Study of a Two Carriers Solid State Straight through Repeater at 7.5 GHz

A study of a 7.1 - 7.7 GHz repeater, designed to satisfy CCIR recommendations, and which avoids the necessity of any change in frequency is described. Two 300 channel carriers can be transmitted and it is therefore necessary that each amplifier should present the following characteristics : a 300 MHz minimum bandwidth, a 4 dB maximum noise figure, a 1 dB gain compression point of at least + 26 dBm, a 0.5°/dB maximum AM/PM conversion, a nominal output power of 15.5 dBm per carrier (for a 6 foot antenna), and a 46 dB overall gain. In order that the total system noise power be less than 200 pW, we show that for a 50 km link, a ± 15 km displacement around the centre of the link can be tolerated. An amplifier was built which meets these specifications. The 2 input stages were optimised for minimum noise measure, and the output stages were optimised for minimum intermodulation. Such a repeater, whose d.c. consumption is low (12 W) could easily be powered by solar cells and could be used on many inaccessable sites.