JP2003264473A - Semi-conductor ic for adjusting tracking filter, and tracking filter adjusting system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tracking filter adjusting semiconductor IC which reduces the system price, and also to provide a tracking filter adjusting system using the IC. <P>SOLUTION: The semiconductor IC internally includes: a frequency converting circuit part which comprises a local oscillation circuit 14 connected to a first variable capacitance diode 7 whose capacitance is controlled by receiving a first tuning control voltage, converts the frequency of a signal inputted from an external tracking filter 3, and outputs it; and a voltage converting circuit 20 for receiving the first tuning control voltage, converting it into a second tuning control voltage, and outputting the second voltage to an outer part to supply it to a second variable capacitance diode 8 for adjusting the characteristics of a tracking filter. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit (LSI) for adjusting a tracking filter and a tracking filter adjusting system using the same, and more particularly to a control voltage generating circuit for a variable capacitance diode and a tracking filter using the same. The present invention relates to an adjusting system, and is used in, for example, a television tuner or the like.

[0002]

2. Description of the Related Art FIG. 4 shows an LSI for adjusting a tracking filter used in a television tuner for VHF, for example.
1 shows a conventional example 1 of a tracking filter adjustment system using the same.

In FIG. 4, 1 is a receiving antenna, 2 is an RF amplifier for amplifying a high frequency (RF) signal received by the receiving antenna, and 3 is a signal for extracting a signal of a desired frequency component from an output signal of the RF amplifier. It is a tracking filter.

The tracking filter adjustment LSI 40 is
Frequency fRF input from external tracking filter 3
It has a built-in frequency conversion circuit that converts the RF signal of to the specified intermediate frequency fIF (= fLOSC-fRF, 58.75MHz for domestic VHF tuner) using the local signal of frequency fLOSC and outputs it.

The frequency conversion circuit section includes a first amplification circuit 11 for amplifying a signal input from an external tracking filter 3 and a frequency mixing circuit (mixer) for frequency conversion of an output signal of the first amplification circuit 11. 12, a second amplifier circuit 13 that amplifies the output signal of the frequency mixing circuit 12 and outputs the amplified signal to the outside, a local oscillating circuit 14 that supplies a local signal to the frequency mixing circuit 12, and the local oscillating circuit 14. A PLL control circuit (including a reference clock generation circuit, a frequency dividing circuit, a phase comparison circuit, etc.) 15 forming a part of a phase locked loop (PLL) is provided.

Outside the LSI, a vibrator 4 connected to a reference clock generation circuit in the PLL control circuit 15 and a part of the PLL connected to the local oscillation circuit 14 are formed.
Output frequency of local oscillator circuit 14 (local oscillator frequency
fLOSC) first variable capacitance diode 41 for adjusting
And a low-pass filter (LPF) 42 that forms a part of the PLL and outputs a feedback control voltage of 0 V to 33 V, and the PL
A CPU 6 for supplying tuning channel frequency designation data to the L control circuit 15 and a second variable capacitance diode 8 connected to the tracking filter 3 for adjusting its characteristic (center frequency) are provided. .

FIG. 5 shows an example of the relationship (voltage / frequency characteristic) between the tuning control voltage vt supplied to the first variable capacitance diode 41 in FIG. 4 and the local oscillation frequency fLOSC.

As described above, in the tracking filter adjusting system of the first conventional example, the feedback control voltage vt of 0V to 33V output from the LPF 52 is applied to the first variable capacitance diode 41 and the second variable capacitance diode 8. It is commonly supplied as a tuning control voltage. But,
The number of parts used outside the LSI is large, the number of assembly steps is large, and the system price is high.

On the other hand, FIG. 6 shows a conventional example 2 of a tracking filter adjustment LSI used in a VHF television tuner and a tracking filter adjustment system using the same.

The configuration of FIG. 6 is different from the configuration of the conventional example 1 described with reference to FIG. 4 in the following points, and the other points are almost the same.

