domingo, 30 de mayo de 2010


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Next-Generation Ultra Low-Noise Amplifiers


Next-Generation Ultra Low-Noise Amplifiers

Skyworks keeps it quiet with latest amplifiers
May 26, 2010
Next-Generation Ultra Low-Noise Amplifiers (LNAs) will meet demanding noise and linearity requirements for multiple wireless infrastructure applications.

Skyworks has introduced two low noise amplifiers (LNAs) for multiple cellular infrastructure receiver applications including GSM, CDMA, WCDMA and LTE base stations and repeaters.

The new monolithic microwave integrated circuit (MMIC) amplifiers allow infrastructure providers to meet a wide range of performance requirements with a single device that minimizes system noise figures with improved receiver sensitivity and stability.

"Skyworks is pleased to be expanding our infrastructure product portfolio particularly as estimates for mobile data traffic are expected to double every year through 2014," said David Stasey, VP of 'Analog Components' at Skyworks. "These solutions are just one of several devices that help reduce the size and complexity of networking equipment while enabling greater reliability, capacity and efficiency", he added.

The SKY67100-396LF (1.7 - 2.0 GHz) and the SKY67101-396LF (0.7 - 1.0 GHz) are gallium arsenide (GaAs) enhancement mode pseudomorphic high electron mobility transistor (pHEMT) LNAs designed for low noise figure down to 0.49 dB while providing unconditional stability and high-linearity performance up to OIP3 of 34 dBm.

The addition of an internal active bias circuitry provides stable performance over temperature. These new LNAs are available in a small, low-cost, industry-standard 2 x 2 x 0.75 millimeter (mm), 8 pin, dual flat no-lead (DFN) package and are layout compatible with each using a reduced -component matching network.






Freescale gets serious in RF; launches new LDMOS and enters GaAs MMICs

Freescale Semiconductor has rolled out new RF LDMOS power transistor designed for operation from 1.8 to 600 MHz and optimized for use under the potentially-destructive impedance mismatch conditions encountered in applications such as CO2 lasers, plasma generators, and magnetic resonance imaging (MRI) scanners. Freescale says the new MRFE6VP6300H FET is the world's first 50 V LDMOS transistor to deliver full-rated output power of 300 Watts CW into a load with a Voltage Standing Wave Ratio (VSWR) of 65:1 and is the only 50 V LDMOS transistor commercially offered with this level of performance.

"This outstanding technical achievement underscores Freescale's long track record of industry firsts in the RF power market," said Gavin Woods, vice president and general manager of Freescale's RF Division. "With this new transistor, manufacturers of CO2 lasers, plasma generators, MRI scanners and other industrial equipment can leverage unprecedented levels of ruggedness and RF power performance."

The other key features of MRFE6VP6300H includes:
MRFE6VP6300H can be used in a push-pull or single-ended configuration
MRFE6VP6300H feature innovative electrostatic discharge (ESD) protection

Package: compact air cavity ceramic NI780-4 package
Availability: Now in samples and volumes in 4th quarter of 2010

In a another separate release Freescale Semiconductor has announced that it has entered the gallium arsenide (GaAs) Monolithic Microwave Integrated Circuit (MMIC) marketplace with the introduction of four new devices to work as low-noise amplifiers and transmit power amplifiers in macro base stations, repeaters and femtocells employed in wireless networks.

Freescale says it holds numerous GaAs-related patents, and was one of the first companies to develop devices based on GaAs technology. The company's growing family of general-purpose amplifiers (GPAs) based on InGaP heterojunction bipolar transistors (HBTs) and GaAs heterojunction field effect transistors (HFETs) covers a broad array of RF and microwave applications.

"Freescale's high performance MMIC devices offer comprehensive RF active solutions for applications requiring high performance such as 3G and 4G cellular base stations, repeaters and femtocells," said Gavin P. Woods, vice president and general manager of Freescale's RF Division. "We developed the new MMIC products with the same standards as our advanced LDMOS RF technology in terms of quality and reliability. Our GaAs MMICs also come with the software and hardware tools necessary to extract optimal performance with minimal overhead costs."

The four new MMICs are:

MML09211H: An enhancement-mode pHEMT MMIC low-noise amplifier for applications such as W-CDMA base stations in the 865 - 960 MHz band to the high-datarate networks currently being implemented in the 728 - 768 MHz band. Key features are low noise figure of 0.6 dB including circuit losses, and supports operation from 400 to 1400 MHz. Small-signal gain is 20 dB at 900 MHz, P1dB output power is 21 dBm, isolation is - 35 dB, and third order output intercept point (IP3) is 32 dBm at 900 MHz.

MMA20312B: Is a two-stage InGaP HBT power amplifier designed for use in wireless base stations as well as repeaters and femtocells. The amplifier covers 1800 to 2200 MHz, delivers P1dB output power of 31 dBm at 2140 MHz and small-signal gain of 26 dB.

MMG15241H: Is a pHEMT device that covers 500 to 2800 MHz, with a noise figure of 1.6 dB at 2140 MHz, P1dB output power of 24 dBm, IP3 of 39 dBm, and small-signal gain of 15 dB.

MMG20271H: Is a low-noise amplifier covers 1500 to 2400 MHz, with a noise figure of 1.8 dB at 2140 MHz, P1dB output power of 27 dBm, IP3 of 42 dBm, and small-signal gain of 15 dB.

Availability: Limited sampling by June 2010 and general sampling by August 2010.

