Patent Description:
<CIT> and <CIT> disclose a marine multibeam sonar device comprising a receiver having a plurality of receive channels.

The present invention is directed to a marine multibeam sonar device as defined in claim <NUM>. Preferred embodiments of the marine multibeam sonar device are the subject-matter of the dependent claims.

Embodiments of the present technology provide a marine multibeam sonar device comprising a transmitter, a memory element, and a processing element. The transmitter includes a plurality of transmit channel circuits, each connected to one of a plurality of transmit transducers. Each transmit channel circuit is configured to receive a transmit transducer electronic signal. The transmit transducers are oriented in a linear array that is configured to form a transmit acoustic beam. The processing element is in communication with the transmitter and the memory element and is configured to generate the transmit transducer electronic signals, each including a serial binary bitstream.

Other aspects and advantages of the present technology will be apparent from the following detailed description of the embodiments and the accompanying drawing figures.

Embodiments of the present technology are described in detail below with reference to the attached drawing figures, wherein:.

The drawing figures do not limit the present technology to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the technology.

The following detailed description of the technology references the accompanying drawings that illustrate specific embodiments in which the technology can be practiced. The embodiments are intended to describe aspects of the technology in sufficient detail to enable those skilled in the art to practice the technology. Other embodiments can be utilized and changes can be made without departing from the scope of the present technology. The following detailed description is, therefore, not to be taken in a limiting sense.

Embodiments of the present technology relate to a marine multibeam sonar device. The device includes a plurality of transmit channels to transmit sound waves into a body of water and a plurality of receive channels to receive reflections of the sound waves. As a result of wave interference and through the use of beamforming techniques, the device may form a sonar beam whose direction in the body of water can be controlled. Multibeam sonar devices traditionally have not been developed for the consumer market. The devices are often large in size and may require multiple people to install them on a marine vessel. In addition, the performance of traditional multibeam sonar devices may suffer as a result of electrical noise from sources within the marine vessel.

Embodiments of the technology will now be described in more detail with reference to the drawing figures. Referring initially to <FIG>, a marine multibeam sonar device <NUM> is illustrated which may utilize beamforming techniques on a plurality of transmit channels and a plurality of receive channels in order to produce a sonar beam whose direction can be controlled. The marine multibeam sonar device <NUM> may reduce size and cost by multiplexing signals from various channels and may improve performance with noise rejection techniques that involve inverting the polarity of various electronic signals. The marine multibeam sonar device <NUM> broadly comprises a transmitter <NUM>, a receiver <NUM>, a housing <NUM>, a memory element <NUM>, and a processing element <NUM>.

The transmitter <NUM> may include a plurality of transmit signal processing circuits <NUM> and a plurality of associated transmit transducers <NUM>. The combination of a transmit signal processing circuit <NUM> and its associated transmit transducer <NUM> forms a transmit channel. In an exemplary embodiment, the transmitter <NUM> may include twenty-four transmit channels. Each transmit signal processing circuit <NUM>, as shown in <FIG>, may process one of a plurality of transmit transducer electronic signals, indicated as "TX" and "TX" in <FIG>, and may include a low pass filter <NUM>, a variable gain amplifier <NUM>, a power amplifier <NUM>, and a transformer <NUM>.

The low pass filter <NUM> generally passes frequencies of one transmit transducer electronic signal that are below a cutoff frequency and attenuates frequencies that are greater than the cutoff frequency. The low pass filter <NUM> may also adjust a shape of the voltage waveform of the transmit transducer electronic signal. The low pass filter <NUM> may include passive and active electronic components such as resistors, capacitors, operational amplifiers, and the like, to form filtering circuits as are generally known. The cutoff frequency may be chosen to be compatible with sonar operating frequencies.

The variable gain amplifier <NUM> generally amplifies one transmit transducer electronic signal with a gain that can be varied. The variable gain amplifier <NUM> may include passive and active electronic components such as potentiometers, resistors, capacitors, operational amplifiers, and the like, to form amplifying circuits as are generally known. The gain may be set by the processing element <NUM> according to a shading factor, as described in more detail below.

The power amplifier <NUM> generally amplifies one transmit transducer electronic signal and may include passive and active electronic components such as resistors, capacitors, operational amplifiers, line drivers, and the like, to form amplifying circuits as are generally known. The power amplifier <NUM> may further convert the single-ended transmit transducer electronic signal to a differential signal.

The transformer <NUM> generally changes the voltage of one transmit transducer electronic signal and may include a center tap transformer with a primary and a secondary as is generally known. The primary may receive the differential signal from the power amplifier <NUM>. The center tap of the secondary may be connected to ground, while a first terminal of the secondary may present a positive polarity of the transmit transducer electronic signal and a second terminal may present a negative polarity of the transmit transducer electronic signal. In addition, the transformer <NUM> may be configured as a step-up transformer, wherein the voltages of the secondary are greater than the voltage of the primary.

