JP4277154B2 - Voltage controlled oscillator and synthesizer receiver - Google Patents

Description

となる。
【００２１】
したがって、受信バンドおよび受信地域に対応して基準周波数ｆREFおよび分 周比Ｎ25、Ｎを、例えば図３に示すように、変更すれば、受信周波数範囲および周波数ステップは、図３に示すようになる。したがって、それぞれの地域において、目的とするＡＭ放送の周波数に対応して基準周波数ｆREFおよび分周比Ｎ、 Ｎ25を変更ないし制御すれば、そのＡＭ放送を受信することができる。
【００２２】
例えば、日本で中波放送を受信する場合であれば、Ｎ25＝20、ｆREF＝20ｋHz に設定するとともに、分周比Ｎを11222〜12329の間で９おきに変更すればよく、このとき、周波数522ｋHz〜1629ｋHzの範囲を９ｋHzステップで受信することが できる。
【００２３】
そして、基準周波数ｆREFおよび分周比Ｎ25、Ｎを、例えば図３に示すように 変更するため、受信機１０には、マイクロコンピュータ３１が設けられる。そして、このマイクロコンピュータ３１には、各種の操作キー（操作スイッチ）３２および設定スイッチ３３が接続され、マイクロコンピュータ３１から可変分周回路２２に分周比Ｎが供給され、可変分周回路２５に分周比Ｎ25の制御信号が供給されるとともに、可変分周回路２７に分周比の制御信号が供給される。
【００２４】
そして、キー３２を操作すると、マイクロコンピュータ３１により、その操作されたキーおよび設定スイッチ３３に対応して分周回路２２、２５の分周比Ｎ、Ｎ25が変更されるとともに、分周回路２７の分周比が制御されて基準周波数ｆREFが変更され、この結果、受信周波数ｆRXが(5)式にしたがって変更される。
【００２５】
こうして、受信機１０においては、例えば図３に示すような受信周波数範囲および周波数ステップでＡＭ放送を受信することができる。
【００２６】
そして、この場合、ＶＣＯ２１の発振周波数ｆVCOは、図３にも示すように、 その変化範囲が広いので、ＶＣＯ２１は、例えば図２に示すように構成される。すなわち、図２において、ＶＣＯ２１は、発振回路２１Ａと、その発振周波数ｆVCOを決定する共振回路２１Ｂとに分割される。そして、発振回路２１ＡはＩＣ ４０にＩＣ化されるとともに、ＩＣ４０は、外部に共振回路２１Ｂを接続するための接続端子（外部接続ピン）ＴX1、ＴX2を有する。なお、ＩＣ４０には、上述した受信機１０の回路１２〜１７、２０の少なくとも一部も一体にＩＣされている。
【００２７】
そして、端子ＴX1と接地との間に、直流カット用のコンデンサＣ11と、共振用コイルＬ11とが直列接続され、端子ＴX2と接地との間に、直流カット用のコンデンサＣ12と、可変容量ダイオードＤ11と、直流カット用のコンデンサＣ13とが直列接続される。また、素子Ｃ11、Ｌ11の接続中点と、素子Ｃ12、Ｄ11の接続中点とが接続されるとともに、この接続中点と、接地との間に、スイッチ用のＰＩＮ接合ダイオードＤ12と、共振用の補助のコイルＬ12と、直流カット用のコンデンサＣ14とが直列接続される。こうして、共振回路２１Ｂが構成される。
【００２８】
さらに、マイクロコンピュータ３１から、所定の制御電圧Ｖ31が取り出され、この制御電圧Ｖ31が、バッファ用のアンプ３４および抵抗器Ｒ11を通じて素子Ｌ12、Ｃ14の接続中点に供給される。また、ローパスフィルタ２４の出力電圧、すなわち、選局電圧ＶTNが、バッファ用の抵抗器Ｒ12を通じて素子Ｄ11、Ｃ13の接続中点に供給される。この場合、制御電圧Ｖ31は、受信周波数範囲に対応して、例えば図３に示すように、“Ｈ”レベルあるいは“Ｌ”レベルに変化するものである。
【００２９】
なお、一例として、
可変容量ダイオードＤ11の容量：８pＦ〜19pＦ（ＶTN＝６〜１Ｖのとき）
コイルＬ11のインダクタンス ：50nＨ
コイルＬ12のインダクタンス ：33nＨ
制御電圧Ｖ31の“Ｈ”レベル ：8.5Ｖ
制御電圧Ｖ31の“Ｌ”レベル ：０Ｖ
である。
【００３０】
このような構成によれば、制御電圧Ｖ31が、バッファアンプ３４および抵抗器Ｒ 11→コイルＬ12→ダイオードＤ12→コイルＬ11→接地のラインを通じてダイオードＤ12に印加される。
【００３１】
したがって、Ｖ31＝“Ｌ”のときには、ダイオードＤ12への印加電圧（端子電圧）は０Ｖであり、ダイオードＤ12はオフであるから、コイルＬ11および可変容量ダイオードＤ11が高周波的に並列接続され、その並列回路がＶＣＯ２１の共振回路２１Ｂとして作用する。
【００３２】
そして、このとき、ローパスフィルタ２４から出力される選局電圧ＶTNが、抵抗器Ｒ12→可変容量ダイオードＤ11→コイルＬ11→接地のラインを通じて可変容量ダイオードＤ11に供給されるので、可変容量ダイオードＤ11の容量は、選局電圧ＶTNに対応して変化する。したがって、ＶＣＯの発振周波数ｆVCOは、図３の うち、Ｖ31＝“Ｌ”の欄に示すように、変化することができる。
【００３３】
一方、Ｖ31＝“Ｈ”のときには、この電圧Ｖ31がダイオードＤ12に印加されるので、ダイオードＤ12はオンとなり、コイルＬ12がコイルＬ11に高周波的に並列接続される。したがって、これらコイルＬ11、Ｌ12および可変容量ダイオードＤ11の並列回路がＶＣＯ２１の共振回路２１Ｂとして作用する。
