Apparatus and method for optimizing the level of rf signals based upon the information stored on a memory

ES 2 264 451 T3

DESCRIPTION

Apparatus and method for optimizing the level of RF signals based on the information stored in a memory.

The present invention relates to a radio frequency (RF) signal processing arrangement and method for optimizing the level of radio frequency (RF) signals suitable for RF signal receiving systems such as television signal receivers.

It is desirable for a television signal receiver to receive television signals having appropriate signal strength throughout the television broadcast band so that a user can always enjoy good quality pictures and sound. However, the signal strength of individual television channels that are received in a particular geographical position frequently varies from one to another mainly due to the difference in the geographical distance between each of the broadcasting stations and the receiving position of the user. . When the receiver tunes to a television channel that has undesirable signal characteristics (for example, too weak or strong interference present), such a state could cause various problems including undesirable noise in the pictures due to poor signal-to-noise ratio and cross-modulation caused by interference. from adjacent frequency signals for analog reception. Furthermore, these problems are especially detrimental to the reception of digital broadcast signals since reception is totally lost when the quality of the signals falls below a particular threshold.

A conventional way of solving the weak signal problem is to selectively apply an additional low noise optimized amplifier between an antenna and a tuner in response to the automatic gain control signal, which represents the strength of the received television signals. For example, U.S. Patent 5,638,141, titled Broadcast Signal Receiver Having a Low-Noise Amplifier Inserted Before a Tuner, filed by Bae et al., Assigned to Samsung Electronics Co., Ltd., and granted the June 10, 1997, describes this type of solution. However, the conventional solution is not a preferable solution to the problems discussed above because the automatic gain control signal does not represent the quality of the television signals (that is, the image and / or sound quality) but simply represents the amount (that is, signal strength) of the television signal that is received. Also, the automatic gain control signal does not reflect the strength of the signals at the adjacent channel frequencies, which could cause the interference problem. Therefore, there is a need for an RF signal processing circuit that optimizes the level of the input television signals on each of the television channels in response to the quality of the television signals and / or in response no. only to the intensity of the tuned signal without also to that of the adjacent signals.

EP-A 0 969 601 describes a method for improving the desired signal in a radio receiver unit. The radio receiver unit comprises a channel filter, a switch, a control unit, means for signal strength detection and controllable amplifiers. The switch is actuated to alternately supply a first signal upstream of the channel filter and a second signal downstream of the channel filter to the means for signal intensity detection. The controllable amplifiers are driven in response to an output signal from the signal strength sensing means.

JP 2001077713A describes a digital broadcast receiver for stable reception of a specified channel. Reception is not disturbed by a high signal level on an adjacent channel because an automatic RF gain control is selected in correspondence with the signal level of the selected channel and the adjacent channel.

The invention is defined in the appended claims. According to a first aspect, the invention suggests a signal processing arrangement comprising: a signal source for providing a radio frequency (RF) signal; means for tuning a channel frequency; means for retrieving information relating to radio frequency (RF) signals at said tuned channel frequency and at a channel frequency close to said tuned channel frequency from a memory; and means for enabling an RF amplifier if said information indicates that the magnitude of an RF signal at said tuned channel frequency is less than a first predetermined threshold level and that the magnitude of an RF signal close to said channel frequency. tuned is less than a second predetermined threshold level. Wherein the signal processing arrangement further comprises means for receiving an information-bearing RF signal; means for receiving RF signal magnitudes at respective ones of said tuned channel frequency and said channel frequency close to said tuned channel frequency; means for measuring the quality of the information carried by said RF signal; and means for updating said information stored in said memory with new information provided by both of said measuring means.

