CN112737707A

CN112737707A - Transceiver using hybrid beamforming and performing antenna calibration method

Info

Publication number: CN112737707A
Application number: CN201911201923.2A
Authority: CN
Inventors: 何建兴; 方士豪; 许仁源; 陈家铭
Original assignee: Industrial Technology Research Institute ITRI
Current assignee: Industrial Technology Research Institute ITRI
Priority date: 2019-10-14
Filing date: 2019-11-29
Publication date: 2021-04-30
Anticipated expiration: 2039-11-29
Also published as: CN112737707B

Abstract

The present disclosure provides a transceiver in a communication system using hybrid beamforming and performing an antenna calibration method. In an exemplary embodiment according to the present disclosure, the transceiver may generate a plurality of scrambling sequences. The transceiver may include a plurality of coupling circuits to receive a feedback signal. The transceiver may recover a transmit signal output by an antenna assembly from the feedback signal using the plurality of scrambling sequences. Thus, the transmitter may perform antenna calibration for each antenna assembly.

Description

Transceiver using hybrid beamforming and performing antenna calibration method

Technical Field

The present invention relates to a transceiver using hybrid beamforming and performing an antenna calibration method.

Background

Fifth generation (5G) communication systems use massive Multiple Input Multiple Output (MIMO) techniques and beamforming. Massive MIMO technology uses an extremely high number of antennas. Massive MIMO technology provides increased data flow, small-scale fading cancellation (fading) and greater beamforming gain.

Fig. 1 shows an example of a massive MIMO system using beamforming. In fig. 1, a next Generation Node B (gNB) transmits signals to several User Equipments (UEs). The gbb includes an extremely high number of antennas. The antennas of the gNB are grouped into sub-arrays. In addition, the gNB transmits signals to the UE using beamforming. Similarly, the gNB receives signals from the UE through beams. The UE accesses the network through the gNB.

Fig. 2 shows an example of a transceiver for a massive MIMO system using all-digital beamforming. In that

In fig. 2, the transceiver inputs Ns baseband signals to the baseband precoding block FBB. The FBB outputs Lt precoded signals. The precoded signal is an input to an Lt digital-to-analog converter (DAC). The Lt outputs of the DAC are inputs to Lt Radio Frequency (RF) chains. The Lt outputs of the RF chain are transmitted through Nt antennas of the transceiver. Similar to fig. 1, the transceiver shown in fig. 2 also uses beamforming. The FBB performs precoding to transmit the precoded signals in different beams.

All-digital beamforming is limited by: space, signal processing complexity, and hardware complexity, including high power consumption.

Fig. 3 shows an example of a transceiver for a massive MIMO system using hybrid digital/analog beamforming. Hybrid beamforming performs precoding in the digital domain as well as in the analog domain. Similar to fig. 2, the transceiver inputs Ns baseband signals to the baseband precoding block FBB. The FBB performs precoding in the digital domain. The FBB outputs Lt precoded signals. The precoded signal is the input of Lt DACs. The Lt outputs of the DAC are inputs of Lt RF chains. However, unlike fig. 2, in fig. 3, Lt outputs of the RF chain are inputs of the RF pre-coding block FRF. FRF performs precoding in the analog domain. The FRF outputs Nt precoded signals, which are transmitted through Nt antennas of the transceiver.

Comparing fig. 2 to fig. 3, the number Ns of baseband signals is less than or equal to the number Lt of RF chains: ns is less than or equal to Lt. In fig. 2, the number of RF chains Lt is equal to the number of antennas Nt: lt equals Nt. However, in fig. 3, since hybrid beamforming has RF precoding, the number of RF chains Lt may be smaller than the number of antennas Nt: lt < Nt.

Fig. 4A, 4B, and 4C illustrate examples of transceivers using hybrid beamforming. In fig. 4A, 4B and 4C, the transceiver inputs Ns baseband signals to the digital precoder FB. FB outputs NR precoded signals. The precoded signals are the inputs to NR RF chains. The RF chain performs up-conversion and outputs a plurality of RF signals. The analog precoder FR performs analog precoding on the plurality of RF signals. After analog precoding, a plurality of Power Amplifiers (PAs) amplify the plurality of RF signals. Finally, after amplification, the antenna sub-arrays of the transceiver transmit the plurality of RF signals.

Fig. 4A shows a transceiver with a fully-connected structure, where each RF chain is connected to all antennas. In fig. 4A, a first RF signal of a first RF chain is connected to a first antenna, a second RF signal of the first RF chain is connected to a second antenna, and an Nt RF signal of the first RF chain is connected to an Nt antenna. Similarly, a first RF signal of an NR-th RF chain is connected to a first antenna, a second RF signal of the NR-th RF chain is connected to a second antenna, and an Nt-th RF signal of the NR-th RF chain is connected to an Nt-th antenna. In fig. 4A, each RF chain is connected to all antenna sub-arrays.

Fig. 4B shows a transceiver with a partially-connected structure (partially-connected structure) in which each sub-array is connected to only a single RF chain. In fig. 4B, a first RF signal of the first RF chain is connected to the first antenna of the first antenna sub-array, a second RF signal of the first RF chain is connected to the second antenna of the first antenna sub-array, and an nth RF signal of the first RF chain is connected to the nth antenna of the first antenna sub-array. Similarly, a first RF signal of the NR-th RF chain is connected to a first antenna of the NR-th antenna sub-array, a second RF signal of the NR-th RF chain is connected to a second antenna of the NR-th antenna sub-array, and an nth RF signal of the NR-th RF chain is connected to an nth antenna of the NR-th antenna sub-array.

