Here we report a novel linearization and efficiency improvement technique for heterojunction bipolar transistor (HBT)-based Wireless Code Division Multiple Access (WCDMA) power amplifier. A process solution is proposed where a tantalum nitride (TaN) layer is strapped to the HBT base metal layer that resolves the current hogging issue. This is known as the strap ballasting technique. The resistance introduced by TaN improves the linear output power without trading-off its power added efficiency. At supply voltage of 4 V, the strap ballasting methodology improves the adjacent channel leakage ratio by 4.5 dB compared to the conventional base ballasting technique at output power of 28 dBm. The corresponding improvement in power added efficiency is 4%. The maximum output power delivered by power amplifier is 36 dBm. The proposed technique can be employed in the WCDMA power amplifier to minimize the fundamental trade-off issue between linear output power and efficiency.
Particle accelerators such as cyclotrons and linear accelerators (LINACs) are widely used as a vehicle for fundamental research in physics as well as energy R&D, medicine, industrial manufacturing and security. A particle beam composed of protons, ions or neutrons can be created by accelerating particles generated from a source using high energy electric fields. Traditionally, particle accelerators found around the world employ the use of tube-based amplifiers including tetrodes, klystrons and traveling wave tubes (TWTs). Tube technology has proven to be robust over many decades and continues to dominate the ultra-high power market. However, they are also large, heavy, cumbersome, expensive to maintain and are potentially dangerous, requiring high-voltage kV power supplies to operate. Furthermore, considering the aging installations of tube amplifiers, replacement of these with new tubes may not be the most sensible approach for the future evolution of accelerator systems. With the advent of high power density semiconductors like gallium-nitride (GaN), solid state power amplifiers (SSPAs) are primed as the future replacements for mature tube amplifiers. GaN HEMT devices are experiencing rapid development in power density, efficiency and longevity and have grown in adoption since its commercial inception around 2008. Capable of reaching power densities of 12W/mm, GaN devices are seen as the next-generation solid state power technology. Presently, the efficiency of GaN HEMT is similar to that of tube amplifiers, but have the advantages of operating <100V and are relatively inexpensive to replace. Furthermore, GaN technology benefits from the cost savings and size scaling trends of the advancing semiconductor industry. This means that the price per watt will be driven lower as smaller and more efficient devices are introduced.
An RF power amplifier is connected to a low power transmitter’s output port, usually marked ‘Antenna’. It is matched to the output impedance of the driver transmitter. The input is marked TX. Its output port, again usually marked ‘Antenna’ is usually engineered to work at the same impedance.
This paper presents a novel dual mode configurable and tunable power amplifier (PA) that achieves a wide-bandwidth and high gain across a operational frequency spectrum of 20 to 30 GHz. The proposed PA used two-stage tunable PA which can be configured as a tunable synchronous mode or tunable stagger-tuned mode PA. PA is implemented by using a distortion-free varactor at the input and output tank of PA. The designed PA includes a high-Q CMOS active inductor (CAI) which provides a widely tunable output matching network. The resistive feedback is used for self-biasing in the designed PA which helps to enhance the linearity, stability of common source (CS) amplifier. The inter-stage impedance matching network consists of shunt and series resonance circuits are employed for maximum power added efficiency (PAE). Furthermore, the capacitive coupled reuse technique is implemented in each stage between the cascaded transistor to reduce the power consumption. A proposed PA is designed using a 65 nm CMOS technology. A measured power gain at the synchronous operation of PA is 28.4 ±0.5 dB with 1.31 GHz bandwidth while power gain at staggered operation is 22.1 ±0.5 dB with 3.71 GHz bandwidth. The measured saturated power (Psat) is 14.21 dBm and the noise figure (NF) is 5.2 dB. The group delay (GD) variation for staggered operation is 57 ±10 ps from 20-30 GHz. A proposed PA exhibits good linearity (IIP3) of 14.5 dBm and PAE is 47.5 % at 24 GHz. The power consumption of a designed PA is 48.56 mW with a supply voltage of 1.2 V.
The first thing you have to do is compromise, because any realistic loudspeaker load is going to confuse things terribly. So, you load your amplifier with a low-inductance power resistor of the correct resistance – eight ohms, or whatever.
Usage of cellular phones for long duration generates heat which leads to reduced data/talk time. To overcome this constrain supply voltage for the radio frequency power amplifier in CDMA/WCDMA cellular phones is controlled which can also improve PA efficiency. For bandwidth enhancement a C Shaped antenna is used which is fed by mini-coaxial cable along with a thin printed ground-line that protrudes from ground-plane to be a balance-feed structure. Prototype of the antenna with length 25 mm, height 30 mm and width 5 mm has been designed. The human’s hand effect on impedance bandwidth and radiation characteristics of the antenna is studied. A prototype is designed to cover hex-band: CDMA (8.24-8.94 GHz), GSM (8.8-9 GHz), DCS (1.71-1.88 GHz), PCS (1.85-1.99 GHz) and WCDMA (1.92-2.17 GHz), GPS (2.18-2.2 GHz). To verify the theoretical work, experimental results are shown.
Audio signals have frequencies in the range of roughly 20 to 20,000 hertz (20 kHz) as would be found in an audio amplifier.
This paper presents an analytical investigation on the effect of nonlinear high power amplifiers on the physical layer security of multiple-input-multiple-output (MIMO) wiretap channels with orthogonal space-time block code (OSTBC). The performances of the MIMO–OSTBC system are evaluated under Rayleigh fading channels when the eavesdropper channel is uncorrelated with the main one. Analytic closed-form expressions for the secrecy outage probability (SOP) and the probability of strictly positive secrecy capacity are delivered. In order to obtain the secrecy diversity order and the secrecy array gain, an asymptotic SOP expression is also derived. Simulation results are provided to validate our analytical analysis and show an excellent agreement between numerical results and Monte-Carlo simulation curves. Furthermore, the impact of the nonlinearity factors on the SOP performances is discussed.