Abstract:
The present invention disclosed an apparatus and method for receiving a plurality of broadcasting signals. The apparatus comprises: a control circuit for generating an analog control voltage signal according to a frequency-voltage look-up table and a desired frequency; an antenna module comprising an antenna and an antenna resonant control circuit comprising a voltage-controlled capacitor being controlled by the analog control voltage signal, wherein the antenna resonant control circuit comprises a voltage-controlled capacitor to control the bandwidth received by the antenna according to the analog control voltage signal; a tuner for tuning a broadcasting signal received by the antenna to generate an output signal; and a demodulator for demodulating the output signal of the tuner.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    (a) Field of the Invention 
         [0002]    The invention relates to a broadcasting system, particularly to a control circuit and related control method for controlling frequency resonance point of an antenna. 
         [0003]    (b) Description of the Related Art 
         [0004]    An FM/DAB (digital audio broadcasting)/SVB (digital video broadcasting) antenna need a broad receiving bandwidth. For example, the bandwidth of FM is about 88 MHz-108 MHz, the bandwidth of DVB-T (European digital video broadcasting-Terrestrial) is about 177.5 MHz-226.5 MHz/474 MHz-858 MHz, and the bandwidth of DAB is about 1452 MHz-1491 MHz. Other antennas, such as WiMAX (Worldwide Interoperability for Microwave Access) and WLAN (Wireless Local Area Network) also have different receiving bandwidth. 
         [0005]    Generally speaking, a prior single antenna cannot support such a broad receiving bandwidth to include many kinds of broadcasting signals at the same time. If a plurality of antennas and a plurality of tuning units are used to receive different broadcasting signals separately to support a broad bandwidth, the total volume as well as the hardware cost is increased. 
         [0006]    If an integrated antenna can receive a plurality of different broadcasting signals, such as an antenna integrating in-car broadcasting reception and wireless communication network, the production cost of the integrated antenna can be obviously reduced. However, such an integrated antenna may receive unnecessary signals due to its broad bandwidth to thereby result in difficulty in post-processing. Besides, how to control such an integrated antenna to receive a desired signal and achieve better reception quality is an important task to endeavor. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    In light of the above-mentioned problem, one object of the invention is to provide a control circuit for controlling frequency resonance point of an antenna and the related method to reduce the above problem in the prior art. 
         [0008]    One object of the invention is to provide a control circuit for controlling frequency resonance point of an antenna and the related method to receive and process a plurality of different kinds of broadcasting signals. 
         [0009]    One object of the invention is to provide a control circuit for controlling frequency resonance point of an antenna and the related method by an additional optimization procedure to achieve the purposes of simplifying circuitry, lowering cost, a better control effect by using the acquired information. 
         [0010]    One embodiment of the invention provides a broadcasting signal receiving circuit, comprising: a control circuit, an antenna module, a tuner and a demodulator. The control circuit generates a voltage control signal according to a frequency-voltage look-up table and a desired frequency. The antenna module includes an antenna and an antenna resonant control circuit. The frequency range of the antenna covers at least two broadcasting frequency bands. The antenna resonant control circuit includes a voltage-controlled capacitor and adjusts the receiving bandwidth of the antenna according to the voltage control signal. The tuner is coupled to the antenna resonant control circuit and tunes a broadcasting signal received by the antenna to generate an output signal. The demodulator is coupled to the tuner and demodulates the output signal of the tuner. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a block diagram illustrating a broadcasting signal receiving circuit  100  according to a first embodiment of the invention. 
           [0012]      FIG. 2  shows a block diagram illustrating the integration of a broadcasting signal receiving circuit  200  and a host according to the first embodiment of the invention. 
           [0013]      FIG. 3  shows a control flow chart illustrating the integration of the broadcasting signal receiving circuit  200  and the host. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Some preferred embodiments of the present invention will now be described in greater detail in the following. However, it should be recognized that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, that is, this invention can also be applied extensively to other embodiments, and the scope of the present invention is expressly not limited except as specified in the accompanying claims. 
         [0015]      FIG. 1  shows a block diagram illustrating a broadcasting signal receiving circuit  100  according to an embodiment of the invention. The broadcasting signal receiving circuit  100  includes an antenna  102 , an antenna resonant control circuit  104 , a tuner  106 , a demodulator  108  and a control circuit  110 . The broadcasting signal receiving circuit  100  may receive and process a plurality of broadcasting signals with different kinds of bandwidths, for example, at least two kinds of signals selected from the following standard: AM, FM, DVB, GSM, GPS, DCS, WiMAX and WLAN. The controllable frequency range should cover the bandwidths of any two of the above number of broadcasting signals to be received by the broadcasting signal receiving circuit  100 . The control circuit  110  recognizes which broadcasting signal to be received according to a command from an upper layer to generate a control signal and then transmit to the antenna resonant control circuit  104  for controlling the received broadcasting signals. According to an embodiment, the antenna resonant control circuit  104  includes at least an LC tank and/or at least a voltage-controlled-capacitor. The voltage-controlled capacitor provides a corresponding capacitance according to the voltage value of the voltage control signal. The bandwidth of the broadcasting signal receivable by the antenna may be changed by adjusting the antenna resonant control circuit  104 . Thus, the broadcasting signal within the bandwidth may be received and the unnecessary broadcasting signal may be rejected. In one embodiment, the antenna  102  and the antenna resonant control circuit  104  may be integrated into a circuit: “an antenna resonant control module”. The antenna resonant control module adjusts the frequency resonance point of the antenna according to the voltage control signal. In the control circuit  110 , a digital-to-analog converter (DAC) may be included to transform a digital control signal into the voltage control signal. Please note that, the voltage control signal is an analog signal described above. Those who are skilled in the art may directly replace the voltage control signal by a digital control signal to control the antenna resonant control circuit  104 . 
