Aerospace, Military & Defence
transceiver product line supports every element digital antenna spacing to C-band and, with some extra effort, an X-band element spacing could be realised. Next, the physical size of a mating RF up/down converter is shown in Figure 4. This particular board is intended as a test board companion for the dual transceiver board and again can be used to consider practical physical size constraints for this RF subsystem. The board is implemented with standard low cost methods, using all commercially available parts. Again, this shows that this type of implementation supports every element digital antennas up to C-band. If there is a migration to X- band, every digital element would be possible, enabling further integration with SiP (system-in-package) integration. These two boards outline that low cost
commercial implementations support every element in digital beam-forming phased arrays for frequencies up to C-band. An every element implementation at X-band and beyond could be realizable with further integration or as alternative beam-forming ICs can be used to reduce the number of waveform generator and receiver channels relative to the number of elements. 4:1 X- /Ku-band beam-formers are now becoming commercially available and are a practical approach for low cost digital beam-forming phased arrays at these frequencies.
Ka-Band element spacing Next, a Ka-band antenna element spacing is considered, as shown in Figure 5. At 30 GHz the /2 spacing is 5 mm, which, as shown, is quite challenging for the electronics. It is practical, however, for a 4:1 analog beam-former to be implemented within this spacing directly opposite of the antenna elements. The challenge is that the physical size constraints allow little opportunity for additional components. This necessitates the need for the inclusion of LNAs or PAs within the beam-forming package and for passive components, such as decoupling capacitors, to be buried within the PWB.
Figure 4. X-/ku-band RF up/down converter
Figure 2. Transceiver
channel spacing
Figure 5. Ka-band physical footprint
Figure 3. Transceiver product line includes dual waveform generators and receivers
22 March 2019 Components in Electronics
A fortunate design benefit for Ka-band satellite systems is that most systems separate transmit and receive functions into separate antennas. This provides the opportunity to design transmit only or receive only beam-forming ICs optimised for the particular task.
Summary
The continued advancement of RF ICs for the wireless industry has become an enabler for the proliferation of digital beam-forming phased array technology. It is now practical to design every element digital beam-forming phased arrays with standard PWB technology for frequencies as high as C-band. At higher frequencies of X-band an every element digital implementation is practical, but extra design effort for further integration
is likely required. Alternatively, a 4:1 analog beam-former could be used and offers additional space for the electronics and again allows for standard PWB implementation methods. This can become challenging at Ka-band physical size constraints. However, with integration of front-end electronics inside a beam-former package, either a subarrayed antenna architecture or an all analog beam-forming system is now realisable.
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