JP2007295286A - Oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to realize miniaturization and cost reduction, and at the same time, to sufficiently use a tuning voltage range at a time of signal band selection of a side in which a variable ratio of an oscillation frequency is small, and moreover to take tracking with a local oscillation frequency. <P>SOLUTION: The oscillator is provided with a varactor diode 21 an end of which tuning voltage Vt is impressed, a capacity coupling capacitor 11, a VHF oscillating circuit 10, and a 1/2 frequency divider 30. The 1/2 frequency divider 30 performs through operation at a time of VHF high band selection, and performs 1/2 frequency division operation at a time of VHF low band selection. Moreover, the oscillator creates a resonant signal using a large region of a capacity change region in a voltage-capacitance change curve of the varactor diode 21 at a time of VHF high band selection, and creates the resonant signal using a small region of the capacity change region in the voltage-capacity change curve of the varactor diode 21 at a time of VHF low band selection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an oscillation device capable of continuously oscillating in two oscillation frequency ranges having different oscillation frequency variable ratios.

  The television signal is received by being divided into a UHF band, a VHF high band, and a VHF low band depending on the frequency band. FIG. 4 is a block diagram of a conventional television signal receiving tuner. As shown in the figure, when a UHF television signal is received, the television signal received by the antenna 131 is fetched from the input terminal 132, tuned by the UHF single tuning circuit 133, and the UHF high frequency amplifier 134. The signal is amplified and tuned by the UHF double tuning circuit 135. The tuning frequency of the UHF single tuning circuit 133 and the UHF double tuning circuit 135 varies depending on the tuning voltage Vt output from the PLL integrated circuit 153, and is tuned in the frequency band of the receiving channel.

  The television signal output from the UHF double tuning circuit 135 is input to the UHF mixer 136. One input terminal of the UHF mixer 136 is connected to the output terminal of the UHF double tuning circuit 133, and the other input terminal is connected to the UHF local oscillator 137. The UHF local oscillator 137 is connected to the UHF resonance circuit 138, and the local oscillation signal output from the UHF local oscillator 137 is changed by the tuning voltage Vt input from the PLL integrated circuit 153 to the UHF resonance circuit 138. . The UHF local oscillator 137 outputs a local oscillation signal that is higher than the received television signal by a predetermined frequency, and an intermediate frequency signal subjected to frequency conversion is output from the output terminal of the UHF mixer 136.

  The intermediate frequency signal is input to the filter 151. The filter 151 is a band pass filter having a steep characteristic, and is connected to the intermediate frequency amplifier 152. The intermediate frequency signal amplified by the intermediate frequency amplifier 152 is output from an output terminal 156 of the tuner.

  When receiving a VHF high-band television signal, the television signal received by the antenna 131 includes a VHF high-band single tuning circuit 139, a VHF high-band high-frequency amplifier 140, a VHF high-band double-tuning circuit 141, The signal is input to the filter 151 via the VHF high band mixer 142. The VHF high-band local oscillator 143 is connected to the VHF high-band resonance circuit 144, and the VHF high-band local oscillator 143 is input by the tuning voltage Vt input from the PLL integrated circuit 153 to the VHF high-band resonance circuit 144. The local oscillation signal to be output changes.

  When a VHF low-band television signal is received, the television signal received by the antenna 131 is converted into a VHF low-band single tuning circuit 145, a VHF low-band high frequency amplifier 146, a VHF low-band double tuning circuit 147, and a VHF low-band mixing. The signal is input to the filter 151 via the device 148. In the VHF low-band local oscillator 149, the local oscillation signal output from the VHF low-band local oscillator 149 changes according to the tuning voltage Vt input to the VHF low-band resonance circuit 150.

