JP3529644B2 - Tuner circuit of digital broadcast receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to terrestrial television broadcasting and cable television (CATV) in which digitally compressed video and audio are transmitted by a modulation system such as an OFDM (Orthogonal Frequency Division Multiplexing) system. The present invention relates to a digital broadcast receiving apparatus that is preferably implemented for reception.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing an electrical configuration of a tuner section of an analog broadcast television receiver. A received high frequency signal input from an input terminal 1 connected to an antenna or a CATV cable is separated into a UHF signal component and a VHF signal component in a band separation filter 2, and a band pass filter (hereinafter, referred to as BPF).
Abbreviated as 10) and 20).

As for the UHF signal component, a signal component in the vicinity of the selected channel is selected by the BPF 10 which serves as a UHF input tuning circuit, is limited to a predetermined level range by the high frequency amplifier circuit 11, and further serves as a UHF interstage tuning circuit. After being detuned in, the signal is supplied to the mixing circuit 13. The local oscillation signal from the local oscillation circuit 14 is given to the mixing circuit 13. The local oscillation signal is also given to the PLL circuit 4, and the PLL circuit 4
Is responsive to a tuning signal provided from a tuning circuit (not shown) such as a microcomputer, in response to the local oscillation circuit 1
The control voltage to the resonance circuit 15 provided in relation to 4 is changed to change the resonance frequency of the resonance circuit 15. Thus, the frequency of the local oscillation signal is stably controlled so as to correspond to the frequency of the broadcasting station to be received.

Similarly, as for the VHF signal component, a signal component in the vicinity of the selected channel is selected by the BPF 20 serving as a VHF input tuning circuit, limited to a predetermined level range by the high frequency amplifier circuit 21, and further the VHF interstage tuning circuit. After being detuned in the BPF 22, the signal is supplied to the mixing circuit 23. The mixing circuit 23 includes a local oscillator circuit 2
The local oscillation signal from 4 is given. The local oscillation signal is also given to the PLL circuit 4, and the P
In response to the tuning signal, the LL circuit 4 changes the control voltage to the resonance circuit 25 provided in association with the local oscillation circuit 24, and changes the resonance frequency of the resonance circuit 25.

The intermediate frequency signals from the mixing circuits 13 and 23 are amplified in the intermediate frequency amplifying circuit 3 and then given to the subsequent I and Q demodulating circuits. The control voltage is also output from the PLL circuit 4 to the BPFs 10, 12; 20, 22. By selectively switching the output of this control voltage to the resonance circuit 15 and the resonance circuit 25, it is possible to switch between reception in the UHF band and reception in the VHF band.

[0006] Further, the low channel of the VHF band and hi
Switching to the gh channel is performed by setting the resonance circuit 25 to the resonance capacitance Cd and the resonance capacitance Cd as shown in FIG.
And a series inductor L1 and L2 connected in parallel with each other, and realized by opening or shorting a switch SW such as a diode between terminals of the inductor L2 in response to a band switching signal from the tuning circuit. To be done.

[0007]

The television receiver configured as described above is a so-called super-heterodyne type receiver, and BPFs 10, 12; 20, 22.
In addition to selecting only the signal component of the reception frequency band,
It also has a function of eliminating image interference generated in the mixing circuits 13 and 23. For example, when receiving 13 channels (center frequency 473 MHz) in Japan, the frequency of the local oscillation signal is 530 MHz, which is the center frequency of 473 MHz plus the frequency 57 MHz of the intermediate frequency signal. The frequency is 587 MHz obtained by adding the intermediate frequency to the local oscillation frequency. Therefore, the BPFs 10 and 12 are required to have a filtering characteristic of passing a component of 473 ± 3 MHz and blocking a component of 587 ± 3 MHz, and this relationship is required for all channels.

Therefore, the BPFs 10, 12; 20,
Reference numeral 22 denotes a VCF (Voltage Controled Filer) capable of changing the center frequency according to the applied voltage, and the local oscillation circuits 14 and 24 including the resonance circuits 15 and 25 respectively correspond to the applied voltage. VCO (Voltage Controled Osc)
illator), and all are controlled by the same control voltage. These VCFs and VCOs are configured by including variable capacitance diodes and the like, and the relationship between their center frequency and oscillation frequency is as shown in FIG. 7 in the UHF band, for example, and the change in the control voltage It must be a linear function separated by the intermediate frequency of 57 MHz.

Here, Table 1 shows channel allocation in Japan, Europe, and the United States.

