Calibration circuit for inter-channel phase and gain calibration in a multi-channel beamforming system, multi-channel beamforming system comprising the circuit and channel calibration method using the circuit

Abstract

The calibration circuit includes a selection unit, a power detector, an analog-to-digital converter, and a calibrator. The selection unit is connected to a plurality of channels, selects two channels from the plurality of channels, provides a test signal to the selected two channels, and receives a test result signal from the selected two channels. The power detector detects power of the selected two channels according to the test result signal. The analog-to-digital converter performs analog-to-digital conversion on an output of the power detector. The calibrator calibrates a phase and a gain between the plurality of channels based on an output of the analog-to-digital converter. One of the plurality of channels is set as a reference channel, the phase and the gain of the remaining channels other than the reference channel among the plurality of channels are sequentially optimized based on the reference channel, and the phase and the gain of the reference channel are optimized based on one of the remaining channels.

Description

BACKGROUND I. TECHNICAL FIELD

[0002] Example embodiments relate generally to signal processing technology, and more particularly to a calibration circuit for calibrating phases and gains between channels in a multi-channel beamforming system, a multi-channel beamforming system including the same, and a channel calibration method using the same.

[0003] II. DESCRIPTION OF RELATED ART

[0004] A fifth generation (5G) mobile communication system currently under study requires about several tens to several hundreds of times the network capacity compared to Long Term Evolution (LTE) as the fourth generation (4G). In addition, communication technology based on millimeter wave communication is being studied to secure a wide bandwidth. In the millimeter wave band, the transmission / reception signal is weaker than the frequency band of the conventional 4G mobile communication system, and thus a technique such as beamforming can be used to overcome this problem.

[0005] A phased array antenna is a technique that increases beam directivity and gain by arranging antennas in an array form and combining beams received through the antennas. Since a signal can be transmitted only in a desired direction through beamforming, a large gain can be obtained. The 5G mobile communication system requires a higher data transmission rate, and the phased array antenna can be a key technology for calibrating large loss on a path.

[0006] The 5G mobile communication system of the millimeter wave band can use a higher frequency, and thus has the advantage of reducing the size of an antenna and a module due to a short wavelength. However, such a short wavelength has a problem of easily occurring phase and amplitude errors.

[0007] If a signal from each antenna (or channel) occurs a phase and amplitude error, the direction of the combined beam can be changed, the side lobe level can be increased, and the transmission speed can be reduced. Therefore, a method of accurately measuring a signal from each channel and calibrating the signal using appropriate phase / gain is required. SUMMARY

[0008] Some example embodiments provide a calibration circuit in a multi-channel beamforming system that can effectively calibrate phases and gains between channels using a sequential channel signal comparison scheme.

[0009] Some example embodiments provide a multi-channel beamforming system including a calibration circuit and capable of effectively calibrating phases and gains between channels using a sequential channel signal comparison scheme.

[0010] Some example embodiments provide a channel calibration method using a calibration circuit in a multi-channel beamforming system and capable of effectively calibrating phases and gains between channels using a sequential channel signal comparison scheme.

[0011] According to an example embodiment, a calibration circuit is included in a multi-channel beamforming system including a plurality of channels, the calibration circuit calibrating phases and gains among the plurality of channels. The calibration circuit includes a selection unit, a power detector, an analog-to-digital converter, and a calibrator. The selection unit is connected to the plurality of channels, selects two channels from the plurality of channels, provides a test signal to the selected two channels, and receives a test result signal from the selected two channels. The power detector detects powers of the selected two channels according to the test result signal. The analog-to-digital converter analog-to-digital converts an output of the power detector. The calibrator calibrates phases and gains among the plurality of channels based on an output of the analog-to-digital converter. One of the plurality of channels is set as a reference channel, phases and gains of remaining channels except for the reference channel among the plurality of channels are sequentially optimized based on the reference channel, and phases and gains of the reference channel are optimized based on one of the remaining channels.

[0012] In some example embodiments, the plurality of channels can include a first channel to an Nth channel, where N is a natural number greater than or equal to three. The first channel can be selected as a reference channel, the second channel to the Nth channel can be sequentially selected as a comparison channel, and the second channel to the Nth channel can be sequentially set to have the lowest power at a first phase. From among the second channel to the Nth channel, the second channel can be selected as a reference channel, the third channel can be selected as a comparison channel, and the third channel can be set to have the lowest power at a second phase different from the first phase. The third channel can be selected as a reference channel, the first channel can be selected as a comparison channel, and the first channel can be set to have the lowest power at the first phase.

[0013] In some example embodiments, while the second channel is set to have the lowest power at the first phase, the phase and gain of the first channel are set to the second phase and a first gain and the phase and gain of the second channel are set to a third phase and the first gain, a reference output power can be measured based on test result signals obtained from the first and second channels. After adjusting the phase and gain of the second channel while maintaining the phase and gain of the first channel, a comparison output power can be measured according to test result signals obtained from the first channel and the second channel. Based on a result of comparing the reference output power and the comparison output power, the phase and gain of the second channel can be set to have a minimum phase error and a minimum gain error.

[0014] In some example embodiments, when the third channel is set to have the lowest power at the second phase, the phase and the gain of the first channel are set to the first phase and the first gain, and the phase and the gain of the third channel are set to the third phase and the first gain, the reference output power can be measured based on the test result signals obtained from the second and third channels. After adjusting the phase and the gain of the third channel while keeping the phase and the gain of the second channel, the comparison output power can be measured according to the test result signals obtained from the second and third channels. Based on the result of comparing the reference output power and the comparison output power, the phase and the gain of the third channel can be set to have the minimum phase error and the minimum gain error.

[0015] In some example embodiments, the plurality of channels can include first to Nth channels, where N is a natural number greater than or equal to three. The first channel can be selected as a reference channel, and the (N / 2+1)th to Nth channels can be sequentially selected as comparison channels, which can be sequentially set to have the lowest power at the first phase. The (N / 2+1)th channel can be selected as a reference channel, and the first to N / 2th channels can be sequentially selected as comparison channels, which can be sequentially set to have the lowest power at the first phase.

[0016] In some example embodiments, the plurality of channels can include first to Nth channels, where N is a natural number greater than or equal to three. The first channel can be selected as a reference channel, and the (N / 2+1)th to Nth channels can be sequentially selected as comparison channels, which can be sequentially set to have the lowest power at the first phase. The (N / 2+1)th channel can be selected as a reference channel, and the first to N / 2th channels can be sequentially selected as comparison channels, which can be sequentially set to have the lowest power at a second phase different from the first phase.

[0017] In some example embodiments, each of the plurality of channels can include a transmission path and a reception path. The transmission path can be enabled in a transmission mode to output a transmission signal. The reception path can be enabled in a reception mode to receive a reception signal.

[0018] In some example embodiments, the selection unit can include a plurality of power couplers, a plurality of first channel selection structures, at least one second channel selection structure, and a transceiver channel selector. The plurality of power couplers can be connected to the plurality of channels. The plurality of first channel selection structures can be connected to the plurality of power couplers. The second channel selection structure can be connected to the plurality of first channel selection structures. The transceiver channel selector can be connected to the second channel selection structure.

[0019] In some example embodiments, in the transmission mode, the test signal can be a transmission signal, the transceiving channel selector can provide the transmission signal to the selected two channels, and the transceiving channel selector can receive the test result signal from the selected two channels through the power coupler, the first channel selection structure, and the second channel selection structure.

[0020] In some example embodiments, in the reception mode, the test signal can be a reception signal, the transceiving channel selector can provide the reception signal to the selected two channels through the second channel selection structure, the first channel selection structure, and the power coupler, and the transceiving channel selector can receive the test result signal from the selected two channels.

[0021] In some example embodiments, the selection unit can include a plurality of quarter- wavelength transformers, a plurality of switches, a plurality of half-wavelength transformers, a combiner / splitter, and a transceiving channel selector. The plurality of quarter- wavelength transformers can be connected to the plurality of channels. The plurality of switches can be connected to the plurality of quarter-wavelength transformers. The plurality of half-wavelength transformers can be connected to the plurality of quarter-wavelength transformers. The combiner / splitter can be connected to the plurality of half-wavelength transformers. The transceiving channel selector can be connected to the combiner / splitter.

[0022] In some example embodiments, each of the plurality of channels can include only a transmission path enabled to output a transmission signal in the transmission mode.

[0023] In some example embodiments, the selection unit can include a plurality of power couplers, a plurality of first channel selectors, at least one second channel selector, and a combiner / splitter. The plurality of power couplers can be connected to the plurality of channels. The plurality of first channel selectors can be connected to the plurality of power couplers. The second channel selector can be connected to the plurality of first channel selectors. The combiner / splitter can be connected to the second channel selector.

[0024] According to an example embodiment, a multi-channel beamforming system includes a plurality of channels and a calibration circuit connected to the plurality of channels. The calibration circuit calibrates phases and gains among the plurality of channels. The calibration circuit includes a selection unit, a power detector, an analog-to-digital converter, and a calibrator. The selection unit is connected to the plurality of channels, selects two channels from the plurality of channels, provides a test signal to the selected two channels, and receives a test result signal from the selected two channels. The power detector detects powers of the selected two channels according to the test result signal. The analog-to-digital converter analog-to-digital converts an output of the power detector. The calibrator calibrates the phases and the gains among the plurality of channels based on an output of the analog-to-digital converter. One of the plurality of channels is set as a reference channel, phases and gains of remaining channels except for the reference channel among the plurality of channels are sequentially optimized based on the reference channel, and the phases and the gains of the reference channel are optimized based on one of the remaining channels.

