Cynthia Y. Hang

High efficiency power amplifier with novel PBG ground plane for harmonic tuning

A high efficiency S-band power amplifier utilizing a novel photonic band-gap (PBG) ground plane is presented. This novel design not only allows intrinsic second and third harmonic tuning without using any filters, but also offers the potential of greatly reducing the amplifier size. An increase of 10% in power added efficiency (PAE) and 1.3 dB in output power has been achieved when compared to a reference amplifier.

High-efficiency push-pull power amplifier integrated with quasi-Yagi antenna

This paper presents a C-band push-pull power amplifier integrated with a modified uniplanar quasi-Yagi antenna. In this circuit, corrugation is added to the truncated ground plane of the antenna so that it can be used for both out-of-phase power combining and second harmonic tuning. By using the active integrated antenna concept, this novel circuit eliminates the usage of an ordinary 180/spl deg/ hybrid at the power-amplifier output stage, therefore eliminating the losses associated with the hybrid, resulting in a compact and high-efficiency power-amplifier design with intrinsic second harmonic suppression. At an operating frequency of 4.15 GHz, a maximum measured power-added efficiency (PAE) of 60.9% at an output power of 28.2 dBm has been achieved. The measured PAE is above 50% over a 260-MHz bandwidth. Additionally, the second harmonic radiation is found to be 30 dB below the fundamental in both E- and H-planes. When the circuit is subjected to a two-tone test, the measured third-order intercept point is 37 dBm, about 10 dB above the P/sub 1 dB/ point.

Push-pull power amplifier integrated with quasi-Yagi antenna for power combining and harmonic tuning

In this paper, a C-band active integrated antenna push-pull power amplifier is presented. The circuit utilizes a uniplanar quasi-Yagi antenna with corrugated ground plane for both out-of-phase power combining and second harmonic tuning. This novel structure results in a compact and high-efficiency power amplifier design with automatic second harmonic suppression. At an operating frequency of 4.15 GHz, a maximum measured PAE of 60.9% at an output power of 28.2 dBm has been achieved.

A new amplifier power combining scheme with optimum efficiency under variable outputs

This paper presents a new power combining scheme, which has either one or four amplifiers on depending upon the levels of input signal. This approach realized by utilizing a unique combiner that is lossless and has constant gain under both scenarios. As a result, for the system where variable output power is required, this combining scheme can be used in an amplifier design with optimum efficiency. Measurement data show 15% power efficiency for the four-amplifier scenario and 28% for the single amplifier scenario at 13dBm input power. We also investigate the possibility of using this combiner in an envelope tracking amplifier.

Effects of output harmonic termination on PAE and output power of AlGaN/GaN HEMT power amplifier

The authors experimentally investigate and discuss the effects of output harmonic termination on power added efficiency (PAE) and output power of an AlGaN/GaN high electron mobility transistor (HEMT) power amplifier (PA). The AlGaN/GaN HEMT PA with gate periphery of 1 mm was built and tested at L-band. Large-signal measurements and comparisons of the PAE and output power were carried out at different DC bias conditions from 50% of saturated drain current (I/sub dss/) to 1% of Id., for the PA with and without output harmonic termination. For class-AB operation at 25% of I/sub dss/, an increase of about 10% in peak PAE and 1 dBm in output power were observed in saturated output power range. Improvements of up to 9% in PAE and 1.2 dBm in output power were achieved over the measured DC bias conditions provided the output harmonics are properly terminated.

High efficiency S-band class AB push-pull power amplifier with wideband harmonic suppression

A high-efficiency class-AB push-pull power amplifier is designed utilizing a novel photonic band-gap (PBG) ground plane. This design allows simultaneous tuning of both the second and the third harmonics, thus resulting in a high efficiency power amplifier design. The measured PAE is 63.8% at an output power of 28.2 dBm. In addition, the measured IP3 is 45 dBm, about 17 dB above the P/sub 1dB/ point.

Output harmonic termination techniques for AlGaN/GaN HEMT power amplifiers using active integrated antenna approach

In this paper, effects of output harmonic terminations on PAE and output power of AlGaN/GaN HEMT power amplifier are investigated. Using a traditional method of harmonic termination, we observe a substantial increase in PAE and output power. Further, we demonstrate the high efficiency AlGaN/GaN HEMT power amplifier with harmonic termination characteristics by using the active integrated antenna approach. For the microstrip-based AlGaN/GaN HEMT power amplifier, large signal measurements and comparisons of PAE and output power were done in class-AB operation with and without output harmonic terminations. For the antenna integrated power amplifier using an AlGaN/GaN HEMT with 1 mm gate periphery, output power of 30 dBm and peak PAE of 55 % with a power gain of 14 dB were achieved at a drain voltage of 18 V and a gate voltage of -2.8 V.

Adaptive microwave systems using DSP

Examples of adaptive microwave systems using DSP are introduced. These systems enable robust communication due to their adaptivity. First, a phased array system with smart antenna and retrodirective array features is shown. These functions can be switched easily just by changing the LO frequency, enabling versatile communications. Next, a power amplifier linearizer based on DSP is shown. The efficiency of the amplifier is improved using DSP linearization.

A High Efficiency Power Amplifier System for CDMA

In this paper, the study of a new power combining scheme which has either one or four amplifiers on depending upon the levels of input signal, is extended to a system with its RF carrier modulated by a IS-95 forward link CDMA signal. The performance is compared with the case where either one amplifier or a Wilkinson combined 4-amplfier array is used. The simulated data indicates that this new approach can reach high efficiency while still keeping the good linearity. In the case when the bias current is about 32% of Idss, the power added efficiency (PAE) of the new combining scheme is about 36.9%.