【００３４】
そして、このとき、ローパスフィルタ２４から出力される選局電圧ＶTNが、抵抗器Ｒ12→可変容量ダイオードＤ11→コイルＬ11→接地のラインを通じて可変容量ダイオードＤ11に供給されるので、可変容量ダイオードＤ11の容量は、選局電圧ＶTNに対応して変化する。
【００３５】
ただし、このとき、コイルＬ11、Ｌ12および可変容量ダイオードＤ11による共振回路２１Ｂの共振周波数は、コイルＬ12が並列接続されたことにより、並列接続されていないとき（Ｖ31＝“Ｌ”のとき）に比べて、高くなっている。したがって、ＶＣＯの発振周波数ｆVCOは、図３のうち、Ｖ31＝“Ｈ”の欄に示すよう に、変化することができる。
【００３６】
こうして、図２のＶＣＯ２１によれば、広い周波数範囲にわたる局部発振信号ＳLO1を形成することができる。そして、そのとき、電源電圧を高くする必要が なく、したがって、車載用の受信機や電池で動作する受信機などの場合に、ＤＣ／ＤＣコンバータを設けて電源電圧を昇圧する必要がないので、受信機の価格の上がることがない。
【００３７】
また、可変容量ダイオードＤ11として、選局電圧に対する容量変化の大きいものを使用する必要がないので、発振信号ＳVCOのＣ／Ｎの悪化することがなく、 したがって、オーディオ信号のＳ／Ｎが悪化することがない。
【００３８】
さらに、単一の制御電圧Ｖ31で発振周波数ｆVCOの変化範囲を変更することが できる。また、この制御電圧Ｖ31が発振回路２１Ａに印加されることがないので、発振信号ＳVCOを常に安定に得ることができるとともに、スイッチ用のダイオ ードＤ12を確実にオンあるいはオフに制御することができる。
【００３９】
〔この明細書で使用している略語の一覧〕
ＡＭ ：Amplitude Modulation；振幅変調
Ｃ／Ｎ ：Carrier to Noise ratio；ＣＮ比
ＤＣ／ＤＣ：Direct Current to Direct Current
ＩＣ ：Integrated Circuit；集積回路
ｋHz ：kiloHertz
ＭHz ：MegaHertz
nＨ ：nanoHenry
pＦ ：picoFarad
ＰＩＮ ：Positive-Intrinsic-Negative
ＰＬＬ ：Phase Locked Loop；位相同期ループ
Ｓ／Ｎ ：Signal to Noise ratio；ＳＮ比
Ｖ ：Volt
ＶＣＯ ：Voltage Controlled Oscillator；電圧制御発振器
【００４０】
【発明の効果】
この発明によれば、広い周波数範囲にわたる発振信号を形成することができる。そして、そのとき、電源電圧を高くする必要がないので、価格の上昇を抑えることができる。また、可変容量ダイオードとして、選局電圧に対する容量変化の大きいものを使用する必要がないので、オーディオ信号のＳ／Ｎが悪化することがない。
【００４１】
さらに、単一の制御電圧で発振周波数の変化範囲を変更することができる。また、この制御電圧が発振回路に印加されることがないので、発振信号を常に安定に得ることができるとともに、スイッチ用のダイオードを確実にオンあるいはオフに制御することができる。
【図面の簡単な説明】
【図１】この発明の一形態を示す系統図である。
【図２】この発明の一形態を示す接続図である。
【図３】この発明を説明するための図である。
【図４】この発明を説明するための接続図である。
【符号の説明】
１１…アンテナ、１２…高周波アンプ、１３…第１ミキサ回路、１４…第１中間周波回路、１５…第２ミキサ回路、１６…第２中間周波回路、１７…ＡＭ検波回路、１８…出力端子、２０…ＰＬＬ、２１…ＶＣＯ、２１Ａ…発振回路、２１Ｂ…共振回路、２２…可変分周回路、２３…位相比較回路、２４…ローパスフィルタ、２５…可変分周回路、２６…発振回路、２７…可変分周回路、２８…分周回路、３１…マイクロコンピュータ、３２…操作キー、３３…設定スイッチ、３４…バッファアンプ、４０…ＩＣ、Ｃ11〜Ｃ14…直流カット用コンデンサ、Ｄ11…可変容量ダイオード、Ｄ12…スイッチ用ダイオード、Ｌ11およびＬ12…共振用コイル、Ｒ11およびＲ12…バッファ抵抗器、ＴX1およびＴX2…外部接続ピン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage controlled oscillator and a synthesizer receiver.
[0002]
[Prior art]
In a synthesizer type superheterodyne receiver, a received signal having a target frequency is converted into an intermediate frequency signal by an oscillation signal of a PLL VCO (voltage controlled oscillator).
[0003]