Fig. 4C shows a transceiver with a hybrid-connected structure (hybrid-connected structure) in which each antenna sub-array is connected to multiple RF chains. In fig. 4C, each sub-array RF chain includes S RF chains. After analog precoding, each antenna of the antenna sub-array transmits RF signals from the S RF chains.

Fig. 5A and 5B illustrate another example of a transceiver using hybrid beamforming. In fig. 5A, the transceiver inputs Ns baseband signals to the digital precoder FB. FB outputs NR precoded signals. The precoded signal is the input to the NR DACs. After the precoded signals are converted to analog signals by the DAC, the RF chain performs up-conversion and outputs a plurality of RF signals. The analog precoder FR performs analog precoding on the plurality of RF signals. After analog precoding, a plurality of Power Amplifiers (PAs) amplify the plurality of RF signals. Finally, after amplification, the antenna sub-arrays of the transceiver transmit the plurality of RF signals. In addition, in fig. 5A, analog precoding is performed by analog weighting in which the RF signal is multiplied by a weighting factor.

FIG. 5B illustrates several of the components shown in FIG. 5A. The phase shifter is an analog electronic circuit that performs analog precoding. The input to the phase shifter is an analog signal and the phase shifter outputs the analog signal with a predetermined phase shift. The phase shifter may include a DAC to convert a digital control signal input by the digital circuit into an analog signal to control the phase shifter. A power amplifier is an analog electronic circuit that increases the power of an input analog signal. The antenna assembly is an antenna. A group of antenna elements may be connected together to form an antenna array. The antenna array may operate as a single antenna to transmit and receive radio waves.

Fig. 6A and 6B show examples of antennas of fourth generation (4G) communication systems and 5G communication systems. Fig. 6A and 6B illustrate a base station providing network access to several user terminals in a coverage area.

Fig. 6A shows an example of an antenna of the 4G communication system. In fig. 6A, an antenna provides network access to several user terminals. Some user terminals are outside the coverage area of the antenna and are not connected to the network.

Fig. 6B shows an example of an antenna array of a 5G communication system. In fig. 6B, the base station uses an Active Phased Array Antenna (APAA) and beamforming. Thus, the coverage area of a base station is divided into a plurality of beams. The user terminal accesses the network through one of the beams. Because the base station uses beamforming, the base station may direct the power of the signal towards the user and provide network access to the user even if the user is not near the base station.

Fig. 7 shows a block diagram of an ideal antenna calibration. The antenna calibration includes estimation and compensation. The transceiver may receive an input of a signal xn to be transmitted. The blocks hn group the channel effects caused by the transceiver hardware on the signal xn. First, the antenna calibrator estimates the channel effect hn. The antenna calibrator then performs compensation for channel effects by pre-filtering the input signal xn with a filter response (1/hn). After performing the estimation and compensation, the antenna transmits a signal xn. Compensation can be provided by pre-filtering the input signal xn in the time domain with a filter response (1/hn) or by multiplying the filter in the frequency domain with a frequency response (1/H), where H is the frequency response of hn.

Fig. 8A and 8B show examples of impulse responses caused by hardware damage and compensation by antenna calibration. In fig. 8A and 8B, the transceiver includes N antenna elements. The antenna calibration performs compensation for each antenna.

Fig. 8A shows an example of an impulse response with only one pulse. In fig. 8A, the impulse response at antenna assembly #1 is one pulse h 1. The impulse response at antenna assembly #2 is one pulse h 2. The impulse response at antenna element # N is one pulse hN. In an ideal calibration, there is no error in the estimation, and the calibrator performs compensation by multiplying the signal to be transmitted by the inverse of the impulse response. Thus, after compensation, the impulse response at antenna element #1, antenna element #2, and antenna element # N has one impulse with a value of 1.

Fig. 8B shows an example of an impulse response with several pulses. In fig. 8B, the impulse response at antenna assembly #1 has pulses h11, h12, h13, …, h1 p. The impulse response at antenna assembly #2 has pulses h21, h22, h23, …, h2 p. The impulse response at antenna assembly # N has pulses hN1, hN2, hN3, …, hNp. In an ideal calibration, there is no error in the estimation. The calibrator performs the compensation using an Infinite Impulse Response (IIR) filter, wherein a frequency response of the IIR filter is an inverse of a frequency response at a corresponding antenna assembly. Thus, after compensation, the impulse response at antenna element #1, antenna element #2, and antenna element # N has one impulse with a value of 1.

Due to the above benefits, how to achieve antenna calibration in a hybrid beamforming system becomes one of the requirements. However, antenna calibration in massive MIMO systems also presents particular challenges.

Disclosure of Invention

Accordingly, to address the difficulties of the known art, the present invention provides a transceiver in a communication system using hybrid beamforming and configured to perform antenna calibration. The transceiver may generate a plurality of orthogonal scrambling sequences. The transceiver may recover the transmit signals of the antenna assemblies from the feedback signals using the plurality of orthogonal scrambling sequences. Thus, the transceiver may perform calibration for each antenna assembly.

