JPH11502393A - TV / FM receiver for multimedia applications - Google Patents

Abstract

(57) Summary A receiver for receiving a first type of received signal, for example a TV signal, and a second type of received signal, for example an FM radio signal, is described. This receiver can be used in multimedia applications. In this receiver, the inputs TVIN, FMIN, SWIN have at least two inputs TVIN, FMIN to which a received signal can be supplied. One input TVIN may, for example, be coupled to a cable network to which the received signal is distributed. The other input FMIN may be used, for example, to plug in a simple wire antenna. In many cases, such a wire antenna will be satisfactory for receiving on-air received signals with acceptable quality. The present invention takes into account that on-air signals will not always be provided by the cable network. Since it has at least two inputs TVIN and FMIN, the reception is flexible.

Description

The present invention relates to a first type of received signal, for example a TV signal, and a second type of received signal, for example an FM radio signal. And a receiver for receiving the information. The invention also relates to a multimedia device incorporating such a receiver. The receiver can enhance the functionality of the multimedia device so that the device has, for example, TV and FM radio reception capabilities. The multimedia device may be in the form of a personal computer (PC) having slots into which various add-on cards are inserted. The receiver may be implemented with one of these add-on cards. Therefore, the PC can access the information transmitted by the FM radio or TV broadcasting station. BACKGROUND OF THE INVENTION A receiver capable of receiving TV and FM radio signals is described in U.S. Pat. No. 5,148,420. In this prior art receiver, both TV and FM radio signals are provided to a single tuner via a common RF input. This single tuner converts a particular received signal to a fixed intermediate frequency (IF) of about 40 MHz, which is common in TV reception. The IF signal generated by the tuner is processed differently for TV or FM radio reception. For TV reception, IF signals are processed very much like IF signal processing in most modern receivers. For FM radio reception, the IF signal is provided to a single-chip FM radio integrated circuit (IC) via a filter unit. In this FM radio IC, the IF signal is frequency-converted to obtain a nominally 10.7 MHz FM IF signal and processed in a more general manner. Although the prior art receiver can recover information from both TV and FM radio signals received at a common RF input, the prior art receiver has much less flexibility. DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a receiver whose information recovery is more flexible than the above-mentioned prior art receiver. According to one aspect of the present invention, there is provided a receiver as defined in claim 1. According to another aspect of the invention, a multimedia device has such a receiver. Yet another aspect of the present invention provides a tuner as defined in claim 4. The invention may be used for receiving both TV and FM radio signals. In one example of such use, a tuner that receives both TV and FM radio signals has an input having two inputs to which the received signals can be provided. One input may for example be connected to a cable network over which the received signal is distributed. The other input may be used, for example, to plug in a simple wire antenna. In many cases, such a wire antenna will be sufficient to receive local broadcasters with acceptable quality. The present invention takes into account that local broadcasters or any other on-air received signals will not always be provided by the cable network. The invention is particularly suitable for multimedia applications. As indicated at the outset, the receiver according to the invention may be incorporated in an add-on card. The flexibility provided by the present invention further enhances the functionality of the add-on card, which allows the add-on card to be used for a variety of multimedia applications. Advantageously, the input comprises a switch for effectively decoupling at least one of the two inputs from the tuner. This embodiment of the present invention takes into account that a user-created wire antenna has an indeterminate impedance. This uncertain impedance at the wire antenna input may affect the reception of cable network signals received via another input. The switch may isolate an undefined impedance from the tuner. Advantageously, a multi-band tuner is used to process the received signal in one of a plurality of band sections, depending on the frequency of the received signal, and a switch is coupled to the input of the one band section ing. Therefore, a received signal being processed in another band segment effectively bypasses the switch. This embodiment of the present invention takes into account that most switches actually have some degree of non-linearity. Such non-linearities can degrade reception quality, for example, by causing intermodulation. The invention will be described in more detail below with reference to an embodiment shown in the drawings. Furthermore, details of advantageous embodiments defined in the dependent claims are likewise described with reference to the illustrated embodiments. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an example of a tuner according to the present invention. FIG. 2 shows, in the form of a circuit diagram, an example of a switchable input unit for transmitting signals to various band divisions in the tuner of FIG. FIG. 3 shows, in the form of a circuit diagram, a preferred example of a switchable input unit for transmitting signals to various band divisions in the tuner of FIG. FIG. 4 is a conceptual diagram showing an example of a multimedia device having the tuner of FIG. In the figures, similar components have similar reference symbols. BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described by way of example with reference to the tuner of FIG. 1 capable of receiving both TV and FM radio signals. In this regard, specific aspects of the tuner of FIG. 1 are similarly discussed with reference to FIGS. 2 and 3, and an example of a multimedia application of the tuner of FIG. 1 is described with reference to FIG. Will be discussed. Finally, some supplements are made to show that the scope of the claimed invention is well beyond the examples shown in the figures. Referring to the tuner of FIG. 1, TV and FM radio signals are provided to inputs TVIN and FMIN, respectively. The tuner of FIG. 1 receives tuning control data TCD relating to a desired received signal, for example the frequency and type of the signal: TV or FM. In response to a desired received signal, the tuner of FIG. 1 supplies an intermediate frequency signal IFS at an output IFOUT. The tuner of FIG. 1 can operate in two modes: a TV mode when the desired received signal is a TV signal, or an FM mode when the desired received signal is an FM radio signal. In the TV mode, the intermediate frequency signal IFS has an intermediate frequency of 38.9 MHz, and is hereinafter abbreviated as TV-IF. In the FM mode, the intermediate frequency signal IFS has an intermediate frequency of 10.7 MHz, and is abbreviated as FM-IF hereinafter. The tuner of FIG. 1 is based on the so-called three-band concept. This means that the tuner of FIG. 1 has three separate frequency bands for processing each of the three associated frequency bands: high, mid and low TV signals. Each band division is composed of the following parts: input filter RFI-H / -M / -L, input amplifier RFA-H / -M / -L, band-pass filter BPF-H / -M / -L, mixer MIX- H / -M / -L, an oscillation circuit OSC-H / -M / -L, and an oscillation resonance circuit ORC-H / -M / -L. The suffixes -H, -M, and -L are used as reference symbols for these components to indicate whether the associated component belongs to a high band, a middle band, or a low band. The tuner of FIG. 1 may be embodied by using a mixer-oscillator integrated circuit MOIC of the type TDA 5736 manufactured by Philips Semiconductors, for example, in FIG. And has a part existing within the square. In the tuner of FIG. 1, the FM radio signal is processed in a low-frequency section. A switch SWIN couples the low band section to either the input TVIN or the input FMIN. In the first case, the TV signal is provided to the lower band, otherwise the FM radio signal is provided to the lower band. The position of the switch SWIN may depend on the mode of the TV or FM in which the tuner of FIG. 1 is operating. However, in some applications it is desirable to control the switch SWIN independently of the mode. For example, an FM radio signal may be present on both the input TVIN and the input FMIN. In this case, it would be advantageous to select the position of switch SWIN for best FM radio reception in FM mode. Some kind of diversity antenna is provided. One antenna may be, for example, a wire antenna coupled to the input FMIN, and the other antenna may be, for example, a VHF / TV antenna that can also receive FM radio signals via the antenna. In each band segment, the input filter RFI-H / -M / -L filters signals at frequencies that are far away from the desired received signal to avoid overloading the input amplifier RFA-H / -M / -L. Decay. The amplifier RFA-H / -M / -L is controlled by the gain control voltage Vagc. The bandpass filter BPF-H / -M / -L provides additional attenuation of the unwanted signal. The mixer MIX-H / -M / -L multiplies the desired reception signal by the oscillation signal OSS-H / -M / -L to cause a frequency shift of the desired reception signal. This oscillation signal OSS-H / -M / -L is composed of an oscillation circuit OSC-H / -M / -L and an oscillation resonance circuit ORC-H / -L that determines the frequency of the oscillation signal OSS-H / -M / -L. -M / -L. The mixer provides the intermediate frequency signal IFS via the intermediate frequency amplifier IFAMP. In each band division, the phase-locked loop circuit PLL controls the oscillation signal OSS-H / -M / -L of the relevant band division. The phase lock loop circuit PLL derives the tuning voltage Vtun from the tuner control data TCD and the oscillation signal OSS-H / -M / -L received via the oscillation signal amplifier OSSA as in the related art. The tuning voltage V tun is applied to the oscillation resonance circuit ORC-H / -M / -L. In the TV mode, the oscillation signal OSS-L in the low frequency range is set to a frequency that is the sum of the desired reception signal and the TV-IF (38.9 MHz). In the FM mode, the oscillation signal OSS-L is set to a frequency that is the sum of a desired reception signal and FM-IF (10.7 MHz). In