According to a second aspect, the invention suggests a signal processing arrangement comprising: a signal source for providing a radio frequency (RF) signal; means for tuning a channel frequency; means for retrieving information regarding radio frequency (RF) signals at said tuned channel frequency and at a channel frequency close to said tuned channel frequency from a memory; and means for disabling an RF amplifier if said information indicates that the magnitude of an RF signal at said tuned channel frequency is greater than a first predetermined threshold level or that the magnitude of an RF signal close to said channel frequency. tuned is greater than a second predetermined threshold level. Wherein the signal processing arrangement further comprises: means for receiving an information-bearing RF signal; means for measuring the magnitudes of the RF signals at respective ones of said tuned channel frequency and said channel frequency close to said tuned channel frequency; means for measuring the quality of the information carried by said RF signal; and means for ac2

ES 2 264 451 T3 updating said information stored in said memory with new information provided by both of said measuring means.

According to a third aspect, the invention suggests a signal processing method comprising the steps of: tuning a channel frequency; retrieving information regarding radio frequency (RF) signals at said tuned channel frequency and at a channel frequency close to said tuned channel frequency from a memory; and enabling an RF amplifier if said information indicates that the magnitude of an RF signal at said tuned channel frequency is less than a first predetermined threshold level and that the magnitude of an RF signal near said tuned channel frequency is lower than a second predetermined threshold level. Wherein the method further comprises the steps of: receiving an information-bearing RF signal; measuring RF signal magnitudes at respective ones of said tuned channel frequency and said channel frequency close to said tuned channel frequency; measuring the quality of the information carried by said RF signal; and updating said information stored in said memory (55) with new information obtained by both of said measurement steps.

According to a fourth aspect, the invention suggests a method for processing a signal comprising the steps of: tuning a channel frequency; retrieving from a memory (55) information regarding radio frequency (RF) signals at said tuned channel frequency and at a channel frequency close to said tuned channel frequency; and disabling an RF amplifier (116) if said information indicates that the magnitude of an RF signal at said tuned channel frequency is greater than a first predetermined threshold level or than the magnitude of an RF signal at said channel frequency. close to said tuned channel frequency is greater than a second predetermined threshold level. Wherein the method further comprises the steps of: receiving an information-bearing RF signal; measuring the magnitudes of the RF signals at the respective ones of said tuned channel frequency and said channel frequency close to said tuned channel frequency; measuring the quality of the information carried by said RF signal; and updating said information stored in said memory (55) with new information obtained by both of said measurement steps.

These and other aspects of the invention will be described in detail with reference to the accompanying drawings. In the drawings:

Figure 1 is a block diagram illustrating a portion of an analog / digital television signal receiver including a first exemplary embodiment of the signal processing arrangement in accordance with the principles of the present invention;

Figure 2 is a block diagram illustrating a portion of an analog / digital television signal receiver including a second exemplary embodiment of the signal processing arrangement in accordance with the principles of the present invention;

Figure 3 is a flow chart describing an exemplary mode of operation of the first embodiment as illustrated in Figure 1 in accordance with the principles of the present invention; and Figure 4 is a flow chart describing an exemplary mode of operation as illustrated in Figure 2 in accordance with the principles of the present invention.

The exemplifications set forth herein illustrate preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any way. In the various figures, the same or similar reference designations are used to identify the same or similar elements.

This application describes a first signal processing arrangement comprising a signal source, such as an antenna, for providing an information-bearing RF signal, such as an analog and / or digital television signal, a signal output point and control means, including an attenuator and / or an amplifier such as a low noise amplifier, together with RF switches associated therewith, coupled between the signal source and the signal output point to control the magnitude of the information-carrying RF signal in response to the quality of the information carried by the RF signal. The signal processing arrangement may further comprise determining means, such as a demodulator, coupled to the control means for determining the quality of the information carried by said RF signal. According to an exemplary embodiment described in detail below, such information quality is indicated by various signal parameters including automatic color control level (CAC), image / sound ratio (I / S) for reception of television signals. analog, and signal-to-noise (S / R), equalizer jacks and bit error rate (TEB) for reception of digital television signals. A method performed by the above arrangement is also described here.