[0025] According to an example embodiment, in a channel calibration method for calibrating phases and gains among a plurality of channels included in a multi-channel beamforming system, the plurality of channels include a first channel to an Nth channel, where N is a natural number greater than or equal to three. The first channel is selected as a reference channel. A second channel to the Nth channel are sequentially selected as comparison channels. The second channel to the Nth channel are sequentially set to have a lowest power at a first phase. The second channel is selected as the reference channel. The third channel is selected as the comparison channel. The third channel is set to have the lowest power at a second phase different from the first phase. The third channel is selected as the reference channel. The first channel is selected as the comparison channel. The first channel is set to have the lowest power at the first phase.

[0026] In some example embodiments, while the second channel to the Nth channel are sequentially set to have the lowest power at the first phase, the phase and gain of the first channel can be set to a second phase and a first gain. The phase and gain of the second channel can be set to a third phase and the first gain. The reference output power can be measured based on test result signals obtained from the first and second channels. The phase and gain of the second channel can be adjusted while the phase and gain of the first channel are maintained. The comparison output power can be measured based on test result signals obtained from the first and second channels. Based on a result of comparing the reference output power and the comparison output power, the phase and gain of the second channel can be set to have a minimum phase error and a minimum gain error.

[0027] In some example embodiments, while the third channel is set to have the lowest power at the second phase, the phase and gain of the second channel can be set to the first phase and the first gain. The phase and gain of the third channel can be set to a third phase and the first gain. The reference output power can be measured based on test result signals obtained from the second and third channels. The phase and gain of the third channel can be adjusted while the phase and gain of the second channel are maintained. The comparison output power can be measured based on test result signals obtained from the second and third channels. Based on a result of comparing the reference output power and the comparison output power, the phase and gain of the third channel can be set to have a minimum phase error and a minimum gain error.

[0028] According to an example embodiment, in a channel calibration method for calibrating phases and gains among a plurality of channels included in a multi-channel beamforming system, the plurality of channels includes a first channel to an Nth channel, where N is a natural number greater than or equal to three. The first channel is selected as a reference channel. The (N / 2+1)th channel to the Nth channel are sequentially selected as comparison channels. The (N / 2+1)th channel to the Nth channel are sequentially set to have the lowest power at a first phase. The (N / 2+1)th channel is selected as a reference channel. The first channel to the N / 2th channel are sequentially selected as comparison channels. The first channel to the N / 2th channel are sequentially set to have the lowest power at a first phase or a second phase different from the first phase.

[0029] In the calibration circuit, the multi-channel beamforming system, and the channel calibration method according to the example embodiment, the phases and gains of the plurality of channels can be calibrated based on a multi-channel signal comparison scheme, and an envelope detector can be used to compare feedback signals instead of using a local oscillator (LO) and an in-phase / quadrature-phase (I / Q) mixer. By fixing the phase and gain of one channel, adjusting the phase and gain of another channel, and measuring the envelope of the signal after the two channels are added, the difference in the phase and gain between the two channels can be detected, and the channel can be calibrated by using or feeding back the difference. Therefore, it can be less sensitive to frequency and can have no LO problem and direct current (DC) offset problem because no I / Q mixer is used. In addition, both the transmission and reception paths can be easily calibrated by simply changing the direction of the switch.

[0030] BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a block diagram illustrating a calibration circuit and a multi-channel beamforming system including the calibration circuit according to an example embodiment.

[0032] Figure 2 is a block diagram illustrating an example of a channel included in a multi-channel beamforming system according to an example embodiment.

[0033] Figure 3 is a flowchart illustrating a channel calibration method according to an example embodiment.

[0034] Figure 4 is a flowchart illustrating an example of step S150 of Figure 3 .

[0035] Figure 5 is a diagram for explaining the operation of Figure 4 .

[0036] Figure 6 is a flowchart illustrating an example of step S250 of Figure 3 .

[0037] Figure 7A , 7B , 7C and 7D are diagrams for describing operations of Figure 3 .

[0038] Figure 8A and 8B are diagrams for describing operations of Figure 1 calibration circuit and a multi-channel beamforming system.

[0039] Figure 9 is a block diagram illustrating a calibration circuit and a multi-channel beamforming system including the calibration circuit according to an example embodiment.

[0040] Figure 10 is a flowchart illustrating a channel calibration method according to an example embodiment.

[0041] Figure 11A , 11B , 11C and 11D are diagrams for describing operations of Figure 10 .

[0042] Figure 12 is a flowchart illustrating a channel calibration method according to an example embodiment.

[0043] Figure 13A and 13B are diagrams for describing operations of Figure 12 .

[0044] Figure 14 is a block diagram illustrating a calibration circuit and a multi-channel beamforming system including the calibration circuit according to an example embodiment.

[0045] Figure 15 , 16A and 16B are diagrams for describing a multi-channel beamforming system including a calibration circuit according to an example embodiment.

[0046] Figure 17 is a block diagram illustrating a multi-channel beamforming system according to an example embodiment. DETAILED DESCRIPTION

[0047] Various example embodiments will be described more fully with reference to the accompanying drawings in which example embodiments are shown. The present inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0048] Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present inventive concept to those skilled in the art. Like reference numerals refer to like elements throughout the application.

[0049] It will be understood that, although the terms first, second, etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the inventive concept. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0050] It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements can be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0051] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive concept. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and / or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0052] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an overly literal or overly formal sense unless expressly so defined herein.

[0053] The above and other features of the inventive concept will become more apparent by describing in detail example embodiments thereof with reference to the attached drawings in which:

[0054] Figure 1 is a block diagram illustrating a calibration circuit and a multi-channel beamforming system including the calibration circuit according to an example embodiment.

[0055] Reference Figure 1The multi-channel beamforming system 100 includes a plurality of channels 1100-1, 1100-2, 1100-3, 1100-4, 1100-5, 1100-6, 1100-7, and 1100-8, and a calibration circuit. The multi-channel beamforming system 100 can further include a plurality of combiners / splitters 1200-1, 1200-2, 1200-3, 1200-4, 1300-1, 1300-2, and 1300-3, and a signal processor 1400.

[0056] The plurality of channels 1100-1 to 1100-8 outputs a transmission signal to be transmitted to the outside (e.g., an external device and / or system) in a transmission mode, and receives a reception signal from the outside in a reception mode. The plurality of channels 1100-1 to 1100-8 includes a first channel to an Nth channel, where N is a natural number greater than or equal to three. For example, N can be an integer that is a multiple of 2. Figure 1 An N=8 case is represented. However, example embodiments are not limited thereto, and the number of channels can be determined in different ways according to example embodiments.

[0057] The plurality of channels 1100-1 to 1100-8 can include a plurality of transmission paths TX_P1, TX_P2, TX_P3, TX_P4, TX_P5, TX_P6, TX_P7, and TX_P8, which are enabled or activated to output a transmission signal in a transmission mode, and a plurality of reception paths RX_P1, RX_P2, RX_P3, RX_P4, RX_P5, RX_P6, RX_P7, and RX_P8, which are enabled or activated to receive a reception signal in a reception mode. One channel can include one transmission path and one reception path. For example, the first channel 1100-1 can include the transmission path TX_P1 and the reception path RX_P1. It will be described with reference to FIGS. 2 to 4 that the configuration of each channel. Figure 2 The configuration of each channel will be described.

[0058] The plurality of combiners / splitters 1200-1 to 1200-4 and 1300-1 to 1300-3 can operate as splitters for dividing or distributing a transmission signal in a transmission mode, and can operate as combiners for combining or synthesizing a reception signal in a reception mode.

[0059] Each of the combiners / splitters 1200-1 to 1200-4 can be connected to two adjacent channels. For example, the combiner / splitter 1200-1 can be directly connected to the first and second channels 1100-1 and 1100-2, can split a signal provided to the first and second channels 1100-1 and 1100-2 in a transmission mode, and can combine signals received from the first channel 1100-1 and the second channel 1100-2 in a reception mode.

[0060] Each of the combiners / splitters 1300-1 to 1300-3 can be connected to two adjacent combiners / splitters. For example, the combiner / splitter 1300-1 can be directly connected to the combiners / splitters 1200-1 and 1200-2, can split the signals provided to the first to fourth channels 1100-1 to 1100-4 in the transmission mode, and can combine the signals received from the first to fourth channels 1100-1 to 1100-4 in the reception mode.

[0061] The signal processor 1400 can perform signal processing to generate a transmission signal in the transmission mode, and can perform signal processing on a reception signal in the reception mode. For example, the signal processing can include encoding / decoding, encryption / decryption, and / or modulation / demodulation, etc. operations, and can include signal processing on a baseband signal, signal processing on an intermediate frequency signal, and signal processing on a radio frequency (RF) signal. In other words, the signal processor 1400 can perform both digital signal processing and subsequent RF signal processing, and the signal processor 1400 can be referred to as a signal processing and RF up-converter (or RF transceiver). Also, according to an example embodiment, the signal processor 1400 can generate a test signal TS for calibrating phases and gains between channels.