In one aspect, the present invention relates to a transceiver in a communication system using hybrid beamforming, configured to perform an antenna calibration method, the transceiver comprising: a processor outputting a plurality of digital precoded signals; a plurality of digital-to-analog converters (DACs) coupled to the processor, receiving the plurality of digital pre-coded signals, and outputting a plurality of analog baseband signals; a plurality of Radio Frequency (RF) chains coupled to the plurality of DACs, receiving the plurality of analog baseband signals, performing up-conversion, and outputting a plurality of RF signals; a plurality of phase shifters that receive the plurality of RF signals from the plurality of RF chains, perform phase shifting on the plurality of RF signals according to a plurality of orthogonal scrambling sequences, and output a plurality of phase-shifted RF signals; a plurality of power amplifiers receiving the plurality of phase-shifted RF signals from the plurality of phase shifters, amplifying the plurality of phase-shifted RF signals, and outputting a plurality of transmit signals; a plurality of antenna assemblies coupled to the plurality of power amplifiers, receiving the plurality of transmit signals, and transmitting the plurality of transmit signals; a plurality of coupling circuits coupled to the plurality of antenna assemblies, receiving the plurality of transmit signals, combining the plurality of transmit signals, and outputting a feedback signal; a feedback network coupled to the plurality of coupling circuits to receive the feedback signal; and an Observation Receiver (ORX) coupled to the feedback network, receiving the feedback signal, performing a frequency down conversion on the feedback signal, and converting the feedback signal into a digital feedback signal, wherein the processor is configured to execute a plurality of modules, the plurality of modules including: a digital precoder that performs precoding on a plurality of digital signals and outputs the plurality of digital precoded signals; a plurality of calibration compensation modules that perform calibration compensation on the plurality of digital precoded signals to compensate for phase, gain, and delay excess amounts in the plurality of transmit signals, the phase, gain, and delay excess amounts caused by the plurality of DACs, the plurality of RF chains, the plurality of phase shifters, and the plurality of power amplifiers; and a calibrator that receives the digital feedback signal, transmits a plurality of calibration sequences to the plurality of calibration compensation modules, and transmits the plurality of orthogonal scrambling sequences to the plurality of phase shifters, wherein the plurality of phase shifters perform phase shifting on the plurality of RF signals according to the plurality of orthogonal scrambling sequences, wherein the calibrator receives the digital feedback signal when the processor outputs the plurality of calibration sequences to the plurality of DACs, the calibrator compares the digital feedback signal with the plurality of calibration sequences and the plurality of orthogonal scrambling sequences to determine the phase, gain, and delay overages and adjust the calibration compensation performed by the plurality of calibration compensation modules.

In order that the aforementioned features and advantages of the invention will be readily understood, exemplary embodiments are described in detail below with reference to the accompanying drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the disclosure as claimed.

It should be understood, however, that this summary may not include all aspects and embodiments of the disclosure, and is therefore in no way intended to be limiting or restrictive. Further, the present invention will include improvements and modifications apparent to those skilled in the art.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

Fig. 1 shows an example of a massive MIMO system using beamforming.

Fig. 2 shows an example of a transceiver for a massive MIMO system using all-digital beamforming.

Fig. 3 shows an example of a transceiver for a massive MIMO system using hybrid digital/analog beamforming.

Fig. 4A, 4B, and 4C illustrate examples of transceivers using hybrid beamforming.

Fig. 5A and 5B illustrate another example of a transceiver using hybrid beamforming.

Fig. 6A and 6B show examples of antennas of the 4G communication system and the 5G communication system.

Fig. 7 shows a block diagram of an ideal antenna calibration.

Fig. 8A and 8B show examples of impulse responses caused by hardware damage and compensation by antenna calibration.

Fig. 9 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention.

Fig. 10 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention.

Fig. 11 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention.

Fig. 12 shows a calibration sequence according to an exemplary embodiment of the present invention.

Fig. 13 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention.

Fig. 14 illustrates phase, gain, and delay excess amounts caused by multiple DACs, multiple RF chains, multiple phase shifters, and multiple power amplifiers according to several embodiments of the invention.

Fig. 15 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention.

Fig. 16 illustrates a plurality of tunable analog filters of a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention.

Fig. 17 illustrates a plurality of tunable analog filters of a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention.

List of reference numerals

ADC: analog/digital converter

APAA: active phased array antenna

c: gain and phase

Orthogonal scrambling sequences

CP1, CP 2: cyclic prefix

DAC: digital/analog converter

FB: digital pre-encoder

FBB: fundamental frequency pre-coding block

FR: analog precoder

FRF: radio Frequency (RF) precoding block

And g NB: next generation node B

h: common broadband channel response

Residual response

Broadband channel response

h1, h2, …, hN, h11, h12, h13, …, h1p, h21, h22, h23, …, h2p, hN1, hN2, hN3, …, hNp: pulse of light

hn: channel effect

1/hn: filter response

N, NR, Ns, Nt, Lt, S: number of

PA: power amplifier

RF: radio frequency

(ii) SEQ: calibration signal

Tx: conveyor

UE: user equipment

xn: signal

Compensation

Delay

Detailed Description

Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts.

To address the difficulties of the known art, the present disclosure provides a transceiver that uses hybrid beamforming and performs an antenna calibration method. For example, since a massive MIMO system includes a very high number of antenna elements, and each antenna element requires a feedback circuit. Since the number of antenna components is extremely high, it is desirable to perform antenna calibration on a feedback signal combining transmission signals of several antenna components. In antenna calibration of conventional systems, however, the combined feedback signal is not required because the number of antenna elements is not high.

