INDUSTRY MOBILES
enhancement of the performance of a CMOS PA so that it delivers the same output power, linearity and efficiency as any GaAs PA − even for LTE signals with high dynamic range.
The very impressive performance gains resulting from the addition of ET will help to unlock an entirely new avenue for smartphone manufacturers and for future developments within the RF front-end. Now that CMOS PAs are demonstrating the capabilities to serve high-end 3G and 4G applications, the time has come when smartphone developers can start to explore the full benefits of an integrated CMOS system.
These developers may seek to improve upon GaAs PA modules that already include multiple GaAs die and a separate CMOS controller die, because it is difficult to integrate the complex bias generation and digital control circuits onto a GaAs die.
Turning to a CMOS PAs could integrate these functions into a single chip, while delivering two substantial benefits: the use of simpler, lower-cost packaging such
Figure 6. Maximum linear power at -38dB ACLR: optimised bias settings.
Figure 5. Values for maximum linear power at -38dB ACLR: initial bias settings. These measurements reveal that the output rises by 6 dB, or fourfold, with the introduction of ET.
as flip-chip onto FR4 substrates; and the elimination of the
‘rats nest’ of bond wires found within today’s GaAs PA modules.
Integrating ET power supply modulators with CMOS PAs is relatively straightforward, because they have similar process requirements to those of a CMOS PA, and are today built on compatible CMOS process platforms. If further integration of ET power supplies with CMOS PAs takes place, mobile developers can benefit from reduced system cost and higher performance, opening up intriguing possibilities for the next-generation of smartphone products.
Making such a move should be an attractive option for the market leading suppliers of mobile phone modems and application processors, because they are all large, fabless CMOS vendors, with well-established foundry and supply chain relationships and significant buying power.
These firms may take the view that as the value of the RF front- end increases, the potential to absorb the PA into CMOS, and therefore make it an integral part of the smartphone chipset, offers some potential for significant revenue growth,improved multi-sourcing ability, and greater supply chain control.
A middle ground?
While it’s easy to see ET and CMOS as a ‘dream team’ solution for the future of the RF front-end, the truth remains that GaAs continues to dominate 90 percent of the PA market. That’s for good reason: GaAs is a well-established technology, and fundamental performance characteristics of PAs built with this material will continue to be advantageous in many applications.
However, ET is undoubtedly closing the ‘performance gap’ between the GaAs PA and its CMOS cousin. With new CMOS PAs coming to the market, such as Peregrine’s Global1 device announced earlier this year, there is potential for even greater performance gains.
When provided with a more equal playing field, in the short term the choice between CMOS and GaAs PAs will probably come down to the individual purchaser. Regardless of where CMOS PAs eventually find their place though, it is clear that ET will play a lead role in getting there.
With almost all PA suppliers and handset OEMs investigating this performance-enhancing technology, the question is no longer if ET it will impact the PA market, but when.
Copyright Compound Semiconductor Issue VI 2014
www.compoundsemiconductor.net 45
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160