each band section, the tuning voltage Vtun is also used to change the respective passband of the input filter RFI-H / -M / -L and the bandpass filter. Preferably, the passband should include the desired received signal. Otherwise, the desired received signal may be distorted and the unwanted signal may not be sufficiently attenuated. In the TV mode, the pass band should include the difference between the frequency of the oscillation signal and the TV-IF. In the FM mode, the passband should be centered on the difference between the frequency of the oscillating signal and the FM-IF. The position of the passband with respect to the frequency of the oscillating signal is tuned through the reception band and is referred to herein as tracking. The phase lock loop circuit PLL also supplies a mode switching signal TV / FM. In the low band section, the mode switching signal TV / FM is used to switch the oscillation resonance circuit ORC-L. The oscillation signal OSS-L is switched to a higher frequency in the TV mode than in the FM mode for a predetermined value of the tuning voltage Vtun. The respective passbands of the input filter RFI-L and the bandpass filter BPF-L are kept substantially constant for a given value of the tuning voltage Vtun. Thus, the frequency offset between the input filter RFI-L and the band-pass filter BPF-L on the one hand and the oscillation signal OSS-L on the other hand is switched. The frequency offset is preferably switched to TV-IF in TV mode and to FM-IF in FM mode. Furthermore, the mode control signal TV / FM preferably switches the pass bandwidth of the band-pass filter BPF-L in the low-pass section. In the TV mode, the bandpass filter BPF-L preferably has a fairly wide passband, for example, of 10 MHz, while in the FM mode, the passband is preferably fairly narrow, for example, of 1 MHz. FIG. 2 shows, in the form of a circuit diagram, an example of a switchable input for the transmission of signals to the low-, mid- and high-band sections at the inputs TVIN and FMIN in the tuner of FIG. It is shown. It should be noted that the switch SWIN shown in FIG. 1 is not electrically equivalent, but rather is functionally represented at the input of FIG. The input section in FIG. 2 includes a circuit for appropriately transmitting high-, mid-, and low-band TV signals from the input TVIN to the relevant band division without switching. The input of FIG. 2 is based on a prior art TV-RF input circuit described in the attached U.S. Pat. No. 4,851,796 and is incorporated herein by reference. The components of FIG. 2 corresponding to this prior art TV-RF input circuit are as follows: image trap 10, inductances L1, L2 and L3, and capacitor C. In FIG. 2, the reference numerals for the aforementioned components are the same as the reference numerals for the corresponding components in the drawing of U.S. Pat. No. 4,851,796 showing the prior art TV-RF input circuit. I have. According to this embodiment of the invention, the input section of FIG. 2 has four switching diodes D1, D2, D3 and D4, respectively. In the FM mode, switching diodes D2 and D4 conduct, while switching diodes D1 and D3 do not conduct. In the TV mode, the switching diodes D1 and D3 conduct, while the switching diodes D2 and D4 do not conduct. The four switching diodes D1, D2, D3 and D4 may be controlled by a mode control signal TV / FM represented in the tuner of FIG. However, in some applications it may be preferable to control the switch SWIN independently of the mode of the TV or FM in which the tuner is operating. That is, in these applications, a separate control signal is used for controlling the switch SWIN. In the input section of FIG. 2, in the TV mode, the switching diode D1 effectively short-circuits the input FMIN to which the FM radio signal is supplied. This in particular enhances the reception quality of high frequency TV signals, which can be explained as follows. The signal source connected to the input FMIN may not have a well-defined impedance. For example, it is often sufficient to receive a local FM radio station with sufficient quality, so it is quite possible that a user has only connected a single wire. The impedance of such a wire antenna is quite uncertain, and furthermore this impedance can vary significantly in the TV frequency band, for example in the range from 48 to 855 MHz. If the input FMIN is not sufficiently isolated from the TV-RF input circuit, this will affect the power matching between the signal source connected to the input TVIN and the associated input filter RFI-H / -M / -L. Maybe. In TV mode, switching diodes D2 and D4 provide isolation. However, in TV mode, switching diodes D2 and D4 are reverse biased and have parasitic capacitance. As a result, the insulation becomes weaker as the frequency increases. For example, depending on the wire antenna connected to the input FMIN, it may happen that an insufficient amount of TV signal power is transmitted to the associated input filter. Particularly in this sense, high-band TV signals are easily affected. The above problem is solved in TV mode by effectively shorting the input FMIN. At the input of FIG. 2, the isolation is provided by the switching diodes D2 and D4 arranged in a back-to-back configuration, as already mentioned. This additional feature also enhances the reception quality of the high band signal, which can be explained as follows. In