EMC Enhanced Constant 'Z' Modulator.
Abstract
The EMC Enhanced constant Z modulator (EECZM) research and development effort at ITT-A/OD was undertaken to provide an amplitude modulation capability for a low-noise,, medium power (1 Watt), wideband (225-400 MHz), frequency hopping (1000 hops/sec) synthesizer currently in development at the ITT-A/OD facility for RADC. The primary objectives was to amplitude modulate the synthesizer's RF carrier to the required modulation percentage while avoiding frequency modulation of the RF carrier. AN RF carrier amplitude modulator can seriously degrade synthesizer noise performance through modulator impedance changes during the modulation cycle. This change in impedance causes frequency modulation of the synthesizer's voltage controller oscillator (VCO) resulting in RF carrier FM sideband extending far beyond the AM sidebands for a large modulation index. Usually the modulator is isolated from the VCO by 20 to 30 dB of buffer amplification to minimize VCO frequency modulation; however, buffer amplifiers tend to degrade the overall synthesizer noise performance. By controlling the modulator's impedance to the VCO during the modulation cycle, the VCO buffer stages can be omitted while RF carrier frequency modulation is minimized.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1984
- Accession Number
- ADA147715
Entities
People
- R. E. Reed