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Key Specifications and Definitions
Narda DROs operate in the 3 to 18 GHz frequency range and typically use bipolar and FET active devices, depending on the requirement. These units are designed for MIL-E-5400 and MIL-E-16400 environments. Pertinent specifications are discussed below.
Output Power and DC Current
A typical DRO source will provide a power out of +12 dBm or more at room temperature. This level will vary about ±2dB over the specified temperature range with the
power decreasing with increasing temperature. The output power can be increased 5 to 10 dB by the addition of an optional buffer amplifier. These units are regulated to operate from +12 or +15 volts DC and the basic FET or bipolar transistorDROwill typically draw about 100 mA. The amplifier option will draw an additional 100 mA.
Frequency Stability
The frequency stability of the dielectric resonator oscillator is primarily determined by the temperature coefficient of the dielectric resonator. This is approximately 5 ppm per °C which translates to ±5 MHz at 12 GHz over a temperature range of -54 to +85°C. This temperature coefficient will degrade at higher frequency and also when a large range of mechanical tuning is required. In certain instances the package can be designed so that its change in dimension with temperature can accommodate change of the resonator frequency, thereby producing improved temperature performance. Varactor tuning can also be provided for either frequency or phase locking.
Spurious Response
A dielectric resonator oscillator is essentially free of spurious response. Typical specifications for non-harmonic spurious are on the order of 90 dBc which relates more to measurement system dynamic range than the actual presence of spurious signal. Harmonics are typically in the -10 to -20 dBc range and can be improved 20 to 30 dB by the addition of a miniature low pass filter.
Phase Noise
DROs offer excellent phase noise performance. Figure 1 compares typical performance of DROs built with FET, bipolar and Gunn active elements. The level of performance is in the -80 to -100 dBc per Hz range at a 10 kHz offset frequency around 6 GHz. Bipolar transistors offer superior performance; however, their utility is limited to about 6 GHz due to power fall off at higher frequencies. Gunn oscillators offer superior noise performance to FETs. However, this improved performance is normally offset by excessive power drain and the FETs are often preferred.
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