JP2000013223A - Frequency synthesizer - Google Patents
Frequency synthesizerInfo
- Publication number
- JP2000013223A JP2000013223A JP10176440A JP17644098A JP2000013223A JP 2000013223 A JP2000013223 A JP 2000013223A JP 10176440 A JP10176440 A JP 10176440A JP 17644098 A JP17644098 A JP 17644098A JP 2000013223 A JP2000013223 A JP 2000013223A
- Authority
- JP
- Japan
- Prior art keywords
- frequency
- voltage
- piezoelectric
- output
- oscillators
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は周波数シンセサイザ
に関し、特に安価であり、耐熱及び、経年時特性に優
れ、更に、急激な温度変化に対する周波数安定度にも優
れた周波数シンセサイザに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency synthesizer, and more particularly to a frequency synthesizer which is inexpensive, has excellent heat resistance and aging characteristics, and also has excellent frequency stability against sudden temperature changes.
【０００２】[0002]
【従来の技術】周波数シンセサイザは高精度な周波数発
生装置としてこれまでに広く用いられてきており、特に
近年では、急速に発達している携帯電話等の移動体通信
システム端末には必要不可欠なものになっている。移動
体通信システム端末に用いられる周波数シンセサイザ
は、一般に図２に示すように誘電体の共振器を用いて数
百〜数十ＧＨｚの高周波を発生させる電圧制御発振器３
と、基準周波数源である温度補償型水晶発振器１０と、
前記電圧制御発振器３の出力周波数を分周する為の第一
の分周器１と、基準周波数を分周する為の分周器９と、
この分周器の出力である分周周波数同士を位相比較する
と共に、この位相差に応じた電圧を出力する位相比較器
８と、前記位相比較器の出力から高周波成分を除去し前
記電圧制御発振器３に制御電圧Ｖｃを供給する為の低域
通過フィルタ２とから構成される。以下に、動作につい
て説明する。電圧制御発振器３の出力周波数Ｆvcoを分
周器１により１／Ｎvcoに分周し、また、基準周波数源
１０の出力周波数Ｆrefを分周器９により１／Ｎrefに分
周する。このとき、分周器の分周比は予め設定した位相
比較周波数が出力されるよう決定される。また、位相比
較周波数は位相雑音等の必要な特性から通常は数ｋＨｚ
〜数十ｋＨｚに設定するのが一般的である。分周器より
出力された二つの位相比較周波数Ｆvco／Ｎvco とＦref
／Ｎref とを位相比較器８に入力すると、前記位相比較
器８は二つの位相比較周波数の位相差に応じて電圧を出
力し、この出力電圧を低域通過フィルタ２を介し前記電
圧制御発振器３の周波数制御部に供給する。該電圧制御
発振器３はこの制御電圧により出力周波数が基準周波数
に位相同期するよう徐々に制御され、基準周波数源と同
一の周波数安定度を有する出力周波数が得られる。以上
の説明からも明らかなように、周波数シンセサイザの出
力周波数の安定度は位相比較に用いる基準周波数源１０
の周波数安定度に依存する。この基準周波数源１０は必
要とする周波数安定度に応じて様々な種類のものが用い
られ、例えば携帯電話システムに於いては、移動端末機
にはＴＣＸＯ（温度補償型水晶発振器）が、基地局には
ＯＣＸＯ（恒温槽型水晶発振器）が用いられている。2. Description of the Related Art A frequency synthesizer has been widely used as a high-precision frequency generator, and is indispensable for a mobile communication system terminal such as a cellular phone which is rapidly developing in recent years. It has become. A frequency synthesizer used in a mobile communication system terminal generally includes a voltage controlled oscillator 3 that generates a high frequency of several hundreds to several tens GHz using a dielectric resonator as shown in FIG.