Thus, the present invention relates to a transceiver with a number of antenna arrays using hybrid beamforming and antenna calibration. The transceiver of the present invention may include a single feedback circuit that may combine the transmit signals of the antenna components into one feedback signal. Since the calibration method uses orthogonal scrambling sequences, the calibrator can recover the transmission signal of the antenna assembly. Therefore, the transceiver of the present invention can perform antenna calibration and reduce the hardware complexity of the feedback circuit.

Fig. 9 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention. In fig. 9, the transceiver may include: a digital precoder FB; a plurality of calibration compensation modules; a plurality of digital-to-analog converters (DACs); a plurality of Radio Frequency (RF) chains; a plurality of phase shifters; a plurality of Power Amplifiers (PAs); a plurality of antenna assemblies; a plurality of coupling circuits; feedback network (FB NW); an Observation Receiver (ORX); and a calibrator.

The digital precoder FB may receive a plurality of (Ns) digital signals, perform precoding on the plurality of digital signals, and output a plurality of digital precoded signals. The plurality of calibration compensation modules may perform calibration compensation on the plurality of digital precoded signals. The plurality of DACs may receive the plurality of digital precoded signals and output a plurality of analog baseband signals. The plurality of RF chains may receive the plurality of analog baseband signals, perform up-conversion, and output a plurality of RF signals. The plurality of phase shifters may receive the plurality of RF signals from the plurality of RF chains, perform phase shifting on the plurality of RF signals, and output a plurality of phase-shifted RF signals. The plurality of PAs may receive the plurality of phase-shifted RF signals from the plurality of phase shifters, amplify the plurality of phase-shifted RF signals, and output a plurality of transmit signals. The plurality of antenna assemblies coupled to the plurality of power amplifiers may receive the plurality of transmit signals and transmit the plurality of transmit signals.

The plurality of coupling circuits coupled to the plurality of antenna assemblies may receive the plurality of transmit signals from the plurality of antenna arrays, combine the plurality of transmit signals, and output a feedback signal. The FB NW coupled to the plurality of coupling circuits may receive the feedback signal. An ORX coupled to the FB NW may receive the feedback signal, perform down conversion on the feedback signal, and convert the feedback signal to a digital feedback signal.

The calibrator may receive the digital feedback signal output by the ORX. The calibrator may also send a plurality of calibration sequences to the plurality of calibration compensation modules.

The calibrator may further send a plurality of orthogonal scrambling sequences c to the plurality of phase shifters. The plurality of phase shifters may perform phase shifting on the plurality of RF signals according to the plurality of orthogonal scrambling sequences c. The phase shifting according to the plurality of orthogonal scrambling sequences c may enable the calibrator to perform calibration for each antenna component of the plurality of antenna components while receiving only a single digital feedback signal.

As previously described, the plurality of calibration compensation modules may perform calibration compensation on the plurality of digital precoded signals. Calibration compensation may be performed to remove phase, gain and delay overages. These phase, gain and delay overages are added to the transmit signal at the antenna elements. The plurality of DACs, the plurality of RF chains, the plurality of phase shifters, and the plurality of power amplifiers cause these phase, gain, and delay overages. Phase, gain and delay overages may be determined for each antenna element.

To determine the phase, gain and delay overages, the calibrator may use the plurality of calibration sequences. The plurality of calibration sequences may be input into the plurality of DACs, a calibrator may receive a digital feedback signal and may compare the calibration sequences to the received digital feedback signal to determine phase, gain, and delay overages.

Thus, the plurality of calibration sequences may be input into the plurality of DACs, a calibrator may receive a digital feedback signal, and the calibrator may compare the digital feedback signal to the plurality of calibration sequences and the plurality of orthogonal scrambling sequences c to determine phase, gain, and delay overages and adjust calibration compensation performed by the plurality of calibration compensation modules.

Further, the plurality of coupling circuits may be a plurality of analog electronic circuits coupled to the antenna assembly. For example, the coupling circuit may be analog electronic circuitry that may sum signals transmitted by the antenna elements to provide a feedback signal. In addition, several antenna elements may be grouped to form an antenna array to transmit and receive either omni-directional antenna beams or directional antenna beams.

Further, the plurality of DACs and the plurality of PAs may be electronic circuits well known to those skilled in the art. The plurality of RF chains may be analog electronic circuits that convert analog signals to RF signals. For example, the RF chain may include mixers, local oscillators, analog filters, and power amplifiers for up-conversion and down-conversion. Similarly, the ORX may be an electronic circuit that converts an analog RF signal to a digital feedback signal. For example, the ORX may include a mixer for down conversion, a local oscillator, an analog filter, a power amplifier, and a DAC.

Fig. 10 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention. In fig. 10, the transceiver may include: a hardware processor, a non-transitory storage medium, a plurality of DACs, a plurality of RF chains, a plurality of phase shifters, a plurality of PAs, a plurality of antenna elements, a plurality of coupling circuits, FB NW, and ORX.

The plurality of DACs, the plurality of RF chains, the plurality of phase shifters, the plurality of PAs, the plurality of antenna elements, the plurality of coupling circuits, FB NW, and ORX are similar to those in fig. 9. A description of these components can be found in the description of fig. 9.

