JP2002118479A - Digital broadcasting receiving circuit, oscillated signal generating circuit, and method for receiving digital broadcast - Google Patents

Abstract

PROBLEM TO BE SOLVED: To receive digital terrestrial broadcasts by a simple configuration. SOLUTION: A first PLL synthesizer 3 controls the frequency of local oscillated signals generated from a first VCO 4 by impressing a voltage having the magnitude corresponding to the phase difference between a reference- frequency signal supplied from a crystal oscillator 2 and the local oscillated signals generated from the VCO 4 upon the VCO 4 by referring to the reference- frequency signal, and so on. A second PLL synthesizer 9 controls the frequency of local oscillated signals generated from a second VCO 10 by comparing the phase of the local oscillated signals with that of the reference-frequency signal supplied from the oscillator 2 through the first PLL synthesizer 3 after adjusting the frequency of the reference-frequency signal by dividing the frequency, and so on. A 1/2 frequency divider 15 inputs the local oscillated signals generated from the second VCO 10, generates a sampling clock signal by dividing the frequency of the oscillated signals into 1/2 frequencies, and supplies the clock signal to a demodulation IC 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcast receiving circuit for receiving digital terrestrial broadcasting, and more particularly to a digital broadcasting receiving circuit capable of receiving digital terrestrial broadcasting with a simple configuration.

[0002]

2. Description of the Related Art A receiving circuit having a configuration shown in FIG. 4, for example, is known as a device for converting the frequency of a received signal and demodulating a broadcast signal in order to receive digital terrestrial broadcasting. The receiving circuit shown in FIG.
After amplification by the amplifier 20 of, for example, a PLL (Phas
e Locked Loop) generated by the first local oscillator 22 including a synthesizer and the like.
_The local oscillator signal having _lo1 is _supplied to the first mixer 23
Multiply by. As a result, the reception signal of the radio frequency band is converted to the IF (Intermediate Frequen
cy) Convert to a signal. Here, _assuming that the frequency of the received signal in the radio frequency band is F _rf and the frequency of the IF signal in the first intermediate frequency band is F _if1 , the first local oscillator 2
2, the frequency (first frequency) _Flo1 of the local oscillation signal generated has the value defined by Expression 1.

[Number 1] _F lo1 _{= F} rf _{+ F if1}

[0003] The DVB-T (Digita
l In the case of Video Broadcasting-Terrestrial, the local oscillation signal generated by the first local oscillator 22 is 1 /
The frequency must be controllable in 6 MHz steps. Therefore, the first local oscillator 22 has, for example, TC
XO (Temperature Compensation crystal Oscillato
r) A local oscillation signal is generated with reference to the 16 MHz reference frequency signal generated by 21 and supplied to the first mixer 23. In addition, the first local oscillator 22 has a frequency of 4 MHz.
a reference frequency signal having a frequency that is a multiple of z,
The frequency of the local oscillation signal may be controlled with reference to a reference frequency signal having a frequency that is a multiple of 6 MHz.

[0004] The receiving circuit shown in FIG.
I down-converted to the first intermediate frequency band by
The F signal is passed through a first SAW (Surface Acoustic Wave) filter 24, a second amplifier 25, and a second SAW filter 26 in this order. Thereafter, the receiving circuit converts the IF signal of the first intermediate frequency band and the local oscillation signal having the second frequency _Flo2 generated by the second local oscillator 27 composed of, for example, TCXO into the second signal. Of the second intermediate frequency F _if2 = 4.571428 MHz as a center frequency. Here, the frequency of the local oscillation signal generated by the second local oscillator 27 (second frequency)
F _lo2 has a value defined by Expression 2.

## _EQU2 ## F _lo2 = F _if1 + F _if2

A demodulation IC (Integrated Circuit) 31
The 1/2 frequency divider 32 is a VCXO (Voltage Controlled cry).
An oscillation signal obtained by dividing the oscillation signal generated by the stal oscillator (oscillator) 33 is input as a sampling clock signal. The demodulation IC 31 uses this sampling clock signal to generate the second intermediate frequency F _{if 2}
And the first and second filters 29 and 30 with
The IF signal that has passed through is sampled. Demodulation IC3
The demodulator 1 can demodulate the broadcast signal by detecting the digitized IF signal.