[0062] The calibration circuit calibrates or compensates for phases and gains between channels. The calibration circuit includes a selection unit, a power detector 2500, an analog-to-digital converter (ADC) 2600, and a calibrator 2700.

[0063] The selection unit is connected to the plurality of channels 1100-1 to 1100-8. The selection unit selects two channels from among the plurality of channels 1100-1 to 1100-8, provides the test signal TS to the selected two channels, and receives a test result signal TRS from the selected two channels.

[0064] The selection unit can include a plurality of power couplers 2100-1, 2100-2, 2100-3, 2100-4, 2100-5, 2100-6, 2100-7, and 2100-8, a plurality of first channel selection structures 200-1, 2200-2, 2200-3, and 2200-4, a plurality of second channel selection structures 2300-1, 2300-2, and 2300-3, and a transceiving channel selector 2400.

[0065] The plurality of power couplers 2100-1 to 2100-8 can be connected to the plurality of channels 1100-1 to 1100-8 and can be used to obtain power from the plurality of channels 1100-1 to 1100-8. One power coupler can be connected to one channel, and the number of power couplers 2100-1 to 2100-8 can be substantially equal to the number of channels 1100-1 to 1100-8. For example, the power coupler 2100-1 can be directly connected to the first channel 1100-1. For example, as shown in FIG. 2, the plurality of power couplers 2100-1 to 2100-8 can be directional couplers. Figure 1

[0066] The plurality of first channel selection structures 2200-1 to 2200-4 can be connected to the plurality of power couplers 2100-1 to 2100-8. Each of the plurality of first channel selection structures 2200-1 to 2200-4 can be connected to two adjacent power couplers. For example, the first channel selection structure 2200-1 can be directly connected to the power couplers 2100-1 and 2100-2 and can add or sum two signals provided by the power couplers 2100-1 and 2100-2 or can block at least one of the two signals.

[0067] The plurality of second channel selection structures 2300-1 to 2300-3 can be connected to the plurality of first channel selection structures 2200-1 to 2200-4. Each of the plurality of second channel selection structures 2300-1 to 2300-3 can be connected to two adjacent channel selection structures. For example, the second channel selection structure 2300-1 can be directly connected to the first channel selection structures 2200-1 and 2200-2 and can add or sum two signals provided by the first channel selection structures 2200-1 and 2200-2 or can block at least one of the two signals.

[0068] In some example embodiments, each of the plurality of first and second channel selection structures 2200-1 to 2200-4 and 2300-1 to 2300-3 can not be implemented as a simple switch (e.g., a single-pole double-throw (SPDT) switch) but can be implemented to add two input signals, pass neither of the two input signals, or pass only one signal and not the other. In addition, each of the plurality of first and second channel selection structures 2200-1 to 2200-4 and 2300-1 to 2300-3 can be implemented to accurately maintain impedance matching even when a signal is not passed. For example, as shown in FIG. 2, each channel selection structure can include a switched Wilkinson combiner (or splitter). However, example embodiments are not limited thereto, and each channel selection structure can be implemented with various structures to perform the above-described roles and functions. Figure 1 ​​

[0069] The transceiving channel selector 2400 can be connected to the second channel selection structure 2300-3, and can receive the test result signal TRS. The transceiving channel selector 2400 can be used to select whether to calibrate the phases and gains of the plurality of transmission paths TX_P1 to TX_P8 or to calibrate the phases and gains of the plurality of reception paths RX_P1 to RX_P8. For example, the transceiving channel selector 2400 can include a double-pole double-throw (DPDT) switch. The operation of the transceiving channel selector 2400 will be described with reference to Figure 8A and 8B The operation of the transceiving channel selector 2400 is described.

[0070] The power detector 2500 detects the power of the selected two channels based on the test result signal TRS provided from the selection unit. For example, the power detector 2500 can include an envelope detector. The envelope of the test result signal TRS obtained from the signals from the selected two channels can be measured, and the phase and gain difference between the selected two channels can be effectively detected and calibrated based on the size of the envelope.

[0071] The analog-to-digital converter 2600 performs analog-to-digital conversion on the output of the power detector 2500. The calibrator 2700 calibrates the phases and gains between the plurality of channels 1100-1 to 1100-8 based on the output of the analog-to-digital converter 2600. Although not shown in detail, the calibrator 2700 can generate a plurality of control signals (or calibration signals) for controlling the phases and gains of the plurality of channels 1100-1 to 1100-8, and can provide the plurality of control signals to the plurality of channels 1100-1 to 1100-8.

[0072] The calibrator 2700 calibrates the phases and gains of the plurality of channels 1100-1 to 1100-8 based on a multi-channel (or two-channel) signal comparison scheme. For example, one of the plurality of channels 1100-1 to 1100-8 is set or determined as a reference channel, the phases and gains of the remaining channels other than the reference channel among the plurality of channels 1100-1 to 1100-8 are sequentially optimized based on or using the reference channel, and the phases and gains of the reference channel are optimized based on one of the remaining channels. In some example embodiments, the operation of setting the reference channel can be performed two or more times. In other words, the reference channel can change at least once. The calibration operation of the calibrator 2700 will be described in detail with reference to Figure 3 and the subsequent drawings.

[0073] Figure 2 is a block diagram illustrating an example of a channel included in a multi-channel beamforming system according to an example embodiment.

[0074] Reference will be made to Figure 2The channel 1100 can include a power amplifier (PA) 1110, a low noise amplifier (LNA) 1120, variable gain phase shifters (VG-PS) 1130 and 1140, switch circuits 1150 and 1160, and an antenna 1170.

[0075] The power amplifier 1110 can amplify a signal to be transmitted through the antenna 1170 in a transmission mode. For example, the power amplifier 1110 can include a multi-mode power amplifier (MM-PA) that operates in two or more amplification modes and performs a transmission gain adjustment (or control) function on a signal.

[0076] The low noise amplifier 1120 can amplify a signal received through the antenna 1170 in a reception mode. For example, the low noise amplifier 1120 can include a variable gain low noise amplifier (VG-LNA) that performs a reception gain adjustment function and further performs a phase change compensation function.

[0077] The variable gain phase shifters 1130 can independently perform a transmission gain adjustment function and a transmission phase adjustment function on an input provided to the power amplifier 1110 at a time (or simultaneously) in a transmission mode. The variable gain phase shifters 1140 can independently perform a reception gain adjustment function and a reception phase adjustment function on an output of the low noise amplifier 1120 at a time in a reception mode. The variable gain phase shifters 1130 and 1140 can receive a control signal CAL provided from a calibrator (e.g., the calibrator 2700 in FIG. 27), and can perform an operation of adjusting or controlling the phase and gain between the channels based on the control signal CAL according to example embodiments. Figure 1

[0078] In each of the variable gain phase shifters 1130 and 1140, an output signal can be generated by adjusting or controlling the magnitude and direction of at least two in-phase vectors and at least two quadrature vectors and by summing the at least two in-phase vectors and the at least two quadrature vectors. Accordingly, the phase and gain of a signal can be simultaneously and independently adjusted or controlled using one element or block effectively.

[0079] The power amplifier 1110 and the variable gain phase shifters 1130 can form a transmission path, and the low noise amplifier 1120 and the variable gain phase shifters 1140 can form a reception path. In some example embodiments, the channel 1100 can include only one variable gain phase shifter, and the one variable gain phase shifter can be shared by the transmission path and the reception path.

[0080] The switch circuits 1150 and 1160 can enable or activate one of the transmission path and the reception path. For example, each of the switch circuits 1150 and 1160 can include an SPDT switch. As Figure 2 ​As shown, the transmission path can be enabled when the switch circuits 1150 and 1160 are electrically connected to the power amplifier 1110 and the variable gain phase shifter 1130. Although not shown above, the reception path can be enabled when the switch circuits 1150 and 1160 are connected to the low noise amplifier 1120 and the variable gain phase shifter 1140. Figure 2 As shown, the transmission path can be enabled when the switch circuits 1150 and 1160 are electrically connected to the power amplifier 1110 and the variable gain phase shifter 1130. Although not shown above, the reception path can be enabled when the switch circuits 1150 and 1160 are connected to the low noise amplifier 1120 and the variable gain phase shifter 1140.

[0081] The position where the power coupler (e.g., the power coupler 2100-1 in Figure 1 ) is connected can correspond to the output end of the transmission path and the input end of the reception path. For example, the power coupler can be connected between the antenna 1170 and the switch circuit 1160.

[0082] Figure 3 is a flowchart illustrating a channel calibration method according to an example embodiment. The channel calibration method will be described based on the multi-channel beamforming system 100 Figure 1 . The channel calibration method of Figure 3 and the calibration circuit included therein.

