KR100994939B1 - Automatically setting an operative state of a wideband amplifier - Google Patents

Abstract

The multi-channel receiver 200 includes an input 111 for receiving a wideband signal potentially including multiple channels, a tuner stage 110, a wideband amplifier 201 connected between the input 111 and the tuner 110, Control switch 202 bridging amplifier 201 and switch controller 203 designed to generate a switch control signal BSC. To control the switch, the switch controller 203 is designed to measure at least one signal quality parameter and generate a switch control signal BSC based on the measured parameter. The determination of the switching of the switch 202 to the open state (amplifier active) is only performed during at least one time interval when the receiver is switched to the channel.

Multichannel Receiver, Wideband Signal, Tuner Stage, Switch Controller, Noise Content

Description

Automatically setting an operative state of a wideband amplifier

The present invention relates to a method for automatically setting an operating state of a broadband amplifier of a multi-channel receiver, the method comprising measuring at least one signal quality parameter and turning the amplifier on based on the measured parameter (active state) Or determining to switch to an OFF state (inactive state). The invention also relates to a signal quality measurement system for use in a receiver capable of receiving at least one input signal. The present invention also provides

An input for receiving a wideband signal potentially containing multiple channels,

-Tuner stage,

A broadband amplifier connected between said input and said tuner,

A controllable switch bridging the amplifier, and

A multi-channel receiver comprising a switch controller designed to generate a switch control signal.

As is known, television signals are transmitted on transmission channels, each channel being specified by at least one carrier frequency and channel bandwidth. Typically, multiple television programs are broadcast simultaneously on different transport channels. The television receiver comprises at least one tuner for tuning the receiver to one selected channel and thus receiving the television signal of the selected television program for further processing. In a television set, such additional processing may include the playback of video and audio, and in the recorder this additional processing may include recording of the television signal for future playback.

In practice, the reception conditions of the television signals may vary. For example, due to changes in ambient conditions, the signal quality may change over time. In addition, at a particular reception location, among the set of available television channels, some signals may be quite strong with relatively little noise, and other signals may be at particular distances from respective transmitters and respective powers of these transmitters. Thus, when transmitted over the air waves, it may be relatively weak with relatively large noise, in which case the signal quality may change when switching from one program to another. In addition, the receiver may be connected to a cable network having a relatively constant signal quality, but the signal may be strong or relatively weak, especially depending on the quality of this cable network and the distance from the nearest amplifier. In the case of cable networks, it is also possible that the received RF signal is strong but the video content may be noisy, depending on the video source used by the cable TV operators.

The television receiver should be able to handle both of these reception conditions and function properly. For this purpose, it is known to equip a tuner with a low-noise broadband amplifier (hereinafter also referred to as LNA). For relatively weak RF signals, the LNA is switched ON to increase the signal-to-noise ratio (S / N) of the demodulated video. However, this LNA is a wideband amplifier that operates on all television channels in the band without input selection, so that unwanted in-band intermodulation products from adjacent channels will be generated, especially when strong signals are received. Can be. To prevent this, such an LNA is implemented as a switchable amplifier that is switched OFF when strong signals are received.

It is possible to provide manual switching, but automatic switching is preferred in view of convenience for the user. In this case, the receiver also has an LNA control system for automatically switching the LNA ON or OFF depending on the signal quality. This LNA control system includes an LNA controller and a signal quality measurement system, which provide a signal quality indication signal for the LNA controller.

The main object of the present invention is to improve such a control system. The invention is defined by the independent claims. The dependent claims define advantageous embodiments.

The object is realized by the step of determining the switching of the amplifier to the ON state (active state) only during at least one time interval when the receiver is switched to the channel. The time interval when the receiver is switched to the channel is, for example, the time interval when the receiver is switched on, the time interval when a new channel is selected or the time interval during the installation process, whereby all channels are scanned.

Based on the measured parameters, the operating state of the broadband amplifier is set to the ON state or the OFF state. As long as the receiver remains switched to the channel, the OFF state is always maintained, while during the ON state the broadband amplifier can be switched to the OFF state if the signal quality deteriorates. Once switched OFF, the wideband amplifier remains in this state until channel switching occurs. Thus, cumbersome ON and OFF switching of the broadband amplifier that may occur in existing receivers is avoided.