(1) LSI 6 for tracking filter adjustment
The first variable capacitance diode 7 of the low withstand voltage type that can operate at an operating power supply voltage of 0 (for example, 5 V) or less
Built in.

(2) As the LPF 5 which constitutes a part of the PLL,
For example, it is configured to output a feedback control voltage of 0V to 5V, and this feedback control voltage is used as the first tuning control voltage Vt.
It is supplied to the first variable capacitance diode 7 as 1.

(3) A nonvolatile memory 51 which is supplied with tuning channel frequency designation data from the CPU 6 and outputs desired tuning control data, and digital / analog (D / A) data output from the nonvolatile memory 51. Convert, 0V ~
Generate a second tuning control voltage Vt2 of 33V
A D / A conversion circuit 52 for supplying the variable capacitance diode 8 is added.

As described above, in the tracking filter adjustment system of the second conventional example, the first variable capacitance diode 7 of the low withstand voltage type is provided in the LSI 6 as compared with the configuration of the first conventional example.
Since it is built in 0, the first variable capacitance diode (41 in FIG. 4) outside the LSI can be omitted, but since the expensive nonvolatile memory 51 and D / A conversion circuit 52 are added outside the LSI. , The price of the system will be high.

[0015]

As described above, the LSI for tracking filter adjustment of the second conventional example and the tracking filter adjustment system using the same use an expensive non-volatile memory outside the LSI. There was a problem that the price would be high.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor integrated circuit for tracking filter adjustment which can reduce the system price, and a tracking filter adjustment system using the same. .

[0017]

A semiconductor integrated circuit according to the present invention has a local oscillation circuit connected to a first variable capacitance diode, the capacitance of which is controlled by receiving a first tuning control voltage. A frequency conversion circuit unit that frequency-converts and outputs the signal input from the tracking filter,
A voltage conversion circuit which receives the first tuning control voltage, converts it into a second tuning control voltage, and outputs it to the outside in order to supply it to the second variable capacitance diode for adjusting the characteristic of the tracking filter. It is characterized by being built-in.

The tracking filter adjusting system of the present invention is connected to the semiconductor integrated circuit of the present invention, a tracking filter provided outside the semiconductor integrated circuit, and the tracking filter, and supplies the second tuning control voltage. And a second variable capacitance diode for adjusting the characteristics of the tracking filter.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment> FIG. 1 shows a first embodiment of the present invention.
2 shows an example of a tracking filter adjustment LSI used in, for example, a VHF television tuner and a tracking filter adjustment system using the same according to the embodiment of FIG.

The configuration of FIG. 1 is different from the configuration of the conventional example 2 described with reference to FIG. 6 in the following points, and the other points are almost the same.

(1) LSI 1 for tracking filter adjustment
0 is the second tuning control voltage vt2 of, for example, 0V to 33V when receiving the first tuning control voltage vt1 of, for example, 0V to 5V output from the LPF5 outside the LSI that constitutes a part of the PLL.
It has a built-in voltage conversion circuit 20 that converts the signal into a signal and outputs it to the outside of the LSI.

(2) By supplying the second tuning control voltage vt2 output from the voltage conversion circuit 20 to the outside of the LSI to the second variable capacitance diode 8 outside the LSI,
I The external non-volatile memory (51 in Fig. 6) and D / A conversion circuit (52 in Fig. 6) are omitted.

That is, in FIG. 1, 1 is a receiving antenna,
Reference numeral 2 is an RF amplifier that amplifies the RF signal received by the receiving antenna, and 3 is a tracking filter for extracting a signal of a desired frequency component from the output signal of the RF amplifier.

The tracking filter adjustment LSI 10 is
Frequency fRF input from external tracking filter 3
The built-in frequency conversion circuit section converts the RF signal of the frequency signal to a predetermined intermediate frequency fIF (= fLOSC-fRF, 58.75 MHz in the domestic VHF tuner) using a local signal of frequency fLOSC and outputs the frequency signal.

