JPH04165881A - Television tuner - Google Patents

Abstract

PURPOSE:To operate the reception of both a television broadcast and a satellite broadcast by almost the same system at the time of receiving the television broadcast and the satellite broadcast by constituting a voltage control oscillator in order to operate a phase lock operation at the time of selecting the first intermediate frequency signal of the satellite broadcast, and in order to FM-demodulate the second intermediate frequency signal of the satellite broadcast. CONSTITUTION:At the time of selecting the satellite broadcast, the second intermediate frequency signal being the output of a frequency converting part B is operated for a prescribed processing by a second intermediate frequency processing part D, and then introduced to a PLL loop part E. The second intermediate frequency signal is FM-demodulated by this loop part E after operating the phase lock operation, and the signal of a base band obtained by the FM demodulation is supplied through a loop filter 13 to an output terminal (t)3 for the satellite broadcast. Thus, both the television broadcast and the satellite broadcast can be received, and the frequency converting part B and the PLL loop part E are shared by using them for the different processings at the time of receiving both the television broadcast and the satellite broadcast, so that both the television broadcast and the satellite broadcast can be received by almost the same system, and the number of parts can sharply be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a television tuner that receives both television broadcasting and satellite broadcasting.

[Summary of the Invention] The present invention allows a channel selection section to select any signal from each high frequency signal of each channel of television broadcasting and a first intermediate frequency signal of satellite broadcasting, and when the high frequency signal of television broadcasting is selected, When converting into a first intermediate frequency signal of broadcasting, #: is provided with a frequency conversion section that converts into a second intermediate frequency signal of satellite broadcasting when the first intermediate frequency signal of satellite broadcasting is selected, and when a high frequency signal of television broadcasting is selected. The output of the frequency conversion section is passed through a first intermediate frequency processing section for television broadcasting, and when a first intermediate frequency signal for satellite broadcasting is selected, the output of the frequency conversion section is passed through a second intermediate frequency processing section for satellite broadcasting. The PLL loop section is configured to be able to open the loop, and when selecting a high frequency signal for television broadcasting, the voltage controlled oscillator is used as a fixed frequency oscillator to convert the first intermediate frequency signal of television broadcasting to a second intermediate frequency signal. When the first intermediate frequency signal of satellite broadcasting is selected, the second intermediate frequency signal of satellite broadcasting is FM demodulated by performing a phase lock operation, thereby converting the high frequency signal of television broadcasting into the first intermediate frequency signal. The frequency converter shares the conversion from the first intermediate frequency signal of the television broadcast to the second intermediate frequency signal, and the conversion from the first intermediate frequency signal of the television broadcast to the second intermediate frequency signal and the conversion of the satellite broadcast from the first intermediate frequency signal to the second intermediate frequency signal. Since the FM demodulation of the second intermediate frequency signal is shared by the PLL loop section, a television tuner for both television broadcasting and satellite broadcasting can be constructed at low cost and in a small space with a small number of parts.

[Prior Art] In order to obtain television broadcasts such as VHF broadcasts and UHF broadcasts with high image quality, a double super one type television tuner as shown in FIG. 3 is being put into practical use.

In FIG. 3, the channel selection section A includes a plurality of band pass filters BP, -BP connected in parallel, and a plurality of switches SW□ -SW for selecting these.

and a switch S corresponding to the selected channel.
It is configured to turn on only W1 to SW, n to pass only the high frequency of the frequency corresponding to the selected channel. The high frequency signal selected by this channel selection section A is guided to a first mixer 20 via an automatic gain control circuit 1 and an amplifier 2. A first local oscillation signal is introduced from the first local oscillator 21 to the first mixer 20, and the first mixer 20 receives the first local oscillation signal from the first local oscillator 21.
The high frequency signal is converted into a first intermediate frequency signal based on the local oscillation signal. This first intermediate frequency signal is guided to a second mixer 24 via a bandpass filter 22 and an amplifier 23. A second local oscillation signal is introduced from a second local oscillator 25 to the second mixer 24, and the second mixer 24 converts the first intermediate frequency signal into a second intermediate frequency signal based on the second local oscillation signal. The second intermediate frequency signal output from the second mixer 24 is transmitted to the amplifier 26 and the bandpass filter 2.
7 to the next stage.

