Patent Application
20060276149
This invention relates in general to radio-frequency signal tuners and, more particularly, to a multi-band digital broadcast tuner.
Developments in the communication industry over recent years have led to the introduction of portable devices that provide a wide variety of communication services. Combined with increasing customer expectations for service quality, this trend has caused an increased demand for devices that provide substantial signal processing power but that are also small and require only a limited amount of power to operate. For example, the introduction of digital video standards for portable devices, such as Digital Video Broadcast-Handheld (DVB-H), has led to the development of handheld devices that can receive and display digital video and audio signals. However, the reception and processing of broadcast digital video and broadcast digital audio signals in conventional handheld devices may require a sizeable collection of circuits and/or components. These components can require significant amounts of space, dissipate a substantial amount of power, and add excessive complexity to the handheld device.
In accordance with the present invention, the disadvantages and problems associated with signal tuners have been substantially reduced or eliminated. In particular, a multi-band broadcast tuner is provided.
In accordance with one embodiment of the present invention, a system for receiving radio-frequency signals includes a first input path, a second input path, a selector, and a mixer. The first input path is capable of transmitting to the mixer a first input signal propagating in a first portion of the radio-frequency spectrum, while the second input path is capable of transmitting to the mixer a second input signal propagating in a second portion of the radio-frequency spectrum. The selector is capable of selectively coupling one of the first input path and the second input path to the mixer. Additionally, the mixer is capable of receiving an input signal and downconverting at least a portion of the input signal that is propagating within a selected frequency range. The mixer is also capable of outputting the downconverted portion of the input signal.
Important technical advantages of certain embodiments of the present invention include power saving benefits, space-saving packaging, and greater operational flexibility. Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.
For a more complete understanding of the present invention and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
Tuner 20 receives video, audio, and/or any other appropriate form of radio-frequency (RF) signals, including any suitable form of digitally-encoded RF signals, from antennas 50 and isolates, within these signals, the portions of these signals that are being transmitted within a particular frequency range or “channel.” Tuner 20 then outputs the isolated portions to demodulator 30 through one or more tuner output ports 24 as tuned signals 92. In particular embodiments, tuner 20 receives video signals from antennas 50 as single-ended input signals and outputs differential quadrature signals to demodulator 30. In particular embodiments, tuner 20 represents a single integrated circuit. Tuner 20 may however represent any appropriate combination of hardware and/or software suitable to provide the described functionality. The contents and operation of a particular embodiment of tuner 20 are described in greater detail below with respect to
Demodulator 30 receives, at demodulator input ports 32, signals output by tuner 20 and extracts information from these signals based on the modulation scheme for which system 10 is configured. Demodulator 30 then outputs the extracted information to decoder 40 through demodulator output port 34 as encoded data 94. In particular embodiments, demodulator 30 is configured to demodulate information modulated using code orthogonal frequency-division multiplexing (COFDM). Demodulator 30 may however be configured to demodulate information modulated using any appropriate technique. Demodulator 30 may represent any appropriate combination of hardware and/or software suitable to provide the described functionality.
Decoder 40 decodes information received from demodulator 30 based on the coding scheme for which system 10 is configured. Decoder 40 then outputs decoded data 96 to display 70. In particular embodiments, decoder 40 is configured to decode information encoded using the Motion Picture Experts Group-2 (“MPEG-2”) standard. Decoder 40 may however be configured to decode information encoded using any appropriate technique. Decoder 40 may represent any appropriate combination of hardware and/or software suitable to provide the described functionality.
Antennas 50 receive radio-frequency signals from terrestrial and/or satellite sources and transmit these signals to inputs of tuner 20 as single-ended inputs. Antennas 50 may represent and/or include any appropriate components to receive radio-frequency signals. In particular embodiments, system 10 is configured to receive signals in multiple bands of the radio-frequency spectrum, and display device may include a separate antenna 50 for each frequency band system 10 is capable of receiving. Although the description below focuses on embodiments of system 10 in which tuner 20 receives input signals 90 through antennas 50, particular embodiments of system may omit antennas 50. In such embodiments, tuner 20 may receive input signals 90 from other components of system 10 or from external cable transmission systems.