  The PLL integrated circuit 153 is a circuit for selecting a reception channel. When receiving a UHF band channel, the PLL integrated circuit 153 applies a UHF band switching voltage Vu for selecting the UHF band to the UHF high-frequency amplifier 134, and The tuning voltage Vt corresponding to the selected channel is applied to the UHF single tuning circuit 133, the UHF double tuning circuit 135, and the UHF resonance circuit 138. When receiving a VHF high-band channel, a VHF high-band switching voltage Vhi for selecting the VHF high-band is applied to the VHF high-band high-frequency amplifier 140 and a tuning voltage Vt corresponding to the selected channel. Is applied to the VHF high-band single tuning circuit 139, the VHF high-band double tuning circuit 141, and the VHF high-band resonance circuit 144. When receiving a VHF low band channel, the VHF low band switching voltage Vlo for selecting the VHF low band is applied to the VHF low band high-frequency amplifier 146, and the tuning voltage Vt corresponding to the selected channel is used for the VHF low band. The voltage is applied to the single tuning circuit 145, the VHF low band double tuning circuit 147, and the VHF low band resonance circuit 150. In addition, a control voltage is applied to the local oscillator switch 155 in the PLL integrated circuit 153.

  FIG. 5 is a diagram illustrating a specific example of the VHF high-band local oscillator 143 and the VHF high-band resonance circuit 144 and a specific example of the VHF low-band local oscillator 149 and the VHF low-band resonance circuit 150. The VHF high-band resonance circuit 144 and the VHF low-band resonance circuit 150 are constituted by LC parallel resonance circuits in which coils 163 and 173 are connected in parallel to a series circuit of varactor diodes 161 and 171 and capacitors 162 and 172. Yes. Since the VHF high-band resonance circuit 144 has a wider oscillation frequency range than the VHF low-band resonance circuit 150, the VHF high-band resonance circuit 144 and the VHF high-band resonance circuit 144 are suppressed in order to suppress the influence of the IC side capacitor (VHF high-band local oscillator 143). A capacitive coupling capacitor 164 is provided between the local oscillator 143 for VHF high band. On the other hand, the VHF low band resonance circuit 150 is directly connected to the VHF low band local oscillator 149.

  Conventional television tuners have local oscillators (143, 149) and resonant circuits (144, 150) for VHF high band and VHF low band, respectively, for receiving the VHF band. For this reason, the number of parts of the local oscillators (143, 149) and the resonance circuits (144, 150) is increased, which hinders downsizing and cost reduction.

In view of this, it has been proposed that the resonant circuits for the VHF high band and the VHF low band are shared by using a frequency divider (see, for example, Patent Document 1). A local oscillation circuit and a frequency divider are provided, and a signal in the required reception band is obtained by dividing the oscillation signal of the local oscillator in accordance with the reception band.
JP 2006-050055 A

  However, since the VHF high band oscillation frequency range (for example, 179 MHz to 407 MHz) and the VHF low band oscillation frequency range (for example, 101 MHz to 171 MHz) are unbalanced, the VHF high band oscillation frequency variable ratio (407/179 = 2. 27) and the VHF low-band oscillation frequency variable ratio (1711/101 = 1.71) are different, and there is a problem that the tuning voltage range cannot be fully utilized when the VHF low-band is selected with a small oscillation frequency variable ratio. Further, when the VHF low band having a small oscillation frequency variable ratio is selected, the tuning frequency of each tuning circuit (145, 147) connected to the preceding stage of the VHF low band mixer 148 is not lowered to the reception frequency of the lowest channel, and the local oscillation frequency There was also a problem that the tracking with was not possible.

  The present invention has been made in view of such a point, and even if the oscillation frequency variable ratio is different between the first signal band and the second signal band, the present invention is configured by one resonance circuit and oscillation circuit. Provide an oscillation device that can be reduced in size and cost, and can fully utilize the tuning voltage range when selecting a signal band with a smaller oscillation frequency variable ratio, and can track the local oscillation frequency. The purpose is to do.

  The oscillation device of the present invention includes a variable capacitance element to which a tuning voltage is applied to one end grounded in terms of high frequency, a coupling capacitor having one end connected to the other end of the variable capacitance element, and the coupling capacitor. An oscillation circuit having an oscillation element connected to an end thereof, and a frequency divider connected to the output end of the oscillation circuit and having a variable frequency division ratio. When the second band is selected, the frequency division ratio at the time of selecting the second band is made larger than that at the time of selecting the first band, and at the time of selecting the first band and at the time of selecting the second band. A region having a different voltage-capacitance change curve of the variable capacitance element is used.

