An X-band GaN PA MMIC for phased array radar applications: Page 5 of 6

June 29, 2017 //By Stuart Glynn and Liam Devlin, Plextek RFI
Active phased array radars require numerous power amplifiers (PAs), which must be small, efficient and low-cost. This article describes an X-band PA MMIC that covers 9 to 11.5 GHz and satisfies these requirements. It has an output power of 7W (38.5 dBm) from a 29 dBm drive with a Power Added Efficiency (PAE) of 42%.

A comparison of the measured to modelled small-signal performance is plotted in Figure 4. The measured results are the dotted traces and the modelled (simulated) performance is the solid traces. It can be seen that there is a slight shift upwards in frequency of the measured performance compared to the modelled, but the agreement is good.


Figure 4: Comparison of measured to modelled s-parameters at 25V, 90mA bias.

The large signal performance was also measured RF-on-Wafer (RFOW). This was measured under pulsed operation at a duty cycle of 10% with a pulse width of 25µs. The measured results are plotted in Figure 5(a) for RF input powers of 5 dBm, 19 dBm, 29 dBm and 32 dBm at a quiescent bias of 25V, 90mA. With an input power of 29 dBm the RF output power is around 38.5 dBm or 7W.


Figure 5a: RFOW measured output power (at 10% duty, 25µs PW) for input powers of 5 dBm (red), 19 dBm (blue), 29 dBm (green) and 32 dBm (orange) at a quiescent bias of 25V, 90mA.

A corresponding plot of the PAE (Power Added Efficiency) is shown in Figure 5(b). At an input drive of 29 dBm the PAE is around 42% from 9 to 11.5 GHz.


Figure 5b: RFOW measured PAE (at 10% duty, 25µs PW) for input powers of 5 dBm (red), 19 dBm (blue), 29 dBm (green) and 32 dBm (orange) at a quiescent bias of 25V, 90mA.

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