A temperature-compensated crystal oscillator 10 serving as a reference frequency source;
A first frequency divider 1 for dividing the output frequency of the voltage controlled oscillator 3, a frequency divider 9 for dividing the reference frequency,
A phase comparator for comparing phases of divided frequencies, which are outputs of the divider, and outputting a voltage corresponding to the phase difference; and a voltage-controlled oscillator for removing high-frequency components from the output of the phase comparator. 3 and a low-pass filter 2 for supplying a control voltage Vc to the low-pass filter 2. The operation will be described below. The output frequency F vco of the voltage controlled oscillator 3 is divided by the frequency divider 1 to 1 / N vco, and the output frequency F ref of the reference frequency source 10 is divided by the frequency divider 9 to 1 / N ref . At this time, the frequency division ratio of the frequency divider is determined so that a preset phase comparison frequency is output. The phase comparison frequency is usually several kHz due to necessary characteristics such as phase noise.
In general, it is set to 〜10 kHz. Two phase comparison frequencies F vco / N vco and F ref output from the frequency divider
/ N ref to the phase comparator 8, the phase comparator 8 outputs a voltage according to the phase difference between the two phase comparison frequencies, and outputs the output voltage via the low-pass filter 2 to the voltage-controlled oscillator. 3 to the frequency control unit. The voltage controlled oscillator 3 is gradually controlled by this control voltage so that the output frequency is phase-synchronized with the reference frequency, and an output frequency having the same frequency stability as the reference frequency source is obtained. As is clear from the above description, the stability of the output frequency of the frequency synthesizer depends on the reference frequency source 10 used for the phase comparison.
Frequency stability. Various types of reference frequency sources 10 are used depending on the required frequency stability. For example, in a mobile phone system, a mobile terminal includes a TCXO (Temperature Compensated Crystal Oscillator) and a base station. Uses an OCXO (Oven-controlled crystal oscillator).
【０００３】[0003]
【本発明が解決しようとする課題】しかしながら、前記
基準周波数源として用いられる水晶発振器は温度補償回
路或いは恒温槽装置と云った高価な付加回路が必要とな
ることはもちろんのこと温度変化に対する周波数安定度
を得る為に温度補償回路等の厳密な調整が必要となり調
整工数の増大によるコストアップを招くという問題があ
った。また、ＴＣＸＯは実装時のリフロー等による高熱
で周波数変化が起こり易く、周波数シンセサイザを構成
した後に再調整が必要となる場合があった。更に、ＴＣ
ＸＯを構成する水晶振動子の温度変化に対する周波数変
化と、温度補償回路の温度変化に対するコンダクタンス
値の変化との時定数が異なる為、急激な温度変化に対し
ＴＣＸＯの周波数安定化機能が追従できず、周波数シン
セサイザの出力周波数の安定度が悪化するという問題が
あった。However, the crystal oscillator used as the reference frequency source requires an expensive additional circuit such as a temperature compensating circuit or a thermostatic oven, and of course, requires a frequency stabilization circuit against temperature change. Therefore, strict adjustment of the temperature compensating circuit and the like is required in order to obtain a degree, and there is a problem that the cost is increased due to an increase in the number of adjustment steps. In addition, TCXO tends to change its frequency due to high heat due to reflow or the like at the time of mounting, and in some cases, readjustment is required after configuring a frequency synthesizer. Furthermore, TC
Since the time constant between the frequency change of the crystal oscillator constituting the XO with respect to the temperature change and the change of the conductance value with respect to the temperature change of the temperature compensation circuit is different, the frequency stabilizing function of the TCXO cannot follow the rapid temperature change. However, there is a problem that the stability of the output frequency of the frequency synthesizer is deteriorated.