  According to this configuration, by using different regions of the voltage-capacitance change curve of the variable capacitance element when the first band is selected and when the second band is selected, the tuning voltage can be varied with respect to a predetermined fluctuation width. The capacitance change range of the capacitive element can be varied, and the region where the capacitance change range is large is selected when a band with a large oscillation frequency change ratio is selected, and the region where the capacitance change range is small when a band with a small oscillation frequency change ratio is selected. The tuning voltage range can be fully utilized even when a band having a small oscillation frequency change ratio is selected.

  According to the present invention, in the oscillation device, when the bandwidth of the first band is larger than that of the second band, a predetermined voltage is applied to the other end of the variable capacitance element when the first band is selected. A ground voltage is applied to the other end of the variable capacitance element when the second band is selected.

  With this configuration, a predetermined voltage is applied to the other end of the variable capacitive element when the first band is selected, which is a band selected with a large oscillation frequency change ratio, so that the voltage applied between the terminals of the variable capacitive element is the predetermined voltage. It is possible to use a region where the capacitance change range is large in the voltage-capacitance change curve. In addition, since the ground voltage is applied to the other end of the variable capacitance element when the second band is selected, which is when the band with a small oscillation frequency change ratio is selected, the voltage applied between both terminals of the variable capacitance element is increased and the capacitance is increased. It is possible to use a region where the change is small and the capacity change is small in the voltage-capacitance change curve.

  According to the present invention, in the oscillation device, when the bandwidth of the second band is larger than that of the first band, a predetermined voltage is applied to the other end of the variable capacitance element when the second band is selected. A ground voltage is applied to the other end of the variable capacitance element when the first band is selected.

  With this configuration, a predetermined voltage is applied to the other end of the variable capacitive element when the second band is selected, which is when a band having a large oscillation frequency change ratio is selected. It is possible to use a region where the capacitance change range is large in the voltage-capacitance change curve. In addition, since the ground voltage is applied to the other end of the variable capacitive element when the first band is selected, which is when the band having a low oscillation frequency change ratio is selected, the voltage applied between the two terminals of the variable capacitive element is increased. It is possible to use a region where the change is small and the capacity change is small in the voltage-capacitance change curve.

  According to the present invention, in the oscillation device, the switching element connected in parallel to the coupling capacitor, the switching element is turned off when the first band is selected, and the switching element is turned on when the second band is selected. And a circuit to be operated.

  With this configuration, the variable capacitance element and the oscillation circuit can be capacitively coupled via the coupling capacitor by turning off the switching element when the first band on the high band side is selected. Further, by turning on the switching element when the second band is selected, the variable capacitance element and the oscillation circuit can be directly connected without using a coupling capacitor.

  When the oscillation device of the present invention is applied to a television tuner, a signal output from the frequency divider when the first band is selected is a local oscillation signal for receiving a VHF high-band television signal, and the first The signal output from the frequency divider when the band of 2 is selected can be a local oscillation signal for receiving a VHF low-band television signal.

  When the oscillation device of the present invention is applied to a television tuner, the division ratio is set to 1 when receiving the VHF high band as the first band, and is divided when receiving the VHF low band as the second band. The ratio can be set to 2.

  According to the present invention, even if the oscillation frequency variable ratio is different between the first band and the second band, it is possible to reduce the size and cost by configuring with a single resonance circuit and oscillation circuit. Furthermore, the tuning voltage range can be fully utilized even when a band having a smaller oscillation frequency variable ratio is selected, and tracking with the tuning circuit can be achieved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In the present embodiment, in the television tuner shown in FIG. 4, the VHF high-band local oscillator 143 and the VHF high-band resonance circuit 144, and the VHF low-band local oscillator 149 and the VHF low-band resonance circuit 150 are included in the oscillation. This is an example in which the apparatus is applied.