Fig. 10 differs from fig. 9 in that the transceiver shown in fig. 10 includes a hardware processor and a non-transitory storage medium. The hardware processor is electrically connected to the non-transitory storage medium and is at least configured to execute the plurality of modules of the transceiver according to the exemplary embodiments and alternative variations. The hardware processor may be configured to execute at least the digital precoder FB, the plurality of calibration compensation modules, and the calibrator. A description of these modules and components executed by a hardware processor may be found in the description of fig. 9.

Furthermore, the hardware processor is configured to process the digital signal and execute at least the plurality of modules of the transceiver according to the exemplary embodiments presented in the present invention. Further, the hardware processor may access a non-transitory storage medium that stores programming code, a codebook configuration, buffered data, and a record layout assigned by the hardware processor. A hardware processor may be implemented using programmable units such as microprocessors, microcontrollers, Digital Signal Processor (DSP) chips, Field Programmable Gate Arrays (FPGAs), and the like. The functions of the hardware processor may also be implemented using a separate electronic device or Integrated Circuit (IC). It should be noted that the functionality of a hardware processor may be implemented using hardware or software.

Accordingly, fig. 9 and 10 jointly illustrate a transceiver in a communication system using hybrid beamforming configured to perform an antenna calibration method, the transceiver comprising: a processor outputting a plurality of digital precoded signals; a plurality of digital-to-analog converters (DACs) coupled to the processor that receive the plurality of digital pre-encoded signals and output a plurality of analog baseband signals; a plurality of Radio Frequency (RF) chains coupled to the plurality of DACs, receiving the plurality of analog baseband signals, performing up-conversion, and outputting a plurality of RF signals; a plurality of phase shifters that receive the plurality of RF signals from the plurality of RF chains, perform phase shifting on the plurality of RF signals according to a plurality of orthogonal scrambling sequences, and output a plurality of phase-shifted RF signals; a plurality of power amplifiers receiving the plurality of phase-shifted RF signals from the plurality of phase shifters, amplifying the plurality of phase-shifted RF signals, and outputting a plurality of transmit signals; a plurality of antenna assemblies coupled to the plurality of power amplifiers, receiving the plurality of transmit signals, and transmitting the plurality of transmit signals; a plurality of coupling circuits coupled to the plurality of antenna assemblies, receiving the plurality of transmit signals, combining the plurality of transmit signals, and outputting a feedback signal; a feedback network coupled to the plurality of coupling circuits to receive a feedback signal; and an Observation Receiver (ORX) coupled to the feedback network, receiving the feedback signal, performing a frequency down-conversion on the feedback signal, and converting the feedback signal to a digital feedback signal, wherein the processor is configured to execute a plurality of modules, the plurality of modules comprising: a digital precoder that performs precoding on a plurality of digital signals and outputs the plurality of digital precoded signals; a plurality of calibration compensation modules that perform calibration compensation on the plurality of digital precoded signals to compensate for phase, gain, and delay excess amounts in the plurality of transmit signals, the phase, gain, and delay excess amounts caused by the plurality of DACs, the plurality of RF chains, the plurality of phase shifters, and the plurality of power amplifiers; and a calibrator that receives the digital feedback signal, transmits a plurality of calibration sequences to the plurality of calibration compensation modules, and transmits a plurality of orthogonal scrambling sequences to the plurality of phase shifters, wherein the plurality of phase shifters perform phase shifting on the plurality of RF signals according to the plurality of orthogonal scrambling sequences, wherein when the processor outputs the plurality of calibration sequences to the plurality of DACs, the calibrator receives the digital feedback signal, compares the digital feedback signal with the plurality of calibration sequences and the plurality of orthogonal scrambling sequences to determine phase, gain, and delay overages and adjust the calibration compensation performed by the plurality of calibration compensation modules.

According to an exemplary embodiment of the present invention, the calibrator shown in fig. 9 may be a baseband unit (BBU). The BBU can be a device that includes a processor that processes the baseband signals.

According to an exemplary embodiment of the present invention, the calibrator shown in fig. 9 may be a Remote Radio Head (RRH). The RRHs may be electronic devices that include analog filters, amplifiers, DACs, analog-to-digital converters (ADCs), and mixers for up-conversion and down-conversion.

Thus, according to an exemplary embodiment of the invention, the calibrator is located in the Base Band Unit (BBU) or the Remote Radio Head (RRH).

According to an exemplary embodiment of the present invention, the plurality of orthogonal scrambling sequences c may be a plurality of Hadamard (Hadamard) sequences or a plurality of Walsh (Walsh) sequences. The plurality of hadamard sequences or the plurality of walsh sequences and the plurality of calibration sequences may form a code division calibration signal. The plurality of hadamard sequences or the plurality of walsh sequences may allow the calibrator to recover the plurality of calibration sequences from the feedback signal. Thus, in this embodiment, the plurality of scrambling sequences are a plurality of hadamard or walsh sequences. In addition, the plurality of scrambling sequences may be designed according to the plurality of calibration sequences so as not to affect the calibration estimation results of the plurality of calibration sequences.

The transceiver shown in fig. 9 may be further coupled to an external baseband processing unit, according to an exemplary embodiment of the present invention. The external baseband processing unit may be a device comprising a processor that processes the baseband signal. The external baseband processing unit may generate the plurality of calibration sequences. Thus, in this embodiment, an external baseband processing unit is coupled to the transceiver and configured to generate the plurality of calibration sequences. In another embodiment of the present invention, an external baseband processing unit is coupled to the transceiver and configured to estimate phase, gain, and delay excess. Additionally, in another embodiment of the present invention, an external baseband processing unit is coupled to the transceiver and configured to generate the plurality of calibration sequences and estimate phase, gain, and delay overages.