[0083] Referring to Figure 1 and Figure 3 , in the channel calibration method according to an example embodiment using the calibration circuit included in the multi-channel beamforming system 100, a first channel 1100-1 is selected as a reference channel (step S110). Next, the remaining channels, for example, second to eighth channels 1100-2 to 1100-8, are sequentially selected as comparison channels, and the second to eighth channels 1100-2 to 1100-8 are sequentially set to have the lowest power at a first phase (e.g., power lower than a reference power). For example, the first phase can be about 0 degrees.

[0084] For example, K can be set to two (step S120), the Kth channel (e.g., the second channel 1100-2) can be selected as a comparison channel (step S130), and the Kth channel can be set to have the lowest power at the first phase (step S150). Step S150 will be described with reference to Figure 4 and 5 .

[0085] When steps S130 and S150 are not performed until the last channel (e.g., the eighth channel 1100-8) (step S170: No), K can be increased by one (step S180), and steps S130 and S150 are repeatedly performed for the next channel (e.g., the third channel 1100-3). Based on such repetition, the second to eighth channels 1100-2 to 1100-8, except for the first channel 1100-1, can be calibrated to have the best phase / gain state at the same phase.

[0086] When steps S130 and S150 are performed for all of the eight channels (e.g., eighth channel 1100-8) (step S170: YES), the first channel 1100-1 can be calibrated to have the best phase / gain state at the same phase.

[0087] For example, the second channel 1100-2 is selected as the reference channel (step S210), the third channel 1100-3 is selected as the comparison channel (step S230), and the third channel 1100-3 is set to have the lowest power at a second phase different from the first phase (step S250). For example, the second phase can be approximately 180 degrees. The reference channel 1100-2 is set to have the best phase / gain state at the first phase (step S260). Figure 6 The step S250 is described.

[0088] Thereafter, the third channel 1100-3 is selected as the reference channel (step S310), the first channel 1100-1 is selected as the comparison channel (step S330), and the first channel 1100-1 is set to have the lowest power at the first phase (step S350). The step S350 can be substantially the same as the step S150. Finally, all of the first to eighth channels 1100-1 to 1100-8 can be calibrated to have the best phase / gain state at the same phase.

[0089] The processes performed in the steps S150, S250, and S350 can be referred to as offset lookup functions.

[0090] Although the example embodiments describe that a specific channel is selected as the reference channel and / or the comparison channel in the steps S110, S210, S230, S310, and S330, the example embodiments are not limited thereto. For example, the reference channel selected in the step S110 can be any one of the plurality of channels 1100-1 to 1100-8, the reference channel and the comparison channel selected in the steps S210 and S230 can be any two of the remaining channels other than the channel selected in the step S110, the reference channel selected in the step S310 can be the same channel as the channel selected in the step S230, and the comparison channel selected in the step S330 can be the same channel as the channel selected in the step S110.

[0091] Figure 4 is a flowchart illustrating an example of the step S150 of Figure 3 is a flowchart illustrating an example of the step S250 of Figure 5 is a diagram for explaining the operation of Figure 4 is a flowchart illustrating an example of the step S350 of Figure 6 is a flowchart illustrating an example of the step S250 of Figure 3 is a flowchart illustrating an example of the step S250 of

[0092] Referring to Figure 1 , 3, 4 and 5, when the Kth channel is set to have the lowest power at the first phase (step S150), the operation is described based on the example of K=2, for example, the second channel 1100-2 is selected as the comparison channel, and the first phase and the second phase are taken as an example of about 0 degrees and about 180 degrees, respectively.

[0093] The phase and the gain of the first channel 1100-1 as the reference channel can be set to the second phase and the first gain (step S510). The phase and the gain of the second channel 1100-2 as the comparison channel can be set to the third phase and the first gain (step S520). The remaining channels 1100-3 to 1100-8 other than the first and second channels 1100-1 and 1100-2 can be in an off state, or signals output from the remaining channels 1100-3 to 1100-8 can be blocked using the first channel selection structure 2200-2 to 2200-4. For example, the third phase can be about -10 degrees close to the first phase, and the first gain can be about -2 dB. However, example embodiments are not limited thereto, and the third phase and the first gain can be determined differently according to example embodiments. Alternatively, step S520 can be described as an operation of storing a present (or current) phase and gain code value (or state) of the comparison channel.

[0094] The test result signal TRS can be obtained by summing the signals obtained from the first channel 1100-1 and the second channel 1100-2 based on the test signal TS, and the reference output power Pout_ref can be measured based on the test result signal TRS (step S530).

[0095] Next, only the phase and the gain of the second channel 1100-2 can be adjusted while the phase and the gain of the first channel 1100-1 are maintained and / or fixed (step S540). After adjusting the phase and the gain of the second channel 1100-2, the test result signal TRS can be obtained again by adding the signals obtained again from the first channel 1100-1 and the second channel 1100-2 based on the test signal TS, and the comparison output power Pout_comp can be measured based on the test result signal TRS (step S550).

[0096] When the comparison output power Pout_comp is lower than (or less than) the reference output power Pout_ref (step S560: Yes), it can be indicated that the phase and gain adjusted in step S540 are closer to the optimal phase / gain state than the phase and gain before adjustment, so the current phase and current gain of the second channel 1100-2 can be stored (step S570). Thereafter, the comparison output power Pout_comp of the current phase and current gain can be set as the reference output power Pout_ref, and steps S540, S550, and S560 can be repeated based on the newly set reference output power Pout_ref.

[0097] When the comparison output power Pout_comp is higher than (or greater than) or equal to the reference output power Pout_ref (step S560: No), it can be said that the phase and gain before adjustment are closer to the optimal phase / gain state than the phase and gain after adjustment in step S540. Therefore, step S570 can be skipped and steps S540, S550 and S560 can be repeated.

[0098] Based on the repetition of steps S540, S550, and S560, the phase and gain of the second channel 1100-2 can be set to have minimum phase error (e.g., zero-degree phase error) and minimum gain error (e.g., zero dB gain error). For example, if step S570 is not executed consecutively more than the reference number even after repeating steps S540, S550, and S560, it can be determined that the storage phase and storage gain of the second channel 1100-2 are in an optimal phase / gain state, and the process can be terminated.

[0099] like Figure 5 As shown, when the reference channel is rotated approximately 180 degrees and the two signals from the reference and comparison channels are added together, while simultaneously changing the phase and gain of the comparison channel, the lowest power (e.g., power below the reference power) can be detected when the phase difference between the two signals is approximately 180 degrees and there is no gain error. Adjustments can be made such that the comparison channel has optimal phase / gain around 0 degrees, for example, a comparison channel with 0-degree phase error and 0dB gain error.

[0100] After completing the above process for the second channel 1100-2, the above process can be performed sequentially for the third to eighth channels 1100-3 to 1100-8.

[0101] Reference Figure 1 , 3 In step S250, when the third channel 1100-3 is set to have the lowest power in the second phase, the operation will be described based on examples where the first phase and the second phase are approximately 0 degrees and approximately 180 degrees, respectively.

[0102] The phase and gain of the second channel 1100-2, which is the reference channel, can be set to the first phase and the first gain, which are set by the operation (step S610) of Figure 4 and 5 The phase and gain of the third channel 1100-3, which is the comparison channel, can be set to the fourth phase and the first gain (step S620). For example, the fourth phase can be about 170 degrees close to the second phase, and the first gain can be about -2 dB. However, example embodiments are not limited thereto, and the fourth phase and the first gain can be determined differently according to example embodiments. Alternatively, step S620 can be described as an operation of storing the current phase and gain code values (or states) of the comparison channel. Steps S610 and S620 can be substantially the same as steps S510 and S520 in Figure 4 , respectively, except for the phase setting values.

[0103] Thereafter, steps S630, S640, S650, S660, and S670 can be substantially the same as steps S530, S540, S550, S560, and S570 in Figure 4 , respectively, Figure 4 and repetitive descriptions will be omitted.

[0104] Figure 7A , 7B , 7C, and 7D are diagrams for describing the operations of Figure 3 .

[0105] First, referring to Figure 7A and 7B , an example of performing steps S110, S120, S130, S150, S170, and S180 in Figure 3 is shown.

[0106] For example, as shown in Figure 7A , the calibration circuit can enable only the first and second channels 1100-1 and 1100-2 and the signal paths related thereto, and can disable the remaining channels 1100-3 to 1100-8 and the signal paths related thereto. In Figure 7A and subsequent diagrams, the disabled components and the disabled signal paths are illustrated by dotted lines. The calibration circuit can set the first channel 1100-1 to about 180 degrees and can set the second channel 1100-2 to about 0 degrees by performing the procedures described with reference to Figure 4 and Figure 5 . In order to set the second channel 1100-2, a test signal TS12 can be provided to the first channel 1100-1 and the second channel 1100-2, and a test result signal TRS12 can be received from the first channel 1100-1 and the second channel 1100-2.

[0107] Similarly, each of the third through seventh channels 1100-3 through 1100-7 can be set to approximately 0 degrees.

[0108] Finally, as shown in Figure 7B , the calibration circuit can enable only the first and eighth channels 1100-1 and 1100-8 and the signal paths associated therewith, and can set the eighth channel 1100-8 to approximately 0 degrees by performing the procedures described with reference to Figure 4 and Figure 5 To set the eighth channel 1100-8, test signals TS18 can be provided to the first and eighth channels 1100-1 and 1100-8, and test result signals TRS18 can be received from the first and eighth channels 1100-1 and 1100-8.

