CN1795612A - Channel selector with automatic gain control - Google Patents
Channel selector with automatic gain control Download PDFInfo
- Publication number
- CN1795612A CN1795612A CNA2004800147532A CN200480014753A CN1795612A CN 1795612 A CN1795612 A CN 1795612A CN A2004800147532 A CNA2004800147532 A CN A2004800147532A CN 200480014753 A CN200480014753 A CN 200480014753A CN 1795612 A CN1795612 A CN 1795612A
- Authority
- CN
- China
- Prior art keywords
- agc
- switching
- amplifier
- voltage
- frequency
- 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.)
- Granted
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Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3052—Automatic control in amplifiers having semiconductor devices in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver
- H03G3/3068—Circuits generating control signals for both R.F. and I.F. stages
-
- 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
- H04N5/52—Automatic gain control
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G1/00—Details of arrangements for controlling amplification
- H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
- H03G1/0088—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using discontinuously variable devices, e.g. switch-operated
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- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Control Of Amplification And Gain Control (AREA)
- Circuits Of Receivers In General (AREA)
Abstract
In a channel selector with and RF preamplifier and a mixer for converting the RF input signals to intermediate frequency output signals, an automatic gain control (AGC) voltage is derived from the IF output signals for reducing the gain of the RF preamplifier after a predetermined ''take over point'' (delayed AGC). In the IF output path of the mixer a switched attenuator is provided that is switched ''on'' and ''off'' under the control of the automatic gain voltage. The attenuator is ''on'' at levels above the ''take over point''.
Description
Technical field
The present invention relates to a kind of channel selector, said channel selector comprises cascade: the lawnmower amplifier of gain controlling that is used to amplify the radio-frequency channel signal of reception, the radio-frequency channel signal that is used to change amplification is the mixer stage of intermediate-frequency channel signal, the output that is connected to mixer stage is used to select the intermediate-frequency filter from the expectation channel signal of said intermediate-frequency channel signal, be used for from the device of selected intermediate-frequency channel signal derivation AGC voltage with the output that is connected to intermediate-frequency filter, the gain of said AGC voltage when the level of the intermediate-frequency channel signal of said selection is used to reduce the lawnmower amplifier in high level mode during greater than predetermined threshold, and the gain when the level of the intermediate-frequency channel signal of said selection is used to keep the lawnmower amplifier in low level mode during less than predetermined threshold is constant basically.
Background technology
Such channel selector is well-known in the art, and be used for deriving a desired intermediate frequency channel signal from the radio-frequency channel signal of a plurality of receptions, said desired intermediate frequency channel signal has best possible signal noise (S/N) ratio, and does not have tangible nonlinear distortion.For example, can design, its mode by the best operated for the TV tuner of today, the input signal of the input of antenna be 60dB μ V (=1mV), gain is 45 decibels, thereby make intermediate frequency be output as 105dB μ V.The signal noise ratio of antenna input signal is 51.3 decibels, and the noise factor of tuner itself is 4 decibels, so the signal noise ratio of intermediate frequency is 47.3 decibels.
Automatic gain control (AGC) is the delay automatic gain control of so-called low level mode, incoming signal level wherein and to also have intermediate frequency output level subsequently be so low so that the lawnmower Amplifier Gain to reduce be inappropriate.When the intermediate frequency output level has surpassed " acceptance point (take over point) " (TOP) time, automatic gain control enters high level mode, has wherein reduced the lawnmower Amplifier Gain, thereby can keep the intermediate frequency output level constant basically.
Usually, channel selector is used to receive off-the-air signal, and is used to receive the signal from cable system.Particularly when cable was the input of main signal, input signal obviously was better than 60dB μ V, for example 66dB μ V.For some grades of protecting the back are not had the strong signal of nonlinear distortion and the influence of radiation effect, the automatic gain of lawnmower amplifier will reduce the gain of this one-level when controlling (AGC) in the intermediate frequency output signal level in case greater than for example 105dB μ V (being acceptance point (TOP)).But have a shortcoming, that is, the gain of each decibel of lawnmower amplifier reduces to make the noise factor of tuner to increase a decibel, and therefore the signal noise ratio of strong input signal still is the signal noise ratio at " acceptance point ".In the example of above-mentioned appointment, when input signal was increased to 66dB μ V, gain dropped to 39 decibels, and the noise factor of tuner is increased to 10 decibels, makes the signal noise ratio of intermediate frequency still remain on 47.3 decibels.