In existing installations, the signal quality measurement system basically only measures the signal strength of the signal (channel) to which the receiver is actually tuned. The determination of whether to switch LNA ON or OFF is then only based on the signal strength of the desired signal itself. In one embodiment of the invention, the signal quality measurement system is designed to measure actual disturbance signal contributions from unwanted channels.

In existing installations, a signal quality measurement system provides a quality signal, and the controller makes a decision by comparing the quality signal with predetermined decision criteria. In one embodiment of the invention, the controller is designed to measure whether the LNA actually provides an improvement. More specifically, the actual disturbance signal contributions are measured once with LNA switching ON and twice with LNA switching OFF. If the measurement at the LNA switching ON shows an improvement (or at least no degradation) compared to the measurement at the LNA switching OFF, it is determined to keep the LNA switching ON state. Conversely, if the signal quality at LNA ON is good but the signal quality at LNA OFF is better, it is determined to keep the LNA switching OFF.

In another embodiment of the invention, the signal quality measurement system is designed to measure the signal states of all channels available for reception. This measurement is preferably performed as part of the installation procedure of the receiver when the channel data is stored in the memory (auto tuning), since the entire frequency range of interest is skimmed during this installation procedure. Although only one channel is affected by poor signal quality, for example due to intermodulation products, the LNA controller switches the LNA to OFF, otherwise the LNA controller switches the LNA to ON. For the remainder of the operating life of the receiver device or until a new installation procedure is executed, the LNA is maintained in the switched off or switched on state, respectively.

These and other features and advantages of the present invention will be further described by the following description of the present invention with reference to the drawings, wherein like reference numerals designate the same or similar parts.

1 is a block diagram schematically showing a conventional television receiver.

2A is a graph showing AGC operation of the tuner.

2B is a graph illustrating AGC operation of a processor.

3 is a block diagram compared to FIG. 1 schematically illustrating a television receiver according to the invention;

4A and 4B are diagrams schematically showing details of possible embodiments of a television receiver according to the invention.

1 schematically illustrates general signal processing in a conventional television receiver 100 for receiving television signals and providing predetermined video and audio signals corresponding to a selected television channel. In general, television receiver 100 includes a tuner stage 110, a filter stage 130, an amplifier stage 150, and a processor 170.

The tuner stage 110 receives the antenna signal SA from the antenna 111. In principle, the antenna signal SA may include all frequencies in the (television) electromagnetic spectrum (typically in the range of about 48 MHz to about 865 MHz). Based on the command input signal 112 as provided by the user, the tuner stage 110 includes a video and audio signal of one selected television channel, which is shifted to a predetermined frequency range. Create The tuner output signal ST is filtered by a filter stage 130 which substantially removes all unwanted frequencies outside of the predetermined frequency range, so as to include only the audio signals of the selected channel and the frequencies of the picture. Generate a tuner output signal (STF). After suitable amplification by the amplifier stage 150, the filtered tuner output signal STF provides in particular the video signal VI at the first output 171 and the audio signal AU at the second output 172. Is demodulated in the processor 170. The processor 170 also provides a first automatic gain control signal AGC1 for the amplifier stage 150 at the third output 173.

The tuner 110 includes an RF amplifier 115 for amplifying the antenna signal SA received from the antenna 111. The gain of the RF amplifier 115 is controlled by a second automatic gain control signal AGC2 provided by the processor 170 at the fourth output 174.

In conventional television receivers, the tuner stage 110, filter stage 130, amplifier stage 150, and processor 170 are known components, and therefore, a more detailed description of their design and operation is omitted herein. It is noted. Only the conventional function of the automatic gain signal generator of the processor 170 will be described in more detail with reference to FIG.

