radio signal from each branch of the plurality of branches to form a plurality of digitized samples corresponding thereto; a plurality of branch processors coupled to the plurality of A/D converters for converting the plurality of 5 digitized samples into a plurality of frequency domain signals, each frequency domain signal corresponding to a subchannel of the plurality of subchannels and further corresponding to a branch of the plurality of branches, and each frequency domain 10 signal comprising a plurality of frequency domain samples corresponding to a plurality of frequencies within each subchannel, each branch processor comprising:
a weighting factor element for determining a weight- 15
ing factor for each subchannel of the branch from
which the branch processor receives the radio
signal after digitization, the weighting factor being
determined from instantaneous signal energy and
noise power, the instantaneous signal energy and 20
the noise power calculated from the plurality of
frequency domain signals; and
a multiplier coupled to the weighting factor element
for multiplying the frequency domain signal cor-
responding to the branch and each subchannel 25
thereof by the weighting factor therefor to produce
a plurality of weighted frequency domain signals
corresponding to the branch and each subchannel,
wherein the apparatus further comprises a combiner
coupled to the plurality of branch processors for 30
combining the plurality of weighted frequency
domain signals that correspond to all the branches
of each subchannel to produce a diversity-com-
bined frequency domain signal for each subchan-
nel. 35
16. The selective call base station of claim 15, wherein the combiner comprises:
a cophaser for cophasing the plurality of weighted frequency domain signals that correspond to all the branches of each subchannel to produce a plurality of 40 weighted cophased frequency domain signals; and
a summer coupled to the cophaser for summing the plurality of weighted cophased frequency domain signals to produce the diversity-combined frequency domain signal for each subchannel.
17. The selective call base station of claim 15, wherein each subchannel includes upper and lower guard bands comprising ranges of frequencies at which no significant
amount of energy is transmitted in the plurality of radio signals, and wherein the weighting factor element comprises a noise estimator coupled to one of the plurality of branches for calculating a first average magnitude squared value of the plurality of frequency domain signals corresponding to the branch throughout the upper and lower guard bands of the plurality of subchannels, and for estimating the noise power corresponding to the branch to be equal to the first average magnitude squared value calculated therefor.
18. The selective call base station of claim 17, wherein each subchannel includes an information band comprising a range of frequencies within which substantially all energy of the subchannel is transmitted by the plurality of radio signals, and wherein the weighting factor element further comprises a signal energy estimator coupled to the one of the plurality of branches for calculating a second average magnitude squared value of the frequency domain signal corresponding to the branch and to each subchannel thereon throughout the information band, and for estimating the instantaneous signal energy corresponding to the branch and each subchannel thereon to be equal to the second average magnitude squared value calculated therefor.
19. The selective call base station of claim 18, wherein the weighting factor element further comprises a calculator coupled to the noise estimator and to the signal energy estimator for calculating the weighting factor for the branch and each subchannel as equal to a square root of the instantaneous signal energy corresponding to the branch and each subchannel, divided by the noise power corresponding to the branch.
20. The selective call base station of claim 15, wherein each branch processor further comprises:
a zero-pad element for increasing the plurality of digitized samples to an integer power of two; and
a Fast Fourier Transform (FFT) element coupled to the zero-pad element for performing a Fast Fourier Transform on the plurality of digitized samples after zeropadding to generate the plurality of frequency domain samples corresponding to the plurality of frequencies within each subchannel.
21. The selective call base station of claim 20, wherein each branch processor further comprises a windowing element coupled to the zero-pad element for windowing the plurality of digitized samples by applying a Hanning window prior to the step of increasing the plurality of digitized samples to an integer power of two.