         [0016]    The tuner  106  may adjust settings of itself to perform gain recursion control according to control signals of the control circuit  110 . The tuner  106  may be used to perform frequency conversion, filtering and/or amplification. Since the functions of the tuner  106  are well known to those who are skilled in the art, the operating principle and functions of the tuner  106  is described hereinafter. In another embodiment, the tuner  106  may include a plurality of tuning units to separately process the broadcasting signals with different standards received by the antenna  102 . In another embodiment, the control circuit  110  may output a variable gain amplifier control signal VGA to control the gain of the tuner  106 . 
         [0017]    The demodulator  108  may receive the output signal from the tuner  106  and demodulate the output signal. Since the functions of the demodulator  108  are well known to those who are skilled in the art, the operating principle and functions of the demodulator  108  is not be described hereinafter. The demodulator  108  transmits the demodulated signal to back-end circuits for subsequent processing, for example, application playing software and/or hardware. In another embodiment, the demodulator  108  may include a plurality of demodulation units to separately process the broadcasting signals with different standards outputted by the tuner  106 . For example, if the demodulator  108  includes a DVB-T demodulation unit and a DAB demodulation unit, the broadcasting signal receiving circuit  100  may demodulate the DVB-T broadcasting signal and the DAB broadcasting signal. 
         [0018]    The control circuit  110  may receive an external command (for example a command for receiving a DVB-T signal in a specific channel from a CPU or MCU) to determine the broadcasting signal received and processed by the broadcasting signal receiving circuit  100 . The control circuit  110  may use the voltage control signal to adjust the antenna resonant control circuit  104  to reach functions of adjusting the frequency resonance point of the antenna. In another embodiment, assuming that the environment is under additive white Gaussian noise (AWGN) condition, a look-up table of the relation between the antenna resonance point and an initial voltage (of the analog voltage control signal) is built up in advance. Then, the control circuit  110  may perform related operations according to the look-up table to accelerate the above recursion control operation; certainly, it can also be omitted. 
         [0019]    In another embodiment, the control circuit  110  may be set in the demodulator  108  within the same chip (for example, a DTV demodulator control chip), as shown in  FIG. 2 .  FIG. 2  shows a block diagram illustrating the integration of a broadcasting signal receiving circuit  200  and a host according to the first embodiment of the invention. If the broadcasting signal receiving circuit  200  couples the host  210 , the above mentioned look-up table may be set in a related driver. Thus, a user may command the playing software of the host to perform frequency change (for example, tuning to a different channel) and then the playing software transmits a frequency change command to the related driver such as a BDA driver (a BDA driver for a digital TV receiving chip applied in Microsoft Windows series where the related driver may not an essential of the invention and the details of the related driver are well-known to those who are skilled in the art and thus omitted hereinafter). According the built-in look-up table, the relation between the frequency and voltage is found so as to output the initial voltage. The initial voltage may supply to the antenna resonant control circuit  204  and the demodulator  208  performs recursion control according to an estimated signal-to-noise ratio. By the recursion control, a better control mechanism is achieved. Certainly, the control circuit  110  may be replaced by the computer CPU and related programs. 
         [0020]      FIG. 3  shows a control flow chart illustrating the integration of the broadcasting signal receiving circuit  200  and the host, comprising the following step: 
         [0021]    Step  310 : commanding the application software of the computer (playing software) by a user to perform frequency change (for example, tuning to a different channel); 
         [0022]    Step  320 : receiving the frequency change command by the software; 
         [0023]    Step  330 : sending the frequency change command to the related driver, such as a BDA driver; 
         [0024]    Step  340 : outputting a voltage control signal to the antenna resonant control circuit  104  according to a frequency-voltage look-up table and a desired frequency; 
         [0025]    Step  350 : receiving the related control command by the demodulator  208 ; and 
         [0026]    Step  360 : controlling the operations of the demodulator  208  and the tuner  206  by the control command, such as tuning to a different channel or the like and simultaneously performing recursion control by the demodulator  208  according to the estimated signal-to-noise ratio. If the above recursion control is performed, a better control mechanism can be achieved. 
         [0027]    The invention provides a set of voltages to be used in antenna resonance point control to receive a plurality of different broadcasting signals to not only simplify circuitry and reduce cost but also achieve the optimum control mechanism by using the acquired information. 
         [0028]    In one embodiment of the invention, for an application software (AP) using the FM/DAB/DTV system, after a user transmits a channel change command to a driver, the driver outputs a preset voltage according to the originally built-in frequency-voltage corresponding table. But, the preset voltage is built by assuming under normal environment. Thus, the information acquired by the demodulator  208 , such as signal-to-noise ratio (SNR), is used to change the output voltage to result in recursion control so as to achieve the purpose of better control. 
         [0029]    Certainly, the whole circuit can further comprise a low signal-to-noise ratio amplifier, disposed between the tuner  206  and the antenna resonant control circuit  204  to amplify the signal received by the antenna. 
         [0030]    Although the present invention has been fully described by the above embodiments, the embodiments should not constitute the limitation of the scope of the invention. Various modifications or changes can be made by those who are skilled in the art without deviating from the spirit of the invention.