FIG. 2A is a graph showing typical operation of the tuner stage 110, and more specifically, the graph shows a second automatic gain control signal ACC2 (horizontal axis) and a gain G (vertical axis) of the tuner stage 110. FIG. Shows a typical relationship between them. The second automatic gain control signal AGC2 is a DC voltage level that can be set in the range of a minimum value (typically 0.5V) to a maximum value (typically 5V). At values above the predetermined first gain control level (typically 4V), the gain G of the tuner stage 110 is at a maximum value which is typically about 45 dB. At values below this predetermined first gain control level, the gain G of the tuner stage 110 is reduced in accordance with the decrease value of the gain control signal AGC2, typically 5 dB at a gain control signal value of 0.5V. Value is reached.

2B is a graph illustrating typical operation of the processor 170. More specifically, this graph shows a typical relationship between the signal strength (horizontal axis) of the antenna signal SA and the gain G (vertical axis) of the tuner stage 110 as set by the processor 170. As long as the antenna signal SA is typically below a predetermined level of 60 dB / kHz, the gain of the tuner stage 110 remains constant at a maximum, which is typically about 45 dB. To this end, the processor 170 generates a second automatic gain control signal AGC2 for the wideband RF amplifier 115 at the maximum level of 5V, such that the gain G of the RF amplifier 115 is at its maximum. . The signal level of the tuner output signal ST is then below the maximum level of about 105 dB / kHz. In this case, the processor 170 generates a first automatic gain control signal AGC1 for the amplifier stage 150 to maintain the signal levels of the corresponding video signal VI and the audio signal AU at a constant level.

If the antenna signal SA typically exceeds a predetermined level of 60 dB / kHz, this means that the signal level of the tuner output signal ST exceeds this maximum level of about 105 dB / kHz [more specifically, the signal input 176 Is sensed by the processor 170 because the signal level of the signal received by the processor 170 exceeds the predetermined maximum input signal level. In this case, processor 170 typically provides a second automatic gain control for wideband RF amplifier 115 to maintain a substantially constant signal level of the tuner output signal ST at the predetermined maximum level of about 105 dB / kHz. Generate signal ACC2, while processor 170 generates a first automatic gain control signal ACC1 for amplifier stage 150 to maintain the gain of amplifier stage 150 at a substantially constant value.

FIG. 3 schematically shows a television receiver 200 with an additional broadband amplifier, commonly referred to as LNA (low noise amplifier), hereinafter, typically in the range of 45 to 865 MHz, for preamplifying the wideband antenna signal SA. It is a block diagram similar to FIG. This LNA 201 may be an integral part of the tuner 110, but for the sake of clarity the LNA 201 is shown as a separate component having an output connected to the tuner input.

The noise performance parameter "Noise Figure" (NF) of a circuit block can be defined as follows:

NF = CN _IN / CN _OUT

Where CN _IN is the carrier-to-noise ratio at the input of the block and CN _OUT is the carrier-to-noise ratio at the output of the block.

The LNA 201 as described above improves the signal-to-noise ratio (S / N) of the television receiver 200. Standard tuners 110 typically have a noise figure (NF) in the range between 6 dB and 11 dB. LNA 201 may have a gain of about 12 dB and typically have a noise figure (NF) of less than about 2.5 dB, in which case the combination of LNA 201 and tuner 110 is typically of 3-4 dB. Will have a noise figure. Thus, noise related performance of television receivers is improved by including LNA 201.

The problem with LNAs is that LNAs tend to introduce intermodulation products at frequencies within the passband of the selected channel. These intermodulated signals are due to cross modulation between the desired signal (the channel on which the tuner 110 is tuned) and the unwanted signals from adjacent channels, and also due to the horn modulation between the unwanted channels. Is generated. If this occurs, it is very difficult or even impossible to eliminate such intermodulated signals in subsequent signal processing, since these intermodulated signals are located within the pass band of the selected channel. Finally, the generated video signal output will therefore be degraded by these interfering intermodulation signals.

As a result, if the signal at the input of tuner 110 exceeds predetermined decision levels, it may be necessary to switch off LNA 201 or bypass LNA 201. Typically, LNA 201 is switched OFF when the RMS value of the signal at the input of tuner 110 exceeds a level of about 60 dB / kHz. 3 shows a bypass switch 202 coupled in parallel to the LNA 201 controlled by a bypass switch control signal BSC from the bypass switch controller 203. The controller 203 may be part of the processor 170, but is shown as a separate unit for clarity.