  FIG. 1 is a configuration diagram of an oscillation device according to the present embodiment. The oscillation device shown in the figure includes one VHF oscillation circuit 10 shared by the VHF high band and the low band, one resonance circuit 20 that outputs a resonance signal for causing the VHF oscillation circuit 10 to oscillate at a desired frequency, and VHF oscillation. And a 1/2 frequency divider 30 that divides or passes through the local oscillation signal output from the circuit 10. The VHF oscillation circuit 10 includes an oscillation element that is excited by a resonance signal input from the resonance circuit 20. The VHF oscillation circuit 10 and the 1/2 frequency divider 30 are built in the integrated circuit 40, and the resonance circuit 20 is connected to input / output terminals 41 and 42 of the integrated circuit 40. The resonance signal output terminal of the resonance circuit 20 is connected to the input / output terminal 41 of the integrated circuit 40.

  A capacitive coupling capacitor 11 that capacitively couples the VHF oscillation circuit 10 and the resonance circuit 20 when the VHF high band is selected is provided in the integrated circuit 40. The capacitive coupling capacitor 11 is provided between the input / output terminal 41 to which the resonance signal output terminal of the resonance circuit 20 is connected and the input terminal of the VHF oscillation circuit 10. A diode 12 as a switching element is connected in parallel to the capacitive coupling capacitor 11. A bias circuit for turning on / off the diode 12 is connected to the anode of the diode 12. The stabilized power supply 14 is connected to the collector of the transistor 13 constituting the bias circuit, and the emitter of the transistor 13 is connected to the anode of the diode 12 via the bias resistor R3. On the other hand, the emitter of the transistor 13 is grounded via a resistor R4. A VHF low band selection signal BS1 is applied to the base of the transistor 13. The VHF low band selection signal BS1 becomes active when the VHF low band is selected, and becomes inactive in other cases.

  A bias circuit for applying a DC bias voltage from the input / output terminal 42 of the integrated circuit 40 to the resonance circuit 20 when the VHF high band is selected is provided in the integrated circuit 40. In such a bias circuit, a stabilized power supply 31 is connected to one end of resistors R1 and R2 connected in series, and the other end is connected to the ground. Further, an intermediate connection point between the resistors R 1 and R 2 is connected to the input / output terminal 42. The collector of the transistor 32 as a switching element is connected to the intermediate connection point of the resistors R1 and R2, and the emitter is connected to the ground side end of the resistor R2. A VHF low band selection signal BS1 is applied to the base of the transistor 32. The 1/2 frequency divider 30 includes a changeover switch (not shown) that switches between a 1/2 frequency division operation and a through operation, and is configured to apply a VHF low band selection signal BS1 to the changeover switch.

  The resonance circuit 20 is configured in the same manner as the VHF high band / low band resonance circuits 144 and 150 shown in FIG. That is, the cathode of the varactor diode 21 as a variable capacitance element is grounded in high frequency via the capacitor 22, one end of the coil 23 is connected to the anode of the varactor diode 21, and the other end of the coil 23 is high frequency via the capacitor 24. Grounded. An input / output terminal 42 of the integrated circuit 40 is connected to an intermediate connection point between the other end of the coil 23 and the capacitor 24. The anode of the varactor diode 21 serving as the output terminal of the resonance circuit 20 is connected to the input / output terminal 41 of the integrated circuit 40.

  The signal output from the 1/2 frequency divider 30 is supplied as a local oscillation signal to the VHF high band mixer 142 and the VHF low band mixer 148 shown in FIG. For convenience, two stabilized power sources 14 are shown in FIG. 1, but the same power source is used.

Next, the operation of the oscillation device according to the present embodiment configured as described above will be described.
FIG. 2A is an equivalent circuit diagram of the oscillating device when the VHF high band having a larger oscillation frequency variable ratio than the VHF low band is selected. When the VHF high band is selected, the VHF low band selection signal BS1 is controlled to be inactive, and the tuning voltage Vt is applied to the cathode of the varactor diode 21 in the resonance circuit 20 from the PLL circuit 153 shown in FIG.

