Timed Arrays

5ARRAY BEAMFORMING

An array feed or beamforming network combines the signals from all the elements to form a receive beam or, conversely, distributes a transmitted signal to the elements in the array to create a transmit beam. This chapter presents an assortment of analog and digital beamforming networks for creating and manipulating beams. A corporate feed has power splitters/combiners that guide the signals to/from the elements. One port in a receive array collects the signals from all the elements to form one beam. A multibeam array needs a corporate feed for each beam. The Blass matrix and the Butler matrix use transmission line to generate simultaneous multiple beams. Bootlace lenses create simultaneous multiple beam approaches without using transmission lines. Finally, the most versatile and advanced beamforming network is the digital beamformer which places an RF analog to digital converter (ADC) at each element and sends the bit representation of the signal at each element to the computer. Beams are formed in software rather than in RF hardware.

5.1 PCB TRANSMISSION LINES

Most feed networks have transmission lines, such as coaxial cables, stripline, and microstrip, and passive devices, such as couplers and power splitters or active components, such as amplifiers and receivers. Impedance matching at the connections ensures efficient power transfer through the feed network. In order to simplify matching, most devices and transmission lines have a characteristic impedance ...