KR100586834B1 - Apparatus and Method for Frequency Direct Conversion of RF System - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to an apparatus and a method for directly converting a frequency of a wireless communication system.

2. The technical problem to be solved by the invention

According to the present invention, a signal converted from a frequency direct conversion apparatus of a wireless communication system is fed back to detect a DC level of each signal to detect an in-phase signal and a quadrature phase. The present invention provides a direct frequency conversion apparatus and method for a wireless communication system capable of lowering carrier feedthrough by equalizing a DC of a signal.

3. Summary of Solution to Invention

The present invention comprises: signal conversion means for converting a digitally input in-phase signal and quadrature signal into an analog signal; Filtering means for extracting a DC component by filtering the analog signal output from the signal conversion means; Detects the DC magnitude of the in-phase signal and the quadrature signal output from the filtering means, connects a path toward the higher DC, and if the DC level difference between the in-phase signal and the quadrature signal is less than or equal to a threshold, frequency for direct conversion Control means for connecting directly to the conversion means; Detecting the DC level difference between the in-phase signal and the quadrature signal output from the filtering means and sending the difference to the path connected by the control means, and when the DC level difference between the in-phase signal and the quadrature signal is less than or equal to a threshold, the control means Comparing means for informing by; DC supply means for applying a reverse bias to the input signal by the DC level difference detected by the comparison means; And the frequency direct converting means for directly frequency converting the in-phase signal and the quadrature signal whose DC level difference is converted to a threshold or less.

4. Important uses of the invention

The present invention is used in a wireless communication system and the like.

Wireless communication, direct conversion, direct conversion, dc offset, feedthrough, in-phase, quadrature

Description

Apparatus and method for frequency direct conversion of RF system of wireless communication system and method thereof             

1 is a block diagram of an embodiment of an apparatus for directly converting a frequency of a wireless communication system according to the present invention;

2 is a flowchart illustrating a method for directly converting a frequency in a wireless communication system according to the present invention.

* Explanation of symbols for the main parts of the drawings

101, 102: DAC 103, 104: DC Supply

105, 106: LPF (Low Pass Filter) 107: Controller

108: Comparator 109: Phase Splitter

110, 111: Mixer 112: Combiner

120: frequency direct conversion unit

The present invention relates to an apparatus for directly converting a frequency of a wireless communication system and a method thereof, and more particularly, to reduce carrier feedthrough occurring in the apparatus for directly converting a frequency of a wireless communication system. An apparatus and method for directly converting a frequency in a wireless communication system can be improved.

Conventional wireless communication systems such as terminals or base stations use a method of converting a frequency two or more times using a mixer and transmitting it to an antenna, but recently using a mixer of a single stage. In one step, the baseband signal is converted into a radio frequency (RF) signal and transmitted to the antenna. This configuration method is called direct conversion or zero intermediate frequency. The advantage of this method is that since the intermediate frequency stage is eliminated, the element related to the intermediate frequency is not used, thereby reducing the cost.

However, the disadvantage of direct conversion is that the RF frequency and the local oscillator (LO) frequency are the same, so the DC offset between the baseband I (In phase) signal and Q (Quadrature Phase) signal at the RF output. Carrier feedthrough occurs due to a DC offset, and a narrow band signal is added to an in band of the final signal, resulting in deterioration of the final transmission signal characteristics.

The present invention has been proposed in order to solve the above problems, and it is possible to detect the DC level of each signal by feeding back the converted signal in the frequency direct conversion apparatus of the wireless communication system. It is an object of the present invention to provide an apparatus and a method for directly converting a frequency in a wireless communication system that can reduce carrier feedthrough by making DC of an in-phase signal and a quadrature phase signal the same. .

An apparatus of the present invention for achieving the above object is a frequency direct conversion apparatus of a wireless communication system, comprising: signal conversion means for converting a digitally input in-phase signal and quadrature signal into an analog signal; Filtering means for extracting a DC component by filtering the analog signal output from the signal conversion means; Detects the DC magnitude of the in-phase signal and the quadrature signal output from the filtering means, connects a path toward the higher DC, and if the DC level difference between the in-phase signal and the quadrature signal is less than or equal to a threshold, frequency for direct conversion Control means for connecting directly to the conversion means; Detecting the DC level difference between the in-phase signal and the quadrature signal output from the filtering means and sending the difference to the path connected by the control means, and when the DC level difference between the in-phase signal and the quadrature signal is less than or equal to a threshold, the control means Comparing means for informing by; DC supply means for applying a reverse bias to the input signal by the DC level difference detected by the comparison means; And the frequency direct converting means for directly converting the in-phase signal and the quadrature signal in which the DC level difference is converted below a threshold.

