Audio production can involve the use of many components, including microphones, wireless audio transmitters, wireless audio receivers, recorders, and/or mixers for capturing, recording, and presenting the sound of productions, such as television programs, newscasts, movies, live events, and other types of productions. The microphones typically capture the sound of the production, which is wirelessly transmitted from the microphones and/or the wireless audio transmitters to the wireless audio receivers. The wireless audio receivers can be connected to a recorder and/or a mixer for recording and/or mixing the sound by a crew member, such as a production sound mixer. Electronic devices, such as computers and smartphones, may be connected to the recorder and/or mixer to allow the crew member to monitor audio levels and timecodes.
Wireless audio transmitters, wireless audio receivers, wireless microphones, and other portable wireless communication devices include antennas for transmitting and receiving radio frequency (RF) signals which contain digital or analog signals, such as modulated audio signals, data signals, and/or control signals. Users of portable wireless communication devices include stage performers, singers, actors, news reporters, and the like.
A wireless audio transmitter may transmit an RF signal that includes an audio signal to a wireless audio receiver. The wireless audio transmitter may be included in a wireless handheld microphone, for example, that is held by the user and includes an integrated transmitter and antenna. When the RF signal is received at the wireless audio receiver, the RF signal may be degraded due to multipath fading caused by constructive interference and/or by other types of interference. This degradation may cause the RF signal to have a poor signal-to-noise ratio (SNR), which can result in bit errors that can cause audio artifacts and muting of the resulting output audio. However, muting the output audio is undesirable in many situations and environments, such as during professional stage productions and concerts. The effects of such multipath fading and interference are most prevalent in harsh RF environments where physical and electrical factors influence the transmission and reception of RF signals, e.g., movement of the microphone within the environment, other RF signals, operation in large venues, etc.
To alleviate issues with multipath fading of RF signals, wireless audio components may utilize frequency diversity and/or antenna diversity techniques. In particular, wireless audio transmitters may utilize frequency diversity to simultaneously transmit on one antenna two RF signals of two separate frequencies in a combined RF signal, where the two RF signals both include the same audio signal. A wireless audio receiver may then use one or both of the underlying RF signals. In addition, wireless audio receivers may utilize antenna diversity to simultaneously receive RF signals from a wireless audio transmitter on multiple antennas. The received RF signals can be combined to produce a single audio output.
In some cases, a two antenna system may not be sufficient to provide adequate performance. More than two antennas may be desired in order to benefit from the user of antennas with different directional gains so that the coverage of the wireless system is extended. For example, a particular venue may have multiple “zones” that need to be covered by a single wireless receiver and/or a venue may be very large. In these situations, having more than two antenna locations may result in improved coverage and reduced transmitter to antenna distances. As such, a traditional two antenna diversity may not provide adequate performance.
When utilizing frequency diversity and/or antenna diversity techniques, existing wireless audio receivers typically combine multiple RF signals received on multiple antennas by scaling each RF signal proportionally using maximal-ratio combining (MRC) under the assumption that there is equal noise power in each RF signal. However, if the antennas are subjected to asymmetrical noise, e.g., when one antenna is closer to a source of interference, then MRC does not maximize the signal-to-noise ratio of the combined signal. This can cause the receiver to produce non-optimal audio output, such as degraded sound or muting. In addition, existing wireless audio receivers may need additional components and complex arrangements in certain situations and environments. For example, if more than two antennas are utilized, external antennas combiners and external switches may be needed.
Accordingly, there is an opportunity for a multi-channel wireless audio receiver system that addresses these concerns. More particularly, there is an opportunity for a multi-channel diversity wireless audio receiver system that provides flexible routing of multiple RF signals in different selectable modes, and low latency uninterrupted reception of signals in harsh RF environments by combining multiple RF signals to maximize signal-to-noise ratio. Furthermore, there is an opportunity for a multi-channel diversity wireless audio receiver system that provides performance benefits when high-order modulation scheme (such as 16-QAM and 64-QAM) are utilized that have higher RF sign-to-noise ratio requirements.