Kamis, 31 Mei 2012

Nama Kelompok

Kelas TI6A:
Tony Soekirman                    [09420415]
Masjumansyah Eka Nurmaidi         [09420392]
Dedyanto                          [09420350]
Davis                             [09420349]
Vivieyanti                        [09420417]

Senin, 28 Mei 2012

LT5503 - 1.2GHz to 2.7GHz Direct IQ Modulator and Mixer

Features

  • Single 1.8V to 5.25V Supply
  • Direct IQ Modulator with Integrated 90° Phase Shifter*
  • Four Step RF Power Control
  • 120MHz Modulation Bandwidth
  • Independent Double-Balanced Mixer
  • Modulation Accuracy Insensitive to Carrier Input Power
  • Modulator I/Q Inputs Internally Biased
  • Available in 20-Lead FE Package

Typical Application

LT5503 Typical Application
LT5503 Typical Application

Description

The LT5503 is a front-end transmitter IC designed for low voltage operation. The IC contains a high frequency quadrature modulator with a variable gain amplifier (VGA) and a balanced mixer. The modulator includes a precision 90° phase shifter which allows direct modulation of an RF signal by the baseband I and Q signals.

In a superheterodyne system, the mixer can be used to generate the high-frequency RF input for the modulator by mixing the system’s 1st and 2nd local oscillators.

The LT5503 modulator output P 1dB is –3dBm at 2.5GHz. The VGA allows output power reduction in three steps up to 13dB with digital control. The baseband inputs are internally biased for maximum input voltage swing at low supply voltage. If needed, they can be driven with external bias voltages.

Applications

  • IEEE 802.11 DSSS and FHSS
  • High Speed Wireless LAN (WLAN)
  • Wireless Local Loop (WLL)
  • PCS Wireless Data
  • MMDS
Sumber: http://www.linear.com/product/LT5503

Multiphysics Simulations of Tunneling Current Modulation using Ultra-Thin Membranes Micromachined on SOI

B. Bercu, L. Montès, G. Bacles, J. Zimmermann, and P. Morfouli
Institute of Microelectronics, Electromagnetism and Photonics, Grenoble

In this paper, we study a novel type of NEMS - tunnel junctions mounted on thin membranes.

Mechanical stress applied to the junction induces changes in the height and length of the barrier, allowing the modulation of the tunnelling current

 
Measument of the deformation of an ultra-thin silicon membrane
.

Download

Sumber: http://www.comsol.com/papers/1576/

Introduction to VEDA: Virtual Environment for Dynamic AFM

Amplitude Modulated Scanning Simulation Tool

screencapture
If you have not already done so, please launch this simulation tool (check the list of running simulation sessions below). It will open up in a separate window. Use the simulation tool to follow along each example by setting the parameters presented. Pause the presentation as needed to get a good understanding of how the tool works.

Launch tool



Sumber: http://nanohub.org/resources/2754?resid=3175

RF Simulation Demo: Amplitude Modulation

Amplitude Modulation (AM) is an analog modulation scheme where the amplitude (A) of a fixed-frequency carrier signal is continuously modified to represent data in a message.  The carrier signal is generally a high frequency sine wave used to “carry” the information on the envelope of the message.  The result is a double-sideband signal, centered on the carrier frequency, with twice the bandwidth of the original signal.
The following algorithm is commonly used to represent amplitude modulation:
Gathering like terms and simplifying the equation leaves:
y(f) = (C + Msin(ωmt + φ))sin(ωct)
The main advantage of using AM modulation is that it has a very simple circuit implementation (especially for reception), creating widespread adoption quickly.  AM modulation however wastes power and bandwidth in a signal.  The carrier requires the majority of the signal power, but actually does not hold any information.  AM uses twice the required bandwidth by transmitting redundant information in both the upper and lower sidebands.

Programming:

