CN1152562C - TV. tuning component - Google Patents
TV. tuning component Download PDFInfo
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- CN1152562C CN1152562C CNB011186984A CN01118698A CN1152562C CN 1152562 C CN1152562 C CN 1152562C CN B011186984 A CNB011186984 A CN B011186984A CN 01118698 A CN01118698 A CN 01118698A CN 1152562 C CN1152562 C CN 1152562C
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Abstract
A television tuner is provided with a differential mixer having two transistors to which a local oscillation signal and a received television signal are inputted, and an intermediate frequency amplifier for amplifying an intermediate frequency signal outputted from the mixer. A signal attenuating means is arranged at the output side of the intermediate frequency amplifier. Then, the local oscillation signal and the television signal are inputted to the base of one of those two transistors, and the base of the other transistor is grounded like high frequencies, and a fixed bias voltage is applied to the base of the other transistor, and the same voltage as the fixed bias voltage or a voltage different from the fixed bias voltage is applied to the base of one transistor. At the time of receiving the television signal at a specific channel, the different voltage is applied to the base of one transistor, and the attenuating frequencies of the signal attenuating means are made coincident with the frequencies of the local oscillation signal at the specific channel.
Description
Technical field
The present invention relates to reduce the deformation that produces by frequency mixer and can reduce the tv tuning component that oscillation signals according is revealed.
Background technology
As shown in Figure 2, formerly a kind of tv tuning component in the technology has frequency mixer 31, oscillation signals according generator 32 and intermediate frequency amplifier 33.After through various synchronous circuits and high-frequency amplifier (all not shown among the figure) processing, needed TV signal inputs to frequency mixer 31.Oscillation signals according by 32 outputs of oscillation signals according generator also inputs to this frequency mixer 31.The TV signal that inputs to frequency mixer 31 and oscillation signals according are implemented frequency compounding, be transformed into after the intermediate-freuqncy signal again by frequency mixer 31 outputs.And, can utilize 33 pairs of intermediate-freuqncy signals of intermediate frequency amplifier to implement to amplify.
Frequency mixer 31 has the frequency compounding transistor (not shown) that is applied with fixed bias voltage to base stage usually, and TV signal and oscillation signals according input to this base stage.Can utilize frequency compounding with transistorized nonlinear characteristic (secondary deformation), TV signal is implemented frequency translation.
Formerly this frequency mixer in the technology is a kind of parts that utilize the secondary deformation behavior to implement operation, yet frequency compounding also can have high order deformation except that secondary deformation with transistor.Therefore, when as the TV signal of received signal and other signal (being not limited in TV signal) when inputing to frequency mixer in the lump, frequency mixer also will produce some other unwanted signal outside the needed intermediate-freuqncy signal, in the time of within these signals are created in the intermediate-freuqncy signal frequency band, these signals just constitute interference signal.
If for instance, for the television system of using in China, the vision carrier frequency of the 3rd channel is 65.75MHz, and local oscillation frequency is 103.75MHz.The SIF sound intermediate frequency frequency is 31.5MHz, the vision intermediate frequency frequency is 38.0MHz, when the signal of the 3rd channel is implemented to receive, if also unwanted to some extent, the frequency of input is the signal of 73.75MHz, will produce frequency owing to three deformation of frequency mixer and be 35.75MHz, unwanted signal.Sort signal occurs in the medium-frequency band, so be a kind of interference signal.Aforesaid example only for illustrating, may differ from one another owing to input to the frequency of the undesired signal of frequency mixer, so this interference signal often also can take place when the signal of nonspecific channel is implemented to receive.
Because the size of the interference signal that produces, determine with transistorized working point to frequency compounding with transistorized nonlinear characteristic and assignment by employed frequency compounding, in a single day so when interference signal being arranged, just can not in time implement change with transistor and working point, and can't eliminate or reduce interference signal frequency compounding.
Summary of the invention
The present invention is exactly the invention that addresses the above problem usefulness, and its purpose is to provide a kind of and can reduces the interference signal that is produced by frequency mixer and can reduce the tv tuning component that oscillation signals according is revealed.
In order to address the above problem, the invention provides a kind of tv tuning component, this tv tuning component have include two transistorized, can import oscillation signals according and as the differential-type frequency mixer of the TV signal of received signal, and can be to the intermediate frequency amplifier of implementing by the intermediate-freuqncy signal of described frequency mixer output to amplify, and also be provided with the signal attenuation assembly at the outlet side of described intermediate frequency amplifier, described oscillation signals according and described TV signal input to a transistorized base stage in described two transistors, and the base stage high frequency earthing on another transistor, fixing bias voltage is applied to base stage on described another transistor, when the TV signal that is positioned at the certain tones road is implemented the signal reception, can apply to the base stage on the described transistor and the unequal voltage of described fixed bias voltage, and make the frequency of fadings of described signal attenuation assembly consistent with the oscillation signals according frequency of described specific channel.