One embodiment of the invention is directed to a method of measuring whether the RMS value of a signal at the input of tuner 110 exceeds said level of about 60 dB / kHz. To this end, the present invention takes advantage of the fact that the processor 170 performs a control action in advance based on the question of whether the RMS value of the signal at the input of the tuner 110 exceeds a level of about 60 dB / kHz. Take it. Thus, instead of monitoring the antenna signal SA or the RMS value of the signal at the input of the tuner 110, the controller 203 monitors the determination of the processor 170 in this respect.

4A illustrates one embodiment of a controller 203 in accordance with the present invention. In one embodiment, the controller 203 has one input 204a coupled to receive a second automatic control signal AGC2 from the processor 170, and a suitably selected reference voltage V of, for example, 4.5V. _ref ) with a comparator 204 having another input 204b coupled to receive. As long as the antenna signal SA is below this level of 60 dB / kHz, the second automatic control signal AGC2 has a value of about 5 V, which is clearly higher than the reference voltage V _ref , so that the output of the comparator 204 is Logically HIGH. If the signal at the input of the tuner 110 exceeds a level of 60 dB / kHz, the processor 170 starts AGC operation, in which case the second automatic control signal AGC is clearly lower than the reference voltage V _ref . Since it has a value of less than 4V, the output of comparator 204 is logically LOW. The output signal of the comparator 204 can be used to switch the bypass switch 202 directly or after some additional processing. Note that other methods for detecting the voltage drop from 5V to 4V are also possible.

4B illustrates another embodiment for monitoring the AGC control action of the processor 170 in accordance with the present invention. In this case, a bias circuit 210 is provided that includes a parallel combination of two resistors 212 and 213 connected in series and a voltage source 211. The node 214 between the two resistors 212, 213 can be considered as the output of the bias circuit 210 connected to the fourth output 174 of the processor 170.

As long as the signal at the input of the tuner 110 is below a level of 60 dB / kV, the current I 1 flowed by the processor 170 at the fourth output 174 from the node 214 is substantially zero. The current I2 flowing from the node 214 by the tuner stage 110 can be ignored. The bias circuit 210 is designed such that the voltage at node 214 is about 5V when the current flowing from node 214 is zero.

As soon as the signal at the input of tuner 110 exceeds a level of 60 dB / kHz, the signal level of the signal received by processor 170 at signal input 176 exceeds a predetermined maximum input signal level, and the processor 170 begins AGC operation, in which case current I1 flowed from node 214 by processor 170 at fourth output 174 rises. In the example of the embodiment, this current I1 is on the one hand the signal level of the signal received by the processor 170 at the signal input 176 and on the other hand the predetermined maximum input signal, for example 500 mA / dB. It can be proportional to the difference between levels. Because of this current I1, the voltage at node 214 can drop. The bias current 210 is designed in such a way that the voltage drop at the node 214 is proportional to the current I1, for example 4V / mA. As described above, as soon as the processor 170 starts AGC operation, the second automatic control signal AGC2 has a value of less than 4V, that is, a voltage drop of at least 1V corresponds to a current I1 of at least 250 mA. Occurs. The processor 170 can sense this current I1 and is designed to generate a control signal for switching the bypass switch 202 directly or after some additional processing.

In the prior art, the quality of the signal at the input of the tuner 110 is continuously monitored so that the LNA 201 can be repeatedly switched ON and OFF even when the user is still watching one television program. This results in noticeable display effects and thus annoys the user.

To avoid this, in a preferred embodiment of the present invention, the LNA can be switched ON only at the moment when the user switches to a new channel or activates the television receiver. In the LNA 201 in the ON state, the quality of the signal at the input of the tuner 110 is continuously monitored and switching the LNA 201 to OFF at any moment (i.e. closing the bypass switch 202). A decision is made. In the LNA 201 in the OFF state, the bypass switch 202 remains closed for the remainder of the selected television program until the user switches to a new channel.

In the LNA 201 in the ON state, the decision to switch the LNA 201 to OFF is based on the signal level at the output of the LNA 201. When the LNA 201 has a gain of about 12 dB, the decision level of 60 dB / kHz of the signal at the input of the tuner 110 corresponds to the level of 48 dB / kHz of the antenna signal SA.