Meanwhile, in the method of directly converting a frequency in a wireless communication system, the method of the present invention feeds back the in-phase signal I and the quadrature signal Q, which are analog signals output from a digital to analog converter (DAC). A first step of inputting into a loop; A second step of extracting a DC component through a low pass filter (LPF) from the in-phase signal (I) and the quadrature signal (Q) output in the first step; The DC component extracted from the low pass filter (LPF) is input to a controller and a comparator, and the in-phase signal I and the quadrature signal (I) passed through the low pass filter (LPF) in the controller ( Detecting the DC magnitude of Q) and connecting the switch up the DC; A fourth step of detecting, by the comparator, a DC level difference between the in-phase signal (I) and the quadrature signal (Q) passing through the low pass filter (LPF) and transmitting a signal along a path connected by the controller; A fifth step of applying a reverse bias to an input signal by a DC level difference detected by the comparator in a DC supply; Determining, by the comparator, whether the DC difference between the two signals is detected below a preset threshold; A seventh step of informing the controller if it is detected to be less than or equal to a threshold as a result of the sixth step, wherein the controller is connected to a frequency direct conversion unit to directly convert a frequency; And an eighth step of proceeding to the second step if it is not detected below the threshold as a result of the determination of the sixth step.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram of an apparatus for directly converting a frequency in a wireless communication system according to the present invention.

As shown in FIG. 1, the apparatus for directly converting a frequency of a wireless communication system according to the present invention includes a digital to analog converter (DAC) for converting digitally input in-phase signals and quadrature signals into analog signals. 101, 102, LPF (Low Pass Filter: hereinafter referred to as "LPF") to filter the analog signal output from the DAC (101, 102) to extract the DC component (105) 106), and detects the magnitude of the DC of the two signals output from the LPF (105, 106) and connects the switch (115) to the higher DC. When the DC level difference between the two signals is less than or equal to the threshold, direct conversion is performed. A controller 107 connecting the switches 113 and 114 to the frequency direct conversion unit 120 for detecting the DC level difference between the two signals output from the LPFs 105 and 106 and the controller 107. Sent by the path connected by the controller, and when the DC level difference between the two signals falls below a threshold, Comparator 108 for notifying the controller 107, DC Supply 103, 104 for applying a reverse bias to the input signal by the DC level difference detected by the comparator 108, and the The frequency direct conversion unit 120 directly converts two signals whose DC level difference is converted to a threshold or less.

In addition, the frequency direct converter 120 separates a local oscillator (LO) generating a predetermined frequency and a signal output from the local oscillator into an in-phase component and a quadrature phase component. A phase splitter 109, a mixer 110 and 111 for up-converting the signal output from the phase divider 109, and a synthesizer for synthesizing the signal output from the mixer 110 and 110 ( Combiner) 112.

The in-phase (I) and quadrature (Q) signals converted to analog by the DACs 101 and 102 are applied to the input terminals of the mixers 110 and 111, and the local oscillator signal is supplied to the phase divider 109. By separating the in-phase (I) component and the quadrature (Q) component, the in-phase component is applied to the local of the in-phase signal, and the quadrature component is applied to the local of the quadrature signal. The two signals upconverted by the mixers 110 and 111 are combined by the combiner 112 to form a single signal. At this time, if a DC offset (Offset) in the quadrature signal, the following equation (1) is established.

"가 캐리어(Carrier)가 되며, 이것이 출력특성 저하를 야기하게 된다. 따라서, 상기 신호를 제거 또는 대폭적인 감쇠를 수행해야 된다.In RF of Equation 1 above,

Becomes a carrier, which causes a decrease in output characteristics. Therefore, the signal must be removed or a significant attenuation must be performed.

An operation process of the apparatus for directly converting a frequency of a wireless communication system according to the present invention is as follows.

First, the in-phase signal I and the quadrature signal Q, which are analog signals output from the DACs 101 and 102, are applied. The in-phase signal I and the quadrature signal Q are input to a feedback loop, and a DC component is extracted while passing through low pass filters 105 and 106. In this case, the switches 113 and 114 are connected to a feedback loop port.

The DC components extracted from the low pass filters (LPFs) 105 and 106 are input to the controller 107 and the comparator 108, and the low pass filter (LPF) 105, from the controller 107. The DC magnitude of the two signals passing through 106 is detected and the switch 115 is connected to the higher DC.

The comparator 108 detects a DC level difference between two signals passing through the low pass filters (LPFs) 105 and 106 and sends it along a path connected by the controller 107.

The DC supplies 103 and 104 apply a reverse bias to the input signal by the DC level difference detected by the comparator 108.