In the illustrated embodiment, system 10 includes an ultra high frequency (UHF) antenna 50a through which system 10 receives signals having a frequency within an appropriate portion of the UHF spectrum, a very high frequency (VHF) antenna 50b through which system 10 receives signals having a frequency within an appropriate portion of the VHF spectrum, and an L-band antenna 50 through which system 10 receives signals having a frequency within an appropriate portion of the L-Band. For example, particular embodiments of system 10 may be configured to receive signals within the 470 MHz to 2 GHz sub-band of the UHF spectrum on UHF antenna 50a, to receive signals within the 150 MHz to 260 MHz sub-band of the VHF spectrum on VHF antenna 50b, and to receive signals within the 1.5 to 1.6 GHz sub-band of the L-Band spectrum on L-Band antenna 50c. As a result, in particular embodiments, tuner 20 may be operable to receive signals within a wide sub-band from particular antennas 50 and within a narrow sub-band from the same or other antennas 50. Moreover, as described in greater detail below, tuner 20 may be capable of tuning across both the wide sub-bands and narrow sub-bands using a common mixer and/or other shared components.
Although
Display 70 displays video and/or audio information received by system 10 to a user of system 10. For the purposes of this description and the claims that follow, display 70 may display information to the user by outputting audio, video, and/or text of any appropriate form to the user. Display 70 may represent and/or include any suitable hardware and/or software to provide the displayed information to the user. Display 70 may include a light-emitting diode (LED) display, a liquid crystal display (LCD), a speaker, and/or any other components appropriate based on the type of information system 10 is configured to receive and/or display.
User interface 80 supports interaction between the user and system 10. For example, in particular embodiments, user interface 80 may include suitable components to allow the user to select a radio or television channel to display. System 10 may include buttons, switches, a keypad, a dial, and/or any other appropriate components to allow the user to control operation of system 10. As shown by dotted-line box 12, user interface 80 may be configured to provide control signals to any or all of tuner 20, demodulator 30, and decoder 40, and these control signals may be propagated between the components in any appropriate manner. For example, in particular embodiments, user interface 80 communicates to demodulator 30 a channel selected by a user of system 10. Demodulator 30 may then indicate the selected channel to tuner 20.
In operation, system 10 receives input signals 90 from terrestrial or satellite sources at antennas 50, and antennas 50 transmit these input signals 90 to tuner 20. Tuner 20 receives input signals 90 from antennas 50 as single-ended signals at tuner input ports 22. Because tuner 20 receives inputs from antennas 50 as single-ended signals, certain components, such as a balun, may be omitted from system 10 that might be necessary or preferable if tuner 20 was limited to receiving input signals 90 as differential signals. As a result, tuner 20 and/or system 10 may be able to operate with fewer components, thereby reducing the size of system 10. Additionally, use of single-ended inputs may allow lower noise figures to be achieved, improving performance of particular embodiments of system 10 when signal reception is weak.
As described in greater detail below with respect to
More specifically, in the illustrated embodiment, tuner 20 generates output signals that include an in-phase portion of the selected frequency component or channel (indicated in
Use of differential output signals may allow tuner 20 to be utilized with many commonly-available configurations of demodulator 30 without the addition of components to convert a single-ended output of tuner 20 to the differential signal appropriate for use with such demodulators 30. As a result, the size of system 10 in particular embodiments may be even further reduced without sacrificing compatibility between tuner 20 and commonly-available demodulators 30.
Demodulator 30 receives the tuned signals 92 output by tuner 20 and demodulates these signals to produce an encoded data 94. In particular embodiments, demodulator 30 receives tuned signals 92a-d as two pairs of differential signals and independently demodulates the information transmitted in the two differential pairs. Demodulator 30 then combines the demodulated information form the two differential pairs to form encoded data 94.
Decoder 40 decodes encoded data 94 output by demodulator 30 to produce decoded data 96 in a form that can be displayed by display 70. After decoding encoded data 94, decoder 40 transmits decoded data 96 to display 70. In particular embodiments, decoder 40 may also perform digital-to-analog conversion on decoded data 96 before transmitting decoded data 96 to display 70. Display 70 then displays decoded data 96 to the user. As noted above, display 70 may display decoded data 96 by generating any appropriate combination of video, audio, and or text information for the user based on decoded data 96 and/or information included in decoded data 96.
