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Ports and Signal Flow

Port types​

Every block has one or more ports. Port types determine how connections are made and how the analysis engine traverses the chain.

PortDirectionUsed by
INInputAmplifiers, filters, attenuators, ADC
OUTOutputAmplifiers, filters, attenuators, DAC, Signal Source, LO
RFDepends on modeMixer RF-side main-path port
IFDepends on modeMixer IF-side main-path port
LOInputMixer (LO drive enters here)

Main signal path​

The analysis engine traces the main signal path by following:

  • OUT → IN connections between amplifiers, filters, and passive blocks
  • in TX mode, signal enters the mixer on IF and leaves on RF
  • in RX mode, signal enters the mixer on RF and leaves on IF

The main path starts at a boundary source such as Signal Source, DAC, or Antenna, and ends at a boundary sink such as ADC, Output, or Antenna, depending on the chain direction.

LO path​

The LO path is a separate branch:

  • A Local Oscillator block connects its OUT port to the mixer's LO port
  • This connection is shown on the canvas as a separate edge (typically entering from below)
  • The LO block and its connections are excluded from the cascade

The analysis engine does not include LO blocks in gain, NF, or linearity calculations. LO parameters (frequency, power, phase noise) are tracked separately for documentation purposes.

Why LO blocks are excluded​

The LO is a support signal, not the signal being processed. Its job is to complete the relation between the signals Intermediate and Radio Frequencies. It is also used to calculate Image frequencies and Mixing Products in the Frequency Planning tab.

Multi-port blocks: mixer details​

The mixer is the only block with three ports

The main signal path through a mixer depends on the operating mode:

  • TX mode: IF → MIXER → RF
  • RX mode: RF → MIXER → IF

Valid connections to a Mixer:

  • A main-path block connected to the mixer's active input for the current mode
  • Local Oscillator block's OUT port → Mixer LO port
  • The Mixer's active output for the current mode → any compatible downstream block