Meanwhile, the process is repeated until the comparator 108 detects a DC difference between the two signals below a preset threshold. When the DC level difference between the two signals in the comparator 108 is less than or equal to the threshold, the controller 107 is notified, and the controller 107 switches the switches 113 and 114 in front of the mixers 110 and 111 to the mixer 110. , 111) for direct conversion.

2 is a flowchart illustrating a method for directly converting a frequency in a wireless communication system according to the present invention.

As shown in FIG. 2, in the method for directly converting a frequency in a wireless communication system according to the present invention, first, an in-phase signal I and an quadrature-phase signal Q, which are analog signals output from the DACs 101 and 102, are fed back. A feedback is inputted to a loop (201), and a DC component is extracted while passing through a low pass filter (LPF) 105 and 106 (202).

Next, DC components extracted from the low pass filters (LPFs) 105 and 106 are input to the controller 107 and the comparator 108 (203), and the controller 107 receives the LPF (Low). The DC signal of the two signals passing through the pass filter 105 and 106 is detected and the switch 115 is connected to the higher DC signal (204).

The comparator 108 detects the DC level difference between the two signals passed through the low pass filters (LPFs) 105 and 106 and sends it along the path connected by the controller 107 (205).

The DC supplies 103 and 104 apply a reverse bias to the input signal by the DC level difference detected by the comparator 108 (206).

On the other hand, the comparator 108 determines whether the DC difference between the two signals is detected below a preset threshold (207), and if the determination result is below the threshold, notifies the controller 107 and the controller 107 ) Connects the switches 113 and 114 in front of the mixers 110 and 111 to the mixers 110 and 111 (208) for direct conversion (209).

As a result of the determination, if it is not detected below the threshold, the process proceeds to step 202 of extracting the DC component via the LPF.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

As described above, the present invention reduces or eliminates a continuous DC offset in real time by using a feedback loop of a direct conversion apparatus of a wireless communication system, and reduces or eliminates a DC offset, thereby reducing a carrier feed. There is an effect that can improve the characteristics (Carrier Feedthrough).

Claims (4)

In the frequency direct conversion device of a wireless communication system, Signal conversion means for converting a digitally input in-phase signal and quadrature signal into an analog signal; Filtering means for extracting a DC component by filtering the analog signal output from the signal conversion means; Detects the DC magnitude of the in-phase signal and the quadrature signal output from the filtering means, connects a path toward the higher DC, and if the DC level difference between the in-phase signal and the quadrature signal is less than or equal to a threshold, frequency for direct conversion Control means for connecting directly to the conversion means; Detecting the DC level difference between the in-phase signal and the quadrature signal output from the filtering means and sending the difference to the path connected by the control means, and when the DC level difference between the in-phase signal and the quadrature signal is less than or equal to a threshold, the control means Comparing means for informing by; DC supply means for applying a reverse bias to the input signal by the DC level difference detected by the comparison means; And The frequency direct converting means for directly frequency converting the in-phase signal and the quadrature signal whose DC level difference is converted to a threshold or less; Direct frequency conversion device of the wireless communication system comprising a. The method of claim 1, Connection of the control means, An apparatus for directly converting frequencies in a wireless communication system, using first to third switches. The method according to claim 1 or 2, The frequency direct conversion means, Local oscillation means for generating a predetermined frequency; Phase distribution means for separating the signal output from the local oscillation means into an in-phase component and a quadrature phase component; Mixing means for up-converting an in-phase signal and a quadrature phase signal respectively output from the phase distribution means; And Synthesizing means for synthesizing the respective signals output from the mixing means; Direct frequency conversion device of the wireless communication system comprising a. In the frequency direct conversion method of a wireless communication system, A first step of inputting an in-phase signal (I) and a quadrature signal (Q), which are analog signals output from a digital to analog converter (DAC), to a feedback loop; A second step of extracting a DC component through a low pass filter (LPF) from the in-phase signal (I) and the quadrature signal (Q) output in the first step; The DC component extracted from the low pass filter (LPF) is input to a controller and a comparator, and the in-phase signal I and the quadrature signal (I) passed through the low pass filter (LPF) in the controller ( Detecting the DC magnitude of Q) and connecting the switch up the DC; A fourth step of detecting, by the comparator, a DC level difference between the in-phase signal (I) and the quadrature signal (Q) passing through the low pass filter (LPF) and transmitting a signal along a path connected by the controller; A fifth step of applying a reverse bias to an input signal by a DC level difference detected by the comparator in a DC supply; Determining, by the comparator, whether the DC difference between the two signals is detected below a preset threshold; A seventh step of informing the controller if it is detected to be less than or equal to a threshold as a result of the sixth step, wherein the controller is connected to a frequency direct converter to directly convert a frequency; And An eighth step of proceeding to the second step if the detection result of the sixth step is not detected below the threshold; Direct frequency conversion method of a wireless communication system comprising a.

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