  At this time, since the VHF low band selection signal BS1 is inactive, one transistor 13 is in a non-conductive state. As a result, the bias voltage from the stabilized power supply 14 is not applied to the anode of the diode 12 and the diode 12 is turned off, and the VHF oscillation circuit 10 is capacitively coupled to the resonance circuit 20 via the capacitive coupling capacitor 11. In other words, the circuit configuration is the same as the circuit configuration in which the VHF high-band oscillator 143 and the VHF high-band resonance circuit 144 illustrated in FIG. 5 are capacitively coupled via the capacitive coupling capacitor 164.

  On the other hand, the transistor 32 that grounds the intermediate connection point between the resistors R1 and R2 via the collector-emitter is also non-conductive. For this reason, the applied voltage of the stabilization power supply 14 is taken out from the intermediate connection point of the resistors R1 and R2 as the bleeder ratio (for example, 1 v) of the resistors R1 and R2, and the DC bias voltage (1 v) is Applied to an intermediate connection point with the capacitor 24. As a result, since a DC bias voltage (1v) is applied to the anode of the varactor diode 21, a voltage (cathode voltage) lower than the tuning voltage Vt set by the PLL circuit by the DC bias voltage (1v) is applied to the varactor diode 21. Will be applied. The resonance circuit 20 resonates with a varactor diode 21 capacitance controlled to a cathode voltage that is lower by a DC bias voltage (1 v), and the resonance signal is input to the VHF oscillation circuit 10 via the input / output terminal 41 and the coupling capacitor capacitor 11. Is done.

  In the VHF oscillation circuit 10, the built-in oscillation element oscillates at the resonance frequency of the resonance signal input from the resonance circuit 20. At this time, the 1/2 frequency divider 30 is in a through mode in which no frequency dividing operation is performed because the VHF low band selection signal BS1 is inactive. Therefore, the oscillation signal output from the VHF oscillation circuit 10 passes through the 1/2 frequency divider 30 and is supplied to the VHF high band mixer without being divided.

Here, a voltage-capacitance change curve of a varactor diode as a variable capacitance element will be described.
FIG. 3 is a characteristic diagram showing the relationship between the capacity of the varactor diode and the cathode voltage. As shown in the figure, it can be seen that the capacitance changes exponentially as the cathode voltage decreases. In the present embodiment, when a VHF high band with a large oscillation frequency variable ratio is selected, a positive DC bias voltage (for example, 1 V) is applied to the anode of the varactor diode 21, thereby making the actual cathode voltage a DC bias higher than the tuning voltage Vt. Only a voltage (for example, 1V) is lowered. If the change range of the cathode voltage corresponding to the change range of the tuning voltage Vt is Vt1 to Vt2, the capacitance change range of the varactor diode 21 with respect to the change range of the cathode voltage (Vt1 to Vt2) is W1. In the present embodiment, the capacitance change range W1 in the voltage-capacitance change curve of the varactor diode 21 is used when the VHF high band is selected.

  Since the resonance frequency of the resonance circuit 20 changes following the capacitance change of the varactor diode 21, the generated resonance frequency range can ensure a variable frequency range corresponding to the capacitance change range W1. For example, when the cathode voltage (Vt1) is the lower limit of the capacity change range W1, the resonance frequency is the lower limit value (179 MHz) of the VHF high band, and when the cathode voltage (Vt2) is the upper limit of the capacity change range W1, It sets so that it may become the resonant frequency of the upper limit (407 MHz) of a band.

  As described above, when the VHF high band is selected, the VHF oscillation circuit 10 and the resonance circuit 20 are connected via the capacitive coupling capacitor 11, and the cathode voltage of the varactor diode 21 is set to the low voltage side by a DC bias voltage (for example, 1V). Since the capacitance change range W1 having a large change range is used by shifting to the above, a wide range of local oscillation signals corresponding to the oscillation frequency variable ratio for the VHF high band can be generated.

  FIG. 2B is an equivalent circuit diagram of the oscillating device when the VHF low band having a smaller oscillation frequency variable ratio than the VHF high band is selected. When the VHF low band is selected, the VHF low band selection signal BS1 is activated and the tuning voltage Vt is applied to the cathode of the varactor diode 21 in the resonance circuit 20 from the PLL circuit 153 shown in FIG.

