Infrared technology solves the problem of wireless audio transmission

High fidelity (hi-fi), consumer electronics, audio systems, home theater But this approach breeds a lot of problems, such as limiting mobility, and messy and obtrusive cables throughout the room (such as home or office), which is not only inconvenient but also affects the aesthetics of the environment. To succeed in today's competitive market, modern short-range communication devices need to achieve simple and fast connection with various resources through wireless means.

One approach to achieving short-range wireless connectivity is to use specially allocated radio frequency (RF) bands by government agencies to transmit/receive various signals. For example, RF solutions for certain consumer electronics applications (such as PC networking) are very popular reliable wireless data connections. However, on the other hand, RF-based communication solutions for real-time, streaming, home entertainment applications (such as audio and video) are easily interfered by other wireless RF systems such as WLAN (802.11), Bluetooth, cordless phones, etc. All of these RF-based applications use the free but crowded 2.4GHz or 5/5.8GHz ISM RF bands and are easily affected by co-channel interference.

In addition, the home entertainment industry has also set up obstacles for RF-based devices. In this field, the connection must maintain ultra-low latency to ensure 'lip sync' between the video image produced by the AV source and the wirelessly connected audio reproduction device (i.e. speakers). In fact, RF is very suitable for wireless data links, and data can be retransmitted in the event of interference, but it is much more difficult to achieve reliable transmission of uncompressed hi-fi audio streams. In addition, RF used in mobile phones, Bluetooth headsets, etc. is suspected of causing harm to human health if used frequently, and professional medical literature is now discussing this issue more and more frequently.

The use of infrared (IR) light as a wireless communication medium is also very popular. We often see IR ports on mobile phones, PDAs and other consumer (CE) devices. It is reported that the number of devices with IR ports has reached nearly 1 billion, and infrared remote control is the communication standard for indoor wireless control. However, traditional IR solutions require line of sight and directionality between the transmitter and the receiving device, which greatly limits its application areas and market appeal. The data transmission rate of IR ports can be quite high, but the working range is very short, only 10cm-100cm for IrDA devices; or the distance can be longer, but the data transmission rate is very low (such as remote control applications).

To overcome these issues with existing IR solutions while avoiding RF communication issues, Infra-Com has developed products based on diffuse infrared (DIR) technology. DIR uses the ability of infrared light signals to bounce off surfaces to avoid the line-of-sight and directionality requirements of traditional IR solutions. With DIR, the information radiated by the infrared signal generated by the transmitter "bounces" throughout an enclosed space (such as a room, office, or laboratory) and is then collected by a specially designed, highly sensitive receiver. DIR technology extends the range of infrared products, thereby broadening their application range.

1. Unique ASIC chipset

Infra-Com has created the first truly marketable, low-cost technology platform for short-range omnidirectional optical wireless communications. Infra-Com has designed a unique ASIC group (i.e., chipset) based on the DIR scheme. IrGate relies on IR 'diffuse' reflection and scattering from ceilings, walls and other surfaces to establish high-bit wireless communications (see Figure 1).

Figure 1: IrGate's full-scale form works in an enclosed space

The IrGate transmitter uses an IR LED array to transmit in three dimensions over a wide area within an enclosed space, while the IrGate receiver uses a highly sensitive receiver array to detect the residual infrared energy that was transmitted and reproduce the original signal, even if it has been severely absorbed and attenuated along the optical path.

Infra-Com markets IrGate technology in the form of a small form factor ASIC chipset, the first of its kind. The benefits of this highly flexible solution have been tested and proven by major vendors in the consumer electronics industry, who have already shipped first samples embedded with IrGate.

IrGate's inherent advantages include:

1. Low cost - Baseband infrared solutions like IrGate can reduce the cost of the manufacturing process. Infra-Com is establishing a development path for further miniaturization, which will lead to a significant reduction in the cost per link.

2. Reliable high bandwidth - IrGate can now achieve a raw bit rate of 22.5Mbps (50Mbps with further development); it can work under different ambient lighting conditions (i.e. natural light and artificial light) and provides inherent partitioning, that is, IrGate-based communications/networks can achieve adjacent spaces without co-channel interference caused by "bandwidth reuse".

3. Avoid RF technical problems - IrGate does not interfere with RF devices; it avoids RF signal delay issues in audio/video streaming applications; IR signals cannot pass through walls and can only work in closed spaces, thus ensuring privacy and security.

4. No frequency allocation or regulatory issues - IrGate is a global, non-regulated technology. It does not require government frequency allocation or any specific classification; "green" IR signals cannot penetrate human tissue and are harmless.

5. Modifiable for consumer electronics applications - IrGate is implemented as a small form factor chipset so it can be embedded in many different types of consumer electronics devices; it provides ODM/OEM with a 'plug and play' system implementation through a very concise reference design; its digital ASIC (i.e. the interface to the 'outside world') uses industry standard interfaces (such as I2S) to connect directly to existing devices, so the most commonly used system architectures can be retained.