The frequency conversion circuit section includes a first amplification circuit 11 for amplifying a signal input from an external tracking filter, and a frequency mixing circuit (mixer) 12 for frequency conversion of an output signal of the first amplification circuit. , This frequency mixing circuit
A second amplifier circuit that amplifies the 12 output signals and outputs them to the outside
13, a local oscillation circuit 14 for supplying a local signal to the frequency mixing circuit 12, and a local oscillation frequency fLOSC which is connected to the local oscillation circuit 14 to form a part of the PLL.
For adjusting the first variable capacitance diode 7, and the local oscillator circuit 14 and the first variable capacitance diode 7, and a PLL control circuit (reference clock generation circuit, frequency dividing circuit, phase control circuit) that constitutes a part of the PLL. (Including a comparison circuit) 15). The first variable capacitance diode 7
Is a low withstand voltage type that can operate at an operating power supply voltage (for example, 5 V) or less of the LSI 10.

Outside the LSI, a vibrator 4 connected to a reference clock generation circuit in the PLL control circuit 15, an LPF 5 that forms a part of the PLL and outputs a feedback control voltage in the PLL,
The CPU 6 for supplying the tuning channel frequency designation data to the PLL control circuit 15 and the second for connecting to the tracking filter 3 for adjusting the filter characteristic (center frequency)
The variable capacitance diode 8 is provided. LPF5 above
Usually uses a large capacitive element for characteristic adjustment, so
Often provided outside the LSI.

The main parts in FIG. 1 are other parts (IF
It is mounted on the same mounting board together with subsequent LSIs, etc.) to form a module, and is built in, for example, a metal shield case. Although not shown, the UHF television tuner is also configured in substantially the same manner as the VHF television tuner.

By the way, the local oscillator circuit 14 in FIG. 1 and the first variable capacitance diode 7 connected to the local oscillator circuit 14 are shown.
Must be configured to be able to continuously change the frequency over the required local frequency range by receiving the first tuning control voltage vt1 of 0V to 5V output from LPF5.

In order to easily realize the above configuration, the required local frequency range is divided into a plurality of divisions and is in charge.
A plurality of sets (three sets in this example) of the local oscillator circuit 14 and the first variable capacitance diode 7 are provided, and these three sets are switched by a switching element controlled by a control signal from the PLL control circuit 15. It is configured to be used selectively.

Not limited to the above three sets of local oscillator circuits 14 and the first variable capacitance diodes 7, one first variable capacitance diode 7 is selectively provided for the three local oscillation circuits 14 provided. You may make it the structure which carries out switching control so that it may connect.

For convenience, the above-mentioned three sets of local oscillation circuits 14 and the first variable capacitance diodes 7 or a selective combination of the three local oscillation circuits 14 and one first variable capacitance diode 7 are used. , Three local oscillation circuits having different local frequency ranges.

In order to explain an example of the operating principle of the local oscillator circuit 14 and the first variable capacitance diode 7 in FIG. 1, FIG. 2 shows input voltages (third oscillator voltage) for three oscillator circuits having different local frequency ranges. Tuning voltage of 1
Vt1) and output frequency (local oscillation frequency fLOSC characteristic)
1 shows an example of the relationship (voltage / frequency characteristic).

That is, one of the three local oscillator circuits receives the first tuning control voltage Vt1 of 0V to 5V and continuously adjusts the local frequency within a low frequency region of the local frequency range. It is configured to change.

Another one of the three local oscillator circuits is a first tuning control voltage Vt of 0V to 5V.
In response to 1, the local frequency is continuously changed in an intermediate frequency range of the local frequency range.

Further, another one of the three local oscillator circuits receives the first tuning control voltage Vt1 of 0V to 5V and continuously localizes in a high frequency range of the local frequency range. It is configured to change the frequency.

By the way, the voltage conversion circuit 20 in FIG.
First tuning control voltage Vt of 0V to 5V output from F5
The second tuning control voltage Vt2 of 0V to 33V in response to 1
Need to be configured to convert to.