[0010]

[Table 1]

In analog broadcasting, it is not possible to carry out broadcasting on the same channel between mutually adjacent service areas. Therefore, as shown in Table 1, a large number of channels are allocated to television broadcasting. Therefore, the television receiver is also required to have a very wide reception bandwidth, and in particular, for the VHF channel, the resonance circuit 25 has
As shown in FIG. 8, it is necessary to use an air core coil having a large inductance. This air-core coil has a shape in which a conductor such as a copper wire is spirally wound, and the relationship shown in FIG. 7 is satisfied by mechanically adjusting the spacing between the windings. Variations in the air-core coil and the variable capacitance diode are adjusted. However, this air-core coil has a problem in that its shape is likely to be distorted and its inductance is likely to change due to mechanical vibration.

For example, when the PLL circuit 4 is locked,
When the frequency fluctuation value of the local oscillation signal when a constant vibration is given to the receiver is measured, it is 1 in peak to peak.
It may fluctuate by as much as 20 kHz, and depending on the setting of the loop band of the PLL loop, there is a possibility that lock may be lost. In the case of digital broadcasting, fluctuations in the intermediate frequency due to such fluctuations in the local oscillation frequency adversely affect the digital demodulation circuit in the subsequent stage, and in some cases cause bit errors and burst errors due to loss of synchronization, resulting in video and audio. There is a problem of causing disorder and freeze.

In this respect, generally, when the frequency fluctuation width of the oscillation circuit becomes wide, the response to the frequency change must be made high, and the phase noise increases in the oscillation signal, leading to the deterioration of the bit error rate, for example. There is.
Therefore, in the multi-channel analog television broadcasting as shown in Table 1, the frequency band is narrowed due to an increase in the number of programs accommodated per channel due to digitization and a common channel due to the adoption of the OFDM modulation method. However, the transition period from the start of digital broadcasting to the end of analog broadcasting must be received over a wide band as in the past.

On the other hand, by converting the frequency of the received high frequency signal,
Obtaining a direct baseband signal, the so-called direct conversion method has a small number of parts, and has the advantage that there is no image interference that occurs in the case of the superheterodyne method described above, there is a problem that there is a lot of adjacent interference, Although it could not be applied to a receiver for analog broadcasting, it can be applied to a receiver for digital broadcasting that is strong against the adjacent interference. However, the local oscillation frequency is 93 + 57 = 150 MH in the case of the above-mentioned super-heterodyne system, for example, in the case of the first channel in Japan.
In contrast to z, the center frequency of the received high frequency signal is equal to 93 MHz, and the resonance circuit 25 requires a large inductance, which is not applicable to a terrestrial digital television broadcast receiver.

It is an object of the present invention to provide a digital broadcast receiving apparatus which can obtain stable operation over a wide band.

[0016]

[Means for Solving the Problems] A digital broadcasting receiver of the present invention.
In order to solve the above problems, the tuner circuit of the communication device
Of the high frequency signals received by the input terminal, the tuning that should be received
Tracking filter that outputs channel signal component
And a signal corresponding to the frequency of the tuning channel to be received
A local oscillation circuit for outputting a certain local oscillation signal;
Oscillation signal and the signal output by the tracking filter
Direct mixing of baseband signals by mixing with the components
And a mixing circuit for outputting the local oscillation circuit,
An oscillator that oscillates a partial oscillation signal, and the oscillator oscillates
Decrease the frequency of the local oscillation signal to reduce the local oscillation signal.
And a frequency lowering means for outputting to the mixing circuit.
Characterize. In addition, the digital broadcast receiving apparatus of the present invention
The tuner circuit, in addition to the above configuration,
Divide the wave number band into multiple, and for each separated frequency band
Equipped with a band separation filter that outputs the above high-frequency signal,
Separate the tracking filter and the mixing circuit above.
It is configured to have multiple units according to multiple frequency bands
One local oscillator circuit outputs a local oscillator signal to each mixing circuit.
It is characterized by

[0017]

[0018]

Further, the digital broadcast receiving apparatus of the present invention
In the tuner circuit, in addition to the above configuration, the frequency lowering unit is a frequency dividing unit.

According to the above construction, the frequency of the local oscillation signal can be lowered relatively easily, and the actual oscillation frequency of the local oscillation means as described above is mechanically shifted by shifting the oscillation frequency higher than the tuning frequency. It is possible to easily use an extremely stable element.

