Combining circuit for a diversity receiving system

A combining circuit for use in a diversity receiving system, said combining circuit being for combining first and second received signals from first and second antennas to produce a combined signal, said combining circuit comprising:

• first and second frequency converting sections, supplied with the first and the second received signals, respectively, for frequency converting the first and the second received signals into first and second frequency-converted signals, respectively;
• a control circuit, connected to said first and said second frequency converting sections, for controlling a channel of said first and said second frequency converting sections;
• first and second preliminary amplifying sections, connected to said control circuit and to said first and said second frequency converting sections, respectively, for preliminarily amplifying the first and the second frequency-converted signals to produce first and second preliminary amplified signals which have first and second output levels, respectively, the first and the second preliminary amplified signals having first and second noise power levels, respectively, which are equal to each other;
• first and second main amplifying sections, connected to said first and said second preliminary amplifying sections, respectively, for mainly amplifying the first and the second preliminary amplified signals by first and second amplification degrees in proportional to the first and the second output levels, respectively, said first and said second main amplifying sections producing first and second main amplified signals having first and second phases, respectively;
• and
• a signal combining section, connected to said first and said second main amplifying sections, for combining the first main amplified signal with the second main amplified signal with the first phase shifted into the second phase, said signal combining section producing the combined signal.