In order to easily realize the above configuration, one example of the voltage conversion circuit 20 is a DC voltage amplifier 21 for expanding an input voltage (first tuning control voltage) of 0V to 5V to an output voltage of 0V to 11V. , A predetermined offset voltage is selected as necessary based on the control signal from the PLL control circuit, and added to the output voltage of the DC voltage amplifier (DC amplifier) 21 (combined)
An offset voltage selection circuit 22 for supplying the voltage and an offset voltage generation circuit (not shown) for generating the predetermined offset voltage. In this case, the constituent elements of the tracking filter adjusting LSI 10 are mainly bipolar transistors, but a high breakdown voltage type field effect transistor of 33 V or more is used in the final stage of the DC voltage amplifier 21.

FIG. 3 shows an example of the relationship (input / output voltage conversion characteristic) between the input voltage (first tuning voltage Vt1) and the output voltage (second tuning voltage Vt2) of the voltage conversion circuit 20 shown in FIG. Shows.

That is, one of the three local oscillator circuits
When the individual units are controlled by the first tuning control voltage Vt1 and oscillate in the low frequency region of the local frequency range, the input voltage of 0V to 5V is expanded to the output voltage of 0V to 11V and output as it is. .

On the other hand, when another one of the three local oscillator circuits is controlled by the first tuning control voltage Vt1 to oscillate in the intermediate frequency range of the local frequency range, , 0V ~ 5V input voltage 0V ~ 11
It expands to the V output voltage and adds the 11V offset voltage to convert it to the 11V to 22V output voltage.

On the other hand, another one of the three local oscillator circuits is connected to the first tuning control voltage Vt.
When controlled by 1 to oscillate in the high frequency range of the local frequency range, input voltage from 0V to 5V is changed to 0V.
It expands to the output voltage of ~ 11V and adds the offset voltage of 22V to convert it to the output voltage of 22V ~ 33V.

In the tracking filter adjustment LSI 10 having the configuration shown in FIG. 1 and the tracking filter adjustment system using the same as described above, the first tuning control of 0V to 5V output from the LPF 5 forming a part of the PLL is performed. The voltage Vt1 is supplied to the first variable capacitance diode 7 inside the LSI 10 to generate a desired local frequency signal. Further, a voltage conversion circuit 20 for converting the first tuning control voltage Vt1 into a second tuning control voltage Vt2 of 0V to 33V is built in the LSI10, and the second tuning control voltage Vt2 is supplied to the outside of the LSI10. 2 variable capacitance diodes
8 to adjust the tracking filter 3 to a desired characteristic (center frequency).

Therefore, as compared with the configuration of the conventional example 2, the LS
I External expensive non-volatile memory (51 in Figure 6) and D / A
Although the conversion circuit (52 in FIG. 6) can be omitted, the system cost can be reduced.

[0045]

As described above, according to the present invention, it is possible to provide a semiconductor integrated circuit for tracking filter adjustment which can reduce the system price and a tracking filter adjustment system using the same.

[Brief description of drawings]

FIG. 1 is an LSI for adjusting a tracking filter used in a television tuner according to a first embodiment of the present invention.
FIG. 3 is a configuration explanatory view showing an example of a tracking filter adjustment system using the same.

FIG. 2 is a diagram illustrating an example of an operating principle of a local oscillator circuit and a first variable capacitance diode in FIG. 1 in order to explain an input voltage (first tuning voltage) of each of three oscillator circuits having different local frequency ranges. A characteristic diagram showing an example of the relationship between vt1) and the output frequency (local oscillation frequency fLOSC characteristic).

FIG. 3 is a characteristic diagram showing an example of a relationship between an input voltage (first tuning voltage vt1) and an output voltage (second tuning voltage vt2) of the voltage conversion circuit 20 in FIG.

FIG. 4 is a configuration explanatory diagram showing a conventional example 1 of a tracking filter adjustment LSI used in a television tuner and a tracking filter adjustment system using the same.