[0006]

In the above prior art, the first local oscillator 22 and the second local oscillator 2
7, and the VCXO 33 independently generate the oscillation signal. However, since a circuit for generating such an oscillation signal such as a reference frequency signal requires higher accuracy and stability than other circuits, it is desirable to reduce the score as much as possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a digital broadcast receiving circuit capable of receiving digital terrestrial broadcasts with a simple configuration.

[0008]

In order to achieve the above object, a digital broadcast receiving circuit according to a first aspect of the present invention demodulates a broadcast signal from a received signal transmitting digital terrestrial broadcast. A reference frequency oscillating means for generating a reference frequency signal of a predetermined frequency, based on a reference frequency signal generated by the reference frequency oscillating means,
Generating a local oscillation signal having a first frequency;
A local oscillation signal generating means for generating a local oscillation signal having a second frequency based on a reference frequency signal generated by the reference frequency oscillating means; Frequency dividing means for dividing the local oscillation signal having the second frequency generated by the local oscillation signal generating means; and a local oscillation signal having the first frequency generated by the first local oscillation signal generating means. Receiving a local oscillation signal having a second frequency generated by the second local oscillation signal generating means, the first frequency converting means for down-converting the received signal into a first intermediate frequency signal; The first frequency converter down-converted by the first frequency converter
A second frequency converting means for down-converting the intermediate frequency signal into a second intermediate frequency signal, and a signal divided by the frequency dividing means as a sampling clock signal, and the second frequency converting means Demodulating means for digitizing the down-converted second intermediate frequency signal and demodulating a broadcast signal.

According to the present invention, the reference frequency signal generated by the reference frequency oscillating means is supplied to the first local oscillating signal generating means and the second local oscillating signal generating means, and the local oscillating signal is supplied. Can be generated. Further, the frequency dividing means can divide the frequency of the local oscillation signal generated by the second local oscillation signal generating means and supply it to the demodulating means as a sampling clock signal. As a result, it is possible to reduce the number of components that require high accuracy and stability to generate the reference frequency signal,
Digital terrestrial broadcasting can be received with a simple configuration.

[0010] More specifically, the first local oscillation signal generating means includes a first voltage controlled oscillator for generating a local oscillation signal having a first frequency, and a reference voltage generated by the reference frequency oscillating means. A first PLL synthesizer for controlling a frequency of a local oscillation signal generated by the first voltage-controlled oscillator with reference to a frequency signal, wherein the second local oscillation signal generating means sets a second frequency to A second voltage controlled oscillator for generating a local oscillation signal, and a local oscillation signal generated by the second voltage controlled oscillator with reference to a signal obtained by dividing the reference frequency signal generated by the reference frequency oscillating means. And a second PLL synthesizer for controlling the frequency of the local oscillation signal generated by the first voltage-controlled oscillator. It is desirable to control the wave number 1/6 MHz step.

Further, it is preferable that the second PLL synthesizer fixes the frequency of the local oscillation signal generated by the second voltage controlled oscillator to a predetermined frequency obtained by controlling the frequency in 1/7 MHz steps. .

A digital broadcast receiving circuit according to a second aspect of the present invention demodulates a broadcast signal from a received signal transmitting a digital terrestrial broadcast, and generates a reference frequency signal having a predetermined frequency. Reference frequency oscillating means, first local oscillation signal generating means for generating a local oscillation signal having a first frequency based on a reference frequency signal generated by the reference frequency oscillating means, A second local oscillation signal generating means for generating a local oscillation signal having a second frequency based on the generated reference frequency signal, a clock signal generating means for generating a sampling clock signal having a predetermined frequency, Receiving the local oscillation signal having the first frequency generated by the local oscillation signal generation means of
A first frequency converter for down-converting a received signal into a first intermediate frequency signal, and a local oscillation signal having a second frequency generated by the second local oscillation signal generator. A second frequency conversion means for down-converting the first intermediate frequency signal down-converted by the frequency conversion means into a second intermediate frequency signal; and a sampling clock signal generated by the clock signal generation means. And demodulating means for digitizing the second intermediate frequency signal down-converted by the second frequency converting means and demodulating a broadcast signal.