【０００４】[0004]
【課題を解決するための手段】上記課題を解決する為
に、本発明に係わる周波数シンセサイザの請求項１記載
の発明は、基準周波数源の出力周波数と電圧制御発振器
の出力周波数とを位相比較手段に入力し、該位相比較手
段にて前記２つの周波数の位相差に応じた電圧を発生
し、該電圧を前記電圧制御発振器の制御電圧として供給
する周波数シンセサイザであって、前記基準周波数源と
して周波数温度特性がほぼ一致した２つの圧電発振器と
両者の出力周波数の差を出力する周波数差生成手段とを
用いたことを特徴とする。請求項２記載の発明は前記請
求項１記載の発明に加え、前記２つの圧電発振器を構成
する各圧電振動子が同一の圧電基板上に形成された２つ
の圧電振動子であることを特徴とする。請求項３記載の
発明は前記請求項１または請求項２記載の発明に加え、
前記圧電発振器がいずれもＡＴカット水晶発振器であ
り、前記周波数差生成手段を前記２つの発振器の出力を
入力するミキサ回路と該ミキサ回路の出力を入力するロ
ーパスフィルタとから構成したことを特徴とする。According to a first aspect of the present invention, there is provided a frequency synthesizer comprising: a phase comparator for comparing an output frequency of a reference frequency source with an output frequency of a voltage controlled oscillator; A frequency synthesizer for generating a voltage corresponding to the phase difference between the two frequencies by the phase comparing means and supplying the voltage as a control voltage of the voltage controlled oscillator, wherein a frequency is used as the reference frequency source. It is characterized in that two piezoelectric oscillators having substantially the same temperature characteristics and frequency difference generating means for outputting a difference between the output frequencies of the two are used. According to a second aspect of the present invention, in addition to the first aspect, each of the two piezoelectric vibrators constituting the two piezoelectric oscillators is two piezoelectric vibrators formed on the same piezoelectric substrate. I do. The invention according to claim 3 is the same as the invention according to claim 1 or 2,
Each of the piezoelectric oscillators is an AT-cut crystal oscillator, and the frequency difference generating means includes a mixer circuit for inputting the outputs of the two oscillators and a low-pass filter for inputting the outputs of the mixer circuits. .
【０００５】[0005]
【本発明の実施の形態】以下、図示した実施例に基づい
て本発明を詳細に説明する。図１は本発明を用いた周波
数シンセサイザの一実施例を示す回路図である。ここで
は特に、基準周波数源としてＴＣＸＯ相当の周波数安定
度が必要な場合について考える。従来の周波数シンセサ
イザと異なる点は、基準周波数源として二つの水晶発振
器４、５を用い、更に、基準周波数源からの位相比較周
波数を前記二つの水晶発振器４、５の出力周波数の差と
しているところにある。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a circuit diagram showing one embodiment of a frequency synthesizer using the present invention. Here, particularly, a case where a frequency stability equivalent to TCXO is required as a reference frequency source is considered. The difference from the conventional frequency synthesizer is that two crystal oscillators 4 and 5 are used as reference frequency sources, and the phase comparison frequency from the reference frequency source is the difference between the output frequencies of the two crystal oscillators 4 and 5. It is in.
【０００６】以下に構成について説明する。電圧制御発
振器３の出力周波数は分周器１により１／Ｎvcoに分周
され、前記分周器から出力される位相比較周波数Ｆvco
／Ｎvcoは位相比較器８に入力される。また、基準周波
数は基準周波数源４、５の各出力周波数Ｆ１とＦ２とを
ミキサー６に入力し、このミキサー６から出力する周波
数｜Ｆ１±Ｆ２｜を低域通過フィルタ７に入力する。低
域通過フィルタ７からは低域周波数である位相比較周波
数｜Ｆ１−Ｆ２｜が出力されこれを位相比較器８に入力
すると、該位相比較器８が位相比較周波数Ｆ vco／Ｎvco
と｜Ｆ１−Ｆ２｜との位相差に応じた電圧を出力し、低
域通過フィルタ２にて高周波ノイズを除去した後、電圧
制御発振器３の周波数制御部に制御電圧Ｖｃとして供給
される。以上の様な構成から成る周波数シンセサイザの
周波数安定度は二つの水晶発振器４、５それぞれの出力
周波数の差｜Ｆ１−Ｆ２｜の安定度に依存することにな
る。周知の通り、水晶発振器に用いられる水晶振動子
は、その切断角度によって共振周波数の温度特性が大き
く異なり、例えば、ＡＴカット水晶振動子の共振周波数
の温度特性３次関数で近似できることが知られている。
このような水晶振動子の周波数温度特性は水晶振動子の
製作偏差から個体差があるが、水晶の切断角度や加工等
の製作工程を管理することによりある範囲内に収まるこ
とが知られている。従ってこれら水晶振動子の周波数温
度特性がほぼ等しい水晶振動子を前記基準周波数源４、
５とに用いると、位相比較周波数｜Ｆ１−Ｆ２｜は温度
変化に対しほぼ一定の値となり、温度補償手段を用いる
ことなしにＴＣＸＯと同等の温度に対する周波数安定度
が得られることになる。また、水晶振動子の共振周波数
は高熱や経時により変化することが前述した通りである
が、同一環境下に於いては、この変化量や変化方向は水
晶振動子の製作ロットが同一であればほぼ同一傾向とな
るのが一般的であり、前記基準周波数源４、５に使用す
る振動子を同一の製作ロットから選択することで、位相
比較周波数｜Ｆ１−Ｆ２｜はこれら周波数変化をも吸収
できる。更に、周波数の異なる２つの振動子を同一の水
晶基板上に形成することにより両者の周波数温度特性の
差異はほぼ等しくなり、温度変化に対する周波数変化を
一定にする上で有効である。この場合、励振周波数の異
なる前記２つの振動子を得る為に該振動子の電極膜厚は
それぞれ異なる厚さとすればよい。The configuration will be described below. Voltage control source
The output frequency of the oscillator 3 is 1 / N by the frequency divider 1.vcoDivided into
And the phase comparison frequency F output from the frequency dividervco
/ NvcoIs input to the phase comparator 8. Also, the reference frequency
The numbers correspond to the output frequencies F1 and F2 of the reference frequency sources 4 and 5, respectively.