Fig. 11 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention. Fig. 11 is similar to fig. 9 and 10. The difference is that in fig. 11, the transceiver may further include a coupling antenna coupled to the FB NW instead of the plurality of coupling circuits. The coupled antenna may provide over-the-air (OTA) coupling between the plurality of antenna elements and a coupled antenna coupled to the FB NW.

The digital precoder FB, the plurality of calibration compensation modules, the plurality of DACs, the plurality of RF chains, the plurality of phase shifters, the plurality of PAs, the plurality of antenna assemblies, FB NW, ORX, and the calibrator are similar to those in fig. 9. A description of these components can be found in the description of fig. 9.

Fig. 12 illustrates an orthogonal scrambling sequence and a calibration sequence according to an exemplary embodiment of the present invention. The orthogonal scrambling sequence may be periodic with a certain period. The time interval corresponding to the period of the orthogonal sequence may include a plurality of calibration sequences.

The calibration sequence may include cyclic prefixes CP1 and CP2 and a calibration signal SEQ. CP1 and CP2 may be added at the beginning and end of the calibration sequence. CP1 may allow the calibrator to perform a synchronization procedure and locate the beginning of a calibration sequence. The length of CP1 may be greater than the maximum delay spread of the overall channel response. CP2 may allow the calibrator to perform common channel response estimation and determine phase, gain, and delay excess. Fig. 14 and the corresponding paragraphs of this specification describe common channel responses. As described previously with respect to fig. 9 and 10, the plurality of calibration sequences may be input to the plurality of DACs to determine phase, gain, and delay overages and adjust calibration compensation. A first DAC of the plurality of DACs may receive a first calibration sequence. A second DAC of the plurality of DACs may receive a second calibration sequence. In this case and referring to fig. 12, SEQ of the first calibration sequence and SEQ of the second calibration sequence may be different calibration signals.

As described previously with respect to fig. 9 and 10, the plurality of orthogonal scrambling sequences may be input to the plurality of phase shifters, wherein the plurality of phase shifters perform phase shifting on the plurality of RF signals. A first phase shifter of the plurality of phase shifters may receive a first orthogonal scrambling sequence. A second phase shifter of the plurality of phase shifters may receive a second orthogonal scrambling sequence. In this case, the first and second orthogonal scrambling sequences may be different. Thus, the calibrator may determine the phase, gain, and delay excess by comparing the digital feedback signal to the plurality of calibration sequences and the plurality of orthogonal scrambling sequences.

As described previously with respect to fig. 9 and 10, the phase shifter may perform phase shifting according to an orthogonal scrambling code. Referring to fig. 12, the phase shifter may receive inputs of a plurality of calibration sequences, wherein each calibration sequence includes the same CP1, CP2, and SEQ. In other words, all calibration sequences input into the phase shifter are the same in a time interval corresponding to the period of the orthogonal scrambling code. The phase shifter may perform a phase shift on a first calibration sequence of a period of the orthogonal scrambling code according to a first coefficient of the orthogonal scrambling code. The phase shifter may perform a phase shift on a second calibration sequence of the period of the orthogonal scrambling code according to a second coefficient of the orthogonal scrambling code. The phase shifter may continue to perform phase shifting on the calibration sequence in a similar manner. Finally, the phase shifter may perform a phase shift on a last calibration sequence of a period of the orthogonal scrambling code according to a last coefficient of the orthogonal scrambling code.

Fig. 13 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention. Unlike fig. 9, fig. 13 shows a transceiver with a receive calibration architecture. The transceiver may include: a plurality of antenna assemblies; a plurality of coupling circuits; a plurality of phase shifters; a plurality (NR) of RF chains; a plurality of analog/digital converters (ADCs); a calibrator; observation Transmitters (OTX); and a transmitter network (TX NW).

A first calibration sequence of the plurality of calibration sequences may correspond to a first RF chain of the plurality (NR) of RF chains. A second calibration sequence of the plurality of calibration sequences may correspond to a second RF chain of the plurality (NR) of RF chains. The plurality of orthogonal scrambling sequences are divided into NR sets of orthogonal scrambling sequences. A first of the sets of orthogonal scrambling sequences may correspond to a phase shifter coupled to a first RF chain. A second set of the sets of orthogonal scrambling sequences may correspond to a phase shifter coupled to a second RF chain.

The calibrator may perform multiplication of the plurality of calibration sequences with the plurality of orthogonal scrambling sequences and add the products together. Thus, the calibrator may multiply the first calibration sequence with each of the orthogonal scrambling sequences of the first set. The calibrator may multiply the second calibration sequence with each of the orthogonal scrambling sequences. After performing the multiplication on all calibration sequences and the orthogonal scrambling sequences, the calibrator may add the products together and input the result into the OTX.

OTX may perform up-conversion on the results input by the calibrator. The OTX may output an RF signal to the TX NW. The TX NW may input the RF signal to the plurality of coupling circuits. OTX may be an electronic circuit that converts digital signals to analog RF signals. For example, OTX may include a mixer, a local oscillator, and an ADC for up-conversion.