Each transmit signal processing circuit <NUM> receives one transmit transducer electronic signal from the processing element <NUM>, filters it, amplifies it, and converts it to a double-ended signal with a positive polarity and a negative polarity with respect to ground. In exemplary embodiments, the device <NUM> may include twenty-four transmit transducer signals, twenty-four transmit signal processing circuits <NUM>, and twenty-four transmit transducers <NUM>.

Each transmit transducer <NUM> may include a transducer formed from piezoelectric materials like ceramics such as lead zirconate titanate (PZT) or polymers such as polyvinylidene difluoride (PVDF) that are configured to receive the transmit transducer electronic signal and produce a series of mechanical vibrations or oscillations that generates a corresponding sound beam. The sound beam may be produced with an acoustic polarity that corresponds to an electrical polarity of the transmit transducer electronic signal. For example, a transmit transducer electronic signal with a positive electrical polarity may cause the transmit transducer <NUM> to generate a sound beam with positive acoustic pressure, while a negative electrical polarity may result in a sound beam with negative acoustic pressure. Thus, the transmit transducer <NUM> may have a polarity as indicated in <FIG>.

The transmit transducers <NUM> may be coupled to the transformers <NUM> such that the transmit transducers <NUM> of the odd-numbered transmit channels receive the transmit transducer electronic signals with a first polarity while the even-numbered transmit channels receive the transmit transducer electronic signals with a second polarity that is opposite to the first polarity. This coupling scheme may provide noise cancelation as discussed below. The transmit transducers <NUM> are typically positioned to form a linear array <NUM>, as seen in <FIG>, <FIG>, with spacing between adjacent transducers, wherein the spacing may be related to a wavelength of the sound beam.

The components that form the transmit signal processing circuits <NUM> and the transmit transducers <NUM> are typically placed on a printed circuit board (PCB), on a flexible (flex) circuit, or combinations thereof. In an exemplary embodiment, the components of the transmit signal processing circuits <NUM> are placed on a PCB, while the transmit transducers <NUM> are placed on a flex circuit.

The transmitter <NUM> may generate a transmit beam <NUM> based on the transmit transducer electronic signals, which are received from the processing element <NUM>. Each transmit transducer electronic signal is a series of periodic pulses, such as sine wave pulses or square wave pulses, whose phase can be adjusted. A single series of pulses may be referred to as a "ping". Each transmit transducer <NUM> produces a sound beam upon receipt of the transmit transducer electronic signal. Given the close proximity of the transmit transducers <NUM> to one another in the transmit transducer array <NUM>, when each transmit transducer produces a sound beam, constructive and destructive wave interference may occur, creating a pattern of nodes and antinodes that can be shaped to form the transmit beam <NUM>, which functions as a single sound beam.

The transmit beam <NUM> may include a main lobe and a plurality of side lobes. The main lobe may receive most of the energy and may have a teardrop, or similar, shape that has a base which projects from the transmit transducer array <NUM>. The side lobes receive much less energy and project at angles that place them at the sides of the base of the main lobe. The side lobes may be attenuated by adjusting the gain of the variable gain amplifier <NUM> of the transmit signal processing circuit <NUM> connected to the appropriate transmit transducers <NUM>. This gain adjustment may be known as "shading", and the value of the gain may be the shading factor. In some cases the gain for the variable gain amplifier <NUM> of the transmit signal processing circuit <NUM> connected to the transmit transducers <NUM> near the center of the transmit transducer array <NUM> may be adjusted to be greater than the gain for the transmit transducer <NUM> near the edges of the transmit transducer array <NUM>.

In operation, the transmit beam <NUM> may be considered to have a roughly triangular profile with a long, narrow base representing a swath where the beam impacts the water bed. The transmit beam <NUM> may be oriented such that its longitudinal axis is orthogonal to the axis formed by the transmit transducer array <NUM>. The direction of the transmit beam <NUM>, or its angle α with respect to the array axis as seen in <FIG>, may be controlled or formed by controlling the phase of each sound beam, which in turn may be controlled by the transmit transducer electronic signals. Thus, by properly adjusting the phase of each transmit transducer electronic signal, the direction of the transmit beam <NUM> may be varied. If the phases are adjusted on successive pings of the transmit transducer electronic signals, then the transmit beam <NUM> may be swept through a range of angles. When the transmitter <NUM> is utilized with a marine vessel and the transmit beam <NUM> is swept, the beam may be swept from front to back of the vessel or from side to side, depending on the orientation of the transmit transducer array <NUM>. In addition, the width of the transmit beam <NUM>, as shown in <FIG>, may be controlled by adjusting the phase of each transmit transducer electronic signal.

When the marine multibeam sonar device <NUM> is operating in the marine vessel, electrical noise from sources such as the marine vessel engine, other electronic devices, or the marine multibeam sonar device <NUM> itself may affect the transmit transducer electronic signals. The noise may be introduced anywhere along the transmit transducer electronic signal path from the low pass filter <NUM> to the transmit transducer <NUM>. This may result in each transmit transducer electronic signal including a data component, which is supplied by the processing element <NUM>, and a noise component, which comes from the noise sources. One way to reduce the effect that the noise has on the transmit beam <NUM> is to try to cancel it when forming the transmit beam <NUM> by taking advantage of destructive wave interference. Both the data component and the noise component have a polarity. Furthermore, both the data component and the noise component are generated in the sound beam that is produced by each transmit transducer <NUM>. If the polarity of the noise component of the sound beam produced by each transmit transducer <NUM> is inverted as compared with the polarity of the noise component of the sound beams from the two adjacent transmit transducers <NUM>, then the noise components may effectively cancel one another due to destructive wave interference because half the noise components have a positive polarity and the other half of the noise components have a negative polarity. In an exemplary implementation, the noise components from the odd-numbered transmit transducers <NUM> may have a positive polarity, while the noise components from the even-numbered transmit transducers <NUM> may have a negative polarity.

The polarity of the noise component of the sound beam from each transmit transducer <NUM> is determined by the polarity of the noise component of the transmit transducer electronic signal. Thus, inverting the polarity of the sound beam noise component involves inverting the polarity of the electronic signal noise component, which means inverting the polarity of the transmit transducer electronic signal. This is accomplished as shown in <FIG> and discussed above wherein the double ended output of the transformer <NUM> for the even-numbered transmit channels is reversed before it is connected to the transmit transducer <NUM>. Therefore, inverting the polarity of the transmit transducer electronic signal as it goes to the transmit transducer <NUM> on every other channel may cancel, or at least greatly reduce, the electrical noise. In some configurations, other inversion configurations may be employed. For instance, pairs of channels may be inverted (two non-inverted channels followed by two inverted channels), triplets may be inverted, and the like.

However, inverting the polarity of the transmit transducer electronic signal also inverts the polarity of the data component, which is what gives the transmit beam <NUM> its proper shape. It would be undesirable to invert the polarity of the data component of the transmit transducer electronic signal for every other transmit channel. In order to avoid this situation, the polarity of the data component of the transmit transducer electronic signal for the even-numbered transmit channels may be generated in an inverted state by the processing element <NUM> before the transmit transducer electronic signal enters the data path shown in <FIG>. The inverted polarity signals are indicated in <FIG> as "TX". Thus, when the polarity of the transmit transducer electronic signal for the even-numbered transmit channels is inverted by the transformers <NUM> before being communicated to the transmit transducers <NUM>, the polarity of the data component for the even-numbered transmit channels is actually re-inverted and restored to its proper state. As a result, the data component of all of the transmit channels has the same polarity when the transmit beam <NUM> is generated by the transmit transducers <NUM>.

In exemplary embodiments, the polarity of the transmit transducer electronic signals may be inverted on the PCB before the signal is communicated to the transmit transducers <NUM> on the flex circuit. However, the inversion of the polarity of the transmit transducer electronic signals may be implemented in many other ways.

The receiver <NUM> includes a plurality of receive transducers <NUM> and a receive signal processing circuit <NUM>, as seen in <FIG>. Each receive transducer <NUM> may also be considered as providing a receive channel. In exemplary embodiments, the receiver <NUM> may include sixty receive transducers <NUM> or sixty receive channels. The receive transducers <NUM> may each include a transducer formed from piezoelectric materials like ceramics such as lead zirconate titanate (PZT) or polymers such as polyvinylidene difluoride (PVDF) that are configured to receive a mechanical force or pressure. Each receive transducer <NUM> generates a receive transducer electronic signal, which may include a variable voltage corresponding to the mechanical force. As with the transmit transducer <NUM>, the receive transducer <NUM> may have a polarity, such as a positive surface or terminal and a negative surface or terminal, wherein the polarity of the voltage generated, and in turn, the receive transducer electronic signal, may correspond to the polarity of the acoustic pressure applied to the receive transducer <NUM>. Typically, the receive transducer electronic signal is a series of periodic pulses, such as sine wave pulses. In some embodiments, the receive transducers <NUM> may be formed from the same material as the transmit transducers <NUM>. In various embodiments, the receive transducers <NUM> may be implemented such that the polarity of the even-numbered receive transducer electronic signals is inverted compared with the polarity of the odd-numbered receive transducer electronic signals. One way to invert the polarity of the even-numbered receive transducer signals is to connect the positive terminal of the even-numbered receive transducers <NUM> to ground and the negative terminal to the receive signal processing circuit <NUM>, while the odd-numbered receive transducers <NUM> have their negative terminal connected to ground and their positive terminal connected to the receive signal processing circuit <NUM>.

The receive signal processing circuit <NUM> includes a multiplexer <NUM>, an analog to digital converter (ADC) <NUM>, and a serializer <NUM>, and may include a plurality of amplifiers <NUM>, a low noise amplifier <NUM>, a variable gain amplifier <NUM>, a low pass filter <NUM>, and a low voltage differential signal (LVDS) driver <NUM>.

Each amplifier <NUM> generally receives one receive transducer electronic signal from one receive transducer <NUM> and amplifies the signal. Each amplifier <NUM> may include passive and active electronic components such as resistors, capacitors, operational amplifiers, and the like, to form amplifying circuits as are generally known.

The multiplexer <NUM> generally performs a time division multiplexing of the receive transducer electronic signals from the amplifiers <NUM>. The multiplexer <NUM> may include a plurality of analog switches that receive a plurality of analog signals and selectively pass one of the signals. The multiplexer <NUM> may include successive stages of analog switches. The multiplexer <NUM> may further include a plurality of control signals that select the receive transducer electronic signal to pass to its output. The processing element <NUM> may control the level of the control signals. Typically, the control signals are set such that each receive transducer electronic signal is passed to the output of the multiplexer <NUM> in successive order for consecutive time slots, each time slot lasting for a first period of time. Thus, the output of the multiplexer <NUM> is a receive electronic signal which includes a stream of the receive transducer electronic signals, each signal per time slot.

The low noise amplifier <NUM> generally amplifies the receive electronic signal and may include passive and active electronic components such as resistors, capacitors, operational amplifiers, and the like, to form amplifying circuits as are generally known.

The variable gain amplifier <NUM> generally amplifies the receive electronic signal with a gain that can be varied. The variable gain amplifier <NUM> may include passive and active electronic components such as potentiometers, resistors, capacitors, operational amplifiers, and the like, to form amplifying circuits as are generally known.

The low pass filter <NUM> generally passes frequencies of the receive electronic signal that are below a cutoff frequency and attenuates frequencies that are greater than the cutoff frequency. The low pass filter <NUM> may include passive and active electronic components such as resistors, capacitors, operational amplifiers, and the like, to form filtering circuits as are generally known. The low pass filter <NUM> may also perform an antialiasing function and thus, the cutoff frequency may be related or proportional to the rate at which the ADC <NUM> samples the receive electronic signal.

The ADC <NUM> generally samples the receive electronic signal and generates a corresponding digital value. The analog to digital converter may include comparators, encoders, and other passive and active components as are generally known. The ADC <NUM> outputs a multibit, parallel digital value corresponding to the voltage level of the receive electronic signal.

The serializer <NUM> generally receives the multibit, parallel digital value of the receive electronic signal from the ADC <NUM> and converts it to a serial stream of bits. The serializer <NUM> may include shift registers or similar components that convert parallel data into serial data.

The LVDS driver <NUM> generally converts the single ended serial bitstream from the serializer <NUM> to a low voltage differential signal. The LVDS driver <NUM> may include passive and active electronic components such as resistors, capacitors, operational amplifiers, and the like, to create differential signals. Furthermore, the LVDS driver <NUM> may output a differential signal that conforms to the LVDS standard.

The receive signal processing circuit <NUM> receives the receive transducer electronic signals from the receive transducers <NUM> and generates the receive electronic signal, which includes digital samples of the receive transducer electronic signals in a differential voltage bitstream, indicated as RX <NUM> - RX M in <FIG>. The bitstream of digital samples forms a stream of packets, one packet for each receive channel in successive order, wherein the packet includes data from a time sliced portion of the associated receive transducer electronic signal. The receive signal processing circuit <NUM> communicates the receive signal to the processing element <NUM>.

In various embodiments, the low noise amplifier <NUM>, the variable gain amplifier <NUM>, the low pass filter <NUM>, the ADC <NUM>, the serializer <NUM>, and the LVDS driver <NUM> may implemented as one or more channels of an analog front end circuit. Furthermore, the device <NUM> may include a plurality of multiplexers <NUM>, wherein each multiplexer <NUM> multiplexes only a portion of the receive transducer electronic signals and communicates its output to one of the channels of the analog front end circuit. In addition, the analog front end circuit may generate a plurality of receive electronic signals, each one including a bitstream of only a portion of the receive transducer electronic signals.

The components that form the receive transducers <NUM> and the receive signal processing circuits <NUM> are typically placed on a PCB, on a flex circuit, or combinations thereof. In an exemplary embodiment, the receive transducers <NUM> and the amplifiers <NUM> are placed on a flex circuit, while the other components of the receive signal processing circuit <NUM> are placed on a PCB. In various embodiments, the other components of the receive signal processing circuit <NUM> are placed on the same PCB as the transmit signal processing circuits <NUM>.

The receive transducers <NUM> are typically positioned to form a linear array <NUM>, similar to the transmit transducer array <NUM> and seen in <FIG> and <FIG>, with spacing between adjacent transducers, wherein the spacing may be related to the wavelength of the transmit beam <NUM>. Given the close proximity of the receive transducers <NUM> to one another, the reflections of the transmit beam <NUM> received by the receive transducers <NUM> may be subject to wave interference properties. In addition, the data of each receive channel is associated with, or includes, a phase or time delay which may be adjusted. "Phase," as utilized herein, refers to a phase shift of a signal or equivalently a time delay of whole cycles which includes a partial cycle phase shift. These phase values may be utilized by the processing element <NUM> when sonar data is calculated, as described in more detail below. A particular set of phase values may determine the reflections that are received at a particular angle with respect to the receive transducer array <NUM>. The combination of the particular phase values and receive channel data may be considered a receive beam <NUM>, as seen in <FIG>. Varying the phase values also varies the angle of the receive beam <NUM>, with one set of phase values for each angle desired. The receive beam <NUM> may have a roughly triangular profile with a long, narrow base representing a swath where the beam reflects from the water bed. Furthermore, the receive beam <NUM> may be oriented such that its longitudinal axis is orthogonal to the axis formed by the receive transducer array <NUM>.

The receive transducer array <NUM> may be oriented with its linear axis orthogonal to the linear axis of the transmit transducer array <NUM>. In various embodiments, the receive transducer array <NUM> may be positioned such that one end of the receive transducer array <NUM> is adjacent to the center of the transmit transducer array <NUM>, as seen in <FIG> and <FIG>. This orientation allows the receive beam <NUM> to be swept across the path of the transmit beam <NUM> in order to determine the angular direction of the water bed features or other objects that reflect the transmit beam <NUM>.

The housing <NUM>, as seen in <FIG>, <FIG>, generally encloses the other components of the marine multibeam sonar device <NUM>. The housing <NUM> may include a top wall, a bottom wall, and four sidewalls. In some embodiments, the sidewalls may be rounded or may have a curvature. The transmit transducer array <NUM> and the receive transducer array <NUM> may be positioned in an opening on the bottom wall, as seen in <FIG>, so that they may be encapsulated and/or potted therein. In one configuration, the housing <NUM> is formed of molded plastic although other suitable materials may be employed.

The housing <NUM> is typically mounted to a hull of the marine vessel, but may be mounted anywhere which provides access to a body of water. The specific position and orientation of the housing <NUM> may depend on the type of scanning for which the marine multibeam sonar device <NUM> is utilized. With down and side scanning, the housing <NUM> may be mounted to the hull of the marine vessel such that the transmit transducer array <NUM> and the receive transducer array <NUM> lie in a horizontal plane with the transmit transducer array <NUM> extending between the forward and rear ends of the marine vessel and the receive transducer array <NUM> extending between the port and starboard sides of the marine vessel. With forward scanning, the housing <NUM> may be mounted to the hull of the marine vessel such that the transmit transducer array <NUM> and the receive transducer array <NUM> lie in a plane that is tilted approximately <NUM> degrees with respect to the horizontal. In addition, the transmit transducer array <NUM> may extend between the port and starboard sides of the marine vessel and the receive transducer array <NUM> may extend between the forward and rear ends of the marine vessel. In some embodiments, the housing <NUM> may include one or more mechanisms, such as servo motors, that will tilt and rotate the transmit transducer array <NUM> and the receive transducer array <NUM> in order to switch between modes of scanning.

The memory element <NUM> may include data storage components such as read-only memory (ROM), programmable ROM, erasable programmable ROM, random-access memory (RAM) such as static RAM (SRAM) or dynamic RAM (DRAM), hard disks, floppy disks, optical disks, flash memory, thumb drives, universal serial bus (USB) drives, or the like, or combinations thereof. The memory element <NUM> may include, or may constitute, a "computer-readable medium". The memory element <NUM> may store the instructions, code, code segments, software, firmware, programs, applications, apps, services, daemons, or the like that are executed by the processing element <NUM>. The memory element <NUM> may also store settings, data, documents, sound files, photographs, movies, images, databases, and the like.

The processing element <NUM> may include processors, microprocessors, microcontrollers, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), analog and/or digital application-specific integrated circuits (ASICs), or the like, or combinations thereof. The processing element <NUM> may generally execute, process, or run instructions, code, code segments, software, firmware, programs, applications, apps, processes, services, daemons, or the like, or may step through states of a finite-state machine, or combinations of these actions. The processing element <NUM> may be in communication with the other electronic components through serial or parallel links that include address busses, data busses, control lines, and the like.

The processing element <NUM> may be configured to control the operation of the transmitter <NUM>. The processing element <NUM> may generate the transmit transducer signal for each transmit transducer <NUM>. Each transmit transducer signal may include a digital bitstream of ones and zeroes that create a periodic waveform. The processing element <NUM> may generate each transmit transducer signal so that it includes a bitstream with the proper phase adjustment of each transmit transducer <NUM> for the transmitter <NUM> to project the transmit beam <NUM> at the desired angle α, as shown in <FIG>, and width, as shown in <FIG>. In general, the processing element <NUM> may include pattern generating hardware or software algorithms that can generate the bitstream. In addition, the processing element <NUM> may invert the polarity of the bitstream for every other transmit channel. In exemplary embodiments, the processing element <NUM> may invert the polarity of the bitstream for the even-numbered transmit channels. In some configurations, the processing element <NUM> may employ other inversion schemes, such as inverting pairs of transmit channels, inverting triplets of transmit channels, and the like.

In exemplary embodiments, a bitstream waveform pattern may be created and stored in the memory element <NUM>. The pattern may form a periodic wave, such as a sine wave, a triangle wave, a square wave, and the like. The pattern may be used to create a ping or a series of pings. In certain embodiments, a plurality of bitstream waveform patterns may be created and stored in the memory element <NUM>, wherein each pattern may form a different wave shape or have another unique characteristic.

When the transmit transducer array <NUM> is generating the transmit beam <NUM>, each transmit transducer <NUM> generates the same periodic acoustic waveform with the phase of the waveform appropriately adjusted to form the transmit beam <NUM> and to steer it. Since the bitstream pattern of each transmit transducer electronic signal is used to create the acoustic waveform, the phase of each bitstream pattern is adjusted in order to adjust the phase of the acoustic waveform emanating from the transmit transducer <NUM>. The processing element <NUM> communicates the same bitstream pattern to each transmit channel, but appropriately adjusts the phase of the pattern for each channel. The processing element <NUM> adjusts the phase of the bitstream pattern by selecting the appropriate bit within the pattern to start generating the bitstream. For example, if the bitstream pattern is <NUM> bits long, then the processing element <NUM> may start generating the bitstream for a first transmit channel at bit <NUM> of the pattern, a second transmit channel at bit <NUM>, a third transmit channel at bit <NUM>, and so forth, with all of the bitstreams being generated and communicated to the transmitter <NUM> at roughly the same time. Thus, the processing element <NUM> may generate the bitstream pattern for each transmit channel with an offset within the pattern.

Generally, the offset of the bitstream pattern for each transmit channel is determined by the position of the associated transmit transducer <NUM> in the transmit transducer array <NUM>. Some transmit channels may have the same offset, while others may have a different offset. By offsetting the bitstream pattern for at least a portion of the transmit channels, the processing element <NUM> effectively sets the relative phase of each transmit transducer electronic signal and, in turn, the phase of the acoustic waveform generated by each transmit transducer <NUM>. In this fashion, the transmit beam <NUM> is properly formed. Furthermore, by adjusting the offset in the bitstream pattern for each transmit channel, the transmit beam <NUM> may be steered to the desired angle α. In addition, the processing element <NUM> may send a value to the variable gain amplifier <NUM> of each transmit signal processing circuit <NUM> to adjust its gain in order to properly shade the side lobes of the transmit beam <NUM> and/or adjust the width of the beam <NUM>. The processing element <NUM> may perform the above-described actions for each ping of the transmit beam <NUM>.

The processing element <NUM> is configured to calculate sonar data based on the reception of the reflections of the transmit beam <NUM>. The processing element <NUM> receives the receive transducer electronic signals as a bitstream from the receive signal processing circuit <NUM>. The bitstream includes a packet of data for the first receive channel followed by a packet of data for the second receive channel and so forth for all of the receive channels.

As mentioned above for the transmit transducer electronic signals, electrical noise from a variety of sources may affect the receive transducer electronic signals as well. Likewise, the receive transducer electronic signals may each include a data component, supplied by the receive transducer <NUM>, and a noise component from the noise sources. Furthermore, the noise may be canceled, or at least greatly reduced, by taking advantage of similar properties that the receive channels have with the transmit channels. The noise components may be canceled by inverting their polarities on every other receive channel. The polarity of the noise component of the appropriate receive channels may be inverted by inverting the polarity of the appropriate receive transducer electronic signals. Since the receive transducer electronic signals are received by the processing element <NUM> as a packet of data for each receive channel, the processing element <NUM> may invert the data included in every other packet - thereby inverting the polarity of the noise component for every other receive channel. In exemplary embodiments, the processing element <NUM> may invert the data from all of the even-numbered receive channels. When the processing element <NUM> is calculating the sonar data as discussed in more detail below, the noise components may cancel each other out.

However, as with the transmit transducer electronic signals, inverting the polarity of the receive transducer electronic signals also inverts the polarity of the data component of those receive channels, which would cause a misinterpretation of the data from those channels. In order to avoid this problem, the polarity of the even-numbered receive transducer electronic signals is inverted from the receive transducer <NUM>, as shown in <FIG> and discussed above. Thus, when the processing element <NUM> inverts the data in the packets from the even-numbered receive channels, the processing element <NUM> is actually re-inverting the data so that the polarity of the receive transducer electronic signal is restored to its proper state, thereby allowing the calculations of the sonar data to be performed correctly.

The processing element <NUM> may perform a series of calculations on the receive channel data to determine the features of the water bed or underwater objects in the path of the transmit beam <NUM>. The processing element <NUM> may set the phase value for each receive transducer electronic signal to calculate sonar data for the receive beam <NUM> being positioned at a first angle. Typically, the first angle is set for the receive beam <NUM> to point at one edge of the transmit beam <NUM> swath. The processing element <NUM> may also adjust the phase value for each receive transducer electronic signal to calculate sonar data for the receive beam <NUM> being positioned at a plurality of incrementally increasing angles, wherein the last angle corresponds to the opposite edge of the transmit beam <NUM> swath.

In some embodiments, the calculations of the sonar data may be performed as a set of simultaneous equations or a matrix equation. Furthermore, calculations such as a fast Fourier transform (FFT) may be performed to compute the sonar data. The time delay from when the ping was generated until the reflections were received may determine the depth of objects in the transmit beam <NUM> path or the water bed. The amplitude, intensity, or other characteristics of the sonar data may determine the density of the objects in the transmit beam <NUM> path or the water bed.

Referring to <FIG>, the marine multibeam sonar device <NUM> may function as follows. The transmitter <NUM> may receive the transmit transducer electronic signals from the processing element <NUM> and, in turn, may generate a ping or a short burst of pings along the transmit beam <NUM> path (whose angle is determined by controlling the phase of the transmit transducer electronic signal to each transmit transducer <NUM>). The receive transducer array <NUM> may receive the reflections of the transmit beam <NUM> and each receive transducer <NUM> generates a receive transducer electronic signal. The receive transducer electronic signals are communicated to the processing element <NUM>, which performs a series of calculations on the data from each receive channel. The calculations may determine how the receive beams <NUM> are formed to receive the transmit beam <NUM> reflections at successive angles. The combination of the single transmit beam <NUM> and the multiple receive beams <NUM> may form a sonar beam <NUM> where the transmit beam <NUM> and the receive beams <NUM> overlap. Thus, each sonar beam <NUM> may be thought of as emanating from a single point and formed from a single transmit beam <NUM> and a plurality of receive beams <NUM>, as seen in <FIG>, wherein the number of receive beams <NUM> may depend on the resolution of the sonar beam <NUM> that is desired. Generally, the higher the number of receive beams <NUM>, the greater the resolution. Furthermore, the sonar beam <NUM> may be projected at the same angle α, as seen in <FIG>, with respect to the plane of the transmit transducer array <NUM> and the receive transducer array <NUM> as the transmit beam <NUM>. In addition, since the sonar beam <NUM> is formed from the transmit beam <NUM>, the width of the sonar beam <NUM>, as shown in <FIG>, may be controlled by adjusting the phase of each transmit transducer electronic signal.

The marine multibeam sonar device <NUM> may have one or more modes of operation. In a first mode, the marine multibeam sonar device <NUM> may generate the sonar beam <NUM> at a fixed angle α for repeated pings. Typically, the angle α is set for approximately <NUM> degrees, such that the sonar beam <NUM> points roughly straight down beneath the marine vessel for down and side scanning or roughly straight forward for forward scanning. This mode may be useful for surveying or mapping the water bed. In addition, the sonar beam <NUM> may be set and held at angles α other than <NUM> degrees, depending on the application of the marine multibeam sonar device <NUM>. Furthermore, the width of the sonar beam <NUM> may be adjusted so that more area of the water bed is covered when "live" sonar images are being viewed.

In a second mode, the sonar beam <NUM> may be swept across a range of angles, wherein the sonar beam <NUM> is projected on a first ping at the minimum angle α. On successive pings, the sonar beam <NUM> may be projected at incrementally increasing angles α until the maximum angle α is reached. When used for down and side scanning, the sonar beam <NUM> may be swept from forward to rear, or vice versa. When used for forward scanning, the sonar beam <NUM> may be swept from starboard to port, or vice versa. This mode may be useful when the marine vessel is still or is moving slowly, or when trying to locate underwater objects, such as schools of fish.

The marine multibeam sonar device <NUM> may be in communication with external equipment, devices, and systems that can display sonar imagery based on the sonar data. Thus, the marine multibeam sonar device <NUM> may communicate the sonar data to the external equipment. Furthermore, the external equipment might direct the marine multibeam sonar device <NUM> as to the mode in which to operate. For example, depending on user preferences, the external equipment might direct the marine multibeam sonar device <NUM> to hold the sonar beam <NUM> at a fixed angle or to sweep the sonar beam <NUM>.

At least a portion of the steps of a method <NUM>, in accordance with various aspects of the current technology, of generating an acoustic waveform with a transducer array <NUM> including a plurality of transducers <NUM> is listed in <FIG>. The steps of the method <NUM> may be performed in the order as shown in <FIG>, or they may be performed in a different order. Furthermore, some steps may be performed concurrently as opposed to sequentially. In addition, some steps may not be performed.

Referring to step <NUM>, an angle is determined at which the acoustic waveform is to be generated. The acoustic waveform may be a sonar beam <NUM>, or a portion thereof, generated by the transmit transducer array <NUM>, which is implemented in a system or device for displaying sonar images, wherein each sonar image is derived from one or more pings of the sonar beam <NUM>. The angle of the sonar beam <NUM> may be determined by input from the user regarding viewing modes of the sonar images. For example, the user may choose a viewing mode in which the sonar beam is generated at a constant angle for repeated pings. Alternatively, the user may choose a viewing mode in which the sonar beam is swept across a range of angles during a series of pings.

Referring to step <NUM>, a binary bitstream is formed from a binary bitstream pattern. The binary bitstream may be an arbitrary sequence of ones and zeros. The binary bitstream pattern may be a series of ones and zeros that corresponds to a shape of the acoustic waveform. The binary bitstream pattern may be periodic. When the binary bitstream is transmitted, as discussed below, exemplary embodiments of the binary bitstream include the specific binary bitstream pattern. The binary bitstream pattern may be stored in a memory element <NUM>.

Referring to step <NUM>, a phase may be determined for each of a plurality of transmit transducer electronic signals. The transmit transducer electronic signals are to be communicated to the transmit transducer array <NUM>, one signal to each transmit transducer <NUM>. Each transmit transducer electronic signal is a periodic signal which includes the binary bitstream and each signal has its own value of the phase. The value may vary according to the angle at which the acoustic waveform is to be generated. The value may also vary according to the position within the transmit transducer array <NUM> of the associated transducer <NUM>.

Referring to step <NUM>, an offset is determined within the binary bitstream pattern that corresponds to each determined phase. Since the binary bitstream pattern is periodic, a phase of the pattern can be determined as well. The phase of the binary bitstream pattern may also be considered an offset, such as a bit position, within the bit pattern. Thus, the offset within the binary bitstream pattern corresponds to the phase of the transmit transducer electronic signal.

Referring to step <NUM>, one transmit transducer electronic signal is transmitted to each of the transmit transducers <NUM>. A processing element <NUM> may transmit the transmit transducer electronic signals to the transmit transducers <NUM>. The transmit transducer electronic signals each include a binary bitstream, and some embodiments of the processing element <NUM> may include hardware and/or software to generate the binary bitstreams. However, exemplary embodiments of the processing element <NUM> may retrieve the binary bitstream pattern from the memory element <NUM> and may start generating the pattern at the offset point that corresponds to the determined phase of the transmit transducer electronic signal for each transducer <NUM>.

Claim 1:
A marine multibeam sonar device (<NUM>) comprising:
a receiver (<NUM>) configured to receive reflections of a transmit acoustic beam, the receiver (<NUM>) including -
a plurality of receive channels, each receive channel including a receive transducer (<NUM>) configured to generate a receive transducer electronic signal, and
electronic circuitry configured to receive the receive transducer electronic signals and generate a receive signal including a stream of binary data packets each packet including data from a time sliced portion of one of the receive transducer electronic signals;
a memory element (<NUM>); and
a processing element (<NUM>) in communication with the receiver (<NUM>) and the memory element (<NUM>),
the processing element (<NUM>) being configured to -
receive and deserialize the receive signal,
retrieve the binary data packet for each receive channel contained in the receive signal, and generate sonar data from the binary data packets,
characterized in that the electronic circuitry of the receiver (<NUM>) further comprises -
a multiplexer (<NUM>) configured to receive the receive transducer electronic signal from each receive transducer (<NUM>) and generate a multiplexer signal that includes a time sliced portion of each of the receive transducer electronic signals in successive order,
an analog to digital converter (<NUM>) configured to receive the multiplexer signal and generate a parallel multibit binary output that is a digital value corresponding to an analog voltage of the multiplexer signal, and
a serializer (<NUM>) configured to receive the analog to digital converter output and generate a serializer signal that is a conversion of the parallel output of the analog to digital converter (<NUM>) to a serial bitstream.