  At this time, since the VHF low-band selection signal BS1 is active, one transistor 13 is in a conductive state. As a result, a bias voltage from the stabilized power supply 14 is applied to the anode of the diode 12 via the resistor R3, and the diode 12 becomes conductive. As a result, both ends of the capacitive coupling capacitor 11 are short-circuited via the diode 12, and the VHF oscillation circuit 10 and the resonance circuit 20 are directly connected. That is, the circuit configuration is such that the VHF low band oscillator 149 and the VHF low band resonance circuit 150 in FIG.

  On the other hand, the transistor 32 that grounds the intermediate connection point of the resistors R1 and R2 via the collector-emitter is in a conductive state. Therefore, the intermediate connection point between the resistors R1 and R2 is grounded through the transistor 32 and becomes 0V. 0 V is applied to an intermediate connection point between the coil 23 and the capacitor 24 of the resonance circuit 20. As a result, the anode of the varactor diode 21 becomes 0V, and the cathode voltage of the varactor diode 21 becomes the tuning voltage Vt set by the PLL circuit. That is, the actual cathode voltage of the varactor diode 21 is higher by the DC bias voltage (1v) than the cathode voltage in a state where the DC bias voltage (1v) is applied. As a result, the resonance circuit 20 resonates with a capacitance controlled to a cathode voltage that is higher by a DC bias voltage (1v) than when the VHF high band is selected, and the resonance signal is transmitted via the input / output terminal 41 to the VHF oscillation circuit 10. Is input.

  In the VHF oscillation circuit 10, the built-in oscillation element oscillates at the resonance frequency of the resonance signal input from the resonance circuit 20. At this time, since the VHF low band selection signal BS1 is active, the 1/2 divider 30 is in the 1/2 dividing mode in which the 1/2 dividing operation is performed. Therefore, the oscillation signal output from the VHF oscillation circuit 10 is divided by 1/2 by the 1/2 divider 30 and supplied to the VHF low band mixer.

  In the present embodiment, when VHF low band having a small oscillation frequency variable ratio is selected, 0V is applied to the anode of the varactor diode 21 so that the cathode voltage is changed to a DC bias voltage rather than a state where a DC bias voltage (for example, 1V) is applied. It ’s just a minute higher. The change range of the cathode voltage corresponding to the change range of the tuner voltage Vt is shifted to the high potential side by the amount that the DC bias voltage is not applied, and becomes Vt11 to Vt22. The capacitance change range of the varactor diode 21 is W2 with respect to the cathode voltage change range Vt11 to Vt22. As apparent from FIG. 3, when the VHF low band is selected, a capacitance change range W2 narrower than the capacitance change range W1 used when the VHF high band is selected is used. When VHF low band is selected, a capacitance change range W2 that is narrower than when VHF high band is selected is used. Therefore, even if the change range of the tuner voltage Vt applied to the varactor diode 21 is the same, the frequency range of the generated resonance frequency is It will be narrowed. For example, when the cathode voltage (Vt11) is the lower limit of the capacity change range W2, the resonance frequency is the lower limit value (101 MHz) of the VHF low band, and when the cathode voltage (Vt22) is the upper limit of the capacity change range W2, the VHF low band is The resonance frequency is set to the upper limit (171 MHz).

  Thus, when the VHF low band is selected, the VHF oscillation circuit 10 and the resonance circuit 20 are directly coupled without capacitive coupling, the cathode voltage of the varactor diode 21 is shifted to the high voltage side, and the capacitance change range W2 is reduced. A local oscillation signal in a frequency range corresponding to the oscillation frequency variable ratio for VHF low band can be generated.

  As described above, according to the present embodiment, when the VHF high band having a large oscillation frequency variable ratio is selected, the capacitance change range W1 that can ensure a larger capacitance change in the voltage-capacitance change curve of the varactor diode 21 in the resonance circuit 20. When the VHF low band with a small oscillation frequency variable ratio is selected, the oscillation frequency is obtained by using the capacitance change range W2 in the resonance circuit 20 in which the capacitance change is relatively small in the voltage-capacitance change curve of the varactor diode 21. As a result, the voltage range of the tuning voltage Vt can be fully utilized even when the VHF low band having a small oscillation frequency variable ratio is selected. Further, even when the VHF low band with a small oscillation frequency variable ratio is selected, the entire range of the tuning voltage Vt is not used to narrow the voltage range, so that the tuning frequency of each tuning circuit (145, 147) is set to the lowest channel reception frequency. And tracking with the local oscillation frequency can be taken.