The following steps describe how to build a VI which implements the longer of the two equations shown above for Amplitude Modulation.  Open the “AM Modulation – Medium Exercise.vi”.  Inspect the front panel and block diagram that has already been created for you.  When this VI is completed, you will be able to select the amplitude and frequency of both the carrier and data signals as well as see the time and frequency domain representation of the signals.  The graphs display the behavior of the carrier and sideband signals as modulation parameters (amplitude and frequency) change.  The following front panel represents the operation of a completed VI:
The block diagram consists of a while loop which contains various controls and graphs to display and control the AM signal component information.
1)  Place an “Add” and “Subtract” VI on the block diagram.  Wire the “Carrier Frequency” and “Modulation Frequency” slider controls into the add function.  Wire the  “Carrier Frequency” into the top connector on the subtract function and “Modulation Frequency” into the bottom connector to subtract the two values.
2)  Place a “Simulate Signal” Express VI on the bock diagram.  A dialog box will open to configure the function.  Select the signal type to be a sine wave, set the frequency to 10 Hz, and the amplitude to 1 volt.  Increase the samples per second to be 100000. Deselect the option to automatically select the number of samples, and set the value to also be 100000.  Once you have finished, the dialog box should resemble the image below:
Select the “OK” button.   LabVIEW will now generate all of the code required for this function.  Make three copies of the function by selecting the VI on the block diagram and holding CTRL while dragging the cursor to an open area.  For the first Simulate Signal VI, wire the Carrier Amplitude into amplitude input and Carrier Frequency into frequency input.  For the second Simulate Signal VI, wire the output of the add function into the frequency input. Wire a constant value of 1 into the amplitude input by right-clicking on the connector and selecting “Create>>Constant”.  For the third Simulate Signal VI, wire the output of the subtract function into the frequency input.  Again, wire a constant value of 1 into the amplitude input by right-clicking on the connector and selecting “Create>>Constant”.
3)  Place a “Multiply” VI on the block diagram.  Wire the sine wave outputs of the second and third Simulate Signal VIs into the multiply function.  Wire the output of the Multiply function into the Modulated Signal graph.  Also, wire the output of the first Simulate Signal VI into the Carrier Signal graph.
4)  Place a “Divide” VI on the block diagram.  Right-click on the lower input connector and create a constant value of 2.  Highlight the constant and the divide function on the block diagram and make a copy by holding CTRL while dragging the cursor to an open area.  Wire the input of one of the divide functions to the output of the second Simulate Signal VI.  Wire the input of the other divide functions to the output of the third Simulate Signal VI.
5)  Place two “Multiply” VIs on the block diagram.  Wire the Modulation Amplitude control and the output of one of the divide functions into the first multiply function.  Wire the output of the second Divide function and the Modulation Amplitude control into the second multiply function.
6)  Place a “Subtract” VI on the block diagram and wire the outputs of both of the multiply functions from the last step into the inputs.  Connect the inputs so the data from the second Simulate Signal VI is being subtracted from the third Simulate Signal VI.
7)  Place an “Add” VI on the block diagram and wire the output of the subtract function from the last step into the function.  Also wire the output from the first Simulate Signal VI into the add function.
8)  Place a “Spectral Measurements” Express VI on the block diagram.  A dialog box will open to configure the function.  Select the spectral measurement to be magnitude (peak) in dB.  Set the Window to be “7 Term B-Harris” (do not enable averaging).  Once you have finished, the dialog box should resemble the image below:
Select the OK button.  LabVIEW will now generate the code for the function.   Wire the output of the add function from the previous step in the signals input connector.  Also wire the output of the add function to the AM Modulated Signal (Time Domain) graph.  Finally wire the output of the Spectral Measurements Express VI to the AM Modulated Signal (Frequency Domain) graph.
Your VI is now complete.  The block diagram of the completed program should resemble the image below.  Press the run icon to execute your VI.  Vary the values for the carrier and modulation amplitude and frequency to see the effect it has on the signal.

Requirements


Filename: am_modulation.vi

Software Requirements


Application Software: LabVIEW Full Development System 7.1

Sumber: http://zone.ni.com/devzone/cda/epd/p/id/5146

Coded Modulation Systems

Coded Modulation Systems is an introduction to the subject of coded modulation in digital communication. It is designed for classroom use and for anyone wanting to learn the ideas behind this modern kind of coding. Coded modulation is signal encoding that takes into account the nature of the channel over which it is used. Traditional error correcting codes work with bits and add redundant bits in order to correct transmission errors. In coded modulation, continuous time signals and their phases and amplitudes play the major role. The coding can be seen as a patterning of these quantities. The object is still to correct errors, but more fundamentally, it is to conserve signal energy and bandwidth at a given error performance. The book divides coded modulation into three major parts. Trellis coded modulation (TCM) schemes encode the points of QAM constellations; lattice coding and set-partition techniques play major roles here. Continuous-phase modulation (CPM) codes encode the signal phase, and create constant envelope RF signals. The partial-response signaling (PRS) field includes intersymbol interference problems, signals generated by real convolution, and signals created by lowpass filtering. In addition to these topics, the book covers coding techniques of several kinds for fading channels, spread spectrum and repeat-request systems. The history of the subject is fully traced back to the formative work of Shannon in 1949. Full explanation of the basics and complete homework problems make the book ideal for self-study or classroom use.

Sumber: http://www.springer.com/engineering/signals/book/978-0-306-47279-4

MODULATION SYSTEMS

modulation is applied. The FCC defines HIGH-LEVEL MODULATION in the Code of Federal Regulations as "modulation produced in the plate circuit of the last radio stage of the system." This same document defines LOW-LEVEL MODULATION as "modulation produced in an earlier stage than the final." Q-36.   What is percent of modulation? Q-37.   With a single modulating tone, what is the amplitude of the sideband frequencies at 100-percent modulation? Q-38.   What is the formula for percent of modulation? Q-39.   What is high-level modulation? MODULATION SYSTEMS To complete your understanding of AM modulation, we are now going to analyze the operation of a typical plate modulator. Detailed circuit descriptions will be used to give you an understanding of a basic AM plate modulator. In addition, we will cover basic circuit descriptions for cathode and grid electron- tube modulators and for base, emitter, and collector transistor modulators in this chapter. Plate Modulator Figure 1-45 is a basic plate-modulator circuit. Plate modulation permits the transmitter to operate with high efficiency. It is the simplest of the modulators available and is also the easiest to adjust for proper operation. The modulator is coupled to the plate circuit of the final rf amplifier through the modulation transformer. For 100-percent modulation, the modulator must supply enough power to cause the plate voltage of the final rf amplifier to vary between 0 and twice the dc operating plate voltage. The modulator tube (V2) is a power amplifier biased so that it operates class A. The final rf power amplifier (V1) is biased in the nonlinear portion of its operating range (class C). This provides for efficient operation of V1 and produces the necessary heterodyning action between the rf carrier and the af modulating frequencies.

sumber: http://electriciantraining.tpub.com/14184/css/14184_66.htm