In the prior art, the determination of whether to activate the LNA was based entirely on the quality of the signal in the selected channel. In turn, the processor 170 generates a second gain control signal ACC2 for the tuner stage 110 based on the signal received from the amplifier stage 150, which essentially includes only the signals in the pass band. However, although the main reason for bypassing the LNA is to reduce undesirable effects from the intermodulated signal, the processor 170 may determine for the tuner 110 based on the actual presence or absence of such an intermodulated signal. The second gain control signal AGC2 is not generated. Thus, if the determination of switching to LNA ON or OFF is based solely on the AGC control mode, the actual presence or absence of such intermodulated signal is not considered at all.

To overcome this drawback, the present invention provides a measurement signal indicative of the actual presence or absence of the intermodulation signal, and at least partially determines the determination of switching to LNA ON or OFF. It is proposed to base the signal on which it is indicated as S _IP below.

The intermodulated signal can be considered noise, and thus one particular implementation of the measurement signal S _IP indicative of the intermodulated signal can be obtained by measuring the signal to noise ratio S / N. S / N may be defined as the ratio of the peak-to-peak value VSpp of the video signal to the RMS value NS _RMS of the noise signal, ie S / N = VSpp / NS _RMS . Due to the automatic gain control action of the processor 170, the video signal VI at the first output 171 has a substantially constant peak-to-peak value for large deviations in the signal level of the RF antenna signal SA. In general, the video output level remains substantially constant when the signal level of the RF antenna signal SA changes from 20 dB / kHz to 100 dB / kHz. Therefore, it is desirable to obtain a signal that is substantially only indicating the RMS value NS _RMS of the noise signal. In any case, since the peak-to-peak value of the video signal can be a substantially constant signal, it is not necessary to have a signal indicative of the peak-to-peak value VSpp of the video signal.

Basically, once the noise is in the signal, it is very difficult or even impossible to separate the noise from the video signal. However, in a preferred embodiment, the advantageous use is the use of the fact that some lines of the CVBS video signal, such as lines 17 and 18, are blank during vertical flyback, which is constant during the horizontal scanning period of these lines. It must be at the DC level. In other formats, other line numbers may be blank.

Noise generated from electronic circuits such as amplifiers is typically distributed in a uniform manner across the video signal. Thus, any AC signal during the horizontal scanning period of these blank lines is directly related to the RMS value of the noise signal in the CVBS video signal, and the measurement of this AC signal substantially indicates the RMS value (NS _RMS ) of the noise signal. Provide a signal.

In general, since the CVBS signals of the different channels are not synchronized, the lines 17 and 18 of the blank period do not generally coincide with the lines of the blank period in neighboring CVBS signals, ie in the disturbing channels. Thus, if the intermodulation signal is generated by undesirable channels, it is expected that such a disturbing intermodulation signal will be present at lines 17 and 18 of the blank period of the selected signal for at least some time at regular intervals. do.

In a practical embodiment, when measuring the noise signal NS _RMS , the measured noise is a combination of widely distributed noise and noise generated by the intermodulation signal. If the LNA is OFF, any such intermodulatory signal may be ignored or it may be assumed that no intermodulatory signal is present.

As described above, the present invention proposes to make a decision to switch to LNA ON or OFF based on the measurement signal S _IP indicative of the intermodulation signal. In one practical embodiment, it is also possible that this determination is based on an absolute measurement performed by comparing the noise level of the signal with a predetermined decision level. This predetermined decision level may correspond to a signal / noise ratio of 43 dB, which is an acceptable noise ratio for consumers. If the signal / noise ratio is better than 43 dB, the signal condition can be determined to be good and no LNA is needed.

Thus, when selecting a channel or switching the receiver ON, the LNA 201 is initially switched OFF. If the measurement signal S _IP exhibits a better signal / noise ratio than 43 dB, the bypass switch controller 203 determines to keep the LNA 201 switched OFF.

In further details of the invention, the impact of LNA 201 is clearly contemplated. To consider the effect of the LNA 201, the signal-to-noise ratio is measured at least twice: once at the LNA 201 switching on, once at the LNA 201 switching off, and the two measurement results are compared with each other. .