  In the above embodiment, the case where the oscillation frequency variable ratio on the VHF high band side is large and the oscillation frequency variable ratio on the VHF low band side is small is described as an example. However, the present invention is not limited to such a case. For example, when the oscillation frequency variable ratio is smaller in the VHF high band than in the VHF low band, the capacitance change range W1 that can ensure a large capacitance change in the voltage-capacitance change curve of the varactor diode 21 when the VHF low band is selected is used. Like that. In the above description, the local oscillation signal output from the VHF oscillation circuit 10 is divided by ½ by the ½ divider 30. However, the division ratio depends on the oscillation frequency range of the high band side and the low band side. Set as appropriate.

  The present invention is not limited to an oscillation device applied to a television tuner. Similarly, if the oscillation frequency range is divided into a plurality of ranges and the oscillation frequency variable ratio of each oscillation frequency range is different, the present invention is similarly applied. Applicable.

  The present invention can be applied to an application in which the oscillation frequency range is divided into a plurality of ranges and the oscillation frequency variable ratios of the respective oscillation frequency ranges are different.

Configuration diagram of an oscillation device according to an embodiment of the present invention (A) Equivalent circuit diagram of the oscillation device shown in FIG. 1 when VHF high band is selected, (b) Equivalent circuit diagram of the oscillation device shown in FIG. 1 when VHF low band is selected Characteristic diagram showing voltage-capacitance curve of varactor diode Overall configuration diagram of a conventional television tuner Configuration diagram of an oscillation device applied to the television tuner shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 VHF oscillation circuit 11 Capacitance coupling capacitor 12 Diode 13, 32 Transistor 14 Stabilized power supply 20 Resonance circuit 21 Varactor diode 22, 24 Capacitor 23 Coil 30 1/2 frequency divider 40 Integrated circuit 41, 42 Input / output terminal

Claims (6)

A variable capacitance element in which a tuning voltage is applied to one end grounded in a high frequency manner;
A coupling capacitor having one end connected to the other end of the variable capacitance element;
An oscillation circuit having an oscillation element connected to the other end of the coupling capacitor;
A frequency divider connected to the output end of the oscillation circuit and having a variable frequency dividing ratio;
While the first band selection on the high band side and the second band selection on the low band side, the frequency division ratio at the time of the second band selection is larger than that at the time of the first band selection,
An oscillation device characterized in that different regions of voltage-capacitance change curves of the variable capacitance element are used when the first band is selected and when the second band is selected.   When the bandwidth of the first band is larger than that of the second band, a predetermined voltage is applied to the other end of the variable capacitance element when the first band is selected, and when the second band is selected, 2. The oscillation device according to claim 1, wherein a ground voltage is applied to the other end of the variable capacitance element.   When the bandwidth of the second band is larger than that of the first band, a predetermined voltage is applied to the other end of the variable capacitance element when the second band is selected, and when the first band is selected, 2. The oscillation device according to claim 1, wherein a ground voltage is applied to the other end of the variable capacitance element.   A switching element connected in parallel to the coupling capacitor; and a circuit that turns off the switching element when the first band is selected and turns on the switching element when the second band is selected. The oscillation device according to any one of claims 1 to 3.   The signal output from the frequency divider when the first band is selected is a local oscillation signal for receiving a VHF high-band television signal, and the signal output from the frequency divider when the second band is selected is 5. The oscillation device according to claim 1, wherein the oscillation device is a local oscillation signal for receiving a VHF low-band television signal. The frequency divider sets a frequency division ratio to 1 when receiving a VHF high band serving as a first band, and sets a frequency division ratio to 2 when receiving a VHF low band serving as a second band. The oscillation device according to claim 5.

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