On the other hand, as a television tuner for satellite broadcasting, the one shown in FIG. 3 has been put into practical use. In FIG. 3, a high frequency signal of satellite broadcasting is converted into a first intermediate frequency signal by a BS converter, and this first intermediate frequency signal is guided to an input terminal t1. The first intermediate frequency signal introduced to the input terminal t1 is introduced to the mixer 3 via a bandpass filter 28, an automatic gain control circuit 29, and an amplifier 30. A second local oscillation signal is introduced from the local oscillator 4 to the mixer 3, and the mixer 3 converts the first intermediate frequency signal into a second intermediate frequency signal based on the second local oscillation signal.

This second intermediate frequency signal is transmitted to the amplifier 31. The signal is guided to an FM demodulator 35 via a bandpass filter 32, an automatic gain control circuit 33, and an amplifier 34. This FM demodulation section 35 is constituted by a PLL loop consisting of a mixer 36, an amplifier 37, a loop filter 38, and a voltage controlled oscillator 39, and performs FM demodulation of the second intermediate frequency signal. The baseband signal obtained by FM demodulation is supplied to the next stage via an amplifier 40.

[Problems to be Solved by the Invention] A conventional television tuner that receives both television broadcasting and satellite broadcasting has a circuit for television broadcasting as shown in Fig. 2 and a circuit for satellite broadcasting as shown in Fig. 3. It is configured by simply arranging the circuits in parallel. Therefore, compared to a television tuner that can only receive either television broadcasts or satellite broadcasts, it simply requires twice as many parts, is expensive, and requires a large storage space, and an improvement is desired.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a television tuner that can be constructed at low cost and in a small space by allowing as many common parts as possible to be used in the reception of television broadcasts and satellite broadcasts.

[Means for Solving the Problems] The television tuner of the present invention for solving the above problems has the following features:
a channel selection unit that selects an arbitrary signal from each high frequency signal of each channel of television broadcasting and a first intermediate frequency signal of satellite broadcasting; and when this channel selection unit selects a high frequency signal of television broadcasting, the selected high frequency signal; a frequency conversion unit that converts the signal into a first intermediate frequency signal of television broadcasting, and converts the first intermediate frequency signal of satellite broadcasting into a second intermediate frequency signal of satellite broadcasting when the first intermediate frequency signal of satellite broadcasting is selected; and a mixer.

PL that can be opened from the loop filter and voltage controlled oscillator
A PLL loop that constitutes an L loop, and when the channel selection section selects a high frequency signal for television broadcasting, a first intermediate frequency signal that is an output of the frequency conversion section is released through a first intermediate frequency processing section for television broadcasting. and converts it into a second intermediate frequency signal of television broadcasting using the voltage controlled oscillator as a fixed frequency oscillator, and when the channel selection section selects the first intermediate frequency signal of satellite broadcasting, the output of the frequency conversion section is A certain second intermediate frequency signal is manually input to the PLL input via the second intermediate frequency processing section for satellite broadcasting.
It is equipped with a PLL loop section that performs FM demodulation in the L loop.

