Abstract
The transmitter (a rack unit, “the rack”) has one clock-source setting, chosen by the operator and persisted with a boot default: internal, or any digital input module that recovers a clock (a console’s personal-monitor link, AES50, an A2B console link, an audio network module, word clock). The radio keeps its own clean reference (a TCXO on the radio module), which sets the carrier frequency. The carrier is never derived from the console’s clock and never moves with it. No reference-clock line runs from the host to the radio. With the internal clock selected, the rack’s own audio clock is steered to the radio’s bit clock by holding the backlog of the buffer between audio capture and the radio at a target. Audio and air are one clock domain, set by the radio’s TCXO. With a console or other external clock selected, the audio side runs on that clock, and the rack instead trims the radio’s symbol (data) rate with a slow loop, using the transceiver’s numerically controlled data-rate setting. The loop measures the transmit backlog, or counts the radio’s bit-clock edges against the audio clock. On the example transceiver the data-rate register holds symbol rate times transmit oversampling ratio as an integer; at 495 ksym/s and an oversampling ratio of 10, one count is about 0.2 ppm of symbol rate. The air’s symbol and block rate then equals the console’s rate while the carrier stays on the TCXO.
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Recommended Citation
Anonymous, "Wireless audio air rate following an external clock by symbol-rate trim: a transmitter whose radio keeps its own clean reference for the carrier while a slow loop trims the radio's numerically controlled symbol rate to an operator-selected console clock, with per-input lock indication and receivers that follow the air rate by trimming their own DAC clock, so that no sample-rate conversion occurs in the normal path", Technical Disclosure Commons, ()
https://www.tdcommons.org/dpubs_series/12145