2. Targeting the wireless audio field

Infra-Com's current application focus is the wireless audio market, where it has accumulated a lot of valuable technology, product and market experience. Infra-Com will continue to move forward with a series of predefined next-generation development steps to make IrGate more flexible and more suitable for this specific market. These initiatives will reduce manufacturing costs while improving functionality and performance. The company's customers will realize a reduction in system prices unless they embed multiple different peripheral components to add more functionality to the IrGate IC.

2.1 IrGT800 chipset series for wireless audio communication

The IrGT800 chipset family for wireless audio communications provides a high-quality, easy-to-implement solution for markets that currently use inconvenient wired products or, as mentioned previously, low-quality RF solutions that are susceptible to interference. Infra-Com recognizes the complex challenges of creating a commercially viable, low-cost semiconductor solution that can wirelessly connect rear surround sound speakers in enclosed spaces/rooms to a variety of audio source devices such as home theater systems, digital televisions, and portable music devices (such as iPod accessories). Infra-Com has successfully begun shipping the IrGT801A chipset, the industry's first chipset with high-bit-rate DIR wireless communication capabilities. The IrGT801A has an infrared communication range of up to 25-50 feet (depending on environmental conditions and system architecture), no line-of-sight or directionality requirements, and a raw data rate (i.e., data rate before modulation, FEC, framing, etc.) of 20Mbps. The IrGT801A has an ultra-low latency (100 microseconds) advantage, making it particularly suitable for high-fidelity (hi-fi) audio applications. In addition, the IrGT801A comes with a simple hardware reference design that does not use software and firmware installations, making it easy to implement a full wireless communication link for audio applications. The overall system and link may include high-quality wireless rear surround sound, subwoofers or other speakers. Moreover, the integration of the IrGT801A, like all other IrGate-based ASICs, benefits from the small form factor of the chipset.

The main specifications of IrGT801A are as follows:

1. Embedded I2S interface. I2S is a recognized audio industry standard—all audio ICs on PCBs used in DVDs, HTiB systems, CDs, speaker amplifiers, etc. use this common, simple standard.

2. The transmit (Tx) and receive (Rx) ends of the IrGT801A both contain a digital IC and an analog IC. The digital IC is used as the modem/interface function of the entire chipset, while the analog IC is part of the analog optical front-end subsystem.

3. Supports up to 4 channels of uncompressed (24-bit) digital audio (speakers).

4. Online forward error correction (FEC), automatic mute function, automatic speaker shutoff function, user indication LED.

2.2 Enhanced IrGT821 IC Series

Infra-Com's IrGT821 next-generation digital audio IC is also now in mass production, and the device offers more advanced features than the IrGT801A series. It also adds a wireless I2C control channel and 4 wireless audio channels, which can control remote peripheral resources (such as DAC, Class D amplifier, digital signal processor) in wireless speakers. The IrGT821 IC includes the IrGT821ADT (Tx) and IrGT821ADR (Rx) sections, which are connected to the LED driver transmitter and analog receiver IC of the IrGT801A, respectively, as shown in Figure 2:

Figure 2: IrGT821 system block diagram

The IrGT821ADx digital chipset has the following enhanced features:

1. Wireless volume/mute control on the receiver side.

2. Higher audio sampling rate - up to 96kHz, while the existing IrGT801A's audio sampling rate is only 48KHz.

3. Support hardware and software modes - IrGT821 supports both separate hardware operating mode (similar to IrGT801A) and software operating mode. In software mode, the IrGT821ADT transmitter IC can receive various control commands from external devices (such as MPEG IC or MCU) and wirelessly transmit them to the IrGT821ADR receiver IC to control the remote peripheral audio device connected to the speaker-side IrGT821ADR device.

2.3 Low-cost IrGT851 IC series

To fulfill its promise of cost reduction, Infra-Com also intends to develop the IrGT851 IC series, a solution based on standard cell ASIC. While the IrGT801A and IrGT821A use structured ASIC technology, the IrGT851 will utilize an ASIC-based COT (customer own tool) mass production business model. This process allows customers to significantly reduce costs. The IrGT851A will include a set of enhanced features and performance beyond the IrGT821A chipset.

3. IrGT700 for low-power wireless audio applications

Infra-Com is planning to develop a low-power version of the IrGate technology, the IrGT700 series, which can be embedded in battery-powered mobile and handheld applications. The development of new semiconductor chipsets that meet the above definition is intended to promote the development of ultra-low-cost and simple products. Wireless headsets and battery-powered wireless speakers are just two small examples of mass-market applications that seek high-quality, low-power wireless solutions.