Stub for which the open circuit appears at the equivalent coupling plane of the DR, about equal to the Looking toward the DR from this port, the circuit appears as if it were an open circuited transmission line Resonate with the reactance of the active device input (gate) port. We know that the load must have a reactance XI = 62.5 ohms to It remains to determine the length of a 50 ohm terminated microstrip line between the coupling plane of the DRĪnd the gate terminal of the active device. Negative resistance of -40.8 ohms is sufficient to allow the transistor to build up and sustain oscillation at The resultant input impedance of the active port is Za = -40.8 -j62.5 ohms at the desired frequency. Taking etch tolerances into consideration, the length of the feedback stub is chosen as 45 degrees. On the other hand, for the active port, a shorterįeedback stub induces higher negative resistance.įinally, negative resistance is reduced if the electrical length of the feedback stub is less than 25 degrees. More rapid the port reactance change with frequency. By adjusting the electric length of the feedback stub, various port impedanceĬharacteristics for Za (?) in the band of interest (6-15 GHz) can be obtained.įrom the port reactance characteristic, we observe that the shorter the electric length of feedback stub, the The open stub (characteristic impedance of 50 ohms), which is terminated at the source end of the FET, servesĪs the feedback element. The characteristic impedance of the output transmission line, Or gate of the transistor is the negative of Za.
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Schematic diagram of the series feedback DRO.ĭetermine the electrical spacing of the dielectric resonator such that the reactance it presents to the base Has the possible maximum variation near resonance in order to insure high circuit Q.įigure 1. Optimize Za (?) with the parameters in the feedbackĬircuit and in the matching network to ensure that Ra (?0) is less than or equal to -25 ohms and Xa (?) Matching network and the load as shown as figure1. Create an active one-port analysis that consists of the active device, the feedback circuit, the.Add a feedback circuit to ensure that the stability factor of the active device with the feedbackĬircuit is less than unity with enough margin.Signal S-parameter of the device for the design. Select an active device that is capable of oscillation at the design frequency, and use the small.
Noise characteristics, while the GaAs FET is required for higher frequencies.įor example, a DRO with a DR as a series feedback element can be designed using following design procedure: The Si-bipolar transistor is generally selected for lower phase
Practically, a GaAs FET or a Si-bipolar transistor is chosen as the active device for the The design technique we will discuss is for a dielectric resonator (DR) to be used as a series feedbackĮlement. This paper summarizes design techniques for DROs and the voltage- tuning DRO (VT-DRO), and presents measuredĭata for them including phase noise, frequency stability and pulsing characteristics. Oscillators that are phase-locked to reference frequencies, such as crystal oscillators. These characteristics make DROs a natural choice both for fundamental oscillators and as the sources for MIC circuitries, simple construction and the ability to withstand harsh environments. The DROs are characterizedīy low phase noise, compact size, frequency stability with temperature, ease of integration with other hybrid They find use both in military and commercial applications. This is the newest member of our diverse family of frequency sythesizers.ĭielectric Resonator Oscillators (DRO) are used widely in today's electronic warfare, missile, radar andĬommunication systems. PC-programmable and features programmable pre-set frequencies, amplitude control, disable outputs, automatic reference detect and many other features making it extremely versatile.
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GED completed development of a portable RF Signal Generator Ranging from 1 to 2 GHz with 100kHz Resolution.
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