KR20100027332A - Circuit of tuner for receiving digital broadcast - Google Patents

Abstract

PURPOSE: A tuner circuit for a digital broadcast is provided to amplify, filter and convert a frequency signal using only an analog/digital converter and a tracking filter. CONSTITUTION: A tuner circuit for a digital broadcast comprises the following: a tracking filter(200) including a differential converter(210) performing a differential conversion of a RF signal; a differential amplifier(220) differentially amplify the RF signal converted from the differential converter; a resonance circuit unit connected to a output end of the differential amplifier to output a RF signal with a predetermined frequency band from the converted RF signal; and an analog/digital converter connected to the tracking filter to convert the RF signal with the predetermined frequency band into a discrete signal.

Description

Circuit of tuner for receiving digital broadcast

The present invention relates to a tuner circuit for digital broadcast reception. More particularly, the present invention relates to a digital broadcast reception tuner circuit for receiving a digital broadcast signal of a desired frequency channel using a tracking filter and an analog / digital converter.

Generally, the band signal of digital broadcasting signal received from digital television is about 46-860MHz, and the performance of tuner used in digital television is not as high as that of tuner used in analog television. Even if all digital broadcasting of the air broadcasting is performed in the future, cable broadcasting that has a large number of viewers besides the broadcasting of the air broadcasting will continue to be transmitted as analog broadcasting, so the tuner used for the digital television has a high performance tuner. It is necessary to implement.

The tuner tunes to a specific frequency channel that the user wants to receive and receives a signal through the tuned specific frequency channel, wherein two channels adjacent to the tuned specific frequency channel are interposed by internal modulation distortion (Intermoduation Distortion). The product of is introduced into the channel to be received, which degrades the signal to noise ratio (SNR) for the channel to be received. In particular, since there are about 150 channels in the frequency band in which the broadcast signal is transmitted, there are a much larger number of adjacent channels than in the above case, so that more distortion signals enter the desired signal.

In addition, a plurality of harmonic components are present in the RF signal received by the tuner, and the plurality of harmonic components are down-converted to fall into a desired signal, resulting in poor SNR.

Therefore, a method has been developed to find only a signal of a desired band in a frequency band in which signals of a plurality of adjacent channels are mixed. First, there is a method of selecting a signal of a desired frequency band by using a tunable band pass filter. This method captures signals in a desired frequency band by moving the center frequency of a band pass filter having a narrow bandwidth.

However, in this case, the tunable band pass filter has to have a very narrow bandwidth and a very wide tuning range in order to select a desired signal. Therefore, a power consumption is very large because a discrete inductor is used to satisfy high channel selectivity.

Next, there is a method of selecting a signal of a desired frequency band by using a double up-down conversion method. This method up-converts an input RF signal having a frequency band of 48-860 MHz to have a 1.2 GHz frequency band by using an Up Conversion mixer and installs a SAW Filter (Surface Acoustic Wave Filter) in the 1.2 GHz band. After selecting only the desired signal, the RF signal filtered by the SAW filter is converted into an IF signal by using a down conversion mixer.

However, in the case of using the SAW filter and two mixers, a separate SAW filter is built in order to satisfy the high channel selectivity in the baseband even after conversion to the IF signal. .

The present invention to solve the above problems, by providing a tracking filter in front of the analog / digital converter to reduce the power consumption, to provide a digital broadcast reception tuner circuit that can reduce the dynamic range of the analog / digital converter The purpose.

A tuner circuit for digital broadcast reception according to the present invention for achieving the above object comprises: a tracking filter for amplifying an RF signal received from an antenna and outputting an RF signal having a predetermined frequency band among the amplified RF signals; And an analog / digital converter connected to the tracking filter to convert the RF signal having the predetermined frequency band into a discrete signal.

The tracking filter may include a differential converter configured to differentially convert the received RF signal, a differential amplifier configured to differentially amplify the differentially converted RF signal, and a differential amplified RF signal connected to an output terminal of the differential amplifier. It may include a resonant circuit unit for outputting an RF signal having a frequency band.

The differential amplifier may be a MOSFET or a BJT, and the resonant circuit may include a variable element part in which a capacitance component is changed according to a control signal, and a negative resistor part to improve frequency selectivity of the resonant circuit part.

In addition, the plurality of capacitors having a predetermined capacitance component may be connected in parallel, and a switch element may be connected to both ends of each capacitor.

The variable element unit may be a variable capacitor diode or a junction capacitor.

The control signal may be a signal generated according to a user channel.

The apparatus may further include a gain controller connected to an output terminal of the tracking filter to adjust a gain of an RF signal having a predetermined frequency band output from the resonance circuit unit.