A digital broadcast receiving circuit according to a third aspect of the present invention demodulates a broadcast signal from a received signal transmitting digital terrestrial broadcasting, and generates a reference frequency signal having a predetermined frequency. Oscillating means, first local oscillation signal generating means for generating a local oscillation signal having a first frequency based on a reference frequency signal generated by the reference frequency oscillating means, Second local oscillation signal generating means for generating a local oscillation signal having a second frequency based on the reference frequency signal thus obtained, and a local oscillator having a second frequency generated by the second local oscillation signal generating means. First frequency conversion means for receiving an oscillation signal and down-converting a received signal into a first intermediate frequency signal; Receiving a local oscillator signal having a first frequency generated by Fushingo generating means, first down-converted by the first frequency converting means
A second frequency converting means for down-converting the intermediate frequency signal into a second intermediate frequency signal, and a reference frequency signal generated by the reference frequency oscillating means as a sampling clock signal, Demodulating means for digitizing the second intermediate frequency signal down-converted by the means and demodulating a broadcast signal.
It is characterized by the following.

According to the present invention, the reference frequency signal generated by the reference frequency oscillating means is supplied to the demodulating means as a sampling clock signal, and the first local oscillating signal generating means and the second local oscillating signal are provided. The local oscillation signal is also supplied to the generation means and can be generated. As a result, the number of components that require high accuracy and stability for generating the reference frequency signal can be reduced, and digital terrestrial broadcasting can be received with a simple configuration.

According to a fourth aspect of the present invention, there is provided an oscillation signal generating circuit for converting a frequency of a reception signal for transmitting digital terrestrial broadcasting, sampling, and executing a local oscillation signal and a sampling clock signal. And a reference frequency oscillating means for generating a reference frequency signal of a predetermined frequency; and a reference frequency signal generated by the reference frequency oscillating means, and converting the received signal into a first intermediate frequency signal. A first local oscillation signal generating means for generating a local oscillation signal for conversion and a signal obtained by dividing the reference frequency signal generated by the reference frequency oscillating means are referred to as a first intermediate frequency signal. A second local oscillation signal generating means for generating a local oscillation signal for converting the signal into an intermediate frequency signal of a second local oscillation signal; By dividing the local oscillation signal, and a frequency dividing means for generating a sampling clock signal for digitizing the second intermediate frequency signal, characterized in that.

A digital broadcast receiving method according to a fifth aspect of the present invention is a method for demodulating a broadcast signal from a received signal for transmitting a digital terrestrial broadcast, wherein a reference frequency signal having a predetermined frequency is generated. A reference frequency oscillation step; a first local oscillation signal generation step of generating a local oscillation signal having a first frequency based on the reference frequency signal generated in the reference frequency oscillation step; A second local oscillation signal generation step of generating a local oscillation signal having a second frequency based on the generated reference frequency signal, and a second frequency generated in the second local oscillation signal generation step. A frequency dividing step of dividing the local oscillating signal, and a first local oscillating signal generating step. A first frequency conversion step of receiving a local oscillation signal having a frequency of 1 and down-converting a received signal into a first intermediate frequency signal; and a second frequency generated in the second local oscillation signal generation step. Receiving a local oscillation signal having the following formulas: a second frequency conversion step of down-converting the first intermediate frequency signal down-converted in the first frequency conversion step into a second intermediate frequency signal; The signal divided in the step is used as a sampling clock signal,
And a demodulation step of digitizing the second intermediate frequency signal down-converted in the frequency conversion step and demodulating a broadcast signal.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital broadcast receiving circuit according to an embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a digital broadcast receiving circuit according to an embodiment of the present invention. As shown, this digital broadcast receiving circuit includes a first amplifier 1
, A crystal oscillator 2 and a first PLL (Phase Locked Loo
p) Synthesizer 3 and the first VCO (Voltage Control
led Oscillator) 4, first mixer 5, and first SA
W (Surface Acoustic Wave) filter 6, second amplifier 7, second SAW filter 8, second PLL synthesizer 9, second VCO 10, second mixer 1
1, a first filter 12, a second filter 13,
A demodulation IC (Integrated Circuit) 14 and a 1/2 frequency divider 15 are provided.

The first amplifier 1 is, for example, an LNA (Low No.
The digital broadcast receiving circuit is configured to amplify a received signal in a radio frequency band input to the digital broadcast receiving circuit.

The crystal oscillator 2 is a circuit for generating a reference frequency signal used for generating a local oscillation signal.

