Oscillators – Automatic frequency stabilization using a phase or frequency... – With reference oscillator or source
Reexamination Certificate
1998-08-05
2001-06-19
Kinkead, Arnold (Department: 2817)
Oscillators
Automatic frequency stabilization using a phase or frequency...
With reference oscillator or source
C331S014000, C331S045000, C327S105000, C327S107000
Reexamination Certificate
active
06249189
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a circuit of a frequency synthesizer accomplished by using a multiphase reference signal source, and more particularly, to a frequency synthesizer capable of generating a signal capable of provinding fine channel resolution, low phase noise, and rapid channel switching speed in system circuits.
2. Description of the Prior Art
With the increase on popularity of radio communication systems, the relevant key circuits are in great demand. In a mobile telephone system, a rapid synchronization between transmitting and receiving terminals is essential to channel building. However, due to the limitation of communication spectrum bandwidth, a break-through shall depend on a high performance frequency synthesizer, which can provide fine channel resolution and high quality output with low phase noise.
In order to achieve both the goals of fine channel resolution and rapid phase locking capability, the mechanism used for a conventional frequency synthesizer is a factional-N phase locked loop as shown in FIG.
1
. Wherever a phase locking state is achieved, the output signal F
0
and reference signal F
r
should satisfy eq. F
0
=N.f×F
r
, in which, the coefficient N.f of the fractional-N frequency divider is controlled by a &Sgr;-&Dgr; modulator. The digital frequency control signal X of the modulator is converted into an analog voltage signal and applied to a loop filter so as to control the voltage controlled oscillator (VCO) to output a predetermined frequency, and meanwhile, the quantization noise introduced by the digital/analog conversion is shifted to a higher frequency band by the &Sgr;-&Dgr; modulator and removed by the low-pass loop filter.
For eliminating cross talk between the reference signal and quantization noise smoothed out by the &Sgr;-&Dgr; modulator, system designers have to narrow the loop bandwidth of the phase locked loop to a value lower tan one tenth of reference signal frequency F
r
as well as the signal bandwidth of the &Sgr;-&Dgr; modulator. Such a consideration may reduce phase noise of the output signal and meanwhile increase phase locking time Therefore, to achieve the design goals of fine channel resolution, reduction of system noise, and rapid phase locking capability simultaneously has become an important issue in design consideration for a high performance frequency synthesizer.
SUMMARY OF THE INVENTION
In view of the room for improvement of the conventional frequency synthesizer circuits, the inventor of the present invention has engaged in relevant R&D constantly, and finally has the opportunity to disclose this invention of a frequency synthesizer circuit.
The invented frequency synthesizer circuit comprises
3
portions: (1) A basic phase locked loop including a variable frequency oscillator, a loop filter, a phase detector, and a frequency divider; (2) A Multiphase signal generator granged to produce a reference signal for the basic phase locked loop; and (3) A Frequency discriminator and phase modulator circuit.
The frequency synthesizer circuit of the present invention may, at the same time, address problems regarding fine channel resolution, reducing phase noise, etc, and furthermore reduce phase locking and frequency hopping time.
REFERENCES:
patent: 4965531 (1990-10-01), Riley
patent: 5889436 (1999-03-01), Yeung et al.
Maneatis et al., IEEE Journal of Solid-State Circuits, 28:1273-1282 (1993).
Wu et al., 1997 IEEE Int'l Solid-State Circuits Conf, SCC97, Sess. 5, 80-81, Communication Building Blocks I, Paper TP 5.2.
Candy, IEEE Translations on Communication, COM-33:249-258 (1985).
Riley et al., IEEE Journal of Solid-State Circuits, 28:553-559 (1993).
Chen Wer-Jen
Wu Jieh-Tsorng
Bacon & Thomas PLLC
Kinkead Arnold
National Science Council of Republic of China
LandOfFree
Frequency synthesizer accomplished by using multiphase... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Frequency synthesizer accomplished by using multiphase..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Frequency synthesizer accomplished by using multiphase... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2520419