In addition, the tracking filter may be divided into a low VHF (48 ~ 108MHz), High VHF (174 ~ 245MHz) or UHF (470 ~ 860MHz) band, the tracking filter and the analog / digital converter chip It may be configured in the form.

The analog / digital converter may be a sigma-delta type analog / digital converter.

According to the present invention, since the frequency signal received from the antenna is amplified and filtered using only the tracking filter and the analog / digital converter, and then converted into a discrete signal, it is possible to reduce the power consumption of the tuner circuit for digital broadcast reception.

In addition, since the adjacent channel signal of the frequency channel to be received is properly cut and transmitted by the tracking filter connected to the front end of the analog / digital converter, the dynamic range of the analog / digital converter can be reduced, making it easy to configure the tuner circuit for digital broadcast reception. Has the effect of being released.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, preferred embodiments of the present invention will be described below, but the technical idea of the present invention may be implemented by those skilled in the art without being limited or limited thereto.

1 is a block diagram of a tuner circuit for digital broadcast reception according to a preferred embodiment of the present invention.

As shown in FIG. 1, the tuner circuit 100 for receiving a digital broadcast according to an exemplary embodiment of the present invention uses a tracking filter 200 and an analog to digital converter (ADC) 300. Include.

The tracking filter 200 amplifies the RF signal received from the antenna A and outputs an RF signal having a predetermined frequency band among the amplified RF signals. In this case, a detailed configuration of the tracking filter 200 will be described below with reference to FIG. 2.

The analog / digital converter 300 is connected in series with the tracking filter 200 to convert the RF signal having the predetermined frequency band into a discrete signal, and the analog / digital converter is a sigma-delta type analog / digital method. It is preferable that it is a converter.

Conventional software defined radio (SDR) architecture has a structure in which an analog to digital converter (ADC) is combined with a wideband low noise amplifier (LNA). In this case, however, the dynamic range of the ADC is very high. It also connects a tunable band pass filter with band selection to the LNA on the front end, but in this case there is only a band select function, so the ADC in the band still has a high ADC. Dynamic range is required. In ADCs, the sampling rate and dynamic range (bits) are important indicators of performance.

The tuner circuit 100 for receiving a digital broadcast according to an exemplary embodiment of the present invention has a feature in that a tracking filter capable of appropriately cutting a signal of a desired channel from the received RF signal is connected to the front of the ADC. The tracking filter functions as a narrowband filter that cuts a large portion of the signals of the N + 1 or N-1 channel. The RF signal passing through the tracking filter has the N-channel signal as the main signal.

In the digital broadcast reception tuner circuit 100 according to an exemplary embodiment of the present invention, since the signals of the N-1 and N + 1 channels are substantially removed through the tracking filter 200, the analog / digital converter 300 Since the required dynamic range can be reduced to reduce the number of bits required, it is advantageous in terms of ease of implementation and power consumption.

The digital broadcast reception tuner circuit 100 according to the preferred embodiment of the present invention consumes less power because the analog / digital converter 300 is positioned behind the tracking filter 200 serving as the LNA. In the case of the tuner, linearity is lowered when a plurality of blocks are added. The digital tuner tuner circuit 100 according to the preferred embodiment of the present invention has relatively high linearity because the above-described simplified structure is provided.

FIG. 2 is a detailed block diagram of a tracking filter in the tuner circuit for digital broadcast reception shown in FIG. 1. As shown in FIG. 2, the tracking filter 200 includes a differential converter 210, a differential amplifier 220, and a resonant circuit 230, where RF _in is an input RF signal, RF _{in +,} and RF _{in −.} Denotes the differentially converted input RF signal, RF _{out +} and RF _{in −} represent the output RF signal.

The differential conversion unit 210 differentially converts the RF signal received from the antenna A into a single line so that the analog / digital converter 300 can convert the RF signal into a discrete signal.

The differential amplifier 220 differentially amplifies the differentially converted RF signal. The differential amplifier 220 includes a first differential amplifier 220a and a second differential amplifier 220b, and the differentially converted RF signal input to the first differential amplifier 220a is differentially amplified and secondly The differentially converted RF signal input to the output terminal of the differential amplifier 220b and input to the second differential amplifier 220b is differentially amplified and output to the output terminal of the first differential amplifier 220a.

2 illustrates a first differential amplification device 220a and a second differential amplification device 220b formed of a MOSFET, but this is only one embodiment, and the first differential amplification device 220a and the second differential amplification are BJT. It is also possible to construct the element 220b.