The first PLL synthesizer 3 is composed of, for example, a program frequency divider, a phase comparator, a loop filter, etc., and applies a reference frequency signal generated by the crystal oscillator 2 to the first VCO 4. Specifies the magnitude of the voltage. That is, the first PLL synthesizer 3
, The frequency of the local oscillation signal generated by the first VCO 4 is controlled.

The first VCO 4 is a voltage controlled oscillator for generating a local oscillation signal having a first frequency _Flo1 corresponding to the magnitude of the applied voltage defined by the first PLL synthesizer 3.

The first mixer 5 multiplies the received signal amplified by the first amplifier 1 by a local oscillation signal having a first frequency _Flo1 generated by a first VCO 4 to thereby obtain a first signal. _Is down-converted to an IF (Intermediate Frequency) signal having the intermediate frequency _Fif1 as a center frequency.

The first SAW filter 6 is a surface acoustic wave filter that functions as a band-pass filter that passes only a signal in a predetermined band, and filters an IF signal generated by down-conversion by the first mixer 5. , To the second amplifier 7.

The second amplifier 7 is, for example, an AGC (Automatic
tic Gain Control) circuit and the like, and the first SAW
The IF signal filtered by the filter 6 is amplified and sent to the second SAW filter 8.

The second SAW filter 8 is a surface acoustic wave filter that functions as a band-pass filter that passes only signals in a predetermined band, and filters the IF signal amplified by the second amplifier 7.

The second PLL synthesizer 9 receives a reference frequency signal generated by the crystal oscillator 2 via the first PLL synthesizer 3 and applies a voltage to the second VCO 10 based on the received reference frequency signal. Define the size of That is, the second PLL synthesizer 9
Controls the frequency of the local oscillation signal generated by the second VCO 10 by defining the magnitude of the voltage applied to the second VCO 10.

The second VCO10 is a voltage controlled oscillator for generating a local oscillator signal having a second frequency F _lo2 corresponding to the size of the defined voltage applied by the second PLL synthesizer 9.

The second mixer 11, the IF signal that has passed through the second SAW filter 8, by multiplying the local oscillation signal having a second frequency _{F lo2} generated by the second VCO 10, the second Intermediate frequency F
_This is for down-converting to an IF signal having _if2 as a center frequency.

The first filter 12 is, for example, an LPF (Lo
w Pass Filter) and performs filtering for removing aliasing components and the like included in the IF signal down-converted by the second mixer 11.

The second filter 13 is, for example, an HPF (Hi
gh Pass Filter) and the like, and the first filter 12
Performs filtering to remove low-frequency noise of the IF signal filtered by.

The demodulation IC 14 is an integrated circuit configured to demodulate a broadcast signal, and converts the IF signal filtered by the second filter 13 into a 1/2 frequency divider 1
The digitalization is performed by sampling according to the sampling clock signal supplied from 5. The demodulation IC 14 demodulates a broadcast signal by detecting a digitized IF signal and outputs the demodulated signal to a circuit for executing data processing, such as a deinterleaver or a descrambler.

The 1/2 frequency divider 15 is generated by the second VCO10 receives a local oscillator signal having a center frequency of a second frequency _{F lo2,} the sampling clock by the frequency dividing it by 2 A signal is generated and supplied to the demodulation IC 14.

The operation of the digital broadcast receiving circuit according to the embodiment of the present invention will be described below. The digital broadcast receiving circuit is a circuit that can receive a digital broadcast with a simple configuration by generating a local oscillation signal and a sampling clock signal using a reference frequency signal generated by the crystal oscillator 2.

When a received signal in a radio frequency band for transmitting digital terrestrial broadcasting is input to the digital broadcast receiving circuit, the first amplifier 1 amplifies the signal and sends it to the first mixer 5.

The first mixer 5 _{multiplies the} local oscillation signal having the first frequency _Flo1 received from the first VCO 4 by the reception signal received from the first amplifier 1 to obtain the first mixer. Down-conversion to an IF signal with the intermediate frequency F _if1 as the center frequency.

The IF signal down-converted by the first mixer 5 passes through a first SAW filter 6, a second amplifier 7, and a second SAW filter 8, and is then input to a second mixer 11. .

The second mixer 11, by multiplying the local oscillator signal, and the IF signal received from the second SAW filter 8 having a second frequency _{F lo2} received from the second VCO 10, the second _Is down-converted to an IF signal having the intermediate frequency _Fif2 as the center frequency.

