Source: https://hackaday.com/2018/08/11/signal-generator-uses-fpga/

Although there are a few exceptions, FPGAs are predominantly digital devices. However, many FPGA applications process analog data, so you often see an FPGA surrounded by analog and digital converters. This is so common that Opal Kelly — a producer of FPGA tools — launched the SYZYGY open standard for interconnecting devices like that. [Armeen] — a summer intern at Opal Kelly — did a very interesting open source FPGA-based signal generator using a Xilinx FPGA, and a SYZYGY-compliant digital to analog converter.

Verilog code (available on GitHub) shows a lot of interesting things
Following how the AM and FM generation works is a great introduction to signal synthesis in an FPGA.

High Performance FPGA-Based Signal Generator using the XEM7320, FrontPanel, and SYZYGY DAC
https://www.opalkelly.com/high-performance-fpga-based-signal-generator-using-the-xem7320-frontpanel-and-syzygy-dac/

SYZYGY is intended to fill the need for a compact, low cost, low pin-count, high-performance connectivity solution between FPGAs and single-purpose hardware peripherals.

Until now, the FPGA landscape has enjoyed limited options when it comes to connecting peripherals into FPGA systems. In the case of low-speed peripherals in the 1 to 50 MHz range, we have Digilent’s Pmod standard. The 6-and 12-pin Pmod connectors are inexpensive to implement, and the cost of the peripherals — of which there are many off-the-shelf offerings — is around $8 to $50.

By comparison, when it comes to high-performance peripherals with data rates up to 10 Gbps, we find the ANSI/VITA standard known as FMC (FPGA Mezzanine Card). In this case, the 72-pin and 200-pin connectors are more expensive, and the peripherals themselves can cost anywhere from a couple of hundred dollars to thousands of dollars.

Opal Kelly, known for providing a range of powerful USB and PCI Express FPGA-based Integration Modules that connect a user’s hardware design implemented in an FPGA to the user’s software implemented on a PC, is shaking things up.

the company just announced the release of SYZYGY, a new open standard for connecting high-performance peripherals to FPGA hardware.

The SYZYGY specification defines two connector types: Standard and Transceiver. The Standard SYZYGY connector offers up to 28 single-ended, impedance-controlled signals, 16 of which may be defined as differential pairs for interface standards such as LVDS. The Transceiver SYZYGY connector boasts four lanes of Gigabit-class transceiver connections and also offers up to 18 single-ended signals.