Therefore, when AM broadcasting (including communications other than broadcasting) can be received over a frequency range of 153 kHz to 18.135 MHz as shown in FIG. 3 for example, the oscillation frequency of the VCO corresponds to the reception frequency range. And must be able to vary over a fairly wide range.
[0004]
Then, as a method of widening the oscillation frequency range of the VCO, when supplying a tuning voltage (tuning voltage) to the variable capacitance diode of the resonance circuit of the VCO,
(1) Increase the upper limit (change range) of the tuning voltage.
(2) Use a variable capacitance diode that has a large capacitance change with respect to the tuning voltage.
The method is common. Also,
(3) The coil of the resonance circuit of the VCO is switched corresponding to the reception band.
A method is also considered.
[0005]
Here, FIG. 4 shows an example of a VCO employing the method of item (3). The oscillation circuit is configured in a Colpitts type by the transistor Qa, and coils La and Lb and variable capacitance diodes are used as the resonance circuit. Da is connected.
[0006]
When VL = “H” level and VH = “L” level, the switching diode Db is reverse-biased and turned off, so that the coil Lb is connected in series with the coil La, and therefore the inductance of the resonance circuit increases. Therefore, oscillation is possible in a low frequency band.
[0007]
Further, when VL = “L” level and VH = “H” level, the switching diode Db is turned on, so that the coil Lb is short-circuited at high frequency by this diode Db, and therefore the inductance of the resonance circuit is reduced. It becomes possible to oscillate in a high frequency band.
[0008]
In each frequency band, when the tuning voltage VT is changed, the capacitance of the variable capacitance diode Da is changed, so that the oscillation frequency is changed. Therefore, for example, an oscillation signal necessary for the reception frequency range as shown in FIG. 3 can be formed.
[0009]
[Problems to be solved by the invention]
However, in the case of the method of item (1), since it is necessary to increase the power supply voltage, in the case of a vehicle-mounted receiver or a battery-operated receiver, a DC / DC converter is provided and the power supply voltage is increased. This increases the price of the receiver.
