Wideband frequency synthesizer and frequency synthesizing method thereof

Abstract

A wideband frequency synthesizer and a frequency synthesizing method thereof are provided. The wideband frequency synthesizer includes a phase-locked loop unit, a first voltage-controlled oscillating unit and a first frequency mixer unit. The phase-locked loop unit receives a reference signal and a feedback signal and generates a first oscillating signal according to the reference signal and the feedback signal. The first voltage-controlled oscillating unit generates a second oscillating signal. The first frequency mixer is coupled to the phase-locked loop unit and the first voltage-controlled oscillating unit, receives the first oscillating signal and the second oscillating signal for mixing frequencies of the first oscillating signal and the second oscillating signal to generate an output signal and taking the output signal as the feedback signal for outputting to the phase-locked loop unit.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the priority benefit of Taiwan application serial no. 102116118, filed on May 6, 2013. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.BACKGROUND[0002]1. Technical Field[0003]The invention relates to a frequency synthesizer and a frequency synthesizing method. Particularly, the invention relates to a wideband frequency synthesizer capable of improving a frequency operation range by additionally configuring a voltage-controlled oscillator and a frequency synthesizing method thereof.[0004]2. Related Art[0005]In recent years, along with booming development of wireless technology, wireless communication is widely used in people's daily life. Along with quick development of applications of communication techniques, demands on data transmission amount and data transmission speed are greatly increased, and a wide transmission bandwidth ...

AI Technical Summary

Benefits of technology

[0009]Accordingly, the invention is directed to a wideband frequency synthesizer and a frequency synthesizing method thereof, by which an output frequency range of the wideband frequency synthesizer is broadened through a low complexity circuit design.

[0018]According to the above descriptions, the frequency synthesizer applies the frequency mixer unit in collaboration with the phase-locked loop unit and the voltage-controlled oscillating unit, where the frequency mixer unit mixes frequencies of two oscillating signals output by the phase-locked loop unit and the voltage-controlled oscillating unit. Moreover, the frequency synthesizer of the invention further takes the output signal generated by the frequency mixer unit as the feedback signal, and feeds back the feedback signal to the phase-locked loop unit, such that the phase-locked loop unit is locked to a wider frequency range to accordingly generate the stable oscillating signal. In this way, the invention increases an applicable bandwidth of the wideband frequency synthesizer, and avoids a complicated hardware circuit design, so as to achieve an effect of low power consumption and low fabrication cost.

Problems solved by technology

A main challenge of the wireless communication domain lies in a highly integrated and low cost complementary metal oxide semiconductor field effect transistor (CMOSFET) chip, and in a transceiver of a communication system, a frequency synthesizer is generally used to provide a stable local oscillating signal.

Moreover, regarding the conventional frequency synthesizer, since there is only one voltage-controlled oscillator, the frequency operation range thereof is smaller, which cannot satisfy the demand on operation bandwidth in today's multi-standard communication system.

However, in the conventional technique, not only a complicated hardware circuit design is required, a higher circuit cost and power consumption are also required.

Regarding the frequency synthesizer having a plurality of frequency dividers, a balance has to be reached between a frequency resolution and the number of devices, and the operation frequency is hard to reach a continuous wideband range.

On the other hand, if operation frequencies of two sets of PLL circuits are close to each other, a frequency pulling phenomenon is occurred, which decreases the quality of the output signal.

Regarding an integrated circuit design of the frequency synthesizer in the current communication system, not only a high efficiency is required, a low cost is also required, so that it is an important issue to design a better wideband frequency synthesizer satisfying application requirements.

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