Using user interface 80, the user may change the selected frequency or channel displayed by system 10. For example, user interface 80 may include a dial that the user can operate to change the frequency or channel displayed by system 10. In response, tuner 20 may begin isolating the newly-selected frequency or channel and may output components of the relevant input signal 90 having the newly-selected frequency or within the newly-selected channel. If the newly selected frequency or channel is on a different band (and, thus, is received on a different antenna 50), tuner 20 may also select a different input signal 90 to tune. User interface 80 may also include a power switch, volume control, and/or other components to allow the user to control operation of system 10.
Because tuner 20 is capable of receiving input signals from antennas 50 as single-ended inputs and outputting differential outputs, tuner 20 may be capable of operating with commonly-available antennas 50 and demodulators 30 while limiting the number of additional components needed to interface tuner 20 with antennas 50 and demodulator 30. Additionally, as described further below, the use of a common tuner 20 for the multiple antennas 50 connected to system 10 may result in a system 10 with fewer components and or a smaller tuner 20. As a result, the inclusion of particular embodiments of tuner 20 in display devices 10 may provide several advantages.
RF stage 110 receives input signals 90 from tuner input ports 22 and processes input signals 90 to facilitate tuning of input signals 90. RF stage 110 may process input signals in any appropriate manner based on the characteristics of the input signals 90 received by tuner 20 and the configuration of mixers 122 and/or other components of tuner 20. Moreover, RF stage 110 may include any suitable components to perform the relevant processing.
In the illustrated embodiment, RF stage 110 includes a plurality of paths 100 connecting each of tuner input ports 22 to a signal converter 118. Signal converter 118 couples one of paths 100 to quadrature mixer 120 based on a frequency or channel selected by the user and/or other appropriate factors. Additionally, signal converter 118 may convert the input signals 90 received by RF stage 110 in an appropriate manner to facilitate the input of these signals to quadrature mixer 120. In particular embodiments, signal converter 118 converts single-ended input signals 90 received by tuner 20 into a differential pair of preprocessed signals 124a and 124b. Additionally, in particular embodiments, signal converter 118 may also perform voltage-to-current conversion on input signals 118 and output preprocessed signals 124 as current mode signals. Moreover, signal converter 118 may induce gain in the selected signal providing additional control over the signal strength and distortion characteristics of preprocessed signal 124.
Although
The presence of attenuators 102 and bandpass filters 104 and 108 in paths 100a and 100b may facilitate reception of input signals 90 across a wide sub-band through paths 100a and 100b. As a result, in particular embodiments, RF stage 110 may include one or more paths (such as paths 100a and 100b) configured for use with antennas 50 receiving signals across a wide sub-band and also one or more paths (such as 100c and 100d) configured for use with antennas 50 receiving signals across a narrow sub-band. Moreover, because of the various configurations of paths 100, tuner 20, in particular embodiments, may be capable of receiving and tuning broadband and/or narrowband input signals 90 that are transmitted over a very wide sub-band of the RF spectrum and also be capable of receiving and tuning broadband and/or narrowband input signals 90 that are received over a very narrow sub-band of the RF spectrum without substantial deterioration in performance. For example, in particular embodiments, tuner 20 may be capable of receiving and tuning signals transmitted over an approximately 1.5 GHz sub-band (from 470 MHz to 2 GHz) of the UHF band of the RF spectrum as well as receiving and tuning signals transmitted over an approximately 100 MHz sub-band (150 MHz to 260 MHz) of the VHF band of the RF spectrum without substantial deterioration of performance when tuning within either sub-band. Although these values are provided for purposes of illustration, tuner 20 may, in particular embodiments, be configured to allow tuning across any appropriately sized sub-bands of any portions of the RF spectrum.