The resonant circuit 230 is connected to the output terminals of the first differential amplifying device 220a and the second differential amplifying device 220b and outputs an RF signal having a predetermined frequency band among the differentially amplified RF signals. In this case, the resonant circuit unit 230 is connected in parallel with the inductor unit 232 and the inductor unit 232, and in parallel with the variable element unit 234 and the variable element unit 234 in which capacitance components change according to a control signal. The resistor unit 236 is connected, and a negative resistor unit 238 connected in parallel with the resistor unit 236 to improve the frequency selectivity of the resonant circuit unit 230. In this case, the control signal may be a signal generated according to a user's channel selected by the tuner circuit 100 for digital broadcast reception.

The principle that the negative resistance unit 236 improves the frequency selectivity of the resonant circuit unit 230 is as follows. Since the resonant circuit composed of the resistor, the inductor, and the capacitor has the maximum impedance in the desired frequency band, the resonant circuit is suitable for frequency selection, and the frequency selectivity of the resonant circuit can be obtained as shown in Equation 1 below.

Equation 1

Where Q is the frequency selectivity, R _L is the impedance of the resonant circuit, w _o is the resonant frequency, and L is the reactance of the resonant circuit.

As shown in Equation 1, the frequency selectivity of the resonant circuit may be represented by a ratio of impedance and reactance in a desired frequency band, and the larger the value of R _L, the larger the Q value. However, in the case of a typical inductor, the parasitic resistance component is so large that the frequency selectivity is as low as 10-15.

At this time, when the negative resistance having a negative impedance component is connected in parallel, the frequency selectivity of the resonant circuit can be obtained as Equation 2 below.

Equation 2

Here, Q is frequency selectivity, R _L is the impedance of the resonant circuit, -R is the impedance of the negative resistor, w _o is the resonant frequency, and L is the reactance of the resonant circuit.

As shown in Equation 2, since the Q value becomes very large in an area where the absolute values of R _L and -R become similar, the inductor unit 232, the variable element unit 234, and the resistor unit 236 are connected in parallel to each other. The negative resistance unit 238 may be further connected in parallel to the circuit unit 230 to improve the frequency selectivity of the resonant circuit unit 230.

In addition, a gain control unit for gain control of a gain control of an RF signal having a predetermined frequency band may be connected to an output terminal of the tracking filter 200. In general, the RF signal input from the antenna A to the digital broadcast reception tuner 100 is mixed with a case where the input level is high and low, so that one analog / digital converter 300 satisfies the magnitude. it's difficult.

Therefore, the gain controller adjusts the gain of the RF signal having a predetermined frequency band to have a similar output level so that the analog / digital converter 300 separates the RF signal having the predetermined frequency band whose gain is controlled by the gain controller. Can be converted easily.

In addition, the tracking filter 200 may divide a frequency band that can be received into a low VHF (48 to 108 MHz), a high VHF (174 to 245 MHz), or a UHF (476 to 860 MHz) band.

3 is a detailed circuit diagram of a variable element unit in the tracking filter illustrated in FIG. 2. As shown in FIG. 3, in the variable element unit 224 according to the preferred embodiment of the present invention, a plurality of capacitors 224a having a predetermined capacitance component are connected in parallel, and a switch element is disposed across each capacitor 224a. 224b) are each connected. In this case, the switch element 224b may be a MOSFET or a BJT.

When the value of the capacitor constituting the tracking filter 200 in the tracking filter 200 is changed, it is possible to perform tracking while changing the frequency. Therefore, when the variable element unit 234 is composed of the plurality of capacitors 224a and the switch elements 224b, the switch according to the control signal which is a signal generated according to the user's channel transmitted to the digital broadcast reception tuner circuit 100 is switched. Since the capacitance of the variable element unit 234 can be adjusted by turning the element 224b on and off, tracking can be performed in a wide range while changing the frequency.

In this case, in FIG. 3, the plurality of capacitors 224a having a predetermined capacitance component are connected in parallel, and then the variable element unit 224 is configured to connect the switch elements 224b to both ends of each capacitor 224a. ), But this is only an example, and the variable element unit 224 of the tracking filter 220 according to the present invention is composed of a variable capacitor diode or a junction capacitor according to the control signal. It is also possible to perform tracking over a wide range while varying the frequency by adjusting the capacitance component.

4 is a detailed circuit diagram of a difference converter in the tracking filter illustrated in FIG. 2.

As shown in FIG. 4, the differential converter 210 includes an input unit 212, a bias unit 214, and a transformer unit 216, and the RF signal received from the antenna A as a single line is biased. The voltage is input through the input unit 212 by applying the voltage of 214, and is differentially converted into two signals through the transformer 216 and output.