Summary of the invention
Current, on the market of TV tuner, require when stronger antenna input signal, to have bigger signal noise ratio consumingly.Main purpose of the present invention provides the tuner that has bigger signal noise ratio under the situation of stronger antenna input signal, therefore, be characterised in that the switching pads that between the input of the output of frequency mixer and intermediate-frequency filter, are provided with according to tuner of the present invention, said switching pads are controlled by AGC (automatic gain control) voltage, switching pads are operated under said high level mode at least in part, and inoperation under said low level mode at least in part.
Make it in " acceptance point " or operation on " acceptance point " by the switching intermediate frequency attenuator, automatic gain controller is attempted by increasing the gain loss that the lawnmower Amplifier Gain compensates intermediate frequency path.Final result is, the intermediate frequency output signal is in original levels, but has improved signal noise ratio, and this is that attenuator itself does not increase the cause of noise basically because having reduced the noise that preamplifier increases.For example, for the incoming level of 66dB μ V and 6 decibels attenuator, the reaction of automative interest increasing controlling circuit just looks like to be that incoming level is that 60dB μ V is the same.The result is 6 decibels of the noise factor less thaies of preamplifier.Obviously, the degree of the decay of increase is subjected to being used to handling the restriction that makes the capacity of the capacity of its attenuator frequency mixer in front that can not produce the distortion problem and intermediate frequency path than large-signal.
Also be a switching amplifier being connected in parallel with said switching pads according to the feature of channel selector of the present invention, said switching amplifier is controlled by AGC (automatic gain control) voltage, and switching amplifier is operated under the said low level mode of the inactive part of switching pads.Improved the dynamic range of channel selector at above-described switching pads, and switching amplifier has improved the dynamic range of channel selector in low-signal levels at the higher signal level.Switching amplifier can not improve signal noise ratio because be invalid at this scope automatic gain controller, so intermediate-freuqncy signal with carried out identical amplification with its noise that accompanies by switching amplifier.Yet switching amplifier has increased lower intermediate-freuqncy signal level really, and has increased the sensitivity of channel selector thus,, has increased the minimum signal that produces useful image that is.Before reaching low level mode high-end, this amplifier should turn-off, so that stop automatic gain controller to be operated for the noise of extra increase.For example, when the incoming level of " acceptance point " is the gain of 60dB μ V and switching amplifier when being 10 decibels, switching amplifier should turn-off at the incoming level that is equal to or less than 50dB μ V.Be noted that it is known that continuous intermediate frequency automatic gain with the control combination of radio frequency automatic gain is controlled in this area, for example as can be known from U.S. Patent application publication US 2001/0016950A1.This dual automatic gain is controlled at useful in the receiver with digital demodulator, can obtain big and stable intermediate frequency level in one of incoming level very big scope.
Preferably, be also that according to the feature of channel selector of the present invention in switching pads and the switching amplifier each is all by a comparator switching, the more said AGC (automatic gain control) voltage of said comparator and a predetermined direct voltage.
Description of drawings
Referring now to accompanying drawing the present invention is described.As here representing:
Fig. 1 is the calcspar according to channel selector of the present invention;
Fig. 2 is the curve chart of operation of the channel selector of key diagram 1;
Fig. 3 is used for the switching pads of channel selector of Fig. 1 and the details schematic diagram of switching amplifier.
Embodiment
The channel selector of Fig. 1 comprises: first tuned filter 2, and its input can be connected to antenna 1, and its output is connected to the input of lawnmower amplifier 3.The radio-frequency channel signal that is amplified by lawnmower amplifier 3 is added to frequency mixer 5 by second tuned filter 4, and here, radiofrequency signal multiplies each other with oscillator signal from a tuning local oscillator 6.Frequency mixer converts radiofrequency signal to intermediate frequency (IF) signal, and intermediate-freuqncy signal is amplified in intermediate frequency amplifier 7 subsequently, and provides it to surface acoustic wave filter 8, carries out channel filtering here.