Each of paths 100 is operable to connect a particular tuner input port 22 to signal converter 118. Moreover, in particular embodiments, multiple paths 100 may connect a particular tuner input port 22 to signal converter 118. In such embodiments, the multiple paths 100 may each provide different forms of processing to the input signals 90 received by that tuner input port 22. For example, in the illustrated embodiment, both 100a and 100b connect tuner input port 22a to signal converter 118. Based, in part, on the presence of the additional attenuator 102 in first path 100a, first path 100a, however, may be more tolerant of interference, while second path 100b may allow for more robust frequency reception. Depending on strength of signal and/or other operational considerations, the user or system 10 itself may select an appropriate one of path 100a and path 100b to provide UHF signals to mixers 122. Furthermore, as described further below, gain and attenuation elements may be distributed throughout particular paths 100 to allow tuner 20 to be configured for an optimal tradeoff between distortion and noise.
Additionally, in particular embodiments, tuner 20 may be housed in a single integrated circuit and signal converter 118 may be coupled to a single reference voltage 192 provided by components external to tuner 20 for multiple bands. In general, reference voltage 192 may be provided by any appropriate component or collection of components. In particular embodiments, reference voltage 192 is provided by a charged capacitor. In alternative embodiments, reference voltage 192 may be provided by a bandgap voltage generator.
Oscillator 140 generates a periodic signal at a tuning frequency selected by the user and provided to oscillator 140 by programmable interface 150. Additionally, although not shown in
Quadrature generator 142 receives tuning signal 144 from oscillator 140 and induces a ninety-degree (90°) phase shift in a copy of tuning signal 144 to produce a shifted tuning signal 146. Quadrature generator 142 then outputs a copy of the original tuning signal 144 and shifted tuning signal 146 to mixers 122. Additionally, when appropriate based on the selected channel, quadrature generator 142 may act as a frequency divider to reduce the frequency of tuning signal 144 to a level appropriate to downconvert the selected channel. For example, in particular embodiments, quadrature generator 142 may be capable of dividing the frequency of tuning signal 144 output by oscillator 140 by any multiple of two from two to N (for example, in particular embodiments, N may equal 32). As a result of this flexibility, such embodiments of tuner 20 may be capable of tuning channels received in several different bands of the radio-frequency spectrum. Quadrature generator 142 may include any appropriate combination of hardware and/or software to provide the described functionality.
Quadrature mixer 120 includes in-phase mixing cell 122a and quadrature mixing cell 122b. Mixers 122 mix preprocessed signals 124 output by RF stage 110 with a tuning signal 144 generated by oscillator 140 to produce a downconverted version of a selected input signal 90 received by tuner 20. As discussed further below,
Baseband filters 130a-c and 130d-f receive downconverted input signals from mixers 122. Baseband filters 130 filter out high-frequency components of the downconverted signal to produce an output that includes the component of the selected input signal 90 that was transmitted at the desired reception frequency. In the illustrated embodiment, baseband filters 130 each provide this output as a pair of differential tuned signals 92. In particular embodiments, baseband filters 130 may be configured to exhibit a passband that is sized based on the minimum channel-spacing used in the signals received at antennas 50. In general, however, baseband filters 130 may include any appropriate combination of hardware and/or software suitable to provide the described functionality. In particular embodiments, it may be desirable, for purposes of optimizing the range dynamic range of output signals 92, to configure baseband filters 130 such that the noise induced in downconverted signals 126a-d passing through baseband filters 130 is independent of the gain induced by baseband filters 130 and/or of the magnitude of downconverted signals 126.
Additionally, particular embodiments of tuner 20 may facilitate more granular control of baseband filters 130 to provide better noise and linearity characteristics in output signals 92. For example, in the illustrated embodiment, baseband filters 130 may each be associated with a frequency control module 194 and a gain control module 196. Each frequency control module 194 may be used to adjust the cutoff frequency of the associated baseband filter 130 independently of the cutoff frequency of the remaining baseband filters 130. Similarly, each gain control module 196 may be used to adjust the variable gain of the associated baseband filter 130 independently of the variable gain set for the remaining baseband filters 130. As a result of these independent control features, may be able to fine-tune the gain and frequency characteristics of output signals 92. For example, in particular embodiments, the gains induced by baseband filters 130a-c and 130d-f do not impact noise characteristics of output signals 92 in a uniform manner. As a result, in such embodiments, tuner 20 may optimize noise reduction by reducing the gain induced by baseband filters 130c and 130f as much as possible, and then proceeding to reduce the gain induced by baseband filters 130b and 130e if more noise reduction is needed. Frequency control module 194 and gain control module 196 may represent any appropriate combination of hardware and/or software operable to provide the described functionality.