[Operation] When a TV broadcasting channel is selected, the channel selection section selects a high frequency signal of the frequency of the selected channel, this high frequency signal is converted into a first intermediate frequency signal by the frequency conversion section, and this first intermediate frequency signal is The signal is guided to the PLL loop section via the first intermediate frequency processing section, and is converted into a second intermediate frequency signal in the PLL loop section. When satellite broadcasting is selected, the channel selection section selects the first intermediate frequency signal of the satellite broadcasting, and this first intermediate frequency signal is converted to the second intermediate frequency signal by the frequency conversion section.
is converted into an intermediate frequency signal, and this second intermediate frequency signal is converted into a second intermediate frequency signal.
The signal is guided to the PLL loop section via the intermediate frequency processing section, and is FM demodulated in this PLL loop section. Therefore, the frequency converter is used for both the conversion from the high frequency signal of television broadcasting to the first intermediate frequency signal and the conversion from the first intermediate frequency signal of satellite broadcasting to the second intermediate frequency signal, and the first intermediate frequency signal of television broadcasting is The number of parts can be reduced because the PLL loop section is used for both the conversion of the signal to the second intermediate frequency signal and the FM demodulation of the second intermediate frequency signal for satellite broadcasting.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit block diagram of a television tuner showing one embodiment of the present invention. In FIG. 1, a high frequency signal of television broadcasting and a first intermediate frequency signal of satellite broadcasting are supplied to input terminal 1. is connected to the channel selection section. Channel selection section A includes a plurality of bandpass filters BP, ~BP connected in parallel.
, , and a plurality of pairs of switches SW for selecting these
-+~SW1. ．． and each bandpass filter BP
, ~B I), each frequency band of each channel of television broadcasting and the first intermediate frequency band of satellite broadcasting are used as passbands. Then, when a desired channel is selected, the bandpass filters BP1 to BP corresponding to that channel are
, , a pair of switches sw, , -sw, , are turned on. The signal selected by the channel selection section is guided to a mixer 3 via an automatic gain control circuit 1 and an amplifier 2. A local oscillation signal is guided to this mixer 3 from a local oscillator 4, and the local oscillator 4 converts the high frequency signal of the television signal into a first intermediate frequency signal when television broadcasting is selected, or satellite broadcasting when satellite broadcasting is selected. The frequency of the local oscillation signal is controlled to convert the first intermediate frequency signal into a second intermediate frequency signal, respectively. This mixer 3 and local oscillator 4 constitute a frequency conversion section B. The output of the mixer 3 is selectively guided to either the first intermediate frequency processing section C or the second intermediate frequency processing section via the first selection switch SWl. The first selection switch SWl is controlled to be switched to one terminal, that is, to the first intermediate frequency processing section C side, when television broadcasting is selected, and to the b terminal, that is, the second intermediate frequency processing section side, when satellite broadcasting is selected. . The first intermediate processing section C for television broadcasting is composed of a bandpass filter 5, and the second intermediate processing section for satellite broadcasting is composed of a series circuit of an amplifier 6, a bandpass filter 7, an automatic gain control circuit 8, and an amplifier 9. It is composed of. The respective outputs of the first intermediate frequency processing section C and the second intermediate frequency processing section are led to terminals a and b of a second selection switch SWt, respectively, and the second selection switch SW selects television broadcasting. -, the terminal is switched to the 1 terminal side, and when satellite broadcasting is selected, the terminal is switched to the b terminal side.

The output of the second selection switch SWt is led to the PLL loop section E via the amplifier IO. PLL loop E includes mixer 11, amplifier 12, loop filter 13, loop opening switch SW3, and voltage controlled oscillator 14.
It is composed of L loops. The switch S W a
is controlled to be in the off position when television broadcasting is selected, and to be in the on position when satellite broadcasting is selected. When television broadcasting is selected, the voltage controlled oscillator 14 serves as a fixed frequency oscillator and the mixer 11 outputs a constant local oscillation signal to convert the first intermediate Rw signal of the television broadcast into a second intermediate frequency signal.

The output of the amplifier 12 is passed through a bandpass filter 15 to an output terminal 1. for television broadcasting. The outputs of the loop filter 13 are each led to an output terminal t3 for satellite broadcasting.

The operation of the above configuration will be explained below.

When an arbitrary channel of television broadcasting is selected, as shown by the solid line in FIG. The a terminal position and the switch SW3 of the PLL loop section E are respectively located at the off position. Then, the channel selection section A passes only the high frequency signal having the frequency of the selected channel, and this high frequency signal is converted by the frequency conversion section B into a first intermediate frequency signal. The first intermediate frequency signal, which is the output of the frequency conversion section B, is guided to the PLL loop section E via the first intermediate frequency processing section C. In this PLL loop section E, the voltage controlled oscillator +46 (-) outputs a constant local oscillation signal, the mixer 11 converts the first intermediate frequency signal into a second intermediate frequency signal, and this second intermediate frequency signal is sent to the band pass filter 15. The signal is supplied to an output terminal tt for television broadcasting.

