GB2312345A - Tuner and image trap circuit for TV with common frequency control - Google Patents
Tuner and image trap circuit for TV with common frequency control Download PDFInfo
- Publication number
- GB2312345A GB2312345A GB9707390A GB9707390A GB2312345A GB 2312345 A GB2312345 A GB 2312345A GB 9707390 A GB9707390 A GB 9707390A GB 9707390 A GB9707390 A GB 9707390A GB 2312345 A GB2312345 A GB 2312345A
- Authority
- GB
- United Kingdom
- Prior art keywords
- frequency
- image
- capacitor
- trap
- input circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/16—Circuits
- H04B1/26—Circuits for superheterodyne receivers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
- H04N5/50—Tuning indicators; Automatic tuning control
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/12—Bandpass or bandstop filters with adjustable bandwidth and fixed centre frequency
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/17—Structural details of sub-circuits of frequency selective networks
- H03H7/1708—Comprising bridging elements, i.e. elements in a series path without own reference to ground and spanning branching nodes of another series path
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/17—Structural details of sub-circuits of frequency selective networks
- H03H7/1741—Comprising typical LC combinations, irrespective of presence and location of additional resistors
- H03H7/175—Series LC in series path
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/17—Structural details of sub-circuits of frequency selective networks
- H03H7/1741—Comprising typical LC combinations, irrespective of presence and location of additional resistors
- H03H7/1758—Series LC in shunt or branch path
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
- H03J3/00—Continuous tuning
- H03J3/02—Details
- H03J3/16—Tuning without displacement of reactive element, e.g. by varying permeability
- H03J3/18—Tuning without displacement of reactive element, e.g. by varying permeability by discharge tube or semiconductor device simulating variable reactance
- H03J3/185—Tuning without displacement of reactive element, e.g. by varying permeability by discharge tube or semiconductor device simulating variable reactance with varactors, i.e. voltage variable reactive diodes
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/16—Circuits
- H04B1/18—Input circuits, e.g. for coupling to an antenna or a transmission line
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Multimedia (AREA)
- Computer Networks & Wireless Communication (AREA)
- Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)
- Noise Elimination (AREA)
- Channel Selection Circuits, Automatic Tuning Circuits (AREA)
Description
2312345 INPUT CIRCUIT FOR A TELEVISION TUNER The present invention relates
to an input circuit for a television tuner, including an image-trap circuit for eliminating image frequencies which act as disturbance waves to a target resonant frequency.
In general, according to television tuners and so forth, by mixing a desired reception frequency with a local oscillating frequency which is higher by an intermediate frequency, the intermediate frequency can be obtained. When a reception frequency (image frequency) which is higher than the local oscillating frequency by an intermediate frequency is inputted, image disturbance occurs.
Fig. 3 shows a basic input circuit 1 for a conventional television tuner. Among signals received through an antenna 2, a VHF band (40 to 470 MHz) is extracted by a VHF-band selection filter (IF filter) 3, and is applied to a high frequency amplifier circuit 4 via a coupling capacitor Cl and the input circuit 1. In the input circuit 1, ends of variable inductors Ll and L2 are connected to the coupling capacitor Cl, and the other end of the inductor Ll is connected to ground via a capacitor C2. The other end of the inductor L2 is connected to ground via a varactor diode VD1, and is connected to the high frequency amplifier circuit 4 via a varactor diode VD2. Both ends of the connected variable inductor L2 and varactor diode VD2 are connected in parallel to a capacitor C3.
The ratio of minimum frequency to maximum frequency of the VHF band (40 to 470 MHz) is large. Thus, in accordance with whether a desired resonant frequency is in a high channel band or a low channel band, by controlling the inductances of the variable inductors Ll and L2 to be small when a high frequency is received and to be large when a low frequency is received, tuning is performed in all the bands.
Also, by controlling the capacitances of the varactor diodes VD1 and VD2 to be small when a high frequency is received and to be large when a low frequency is received, matching of impedance at a desired frequency is performed. As shown in Fig. 4, by connecting the capacitor C3 in parallel to the series circuit of the variable inductor L2 and the varactor diode VD2, an image-trap circuit which traps image frequencies acting as disturbance waves to a ddsired resonant frequency is formed.