Programmable interface 150 allows a user or other elements of system 10 to configure operation of tuner 20. In particular embodiments, programmable interface 150 represents a serial digital bus and control logic capable of adjusting operation of various components of tuner 20 based on control information transmitted on the serial digital bus. In general, however, programmable interface 150 may include any appropriate collection of hardware and/or software to allow tuner 20 to receive control information from the user or other elements of system 10. In particular embodiments, programmable interface 150 may be configured to communicate with portions of user interface 80. For example, programmable interface 150 may receive, from user interface 80, information specifying a frequency or channel selected by the user. Additionally, programmable interface 150 may receive information from other elements of system 10, such as demodulator 30, to allow that device to set power-consumption settings and other operational parameters of system 10. Programmable interface 150 may be configured to provide control signals to any or all of the elements of RF stage 110 and baseband stage 170, and these control signals may be propagated between and within the two stages in any appropriate manner.
In operation, tuner 20 receives input signals 90 from antennas 50 as single-ended signals at input ports 22. Input signals 90 are transmitted to signal converter 118 over paths 100. Paths 100, in particular embodiments, may include a number of distributed gain and attenuation elements. Because the impact of signal gain and attenuation may vary at different locations along paths 100, the distribution of gain and attenuation elements along paths 100 may provide system 10 greater ability to achieve an optimal balancing between signal strength and distortion.
For example, in the illustrated embodiment, path 100a includes variable attenuator 102, bandpass filter 104, low-noise amplifier 106, bandpass filter 108 and attenuator 112 coupled in series. In particular embodiments, bandpass filters 104 and 108 and low-noise amplifier 106 may each be capable of inducing a variable gain in signals they receive, and attenuators 102 and 112 may be capable of inducing a variable attenuation in signals they receive.
As a result, system 10 may be able to achieve an optimal tradeoff between distortion and signal strength by selectively configuring the variable components along a particular path 100. For example, in particular embodiments, if distortion occurs in output signals 92a, attenuating the associated input signal 90 at attenuator 112 (e.g. by increasing the attenuation induced by variable attenuator 112) may result in a greater reduction in distortion for a given reduction in signal strength than attenuating input signal 90 at attenuator 102 due to the proximity of attenuator 112 to signal converter 118. Thus, the finer control facilitated by distributing gain and attenuation elements at multiple locations along particular paths 100 may facilitate improved control of tuner 20.
Based on input received from programmable interface 150, signal converter 118 selects a particular path 100 to output. Depending on the configuration of system 10, signal converter 118 may, by selecting a particular path 100 to output, select the antenna 50 from which tuner 20 receives the input signal. For example, in the illustrated embodiment, signal converter 118 may, by selecting between paths 100b-d, select between input signals 90 received from antennas 50a-c respectively.
Additionally, in particular embodiments, multiple paths 100 may couple a particular antenna 50 to signal converter 118. In such embodiments, signal converter 118 may also, by selecting a particular path 100, select the processing to be performed to the selected input signal 90. For example, in the illustrated embodiment, both paths 100a and 100b couple UHF antenna 50a to signal converter 118. However, as a result of the inclusion of attenuator 102 prior to bandpass filter 104, path 100a may represent, by comparison to path 100b, a low-distortion path that exhibits better linearity characteristics than path 100b. Similarly, as a result of the absence of a comparable attenuator before bandpass filter 104 in path 100b, path 100b may represent, by comparison to path 100a, a high-sensitivity path to facilitate tuning of weaker signals in low-noise settings. Thus, signal converter 118 may also, by selecting between paths 100, select the conditioning to be performed on the relevant input signal 90. As a result, tuner 20 may be reconfigured dynamically to adjust to changes in operating conditions or performance requirements.