[0109] Next, with reference to Figure 7C , examples of performing steps S210, S230, S250 in Figure 3 are shown.

[0110] For example, the calibration circuit can enable only the second and third channels 1100-2 and 1100-3 and the signal paths associated therewith, can set the second channel 1100-2 to approximately 0 degrees by performing the procedures described with reference to Figure 6 and can set the third channel 1100-3 to approximately 180 degrees. To set the third channel 1100-3, test signals TS23 can be provided to the second and third channels 1100-2 and 1100-3, and test result signals TRS23 can be received from the second and third channels 1100-2 and 1100-3.

[0111] Next, with reference to Figure 7D , examples of performing steps S310, S330, and S350 in Figure 3 are shown.

[0112] For example, the calibration circuit can enable only the first and third channels 1100-1 and 1100-3 and the signal paths associated therewith, can set the third channel 1100-3 to approximately 180 degrees by performing the procedures described with reference to Figure 4 and Figure 5 and can set the first channel 1100-1 to approximately 0 degrees. To set the first channel 1100-1, test signals TS31 can be provided to the first and third channels 1100-1 and 1100-3, and test result signals TRS31 can be received from the first and third channels 1100-1 and 1100-3.

[0113] When all of the above processes are completed, all of the plurality of channels 1100-1 to 1100-8 can be set to have the same phase, for example, can have the best phase / gain state at the same phase, so that phase and gain errors occurring in the chip can be compensated for.

[0114] Although the example embodiments are described as performing error calibration on only one phase (e.g., the first phase), the example embodiments are not limited thereto, and can perform error calibration on a plurality of phases (or two or more phases). For example, in order to calibrate errors caused by differences between phase states of the phase shifters, synchronization can be performed in all phases by changing the phase of the reference channel by, for example, about 11.2 degrees in a 5-bit phase shifter, so that a more accurate beam pattern can be generated or formed.

[0115] Figure 8A and 8B are diagrams for describing the operation of the calibration circuit and the multi-channel beamforming system of Figure 1 .

[0116] Referring to Figure 2 , 8A and 8B, using the switch circuits (e.g., switch circuits 1150 and 1160 in Figure 2 ) included in the plurality of channels 1100-1 to 1100-8 and the transceiving channel selector 2400 included in the calibration circuit, it can be relatively easy and simple to calibrate the transmission path and the reception path. Figure 8A and 8B show an example of performing a calibration operation of the seventh channel 1100-7 by selecting the first and seventh channels 1100-1 and 1100-7.

[0117] As Figure 8AAs shown, the transmission paths TX_P1 and TX_P7 in the first and seventh channels 1100-1 and 1100-7 can be enabled using the switch circuits included in the first and seventh channels 1100-1 and 1100-7, and the DPDT switches included in the transceiving channel selector 2400 can be connected as shown. A test signal TS17_TX can correspond to a transmission signal to be output in a transmission mode. The test signal TS17_TX can be provided to the input ends of the transmission paths TX_P1 and TX_P7 through the transceiving channel selector 2400 and the combiner / splitter 1200-1, 1200-4 and 1300-1 to 1300-3. Signals can be fed back from the output ends of the transmission paths TX_P1 and TX_P7, which can be received as test result signals TRS17_TX through the power couplers 2100-1 and 2100-7 and the channel selection structures 2200-1, 2200-4 and 2300-1-2300-3, which can be provided to the transceiving channel selector 2400. The transmission path TX_P7 in the seventh channel 1100-7 can be set based on the test signal TS17_TX and the test result signals TRS17_TX.

[0118] In addition, as Figure 8B As shown, the transmission paths TX_P1 and TX_P7 in the first and seventh channels 1100-1 and 1100-7 can be enabled using the switch circuits included in the first and seventh channels 1100-1 and 1100-7, and the DPDT switches included in the transceiving channel selector 2400 can be connected as shown. A test signal TS17_TX can correspond to a transmission signal to be output in a transmission mode. The test signal TS17_TX can be provided to the input ends of the transmission paths TX_P1 and TX_P7 through the transceiving channel selector 2400 and the combiner / splitter 1200-1, 1200-4 and 1300-1 to 1300-3. Signals can be fed back from the output ends of the transmission paths TX_P1 and TX_P7, which can be received as test result signals TRS17_TX through the power couplers 2100-1 and 2100-7 and the channel selection structures 2200-1, 2200-4 and 2300-1-2300-3, which can be provided to the transceiving channel selector 2400. The transmission path TX_P7 in the seventh channel 1100-7 can be set based on the test signal TS17_TX and the test result signals TRS17_TX.

[0119] Based on the above-described scheme, the plurality of transmission paths TX_P1 to TX_P8 and the plurality of reception paths RX_P1 to RX_P8 can be calibrated independently. In other words, the reference Figure 3The process described with respect to FIG. 7, and also can be performed with respect to the multiple receive paths RX_P1 to RX_P8, is referred to as a phase and gain calibration process. Figure 3 The process described with respect to FIG. 7.

[0120] In the calibration circuit, the multi-channel beamforming system, and the channel calibration method according to example embodiments, the phases and gains of the multiple channels 1100-1 to 1100-8 can be calibrated based on a multi-channel signal comparison scheme, in which envelope detectors can be used to compare feedback signals instead of using a local oscillator (LO) and an in-phase / quadrature-phase (I / Q) mixer. By fixing the phase and gain of one channel, adjusting the phase and gain of another channel, and measuring the envelope of the summed signal of the two channels, the difference in phase and gain between the two channels can be detected, which can be calibrated by using or feeding back the difference. Thus, it can be less sensitive to frequency and can have no LO issues and direct current (DC) offset issues because no I / Q mixer is used. In addition, both the transmit and receive paths can be easily calibrated by just changing the direction of the switches.

[0121] Figure 9 is a block diagram illustrating a calibration circuit and a multi-channel beamforming system including the calibration circuit according to example embodiments. As described with respect to Figure 1 Repetitive description will be omitted.

[0122] Referring to Figure 9 , the multi-channel beamforming system 200 includes multiple channels 1100-1 to 1100-8, and a calibration circuit. The multi-channel beamforming system 200 can further include multiple combiners / splitters 1200-1 to 1200-4 and 1300-1 to 1300-3, and a signal processor 1400.

[0123] Figure 9 The multi-channel beamforming system 200 of Figure 1 is substantially the same as the multi-channel beamforming system 100 of

[0124] The calibration circuit includes a selection unit, a power detector 3600, an analog-to-digital converter 3700, and a calibrator 3800. The power detector 3600, the analog-to-digital converter 3700, and the calibrator 3800 can be substantially the same as the power detector 2500, the analog-to-digital converter 2600, and the calibrator 2700, respectively, of Figure 1

[0125] ​The selection unit can include a plurality of quarter wavelength (λ / 4) transformers 3100-11, 3100-21, 3100-31, 3100-41, 3100-51, 3100-61, 3100-71, 3100-81, 3100-12, 3100-22, 3100-32, 3100-42, 3100-52, 3100-62, 3100-72, and 3100-82, a plurality of switches 3200-1, 3200-2, 3200-3, 3200-4, 3200-5, 3200-6, 3200-7, and 3200-8, a plurality of half wavelength (λ / 2) transformers 3300-1, 3300-2, 3300-3, and 3300-4, a combiner / splitter 3400, and a transceiver channel selector 3500. Wavelength (λ) can represent the wavelength of a signal transmitted and received through the multi-channel beamforming system 200.

[0126] The plurality of quarter wavelength transformers 3100-11 through 3100-81 and 3100-12 through 3100-82 can be connected to the plurality of channels 1100-1 through 1100-8. Two quarter wavelength transformers can be connected to one channel, and the number of quarter wavelength transformers 3100-11 through 3100-81 and 3100-12 through 3100-82 can be substantially equal to twice the number of channels 1100-1 through 1100-8. For example, the quarter wavelength transformer 3100-11 can be directly connected to the first channel 1100-1, and the quarter wavelength transformer 3100-12 can be directly connected to the quarter wavelength transformer 3100-11.

[0127] The plurality of switches 3200-1 through 3200-8 can be connected to the plurality of quarter wavelength transformers 3100-11 through 3100-81 and 3100-12 through 3100-82, and can be connected to the plurality of channels 1100-1 through 1100-8 through the plurality of quarter wavelength transformers 3100-11 through 3100-81 and 3100-12 through 3100-82. One switch can be connected to one channel, and the number of switches 3200-1 through 3200-8 can be substantially equal to the number of channels 1100-1 through 1100-8. For example, the switch 3200-1 can be directly connected between a node between the quarter wavelength transformers 3100-11 and 3100-12 and a ground voltage. When the switch 3200-1 is open, the first channel 1100-1 can be selected.

[0128] Multiple half-wavelength converters 3300-1 to 3300-4 can be connected to multiple quarter-wavelength converters 3100-12 to 3100-82. Each of the multiple half-wavelength converters 3300-1 to 3300-4 can be connected to two adjacent quarter-wavelength converters. For example, half-wavelength converter 3300-1 can be directly connected to quarter-wavelength converters 3100-12 and 3100-22.

