Current-Controlled Oscillator Linear Region Extension
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Solution Overview
Problem
Conventional oscillators suffer from deteriorated phase noise characteristics and deadlock states due to limited linear regions in oscillation frequency control, leading to unstable operation.
Innovation Solution
Incorporating a differential amplifier circuit with resistor elements in each current path and a regulator to set a limit voltage within the linear region, preventing oscillation frequency control voltage from entering saturation, thus enlarging the linear region and stabilizing frequency control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the oscillation frequency control voltage is allowed to vary over a wide range, then the oscillation frequency can be adjusted broadly, but the phase noise characteristics deteriorate and deadlock states occur due to entering saturation regions
Solution Approach 1:
The patent applies parameter changes by modifying the differential amplifier circuit characteristics through resistor elements. By adding resistors in series with the current paths, the linear region of the differential output current is extended, allowing broader frequency adjustment while maintaining stable operation and avoiding saturation. This changes the electrical parameters of the circuit to achieve both wide adjustment range and good phase noise characteristics.
2Device complexity
If the linear region of the differential output current is small, then the circuit is simpler, but the oscillation frequency control becomes unstable and sensitive to noise
Solution Approach 1:
The patent uses resistor elements as intermediary components in the differential amplifier circuit. These resistors act as mediators that extend the linear region of the differential output current without fundamentally changing the circuit architecture. The resistors smooth the current characteristics and expand the control range, improving stability while maintaining relative circuit simplicity.
3Adaptability or versatility
If the oscillation frequency control voltage enters the saturation region, then the control range is maximized, but the PLL becomes unable to control frequency (deadlock state)
Solution Approach 1:
The patent implements beforehand cushioning by pre-extending the linear region of the differential amplifier through the addition of resistor elements. This preparatory modification ensures that even when the control voltage varies widely, the circuit remains within its linear operating region, preventing deadlock states before they can occur. The resistors provide a cushion against saturation by smoothing the current characteristics.
Data Source
AI summary
In the current-controlled oscillator performing an oscillation frequency control by using a differential amplifier circuit, resistors are inserted to each current path of a differential pair of the differential amplifier circuit, and thereby an inclination of output currents Ia, Ib of a differential pair is small in the linear line region. Further, by setting a reference voltage applied to a base of a transistor of one side of the differential pair lowly, the linear region is shifted to low voltage side, and thereby a saturation region of the low voltage side is not occurred. Moreover, when a comparison result of a phase of an output signal of the current-controlled oscillation circuit and a reference signal is converted to an oscillation frequency control voltage Vtune, by limiting an upper limit voltage of the Vtune by an output of a regulator in stead of a positive voltage power source Vcc of common circuit, the Vtune does not move to a saturation region upper than the linear region. According to the current-controlled oscillator, it is possible to prevent deterioration of a phase noise characteristic or deadlock caused by an inclination or a width of the linear region of the output characteristic of the differential amplifier circuit.