Furthermore, the digital broadcast receiving apparatus of the present invention
In addition to the above- mentioned configuration, the tuner circuit of the above-mentioned type is characterized in that the frequency dividing means has a plurality of frequency dividing ratios.

According to the above construction, the constant reception frequency range can be divided into a plurality of bands, the variable range of the oscillation frequency of the local oscillation means can be reduced, and the phase noise can be suppressed. It is suitable for receiving broadcasts.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Regarding one embodiment of the present invention,
The following is a description with reference to FIGS. 1 to 4.

FIG. 1 is a block diagram showing an electrical configuration of a tuner section of a digital broadcast television receiver according to an embodiment of the present invention. The received high frequency signal input from the input terminal 31 connected to the antenna or the CATV cable is separated into the UHF signal component and the VHF signal component in the band separation filter 32, and is supplied to the band pass filters 40 and 50.

As for the UHF signal component, a signal component in the vicinity of the selected channel is selected by the BPF 40 that serves as a UHF input tuning circuit, is limited to a predetermined level range by the high frequency amplifier circuit 41, and further serves as a UHF interstage tuning circuit. Is applied to the mixing circuit 43 after being retuned in. The local oscillation signal from the local oscillation circuit 34 is given to the mixing circuit 43. The local oscillation signal is also applied to the PLL circuit 35, and the PLL circuit 3
Reference numeral 5 changes a control voltage to a resonance circuit 36 provided in association with the local oscillation circuit 34 in response to a tuning signal provided from a tuning circuit (not shown) such as a microcomputer, and the resonance circuit The resonance frequency of 36 is changed.
Thus, the frequency of the local oscillation signal is stably controlled so as to correspond to the frequency of the broadcasting station to be received.

Similarly, as for the VHF signal component, a signal component in the vicinity of the selected channel is selected by the BPF 50 serving as a VHF input tuning circuit, limited to a predetermined level range by the high frequency amplifier circuit 51, and further the VHF interstage tuning circuit. After being retuned in the BPF 52, the signal is supplied to the mixing circuit 53. The local oscillation signal from the local oscillation circuit 34 is fed to the mixing circuit 53 by a frequency divider 37.
The 1/2 frequency-divided signal divided by 2 and the 1/4 frequency-divided signal further divided by 1/2 by the frequency divider 38 cascade-connected to the frequency divider 37 are used as a changeover switch 39. Is selected and given in. The local oscillation signal is also stably controlled by the PLL circuit 35 as described above, and the PLL circuit 35 is provided in association with the local oscillation circuit 34 in response to the tuning signal. The resonance frequency of the resonance circuit 36 and the switching state of the changeover switch 39 are changed.

The baseband signals from the mixing circuits 43 and 53 are amplified in the amplifier circuit 33 and then given to the digital demodulation circuit in the subsequent stage to be demodulated into I, Q signals and the like. Filter control data is also output from the channel selection circuit such as a microcomputer, and the filter control data is supplied to the analog / digital converters 60 and 61.
Converted into DC control voltage at BPF 40, 42;
50, 52 and the BPF 40, 42; 50, 5
The tracking frequency of 2 is changed.

FIG. 2 shows a local oscillator circuit 34, a resonance circuit 36, frequency dividers 37 and 38, and a changeover switch 3.
It is a block diagram which shows 9 vicinity in detail.

The local oscillation circuit 34 comprises an oscillator 71, frequency dividers 72 and 73, and a changeover switch 74. The oscillator 71 oscillates in the GHz band, and the oscillated signal is frequency-divided by the frequency divider 72 by ½ and supplied to one input of the changeover switch 74, and further ½ by the frequency divider 73. Divided and the changeover switch 74
Given to the other input of. The changeover switch 74 is realized by a diode switch, for example, as shown in FIG. 2, and in response to the tuning signal, the PLL circuit 35 selectively outputs one of the outputs from the two inputs. It is output to the mixing circuit 43. When the 1/2 frequency-divided output of the oscillator 71 output from the frequency divider 72 is directly output, it becomes a local oscillation signal of the UHF high channel, and the 1/4 frequency-divided output of the oscillator 71 output from the frequency divider 73. Is a local oscillation signal of the UHFlow channel.

Further, the 1/4 frequency-divided output is further frequency-divided by the frequency divider 37, and then the changeover switch 39.
Given to. The changeover switch 39 is also realized by a diode switch or the like like the changeover switch 74,
Switching is controlled by the PLL circuit 35. The local oscillation signal of the VHFhigh channel is output from one output of the change-over switch 39 and given to the mixing circuit 53, and the other output of the change-over switch 39 is further divided by 1/2 in the frequency divider 38. Then, it is supplied to the mixing circuit 53 as a local oscillation signal of the VHF Flow channel.