practice, the parasitic capacitance of the insulation of the input FMIN, for example, may combine with the parasitic inductance of the connection to form a parasitic resonant circuit causing a mismatch. By halving the parasitic capacitance, for example, a parasitic resonance circuit can be tuned to obtain satisfactory power matching. The input of FIG. 2 has a resistor R2 in series with the switching diode D3. Depending on the state of the switching diode D3, the resistor R2 may or may not affect the characteristics of the input filter RFI-L, as shown in detail. The input filter RFI-L is basically a parallel resonance circuit and includes an inductance L4. In the FM mode, the switching diode D3 does not conduct, and thus the resistor R2 is effectively isolated from the parallel resonant circuit, which has a much higher Q. However, in the TV mode, the switching diode D3 conducts, and the resistor R2 effectively reduces the Q of the parallel resonance circuit of the input filter RFI-L. This has the advantageous effect that in FM mode the input filter RFI-L has a narrower bandwidth than in TV mode. In the input section of FIG. 2, the input FMIN is coupled to switching diodes D1 and D4 via an FM input filter. The FM input filter includes two inductances L5 and L6 and a capacitance C1. The components of FIG. 2 without reference symbols will be readily understood by those skilled in the art, but have been used to couple AC and / or DC signals as appropriate. As a result, these components need not be discussed further herein. FIG. 3 shows, in the form of a circuit diagram, a preferred input section in the tuner of FIG. 1 for transmitting signals at the inputs TVIN and FMIN to the low-pass section, the mid-pass section and the high-pass section. . Like the input of FIG. 2, the input of FIG. 3 is based on the prior art TV-RF input circuit described in US Pat. No. 4,851,796. However, in accordance with this embodiment of the present invention, at the input of FIG. 3, the low frequency TV signal at the input TVIN is transmitted to the low frequency section in a different manner than the input of FIG. . In the input unit shown in FIG. 3, the low-frequency TV signal is supplied to the input filter RFI-L via the input filter RFI-H in the high frequency band. FIG. 3 shows in detail the input filter RFI-H in the high band section where the low band TV signal is transmitted. The input filter RFI-H includes an inductance LH, a varicap diode CHvar, and a capacitance CHpad, and these constitute a parallel resonance circuit. The signal of the parallel resonance circuit is extracted through a series arrangement of the inductance LHtap and the capacitance CHtap. The inductance LH in the input filter RFI-H should have a value suitable for tuning the high frequency parallel resonant circuit. Thus, even if the LH has a fairly small impedance in the low band, it can be approximated as a short circuit in the low band. The input of FIG. 3 has three switching diodes D1A, D2A and D3A instead of the four of the input of FIG. When the switching diode D1A is conducting, one end of the parallel resonant circuit of the input filter RF1-H is effectively coupled to ground. However, when the switching diode D1A is not conducting, the low-frequency TV signal may be transmitted to the input filter RFI-L via the input filter RFI-H. For such a transmission, the switching diode D2A should be in a conducting state. When switched to a non-conducting state, the switching diode D3A provides satisfactory isolation of the input FMIN from the TV-RF circuit. The switching diode for effectively shorting the input FMIN does not appear at the input of FIG. 3 as does the switching diode D1 of FIG. The input section of FIG. 3 can be divided into four switching states: TV low range, TV mid range, TV high range and FM. Table 1 below lists the relationship between the switching states and the state of each of the three switching diodes individually. In Table 1, 0 indicates that the associated switching diode is non-conductive, and 1 indicates that it is conductive. In FIG. 3, each of the three switching diodes D1A, D2A and D3A receives an individual control signal S (D1A), S (D2A) and S (D3A), respectively. These control signals can be obtained from a phase locked loop circuit PLL via, for example, a band switching logic circuit (not shown). In the high TV switching state, any uncertain impedance at the input FMIN is very well isolated from the high frequency section, since all three switching diodes D1A, D2A and D3A effectively contribute to the isolation. In the switching state of the high TV range, the switching diodes D2A and D3A do not conduct, and the switching diode D1A conducts. In the FM switching state, the switching diode D3A conducts to transmit the FM radio signal at the input FMIN to the lower band. Switching diode D1A and switching diode D2A do not conduct to insulate input TVIN from the low-pass section. At the input of FIG. 3, the inductance L1A is connected in series with the resistor R2, and this function has already been described with reference to FIG. The inductance L1A tunes the input filter RFI-L differently in the TV mode and the FM mode. Referring to the tuner of FIG. 1, the tuning difference may be advantageously used as a result of switching the passband of the bandpass filter BPF-L to compensate for any detuning of the filter. With an