And, tv tuning component provided by the present invention, can also further between base stage on the described transistor and earth point, be provided with the series circuit that constitutes by resistor and switch module, thereby can work as when the TV signal that is positioned at described specific channel implemented signal and receive, make described switch module be in conducting state.
And, tv tuning component provided by the present invention, can also further make described signal attenuation assembly be provided with inductance element, capacitor and the switching diode that is being connected with described capacitors in series, described capacitor that is being connected in series and switching diode and described inductance element are connected in parallel, thereby can work as when the TV signal that is positioned at described specific channel implemented signal and receive, make described switching diode be in conducting state, and make the parallel resonance frequency that produces by described inductance element and described capacitor, consistent with the local oscillation frequency of described specific channel.
And tv tuning component provided by the present invention, described switch module are negative pole-positive pole-negative-type transistor, and this transistorized collector electrode is connected with negative electrode on the described switching diode.
Description of drawings
Fig. 1 is the schematic circuit of a kind of tv tuning component of the present invention.
Fig. 2 is the schematic circuit of a kind of tv tuning component of technology formerly.
Embodiment
As shown in Figure 1, the TV signal that receives by not shown antenna after handling through synchronous circuit and high-frequency amplifier (not shown), is transformed into needed TV signal and inputs to frequency mixer 1.Oscillation signals according by 2 outputs of oscillation signals according generator also inputs to frequency mixer 1.
Frequency mixer 1 has two transistor 1a, 1b, thereby constitute a kind of differential-type frequency mixer, bias voltage is applied to the base stage of transistor 1a by bias resistor 1c, 1d, and bias voltage also is applied to the base stage of transistor 1b by bias resistor 1e, 1f.The bias voltage that is applied to these two base stages is mutually the same.Two transistorized emitters are connected to each other by resistor 1 g, and these two emitters also are connected with constant-current supply.
Base stage on the transistor in two transistors is also by resistor 3, and is connected as the collector electrode on the negative pole-positive pole-negative-type transistor 4 of switch module.The resistance value of resistor 3 can be implemented to adjust according to needs.Emitter on negative pole-positive pole-negative-type transistor 4 is connected with earth point.The voltage that external power source 6 provides can pass through diverter switch 5, is applied to the base stage on negative pole-positive pole-negative-type transistor 4.
Collector electrode on transistor 1a, the 1b is connected with loading resistor 1h, 1i respectively.
As the TV signal and the oscillation signals according of needed received signal, input to the base stage of a transistor 1a, and the base stage on another transistor 1b is by direct-current blocking-up capacitor 1j high frequency earthing.Signal by the output of the collector electrode on negative pole-positive pole-negative-type transistor 1a, 1b is the intermediate-freuqncy signal of mutual balance.Therefore, frequency mixer 1 can be used as the frequency mixer use of a kind of input signal imbalance, output signal balance.
Intermediate-freuqncy signal by frequency mixer 1 output is implemented to amplify by intermediate frequency amplifier 7.Intermediate frequency amplifier 7 has main amplifier 7a, and the emitter follower type transistor 7b that uses as buffer amplifier, and the emitter on the transistor 7b is by resistor 7c DC earthing.
The emitter of transistor 7b is connected with trap circuit 8 as the signal attenuation assembly, and intermediate-freuqncy signal exports lead-out terminal 9 to after by trap circuit 8 again.
For the aforesaid this structure form of the composition, the base stage of negative pole-positive pole-negative-type transistor 4 is in the blocking state that is not connected with external bias power supply 6 usually, and is applied in identical substantially bias voltage on each base stage on transistor 1a, the 1b.Therefore, the voltage between the collector and emitter on the transistor 1a equates substantially with the voltage that transistor 1b goes up between the collector and emitter.Both collector currents also equate under the effect in continuous current source substantially.
The dc point of transistor 1a equates each other substantially with the dc point of transistor 1b, so can be in balance operating state completely.Input to the needed TV signal of base stage on the transistor 1a, will implement frequency compounding with oscillation signals according, and be transformed to intermediate-freuqncy signal.
At this moment, transistor 1a and 1b are in the balance operating state, TV signal of being imported and oscillation signals according are the phase cancellation state, so frequency mixer 1 will can not be exported the secondary high frequency waves (is exactly to appear at two even high frequency waves between the collector electrode on transistor 1a, the 1b if more correctly say) of these signals.Therefore, the circuit that is positioned at thereafter all will can not be subjected to the interference of these secondary high frequency waves.And, because the current potential of high frequency waves is quite low more than three times, so even also can not produce harmful effect from tuning block output.Because switching diode 8b is in blocking state, so intermediate-freuqncy signal will be implemented output by inductance element 8a.