The resonance circuit 36 includes capacitors C1, C2 and
It comprises C3, C4, a variable capacitor Cv, and an inductor L. Variable capacitor Cv
Is realized by a variable capacitance diode or the like, and its capacitance value changes in response to the channel selection signal.

In this way, the frequency of the local oscillation signal of the UHF channel actually input to the mixing circuit 43 is divided into two bands as shown in FIG. 3, and for each band,
It changes in response to a change in the control voltage from the PLL circuit 35 to the variable capacitor Cv. Further, FIG. 3 shows the filter control data as digital / analog converters 60, 6
Control voltage obtained by analog conversion in 1 and BPF4
The relationship with the tracking frequency of 0, 42; 50, 52 is shown. As is clear from FIG. 3, in the present invention, the tracking frequency, that is, the variable range of the reception frequency, is divided into two bands for the local oscillation signal and is in charge of the division.

As described above, since the variable range of the tracking frequency is divided into a plurality of bands to be received by the local oscillation signal, the variable range of the oscillation frequency of the oscillator 71 is reduced,
Responsiveness to frequency changes can be reduced. This makes it possible to suppress phase noise and is suitable for receiving digital broadcasting, and is also suitable for wideband reception during the transition period from the start of digital broadcasting to the end of analog broadcasting.

As described above, in the digital broadcasting television receiver according to the present invention, the local oscillation from the oscillator 71 is performed by using the frequency dividers 72, 73; 37, 38 capable of lowering the frequency relatively easily. Since the signal is divided and input to the mixing circuits 43 and 53, the oscillation frequency of the oscillator 71 is the BPF 40, 42;
In the resonance circuit 36, the oscillation frequency of the oscillator 71 can be shifted higher than the tracking frequency of 0.52, and is set to a frequency in the GHz band higher than the frequency used in normal terrestrial television broadcasting or CATV. A chip inductor as shown in FIG. 4 can be used in place of the air-core coil shown in FIG. 8 as the inductor L, which is the resonance element, and can be less affected by external vibration. As a result, stable operation can be performed over a wide frequency band, and digital broadcasting can be satisfactorily received.

Further, as described above, even if the oscillation frequency of the oscillator 71 of the local oscillation circuit 34 is high, the frequency of the local oscillation signal actually given to the mixing means can be lowered, and the local oscillation signal can be lower than that of the superheterodyne system. A direct conversion method in which the frequency of the oscillation signal is low can be applied, the configuration can be simplified, and image interference can be eliminated.

As the inductor L, a dielectric resonator or a microstrip line may be used in addition to the chip inductor. Further, the frequency division ratio and the number of stages of the frequency divider may be appropriately selected according to the oscillation frequency of the oscillator 71 and the reception frequency bandwidth. According to the above configuration
For example, the frequency of the local oscillation signal is reduced by the frequency reduction means.
Reduced and fed to the mixing means. Therefore, the local
Set the oscillation frequency of the oscillation means to the tuning frequency of the tracking filter.
Can be shifted higher than wave number, normal ground wave
Than frequencies used in television broadcasting and CATV
Use a local oscillator as a frequency in the high GHz range.
Resonance element, chip inductor, dielectric resonator or
Mechanically stable elements such as microstrip lines
Can be used. In this way, the vibration from the outside
Stable over a wide frequency band
It can be operated and can receive digital broadcasts well.
I can believe. In addition, the local oscillator
Even if the oscillation frequency of the stage is high, it is actually given to the mixing means.
The frequency of the local oscillation signal can be lowered,
The frequency of the local oscillation signal is lower than that of the heterodyne method
Direct conversion method can be applied,
The structure can be simplified and image interference can be eliminated.
Further, according to the above configuration, the influence of external vibration
It becomes difficult to receive, and stable operation is performed over a wide frequency band.
And receive good digital broadcasts.
You can Furthermore, as described above, the oscillation of the local oscillation means
Local oscillation actually given to the mixing means even at high frequencies
The frequency of the signal can be lowered, and
The frequency of the local oscillation signal is lower than that of the IN method.
A conversion method can be applied to simplify the configuration.
It can be simplified to eliminate image interference.