[0129] The combiner / splitter 3400 can be connected to multiple half-wavelength converters 3300-1 to 3300-4, and can operate similarly to combiners / splitters 1200-1 to 1200-4 and 1300-1 to 1300-3. The transmit / receive channel selector 3500 can be connected to the combiner / splitter 3400, can receive the test result signal TRS, and can... Figure 1 The transmit / receive channel selector in the 2400 is basically the same.

[0130] Unlike Figure 1 A multi-channel beamforming system 100, including Figure 9 In the multi-channel beamforming system 200, the selection unit cannot simultaneously select two adjacent channels. For example, when the first channel 1100-1 is selected as the reference channel, the second to fourth channels 1100-2 to 1100-4 cannot be selected as comparison channels; instead, only the fifth to eighth channels 1100-5 to 1100-8 can be selected as comparison channels. Therefore, in Figure 9 In the multi-channel beamforming system 200, the reference function cannot be executed. Figure 3 The channel calibration method described in Figure 7 can be performed using a reference. Figure 10 to 1 3. The channel calibration method is described.

[0131] Figure 10 This is a flowchart illustrating a channel calibration method according to an example embodiment. It will be based on... Figure 9 Description of the multi-channel beamforming system 200 and its included calibration circuitry Figure 10 The channel calibration method. (And) Figure 3 Duplicate descriptions will be omitted.

[0132] Reference Figure 9 and Figure 10 In a channel calibration method according to an example embodiment using a calibration circuit included in a multi-channel beamforming system 200, a plurality of channels 1100-1 to 1100-8 can be divided into a first channel group including channels 1100-1 to 1100-4 and a second channel group including channels 1100-5 to 1100-8, and a calibration operation can be performed for each channel group.

[0133] First, the first channel 1100-1 is selected as a reference channel (step S1110), and the channels 1100-5 to 1100-8 included in the second channel group are sequentially selected as comparison channels, the fifth to eighth channels 1100-5 to 1100-8 are sequentially set to have the lowest power at the first phase.

[0134] For example, K can be set to N / 2+1 (step S1120), the Kth channel (e.g., the fifth channel 1100-5) can be selected as a comparison channel (step S1130), and the Kth channel can be set to have the lowest power at the first phase (step S1150). When steps S1130 and S1150 are not performed until the last channel (e.g., the eighth channel 1100-8) in the second channel group (step S1170: No), K can be increased by one (step S1180), and steps S1130 and S1150 can be repeated. Based on such repetition, the channels 1100-5 to 1100-8 included in the second channel group can be calibrated to have the best phase / gain state at the same phase.

[0135] Steps S1110, S1120, S1130, S1150, S1170, and S1180 can be similar to steps S110, S120, S130, S150, S170, and S180, respectively, in Figure 3 .

[0136] Next, the fifth channel 1100-5 is selected as a reference channel (step S1210), and the channels 1100-1 to 1100-4 included in the first channel group are sequentially selected as comparison channels, the first to fourth channels 1100-1 to 1100-4 are sequentially set to have the lowest power at the first phase.

[0137] For example, K can be set to one (step S1220), the Kth channel (e.g., the first channel 1100-1) can be selected as a comparison channel (step S1230), and the Kth channel can be set to have the lowest power at the first phase (step S1250). When steps S1230 and S1250 are not performed until the last channel (e.g., the fourth channel 1100-4) in the first channel group (step S1270: No), K can be increased by one (step S1280), and steps S1230 and S1250 can be repeatedly performed. Based on such repetition, the channels 1100-1 to 1100-4 included in the first channel group can be calibrated to have the best phase / gain state at the same phase.

[0138] Steps S1210, S1220, S1230, S1250, S1270, and S1280 can be similar to steps S1110, S1120, S1130, S1150, S1170, and S1180, respectively.

[0139] Figure 11A , 11B , 11C and 11D are diagrams for describing the operations of Figure 10 .

[0140] First, referring to Figure 11A and 11B , an example of performing steps S1110, S1120, S1130, S1150, S1170, and S1180 in Figure 10 is shown.

[0141] For example, as shown in Figure 11A , the calibration circuit can enable only the first and fifth channels 1100-1 and 1100-5 and the signal paths related thereto, can set the first channel 1100-1 to about 180 degrees by performing the procedures described with reference to Figure 4 and Figure 5 , and can set the fifth channel 1100-5 to about 0 degrees. To set the fifth channel 1100-5, the test signal TS15 and the test result signal TRS15 can be used.

[0142] Similarly, each of the sixth and seventh channels 1100-6 to 1100-7 can be set to about 0 degrees.

[0143] Finally, as shown in Figure 11B , the calibration circuit can enable only the first and eighth channels 1100-1 and 1100-8 and the signal paths related thereto, and can set the eighth channel 1100-8 to about 0 degrees by performing the procedures described with reference to Figure 4 and 5 . To set the eighth channel 1100-8, the test signal TS18 and the test result signal TRS18 can be used.

[0144] Next, referring to Figure 11C and 11D , an example of performing steps S1210, S1220, S1230, S1250, S1270, and S1280 in Figure 10 is shown.

[0145] For example, as shown in Figure 11C , the calibration circuit can enable only the first and fifth channels 1100-1 and 1100-5 and the signal paths related thereto, can set the first channel 1100-1 to about 180 degrees by performing the procedures described with reference to Figure 4 and 5 . To set the fifth channel 1100-5, the test signal TS15 and the test result signal TRS15 can be used.The described process sets the fifth channel 1100-5 to approximately 180 degrees, and can set the first channel 1100-1 to approximately 0 degrees. For example, using the variable gain phase shifter included in the fifth channel 1100-5, the fifth channel 1100-5 can be set to approximately 180 degrees by rotating the phase of the fifth channel 1100-5 from approximately 0 degrees, as set by the operation of Figure 11A the test signal TS51 and the test result signal TRS51.

[0146] Similarly, each of the second and third channels 1100-2 to 1100-3 can be set to approximately 0 degrees.

[0147] Finally, as shown in Figure 11D , the calibration circuit can only enable the fourth and fifth channels 1100-4 and 1100-5 and the signal paths related thereto, and can set the fourth channel 1100-4 to approximately 0 degrees by performing the process described with reference to Figure 4 and Figure 5 . To set the fourth channel 1100-4, the test signal TS54 and the test result signal TRS54 can be used.

[0148] Figure 12 is a flowchart illustrating a channel calibration method according to an example embodiment. The channel calibration method will be described based on the multi-channel beamforming system 200 and the calibration circuit included therein, which are described with reference to Figure 9 . Descriptions repeated with Figure 12 and Figure 3 will be omitted. 10 Referring to

[0149] and Figure 9 , in the channel calibration method using the calibration circuit included in the multi-channel beamforming system 200 according to an example embodiment, Figure 12 the method of Figure 12 may be substantially the same as the method of Figure 10 except that step S1255 is changed. Steps S1110, S1120, S1130, S1150, S1170, S1180, S1210, S1220, S1230, S1270, and S1280 can be substantially the same as steps S1110, S1120, S1130, S1150, S1170, S1180, S1210, S1220, S1230, S1270, and S1280 in Figure 10 , respectively.

[0150] In Figure 12In this method, the Kth channel can be configured to have the lowest power in the second phase (step S1255). Step S1255 can be similar to... Figure 3 Step S250 in the process.

[0151] Figure 13A and 13B It is used to describe Figure 12 The diagram shows the operation.

[0152] Reference Figure 13A and 13B This shows the execution Figure 12 Examples of steps S1210, S1220, S1230, S1255, S1270 and S1280 in the process.

[0153] For example, the calibration circuit can enable only the first and fifth channels 1100-1 and 1100-5 and their associated signal paths by performing a reference. Figure 6 The described process sets the fifth channel 1100-5 to approximately 0 degrees, and the first channel 1100-1 can be set to approximately 180 degrees. Unlike... Figure 11C For example, rotating the phase of the fifth channel 1100-5 may be unnecessary.

[0154] Similarly, each of the second and third channels 1100-2 to 1100-3 can be set to approximately 180 degrees.

[0155] Finally, as Figure 13B As shown, the calibration circuit can enable only channels 4 and 5, 1100-4 and 1100-5, and their associated signal paths, and can be activated by performing a reference... Figure 6 The described process sets the fourth channel 1100-4 to approximately 180 degrees.

[0156] When based on Figure 12 When performing calibration using this method, channels 1100-5 to 1100-8 in the second channel group can be calibrated to have an optimal phase / gain state of approximately 0 degrees, and channels 1100-1 to 1100-4 in the first channel group can be calibrated to have an optimal phase / gain state of approximately 180 degrees. In other words, channels 1100-1 to 1100-4 in the first channel group and channels 1100-5 to 1100-8 in the second channel group can be set differently (e.g., they can be set to differ by approximately 180 degrees). Even with the channels set in this way, offsets generated within the chip can be calibrated.

[0157] Although not detailed, Figure 1 The multi-channel beamforming system 100 can also perform Figure 10 and12 a channel calibration method.

[0158] Figure 14 is a block diagram illustrating a calibration circuit and a multi-channel beamforming system including the calibration circuit according to an example embodiment. As in Figure 1 and 9 repeated descriptions will be omitted.