Yet, being in the TV signal (needed TV signal) of implementing the signal receiving channels usually, other undesirable TV signal input to frequency mixer 1 in the lump with a little often.For this situation, the signal that inputs to frequency mixer 1 will comprise needed TV signal, other undesirable TV signal and be positioned at the oscillation signals according of received signal channel.According to the deformation behavior more than three times of transistor 1a, 1b, these three signals will produce the signal that makes new advances.And, if this new signal occurs within the intermediate frequency signal band, will become interference signal.
In general, the deformation by the transistor nonlinear characteristic produces can change along with the transistor DC disturbances of power.In other words be exactly that when collector current and collector electrode and emission voltage across poles change, this deformation also will change.
In the time may having produced described new signal (so-called interference signal), the voltage that external power source 6 provides can be applied to the base stage on negative pole-positive pole-negative-type transistor 4, and make it be in conducting state.At this moment, switching diode 8b also will be in conducting state.When negative pole-positive pole-when negative-type transistor 4 is in conducting state, base stage on the transistor 1a will be connected with earth point by resistor 3, so its voltage will descend, thereby can make the collector current of transistor 1a and the collector current of transistor 1b, be the reciprocal different value of increase and decrease direction.Because these two collector currents are the value that differs from one another, so the voltage between each collector electrode and emitter also will be the reciprocal different value of increase and decrease direction.In other words be exactly that their dc point differs from one another.
Because by resistor 3 variable quantity of these electric currents and voltage is implemented to adjust, thus can be that minimizing mode is determined this working point according to the current potential that makes the interference signal that may have problems, and in view of the above the bias voltage of transistor 1a is implemented to set.
This mode can reduce from the interference signal of frequency mixer 1 output, but the poised state of frequency mixer 1 self is with destroyed.Consequently, the oscillation signals according of being imported will not carried out under the state of phase cancellation completely by frequency mixer 1 output.If make the parallel resonance frequency that forms by inductance element 8a in the trap circuit 8 and capacitor 8c, the oscillation signals according of implementing the signal receiving channels is consistent with being positioned at, then intermediate frequency amplifier 7 can be implemented decay to the oscillation signals according that leaks out, and does not make it appear at lead-out terminal 9.
And, when the voltage that is applied to the variable capacitance diode two ends being implemented to change with variable capacitance diode replacement capacitor 8c, also can be to producing other channel of interference signal, the decay of the oscillation signals according that enforcement leaks out.
Claims (4)
1. tv tuning component, it is characterized in that having include two transistorized, can import oscillation signals according and as the differential-type frequency mixer of the TV signal of received signal, and intermediate frequency amplifier to implementing by the intermediate-freuqncy signal of described frequency mixer output to amplify, and also be provided with the signal attenuation assembly at the outlet side of described intermediate frequency amplifier, described oscillation signals according and described TV signal input to a transistorized base stage in described two transistors, and the base stage high frequency earthing on another transistor, fixing bias voltage is applied to base stage on described another transistor, when the TV signal that is positioned at the certain tones road is implemented the signal reception, base stage on a described transistor applies and the unequal voltage of described fixed bias voltage, and makes the frequency of fadings of described signal attenuation assembly consistent with the oscillation signals according frequency of described specific channel.
2. tv tuning component as claimed in claim 1, it is characterized in that between base stage on the described transistor and earth point, also being provided with the series circuit that constitutes by resistor and switch module, when the TV signal that is positioned at described specific channel was implemented the signal reception, described switch module was in conducting state.
3. tv tuning component as claimed in claim 1 or 2, it is characterized in that described signal attenuation assembly has inductance element, capacitor and the switching diode that is being connected with described capacitors in series, described capacitor that is being connected in series and switching diode and described inductance element are connected in parallel, when the TV signal that is positioned at described specific channel is implemented the signal reception, described switching diode is in conducting state, and make the parallel resonance frequency that constitutes by described inductance element and described capacitor, consistent with the oscillation signals according frequency of described specific channel.
4. tv tuning component as claimed in claim 3 is characterized in that described switch module is negative pole-positive pole-negative-type transistor, and this transistorized collector electrode is connected with negative electrode on the described switching diode.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP187513/2000 | 2000-06-19 | ||
| JP2000187513A JP3723723B2 (en) | 2000-06-19 | 2000-06-19 | Television tuner |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1330489A CN1330489A (en) | 2002-01-09 |
| CN1152562C true CN1152562C (en) | 2004-06-02 |
Family
ID=18687482
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB011186984A Expired - Fee Related CN1152562C (en) | 2000-06-19 | 2001-06-11 | TV. tuning component |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP3723723B2 (en) |
| CN (1) | CN1152562C (en) |
-
2000
- 2000-06-19 JP JP2000187513A patent/JP3723723B2/en not_active Expired - Fee Related
-
2001
- 2001-06-11 CN CNB011186984A patent/CN1152562C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2002010154A (en) | 2002-01-11 |
| JP3723723B2 (en) | 2005-12-07 |
| CN1330489A (en) | 2002-01-09 |
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| C10 | Entry into substantive examination | ||
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| C06 | Publication | ||
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| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20040602 Termination date: 20120611 |