Furthermore, this application describes a second signal processing arrangement comprising a signal source, such as an antenna, for providing an RF signal, such as an analog and / or digital television signal; a signal exit point; and first control means, including an attenuator and RF switches associated therewith, coupled between the signal source and the signal output to control the magnitude of the RF signal in response to the magnitude of the RF signal at the frequency tuned channel as well as an RF signal close to the tuned channel, including one adjacent or close to the tuned channel frequency. The signal processing arrangement may further comprise a memory for storing channel information regarding the magnitude of the RF signal for each signal that can be received over an entire frequency band, including the magnitude of the RF signal for the channel. which is tuned and those of the channels close to the tuned channel, and second control means including a microprocessor coupled to the first control means for controlling the first control means in response to channel information stored in memory. A method performed by this arrangement is also described here.

Referring now to the drawings, and more particularly to Figures 1 and 2, block diagrams 100 and 200 show two exemplary implementations.

ES 2 264 451 T3 res of booster / dimmer circuits 110 and 210, respectively, in conjunction with a receiver for analog / digital color television signals. The above first and second signal processing arrangements, as well as the methods performed by the respective ones of the arrangements, are equally applicable to each of the implementations illustrated in Figures 1 and 2.

Figure 1 depicts an exemplary implementation booster / attenuator circuit 110 in conjunction with an analog / digital television signal receiver. Digital and / or analog television signals over the air are received at an antenna (not shown) and then applied to the RF input point 22 of the UHF / VHF splitter 20 via an RF signal transmission line ( not shown) such as a coaxial cable. The UHF / VHF splitter 20 separates the UHF television signals from the VHF television signals in a frequency domain and supplies the UHF television signals to the attenuator switch 118 which is part of the booster / attenuator circuit 110. Although Figure 1 shows that the booster / attenuator circuit 110 is implemented in the UHF signal processing path, it can also be implemented in the VHF signal processing path in the same manner.

Attenuator switch 118 supplies UHF television signals to attenuator 112 (eg, 3 dB resistive RF attenuator) or booster switch 111 in response to an attenuator control signal from integrated circuit (IC) 30 phase-locked loop (BEF) that is generated by the microprocessor 50 and transmitted via the TC bus (Inter-Integrated Circuit bus). Boost switch 111 receives RN UHF signals from attenuator switch 118 and supplies them to tunable single-tuned filter (SU) 114 of booster / attenuator circuit 110 or tunable single-tuned filter (SU) 122, usually located at the input of the RF circuit in a television tuner of the television signal receiver, in response to an elevator control signal from phase locked loop (BEF) integrated circuit (IC) 30 that is generated by microprocessor 50 and transmitted on bus I²C.

The tunable single tuning (SU) filter 114 of the boost / attenuator circuit 110 attenuates undesirable signals that could cause cross-modulation interference. Filter 114 is designed with a wider bandwidth than typical of a standard tuner input filter 122. Such a design reduces loss such that the noise figure performance of amplifier 116 is not significantly degraded while providing some protection against interference. The tuning signal ST for the filter is generated by the digital / analog converter (CDA) integrated circuit (IC) 40 which is controlled by the microprocessor 50 via the I bus.²C. The tunable single tuning (SU) filter 114 also functions as a tunable impedance matching network between the RF input point 20 and the low noise amplifier 116 to provide better impedance matching between the antenna and the amplifier 116 low noise at a given frequency (for example, a receive frequency). Better impedance matching improves the voltage standing wave ratio (VSWR) between the antenna and the low noise amplifier 116 resulting in reduction of undesirable signal losses and impulse responses. The low noise amplifier 116 is driven by the elevator control signal from the phase locked loop integrated circuit (IC) 30 that is generated by the microprocessor 50 and transmitted on the I bus.²C. Although a fixed gain amplifier is used as the low noise amplifier 116 in Figure 1, a controlled gain amplifier can also be used with an appropriate gain control circuit. The output signal from the elevator switch 111 is applied to the tunable single tuning (SU) filter 122.