This procedure can always be executed to eliminate the need to predefine a predetermined decision level. After the measurement result obtained at the LNA 201 switching off, as indicated by S _IP (LNA = OFF), is determined to indicate a signal / noise ratio worse than 43 dB, this comparison procedure may also be performed only as a second step procedure. It is possible.

If the measurement result [S _IP (LNA = OFF)] indicates a signal / noise ratio worse than 43 dB due to noise only, it may be desirable to switch the LNA to ON. In this case, the measurement result S _IP (LNA = OFF) is stored in the memory to function as a reference value.

The LNA 201 is then switched to ON and measured with the LNA 201 with a signal-to-noise ratio switched to ON, yielding a measurement result indicated by S _IP (LNA = ON). This result is compared to the previously measured result [S _IP (LNA = OFF)] stored in memory and determined to switch the LNA to the state that provides the best quality. Next, higher S _IP values will be assumed to represent more intermodulation signals. Thus, if S _IP (LNA = ON) <S _IP (LNA = OFF), it is determined to keep LNA switching ON, whereas if S _IP (LNA = ON)> S _IP (LNA = OFF), It is determined to keep the LNA switching OFF.

Preferably, when S _IP (LNA = ON) = S _IP (LNA = OFF), it is determined to keep the LNA switching ON.

Preferably, the S _IP (LNA = OFF) is measured first and then the S _IP (LNA = ON) as described above, but the measurement can be performed in the reverse order.

As mentioned above, the decision to keep the LNA in the ON or OFF state is basically made only at the moment when the television receiver is switched ON or when the user switches to another channel. However, under certain circumstances, the measurement may not reliably reflect the amount of disturbance caused by the intermodulation signal.

For example, at any time, the disturbance generated by the intermodulation signal is expected to be proportional to the signal strength of the disturbing signal of the adjacent channel at that time. However, this signal strength is not constant. In the case of a negative modulation format, the carrier's modulation depth is maximum during the white portion of the picture frame and minimum during the synchronization period. Thus, the measurement signal S _IP representing the intermodulated signal measured at a particular time depends on the image frame contents of the adjacent channel at that time, that is, the white part, the black part, and the synchronization period, which depends on the difference of 15 dB. This may be the case. Thus, when the user switches to another channel and the measurement signal S _IP representing the intermodulation signal is measured, the disturbing signal of the adjacent channel corresponds only to the white portion, that is, the signal strength at that time is low and intermodulation Almost no noise from the enemy signal is detected and allows the bypass switch controller 203 to decide to keep the LNA switched on, while other parts of the disturbing signal of the neighboring channel, such as blacks or synchronization pulses, Generates an annoying intermodulation signal, and if such a situation is detected, allows bypass switch controller 203 to determine to keep the LNA switched off.

Indeed, the vertical periods of CVBS signals in different channels do not have exactly the same length. As a result, after sufficient time passes, the measurement periods (lines 17 and 18) of the selected signal will move relative to the adjacent channels and correspond to other signal portions of the adjacent channels.

In further details of the invention, the effect is used as follows. Initially, i.e. at the start of a television receiver or switching to another channel, the LNA is switched OFF and the value S _IP (LNA = OFF) of the measurement signal S _IP representing the intermodulation signal is measured. . The measurement result is saved. Thereafter, the LNA is switched ON, and the value S _IP (LNA = ON) of the measurement signal S _IP representing the intermodulated signal is measured. This value is compared with the stored measurement result S _IP (LNA = OFF), and a decision is made to switch the LNA ON or OFF based on the result of this comparison.

When it is determined to switch the LNA to ON, the value S _IP (LNA = ON) of the measurement signal S _IP indicating the intermodulation signal is measured regularly (for example, once per predetermined period of time, such as once per second). 1 time). After each measurement, the final value S _IP (LNA = ON) is compared with the initially measured value S _IP (LNA = OFF). When the condition _{S IP (LNA = ON) ≤S} IP (LNA = OFF) is applied, it is determined to switch the LNA is turned ON. As soon as the condition S _IP (LNA = ON)> S _IP (LNA = OFF) occurs, decide to switch LNA OFF and keep LNA switching OFF regardless of the change in value [S _IP (LNA = ON)], a process of comparing the value S _IP measure (LNA = ON), and the value S _IP (LNA = OFF) can be stopped (there is no need to switch the LNA ON to regularly and OFF).