The IF signal down-converted by the second mixer 11 is converted into first and second filters 12 and 13.
, And then input to the demodulation IC 14. The demodulation IC 14 executes a digitizing process for sampling the IF signal in accordance with the sampling clock signal supplied from the 1/2 frequency divider 15, and demodulates and outputs a broadcast signal.

When demodulating the broadcast signal in this manner, the first VCO 4 defines the first frequency F _{lo 1 in accordance} with the magnitude of the voltage applied by the first PLL synthesizer 3. Then, a local oscillation signal is generated. First
PLL synthesizer 3 refers to the reference frequency signal supplied from crystal oscillator 2, applies a voltage having a magnitude corresponding to the phase difference with the local oscillation signal generated by first VCO 4 to first VCO 4, etc. Then, the first frequency F of the local oscillation signal generated by the first VCO 4
controls _lo1 .

At this time, the first PLL synthesizer 3 converts the reference frequency signal supplied from the crystal oscillator 2 into
Send to the second PLL synthesizer 9.

The second PLL synthesizer 9 includes a first P
After dividing the reference frequency signal supplied from the crystal oscillator 2 via the LL synthesizer 3 to adjust the frequency, the phase is compared with the local oscillation signal generated by the second VCO 10. The second PLL synthesizer 9 applies a voltage having a magnitude corresponding to the phase difference between the reference frequency signal and the local oscillation signal to the second VCO 10, for example, to adjust the frequency of the local oscillation signal generated by the second VCO 10. Control.

The local oscillation signal generated by the second VCO 10 is sent to the second mixer 11 and
The signal is input to the 1/2 frequency divider 15.

The 分 frequency divider 15 generates a sampling clock signal by dividing the frequency of the local oscillation signal received from the second VCO 10 by 、, and generates a demodulation signal.
Supply to C14.

For example, here, the 1/2 frequency divider 15 outputs the demodulated I
Frequency F of sampling clock signal supplied to C14
It is assumed that _sa is F _sa = 18.285714 [MHz].

At this time, the second frequency F of the local oscillation signal generated by the second VCO 10
_{lo2 is, F lo2 = 2 × F sa} = 36.571428 [MH
z]. That is, the second frequency F _lo2 is 1 /
It is a multiple of 7 MHz. Therefore, the second PLL synthesizer 9 controls the frequency of the local oscillator signal the second VCO10 is generated based on the reference frequency signal supplied from the crystal oscillator 2 with 1/7 MHz _{step, F lo2}
= 36.571428 [MHz]. Thus, 1 /
The two-frequency divider 15 can generate a sampling clock signal having an appropriate frequency.

For example, the first intermediate frequency F _{if1 which} is the center frequency of the IF signal generated by the down-conversion of the first mixer 5 is F _if1 = 32 [MH]
z]. At this time, the second intermediate frequency _{Fif2, which} is the center frequency of the IF signal generated by the down-conversion of the second mixer 11, is defined as in Expression 3.

[Number 3] _{F if2 = F if1 -F lo2 =} 4.5714285 [MHz]

Further, the frequency F _{rf of the} received signal is F
_{Assuming that rf} = 474 [MHz], the first VCO
4 has a first frequency F of a local oscillation signal generated by
_lo1 is defined as in Expression 4.

[Number 4] _{F lo1 = F rf + F if1} = 474 + 32
[MHz] = 506 [MHz]

The first PLL synthesizer 3 refers to the reference frequency signal supplied from the crystal oscillator 2 to reduce the frequency of the local oscillation signal generated by the first VCO 4 to 1/6.
Control is performed in MHz steps. Thereby, for example, DVB-T (Digital Video Broadcasti
ng-Terrestrial) and can receive digital terrestrial broadcasting.

As described above, according to the present invention,
The reference frequency signal generated by the crystal oscillator 2 is
The sampling clock signal is also supplied to the second PLL synthesizer 9 via the LL synthesizer 3 and the frequency of the local oscillation signal generated by the second VCO 10 is divided so as to supply the demodulation IC 14 with the sampling clock signal. As a result, the number of components that require high accuracy and stability, such as an oscillator for generating the reference frequency signal, can be reduced, and digital broadcasting can be received with a simple configuration.

