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Jun OTSUKI Hao SAN Haruo KOBAYASHI Takanori KOMURO Yoshihisa YAMADA Aiyan LIU
This paper presents a technique for reducing spurious output of balanced modulators used in transmitters and arbitrary waveform generators. Two-step upconversion is a convenient way to produce a desired single-sideband (SSB) radio-frequency (RF) signal--baseband quadrature I and Q signals (which are analog outputs of direct digital frequency synthesizers) are upconverted by mixers and local oscillators (LOs)--but mismatches between the DACs in I and Q paths cause spurious output. We propose a method of dynamically matching the I and Q paths by multiplexing two DACs between I and Q paths in a pseudo-random manner. MATLAB simulation shows that multiplexing the two DACs spreads the spurious output, caused by mismatches between the two DACs, in the frequency domain, and reduces the peak level of spurious signals.
Ibuki MORI Yoshihisa YAMADA Santhos A. WIBOWO Masashi KONO Haruo KOBAYASHI Yukihiro FUJIMURA Nobukazu TAKAI Toshio SUGIYAMA Isao FUKAI Norihisa ONISHI Ichiro TAKEDA Jun-ichi MATSUDA
This paper proposes spread-spectrum clock modulation algorithms for EMI reduction in digitally-controlled DC-DC converters. In switching regulators using PWM, switching noise and harmonic noise concentrated in a narrow spectrum around the switching frequency can cause severe EMI. Spread-spectrum clock modulation can be used to minimize EMI. In conventional switching regulators using analog control it is very difficult to realize complex spread-spectrum clocking, however this paper shows that it is relatively easy to implement spread-spectrum EMI-reduction using digital control. The proposed algorithm was verified using a power converter simulator (SCAT).