In practice, the measurement signal S _IP indicative of the intermodulation signal can only take values within a predetermined range of values. For example, if the value of S _IP stored in the memory register having N bits, S _IP may take only the values between 0 (shown as S _MIN) and 2 ^N-1 (shown as S _MAX). The noise caused by the intermodulation enemy signal is very large, the value of _{[S IP (LNA = OFF)} ] is already extreme of the range (extreme value), in this case S _MAX (or high noise measurements at the beginning of the S _IP If corresponding to low values, it may have S _MIN ). If the noise generated by the intermodulation signal is worse when the LNA is switched on, the noise is not significant because the value of the measured signal representing the intermodulation signal cannot exceed S _MAX (or below S _MIN respectively). It cannot be represented by the measurement signal S _IP representing the intermodulation signal. The bypass switch controller 203 can then be properly determined since the two measured values S _IP (LNA = OFF) and S _IP (LNA = ON) do not accurately reflect the relative strengths of the intermodulation signal. none.

In a further detail of the invention, this problem is avoided as follows. Initially, ie when switching across different channels or at the beginning of a television receiver, the LNA is switched off and the value of the measurement signal S _IP representing the intermodulation signal is measured. In addition, the value S _IP (LNA = ON) of the measurement signal S _IP of the intermodulated signal is measured and compared with the value S _IP (LNA = OFF). As before, if S _IP (LNA = ON) <S _IP (LNA = OFF), it is determined to keep LNA switching on, while if S _IP (LNA = ON)> S _IP (LNA = OFF), LNA switching It is determined to keep off.

If S _IP (LNA = ON) = S _IP (LNA = OFF), a check is made to see if S _IP (LNA = OFF) has an extreme value S _MAX . If S _IP (LNA = OFF) is lower than the extreme value (S _MAX ), it is determined to keep the LNA switching ON as before. If S _IP (LNA = OFF) is equal to the extreme value (S _MAX ), it is determined to switch the LNA to OFF and keep the LNA to OFF as long as the current channel maintains the selected channel. This switching method provides a performance improvement of about 4 to 8 dB, especially in the UHF band. In the UHF band, the noise figure NF for the tuner stage 110 is about 8-12 dB. By using an LNA with a noise figure (NF) of about 3 dB, the overall noise figure will be an improvement of about 4 dB, ie about 4 to 8 dB.

It will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments and that various changes and modifications are possible within the protection scope of the present invention as defined in the claims.

For example, any other signal capable of displaying noisy content can be used to represent the intermodulation signal.

Moreover, the decision making process as described may be implemented in hardware or software, or firmware as desired.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The use of the verb 'comprise' and its conjugation does not exclude the presence of elements or steps other than those listed in a claim. The use of “a, an”, preceding a component or step does not exclude the presence of a plurality of such components or steps. The invention can be implemented by means of hardware comprising respective separate components and by means of a suitably programmed computer. In the device claims enumerating respective means, each of these means may be embodied by one and the same item of hardware. The fact that certain measures are cited in different dependent claims does not indicate that a combination of these measures has no advantage.

Claims (19)

