unloaded Q

unloaded Q

[¦ən′lōd·əd ′kyü]
(electronics)
The Q of a system when there is no external coupling to it.
References in periodicals archive ?
Unloaded Q is a figure of merit for a resonator, and is the ratio of energy stored versus energy dissipated per RF cycle.
A rigorous mode-matching method was used to compute the resonant frequency, unloaded Q and fields of the desired resonant mode, as well as the spurious higher order modes of the conductor (solid or ring)loaded resonators.
A rigorous mode-matching method is used to compute the resonant frequency, unloaded Q and resonant-mode fields.
A rigorous mode-matching technique was used to compute the resonant frequency, unloaded Q and resonator fields.
TABLE I CONVENTIONAL GROUND-MOUNT CHARACTERISTICS Gain Noise Cumulative Stage (db) Figure (dB) NF (dB) Pigtail -0.1 0.1 0.10 connector Lightning -0.1 0.1 0.20 arrestor 100 ft -2.0 2.0 2.20 cable Filter -2.5(*) 2.5 4.70 LNA 15.0 0.4 5.10 Total 10.3 5.10 front end * Based on an unloaded Q of 6500, sixth-order quasi-elliptical design.
TABLE II CONVENTIONAL TOWER-MOUNT CHARACTERISTICS Gain Noise Cumulative Stage (dB) Figure (dB) NF (dB) Pigtail -0.1 0.1 0.10 connector Lightning -0.1 0.1 0.20 arrestor Filter -2.5(*) 2.5 2.70 LNA 30.0 0.4 3.10 100 ft -5.0 5.0 3.11 cable Total 22.3 3.11 front end * Based on an unloaded Q of 6500, sixth-order quasi-elliptical design.
Figure 1 shows the simulated difference in filter insertion loss for two filters, including a conventional filter with unloaded Q values of roughly 6500 and a superconducting filter with unloaded Qs of 30,000.
The high unloaded Qs translate into highly selective frequency responses with low passband insertion loss and high rejection.
Fabricated with superconducting films on special substrates rather than with conventional metal conductors on ceramic or polytetrafluoroethylene (PTFE) substrates, these filters are capable of unloaded Qs exceeding 50,000.
For receiver applications, HTS bandpass filters offer the best electrical performance of the three filter types with unloaded Qs approaching 50,000.
However, most standard tunable filters do not realize the unloaded Qs ([Q.sub.u]) needed to achieve high performance levels.
The RF leads are loosely coupled to the resonator so that the loaded and unloaded Qs can be assumed equal.