Frequency input to mixer 6 and output from mixer 6
The number | F1 ± F2 | is input to the low-pass filter 7. Low
From the bandpass filter 7, a phase comparison frequency which is a low frequency
The number | F1-F2 | is output and input to the phase comparator 8.
Then, the phase comparator 8 sets the phase comparison frequency F vco/ Nvco
And a voltage corresponding to the phase difference between | F1-F2 |
After removing high-frequency noise with the bandpass filter 2, the voltage
Supply as control voltage Vc to frequency control unit of control oscillator 3
Is done. The frequency synthesizer with the above configuration
The frequency stability is the output of each of the two crystal oscillators 4, 5.
Will depend on the stability of the frequency difference | F1-F2 |.
You. As is well known, crystal oscillators used in crystal oscillators
Has a large temperature characteristic of the resonance frequency depending on the cutting angle.
For example, the resonance frequency of an AT-cut quartz resonator
It is known that the temperature characteristic can be approximated by a cubic function.
The frequency-temperature characteristics of such a crystal resonator
Although there are individual differences due to manufacturing deviations, the cutting angle and processing of quartz, etc.
By controlling the manufacturing process of
And is known. Therefore, the frequency temperature of these crystal units
The crystal oscillators having substantially the same degree characteristics are referred to as the reference frequency source 4,
5, the phase comparison frequency | F1-F2 |
Almost constant value against change, use temperature compensation means
Frequency stability at the same temperature as TCXO without any problem
Is obtained. Also, the resonance frequency of the crystal unit
Changes as a result of high heat and aging, as described above.
However, under the same environment, the amount and direction of this change
If the production lots of crystal units are the same, the tendency is almost the same.
Generally, the reference frequency sources 4 and 5 are used.
Phase by selecting the same transducer from the same production lot.
The comparison frequency | F1-F2 | also absorbs these frequency changes
it can. Furthermore, two vibrators having different frequencies are connected to the same water.
Of the frequency-temperature characteristics of both
The difference is almost equal, and the frequency change with temperature change
It is effective in making it constant. In this case, the excitation frequency
In order to obtain the above two vibrators, the electrode thickness of the vibrator is
The thickness may be different from each other.
【０００７】以上、本発明を水晶発振器を例に説明した
が、本発明はこれに限定されるものではなく、水晶以外
の圧電材料として例えばニオブ酸リチュウムやタンタル
酸リチュウム等からなる振動子を用いて圧電発振器を構
成した場合であっても、一実施例と同一の機能が得られ
ることは言うまでもない。Although the present invention has been described with reference to a quartz oscillator as an example, the present invention is not limited to this. For example, a vibrator made of, for example, lithium niobate or lithium tantalate is used as a piezoelectric material other than quartz. Needless to say, even when a piezoelectric oscillator is configured, the same function as that of the embodiment can be obtained.
