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A signal combination method unites the phase and amplitude relationships and uses second-order bandpass sampling for partial phase control of component signals. It relies upon a spectral replication sampling property. The performance of the technique for interception of slow frequency hopping spread spectrum, antenna combination and a switchable beam linear antenna array is discussed.

Bandpass sampling using suitable interpolants enables the frequency-shift in bandpass signals. The bandpass sampling technique phase shifts the second order sampled signals. The variation in the separation of sample streams enables the generation of different magnitudes of phase shifts. The phase shifts and frequency shifts are determined digitally.

A method for evaluating antenna diversity systems is presented with an example of a handset using up to four antennas in indoor mobile communication. The method includes a 'two-at-a-time' measurement test setup that uses maximum likelihood estimation of the covariance matrix and compensation for the imperfect match, which typically occurs during the design and evaluation process for compact antennas. The diversity performance of the antenna system can be presented as an effective order of diversity, which is the equivalent number of equal power, uncorrelated diversity branches for the same diversity gain at a given probability. Index Terms--Antenna arrays, covariance matrices, diversity methods, estimation, fading channels, mobile antennas, signal processing.

The Fourier relations between channel transfer function and scattering distribution can apply to personal and mobile communications where multipath is a prevalent phenomena. In this paper, the transform relations are reviewed and interpreted for the mobile radio channel. The effective scattering distribution is the vector product of the antenna pattern and the incident waves and is a scalar function of angle and delay time. The space base-band frequency correlation function transforms with the averaged power of the effective scattering distribution. If the angular power density marginal of the effective scattering distribution is known, then the transform relations can be used for configuring antennas for spatial diversity. Similarly, if the delay time marginal is known, then conditions for frequency diversity are available. The two-dimensional (2-D) transform gives a convenient route for assessing tradeoffs between combined frequency and space diversity. Using modeled distributions, solutions are given for spaced directive antennas and an example is discussed for the space-frequency tradeoff. Index Terms--Land mobile radio, land mobile radio diversity systems, multipath interference.