UHF tuner circuit 120 includes tunable single tuning (SU) filter 122, gain controlled RF amplifier 124, tunable dual tuning (SD) filter 126, mixer 142, local oscillator (OL) 146 of UHF, and the filter 152 of intermediate frequency (IF) of double tuning (SD). The gain of the gain-controlled RF amplifier 124 is controlled in response to the RF automatic gain control signal generated by the analog video and sound processing circuit 60 (for receiving analog signals) or by the power detector 179. (for digital signal reception). The UHF tuner circuit 120 converts UHF television signals into intermediate frequency (IF) television signals and is usually located in a tuner module of the television signal receiver.

The IF signals from the dual-tuned (SD) IF filter 152 are then processed in the IF signal processing circuit 150 that includes the IF amplifier 154, the surface acoustic wave (OAS) filter 156, and the amplifier. 158 Controlled Gain IF. The gain of the gain-controlled IF amplifier 158 is controlled in response to the IF automatic gain control (AGC) signal generated by the analog video and sound processing circuit 60 (for receiving analog signals) or by the detector. 179 power (for digital signal reception). The output signals from the gain-controlled amplifier 158 are applied to the subsequent analog signal processing circuit, which includes the analog video and sound processing circuit 60, and to the subsequent digital signal processing circuit 170, which includes the analog converter / digital 172, power detector 179, demodulator 174, equalizer 176, and error correction decoder 178.

Analog video and sound processing circuit 60 demodulates analog television signals, such as NTSC, PAL, and SECAM television signals, and generates RF and IF automatic gain control (AGC) signals that drive RF amplifier 124. gain controlled and gain controlled IF amplifier 158, respectively, in response to the amount (ie, magnitude) of the analog RF television signals. Analog video and sound processing circuit 60 includes an analog / digital converter and provides microprocessor 50 with parameter information representing such RF and IF automatic gain control (AGC) signals as digital data. Similarly, the analog video and sound processing circuit 60 provides the microprocessor

ES 2 264 451 T3

50, via bus I²C, of ​​the parameter information in digital form representing the automatic chroma control signal and the image-to-sound carrier ratio (I / S), each of which indicates different aspects of the image quality of the analog RF television signals.

The digital signal processing circuit 170 processes digital television signals such as QAM (Quadrature Amplitude Modulation), QPSK (Quadrature Phase-Shift Keying = Quadrature Phase Shift Keying) and HD VSB ( High Definition Vestigial Side Band = high definition residual side band). The analog / digital (A / D) converter provides digitized IF signals for demodulator 174 and power detector 179, both of which are usually located on a digital demodulator IC. The power detector 179 generates RF and IF automatic gain control (AGC) signals that control the gain-controlled RF amplifier 124 and the gain-controlled IF amplifier 158, respectively, in response to the amount (i.e., magnitude) of RF digital television signals. The power detector 179 supplies the microprocessor 50, via the I bus²C, of ​​the parameter information representing such RF and IF automatic gain control (AGC) signals. The determination of the automatic gain control (AGC) level is performed based on the digitized IF signals that have not yet been demodulated.

The demodulator 174 demodulates the digitized IF signals from the analog / digital (A / D) converter 172 and provides so-called "digital baseband signals." The demodulator 174 also generates the parameter information that represents the signal / noise ratio, which indicates one of the aspects of the image and sound quality of the RF digital television signals and provides the microprocessor 50, via the I bus²C, of ​​such information.

Equalizer 176 receives the digital baseband signals from demodulator 174 and attempts to correct their impulse responses. Impulse response can be degraded by transmission channel multipath effects such as antenna and tuner input circuitry imperfections. The equalizer 176 also generates the parameter information representing the filter taps, which indicates one of the aspects of the quality of the RF digital television signals, and provides the microprocessor 50, via the I bus²C, of ​​such information. By monitoring these EQ jacks, the above circuits can be selected to reduce the effects of antenna and tuner input imperfections.

The output signals from equalizer 176 are applied to error correction decoder 178 which performs error correction on digital baseband signals by the Reed-Solomon decoding method. The error correction decoder 178 generates the parameter information representing the bit error rate (TEB), which indicates one of the aspects of the image and sound quality of the RF digital television signals and provides the microprocessor 50 , by bus I²C, of ​​such information.