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Noise temperature, Noise Figure and Noise Factor


Noise temperature, Noise Figure and Noise Factor

Noise temperature, Noise Figure and Noise Factor

The basic formulae are:

Noise temperature (T) = 290 * (10^(Noise Figure/10)-1) K

Noise Figure (NF) = 10 * log (Noise factor) dB

Note that log must be to base 10. When using calculators and spreadsheets make sure that base 10 is selected. As a test, 10 * log(2) should give an answer of +3 dB. Noise temperature is measured in units called Kelvin (K) and these are like Celsius (C) temperature degrees but start at zero for absolute zero temperature so

0 K = -273 deg C

273 K = 0 deg C (ice melts)

290 K = 17 deg C (ambient temperature of a waveguide, for example)

Table to convert Noise Figure (NF) to Noise Temperature (T). This is useful for working out LNA or LNB noise temperatures from advertised Noise Figures.

NF(dB) T (K) NF(dB) T (K) NF(dB) T (K) NF(dB) T (K)
0.1 7 1.1 84 2.1 180 3.1 302
0.2 14 1.2 92 2.2 191 3.2 316
0.3 21 1.3 101 2.3 202 3.3 330
0.4 28 1.4 110 2.4 214 3.4 344
0.5 35 1.5 120 2.5 226 3.5 359
0.6 43 1.6 129 2.6 238 3.6 374
0.7 51 1.7 139 2.7 250 3.7 390
0.8 59 1.8 149 2.8 263 3.8 406
0.9 67 1.9 159 2.9 275 3.9 422
1.0 75 2.0 170 3.0 289 4.0 438

Procedure for adding up noise temperatures for antenna, waveguide, LNA, cable and indoor receiver in series:

System noise temperature (T system) is referred to the input of the LNA.
Antenna noise temperature is referenced to the flange specified by the manufacturer.
The calculations below assume you add some length of waveguide between the above flange and the LNA.
The noise temperature of the LNA refers to the input of the LNA.
The noise temperature of the cable after the LNA refers to the input of the cable.
The noise temperature of the receiver refers to the input of the receiver.

You need to convert gains in dB to numbers. Number = 10 ^(dB/10)
T system = Noise contribution from antenna = Antenna noise temp * waveguide gain
+ noise contribution of the waveguide = 290 * (1-waveguide gain)
+ noise contribution of the LNA = the LNA noise temp
+ noise contribution of the cable = cable noise temp / LNA gain
+ noise contribution of the indoor receiver = indoor receiver input noise temp / (LNA gain * cable gain)

Example: Antenna noise temperature = 35 K (mainly ground pick up noise)
Waveguide feeder gain = -0.25 dB (0.944), temperature = 290K
LNA gain = 50 dB (100000), input noise temperature = 75 K
Cable loss or attenuation = 20 dB or cable gain = -20 dB (0.01)
Cable noise temp= 290 K
Indoor receiver noise figure = 9 dB
Indoor receiver input noise temperature = 290 * (10^(9/10)-1) = 2013.5519 K

Tsystem = 35 * 0.944 = 33 Noise contribution of the antenna
+ 290 ( 1 - 0.944) = 16 Noise contribution of the waveguide
+ 75 Noise contribution of the LNA
+ 290/100000 = 0.0029 Noise contribution of the cable *
+ 2013.5519/(100000 * 0.01) = 2.0135519 Noise contribution of the indoor receiver
= 126.0164519 K

* The spurious precision in the above lines is to help resolve discrepancies in the last two calculations.
Different calculation methods give slightly different results. 25 March 2007. More ideas welcome please on the controversial cable noise contribution calculations.

Note that LNA noise temperature, the antenna noise temperature and waveguide loss are the main factors.

Some examples of antenna noise temperature versus elevation angle are shown on page antnoise.htm

To calculate the G/T of a receive system : G/T = Receive gain in dBi - 10 log ( system noise temperature T ).

Specialized avalanche photodiode arrays enable adaptive optics uses




Specialized avalanche photodiode arrays enable adaptive optics uses

Specialized avalanche photodiode arrays enable adaptive optics usesThe Advanced Imaging Technology Group at Lincoln Laboratory has fabricated arrays of new high-fill-factor Geiger-mode avalanche photodiodes (GM-APDs) for application as optical wavefront sensors. High-quality wavefront sensors are key enablers for laser communications and high-resolution astronomy. GM-APDs differ from conventional photodetectors because they produce a digital pulse in response to a single incoming photon. This capability eliminates analog circuit readout noise and enables sensitive photon counting.

Lincoln Laboratory previously applied GM-APDs to laser radar and imaging applications; however, those devices had relatively low fill factor and were therefore unsuitable for applications as a wavefront sensor. A wavefront sensor converts the incoming light wave to an array of light spots whose locations indicate the wavefront's shape. A high-fill-factor detector array is needed to measure the locations of these light spots.

This new array consists of 2 × 2 subarrays of detectors, known as quad cells, each with high fill factor. Any photoelectron originating in the interior region of a quad cell is collected and detected by the closest APD. Each APD is connected to a digital pixel circuit that counts the detection events. The fact that no photoelectrons are "lost" between diodes enables use of these specialized arrays in adaptive optics systems. The four count values can be used to compute the displacement of the light spot from the center of the quad cell.

This is a false-color contour plot of the total number of detection events from all four detectors in a quad cell as a function of the location of a small light spot. (Red denotes high counts; blue, low counts.) Photoelectrons incident on the boundary areas between adjacent APD regions are collected and detected smoothly, demonstrating that this design is well suited for wavefront sensor use.

The high-fill-factor arrays will eventually be used in laser-guide-star adaptive optics in which a laser serves as an artificial star, providing a reference point for astronomical imaging. This star can be positioned anywhere the telescope can point, opening up a greater area of the sky to adaptive optics.

MIT : Noise Processes in RF Integrated Circuits (Oscillators and Mixers)