However, according to the conventional input circuit 1, the capacitor C3 is connected in parallel to the series circuit of the inductor L2 and the varactor diode VD2 in order to form the image-trap circuit. However, this arrangement makes it extremely difficult to control the camacitance of the capacitor C3, and as a result, disadvantageous image disturbance occurs. In other words, 1) by increasing the capacitance of the capacitor C3, the variable range of the image-trap frequency can.be widened but the variable range cannot be extended to a high frequency. Because the variable inductors L1 and L2 are tuned to have small inductances when a high frequency is received, the capacitor C3 is connected in parallel to the variable inductor L2 having.small inductance, and the target image-trap frequency is higher than the reception resonant frequency by twice the intermediate frequency. Thus, under these conditions, in order to tune to the target image-trap frequency, the capacitance of the capacitor C3 must be reduced.
2) However, reducing the capacitance of the capacitor C3 narrows the variable range of the image-trap frequency, which makes it difficult to tune the image-tram frequency to the target image frequency.
Accordingly, it is an object of the present invention to provide an input circuit for a television tuner, in which the variable range of an imagetrap frequency can be extended and the image-trap frequency can readily be tuned to the target image frequency.
According to the present invention, the foregoing object is achieved through the provision of an input circuit for a television tuner, in which a series circuit including an image-trap capacitor and a second varactor diode is connected in parallel to a series circuit including a tuning inductor and a first varactor diode, and a common voltage for tuning is applied to the first and second varactor diodes so that their capacitances change, whereby the resonant frequency and the image-trap frequency change.
According to the input circuit for the television tuner, even when the capacitance of the image-trap capacitor is relatively increased, the combined capacitance of the capacitor and the varactor diode can be reduced when a high frequency is received. As a result, the variable range of the image-trap frequency can be extended, and the image-trap frequency can readily be tuned to the target image frequency.
As described above, according to the present invention, by additionally connecting the varactor diode to the imagetrap capacitor, the capacitance of the varactor diode can be changed in accordance with the reception frequency. Thus, even when the capacitance of the capacitor is relatively increased, the combined capacitance of the capacitor and the varactor diode can be reduced when a high frequency is 7487GB received, so that the variable range of the image-trap frequency can be extended, and the image-trap frequency can be tuned to the target image frequency.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
Fig. 1 is a circuit diagram showing an input circuit for a television tuner, according to one embodiment of the present invention; Fig. 2 is an equivalent circuit diagram showing an image trap circuit extracted from the input circuit of Fig. 1; Fig. 3 is a circuit diagram showing a basic pattern of a conventional input circuit for a television tuner; and Fig. 4 is a circuit diagram showing the imagetrap circuit shown in Fig. 3.
By referring to the attached drawings, an embodiment of the present invention will be described below.
Fig. 1 shows a circuit diagram of an input circuit for a television tuner, according to one embodiment of the present invention. The components identical to those in the conventional example are denoted by the same reference numerals.
As shown in Fig. 1, among signals received through an antenna 2, a VHF band (40 to 470 MHz) is extracted by a VHF band selection filter 3, and is applied to a high frequency amplifier circuit 4 via an input circuit la and a coupling capacitor 5. The input terminal 23 of the input circuit la is connected to the output terminal 24 with inductors 6, 7, 8, a capacitor 9, an inductor 10, and a varactor diode 28 provided therebetween, and is connected to the output terminal 24 with an image- trap capacitor 11 and a varactor diode 29 provided therebetween.
The inductors 6 and 7 are connected at a point also is connected to ends of resistors 20, 22, and a capacitor 21 via a diode 13 and an inductor 16. The other end of the resistor 22 is connected to a VHF-low-channel-band selection-voltage-supply terminal 27. The other ends of the resistor 20 and the capacitor 21 are connected to ground. The inductors 7 and 8 are connected at a point also connected to one end of an inductor 12, the other end of the inductor- 12 is connected to ground via a capacitor 18 and is also connected to a VHF-high-channel-band selection-voltagesupply terminal 26 via a resistor 31.
In addition, the point at which the inductor 8 and the capacitor 9 are connected is also connected to the point between the diode 13 and the inductor 16 via the diode 14.
7487GB 7 A reverse voltage supplied via a tuning-voltage supply terminal 25 is applied to the varactor diodes 15 and 28 via a resistor 19, and is applied to the varactor diode 29 via a resistor 30.
At this time, a voltage is selectively applied to the VHF-low-band selection terminal 27 and the VHFhigh-band selection terminal 26. In other words, when a VHF-low-band signal is received, a voltage is selectively applied to the VHF-low-band selection terminal 27, so that the diodes 13 and 14 are switched off. When a VHF-highband signal is received, a voltage is selectively applied to the VHF-high-band selection terminal 26, so that the diodes 13 and 14 are switched on.