The output signals from the error correction decoder 178 are then processed by the subsequent signal processing circuit (not shown). The microprocessor 50, via the phase locked loop (BEF) integrated circuit (IC) 30 and the analog / digital converter (CAD) integrated circuit (IC) 40, controls the operations of the booster / attenuator circuit 110 based on the above information for various parameters in the manner described in Figure 3.

Figure 2 depicts another exemplary implementation of booster / dimmer circuit 210 in conjunction with an analog / digital television signal receiver. In this implementation, dimmer 112 with dimmer switch 118 is now located between RF input 22 and UHF / VHA splitter 20 so that both VHF and UHF television signals can be attenuated in response to the Attenuator control signal generated by phase locked loop integrated circuit (IC) 30 which is controlled by microprocessor 50 via the I bus²C. UHF television signals are filtered by tunable dual-tuned (SD) filter 114 and then amplified by low-noise amplifier 116 in response to the elevator control signal in the same manner as previously described in conjunction with Figure 1. VHF television signals, separated by UHF / VHF separator 20 from UHF television signals, are applied to VHF tuner circuit 130 which includes tunable single tuning (SU) filter 132, tuning amplifier 134 RF, tunable dual-tune (SD) filter 136, mixer 144, VHF local oscillator (OL) 144, and dual-tune (SD) IF filter 152. The dual tuned (SD) IF filter 152 is used for both VHF and UHF signal processing as a common element. The VHF tuner circuit 130 converts VHF television signals to IF television signals and is usually located in a tuner module of a television signal receiver. The functions of the IF signal processing circuit 150, the analog video and sound processing circuit 60, and the digital signal processing circuit 170 are the same as explained above in conjunction with FIG. 1. The microprocessor 50, via the phase locked loop (BEF) integrated circuit (IC) 30 and the digital / analog converter (CDA) integrated circuit (IC) 40, controls the operation of the boost / attenuator circuit 110 based on the above information for various parameters in the manner described in Figure 4.

Referring now to Figure 3, flow chart 300 describes an exemplary mode of operation of the booster / dimmer circuit 110 shown in Figure 1, which is supplemental or additional to the various modes of operation of the entire circuit described herein. In step 302, a television tuner is tuned to a particular UHF television channel. In step 304, microprocessor 50 retrieves previously stored automatic gain control parameter data from memory 55. The determination of the automatic gain control level for the individual channels that can be received in all television bands in VHF / UHF is usually performed when a user initially installs the television signal receiver, and such individual control information

ES 2 264 451 T3 automatic gain can be stored in a memory to form a so-called "memory scan list".

In step 306, microprocessor 50 compares the stored automatic gain control level for the tuned channel to a predetermined threshold. If the current automatic gain control level is not less than the threshold, then the boost / attenuator circuit 110 will be bypassed as indicated in step 314. However, if the level is lower than the threshold, then in step 308 the microprocessor 50 obtains from memory 55 the automatic gain control levels of the adjacent channel signals. In step 310, if one of the adjacent channel automatic gain control levels is stronger than a predetermined level, the boost / attenuator circuit 110 is bypassed. If not, in step 312, the low noise amplifier 116 is enabled and applied.

In step 316, the various parameters that indicate the quality of the information carried by the tuned television signal in UHF, such as equalizer jacks (EC), bit error rate (TEB), signal-to-noise ratio (S / R), automatic color control (CAC) and image / sound ratio (I / S) are measured as described above. If such parameters indicate that the signal quality is unacceptable, the attenuator 112 is enabled and applied as indicated in step 318. If such parameters indicate that the signal quality is acceptable, the television signal receiver continues to receive the tuned signal as indicated in step 326 and the channel data, including the measured parameter data as well as the present mode of operation. Boost / attenuator circuit 110 (ie, whether low noise amplifier 116 is enabled or not) for this particular channel can be stored in memory 55 as indicated in step 328.