In the above embodiment, the second VCO
Although it has been described that the sampling clock signal is generated using the local oscillation signal generated by the step 10,
The present invention is not limited to this, and the same reference frequency signal may be used only in the front end portion. That is,
As shown in FIG. 2, the demodulation IC 14 has a frequency F _sa = 18.7514 supplied from an independently provided crystal oscillator 16.
[MHz] sampling clock signal
PLL synthesizer 3 and second PLL synthesizer 9
However, the reference frequency signal supplied from the crystal oscillator 2 may be used.

In this case, for example, the first PLL synthesizer 3 refers to the reference frequency signal supplied from the crystal oscillator 2 and controls the frequency of the local oscillation signal generated by the first VCO 4 in steps of 500 kHz. The second PLL synthesizer 9 includes the first PLL synthesizer 3
The reference frequency signal received from crystal oscillator 2 through
The frequency is divided into 2 MHz, which is a multiple of 00 kHz, and the frequency of the local oscillation signal generated by the second VCO 10 is controlled with reference to the divided signal. Thereby, the crystal oscillator 2
Can be supplied to the first PLL synthesizer 3 and the second PLL synthesizer 9 to generate a local oscillation signal.

When the frequency F _sa of the sampling clock signal supplied to the demodulation IC 14 can be set to an arbitrary value, for example, as shown in FIG. The generated reference frequency signal may be supplied to the first PLL synthesizer 3 and the second PLL synthesizer 9 to generate a local oscillation signal.

[0054]

As described above, according to the present invention, high accuracy and stability are required to generate an oscillation signal such as a reference frequency signal. , And digital terrestrial broadcasting can be received with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a digital broadcast receiving circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a modification of the digital broadcast receiving circuit according to the embodiment of the present invention.

FIG. 3 is a diagram showing a modification of the digital broadcast receiving circuit according to the embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional digital broadcast receiving circuit.

[Explanation of symbols]

 1, 7, 20, 25 Amplifier 2, 16, 17 Crystal oscillator 3, 9 PLL synthesizer 4, 10, VCO 5, 11, 23, 28 Mixer 6, 8, 24, 26 SAW filter 12, 13, 29, 30 Filter 14 , 31 demodulation IC 15, 32 1/2 frequency divider 21 TCXO 22, 27 local oscillator 33 VCXO

Claims (7)