5 is a reference diagram for a test result of a tuner circuit for digital broadcast reception according to an exemplary embodiment of the present invention. As shown in FIG. 5, the tuner circuit 100 for receiving digital broadcasts exhibits narrowband characteristics in 224MHZ, 605MHZ, and 883MHZ, which are frequency bands of the digital broadcast signal, and the SNR is evenly measured.

In general, an RF signal received from an antenna is converted into a discrete signal by a structure in which an analog to digital converter is attached to a low noise amplifier (LNA). However, in this case, the analog-to-digital converter needs to have a very high dynamic range, and even if a low noise amplifier has a tunable band pass filter, only a specific band can be selected. In order to convert to a discrete signal, the dynamic range of the analog-to-digital converter must be very high. Analog-to-digital converters are very difficult to design at high dynamic ranges.

The tuner circuit 100 for receiving a digital broadcast according to the present invention amplifies an RF signal received from an antenna A instead of a low noise amplifier in front of the analog / digital converter 300 and has an RF signal having a predetermined frequency band among the amplified RF signals. By connecting the tracking filter 200 for outputting the signal to the digital broadcast reception tuner circuit 100 to properly cut the signal adjacent to the channel to be received and then transmitted to the analog / digital converter 300 of the analog / digital converter 300 The range of the dynamic range can be reduced, making it easy to implement and reducing power consumption, and the digital broadcast receiving tuner circuit 100 of the present invention can be utilized as an element for a soft defined radio (SDR) in the form of a chip. Do.

The above description is merely illustrative of the technical idea of the present invention, and various modifications, changes, and substitutions may be made by those skilled in the art without departing from the essential characteristics of the present invention. It will be possible. Accordingly, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by the embodiments and the accompanying drawings. . The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

According to the present invention, since the tracking filter appropriately filters and transmits the frequency signal, it is possible to reduce the dynamic range of the analog / digital converter so that it is easy to implement and the power consumption can be reduced. It can be used as a substitute.

1 is a block diagram of a tuner circuit for digital broadcast reception according to an embodiment of the present invention;

2 is a detailed block diagram of a tracking filter in the tuner circuit for digital broadcast reception shown in FIG. 1;

3 is a detailed circuit diagram of a variable element unit in the tracking filter illustrated in FIG. 2;

4 is a detailed circuit diagram of a difference converter in the tracking filter shown in FIG. 2, and

5 is a reference diagram for a test result of a tuner circuit for digital broadcast reception according to an exemplary embodiment of the present invention.

<Brief description of the main parts of the drawings>

100: tuner circuit 200 for receiving digital broadcasts: tracking filter

(210): difference conversion unit 212: input unit

214: bias portion 216: converter portion

220: differential amplifier 220a: first differential amplifier

220b: second differential amplifier 230: resonant circuit section

232: inductor portion 234: variable element portion

234a: Capacitor 234b: Switch element

Reference numeral 236: resistance section 238: negative resistance section

240: gain control unit

(300): analog / digital converter

Claims (12)

A tracking filter for amplifying an RF signal received from an antenna and outputting an RF signal having a predetermined frequency band among the amplified RF signals; And And an analog / digital converter connected to the tracking filter to convert the RF signal having the predetermined frequency band into a discrete signal. The method of claim 1, The tracking filter may include a differential converter configured to differentially convert the received RF signal. A differential amplifier for differentially amplifying the differentially converted RF signal, and And a resonant circuit part connected to an output terminal of the differential amplifier part and outputting an RF signal having a predetermined frequency band among the differentially amplified RF signals. The method of claim 2, And the differential amplifier is a MOSFET or a BJT. The method of claim 2, And the resonant circuit part includes a variable element part in which a capacitance component is changed according to a control signal. The method of claim 2, And the resonant circuit part comprises a negative resistor part to improve frequency selectivity of the resonant circuit part. The method of claim 4, wherein The variable element unit is a tuner circuit, characterized in that a plurality of capacitors having a predetermined capacitance component is connected in parallel, the switch element is connected to each end of each capacitor. The method of claim 4, wherein The variable element unit is a tuner circuit, characterized in that the variable capacitor (Varactor diode) or junction capacitor (Junction capacitor). The method of claim 4, wherein And the control signal is a signal generated according to a user channel selection channel. The method of claim 2, And a gain control unit connected to an output terminal of the tracking filter to adjust a gain of an RF signal having a predetermined frequency band output from the resonant circuit unit. The method of claim 1, And the tracking filter and the analog / digital converter are configured in a chip form. The method of claim 1, The tracking filter is a tuner circuit, characterized in that the frequency band is divided into a low VHF (48-108MHz), High VHF (174-245MHz) or UHF (470-860MHz) band. The method of claim 1, The analog / digital converter is a sigma-delta type analog / digital converter, characterized in that the tuner circuit

Images