[0159] Referring to Figure 14 , the multi-channel beamforming system 300 includes a plurality of channels 1100-a, 1100-b, 1100-c, 1100-d, 1100-e, 1100-f, 1100-g, and 1100-h, and a calibration circuit. The multi-channel beamforming system 300 can further include a plurality of combiners / splitters 1200-1 to 1200-4 and 1300-1 to 1300-3, and a signal processor 1400.

[0160] Figure 14 The multi-channel beamforming system 300 can be substantially the same as the multi-channel beamforming system 100 of Figure 1 except for changing the configuration of the plurality of channels 1100-a to 1100-h and the calibration circuit.

[0161] Unlike the plurality of channels 1100-1 to 1100-8 in Figure 1 , the plurality of channels 1100-a to 1100-h can include only a plurality of transmission paths TX_P1 to TX_P8. For example, in the case where the chip size is not important, such as a base station, or in the case of a radar system, etc., the transmission path and the reception path can be separated from each other to be manufactured as two or more chips.

[0162] The calibration circuit includes a selection unit, a power detector 4500, an analog-to-digital converter 4600, and a calibrator 4700. The power detector 4500, the analog-to-digital converter 4600, and the calibrator 4700 can be substantially the same as the power detector 2500, the analog-to-digital converter 2600, and the calibrator 2700 in Figure 1 , respectively.

[0163] The selection unit can include a plurality of power couplers 4100-1, 4100-2, 4100-3, 4100-4, 4100-5, 4100-6, 4100-7, and 4100-8, a plurality of first channel selectors 4200-1, 4200-2, 4200-3, and 4200-4, a plurality of second channel selectors 4300-1 and 4300-2, and a combiner / splitter 4400.

[0164] The plurality of power couplers 4100-1 to 4100-8 can be substantially the same as the plurality of power couplers 2100-1 to 2100-8 in Figure 1The multiple power couplers 2100-1 to 2100-8 are basically the same.

[0165] Multiple first channel selectors 4200-1 to 4200-4 can be connected to multiple power couplers 4100-1 to 4100-8. Each of the multiple first channel selectors 4200-1 to 4200-4 can be connected to two adjacent power couplers. For example, first channel selector 4200-1 can be directly connected to power couplers 4100-1 and 4100-2.

[0166] Multiple second channel selectors 4300-1 and 4300-2 can be connected to multiple first channel selectors 4200-1 to 4200-4. Each of the multiple second channel selectors 4300-1 and 4300-2 can be connected to two adjacent channel selectors. For example, second channel selector 4300-1 can be directly connected to first channel selectors 4200-1 and 4200-2.

[0167] In some example embodiments, each of the plurality of first channel selectors 4200-1 to 4200-4 and the plurality of second channel selectors 4300-1 and 4300-2 may include a single-pole double-throw (SPDT) switch or a single-pole triple-throw (SP3T) switch. An SPDT switch can be used to allow only one of the two input signals, while an SP3T switch can be used to allow only one of the two input signals and can further be used to block both input signals.

[0168] The combiner / splitter 4400 can be connected to multiple second-channel selectors 4300-1 and 4300-2, and can be similar to... Figure 9 Combiner / splitter 3400.

[0169] and Figure 1 and Figure 9 The multi-channel beamforming systems 100 and 200 are different. Figure 14 The multiple channels 1100-a to 1100-h included in the multi-channel beamforming system 300 can consist only of multiple transmission paths TX_P1 to TX_P8; therefore, the transmit / receive channel selector in the selection unit included in the calibration circuit can be omitted or deleted. Figure 9 Like the multi-channel beamforming system 200, in Figure 14 In the multi-channel beamforming system 300, it is not possible to perform... Figure 3 The channel calibration method, but can be performed Figure 10 and 12 The channel calibration method.

[0170] Although not shown in detail, when included Figure 1 and Figure 9The plurality of channels 1100-1 to 1100-8 in the multi-channel beamforming systems 100 and 200 are implemented as Figure 14 the plurality of channels 1100-a to 1100-h in Figure 1 and 9 the transceiver channel selectors 2400 and 3500 can be omitted or removed.

[0171] Figure 15 , 16A and 16B are diagrams for describing a multi-channel beamforming system including a calibration circuit according to an example embodiment.

[0172] Referring to Figure 15 , an embodiment of a four-channel beamforming system having about 28 GHz in which a calibration circuit according to an example embodiment is integrated is shown.

[0173] Referring to Figure 16A , an envelope actually measured in a four-channel beamforming system of Figure 15 is shown, and the envelope is obtained based on a summed signal from the third channel and the fourth channel while changing the phase and the gain of the third channel and fixing the phase and the gain of the fourth channel. Referring to Figure 16B , one envelope actually measured in a four-channel beamforming system of Figure 15 is shown, and the envelope is obtained based on a summed signal from the second channel and the fourth channel while changing the phase and the gain of the second channel and fixing the phase and the gain of the fourth channel.

[0174] When there is no phase and gain error in each channel (for example, when there is a phase difference of about 180 degrees between two channels), the lowest power output can be seen. When the second channel and the third channel are set with the fourth channel as a reference, and the phase and gain error between the two channels is measured, it can be seen that the error is reduced from about 9 degrees and 1 dB error before calibration to about 1.2 degrees and 0.2 dB error after calibration. It can be seen that a high-efficiency calibration is performed using a relatively simple circuit, without an LO problem and a DC offset problem, because an I / Q mixer is not used.

[0175] Phase and gain error calibration between channels is a basic technology for 5G communication systems and / or beyond 5G (B5G) communication systems and radar systems and wireless power transmission systems affected by a side lobe increase. The conventional technology has a problem in that an LO is required, a DC offset problem occurs in an I / Q mixer, and a complex feedback circuit is required to calibrate a transmission and reception path. The conventional technology is more complex because calibration is performed using absolute values of phase and gain of each channel. In the calibration circuit and channel calibration method according to an example embodiment, calibration can be performed by setting a reference value (or channel) in a chip and using relative values instead of absolute values, and thus complexity can be reduced. In addition, an I / Q mixer can not be used, and thus an LO signal can not be required and a DC offset problem can not exist. In addition, the structure can be frequency-insensitive, and thus can be easily applied to a multi-band multi-channel chip, and both a transmission and reception path can be easily calibrated.

[0176] Figure 17 is a block diagram illustrating a multi-channel beamforming system according to an example embodiment.

[0177] Referring to Figure 17 , the beamforming system 8000 includes a transceiver 8100, a plurality of beamforming circuit arrays 8200a, 8200b,..., 8200h, an antenna array 8300, and a calibration circuit 8400. Although Figure 17 An 8x8 channel active phased array system is illustrated, but the number of elements or blocks included in the beamforming system can be variously determined according to an example embodiment.

[0178] In a transmission mode, the transceiver 8100 performs encoding / decoding, encryption / decryption, and / or modulation / demodulation, etc. operations on data to be transmitted, sequentially converts the data into a baseband signal, an intermediate frequency signal, and a radio frequency signal, and provides the converted signal to the plurality of beamforming circuit arrays 8200a to 8200h. In a reception mode, the transceiver 8100 performs operations such as encoding / decoding, encryption / decryption, and / or modulation / demodulation on an RF signal received from the antenna array 8300 and the plurality of beamforming circuit arrays 8200a to 8200h to sequentially convert the RF signal into an intermediate frequency signal, a baseband signal, and data.

[0179] The plurality of beamforming circuit arrays 8200a to 8200h includes a plurality of beamforming circuits. For example, the beamforming circuit array 8200a can include first to eighth beamforming circuits BFIC1-1, BFIC1-2,..., BFIC1-8. Although not shown in detail, each of the beamforming circuit arrays 8200b to 8200h can also include a plurality of beamforming circuits.

[0180] The antenna array 8300 includes a plurality of antennas. Each antenna can be connected to a corresponding beamforming circuit to transmit / receive a signal.

[0181] One beamforming circuit included in the plurality of beamforming circuit arrays 8200a to 8200h and one antenna included in the antenna array 8300 can correspond to a reference Figure 1 to 14 One channel described above.

[0182] The calibration circuit 8400 calibrates a phase and a gain between channels, and can be a calibration circuit according to the example embodiments described above. Figure 1 to 14

[0183] The above-described embodiments can be applied to various communication devices and systems including a multi-channel beamforming system, and various electronic devices and systems including various communication devices and systems. For example, the example embodiments can be applied to devices or systems such as a mobile phone, a smart phone, a tablet PC, a laptop computer, a personal digital assistant (PDA), a portable multimedia player (PMP), a digital camera, a portable game console, a navigation device, a wearable device, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, an electronic book reader, a virtual reality (VR) device, an augmented reality (AR) device, a robot device, etc.

[0184] Specifically, the example embodiments can be applied to, for example, a 5G mobile communication system (e.g., about 28 GHz, 40 GHz, etc.), a military radar and communication system (e.g., X-band, Ku-band, W-band, etc.), a satellite communication system (e.g., Ka-band, etc.), a car radar (e.g., an autonomous or self-driving vehicle) (e.g., about 79 GHz, etc.), a wireless power transmission (e.g., about 5.8 GHz, etc.), etc.

