CiteULike: dcastros Popovic http://www.citeulike.org/user/dcastro/author/Popovic CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dcastro/article/2782041 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 50, No. 3. (2002), pp. 814-826.</i><br /><br />The generation of RF/microwave power is required not only in wireless communications, but also in applications such as jamming, imaging, RF heating, and miniature dc/dc converters. Each application has its own unique requirements for frequency, bandwidth, load, power, efficiency, linearity, and cost. RF power is generated by a wide variety of techniques, implementations, and active devices. Power amplifiers are incorporated into transmitters in a similarly wide variety of architectures, including linear, Kalm, envelope tracking, outphasing, and Doherty. Linearity can be improved through techniques such as feedback, feedforward, and predistortion Power amplifiers and transmitters for RF and microwave FH Raab P Asbeck S Cripps PB Kenington ZB Popovic N Pothecary JF Sevic NO Sokal doi:10.1109/22.989965 Microwave Theory and Techniques, IEEE Transactions on, Vol. 50, No. 3. (2002), pp. 814-826. 2008-05-09T23:54:52-00:00 Microwave Theory and Techniques, IEEE Transactions on 50 3 814 826 amplifier microwave power rf transmitter http://www.citeulike.org/user/dcastro/article/2774720 <i>Microwave Symposium Digest, 2002 IEEE MTT-S International, Vol. 2 (2002), pp. 1317-1320.</i><br /><br />An X-band oscillating element can be achieved in compact form with class-E operation and high directivity. An annular ring is used both as the radiating element and microstrip feedback circuit for the class-E amplifier. A maximum conversion efficiency of the DC power consumption to radiated copolarized power is 55% at 10 GHz with maximum effective radiated power of 23.6 dBm and total radiated power of 15.5 dBm. This active antenna element is shown to be a good candidate for high aperture efficiency spatial power combining A 10 GHz integrated class-E oscillating annular ring element for high-efficiency transmitting arrays JA Hagerty Z Popovic doi:10.1109/MWSYM.2002.1011911 Microwave Symposium Digest, 2002 IEEE MTT-S International, Vol. 2 (2002), pp. 1317-1320. 2008-05-09T08:23:39-00:00 Microwave Symposium Digest, 2002 IEEE MTT-S International 2 1317 1320 active antenna efficiency high integrated oscillator http://www.citeulike.org/user/dcastro/article/2774610 <i>Microwave Symposium Digest, 1999 IEEE MTT-S International, Vol. 2 (1999), pp. 663-666 vol.2.</i><br /><br />This work discusses the use of a microstrip-fed slot antenna to directly provide the necessary output match and harmonic tuning for a 10 GHz class-E power amplifier. There is no matching circuit at the output of the amplifier since the slot is designed to provide the correct impedance at the fundamental frequency and to present an open circuit at the second harmonic. This eliminates losses in the matching circuit and decreases circuit area. Since the class-E amplifier requires a complex output load, the designed slot antenna is not a resonant structure. The device used is an Alpha AFM04P2 MESFET, which has a maximum output power of about 21 dBm. The measured performance of the active antenna shows 74% drain efficiency, 62% power-added-efficiency (PAE), and 20 dBm output power at 10 GHz, at 5 dB gain compression. The PAE is greater than 50% in a 400 MHz bandwidth A 10 GHz high-efficiency active antenna MD Weiss Z Popovic doi:10.1109/MWSYM.1999.779848 Microwave Symposium Digest, 1999 IEEE MTT-S International, Vol. 2 (1999), pp. 663-666 vol.2. 2008-05-09T07:26:08-00:00 Microwave Symposium Digest, 1999 IEEE MTT-S International 2 663 666 vol.2 active antenna efficiency high http://www.citeulike.org/user/dcastro/article/2774539 <i>Antennas and Propagation Society International Symposium, 1997. IEEE., 1997 Digest, Vol. 1 (1997), pp. 18-21 vol.1.</i><br /><br />Second-resonance slot antennas, due to their ability to transmit and receive on both sides of a microstrip ground plane, are often employed in planar active antenna arrays. For example, in an amplifier array, the input and output of an amplifier circuit are connected to orthogonally polarized antennas. The purpose of using orthogonal polarizations is to ensure amplifier stability. We present a 7 GHz cross-slot antenna designed to be used in a mixer/phase detector active antenna. By incorporating a varactor diode into the microstrip feed line, the cross-slot resonance can be electronically tuned over a 10% bandwidth. By mechanically varying the feed line (tuning stub) length, a 45% 2:1 VSWR bandwidth is possible A tunable second-resonance cross-slot antenna MA Forman ZB Popovic doi:10.1109/APS.1997.630066 Antennas and Propagation Society International Symposium, 1997. IEEE., 1997 Digest, Vol. 1 (1997), pp. 18-21 vol.1. 2008-05-09T06:48:25-00:00 Antennas and Propagation Society International Symposium, 1997. IEEE., 1997 Digest 1 18 21 vol.1 active antenna http://www.citeulike.org/user/dcastro/article/2774523 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 48, No. 12. (2000), pp. 2686-2691.</i><br /><br />This paper presents an optically switched X-band active antenna element for half-duplex transmit/receive (T/R) applications. The antenna element is designed to be a unit cell of a quasioptical array with fast switching between T and R and with built-in phase-shifterless beamforming. The measured performance of the active element is 14 dB gain contributed by the power amplifier (PA) in transmission and 16 dB gain contributed by the low-noise amplifier in reception, with 30 dB isolation between T and R. The switching is accomplished with only 1 μW of optical power for 1.7 μs switching time (1.7 pJ of optical energy) and a rise time of 2 ns at 10 GHz with 7 mW of optical power (14 pJ of optical energy). The design, implementation, and measured performance of the optically controlled transmit/receive circuit are presented A transmit/receive active antenna with fast low-power optical switching J Vian Z Popovic doi:10.1109/22.899031 Microwave Theory and Techniques, IEEE Transactions on, Vol. 48, No. 12. (2000), pp. 2686-2691. 2008-05-09T06:44:38-00:00 Microwave Theory and Techniques, IEEE Transactions on 48 12 2686 2691 active antenna fast low power receiver transceiver transmiter