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PI4DQPSK_ModTuned (PI-4 DQPSK Modulator, Tuned)


Available in ADS

Parameters

Name

Description

Units

Default

Fnom

Nominal input frequency

GHz

1

Rout

Output resistance

Ohm

50

SymbolRate

Output symbol rate (1/2 input bit rate)

kHz

24.3

Delay

Sampling delay

nsec

50

Notes/Equations
  1. This tuned PI/4 DQPSK modulator selects the input harmonic closest to the specified Fnom frequency and modulates it according to the phase state determined by differentially encoding the input bit stream and applying the PI/4 phase offset.
    If there is no analysis harmonic frequency close enough to the Fnom frequency, a warning is issued and the output is 0. The input bit stream is sampled at a rate determined by the SymbolRate with an initial synchronizing delay determined by the Delay parameter. The actual sampling rate is rounded to an integer multiple of the system timestep-use a corresponding discrete time source to generate this serial bit stream or ensure that the analysis sampling rate is an integer multiple of the bit rate. Two consecutive bits are monitored, along with the previous phase state, to determine the next phase state. An input bit is assumed to be 1 if it is greater than 0.5V and 0 otherwise.
  2. The RF carrier is injected at pin 1; the input bit stream is injected at pin 3. The resulting PI4DQPSK signal is present at pin 2. The RF carrier should be a frequency-domain source; the modulating signal should be a time-domain source.
  3. The input impedances of both the serial bit stream input and the RF carrier are infinite; output impedance is set by Rout, and is limited to a minimum value of 0.1 Ohm. The open circuit output voltage is defined by:

    where
    k represents the value at the analysis harmonic frequency closest to the Fnom value

    Phase Transition = Next Phase − Current Phase

    0

    0

    45°

    0

    1

    135°

    1

    0

    −45°

    1

    1

    −135°

  4. This model will not function as a modulator in transient and baseband envelope simulations because of the use of complex exponential functions.
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