The plurality of coupling circuits may receive an RF signal from a TX NW and input the RF signal to the plurality of phase shifters. The plurality of phase shifters may perform phase shifting on the plurality of RF signals according to the plurality of orthogonal scrambling sequences. A phase shifter coupled to a first RF chain of the plurality of RF chains performs a phase shift according to a first set of the sets of orthogonal scrambling sequences. A phase shifter coupled to a second RF chain of the plurality of RF chains performs a phase shift according to a second set of the sets of orthogonal scrambling sequences.

The plurality of RF chains may receive phase-shifted RF signals from the plurality of phase shifters. Since any one of the plurality of RF chains may receive several phase-shifted RF signals, the plurality of RF chains may combine the received phase-shifted RF signals to output a plurality of combined signals. For example, the plurality of RF chains may use Maximum Ratio Combining (MRC) to obtain the plurality of combined signals. The plurality of ADCs may convert the plurality of combined signals into a plurality of digital signals. The plurality of digital signals may have phase, gain, and delay overages. A calibrator may receive the plurality of digital signals, compare the plurality of digital signals to the plurality of calibration sequences to determine phase, gain, and delay overages, and adjust calibration compensation.

Fig. 14 illustrates phase, gain, and delay excess amounts caused by multiple DACs, multiple RF chains, multiple phase shifters, and multiple power amplifiers according to several embodiments of the invention. The digital pre-coded signal may be input into the DAC shown in fig. 14. After the DAC performs digital/analog conversion and the RF chain performs up-conversion, the RF signal may be input into a plurality of phase shifters. The plurality of phase shifters may be coupled to a plurality of PAs. After amplification, the plurality of antenna elements may transmit a plurality of transmit signals. However, these components may cause phase, gain, and delay overruns in the multiple transmit signals. The plurality of calibration compensation modules may perform calibration compensation on the plurality of digital precoded signals to compensate for phase, gain, and delay excess in the plurality of transmit signals.

Any calibration compensation module can compensate for the excess caused by the DAC, the RF chain, and the phase shifter and PA coupled to the respective RF chain. The RF chain may be coupled to several phase shifters. Therefore, the phase, gain, and delay excess caused by the line formed by the phase shifter and the PA are different from the phase, gain, and delay excess caused by another line formed by the phase shifter and the PA. However, the line formed by the phase shifter and PA and another line formed by the phase shifter and PA may be coupled to the same RF chain, and thus have a common component with an excess of phase, gain, and delay. The common wideband channel response h may include phase, gain and delay excess caused by the DAC and RF chain. The gain and phase of the line formed by the phase shifter and PA is c. In summary, the phase, gain and delay excess at any antenna element is the product of h and c, which is referred to as the wideband channel response

In an exemplary embodiment of the invention, the calibrator of the transceiver shown in fig. 9 may adjust the calibration compensation to compensate for the common wideband channel response. Thus, in this embodiment, the common wideband channel response is the phase, gain and delay excess caused by the multiple DACs and RF chains, and the calibrator adjusts the calibration compensation to compensate for the common wideband channel response.

Fig. 15 illustrates a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention. Fig. 15 is similar to fig. 9 and 10. Except that in fig. 15, the transceiver may further include a plurality of delay circuits coupled to the plurality of phase shifters. The calibrator may adjust the delay for each path formed by the phase shifter and the PA

Wherein the delay adjusted for a line formed by a phase shifter and a PA may be different from the delay adjusted for another line formed by a phase shifter and a PA. In addition, the calibrator may determine a plurality of orthogonal scrambling sequences c, a plurality of delays, using the following equation

And compensation

To

The digital precoder FB, the plurality of calibration compensation modules, the plurality of DACs, the plurality of RF chains, the plurality of phase shifters, the plurality of PAs, the plurality of antenna assemblies, FB NW, ORX, and the calibrator are similar to those in fig. 9. A description of these components can be found in the description of fig. 9. The plurality of calibration compensation modules may provide compensation through digital filters

To

Fig. 16 illustrates a plurality of tunable analog filters of a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention. FIG. 16 shows a plurality of tunable analog filters and a plurality of delay circuits. The plurality of tunable analog filters may be coupled to the transceiver of fig. 15 between the plurality of RF chains and the plurality of delay circuits. The calibrator may further adjust the plurality of tunable analog filters to compensate for a residual response

Similar to fig. 15, the calibrator may also adjust the delay for each line formed by the phase shifter and PA

In addition, the calibrator may determine a plurality of orthogonal scrambling sequences c, a plurality of delays, using the following equation

Compensation

To

And residual response

Fig. 17 illustrates a plurality of tunable analog filters of a transceiver in a communication system configured to perform an antenna calibration method using hybrid beamforming according to an exemplary embodiment of the present invention. Figure 17 shows a plurality of tunable analog filters. The plurality of tunable analog filters may be coupled to the transceiver of fig. 9 between the plurality of RF chains and the plurality of phase shifters. Similar to fig. 16, the calibrator may further adjust the plurality of tunable analog filters to compensate for a residual response

Compensation

To

And residual response

In an exemplary embodiment of the invention, the calibrator of the transceiver of fig. 17 may adjust the plurality of tunable analog filters to provide calibration compensation for phase, gain, and delay excess caused by the plurality of phase shifters and the plurality of PAs. Thus, in this embodiment, the common wideband channel response is an excess amount of phase, gain, and delay caused by the plurality of DACs and RF chains, and the calibrator adjusts the calibration compensation of the plurality of calibration compensation modules to compensate for the common wideband channel response, wherein the calibrator adjusts the plurality of tunable analog filters to provide calibration compensation for the excess amount of phase, gain, and delay caused by the plurality of phase shifters and the plurality of power amplifiers.

