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Managing Phase Noise in Microwave Chains

November 12, 2010
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Introduction

Noise in oscillators is an old and new issue. It yet sometimes confuses even professional engineers, because oscillation itself is essentially an autonomous phenomenon. This paper is formatted to discuss the complete design of the frequency conversion chain using the end user approach (or application aspect) presented, viz. from the design specifications, concept designs, subsystems, simulation results and eventually conclusion.

Software defined radio (SDR) is now popular in wireless comunications. The technology is an enabler for many new variable capacity applications and cognitive radio. [21] This work tries to enlighten one, many times overlooked, but very important aspect in the designing of the SDR radio system. A major challenge for software defined radio is to equal the efficiencies of pure hardware solutions, while providing the flexibility and inteligence that only software can provide.

Radio system software developer will want to be shielded from all hardware (HW) developmental changes. On customer demand, he will only want to upgrade the multilevel digital modulation and bandwidth. Maybe even a digital protocol of radio-to-radio communication. What this will pull behind, one can only imagine. But some things are certain. Protocol can demand more memory and CPU resources. Higher speeds and higher level digital modulations will demand higher frequency amplitude dynamic and phase noise conditions in the rx/tx frequency conversion chains (HW) alone. [17] In good systems, with enough amplitude dynamic, these low noise conditions can only come from local oscillators. Power supplies and active lowpass filter must be made low noise. Electromagnetic shielding must be reasonable enough.

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