In the AR6A repeater bay. microwave carrier power for both the receiver and the transmitter is derived from a single voltage-controlled crystal oscillator. For long-term stability, this oscillator is phase locked to an externalreference frequencyI available at each radio station. From the output signal of this oscillator, an active frequency-multiplier chain generates about +21 dBm power in the 6-GHz band. Part of this power serves as the local oscillator signal for the transmitter directly. The other part is shifted in frequency, to produce the local oscillator signal for the receiver.
The AR6A Radio System requires precise control of the local oscillator frequency at repeaters and main stations, so that the IF equalizer pilots will be accurately located with respect to the narrowband crystal pick‐off filters. In addition, the accumulated frequency error from each repeater and main station must be limited to a value that can be corrected by the tracking receiver of the multimastergroup terminal. Precise frequency control is maintained along the route by locking local oscillators to a stable and accurate frequency reference provided at each repeater station by the Microwave Carrier Synchronization Supply (MCSS). The MCSS provides a source and a backup for this signal. Extensive monitoring circuitry in the MCSS detects failed conditions. The accuracy of the two oscillators is continuously monitored by making frequency comparisons of their output. These frequency‐monitoring circuits are also used to make yearly adjustments to the oscillators using a rubidium frequency standard as reference. This paper describes the MCSS System that has been developed for the AR6A Radio System.
This paper describes the essential features and the performance of the AR6A microwave transmitter and receiver. Subsystems that are major contributors to repeater noise are explained in detail. Design objectives for each of these units are given and compared to typical results obtained from measurements. Transmitter linearity was improved substantially through the use of predistortion. The thermal noise contribution of the receiver was reduced by use of a new low‐noise microwave preamplifier.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.