[0010]
In the case of method (2), the C / N of the oscillation signal is deteriorated, and as a result, the S / N of the demodulated audio signal is deteriorated.
[0011]
Further, in the case of the VCO of the item (3), since the band switching control voltages VL and VH are also applied to the oscillation transistor Qa, the oscillation condition of the transistor Qa becomes severe.
[0012]
The present invention is intended to solve the above problems.
[0013]
[Means for Solving the Problems]
In this invention,
An oscillation circuit;
A resonance circuit that determines the oscillation frequency of the oscillation circuit;
Have
The oscillation circuit is
First and second terminals for connecting the resonant circuit
Have
The resonant circuit is
A first DC cutting capacitor and a first resonance coil are connected in series between the first terminal and the ground,
Between the second terminal and the ground, a second DC cut capacitor, a variable capacitance diode, and a third DC cut capacitor are connected in series.
The connection midpoint of the first DC cut capacitor and the first resonance coil is connected to the connection midpoint of the second DC cut capacitor and the variable capacitance diode, and
Between the midpoint of connection and the ground, a switching diode, a resonance auxiliary coil, and a fourth DC cut capacitor are connected in series.
A first control voltage is supplied to a connection midpoint between the auxiliary coil and the fourth DC cut capacitor through a first buffer circuit,
A second control voltage is supplied to a connection midpoint between the variable capacitance diode and the third DC cut capacitor through a second buffer circuit,
By switching the first control voltage, the switching diode is turned on and off to switch the oscillation frequency range of the oscillation circuit, and
By changing the second control voltage, the capacitance of the variable capacitance diode is changed to change the oscillation frequency in the oscillation frequency range.
Voltage controlled oscillator
It is what.
In addition, a synthesizer receiver in which such a voltage controlled oscillator is applied to a local oscillation circuit is provided.
Therefore, the reception frequency range is switched by on / off control of the switch element, and the reception frequency is changed in the reception frequency range switched by changing the frequency division ratio of the variable frequency dividing circuit.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, reference numeral 10 denotes an AM receiver configured in a synthesizer system and a double superheterodyne system. In this example, the reception band, reception frequency range, and frequency step are as shown in FIG.
[0015]
Then, the reception signal from the antenna 11 is supplied to the first mixer circuit 13 through the high frequency amplifier 12, and the frequency fLO1 from the variable frequency dividing circuit 25 is, for example,
fLO1 = fRX + fIF1 (1)
fRX: Transmission frequency of the intended reception signal SRX fIF1: First intermediate frequency. For example, fIF1 = 10.7MHz
Frequency signal SLO1 is extracted, this signal SLO1 is supplied to the mixer circuit 13 as a first local oscillation signal, and the intended received signal SRX is frequency-converted to a first intermediate frequency signal SIF1 (first intermediate frequency fIF1). The
[0016]
Subsequently, the first intermediate frequency signal SIF1 is supplied to the second mixer circuit 15 through, for example, a first intermediate frequency circuit 14 configured by cascading ceramic filters and amplifiers, and the frequency from the frequency divider circuit 28 is also supplied. For example, fLO2 is
fLO2 = fIF1-fIF2 (2)
fIF2: second intermediate frequency. For example, fIF2 = 450kHz
Frequency division signal SLO2 is extracted, this signal SLO2 is supplied to the mixer circuit 15 as a second local oscillation signal, and the signal SIF1 is frequency-converted to a second intermediate frequency signal SIF2 (second intermediate frequency fIF2). Then, the second intermediate frequency signal SIF2 is supplied to the AM detection circuit 17 through the second intermediate frequency circuit 16, and the audio signal is demodulated, and this audio signal is taken out to the terminal 18.
[0017]
At this time, the PLL 21 is configured by the circuits 21 to 27. That is, an oscillation signal SVCO having a frequency fVCO is extracted from the VCO 21, this signal SVCO is supplied to the variable frequency dividing circuit 22, and is divided by a frequency of 1 / N, and this frequency divided signal is supplied to the phase comparison circuit 23. . At this time, an oscillation signal having a stable frequency is taken out from the crystal oscillation circuit 26, and this oscillation signal is supplied to the variable frequency dividing circuit 27 and divided into a signal having the reference frequency fREF. 23 is supplied as a reference signal.
