regulate frequency fluctuations. As a result, these synthesizers can offer superior performance in applications where precise and stable frequencies are critical, such as in communication systems and signal processing.

Other Options:
Option A: It is a simpler piece of equipment
This option is not correct. The controlled oscillator synthesizer is generally more complex due to the need for additional components such as feedback systems and voltage-controlled oscillators. In contrast, a direct oscillator synthesizer might be simpler, using fewer components for frequency generation.

Option C: It does not require crystal oscillator
While it is true that some controlled oscillator synthesizers do not rely directly on a crystal oscillator, this is not the main reason they are preferred. The focus is on the stability and flexibility of the frequency output rather than the type of oscillator used. Many controlled oscillators still use crystals for frequency references, but they are designed to be less susceptible to instability.

Option D: It is relatively free of spurious frequency
While controlled oscillator synthesizers may have fewer spurious frequencies than direct ones, this is not their primary advantage. Spurious frequencies, which are unwanted signals at frequencies different from the intended one, can still be present in both types of systems. However, controlled oscillator synthesizers are more likely to mitigate this issue due to their frequency stability and better design features for filtering and regulation.

In conclusion, the controlled oscillator synthesizer is preferred because of its superior frequency stability (Option B), which ensures more reliable performance, especially in sensitive applications.