522 Double Balanced Mixer and Quadrature Divider
522 : Double Balanced Mixer and Quadrature Divider
- Author: Bruce MacKinnon
- Description: Takes an RF input (with DC bias) and a digital LO signal and mixes to provide a differential IF output. Simulated at 7 MHz.
- GitHub repository
- Clock: 0 Hz
Overview
The project name notwithstanding, this is a simple double-balanced RF mixer for the HF frequency range (around 7 MHz). The design is a switching mixer, so the local oscillator (LO) clock is a digital signal.
The RF input should be DC biased. Expected bias is around 0.6 volts.
A differential IF output is provided. The IF output should be the difference of IFOUT_P and IFOUT_N.
The detailed document here gets into the mathematical basis for the circuit design used.
The tile also has a simple digital component called a quadrature divider. This takes a digital clock and creates two output clocks with quadrature relationship (90 degrees of phase difference). This would be useful for certain types of RF modulators and demodulators.
The mixer and the quadrature divider are entirely independent circuits at this time.
Pinouts
- ua[0] - Analog RF input with DC bias.
- ua[1] - Analog IF output (positive phase)
- ua[2] - Analog IF output (negative phase)
- uio_in[0] - Digital local oscillator (LO) input.
- uio_in[1] - Digital clock input for quadrature divider.
- uo_out[0] - Digital quadrature divider output, I phase.
- uo_out[1] - Digital quadrature divider output, Q phase.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | Local Oscillator input for mixer | I phase output from quadrature divider | |
| 1 | Clock input for quadrature divider | Q phase output from quadrature divider | |
| 2 | |||
| 3 | |||
| 4 | |||
| 5 | |||
| 6 | |||
| 7 |
Analog pins
ua | PCB Pin | Internal index | Description |
|---|---|---|---|
| 0 | B5 | 11 | RF input (with DC bias) |
| 1 | B0 | 6 | IF output (Positive phase) |
| 2 | B4 | 10 | IF output (Negative phase) |