5 shows a tuning control voltage vt supplied to the first variable capacitance diode in FIG. 4 and a local oscillation frequency fLOSC.
FIG. 6 is a characteristic diagram showing an example of a relationship with

FIG. 6 is a configuration explanatory view showing a conventional example 2 of a tracking filter adjustment LSI used in a television tuner and a tracking filter adjustment system using the same.

[Explanation of symbols]

1… receiving antenna, 2… RF amplifier, 3… Tracking filter, 4 ... oscillator, 5… Low-pass filter (LPF), 6… CPU, 7 ... first variable capacitance diode, 8 ... second variable capacitance diode, 10 ... LSI for tracking filter adjustment 11 ... the first amplifier circuit, 12 ... frequency mixing circuit, 13 ... second amplifier circuit, 14 ... Local oscillator circuit, 15 ... PLL control circuit, 20 ... Voltage conversion circuit.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5C025 AA25                 5K020 AA02 BB04 DD15 EE01 EE02                       EE03 HH02                 5K058 AA01 AA03 BA02 CA01 CA05                       DA14 DB04 EA08 EA17 GA16                 5K062 AA06 AC02 BB13 BC03

Claims (7)

[Claims] 1. A local oscillation circuit connected to a first variable capacitance diode, the capacitance of which is controlled by receiving a first tuning control voltage, and frequency-converts and outputs a signal input from an external tracking filter. And a frequency conversion circuit unit for receiving the first tuning control voltage, converting the second tuning control voltage to a second tuning control voltage, and externally supplying the second tuning capacitor to the second variable capacitance diode for adjusting the characteristic of the tracking filter. A semiconductor integrated circuit for adjusting a tracking filter, comprising a voltage conversion circuit for outputting. 2. The frequency conversion circuit unit, a frequency mixing circuit for frequency converting an input signal, a local oscillator circuit for supplying a local signal for frequency conversion to the frequency mixing circuit, and a feedback control voltage in a phase locked loop. A first variable capacitance diode for adjusting the oscillation frequency of the local oscillation circuit and a phase together with the local oscillation circuit and the first variable capacitance diode. 2. A semiconductor integrated circuit for adjusting a tracking filter according to claim 1, further comprising a PLL control circuit forming a part of the synchronous loop PLL. 3. The maximum value of the first tuning control voltage is less than or equal to the operating power supply voltage of the semiconductor integrated circuit, and the second tuning control voltage is a voltage higher than the first tuning control voltage. 3. A semiconductor integrated circuit for adjusting a tracking filter according to claim 1, wherein the variation range of the voltage is wide and the maximum value of the voltage is high. 4. The local oscillator circuit and the first variable capacitance diode connected thereto are provided with at least three local oscillator circuits so as to divide a required local frequency range into a plurality of divisions. 4. The tracking filter adjusting device according to claim 1, wherein the three local oscillator circuits are selectively used by being switched by a control signal from the PLL control circuit. Semiconductor integrated circuit. 5. The DC voltage amplifier, wherein the voltage conversion circuit receives the first tuning control voltage and expands to an output voltage having a wider maximum voltage range than the first tuning control voltage, and the PLL. 2. An offset voltage selection circuit for selecting a predetermined offset voltage as necessary based on a control signal from the control circuit and supplying the voltage for addition to the output voltage of the DC voltage amplifier. 5. A semiconductor integrated circuit for adjusting a tracking filter according to any one of items 1 to 4. 6. The semiconductor integrated circuit according to claim 1, a tracking filter provided outside the semiconductor integrated circuit, and a second tuning control connected to the tracking filter. A tracking filter adjustment system comprising: a second variable capacitance diode for adjusting a characteristic of the tracking filter by being supplied with a voltage. 7. The semiconductor integrated circuit is provided outside the semiconductor integrated circuit,
A low-pass filter forming a part of the phase-locked loop and generating the first tuning control voltage as a feedback control voltage in the phase-locked loop; and a low-pass filter provided outside the semiconductor integrated circuit and inside the semiconductor integrated circuit. 7. The tracking filter adjustment system according to claim 6, further comprising a CPU for supplying channel selection channel frequency designation data to the.