In the method for automatically setting the operating state of the broadband amplifier 201 in a multi-channel receiver, Measuring at least one signal quality parameter; And determining to switch the amplifier 201 to an ON state or an OFF state based on the measured parameter, Determining to switch the amplifier 201 to the ON state may include an installation process during a time interval when the receiver is switching to a new channel, or during the activation of the multichannel receiver, or when all channels are scanned. A method of automatically setting the operating state of a broadband amplifier, taken only during The method of claim 1, If it is determined to switch the amplifier 201 to the ON state based on the measurement result, signal quality monitoring procedures are repeatedly performed, and each procedure is performed as follows. Re-measuring the signal quality parameter; Determining, based on the re-measured parameter, to keep the amplifier 201 ON or to switch the amplifier 201 to the OFF state. The method of claim 1, Measuring the at least one signal quality parameter comprises measuring intermodulation products. The method of claim 1, Measuring the at least one signal quality parameter comprises measuring a noise-related signal. The method of claim 1, Measuring the at least one signal quality parameter comprises determining whether an automatic gain control system of the receiver is active or inactive. The method of claim 5, Determining whether the DC voltage level of the automatic gain control signal AGC2 has a first value indicating that the automatic gain control system is inactive or having a value within a predetermined range indicating that the automatic gain control system is active. Included, the operating state automatic setting method of the broadband amplifier. The method of claim 5, Determining whether the automatic gain control signal output 174 of the gain controller 170 indicates that the automatic gain control system is inactive because no current flows, or that the current amount indicates that the automatic gain control system is active. Included, the operating state automatic setting method of the broadband amplifier. The method of claim 1, Determining to switch the amplifier 201, a) switching the amplifier 201 to an OFF state; b) measuring the value of the at least one signal quality parameter while the amplifier 201 remains in the OFF state; c) comparing the measured value with a predetermined decision level; And d) if the comparison indicates a good signal state, determining to maintain the amplifier 201 operating in the OFF state. The method of claim 1, Determining to switch the amplifier 201, a) switching the amplifier 201 to an OFF state; b) measuring the value of the at least one signal quality parameter while the amplifier 201 remains in the OFF state; e) switching the amplifier 201 to an ON state; f) measuring the value of the at least one signal quality parameter while the amplifier 201 remains ON; g) comparing the two measured values; h1) if the difference between the two measured values indicates more intermodulation signals when the amplifier 201 is in the OFF state compared to when the amplifier 201 is in the ON state, the amplifier Determining to switch 201 to an ON state; h2) if the difference between the two measured values indicates more intermodulation signals when the amplifier 201 is in the ON state compared to when the amplifier 201 is in the OFF state, the amplifier And determining to switch 201 to an OFF state. The method of claim 9, Wherein steps a) and b) are performed before steps e) and f). The method of claim 9, The comparing step, h3) if the two measured values are equal to each other, determining to switch the amplifier 201 to an ON state. The method of claim 9, The comparing step, h3) if the two measured values are equal to each other: h3i) checking if the value of the signal quality parameter has an extreme value (S _MAX ) when the amplifier (201) is switched OFF; h3ii) determining to switch the amplifier 201 to the ON state if the value of the signal quality parameter is not equal to the extreme value when the amplifier is switched OFF; h3 iv) determining to switch the amplifier 201 to the OFF state if the value of the signal quality parameter is equal to the extreme value when the amplifier is switched OFF. The method of claim 1, Measuring the at least one signal quality parameter comprises measuring signal states of all available channels, and wherein the measuring and determining to switch are performed only during an initialization procedure of the receiver. How to automatically set the operating state of the amplifier. The method of claim 13, Wherein the at least one signal quality parameter comprises a signal-to-noise ratio and a signal strength of each of the available channels. delete delete In the multi-channel receiver 200, An input 111 for receiving a wideband signal potentially including multiple channels; A tuner stage 110; A wideband amplifier 201 connected between the input 111 and the tuner 110; Means for measuring at least one signal quality parameter; Means for determining to switch the amplifier 201 to an ON state or an OFF state based on the measured parameter, wherein determining to switch the amplifier 201 to an ON state means that the receiver is switched to a new channel and Means for determining, taken during a time interval when present, or during activation of the multi-channel receiver, or only during an installation process when all channels are scanned. The method of claim 17, And a controllable switch 202 for bridging the amplifier 201, The means for measuring and means for determining may comprise a switch controller for generating a switch control signal BSC and measuring at least one signal quality parameter to generate a switch control signal BSC based on the measured parameter; 203), The switch controller 203 is designed to switch the controllable switch 202 from a closed state, the amplifier is inactive in an open state, and the amplifier is in the time interval when the receiver is switching to the new channel. Or during the activation of the multi-channel receiver or only during the installation process when all channels are scanned. The method of claim 1, And the multichannel receiver is a multichannel television receiver.

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