Fig. 2 is an equivalent circuit diagram showing an image-trap circuit which is only extracted from the input circuit la shown in Fig. 1. In Fig. 2, the capacitor 9 shown in Fig. 1 is short-circuited since it has a large capacitance and is used to prevent a direct current to flow. In addition, VD represents a combined variable capacitor formed by combining the varactor diode 29 and the capacitor 11 in series, and L is a combined inductor whose inductance can be changed by the diodes 13 and 14.
When the diodes 13 and 14 are switched off, the combined inductor L comprises the inductors 6, 7, 8 and 10 which are connected in series. When the diodes 13 and 14 are switched on, the combined inductor L comprises the inductors 7 and 8 which are short-circuited and the inductors 6 and 10 which are connected in series. In other words, the inductance of the image-trap circuit is changed to a large value when a VHF-low-band signal is received, and it is changed to a small value when a VHFhigh-band signal is received.
In addition, the capacitance of the combined variable capacitor VD is changed by changing a reverse 7487GB 8 voltage applied-to a tuning-voltage supply terminal 25, together with the capacitances of the variable capacitance diodes 15 and 28. The capacitance of the combined variable capacitor VD is changed to a small value when a high channel signal is received, and it is changed to a large value when a low channel signal is received.
Consequently, when a VHF band signal is received, the inductance of the combined inductor L can be changed to two conditions in conjunction with a switch of the bands. Also, the capacitance of the combined variable capacitor VD can be changed in conjunction with selection of the channels in the same band, thus, the image-trap frequency can be changed in accordance with a change of the reception channels.
Therefore, the image-trap frequency can simultaneously be changed in the range between the minimum frequency and the maximum frequency in accordance with the resonant frequency. Thus, the variable range of the image-trap frequency can be extended, and the image-trap frequency can readily be tuned to the target image frequency.
7487GB 9
Claims (3)
1. An input circuit for a television tuner in which a series circuit including an image-trap capacitor and a second varactor diode is connected in parallel to a series circuit including a tuning inductor and a first varactor diode, and a common tuning voltage is applied to said first and second varactor diodes so that the capacitances thereof change, whereby the resonant frequency and the image-trap frequency change.
2. An input circuit for a television tuner substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.
3. A television tuner, having an input circuit as claimed in Claim 1 or Claim 2.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP8095487A JPH09284157A (en) | 1996-04-17 | 1996-04-17 | Tuner provided with distribution circuit |
Publications (2)
Publication Number | Publication Date |
---|---|
GB9707390D0 GB9707390D0 (en) | 1997-05-28 |
GB2312345A true GB2312345A (en) | 1997-10-22 |
Family
ID=14138970
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB9707390A Withdrawn GB2312345A (en) | 1996-04-17 | 1997-04-11 | Tuner and image trap circuit for TV with common frequency control |
Country Status (6)
Country | Link |
---|---|
JP (1) | JPH09284157A (en) |
KR (1) | KR100243838B1 (en) |
CN (1) | CN1164795A (en) |
DE (1) | DE19715956C2 (en) |
GB (1) | GB2312345A (en) |
MX (1) | MX9702782A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1467487A2 (en) * | 2003-04-09 | 2004-10-13 | Alps Electric Co., Ltd. | Tuned filter |
WO2006132570A1 (en) * | 2005-06-09 | 2006-12-14 | Telefonaktiebolaget L M Ericsson (Publ) | A tunable circuit arrangement and a method for providing such an arrangement |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3592160B2 (en) | 1999-11-25 | 2004-11-24 | アルプス電気株式会社 | Tuner double tuning circuit |
DE60333729D1 (en) * | 2002-02-01 | 2010-09-23 | Nxp Bv | TELEVISION TELEVISION AND CIRCUIT BOARD USED THEREIN |
JP3675438B2 (en) * | 2002-10-31 | 2005-07-27 | 松下電器産業株式会社 | High frequency receiver |
JP3096170U (en) * | 2003-02-27 | 2003-09-05 | アルプス電気株式会社 | Television tuner input circuit |