[Claims] 1. A digital broadcast receiving circuit for demodulating a broadcast signal from a received signal transmitting digital terrestrial broadcasting, comprising: a reference frequency oscillating means for generating a reference frequency signal of a predetermined frequency; First local oscillation signal generation means for generating a local oscillation signal having a first frequency based on the generated reference frequency signal; and second local oscillation signal generation means based on the reference frequency signal generated by the reference frequency oscillation means. Second local oscillation signal generating means for generating a local oscillation signal having the frequency of: and frequency dividing means for dividing the local oscillation signal having the second frequency generated by the second local oscillation signal generating means. Receiving a local oscillation signal having a first frequency generated by the first local oscillation signal generating means, The down-converted to an intermediate frequency signal 1
Receiving a local oscillation signal having a second frequency generated by the second local oscillation signal generating means, and down-converting the first intermediate frequency signal by the first frequency converting means. Frequency conversion means for down-converting the signal into a second intermediate frequency signal, and a signal frequency-divided by the frequency division means as a sampling clock signal, which is down-converted by the second frequency conversion means. A demodulating means for digitizing the second intermediate frequency signal and demodulating a broadcast signal. 2. The first local oscillation signal generating means generates a local oscillation signal having a first frequency.
And a first PLL synthesizer for controlling the frequency of a local oscillation signal generated by the first voltage-controlled oscillator with reference to a reference frequency signal generated by the reference frequency oscillating means, The second local oscillation signal generating means generates a local oscillation signal having a second frequency.
And a second P controlling a frequency of a local oscillation signal generated by the second voltage controlled oscillator with reference to a signal obtained by dividing a reference frequency signal generated by the reference frequency oscillating means.
LL synthesizer, wherein the first PLL synthesizer reduces the frequency of the local oscillation signal generated by the first voltage controlled oscillator to 1 / 6M
The digital broadcast receiving circuit according to claim 1, wherein the digital broadcast receiving circuit controls the frequency in steps of Hz. 3. The second PLL synthesizer fixes a frequency of a local oscillation signal generated by the second voltage-controlled oscillator to a predetermined frequency obtained by controlling the frequency in 1/7 MHz steps. 3. The digital broadcast receiving circuit according to claim 2, wherein: 4. A digital broadcast receiving circuit for demodulating a broadcast signal from a received signal transmitting digital terrestrial broadcasting, comprising: a reference frequency oscillating means for generating a reference frequency signal of a predetermined frequency; First local oscillation signal generation means for generating a local oscillation signal having a first frequency based on the generated reference frequency signal, and second local oscillation signal generation means based on the reference frequency signal generated by the reference frequency oscillation means. Second local oscillation signal generation means for generating a local oscillation signal having a frequency of: a clock signal generation means for generating a sampling clock signal of a predetermined frequency; Receiving a local oscillation signal having a frequency of? And down converting the received signal to a first intermediate frequency signal.
Receiving a local oscillation signal having a second frequency generated by the second local oscillation signal generation means, and down-converting the first intermediate frequency signal by the first frequency conversion means. To a second intermediate frequency signal, a second frequency conversion means, and a sampling clock signal generated by the clock signal generation means, and a second frequency conversion means down-converted by the second frequency conversion means. And a demodulating means for digitizing the intermediate frequency signal and demodulating a broadcast signal. 5. A digital broadcast receiving circuit for demodulating a broadcast signal from a received signal transmitting digital terrestrial broadcasting, comprising: a reference frequency oscillating means for generating a reference frequency signal of a predetermined frequency; First local oscillation signal generation means for generating a local oscillation signal having a first frequency based on the generated reference frequency signal; and second local oscillation signal generation means based on the reference frequency signal generated by the reference frequency oscillation means. A second local oscillation signal generating means for generating a local oscillation signal having a frequency of: a local oscillation signal having a second frequency generated by the second local oscillation signal generating means; 1 to down convert to 1 intermediate frequency signal
Receiving a local oscillation signal having a first frequency generated by the first local oscillation signal generation means, and down-converting the first intermediate frequency signal by the first frequency conversion means. Frequency conversion means for down-converting to a second intermediate frequency signal, a reference frequency signal generated by the reference frequency oscillating means being input as a sampling clock signal, and being down-converted by the second frequency conversion means. Demodulating means for digitizing the obtained second intermediate frequency signal and demodulating a broadcast signal. 6. An oscillation signal generation circuit for generating a local oscillation signal and a sampling clock signal when performing frequency conversion and sampling of a reception signal for transmitting digital terrestrial broadcasting, comprising: A reference frequency oscillating means for generating a reference frequency signal, and a local oscillating signal for converting a received signal into a first intermediate frequency signal with reference to the reference frequency signal generated by the reference frequency oscillating means. A first local oscillation signal generating means, and a signal for converting the first intermediate frequency signal into a second intermediate frequency signal with reference to a signal obtained by dividing the reference frequency signal generated by the reference frequency oscillating means. Second local oscillation signal generating means for generating a local oscillation signal, and dividing the frequency of the local oscillation signal generated by the second local oscillation signal generating means A frequency dividing means for generating a sampling clock signal for digitizing the second intermediate frequency signal. 7. A digital broadcast receiving method for demodulating a broadcast signal from a received signal transmitting digital terrestrial broadcast, comprising: a reference frequency oscillating step of generating a reference frequency signal of a predetermined frequency; A first local oscillation signal generating step of generating a local oscillation signal having a first frequency based on the generated reference frequency signal, and a second local oscillation signal generating step based on the reference frequency signal generated in the reference frequency oscillation step. A second local oscillation signal generating step of generating a local oscillation signal having a frequency of: and a frequency dividing step of dividing the local oscillation signal having the second frequency generated in the second local oscillation signal generating step. A local oscillation signal having a first frequency generated in the first local oscillation signal generation step Receiving, a first down-converting the received signal into a first intermediate frequency signal
Receiving the local oscillation signal having the second frequency generated in the second local oscillation signal generation step, and down-converting the first intermediate frequency signal in the first frequency conversion step A second frequency conversion step of down-converting the signal into a second intermediate frequency signal, and a signal obtained by dividing the frequency in the frequency division step as a sampling clock signal, and the second frequency down-converted in the second frequency conversion step. A demodulating step of digitizing the intermediate frequency signal and demodulating a broadcast signal.