Hereto the device of Miao Shuing all is well-known in the art.Tuned filter 1 and 4 does not have any contribution basically for channel filtering, is mainly used in the frequency that suppresses image, otherwise these picture frequencies can fold in frequency mixer 5 and enter the desired intermediate frequency channel.The desired intermediate frequency channel signal that has fully suppressed adjacent channel signal in SAW filter (surface acoustic wave filter) 8 is added to intermediate frequency unit 9, carries out further intermediate frequency here and amplifies and intermediate frequency demodulation.And intermediate frequency unit 9 produces automatic gain control (AGC) voltage V
Agc, be used to control the gain of preamplifier 3.This is the automatic gain control of a delay: in low imput (low level mode), AGC (automatic gain control) voltage does not reduce the gain of preamplifier 3 basically, and in higher incoming level (high level mode), AGC (automatic gain control) voltage will reduce the gain of preamplifier 3, thereby can keep the intermediate frequency output signal of SAW filter constant basically.This point that AGC (automatic gain control) voltage begins to reduce the gain of preamplifier be exactly " acceptance point " (TOP).In this delay automatic gain control, delay device (as single diode) stops AGC (automatic gain control) voltage to be sent to preamplifier in low level mode, allows such transmission in high level mode.Also might constitute a kind of like this preamplifier 3, its gain can not reduce by the AGC (automatic gain control) voltage that produces under low level mode basically.
According to the present invention, the channel selector of Fig. 1 comprises switching pads 10 and the switching amplifier 11 between the input of the output terminals A that is arranged on intermediate frequency amplifier 7 and surface acoustic wave filter 8.By means of comparator C
1Can make attenuator 10 switch on and off comparator C
1Compare AGC (automatic gain control) voltage V
AgcWith predetermined reference voltage V
1By means of comparator C
2Can make amplifier 11 switch on and off comparator C
2Compare AGC (automatic gain control) voltage V
AgcWith predetermined reference voltage V
2When attenuator 10 and amplifier 11 boths disconnected, this combination provided a reference gain, and this reference gain not necessarily will equal 0 decibel.When switching amplifier is connected, for example 10 decibels of its gain increases, when switching pads were connected, its gain reduced for example 6 decibels.Certainly, amplifier and attenuator should not connected simultaneously.
The operation of expression switching pads and switching amplifier in the schematic diagram of Fig. 2, Fig. 2 represents: the output at surface acoustic wave filter 8 is the intermediate frequency level V of unit with dB μ V
0Be to be the antenna incoming level V of unit with dB μ V
iThe situation of function.Dotted line representative among Fig. 2 does not have this function of attenuator 10 and amplifier 11.At low incoming level, amplifier 11 is connected, and the sensitivity of this set has increased for example 10 decibels.When level increased, amplifier was at the incoming level L of for example 50dB μ V
2Disconnect.Then, level is by " acceptance point ", and acceptance point is positioned at for example incoming level T of 63dB μ V.Incoming level L at for example 65dB μ V
1, attenuator 10 is connected, so that from this level, the signal noise ratio of this arrangement begins to increase.
If there is such possibility: under specific condition, comprise element 8,9, C
1, C
2, there is the trend of vibration in 10,11 loop, then lag behind or the comparator C of latch function by providing to have
1, C
2Just may avoid occurring this situation very simply.