On the other hand, when satellite broadcasting is selected, as shown by the dashed line in FIG.
, are in the on position, the first and second selection switches sw, s
Terminal position of w, switch SW of PLL loop section E
3 are respectively located in the on position. Then, the channel selection section A passes only the first intermediate frequency signal of satellite broadcasting,
This first intermediate frequency signal is converted into a second intermediate frequency signal by the frequency conversion section B. The second output, which is the output of frequency converter B,
The intermediate frequency signal is guided to the PLL loop section E after being subjected to predetermined processing in the second intermediate frequency processing section.

In this PLL loop section E, a phase conflict lock operation is performed to FM demodulate the second intermediate frequency signal, and the baseband signal obtained by FM demodulation is supplied to the output terminal t3 for satellite broadcasting through the loop filter 13. Ru.

In this way, both television broadcasting and satellite broadcasting can be received, and since the frequency conversion section B and PLL loop section E are used for different processing when receiving both, television broadcasting and satellite broadcasting can be received in almost the same system. The number of parts can be significantly reduced.

In this embodiment, since the frequencies of the first intermediate frequency signal for television broadcasting and the second intermediate frequency signal for satellite broadcasting are different,
Selection switch SW, and second selection switch SW! Although the circuit was configured to switch between television broadcasting and satellite broadcasting circuits, if the same frequency band is used, switching of the circuits described above becomes unnecessary, further reducing the number of parts.

[Effects of the Invention] As described above, according to the present invention, the channel selection unit selects any signal from among the high frequency signals of each channel of television broadcasting and the first intermediate frequency signal of satellite broadcasting, and A frequency converter is provided, which converts the high frequency signal into a first intermediate frequency signal of television broadcasting when the high frequency signal is selected, and converts it into the second intermediate frequency signal of satellite broadcasting when the first intermediate frequency signal of satellite broadcasting is selected. When a high frequency signal is selected, the output of the frequency conversion section is passed through a first intermediate frequency processing section for television broadcasting, and when a first intermediate frequency signal for satellite broadcasting is selected, the output of the frequency conversion section is passed through a second intermediate frequency processing section for satellite broadcasting. The first intermediate frequency signal of the television broadcast is guided to the PLL loop section through the processing section, and the PLL loop section is configured to be able to open the loop, and when selecting the high frequency signal of the television broadcast, the voltage controlled oscillator is used as a fixed frequency oscillator to generate the first intermediate frequency signal of the television broadcast. is converted into a second intermediate frequency signal, and when the first intermediate frequency signal of satellite broadcasting is selected, a phase lock operation is performed and the second intermediate frequency signal of satellite broadcasting is FM demodulated. Since the frequency conversion section and the PLL loop section are both used for different processing when receiving the data, it is possible to perform both receptions using almost the same system, reducing the number of parts, resulting in a cost-effective and space-saving configuration. play.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of a television tuner showing an embodiment of the present invention, and FIGS. 2 and 3 are circuit block diagrams of a television tuner showing conventional examples, respectively. A...Channel selection section, B...Frequency conversion section, C
...First intermediate frequency processing unit for television broadcasting, D...Second intermediate frequency processing unit for satellite broadcasting, E...PLL loop channel, 3.11...Mixer, 13...Loop filter ,
14...Voltage controlled oscillator.

Claims (1)

[Claims] (1) A channel selection section that selects any signal from among the high frequency signals of each channel of television broadcasting and the first intermediate frequency signal of satellite broadcasting, and selects when this channel selection section selects the high frequency signal of television broadcasting. a frequency converter that converts the high frequency signal into a first intermediate frequency signal for television broadcasting, and converts it into a second intermediate frequency signal for satellite broadcasting when the first intermediate frequency signal for satellite broadcasting is selected; a mixer; and a loop filter. and a voltage controlled oscillator to form an openable PLL loop, and when the channel selection section selects a high frequency signal for television broadcasting, the first intermediate frequency signal that is the output of the frequency conversion section is subjected to first intermediate frequency processing for television broadcasting. The voltage controlled oscillator is used as a fixed frequency oscillator to convert into a second intermediate frequency signal of television broadcasting, and the channel selection section selects a first intermediate frequency signal of satellite broadcasting. In some cases, the second intermediate frequency signal, which is the output of the frequency conversion section, is input to the PLL input via a second intermediate frequency processing section for satellite broadcasting, and the PLL loop section demodulates the frequency in the PLL loop. TV tuner.