Diversity receiver and gain adjusting method therefor

1. A diversity receiver including a plurality of branches each comprised of a direct conversion type receiver, said diversity receiver comprising:

a plurality of variable gain amplifiers, the gains of which can be controlled, for amplifying a received signal of each of said branches;

a plurality of reception level measuring circuits for measuring a reception level in each of said branches to deliver the result of the measurement;

a reception level selector circuit for comparing the results of the measurements of the reception levels in the respective branches to select and deliver the result of the measurement of a maximum reception level which is the highest reception level; and

a gain setting circuit for adjusting the variable gain amplifiers of all branches, including variable gain amplifiers belonging to a branch corresponding to the maximum reception level, to the same gain such that output levels of said variable gain amplifiers are set to a preset predetermined value, wherein:

said reception level measuring circuit calculates average power of the reception levels on a slot-by-slot basis for each of said branches, said slot indicating a preset predetermined time interval, to deliver the calculated average power as the result of the measurement of the reception level, and

said reception level selector circuit determines the maximum reception level for each of the slots by comparing the result of the measurement of the reception for all said branches during each of said slots, and sets all the variable gain amplifiers to the same gain based on the maximum reception level.

2. The diversity receiver according to claim 1 , wherein said reception level measuring circuit and said reception level selector circuit are included in a single integrated circuit device.

3. The diversity receiver of claim 1 , wherein the gain setting circuit adjusts the gain of each of the plurality of variable gain amplifiers during a slot based on a maximum reception level measured in a preceding slot.

4. The gain adjusting method of claim 1 , wherein the variable gain amplifiers are set to the same gain based on the maximum reception level determined during a preceding slot.

5. A gain adjusting method for a diversity receiver which comprises a plurality of branches each including a direct conversion type receiver, said each branch comprising a plurality of variable gain amplifiers, the gains of which can be controlled, said method comprising:

measuring a reception level for each of said branches to deliver the respective results of the measurements;

comparing the measurement results of reception levels in said respective branches with one another to select the result of the measurement of a maximum reception level which is the highest reception level; and

adjusting the variable gain amplifiers of all said branches, including variable gain amplifiers belonging to a branch corresponding to the maximum reception level, to the same gain such that output levels of said variable gain amplifiers are set to a preset predetermined value wherein:

the measuring a reception level for each of said branches comprises calculating average power of the reception levels of each of said branches on a slot-by-slot basis, a slot indicating which is a preset time interval, and outputting the measured reception levels for each of said branches for each of said slots,

the maximum reception level for each said slot is determined by comparing the output measured reception levels for each said branch during said slot, and

all the variable gain amplifiers are set to the same gain based on the determined maximum reception level.