In step 320, the various parameters above are measured again to determine the effect of attenuator 112. If the measured parameters indicate that picture and / or sound qualities have improved, attenuator 112 continues to be enabled and applied as indicated in the step 324. However, if the parameters indicate that the application of the attenuator 112 does not improve the image and / or sound qualities, the message "channel cannot be received" is displayed on the screen and such information is stored in memory 55 as indicated. at step 322.

Referring now to Figure 4, flow chart 400 describes an exemplary mode of operation of the booster / dimmer circuit 210 shown in Figure 2, which is supplemental or additional to the various modes of operation of the entire circuit described herein. In step 402, a television tuner is tuned to a particular VHF or UHF television channel. When a VHF channel is tuned, the various parameters that indicate the quality of the information carried by the tuned VHF television signal are measured. More specifically, these parameters are measured in two different modes of operation of the booster / attenuator circuit 210. In "Normal" mode, attenuator 118 is bypassed so that VHF television signals are applied directly to tunable SU filter 132 via UHF / VHF splitter 20, as indicated in step 412. In the "Select attenuator" mode, the attenuator

118 is enabled and applied to VHS television signals as indicated in step 416. Parameter data measured in the respective operating modes is stored in memory 55 as indicated in steps 414 and 418.

After measuring the various parameter information, the magnitude of the VHF television signals is determined by evaluating the automatic gain control (AGC) signals in step 422. If the VHF television signals are so weak that they could be inappropriate for proper reception, attenuator 118 is disabled and bypassed as indicated in step 426.

At step 420, the results of previous measurements in the different modes of operation are compared, and whichever mode provides a better picture and / or sound state continues to be used. That is, if the application of the attenuator 118 provides a better picture and / or sound state, the attenuator 118 is enabled and applied for reception of the tuned channel as indicated in step 424. If not, the attenuator 118 is bypassed as shown. indicated in step 426. At step 428, information representing the selected mode of operation (ie, use or not use of attenuator 118) for this particular television channel is stored in memory 55 for future access to this channel.

When a UHF channel is tuned, the various parameters that indicate the quality of the information carried by the tuned UHF television channel are measured in four different operating modes of the booster / attenuator circuit 210. In the "Normal" mode, both the attenuator 118 and the low-noise amplifier 116 are bypassed so that UHF television signals are applied directly to the tunable single-tuned (SU) filter 122 via the UHF / UHF splitter 20. VHF as indicated in step 472. In the "attenuator select" mode, attenuator 118 is enabled and applied to UHF television signals but low noise amplifier 116 is bypassed as indicated in step 476. In the "Select Elevator" mode, the low noise amplifier 116 is enabled and applied to UHF television signals but the attenuator 118 is bypassed, as indicated in step 480. In the "Select Attenuator + Elevator" mode ", Both attenuator 118 and low noise amplifier 116 are enabled and applied to UHF television signals. The parameter data measured in the respective operating modes is stored in memory 55 as indicated in steps 474, 478, 482, and 486.

In step 488, all measurement results in the respective four modes of operation are compared and whichever mode provides the optimal picture and / or sound state continues to be used as indicated in step 490. In step 492, the information representing the selected optimal performance of the boost / attenuator circuit 210 (that is, whether either or both of the attenuator 118 and the low-noise amplifier 116 is or is enabled or not), for this particular channel UHF television broadcast is stored in memory 55 for future access to this channel.

Although this invention has been described as having a preferred design, the present invention may be further modified within the spirit and scope.

ES 2 264 451 T3 ce of this description. Therefore, this application is intended to include any variations, uses, or adaptations of the invention that are within the limits of the appended claims.

For example, the booster / attenuator circuit 110 and its control methods can be used for analog / digital radio broadcast receivers, and the booster / attenuator circuit 110 can be located anywhere between an antenna and an RF input point. of the input circuit of a television tuner module. That is, the booster / dimmer circuit 110 could be implemented in a television signal receiver, it could be located in a separate module external to a television signal receiver, or it could be implemented in an antenna assembly.

The term "television signal receiver" used herein includes any television signal receiver with or without a display screen. For example, the term "television signal receivers" includes, but is not limited to, VCRs, DVD players, and set-top boxes.