DE10330449B3 (en) * | 2003-07-05 | 2005-02-24 | Daimlerchrysler Ag | Camshaft adjuster for internal combustion engine has stator and first thrust washer bounding adjuster towards cam frictionally joined to camshaft by cylindrical surface |
CN101179677B (en) * | 2006-11-08 | 2011-12-14 | 奇景光电股份有限公司 | Television tuner and manufacturing method thereof |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4835608A (en) * | 1988-05-31 | 1989-05-30 | Zenith Electronics Corporation | Image trap filter circuit |
JPH0352323A (en) * | 1989-07-19 | 1991-03-06 | Matsushita Electric Ind Co Ltd | Electronic tuner |
US5054117A (en) * | 1989-08-01 | 1991-10-01 | Zenith Electronics Corporation | Tunable UHF filter for switchable VHF/UHF receiver |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6352510A (en) * | 1986-08-22 | 1988-03-05 | Toshiba Corp | Electronic tuner |
JP3053150B2 (en) * | 1993-02-26 | 2000-06-19 | アルプス電気株式会社 | TV tuner input tuning circuit |
-
1996
- 1996-04-17 JP JP8095487A patent/JPH09284157A/en active Pending
-
1997
- 1997-04-11 GB GB9707390A patent/GB2312345A/en not_active Withdrawn
- 1997-04-16 KR KR1019970013895A patent/KR100243838B1/en not_active IP Right Cessation
- 1997-04-16 MX MX9702782A patent/MX9702782A/en unknown
- 1997-04-16 DE DE19715956A patent/DE19715956C2/en not_active Expired - Fee Related
- 1997-04-17 CN CN97104102A patent/CN1164795A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4835608A (en) * | 1988-05-31 | 1989-05-30 | Zenith Electronics Corporation | Image trap filter circuit |
JPH0352323A (en) * | 1989-07-19 | 1991-03-06 | Matsushita Electric Ind Co Ltd | Electronic tuner |
US5054117A (en) * | 1989-08-01 | 1991-10-01 | Zenith Electronics Corporation | Tunable UHF filter for switchable VHF/UHF receiver |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1467487A2 (en) * | 2003-04-09 | 2004-10-13 | Alps Electric Co., Ltd. | Tuned filter |
EP1467487A3 (en) * | 2003-04-09 | 2005-01-19 | Alps Electric Co., Ltd. | Tuned filter |
WO2006132570A1 (en) * | 2005-06-09 | 2006-12-14 | Telefonaktiebolaget L M Ericsson (Publ) | A tunable circuit arrangement and a method for providing such an arrangement |
US7936235B2 (en) | 2005-06-09 | 2011-05-03 | Telefonaktiebolaget L M Ericsson (Publ) | Method to increase the tuneability of varactors |
Also Published As
Publication number | Publication date |
---|---|
KR970073038A (en) | 1997-11-07 |
DE19715956C2 (en) | 2003-08-14 |
KR100243838B1 (en) | 2000-02-01 |
GB9707390D0 (en) | 1997-05-28 |
MX9702782A (en) | 1998-04-30 |
CN1164795A (en) | 1997-11-12 |
DE19715956A1 (en) | 1997-11-06 |
JPH09284157A (en) | 1997-10-31 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4905306A (en) | Filter switching arrangement for a tuner | |
US4247953A (en) | Tunable high-frequency input circuit | |
US4771332A (en) | Tuning apparatus for the VHF band of a television receiver | |
KR100375397B1 (en) | Television signal receiving tuner | |
US7106149B2 (en) | Switchable tuneable bandpass filter with optimized frequency response | |
US4710974A (en) | Circuit arrangement for a tuner for changing over several frequency ranges | |
GB2312345A (en) | Tuner and image trap circuit for TV with common frequency control | |
CA2279566A1 (en) | Receiver having a tuning circuit with a selectable input | |
KR100424691B1 (en) | Vhf band and uhf band television signal receiving tuner | |
US4573211A (en) | Two-circuit resonant bandpass filter for television tuners | |
MXPA97002782A (en) | Entry circuit for a televis tuner | |
US6760079B2 (en) | TV tuner unit having a resonance network | |
US4628540A (en) | Tuning arrangement having a substantially constant frequency difference between an RF-circuit and an oscillator circuit | |
US6734761B2 (en) | Radio-frequency input stage | |
KR100465489B1 (en) | Television receiver | |
KR0133241B1 (en) | Tuner circuit having a switching diode to change receiving bands | |
JPH0730456A (en) | Television tuner | |
US20090201429A1 (en) | Television tuner | |
US7295251B2 (en) | Television tuner capable of improving image disturbance with receiving UHF band | |
KR930006547Y1 (en) | Variable if filter | |
KR100406353B1 (en) | Switching circuit for input tuning in television tuner | |
JPS6228099Y2 (en) | ||
KR940001485Y1 (en) | High Frequency Tuning Circuit of VHF Band Full Tuning Tuner | |
KR0168954B1 (en) | Tuner filter circuit of satellite broadcasting tuner | |
JPH0132433Y2 (en) |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |