Patent Application
20100218661
The present invention relates to a wireless receiver.
During concerts or an audio recording, wireless transmitters are often used in connection with musical instruments, like violins, guitars, bass guitars or the like. The sound produced by the music instruments are transmitted by means of the wireless transmitters to wireless receivers. The wireless receivers will forward the wireless transmitted audio signals to a subsequent audio processing.
Certain music instruments like string instruments, guitars, bass guitars, violins etc. must be tuned regularly, sometimes they even have to be retuned during concerts.
It is an object of the invention to provide a wireless receiver which enables an improved tuning of musical instruments.
This object is solved by a wireless receiver according to claim 1.
Therefore, a wireless receiver for receiving a wireless transmitted audio signal from a wireless transmitter is provided. The wireless receiver comprises a tuning assisting unit for assisting in the tuning of a music instrument coupled to the wireless transmitter. The tuning assisting unit indicates whether the audio signal from the music instrument corresponds to a specified frequency. The wireless receiver furthermore comprises an audio amplifier for amplifying the received audio signal. The wireless receiver furthermore comprises a housing which incorporates the tuning assisting unit and the audio amplifier.
According to a further aspect of the invention, the tuning assisting unit comprises an analog amplifier unit having at least one first and second operational amplifier, eight resistors and five capacitors.
According to a further aspect of the invention, the tuning assisting unit receives an analog signal of a music instrument as input signal and determines a corresponding digital signal, wherein the zero crossings of the input analog signal relate to the zero crossings of the output digital signal.
The invention relates to the idea to integrate a tuning assisting unit into a wireless receiver cooperating with a wireless transmitter which is coupled to a musical instrument. The tuning assisting unit is used to assist the tuning of a music instrument coupled to the wireless transmitter. A wireless receiver, which comprises a tuning assisting unit is advantageous as no cable needs to be provided between the wireless receiver and an external tuning device. Furthermore, as no cable needs to be provided, any possible operation error can be avoided. While in tuning units according to the prior art, a separate audio amplifier needs to be provided, integrated tuning units can also reuse the audio amplifier of the wireless receiver.
Further aspects of the invention are defined in the dependent claims.
Embodiments and advantages of the present invention will now be described in more detail with reference to the figures.
The music instrument can for example be a string instrument, a guitar, a bass guitar, a violin or any other music instrument which needs to be tuned.
The tuning assisting unit TU receives an analog signal from the music instrument (transmitted via the wireless transmitter and received by the wireless receiver) and converts the analog signal into a digital signal having high and low levels such that the output signal can be processed by a digital signal processor. The tuning assisting unit TU serves to remove the amplitude information but to maintain the zero crossings of the signal. Based on the zero crossings, the frequency of the signal can be determined. The output of the tuning assisting unit relates to the frequencies of the audio signal from the music instrument. However, it should be noted that the audio signal from the music instrument not only comprises the fundamental waves but also harmonics thereof. In a subsequent processing, the fundamental signal has to be determined even in the presence of the harmonics.
The input analog signal may comprise several fundamental signals and harmonics thereof.
The output signal OUT of the tuning assisting unit TU is a square wave signal.
The tuning assisting unit receives the analog signal from the music instrument as input signal and outputs a digital signal which peeks are compatible with a subsequent digital signal processor. The output signal of the tuning assisting unit TU has a low and a high level. The frequency information of the audio signal from the music instrument is present in the zero crossings. In other words, the time from a rising edge to the next rising edge will correspond to one period of the signal. As several harmonics may be present, a subsequent digital signal processor must determine which rising edges relate to a fundamental signal.
The output signal OUT of the tuning assisting unit TU is a square wave signal.
The wireless receiver can comprise a housing, a power supply unit, an audio processing unit, a processor and optionally a display. As mentioned above, the tuning assisting unit can be realised with eight resistors, five capacitors and two operational amplifiers or a double-operational amplifier. The first operational amplifier can be used as a pre-amplifier with a bandwidth of 60 Hz-400 Hz, the second operational amplifier can be used as a limiting amplifier. This limiting amplifier serves to provide an output voltage at approximately 3 Vss independent on the value of the input signal. The frequencies of the input signal will all be included in the output signal. The output signal of the limiter can be provided to a digital input of a system processor.
The signal of the music instrument typically comprises several harmonics, like second to fourth harmonics. Sometimes these harmonics can be higher than the fundamental wave. As an example, tone “A” has a ground frequency of 110 Hz, the tone “E” has a ground frequency of 82.5 Hz. The second, fourth, eighth etc. harmonics of a tone is the same tone. However, it should be noted that the third harmonics is another tone. Accordingly, for a guitar, the fourth harmonics of the E-cord with 330 Hz has the same frequency as the third harmonics of an A-cord.
Accordingly, in any subsequent audio processing, the ambiguity of the harmonics must be dealt with.
The circuit of the tuning assisting unit is very simple and is also very cheap such that an integrated tuning unit can be provided for a wireless receiver.
At the input IN the tuning assisting unit TU receives the signal of the music instrument. The first operational amplifier O1 serves as an amplifier with a bandpass characteristic. The second operational amplifier O2 is in an open-loop gain operation without a negative feedback. The second operational amplifier O2 supplies the limited output signal TF which corresponds to the tone frequency to a subsequent audio processing.
In an alternative embodiment, the tuning assisting unit can also be implemented or realised by means of a digital signal processor.
In a further embodiment, the tuning unit as described above can also be implemented in a wireless transmitter to which a music instrument can be coupled to.
The receiver R may optionally comprise a display for displaying the output results of the tuning assisting unit, i. e. whether a tone for a music instrument corresponds to a present frequency (a present tone).