A detailed embodiment of the switching pads 10 of Fig. 3 presentation graphs 1 and switching amplifier 11.Switching amplifier comprises: bipolarity NPN transistor T
1, bipolarity NPN transistor T
1Emitter impedance be resistor R
1, resistor R
2With by-pass capacitor C
1Inductance L in collector terminal
1And and transistorized collector electrode and base stage between capacitor C
3The feedback resistor R of series connection
3By input A and capacitor C
2To transistor T
1Base stage apply intermediate frequency input signal from the intermediate frequency amplifier 7 of Fig. 1, and, by capacitor C
4And through output B to the input of the surface acoustic wave filter 8 of Fig. 1 apply from collector electrode through amplifying signal.By means of switching transistor T
2Make transistor T
1Conducting and end switching transistor T
2Be by comparator C
2Control.The collector electrode of this switching transistor is by collector resistor R
4Be connected to supply voltage, and by resistors in series R
5Be connected to amplifier transistor T
1Base stage.
Switching pads comprise between middle frequency input terminal A and medium frequency output end B: the capacitor C that series connection is arranged
5, resistor R
6, diode D
1, the second diode D
2, resistor R
7, capacitor C
6Resistor R
8With interconnective diode D
1And D
2Anode be connected to positive voltage.Switching transistor T
3Collector electrode pass through resistor R
9Be connected to C
5And R
6Interlinkage, and pass through resistor R
10Be connected to C
6And R
7Interlinkage.Comparator C
1The control switch transistor T
3The numerical value of the passive component of the device of Fig. 3 is as shown in the table:
| R 1 | R 2 | R 3 | R 4，R 9，R 10 | R 5 | R 6，R 7 | R 8 | C 1 | C 2-C 6 | L 1 |
| 10Ω | 82Ω | 220 Ω | 3.3kΩ | 10k Ω | 47Ω | 100 Ω | 330pF | 4.7 |
10 μH |
Be noted that capacitor C
2-C
6Only has the stopping direct current function, resistor R
4, R
9, R
10The function of DC power supply only is provided.
In operation, at low radio frequency incoming level, AGC (automatic gain control) voltage V
AgcHigher, consequently, two comparator C
1And C
2All transmit low output voltage, so switching transistor T
2And T
3All end.Diode D
1And D
2Not conducting, thereby switching pads disconnect.Amplifier transistor T
1Just, pass through transistor T from the intermediate-freuqncy signal of input A in conducting
1Amplify, arrive output B.
As the level L of incoming level by Fig. 2
2The time, voltage V
AgcBy predetermined voltage V
2, make comparator C
2Output become high level, switching transistor T
2Become conducting, transistor T
1End., but make without the intermediate-freuqncy signal of amplifying without any more amplification from the intermediate-freuqncy signal of input by capacitor C
2, feedback path C
3, R
3, and capacitor C
4Arrive output B.Whereby, resistor R
3Numerical value determined reference gain, the gain when promptly the two all disconnects when amplifier and attenuator between terminal A and B.
At last, as the level L of input signal by Fig. 2
1The time, voltage V
AgcBy predetermined voltage V
1, and the output of comparator becomes high level, consequently, and switching transistor T
3With attenuator diodes D
1, D
2All become conducting.Now, from the part intermediate-freuqncy signal current flows through resistor R of input A
8Thereby, make the signal attenuation that is sent to output O.Attenuator is in on-state.Formation is by 3 resistor R
6, R
7, R
8The attenuator that forms is configured to its output impedance as much as possible near the output impedance of switching amplifier in on-state.
Claims (3)
1. channel selector, said channel selector comprise cascade: be used to amplify the gain controlling lawnmower amplifier (3) of the radio-frequency channel signal of reception, the radio-frequency channel signal that is used to change amplification and be the mixer stage (5) of intermediate-frequency channel signal, the output that is connected to mixer stage and be used to select be used for deriving AGC voltage (V from selected intermediate-frequency channel signal from the intermediate-frequency filter (8) of the expectation channel signal of said intermediate-frequency channel signal and the output that is connected to intermediate-frequency filter
Agc) device, said AGC voltage (V
Agc) gain when the level of the intermediate-frequency channel signal of said selection is used to reduce the lawnmower amplifier in high level mode during greater than predetermined level (T), and the gain when the level of the intermediate-frequency channel signal of said selection is used to keep the lawnmower amplifier in low level mode during less than predetermined level (T) is constant basically, it is characterized in that: the switching pads (10) that between the input (B) of the output (A) of frequency mixer and intermediate-frequency filter, are provided with, said switching pads are controlled by AGC (automatic gain control) voltage, make switching pads in operation and inoperation under the said low level mode of at least a portion under the said high level mode of at least a portion.
