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Peak Program meter and AM Transmitter by TamirS

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Peak Program meter and AM Transmitter

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									             1- Peak Program Meter
                 2- AM Transmitter
                               Tamir Suliman
Milos Dorolosovaki
                                 May 2009
                                  ECE 294
Peak Program Meter
    What's Peak Program Meter
• A Peak Program Monitor (PPM), sometimes
  referred to as a Peak Reading Meter (PRM), is
  an audio metering device except its capable of
  reading accurate signal peak level compared
  to the regular volume meter .
           Peak Program Meter
• Volume unit VU Meters show you the average
  level of the signal- so they're great for recording
  to analog tape or for mastering purposes where
  you want to know the overall general level of the
  signal.
• VU Meters are bad at telling you the peak level
  of the signal. This paper focuses on the design
  and the implementation of a peak program
  meter, which features a data-acquisition system,
  using a C6713 DSP-based starter kit (DSK).
          Peak Program Meter
• PPM improves on the VU meter’s performance
  problems by integrating the signal for small
  time . this integration process will then only
  detects peaks that are long enough to be
  heard by typical human listener.
          Peak Program Meter
• The primary function of this program is to detect
  and provide an LED indication /warning whenever
  an output value is approaching the range limit of
  the DAC.
• These condition are checked every Ts =1/Fs, a
  dwell time is required to maintain the ON status
  of each of LEDs without this dwell time the LED
  would cycle on/off too rapidly to be visible. The
  output value s above which an LED turns ON
  were chosen to be .
          Peak Program Meter
• These turn on levels are shown the Figure
  below , where the sinusoidal signal is at the
  maximum amplitude for the DAC.
Peak Program Meter
         PPM Implementations
• The output value s above which an LED turns
  ON were chosen to be
• +/- (28000,3200,32767)
• These turn on levels are shown the Figure
  below , where the sinusoidal signal is at the
  maximum amplitude for the DAC.
• Reset value is 4800 which turns the LED off
  after "RESET" number of samples
• ScaleFactor = 1.0
PPM-Movie
                       WHY PPM
• An alternative to VU meters Peak Program Meters have fast
  rise times (30 times faster than VU meters)
• PPM has much slower fallback or decay time.
• PPM responds to peak levels rather than average levels.
  This makes them especially useful in situations where
  distortion or overload is a significant concern, as in digital
  applications. Because other meters, (i.e. VU meters)
  respond more slowly, giving an average level reading, they
  are not as useful for indicating maximum levels or peaks.
• Popular and tested in Europe, PPMs are found in
  mechanical, LED, and/or plasma forms in a variety of
  equipment types.
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AM Transmitter
             AM Transmitter
• One of the simplest modulation schemes is
  Amplitude Modulation, which is normally just
  abbreviated as AM.
• For several decades commercial AM radio
  broadcasts is used on many consumer radios in
  most of the countries around the world.
• AM provides an easily understood modulation
  scheme that can be thought as the starting point
  for many of today’s more complicated
  modulation schemes.
             AM Transmitter
• A.M works by varying the strength of the
  transmitted signal in relation to the
  information being sent. For example, changes
  in the signal strength can be used to reflect
  the sounds to be reproduced by a speaker, or
  to specify the light intensity of television
  pixels.
     FORMS of AM Modulation
• Conventional amplitude modulation (AM) (also
  known as double sideband (DSB) with carrier)
• Single sideband (SSB)
• Double sideband suppressed carrier (DSB-SC).
                  AM-DSB
• In the basic form Amplitude modulation
  produces a signal with power concentrated at
  the carrier frequency and in two adjacent
  sidebands.
• Each sideband is equal in bandwidth to that of
  the modulating signal and is a mirror image of
  the other.
             Single Side Band
• Single-sideband modulation (SSB) is a refinement
  of amplitude modulation that more efficiently
  uses electrical power and bandwidth.
• Amplitude modulation produces a modulated
  output signal that has twice the bandwidth of the
  original baseband signal.
• Single-sideband     modulation      avoids   this
  bandwidth doubling, and the power wasted on a
  carrier.
     Producing Single Side Band
• Filtering, leaving only either the upper
  sideband (USB) or less commonly the lower
  sideband (LSB).
• Most often, the carrier is reduced or removed
  entirely (suppressed), being referred to in full
  as single sideband suppressed carrier
  (SSBSC).
             Single Side Band
• Hartley modulator
• Two versions of the original signal are
  generated, mutually 90° out of phase.
• Each one of these signals is then mixed with
  carrier waves that are also 90° out of phase
  with each other.
• By either adding or subtracting the resulting
  signals, a lower or upper sideband signal
  results.
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