appropriate value of inductance L1A, the passbands of input filter RFI-L and bandpass filter BPF-L are fairly matched. The components of FIG. 3 without reference symbols will be readily understood by those skilled in the art, but are used to couple AC and / or DC signals as appropriate. As a result, these components need not be discussed further herein. FIG. 4 shows an example of a multimedia device having the tuner TUN of FIG. The tuner TUN of FIG. 1 is incorporated in an add-on card PCAO, which is plugged into a holder HOL of the add-on card of the multimedia device. Apart from the tuner TUN of FIG. 1, the add-on card includes a TVIF signal processing circuit TVIFC and an FMIF signal processing circuit FMIFC. The latter circuit receives the intermediate frequency signal IFS supplied by the tuner TUN of FIG. 1 via the IF separation filter IFSF. The tuner TUN, the IF separation filter IFSF, and the TVIF signal processing circuit TVIFC in FIG. 1 are housed in a shielded metal box SMB. This shielded metal box SMB containing the components described above may be manufactured in this way and sold to an add-on card manufacturer. The multimedia device of FIG. 4 includes a user interface UIF, a control unit CCU, a video display device PDD, and an audio reproduction unit SRU. The user selects a desired received signal through the user interface UIF. For example, a user can enter a program number with a keyboard that is part of the user interface UIF. The control unit CCU effectively controls the add-on card PCAO so that the tuner TUN of FIG. 1 selects a desired received signal. For example, the control unit CCU gives instructions on the frequency of the desired received signal and the type of the signal: FM or TV, stored in a memory (not shown). These instructions are supplied to the tuner TUN of FIG. 1 in the form of tuner control data TCD. The add-on card PCAO provides, for example, audio and / or video information obtained from the desired received signal, which can be further processed in the control unit CCU. The audio and / or video information is provided to the user via the audio reproduction unit SRU and the video display device PDD, respectively. Obviously, the invention can be embodied in a different way than the embodiments described above. In this regard, any reference signs in the claims shall not be construed as limiting the relevant claim. Some final additions are made to show that the scope of the claimed invention is well beyond the embodiments described above. It should be noted that the present invention is not limited to combined TV and FM radio reception, two different types of received signals or two inputs such as inputs TVIN and FMIN. More inputs can be used if desired. Furthermore, the invention is not limited to multimedia applications. The invention can be used in any device having a receiver, such as a TV receiver and a video tape recorder. It should likewise be noted that the invention is not limited to the concept of a three-band tuner as shown in FIG. In principle, the invention may be applied to any tuner concept, for example a two-band tuner concept. It should further be noted that the present invention is not limited to the use of RF-TV input circuits as described in U.S. Pat. No. 4,851,796. Finally, it should be noted that more or less switching diodes can be used. For example, in the input section of FIG. 2, one of the switching diodes D2 and D4 may be omitted. The switching diode D4 may be replaced by, for example, a capacitor.

Claims (1)

[Claims] 1. A receiver for receiving first and second types of received signals,   An input unit (TVIN, FMIN, SWIN) for receiving a reception signal;   A tuner (T) for providing an intermediate frequency signal (IFS) according to the received signal. UN)   When the reception signal of the first type is received, the intermediate frequency signal (IFS) is A first intermediate frequency signal processor (TVIFC) coupled for processing;   When the second type reception signal is received, the intermediate frequency signal (IFS) is A second intermediate frequency signal processor (FMIFC) coupled for processing. Receiver   The input unit (TVIN, FMIN, SWIN) is used to receive a received signal. A receiver comprising a number input (TVIN, FMIN). 2. The input unit (TVIN, FMIN, SWIN) is connected to the tuner (TUN). For effectively decoupling at least one of said plurality of inputs from The receiver according to claim 1, comprising a switch (SWIN). 3. The tuner (TUN) includes a plurality of sections ((TUN)) depending on the frequency of the received signal. RFI-L., RFI-M., RFI-H.) To process the received signal. A band-type tuner, wherein the switch (SWIN) includes the plurality of sections. 3. An input according to claim 2, wherein the input is coupled to one of the inputs (RFI-L ..). On-board receiver. 4. A tuner for receiving first and second types of reception signals,   An input unit (TVIN, FMIN, SWIN) for receiving a reception signal;   A mixer for providing an intermediate frequency signal (IFS) in response to the received signal; In a tuner having a shaker device (MOIC),   The input unit (TVIN, FMIN, SWIN) may be supplied with the reception signal. A tuner having a plurality of inputs (TVIN, FMIN). 5. A receiver as claimed in claim 1 and a method for controlling the receiver and processing data signals. A multimedia device having a control unit (CCU).