A method for relaxing specifications of analog LPF for π/4-shift QPSK signal generator

✍ Scribed by Akira Yasuda; Hiroshi Tanimoto; Takako Oda

• Book ID: 101294862
• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 185 KB
• Volume: 83
• Category: Article
• ISSN: 1042-0967
• DOI: 10.1002/(sici)1520-6440(200005)83:5<53::aid-ecjc6>3.0.co;2-y

✦ Synopsis

Important issues for PHS and other portable terminals are reducing size, increasing precision, and lowering power consumption. In this paper, the authors propose a S/4-shift QPSK signal generator which uses an analog FIR filter as a way to achieve the above goals. In the proposed method, an analog FIR filter with minimal effects on relative component dispersion is used to attenuate adjacent channel noise and dramatically ease the characteristics required from the continuous time LPF. In addition, by supplementing the ROM data with reversed characteristics, degradation in modulation precision due to the analog FIR filter is minimized. This results in a reduction in power consumption in the continuous time LPF. A test chip 2.1 mm u 2.0 mm in size has a modulation precision under 1.8%, a power leakage into adjacent channels (600 kHz) under 60 dB, and a current consumption under 17 mA.