Array errors due to manufacturing tolerances distort the array pattern. To minimize these errors, the array must be calibrated at the factory and at regular intervals once deployed. The transversal filter consisting of a sequence of weighted taps with intertap delay spacing offers a practical means for achieving the variable amplitude and phase weighting as a function of frequency that is required if an adaptive array system is to perform well against wideband interference signal sources. The distortionless channel transfer functions for a two-element array were derived. It was found that to ensure distortion-free response to a broadband signal the channel phase is a linear function of frequency, whereas the channel amplitude function is nearly flat over a 40% bandwidth. Quadrature hybrid processing provides adequate broadband signal response for signals having as much as 20% bandwidth. Tapped delay line processing is a practical necessity for 20% or more bandwidth signals. A transversal filter provides an attractive means of compensating the system auxiliary channels for the undesirable effects of the following: multipath interference; interchannel mismatch; and propagation delay across the array.

Chapter Contents:

• 10.1 Array Errors
• 10.2 Array Calibration
• 10.3 Broadband Signal Processing Considerations
• 10.4 Compensation for Mutual Coupling
• 10.5 Multipath Compensation
• 10.6 Analysis of Interchannel Mismatch Effects
• 10.7 Summary and Conclusions
• 10.8 Problems
• 10.9 References

Inspec keywords: adaptive antenna arrays; transversal filters

Other keywords: bandwidth signal; channel phase; two element array; distortion free response; broadband signal response; intertap delay spacing; interchannel mismatch; phase weighting; quadrature hybrid processing; transversal filter; channel amplitude function; array pattern; multipath interference; adaptive array system; tapped delay line processing; wideband interference signal source; distortionless channel transfer function; system auxiliary channel; propagation delay; array errors

Subjects: Antenna arrays; Filtering methods in signal processing; Filters and other networks