[0037]

[Effects of the Invention] The tuner of the digital broadcasting receiver of the present invention.
As described above, the input circuit receives the high frequency signal received by the input terminal.
Output the signal component of the selected channel that should be received.
Tracking filter and the tuning channel to be received
A station that outputs a local oscillation signal that is a signal corresponding to the frequency
Local oscillation circuit, the local oscillation signal, and the tracking filter.
By mixing with the signal component output by
And a mixing circuit for directly outputting a baseband signal,
The local oscillation circuit is an oscillator that oscillates a local oscillation signal.
And lower the frequency of the local oscillation signal oscillated by the oscillator.
The frequency for outputting the local oscillation signal to the mixing circuit.
And a means for reducing the number. In addition, according to the present invention
The tuner circuit of the digital broadcasting receiver is added to the above configuration.
By separating the frequency band of the high-frequency signal into multiple,
Band that outputs the above high-frequency signal for each separated frequency band
Equipped with a band separation filter,
And the above mixing circuit according to the separated multiple frequency bands.
Multiple local oscillator circuits are provided for each mixing time.
A local oscillation signal is output to the road.

[0038]

[0039]

Further, the digital broadcast receiving apparatus of the present invention
In the tuner circuit , as described above, the frequency lowering means is a frequency dividing means that can relatively easily lower the frequency of the local oscillation signal.

Therefore, it is possible to easily enable the use of the mechanically stable element.

Furthermore, the digital broadcast receiver of the present invention
In the above tuner circuit, the frequency dividing means is provided with a plurality of frequency division ratios so as to divide a constant reception frequency range into a plurality of bands.

Therefore, the variable range of the oscillation frequency of the local oscillation means can be reduced to suppress the phase noise, which is suitable for receiving digital broadcasting.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a tuner section of a digital broadcast television receiver according to an embodiment of the present invention.

FIG. 2 is a block diagram showing in detail a local oscillation circuit, a resonance circuit, a frequency divider and the vicinity of a changeover switch in the tuner section of FIG.

FIG. 3 is a graph showing changes in local oscillation frequency and reception frequency with respect to changes in control voltage according to the present invention.

FIG. 4 is a perspective view of a chip inductor which is an example of a resonance element used in the present invention.

FIG. 5 is a block diagram showing an electrical configuration of a tuner unit of a television receiver for analog broadcasting.

6 is an electric circuit diagram for explaining a resonance frequency switching method in the resonance circuit of the tuner unit shown in FIG.

7 is a graph showing changes in the local oscillation frequency and the reception frequency with respect to changes in the control voltage of the tuner unit shown in FIG.

FIG. 8 is a perspective view of an air-core coil which is an example of a resonance element used in the related art.

[Explanation of symbols]

31 input terminals 32 band separation filter 33 amplifier circuit 34 Local oscillation circuit (frequency conversion means) 35 PLL circuit 36 Resonance circuit (frequency conversion means) 37,38; 72,73 divider 39,74 selector switch 40, 42; 50, 52 BPF 41,51 high frequency amplifier 43, 53 mixing circuit (frequency conversion means, mixing means) 60,61 Digital / Analog converter 71 oscillator L inductor (resonant element)

Claims (4)

(57) [Claims] 1. A high frequency signal received by an input terminal is received.
Tracker that outputs the signal component of the channel to be trusted
And Gufiruta is the signal corresponding to the frequency of the to be received tuning channel
The local oscillation circuit that outputs the local oscillation signal, the local oscillation signal, and the tracking filter output
By mixing with the signal components, the baseband signal
A mixing circuit for directly outputting the signal , the local oscillation circuit lowers the frequency of the local oscillation signal oscillated by the oscillator and the oscillator that oscillates the local oscillation signal.
The local oscillation signal to the mixing circuit.
A digital broadcast receiving device characterized by including:
Tuner circuit . 2. The digital broadcast receiving apparatus according to claim 1, wherein the frequency lowering unit is a frequency dividing unit .
Tuner circuit . 3. The digital broadcast receiving apparatus according to claim 2, wherein the frequency dividing means has a plurality of frequency dividing ratios .
Tuner circuit . 4. The frequency band of the high frequency signal is separated into a plurality of frequency bands.
And output the above high frequency signal for each separated frequency band
And a band separation filter that separates the tracking filter and the mixing circuit.
A single local oscillation circuit outputs a local oscillation signal to each mixing circuit by configuring multiple configurations according to multiple frequency bands
The digital broadcast reception according to claim 1, characterized in that
The tuner circuit of the device.