[0018]
The comparison output of the comparison circuit 23 is supplied to the low-pass filter 24, and the output voltage is supplied to the VCO 21 as its control voltage (tuning voltage). Further, the oscillation signal SVCO of the VCO 21 is supplied to the variable frequency dividing circuit 25 and is divided to a frequency of 1 / N25, and this frequency divided signal is supplied to the mixer circuit 13 as the first local oscillation signal SLO1 as described above. Is done. Further, the oscillation signal of the oscillation circuit 26 is supplied to the frequency dividing circuit 28 to form the second local oscillation signal SLO2.
[0019]
Therefore, in the steady state, the frequency of the frequency-divided signal from the variable frequency dividing circuit 22 and the frequency fREF of the frequency-divided signal from the frequency dividing circuit 27 are equal to each other. Therefore, the oscillation frequency fVCO of the oscillation signal SVCO at this time Is
fVCO = N × fREF (3)
It becomes. At this time, fLO1 = fVCO / N25 (4) by the frequency dividing circuit 25.
It is.
[0020]
As a result, from equations (1), (3), (4)

It becomes.
[0021]
Therefore, if the reference frequency fREF and the frequency division ratios N25 and N are changed corresponding to the reception band and the reception area as shown in FIG. 3, for example, the reception frequency range and frequency step are as shown in FIG. . Accordingly, in each area, if the reference frequency fREF and the frequency division ratios N and N25 are changed or controlled corresponding to the frequency of the target AM broadcast, the AM broadcast can be received.
[0022]
For example, in the case of receiving medium-wave broadcasting in Japan, N25 = 20 and fREF = 20 kHz may be set, and the division ratio N may be changed every 9 between 11222-12329. The range from 522 kHz to 1629 kHz can be received in 9 kHz steps.
[0023]
In order to change the reference frequency fREF and the frequency division ratios N25 and N as shown in FIG. 3, for example, the receiver 10 is provided with a microcomputer 31. Various operation keys (operation switches) 32 and a setting switch 33 are connected to the microcomputer 31, and a frequency division ratio N is supplied from the microcomputer 31 to the variable frequency dividing circuit 22. A control signal of the frequency division ratio N25 is supplied, and a control signal of the frequency division ratio is supplied to the variable frequency dividing circuit 27.
[0024]
When the key 32 is operated, the microcomputer 31 changes the frequency dividing ratios N and N25 of the frequency dividing circuits 22 and 25 corresponding to the operated key and the setting switch 33, and the frequency dividing circuit 27 The frequency division ratio is controlled to change the reference frequency fREF, and as a result, the reception frequency fRX is changed according to the equation (5).
[0025]
Thus, the receiver 10 can receive AM broadcasts in a reception frequency range and frequency step as shown in FIG. 3, for example.
[0026]
In this case, since the variation range of the oscillation frequency fVCO of the VCO 21 is wide as shown in FIG. 3, the VCO 21 is configured as shown in FIG. 2, for example. That is, in FIG. 2, the VCO 21 is divided into an oscillation circuit 21A and a resonance circuit 21B that determines its oscillation frequency fVCO. The oscillation circuit 21A is integrated into an IC 40, and the IC 40 has connection terminals (external connection pins) TX1 and TX2 for connecting the resonance circuit 21B to the outside. It should be noted that at least a part of the circuits 12 to 17 and 20 of the receiver 10 described above is integrated with the IC 40.
[0027]
A DC cut capacitor C11 and a resonance coil L11 are connected in series between the terminal TX1 and the ground, and a DC cut capacitor C12 and a variable capacitance diode D11 are connected between the terminal TX2 and the ground. And a DC cut capacitor C13 are connected in series. Further, the connection midpoint of the elements C11 and L11 and the connection midpoint of the elements C12 and D11 are connected, and the PIN junction diode D12 for switching and the resonance are connected between the connection midpoint and the ground. The auxiliary coil L12 and a DC cut capacitor C14 are connected in series. Thus, the resonance circuit 21B is configured.
[0028]
Further, a predetermined control voltage V31 is taken out from the microcomputer 31, and this control voltage V31 is supplied to the connection midpoint of the elements L12 and C14 through the buffer amplifier 34 and the resistor R11. The output voltage of the low-pass filter 24, that is, the tuning voltage VTN is supplied to the connection midpoint of the elements D11 and C13 through the buffer resistor R12. In this case, the control voltage V31 changes to “H” level or “L” level as shown in FIG. 3 , for example, corresponding to the reception frequency range.