[0185] The foregoing is a description of example embodiments and should not be construed as limiting thereof. Although several example embodiments have been described, those skilled in the art will readily understand that many modifications can be made to the example embodiments without materially departing from the novel teachings and advantages of the inventive concept. Accordingly, all such modifications are intended to be included within the scope of the inventive concept as defined in the claims. Therefore, it is to be understood that the foregoing is a description of various example embodiments and should not be construed to limit the disclosed example embodiments to those described, and that modifications to the disclosed example embodiments, as well as other example embodiments, are intended to be included within the scope of the claims.​

Claims

1. A calibration circuit in a multi-channel beamforming system including a plurality of channels, the calibration circuit configured to calibrate phases and gains among the plurality of channels, the calibration circuit comprising: a selection unit connected to the plurality of channels, the selection unit configured to select two channels from the plurality of channels, to provide a test signal to the selected two channels, and to receive a test result signal from the selected two channels; a power detector including an envelope detector configured to detect an envelope of the test result signal, the power detector configured to measure powers of the selected two channels according to a magnitude of the envelope of the test result signal; an analog-to-digital converter configured to perform analog-to-digital conversion on an output of the power detector; and a calibrator configured to calibrate phases and gains among the plurality of channels based on an output of the analog-to-digital converter, wherein the plurality of channels includes a first channel to an Nth channel, where N is a natural number greater than or equal to three, the first channel is selected as a reference channel, a second channel to the Nth channel are sequentially selected as comparison channels, and the second channel to the Nth channel are sequentially set to have zero-degree phase error and zero-dB gain error at a first phase, from among the second channel to the Nth channel, the second channel is selected as a reference channel and a third channel is selected as a comparison channel, the third channel is set to have zero-degree phase error and zero-dB gain error at a second phase different from the first phase, and the third channel is selected as a reference channel, the first channel is selected as a comparison channel, and the first channel is set to have zero-degree phase error and zero-dB gain error at the first phase, wherein, when the second channel is set to have zero-degree phase error and zero-dB gain error at the first phase: a reference output power is measured based on the test result signals obtained from the first channel and the second channel when phases and gains of the first channel are set to the second phase and a first gain and phases and gains of the second channel are set to a third phase and the first gain, a comparison output power is measured based on the test result signals obtained from the first channel and the second channel after adjusting the phases and gains of the second channel while maintaining the phases and gains of the first channel, and the phases and gains of the second channel are set to have zero-degree phase error and zero-dB gain error based on a comparison result of the reference output power and the comparison output power, wherein, when the third channel is set to have zero-degree phase error and zero-dB gain error: a reference output power is measured based on the test result signals obtained from the second channel and the third channel when phases and gains of the second channel are set to the first phase and a first gain and phases and gains of the third channel are set to the third phase and the first gain, a comparison output power is measured based on the test result signals obtained from the second channel and the third channel after adjusting the phases and gains of the third channel while maintaining the phases and gains of the second channel, and the phases and gains of the third channel are set to have zero-degree phase error and zero-dB gain error based on a comparison result of the reference output power and the comparison output power. adjusting the phase and gain of the third channel while keeping the phase and gain of the second channel, measuring a comparison output power based on the test result signals obtained from the second and third channels, and based on a comparison result of the reference output power and the comparison output power, the phase and gain of the third channel are set to have zero degree phase error and zero dB gain error; wherein each of the plurality of channels comprises: a transmit path configured to be enabled in a transmit mode to output a transmit signal; and a receive path configured to be enabled in a receive mode to receive a receive signal. wherein the selection unit comprises: a plurality of power couplers connected to the plurality of channels, each of the plurality of power couplers being directly connected to a respective one of the plurality of channels and comprising a directional coupler; a plurality of first channel selection structures connected to the plurality of power couplers, each of the plurality of first channel selection structures being connected to two adjacent power couplers and comprising a switched Wilkinson combiner having one resistor and two switches; a plurality of second channel selection structures connected to the plurality of first channel selection structures, each of the plurality of second channel selection structures being connected to two adjacent first channel selection structures or two adjacent second channel selection structures and comprising a switched Wilkinson combiner having one resistor and two switches; and a transceive channel selector connected to one of the plurality of second channel selection structures, the transceive channel selector comprising a double-pole double-throw (DPDT) switch configured to receive a test signal generated from a signal processor or to provide the test result signal to the power detector.

2. The calibration circuit of claim 1, wherein, in the transmit mode: the test signal is a transmit signal, the transceive channel selector is configured to provide the transmit signal to the selected two channels, and the transceive channel selector is configured to receive the test result signal from the selected two channels through the power couplers, the first channel selection structures, and the second channel selection structures.

3. The calibration circuit of claim 1, wherein, in the receive mode: the test signal is a receive signal, the transceive channel selector is configured to provide the receive signal to the selected two channels through the second channel selection structures, the first channel selection structures, and the power couplers, and the transceive channel selector is configured to receive the test result signal from the selected two channels.

4. A multi-channel beamforming system, comprising: a plurality of channels; and a calibration circuit connected to the plurality of channels, the calibration circuit being configured to calibrate phases and gains among the plurality of channels, wherein each of the plurality of channels comprises: a transmit path configured to be enabled in a transmit mode to output a transmit signal; and a receive path configured to be enabled in a receive mode to receive a receive signal wherein the calibration circuit comprises: a plurality of power couplers connected to the plurality of channels, each of the plurality of power couplers being directly connected to a respective one of the plurality of channels and comprising a directional coupler; a plurality of first channel selection structures connected to the plurality of power couplers, each of the plurality of first channel selection structures being connected to two adjacent power couplers and comprising a switched Wilkinson combiner having one resistor and two switches; a plurality of second channel selection structures connected to the plurality of first channel selection structures, each of the plurality of second channel selection structures being connected to two adjacent first channel selection structures or two adjacent second channel selection structures and comprising a switched Wilkinson combiner having one resistor and two switches; and a transceive channel selector connected to one of the plurality of second channel selection structures, the transceive channel selector comprising a double-pole double-throw (DPDT) switch configured to receive a test signal generated from a signal processor or to provide the test result signal to the power detector. a selection unit connected to the plurality of channels, the selection unit configured to select two channels from the plurality of channels, to provide test signals to the selected two channels, and to receive test result signals from the selected two channels; a power detector comprising an envelope detector configuration configured to detect an envelope of the test result signals, the power detector configured to measure a power of the selected two channels according to a magnitude of the test result signals; an analog-to-digital converter configured to perform analog-to-digital conversion on an output of the power detector; and a calibrator configured to calibrate the phase and gain among the plurality of channels based on an output of the analog-to-digital converter, wherein the plurality of channels comprises a first channel to an Nth channel, where N is a natural number greater than or equal to three, the first channel is selected as a reference channel, a second channel to an Nth channel are sequentially selected as comparison channels, and the second channel to the Nth channel are sequentially set to have zero-degree phase error and zero-dB gain error at a first phase, from among the second channel to the Nth channel, the second channel is selected as a reference channel and the third channel is selected as a comparison channel, the third channel is set to have zero-degree phase error and zero-dB gain error at a second phase different from the first phase, and the third channel is selected as a reference channel, the first channel is selected as a comparison channel, and the first channel is set to have zero-degree phase error and zero-dB gain error at the first phase, wherein, when the second channel is set to have zero-degree phase error and zero-dB gain error at the first phase: a reference output power is measured based on the test result signals obtained from the first channel and the second channel when the phase and gain of the first channel are set to the second phase and a first gain and the phase and gain of the second channel are set to a third phase and the first gain, after adjusting the phase and gain of the second channel while keeping the phase and gain of the first channel, a comparison output power is measured based on the test result signals obtained from the first channel and the second channel, and based on a comparison result of the reference output power and the comparison output power, the phase and gain of the second channel are set to have zero-degree phase error and zero-dB gain error, wherein, when the third channel is set to have zero-degree phase error and zero-dB gain error: a reference output power is measured based on the test result signals obtained from the second channel and the third channel when the phase and gain of the second channel are set to the first phase and a first gain and the phase and gain of the third channel are set to the third phase and the first gain, after adjusting the phase and gain of the third channel while keeping the phase and gain of the second channel, a comparison output power is measured based on the test result signals obtained from the second channel and the third channel, and based on a comparison result of the reference output power and the comparison output power, the phase and gain of the third channel are set to have zero-degree phase error and zero-dB gain error, The selection unit includes: a plurality of power couplers connected to the plurality of channels, each of the plurality of power couplers connected to a respective one of the plurality of channels and including a directional coupler; a plurality of first channel selection structures connected to the plurality of power couplers, each of the plurality of first channel selection structures connected to two adjacent power couplers and including a switched Wilkinson combiner having one resistor and two switches; a plurality of second channel selection structures connected to the plurality of first channel selection structures, each of the plurality of second channel selection structures connected to two adjacent first channel selection structures or two adjacent second channel selection structures and including a switched Wilkinson combiner having one resistor and two switches; and a transceiver channel selector connected to one of the plurality of second channel selection structures, the transceiver channel selector including a double-pole double-throw (DPDT) switch configured to receive a test signal generated from a signal processor or provide the test result signal to the power detector.

Images