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Loopback technique for IQ imbalance estimation for calibration in OFDM systems

一种平衡、复用信号的技术，应用在正交频分复用系统,无线OFDM系统领域，能够解决增加模拟设计复杂性、ADC设计复杂性和功率消耗多等问题

Inactive Publication Date: 2015-04-29
ST ERICSSON SA
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  • Abstract
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Problems solved by technology

This implies that the ADC design is more complex and consumes more power
[0016] ● It significantly increases the complexity of the analog design because it requires the implementation of an RF envelope detector which must be self-testable before being used for IQ imbalance estimation and calibration

Method used

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  • Loopback technique for IQ imbalance estimation for calibration in OFDM systems
  • Loopback technique for IQ imbalance estimation for calibration in OFDM systems
  • Loopback technique for IQ imbalance estimation for calibration in OFDM systems

Examples

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Embodiment Construction

[0043] figure 1 Shows the relationship between EVM and image carrier suppression rate in an example of a 54-Mbps 802.11a based implementation. The figure shows the measured EVM of an "ideal" transmitter as a function of its image carrier suppression. The reduction in EVM at low signal levels is due to the limitations of the VSA (Vector Signal Analyzer) at low power levels. Dashed lines represent extrapolated values ​​for ideal VSA. Only preamble based channel estimation is used for VSA for mapping.

[0044]In this example, it clearly appears that in order to meet the EVM requirement of a 54-Mbps 802.11a signal (EVM = -25dB), the image carrier suppression of the system must exceed about -29dBc.

[0045] exist figure 2 , it can be seen that in order to achieve this image carrier suppression, a 5% magnitude error and a 2% phase error can be tolerated.

[0046] It should also be noted that in this example it is assumed that there are no other faults in the system. In realit...

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Abstract

A transceiver for orthogonal frequency division multiplex communication has a transmitter module (1) and a receiver module (2). The transmitter (1) has an I-path (3) and a Q-path (4) to receive signals on a number of subcarriers provided by a signal generator (9). The receiver module (2) has a receiver I-path (7) and a receiver Q-path (8) to deliver signals to a processor (15). IQ imbalance is calculated for each of the transmitter and receiver by the signal generator sending a sample signal (XI(k), XQ(k)) over a one of the transmitter paths. The signal is then applied to one or each of the inputs to the receiver paths (7,8) to generate receiver output signals YI(k), YQ(k), RQ(k). The processor (15) is responsive to the output signals to calculate the transmitter and receiver IQ imbalance for that subcarrier. A calibrator (19) and compensator (20) are responsive to the calculated IQ imbalance to correct or compensate each subcarrier of the transceiver band.

Description

technical field [0001] The present invention relates to the field of multi-carrier communication systems, in particular to Orthogonal Frequency Division Multiplexing (OFDM) systems, including wireless OFDM systems. Background technique [0002] Orthogonal Frequency Division Multiplexing, also known as "Multi-Carrier Modulation" (MCM) or "Discrete Multi-Tone Modulation" (DMTM), divides and encodes high-speed incoming serial data on multiple different carrier frequencies within a communication channel (referred to as "subcarriers") to down-modulate the serial data to transmit data from one user to another. Serial information is decomposed into multiple sub-signals, which are simultaneously transmitted in parallel via sub-carriers. [0003] By spacing the subcarrier frequencies at symbol frequency intervals for transmission, the peak power of each modulated subcarrier is precisely aligned with the zero power component of another modulated subcarrier, thereby providing orthogon...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/36H04L27/38
CPCH04L27/364H04L27/3863H03D3/009H04L25/03159H04L2025/03414
Inventor 阿施拉夫·达尼
Owner ST ERICSSON SA
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