2. channel selector according to claim 1 is characterized in that: with the switching amplifier (11) that said switching pads (10) are connected in parallel, said switching amplifier is by AGC (automatic gain control) voltage (V
Agc) control, switching amplifier is operated under the said low level mode of the inactive part of switching pads.
3. channel selector according to claim 2 is characterized in that: each in switching pads (10) and the switching amplifier (11) is all by a comparator (C1, C2) switching, the more said AGC (automatic gain control) voltage (V of said comparator
Agc) and a predetermined direct voltage (V
1, V
2).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IB0303970 | 2003-05-27 | ||
| IBPCT/IB03/03970 | 2003-05-27 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1795612A true CN1795612A (en) | 2006-06-28 |
| CN100546184C CN100546184C (en) | 2009-09-30 |
Family
ID=33485268
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2004800147532A Expired - Fee Related CN100546184C (en) | 2003-05-27 | 2004-05-24 | channel selector with automatic gain controller |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP1632027A1 (en) |
| JP (1) | JP2007500989A (en) |
| KR (1) | KR20060013554A (en) |
| CN (1) | CN100546184C (en) |
| WO (1) | WO2004107574A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4676365B2 (en) * | 2006-03-20 | 2011-04-27 | 新日本無線株式会社 | Gain switching amplifier |
| KR102211171B1 (en) * | 2020-04-17 | 2021-02-01 | 삼성에스디아이 주식회사 | Rechargeable battery and case manufacturing method of the same |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4172239A (en) * | 1978-10-06 | 1979-10-23 | Rca Corporation | Signal attenuator |
| JP3371506B2 (en) * | 1994-02-14 | 2003-01-27 | 株式会社日立製作所 | Receiver |
| US5940143A (en) * | 1995-10-06 | 1999-08-17 | Hitachi, Ltd. | High-definition television signal receiving apparatus and gain control circuit thereof |
| JP2996170B2 (en) * | 1996-03-21 | 1999-12-27 | 日本電気株式会社 | Gain control circuit |
| JP3627783B2 (en) * | 1996-12-26 | 2005-03-09 | シャープ株式会社 | Tuner for cable modem |
| CN1190964C (en) * | 2000-02-14 | 2005-02-23 | 夏普公司 | Tuner of cable modem |
| WO2004098052A1 (en) * | 2003-04-29 | 2004-11-11 | Koninklijke Philips Electronics N. V. | Receiver circuit with adjustable if amplifier gain |
-
2004
- 2004-05-24 JP JP2006530891A patent/JP2007500989A/en not_active Withdrawn
- 2004-05-24 WO PCT/IB2004/050758 patent/WO2004107574A1/en not_active Application Discontinuation
- 2004-05-24 KR KR1020057022395A patent/KR20060013554A/en not_active Application Discontinuation
- 2004-05-24 EP EP04734584A patent/EP1632027A1/en not_active Withdrawn
- 2004-05-24 CN CNB2004800147532A patent/CN100546184C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| WO2004107574A1 (en) | 2004-12-09 |
| EP1632027A1 (en) | 2006-03-08 |
| CN100546184C (en) | 2009-09-30 |
| KR20060013554A (en) | 2006-02-10 |
| JP2007500989A (en) | 2007-01-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| ASS | Succession or assignment of patent right |
Owner name: NXP CO., LTD. Free format text: FORMER OWNER: KONINKLIJKE PHILIPS ELECTRONICS N.V. Effective date: 20071012 |
|
| C41 | Transfer of patent application or patent right or utility model | ||
| TA01 | Transfer of patent application right |
Effective date of registration: 20071012 Address after: Holland Ian Deho Finn Applicant after: Koninkl Philips Electronics NV Address before: Holland Ian Deho Finn Applicant before: Koninklijke Philips Electronics N.V. |
|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20090930 Termination date: 20100524 |