单音干扰对QPSK解调性能影响分析

Analysis on Tone Interference Effects on QPSK Demodulation Performance

QPSK调制技术具有误码性能好、频谱利用率高的优点,但在工程中杂散直接影响了其误码特性。在窄带系统中将杂散等效为单音干扰,建立了带单音干扰的QPSK模型,从理论上分析了单音干扰各种参数对QPSK解调性能产生影响的机理。指出单音干扰会导致QPSK星座图形变,甚至引起系统假锁,从而导致比特误码率升高,仿真结果分析了BER特性受各种参数的影响程度。指出卷积编码可以有效地抑制杂散,提高QPSK的误码性能,并通过仿真研究了卷积编码改善误码特性的适用条件。

The QPSK modulation technology has such features as ideal bit error rate （BER）,higher spectrum efficiency,etc.The spurious signal may be generated by AD/DA,low-noise amplifiers,frequency synthesizers,and mixers,which affects the QPSK perform-ance.In the application conditions,some of the spurs are expected to be relatively narrowband signals and as such may be modeled as tone interference.Based on analysis the spur magnitude,frequency and phase effect on QPSK constellation diagram,the spur offset in frequency from the center frequency of QPSK signal,false lock of receiver onto the spur,adversely affects bit error rate performance.The simulations results show that the addition of convolutional coding can effectively suppress the spurious signals and improve the BER per-formance.In the simulation,the applicable condition of convolutional coding in the improvement of BER performance is studies.