[0029]
As an example,
Capacitance of the variable capacitance diode D11: 8 pF to 19 pF (when VTN = 6 to 1 V)
Inductance of coil L11: 50nH
Inductance of coil L12: 33nH
“H” level of control voltage V31: 8.5V
"L" level of control voltage V31: 0V
It is.
[0030]
According to such a configuration, the control voltage V31 is applied to the diode D12 through the buffer amplifier 34 and resistor R 11 → coil L12 → diode D12 → coil L11 → ground line.
[0031]
Therefore, when V31 = “L”, the voltage (terminal voltage) applied to the diode D12 is 0V, and the diode D12 is off, so that the coil L11 and the variable capacitance diode D11 are connected in parallel at high frequency. The circuit acts as a resonant circuit 21B for the VCO 21.
[0032]
At this time, the channel selection voltage VTN output from the low-pass filter 24 is supplied to the variable capacitance diode D11 through the resistor R12 → variable capacitance diode D11 → coil L11 → ground line, and therefore the capacitance of the variable capacitance diode D11. Changes corresponding to the tuning voltage VTN. Therefore, the oscillation frequency fVCO of the VCO can be changed as shown in the column of V31 = “L” in FIG.
[0033]
On the other hand, when V31 = "H", the voltage V31 is applied to the diode D12, so that the diode D12 is turned on and the coil L12 is connected in parallel to the coil L11 in high frequency. Therefore, a parallel circuit of the coils L11 and L12 and the variable capacitance diode D11 functions as the resonance circuit 21B of the VCO 21.
[0034]
At this time, the channel selection voltage VTN output from the low-pass filter 24 is supplied to the variable capacitance diode D11 through the resistor R12 → variable capacitance diode D11 → coil L11 → ground line, and therefore the capacitance of the variable capacitance diode D11. Changes corresponding to the tuning voltage VTN.
[0035]
However, at this time, the resonance frequency of the resonance circuit 21B by the coils L11 and L12 and the variable capacitance diode D11 is compared with the resonance frequency when the coil L12 is not connected in parallel because the coil L12 is connected in parallel (when V31 = “L”). It is getting higher. Therefore, the oscillation frequency fVCO of the VCO can be changed as shown in the column of V31 = “H” in FIG.
[0036]
Thus, according to the VCO 21 of FIG. 2, the local oscillation signal SLO1 over a wide frequency range can be formed. And at that time, there is no need to increase the power supply voltage. Therefore, in the case of a vehicle-mounted receiver or a battery-operated receiver, it is not necessary to provide a DC / DC converter to boost the power supply voltage. The price of the receiver never increases.
[0037]
Further, since it is not necessary to use the variable capacitance diode D11 having a large capacitance change with respect to the tuning voltage, the C / N of the oscillation signal SVCO does not deteriorate, and therefore the S / N of the audio signal deteriorates. There is nothing.
[0038]
Further, the change range of the oscillation frequency fVCO can be changed with a single control voltage V31. Further, since the control voltage V31 is not applied to the oscillation circuit 21A, the oscillation signal SVCO can always be obtained stably, and the switching diode D12 can be reliably controlled to be turned on or off. it can.
[0039]
[List of abbreviations used in this specification]
AM: Amplitude Modulation; A / C modulation: Carrier to Noise ratio; CN ratio DC / DC: Direct Current to Direct Current
IC: Integrated Circuit; integrated circuit kHz: kiloHertz
MHz: MegaHertz
nH: nanoHenry
pF: picoFarad
PIN: Positive-Intrinsic-Negative
PLL: Phase Locked Loop; Phase-locked loop S / N: Signal to Noise ratio; SN ratio V: Volt
VCO: Voltage Controlled Oscillator
【The invention's effect】
According to the present invention, an oscillation signal over a wide frequency range can be formed. At that time, since it is not necessary to increase the power supply voltage, an increase in price can be suppressed. Further, since it is not necessary to use a variable capacitance diode having a large capacitance change with respect to the tuning voltage, the S / N of the audio signal does not deteriorate.
[0041]
Furthermore, the change range of the oscillation frequency can be changed with a single control voltage. In addition, since this control voltage is not applied to the oscillation circuit, the oscillation signal can be always obtained stably and the switching diode can be reliably controlled to be turned on or off.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of the present invention.
FIG. 2 is a connection diagram illustrating one embodiment of the present invention.
FIG. 3 is a diagram for explaining the present invention.
FIG. 4 is a connection diagram for explaining the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Antenna, 12 ... High frequency amplifier, 13 ... 1st mixer circuit, 14 ... 1st intermediate frequency circuit, 15 ... 2nd mixer circuit, 16 ... 2nd intermediate frequency circuit, 17 ... AM detection circuit, 18 ... Output terminal, 20 ... PLL, 21 ... VCO, 21A ... oscillation circuit, 21B ... resonance circuit, 22 ... variable frequency dividing circuit, 23 ... phase comparison circuit, 24 ... low pass filter, 25 ... variable frequency dividing circuit, 26 ... oscillation circuit, 27 ... Variable frequency dividing circuit, 28 ... frequency dividing circuit, 31 ... microcomputer, 32 ... operation key, 33 ... setting switch, 34 ... buffer amplifier, 40 ... IC, C11 to C14 ... DC cut capacitor, D11 ... variable capacitance diode, D12 ... Switch diode, L11 and L12 ... Resonance coil, R11 and R12 ... Buffer resistor, TX1 and TX2 ... External connection pins

Claims (2)

An oscillation circuit;
A resonance circuit that determines the oscillation frequency of the oscillation circuit;
The oscillation circuit is
First and second terminals for connecting the resonant circuit
Have
The resonant circuit is
A first DC cutting capacitor and a first resonance coil are connected in series between the first terminal and the ground,
Between the second terminal and the ground, a second DC cut capacitor, a variable capacitance diode, and a third DC cut capacitor are connected in series.
The connection midpoint of the first DC cut capacitor and the first resonance coil is connected to the connection midpoint of the second DC cut capacitor and the variable capacitance diode, and
Between the midpoint of connection and the ground, a switching diode, a resonance auxiliary coil, and a fourth DC cut capacitor are connected in series.
A first control voltage is supplied to a connection midpoint between the auxiliary coil and the fourth DC cut capacitor through a first buffer circuit,
A second control voltage is supplied to a connection midpoint between the variable capacitance diode and the third DC cut capacitor through a second buffer circuit,
By switching the first control voltage, the switching diode is turned on and off to switch the oscillation frequency range of the oscillation circuit, and
A voltage controlled oscillator configured to change an oscillation frequency in the oscillation frequency range by changing a capacitance of the variable capacitance diode by changing the second control voltage . Configured cie synthesizer receiver to change the reception frequency by changing the local oscillation frequency by changing the frequency division ratio of the variable frequency dividing circuit in PLL,
The voltage controlled oscillator of the PLL is
An oscillation circuit;
A resonance circuit that determines the oscillation frequency of the oscillation circuit, and
The oscillation circuit is
First and second terminals to which the resonance circuit is connected
And having
The oscillation signal is supplied to the mixer circuit as the local oscillation signal,
The resonant circuit is
A first DC cutting capacitor and a first resonance coil are connected in series between the first terminal and the ground,
Between the second terminal and the ground, a second DC cut capacitor, a variable capacitance diode, and a third DC cut capacitor are connected in series.
The connection midpoint of the first DC cut capacitor and the first resonance coil is connected to the connection midpoint of the second DC cut capacitor and the variable capacitance diode, and
Between the midpoint of connection and the ground, a switching diode, a resonance auxiliary coil, and a fourth DC cut capacitor are connected in series.
The first control voltage is supplied from the tuning control circuit to the connection midpoint of the auxiliary coil and the fourth DC cut capacitor through the first buffer circuit,
The second control voltage is supplied from the control circuit to the connection midpoint of the variable capacitance diode and the third DC cut capacitor through the second buffer circuit,
By switching the first control voltage to turn on / off the switching diode, the oscillation frequency range of the oscillation circuit is switched to switch the reception frequency range,
A synthesizer receiver configured to change the reception frequency in the reception frequency range by changing the oscillation frequency in the oscillation frequency range by changing the capacitance of the variable capacitance diode by changing the second control voltage. .

Images