In view of the above, the present invention is applicable to transceivers with a high number of antenna elements using hybrid beamforming. In a transceiver with many antenna elements, each antenna element would require a feedback network. Such requirements will result in increased hardware complexity. The transceiver of the present invention may include a single feedback network that may combine the transmit signals at the antenna assemblies into one feedback signal. Since the plurality of phase shifters perform phase shifting on the RF signal according to the plurality of orthogonal scrambling sequences, the calibrator can recover the transmission signal output by the antenna assembly. Therefore, the transceiver of the present invention can perform calibration to remove the phase, gain and delay excess caused by the RF components and reduce the hardware complexity of the feedback network.

No element, act, or instruction used in the detailed description of the embodiments disclosed herein should be construed as critical or essential to the invention unless explicitly described as such. In addition, each indefinite article "a" or "an" as used herein may encompass more than one item. If only one item is expected, the term "single" or similar language will be used. Furthermore, any of the term "… followed by a list of items and/or categories of items" as used herein is intended to include any of the items and/or categories of items "any combination of," any plurality of, "and/or any combination of multiple of," either alone or in combination with other items and/or other categories of items. Furthermore, the term "set" as used herein is intended to include any number of items, including zero. Further, the term "number" as used herein is intended to include any number, including zero.

Various equivalent modifications and changes in the structure of the disclosed embodiments can be made by those skilled in the art without departing from the scope or spirit of the invention. In view of the disclosure, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

Claims

1. A transceiver in a communication system using hybrid beamforming, configured to perform an antenna calibration method, the transceiver comprising:

a processor outputting a plurality of digital precoded signals;

a plurality of digital/analog converters coupled to the processor, receiving the plurality of digital pre-coded signals, and outputting a plurality of analog baseband signals;

a plurality of radio frequency chains coupled to the plurality of digital/analog converters, receiving the plurality of analog baseband signals, performing up-conversion, and outputting a plurality of radio frequency signals;

a plurality of phase shifters to receive the plurality of radio frequency signals from the plurality of radio frequency chains, perform phase shifting on the plurality of radio frequency signals according to a plurality of orthogonal scrambling sequences, and output a plurality of phase-shifted radio frequency signals;

a plurality of power amplifiers that receive the plurality of phase-shifted radio frequency signals from the plurality of phase shifters, amplify the plurality of phase-shifted radio frequency signals, and output a plurality of transmit signals;

a plurality of antenna assemblies coupled to the plurality of power amplifiers, receiving the plurality of transmit signals, and transmitting the plurality of transmit signals;

a plurality of coupling circuits coupled to the plurality of antenna assemblies, receiving the plurality of transmit signals, combining the plurality of transmit signals, and outputting a feedback signal;

a feedback network coupled to the plurality of coupling circuits to receive the feedback signal; and

an observation receiver coupled to the feedback network, receiving the feedback signal, performing a frequency down-conversion on the feedback signal, and converting the feedback signal to a digital feedback signal,

wherein the processor is configured to execute a plurality of modules comprising:

a digital precoder that performs precoding on a plurality of digital signals and outputs the plurality of digital precoded signals;

a plurality of calibration compensation modules that perform calibration compensation on the plurality of digital precoded signals to compensate for phase, gain, and delay excess in the plurality of transmit signals; and

a calibrator that receives the digital feedback signal, transmits a plurality of calibration sequences to the plurality of calibration compensation modules, and transmits the plurality of orthogonal scrambling sequences to the plurality of phase shifters to perform phase shifting on the plurality of radio frequency signals,

wherein the calibrator receives the digital feedback signal when the processor outputs the plurality of calibration sequences to the plurality of digital-to-analog converters, the calibrator compares the digital feedback signal to the plurality of calibration sequences and the plurality of orthogonal scrambling sequences to determine the phase, gain, and delay overages and to adjust the calibration compensation performed by the plurality of calibration compensation modules.

2. The transceiver of claim 1, wherein the calibrator is a baseband unit or a remote radio head.

3. The transceiver of claim 1, wherein the plurality of scrambling sequences are hadamard or walsh sequences.

4. The transceiver of claim 1, wherein an external baseband processing unit is coupled to the transceiver and configured to generate the plurality of calibration sequences.

5. The transceiver as recited in claim 1, wherein an external baseband processing unit is coupled to the transceiver and configured to estimate the phase, gain and delay excess.

6. The transceiver of claim 4, wherein the external baseband processing unit is further configured to estimate the phase, gain, and delay excess.

7. The transceiver of claim 1, wherein a common wideband channel response is a phase, gain and delay excess caused by the plurality of digital-to-analog converters and the plurality of radio frequency chains, and the calibrator adjusts the calibration compensation to compensate for the common wideband channel response.

8. The transceiver of claim 1, wherein the transceiver further comprises:

a plurality of tunable analog filters receiving the plurality of radio frequency signals from the plurality of radio frequency chains and coupled to the plurality of phase shifters,

wherein a common wideband channel response is a phase, gain, and delay excess caused by the plurality of digital-to-analog converters and the plurality of radio frequency chains, and the calibrator adjusts the calibration compensation of the plurality of calibration compensation modules to compensate for the common wideband channel response,

wherein the calibrator adjusts the plurality of tunable analog filters to provide calibration compensation for phase, gain, and delay excess caused by the plurality of phase shifters and the plurality of power amplifiers.