Getting back to Sunblazer though, there was an antenna issue. The probe’s operating frequency was to have been 40 MHz. The receiving antenna was an array of half-wave dipoles arranged in a matrix over a large area of land somewhere in Texas. Each dipole fed a 75-ohm twin-lead, each with a variable delay line. Signal propagation time from each dipole to its receiver connection was made variable. By choosing the individual delay times properly, the array of dipoles became a steerable array. The main lobe’s direction of reception could be pointed differently by selecting the delay times for each feedline.

Organizations such as the Federal Communications Commission (FCC) and the International Telecommunication Union (ITU), and even the Amateur Radio Relay League (ARRL), work hard to organize frequency-spectrum use into carefully organized and managed bands of frequencies for each application. This includes, for example, the 2.4- to 2.5-GHz band for Wi-Fi wireless local-area networks (WLANs) and their essential wireless access to the internet for many different electronic devices. Starting within the kilohertz range for AM radios through VHF/UHF broadcast television channels (Fig. 1), spectrum use is carefully monitored to prevent unwanted overlapping of signals that can interfere with the reception of designed signals.

The 2.4-GHz span is part of the unlicensed industrial, scientific, and medical (ISM) band of frequencies intended for widespread and easy-to-use wireless applications. One of those applications, though, is the microwave oven at 2.45 GHz

Wreaking Havoc on Wi-Fi

Although microwave ovens are designed to operate with relatively low levels of RF radiation, small amounts of leaking RF energy are enough to jam or interfere with the operation of nearby Wi-Fi equipment and prevent wireless access. Interference within the 2.4-GHz band may not be enough to prevent a Wi-Fi system from operating altogether, but may surface as slow internet access speeds and slow computer file transfers using the Wi-Fi system.

Interference results between fixed in-home wireless networks when a close-enough neighbor has set a wireless router to the same channel at the same frequency as the Wi-Fi system next door.

Interference occurs when attempts are made to use multiple signals within the same frequency channel at the same time without some form of synchronization.

In contrast to unlicensed ISM band frequencies, frequency bands licensed by the FCC, such as the cellular radio bands at 824 to 849 MHz and 869 to 894 MHz, are organized into what became 25-MHz channel blocks for different cellular carriers.

As more wireless applications crowd into the available frequency bands, signal congestion is forcing RF/microwave system designers to find ways to cope with unwanted signals.

While 4G LTE and LTE-Advanced technologies are still being deployed worldwide, the next generation in wireless communication promises a paradigm shift in throughput, latency, and scalability. By 2025, the emerging wireless 5G market is expected to reach a total value of $250B1. 5G is projected to be 100 times faster than 4G LTE and 10 times faster than Google Fiber (a physical connection). To put this into perspective, a high-definition movie will take less than a second to download on 5G, compared to 10 minutes on 4G LTE. Data rates will be further improved by using massive multiple-input multiple-output (MIMO) technology that originally were designed for use in IEEE 802.11n Wi-Fi networks.

The inconvenient truth of future 5G networks is that their increased high-speed bandwidth, and the use of the millimeter wave spectrum (the radio spectrum above 30 gigahertz) to achieve it, comes at a price: Those radio signals barely propagate around the corners of buildings.

To overcome this issue, the strategy has been a combination of small cells with massive multiple-input multiple-output (MIMO) antennas to increase coverage. Small cell deployment will be so extensive that the Small Cell Forum predicts 5G small cell will overtake 4G small cells by 2024. The total installed base of 5G or multimode small cells will reach 13.1 million by 2025, constituting more than one-third of the total small cells in use.

Modern wireless radio transmitter designs encompass real IF (intermediate frequency) transmitters, complex IF transmitters, and zero-IF transmitters. At present, these transmitters continue to shuffle data through analog paths. There are limitations in the analog domain which impact the performance, capacity, and cost of the system, however.

To meet the demands for higher bandwidth communications, IC manufacturers have developed direct-to-RF architectures that provide excellent spurious, low-noise performance with output update rates in the giga-samples-per-second (Gsps) range.

This company’s resonator technology could very well become a key factor in enabling filters for 5G applications.

The smartphones that permeate today’s world wouldn’t be possible without the RF filters found inside of them. And with 5G rapidly approaching, the need for high-frequency filter solutions is only going to intensify. One company that’s making a significant impact within the mobile-communications filter space is Resonant. The firm recently unveiled its new technology, which it believes holds great promise for future RF filters for 5G mobile devices.

“We’re a licensing company,” says Mike Eddy, vice president of marketing at Resonant. “We don’t make the filters, multiplexers, etc. We create the designs for our customers and then we license those designs on a per-unit royalty basis. Also, we announced the addition of filter IP library products to our offerings. Library products are designed and developed by Resonant against one of its foundry partner’s processes, tested against the latest industry and phone board requirements, and then made available to license.”

Gallium-nitride technology figures to play a significant role in sub-6-GHz 5G applications to help achieve goals like higher data rates.

This tiny flip-chip digital attenuator can control an attenuation range as wide as 31.5 dB in either 0.5- or 1.0-dB steps far into the mmWave frequency range.

Fujitsun Laboratorioes-yksikkö ilmoittaa kehittäneensä ensimmäisen antennipaneelin, jolla voidaan samanaikaisesti palvella neljää 5G-käyttäjää 28 gigahertsin taajuudella. Antennipaneeli mahdollistaa yhteensä yli 10 gigabitin datakaistan.

Fujitsun antennissa on 128 antennielementtiä, joiden sätielemän signaalin vaihetta voidaan tarkasti kontrolloida. Lisäksi signaalein väliset häiriöt on pystytty suodattamaan.