高頻調頻式振盪器

Abstract

調頻式振盪器為通迅系統的關鍵性零組件. 其製作方式約可分為兩種 : [1]為電感電容調變式, 其輸出波形為近似正弦波; [2]為電流充放電 式. 就設計方面及輸出波形品質的考量而言, 此兩種振盪器各有其優劣. 本論文將就上述兩種類型的振盪器進行評比與討論. 同時, 我們將討論利 用電流放大器及電容所組成的振盪器之成效及可行性. 除此之外且尤值的 一提的是, 我們提出一種全新的單晶微波積體電路振盪器, 其經由負阻抗 轉換器, 可變電容轉換器, 既單晶製成的電感並聯而成, 且可工作在微波 的頻率範圍. 經由模擬證實, 其振盪頻率的範圍約在2.25 GHz 至 1.7 GHz之間.由於我們提出的振盪器兼具高振盪頻率, 寬調幅既低相位雜訊等 特點, 且能完全以單晶微波積體電路的方式製作, 是以我們認為其在通訊 系統的應用上相當具有價值, 諸如跳頻式 GMSK 高頻無線電調變解調器的 製作上, 皆可為應用. Variable-Frequency Oscillators (VFO's), or Voltage Con- rolled Oscillators (VCO's), are widely used in communicationystems. Categorically, oscillators can be divided into twolasses :(1) tuned oscillators which provide nearly sinusoidalutputs; and (2) multivibrators circuits which switch back andorth between two astable states. In this thesis, oscillators implemented with differentechniques, such as LC-sinusoidal oscillators in the firstategory and relaxation type oscillators in the second cate-ory, are presented and compared. Besides, a prototype of ope-ational transconductance amplifier-capacitor (OTA-C) typescillator is also studied and discussed. Most important of all, we invented a novel monolithic ne-ative-resiatance LC VFO' s for use in the microwave range. Its composed of (1) negative impedance converter; (2) variableapacitance converter; and (3) monolithically fabricated induc-ors. By simulation results, the oscillator can operate at fre-uency from 1.7 GHz to 2.25 GHz. This circuit theoreticallyxhibits the benefits of both the two classes of oscillatorsentioned above.