Block Components
Every block in a chain has a component that defines its function, port types, and which parameters apply to it. Components are grouped into four categories.
LO blocks
LO (local oscillator) blocks are support blocks — they connect to the LO port of a mixer but are not part of the main signal path. The cascade analysis excludes LO blocks from all gain, NF, and linearity calculations.
Active blocks
Active blocks add gain (or conversion gain) to the signal.
| Component | Ports | Typical use |
|---|---|---|
| Low Noise Amplifier | IN, OUT | First gain stage in RX chain; low noise figure is critical |
| Power Amplifier | IN, OUT | Final gain stage in TX chain; high output power |
| Driver | IN, OUT | Pre-PA stage; drives the PA to its operating point |
| Amplifier | IN, OUT | Generic gain stage |
| Variable Gain Amplifier | IN, OUT | Variable gain amplifier |
| Buffer | IN, OUT | Isolation or impedance buffering; typically unity gain |
| Mixer | RF, LO, IF | Frequency conversion between RF and IF |
Passive blocks
Passive blocks attenuate the signal (negative gain = insertion loss).
| Component | Ports | Typical use |
|---|---|---|
| Bandpass Filter | IN, OUT | Channel selection, image rejection |
| Highpass Filter | IN, OUT | LO feedthrough rejection, DC blocking |
| Lowpass Filter | IN, OUT | Anti-alias, harmonic rejection |
| Bandstop Filter | IN, OUT | Notch filter, interference rejection |
| Attenuator | IN, OUT | Fixed resistive pad |
| DSA | IN, OUT | Digitally switched attenuator; variable attenuation |
| Isolator | IN, OUT | One-way transmission; high reverse isolation |
| Phase Shifter | IN, OUT | Phase control; may have insertion loss |
| Limiter | IN, OUT | Overdrive/ESD protection; clamps high input signals |
Boundary blocks
Boundary blocks mark the entry and exit points of the chain.
| Component | Ports | Typical use |
|---|---|---|
| DAC | OUT | TX chain source; sets the initial signal level |
| ADC | IN | RX chain endpoint |
| Signal Source | OUT | Generic RF source (antenna, test generator) |
| Antenna | RF | RF boundary for over-the-air input or output |
| Output | IN | Marks the chain endpoint (antenna, load) |
Support blocks
| Component | Ports | Notes |
|---|---|---|
| Local Oscillator | OUT | Local oscillator. Connects to mixer LO port only. Excluded from cascade. |
Port types reference
| Port | Signal type | Carries |
|---|---|---|
IN | RF/IF signal | Main signal path input |
OUT | RF/IF signal | Main signal path output |
RF | RF signal | Mixer RF-side main-path port |
IF | IF signal | Mixer IF-side main-path port |
LO | LO drive | Local oscillator drive to mixer |
For mixers, RF and IF swap main-path direction between TX and RX modes. See Ports & Signal Flow for examples.