Furthermore, in particular embodiments, signal converter 118 may also convert the selected input signal 90 from a single-ended signal to a differential signal pair. Signal converter 118 than outputs the selected signal, which is shown in
Oscillator 140 provides mixers 122a and 122b with a tuning signal 144 having a frequency set by the user using user interface 80. Based on tuning signal 144, quadrature mixer 120 downconverts a particular frequency component or channel within preprocessed signals 124 so that the relevant frequency or channel possesses a lower center frequency. More specifically, mixers 122a and 122b downconvert the relevant frequency component or channel so that the relevant frequency component or channel is centered at the desired baseband frequency. In particular embodiments, this frequency may be substantially near 1 Hz. After downconversion, preprocessed signals 124 are output by mixers 122a and 122b as downconverted signals 126.
After downconverted signals 126 are output by mixers 122, baseband filters 130 filter out all frequency components outside a particular desired passband, thereby producing tuned signals 92. As noted above, these tuned signals 92 may, in particular embodiments, represent a pair of quadrature, differential signals.
In particular embodiments, each baseband filter 130 is additionally capable of inducing a variable gain in downconverted signals 126. As a result, tuner 20 may be configured to further reduce noise in output signals 92 by adjusting the gain induced by baseband filters 130. Furthermore, because particular embodiments of tuner 20 include multiple baseband filters 130 at the output of each mixing cell 122, baseband stage 170 may provide finer control of noise by allowing distributed gain control similar to that described with respect to RF stage 110.
Additionally, in particular embodiments, programmable interface 150 may, in addition to receiving an indication of the selected frequency or channel, may be capable of receiving other inputs that affect operation of tuner 20. As one example, in particular embodiments, programmable interface 150 may receive power parameters that specify a power-consumption mode or other power-related settings for tuner 20. Programmable interface 150 may, in response to receiving such power parameters, power down one or more elements of tuner 20 and/or otherwise adjust aspects of the operation of tuner 20 related to power-consumption based on the power parameters received by programmable interface 150.
As another example, in particular embodiments, programmable interface 150 may receive linearity parameters that specify linearity settings for tuner 20. Programmable interface 150 may, in response to receiving such linearity parameters, vary the gain or attenuation induced by amplifiers 106, attenuators 102, 112, 114, and 116, or baseband filters 130 and/or otherwise adjust aspects of the operation of tuner 20 related to linearity based on the received linearity parameters. Similarly, in particular embodiments, programmable interface 150 may receive noise parameters that specify noise settings for tuner 20. Programmable interface 150 may, in response to receiving such noise parameters, adjust the operation of amplifiers 106, bandpass filters 104, bandpass filters 108, baseband filters 130, and/or otherwise adjust aspects of the operation of tuner 20 related to noise based on the noise parameters received by programmable interface 150.
Thus, particular embodiments of tuner 20 may amplify single-ended, voltage mode input signals 90 before converting these input signals to differential, current mode preprocessed signals 124, thereby providing better noise characteristics and consuming less current than if single-ended-to-differential and/or voltage-to-current conversion were done prior to amplification. Additionally, particular embodiments of tuner 20 provide multiple signals paths 100 from input ports 22 to quadrature mixer 120 that include different configurations of filtering and amplification, allowing both signals received across a wide sub-band and those receive across a narrow sub-band to be tuned by mixer 120 without substantial deterioration in performance. Furthermore, the distributed gain and attenuation elements throughout tuner 20 provide greater control over noise and distortion in particular embodiments of tuner 20. Also, the inclusion of a programmable interface may allow simplified interaction with and control of tuner 20. As a result, particular embodiments of tuner 20 may provide a number of operational benefits. Although a number of benefits are described, particular embodiments of tuner 20 may provide some, all, or none of these benefits.
Thus, particular embodiments of tuner 20 may be capable of tuning signals received in multiple different bands using a common quadrature mixer 120. Additionally, particular embodiments of tuner 20 may be able to generate quadrature, differential tuned signals 92 from single-ended input signals 90. As a result, tuner 20 may minimize the number of external components that may be required in system 10 to allow tuner 20 to operate with common configurations of antennas 50 and demodulator 30. Consequently, particular embodiments of tuner 20 may provide multiple benefits when utilized in system 10. Nonetheless, a particular embodiment of tuner 20 may include some, none, or all of these benefits.
Thus, as shown by
Although the present invention has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.