【０００８】[0008]
【本発明の効果】以上説明したように請求項１記載の発
明は基準周波数源からの位相比較周波数を二つの圧電発
振器の出力周波数の差としており、また、これら圧電発
振器は温度補償回路を備えていない為、部品点数が少な
く、更に、調整工数が必要ない為、価格的に安価なもの
になる。また、二つの圧電発振器４、５とに使用する水
晶振動子を同一製造ロットとすることにより周波数シン
セサイザの出力周波数は高熱及び、経時による安定度が
向上する。As described above, the first aspect of the present invention uses the phase comparison frequency from the reference frequency source as the difference between the output frequencies of the two piezoelectric oscillators, and these piezoelectric oscillators have a temperature compensation circuit. Since the number of components is small, the number of adjustment steps is not required, and the cost is low. Also, by using the same manufacturing lot for the crystal units used for the two piezoelectric oscillators 4 and 5, the output frequency of the frequency synthesizer is increased in heat and the stability over time is improved.
【図１】本発明に基づく周波数シンセサイザの一実施例
のブロック回路図を示すものである。FIG. 1 shows a block circuit diagram of an embodiment of a frequency synthesizer according to the present invention.
【図２】従来の周波数シンセサイザのブロック回路図を
示すものである。FIG. 2 is a block circuit diagram of a conventional frequency synthesizer.
１、９・・・分周器 ２、７・・低域通過フィルタ ３・・・・電圧制御発振器 ４、５・・水晶発振器 ６・・・・ミキサー ８・・・・位相比較器 １０・・・温度補償が水晶発振器 1, 9 frequency divider 2, 7 low pass filter 3 voltage controlled oscillator 4, 5 crystal oscillator 6 mixer 8 phase comparator 10・ Temperature compensation is crystal oscillator
Claims (3)
器の出力周波数とを位相比較手段に入力し、該位相比較
手段にて前記２つの周波数の位相差に応じた電圧を発生
し、該電圧を前記電圧制御発振器の制御電圧として供給
する周波数シンセサイザであって、前記基準周波数源と
して周波数温度特性がほぼ一致した２つの圧電発振器と
両者の出力周波数の差を出力する周波数差生成手段とを
用いたことを特徴とする周波数シンセサイザ。An output frequency of a reference frequency source and an output frequency of a voltage controlled oscillator are input to a phase comparing means, and a voltage corresponding to a phase difference between the two frequencies is generated by the phase comparing means. As a control voltage of the voltage-controlled oscillator, using two piezoelectric oscillators having substantially the same frequency-temperature characteristics as the reference frequency source and frequency difference generating means for outputting the difference between the output frequencies of the two piezoelectric oscillators. A frequency synthesizer.
動子が同一の圧電基板上に形成された２つの圧電振動子
であることを特徴とする請求項１記載の周波数シンセサ
イザ。2. The frequency synthesizer according to claim 1, wherein each of the piezoelectric vibrators constituting the two piezoelectric oscillators is two piezoelectric vibrators formed on the same piezoelectric substrate.
発振器であり、前記周波数差生成手段を前記２つの発振
器の出力を入力するミキサ回路と該ミキサ回路の出力を
入力するローパスフィルタとから構成したことを特徴と
する請求項１または請求項２記載の周波数シンセサイ
ザ。3. The piezoelectric oscillator is an AT-cut crystal oscillator, and the frequency difference generating means comprises a mixer circuit for inputting the outputs of the two oscillators and a low-pass filter for inputting the outputs of the mixer circuits. 3. The frequency synthesizer according to claim 1, wherein:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10176440A JP2000013223A (en) | 1998-06-23 | 1998-06-23 | Frequency synthesizer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10176440A JP2000013223A (en) | 1998-06-23 | 1998-06-23 | Frequency synthesizer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000013223A true JP2000013223A (en) | 2000-01-14 |
Family
ID=16013752
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10176440A Pending JP2000013223A (en) | 1998-06-23 | 1998-06-23 | Frequency synthesizer |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2000013223A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1136659A2 (en) | 2000-01-21 | 2001-09-26 | Nissan Motor Co., Ltd. | Apparatus and method for controlling position of electromagnetically operated engine valve of internal combustion engine |
-
1998
- 1998-06-23 JP JP10176440A patent/JP2000013223A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1136659A2 (en) | 2000-01-21 | 2001-09-26 | Nissan Motor Co., Ltd. | Apparatus and method for controlling position of electromagnetically operated engine valve of internal combustion engine |
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