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The 700 to 2600 MHz frequency band will be used by ever more mobile devices (up to 50 billion by the end of the decade according to forecasts), as it will remain the sweet spot in the frequency spectrum for wide area coverage macro cells due to the optimal propagation loss in the light of frequency reuse. The capacity of the cellular networks has to be increased through:

In addition, solutions are necessary to increase the ACLR and the efficiency of the transmitter, and to reduce the EVM of the receiver and the overall footprint of the antenna, front-end module and transceiver. Indeed, without a reduction in ACLR, the network will become unreliable as more mobile connections will be interrupted or dropped, due to increasing interference. In addition, the inter-band CA and the MIMO technique, which are touted to improve the data rate, will require more complex front-end modules. The MIMO technique in particular requires multiple antennas, front-end modules and transceivers per mobile device, and therefore also a smaller footprint per antenna, front-end module and transceiver, as well as improved efficiency, in order to maintain the current battery autonomy and to prevent sleek mobile device designs from becoming overheated.

State-of-the-art duplexers and power amplifiers, and to a lesser extent antennas, are frequency band-specific components - i.e. they are neither ultra-wideband nor frequency-tunable. Given the ever-increasing number of cellular communication frequency bands to be supported and hence the higher part count, it should be clear that a tunable approach reduces BOM cost...

ChipDesign is working on a tunable antenna and tunable front end IC for next-generation durable and energy-efficient mobile devices. It supports Google's Project Ara and the PhoneBloks Kickstarter campaign. These modular RF components are also being integrated in ChipDesign's IoT development board.

Tunable Antenna

The design of antennas for mobile devices is becoming increasingly challenging. New wireless standards, touting enhanced throughput, require both the coverage of more frequency bands per antenna (to support LTE-A inter-band carrier aggregation for example), as well as more antennas per mobile device (to support IEEE802.11ac or LTE-A MIMO for example). At the same time, mobile devices become sleeker. The Chu-Harrington limit, however, bounds and relates the bandwidth, the efficiency and the volume of electrically small antennas. ChipDesign has therefore developed a multi-functional tunable antenna, which allows multi-band 2G/3G/4G cellular communication, 866 MHz RFID tag reading, L-band DVB-H and S-band SDARS broadcast reception, L2 GPS navigation and 2.45 GHz WLAN (IEEE802.11a/b/g/n/ac) and WPAN (Bluetooth and ZigBee) connectivity. ChipDesign believes that its on-demand-reconfigurable multi-functional antenna paradigm can provide a solution to the spectrum shortage and the MIMO-on-the-handset conundrum and enable the next leap in download capacity for mobile devices.

SDR Antenna

ChipDesign's tunable antenna for mobile devices consists of a low-profile electronically-tunable electrically-small (18.5 cm long) slot antenna, which allows for improved receiver selectivity1,2.

OEM version: 700 MHz - 2.6 GHz - Test hardware influencing the antenna match: 5 V Seeeduino Lotus micro-controller board and 10 cm U.FL to SMA adapter.
Freq. [MHz] Application dB20(|S11|) VSWR leftValue topValue rightValue
700 Cellular -18 1.27 123 2 255
866 ISM -23 1.14 114 27 0
900 Cellular -30 1.05 125 1 34
1227 GPS L2 -18 1.28 96 1 253
1452-1492 DVB-H -11/-4.9 1.8/3.5 255/1 255/1 255/1
1575.42 GPS L1 -6.6 2.75 2 0 2
1800 Cellular -14 1.5 163 1 2
1900 Cellular -31 1.05 141 1 18
2100 Cellular -16.5 1.35 181 1 91
2320-2345 SDARS -7.6 2.42 20/74 192/253 14/13
2450 ISM -7.1 2.5 162 1 2
2600 Cellular -9.2 2.05 0 2 216
See presentation

Seeed version: 433 MHz - 2.1 GHz - Test hardware influencing the antenna match: 5 V Seeeduino Lotus micro-controller board and 10 cm U.FL to SMA adapter.
Freq. [MHz] Application dB20(|S11|) VSWR leftValue topValue rightValue
433 ISM -8.2 2.26 147 0 255
450 Cellular -7.8 2.35 142 0 255
700 Cellular -20 1.2 255 23 255
866 ISM -20 1.2 33 254 94
900 Cellular -22.7 1.2 33 254 111
1227 GPS L2 -25 1.12 112 135 201
1452-1492 DVB-H -11.5/-6.6 1.72/2.7 254/254 254/254 254/254
1575 GPS L1 -5.5 3.2 1 0 1
1800 Cellular -9.8 1.9 121 1 0
1900 Cellular -13.7 1.5 144 0 50
2100 Cellular -31 1.05 101 22 44
2320-2345 SDARS -12.3/-10.8 1.6/1.8 1/1 82/89 0/255
2450 ISM -4.7 3.7 22 133 141
2600 Cellular -2.9 5.8 0 0 0

The unique selling proposition of ChipDesign's tunable antenna:

Price:

Tunable Front End IC

ChipDesign's tunable front end IC architecture for cellular devices is centered around a novel envelope tracking CMOS power amplifier design, featuring integrated tunable duplex filtering. CMOS power amplifier design for cellular front end modules is challenging, because of the stringent requirements for the adjacent channel leakage ratio (ACLR), the bandwidth, the out-of-band noise in the RX band, the power added efficiency (PAE) and the output power.

New capacity-increasing LTE-A techniques, such as inter-band CA and MIMO will further constrain the footprint and the power dissipation of the power amplifier. ChipDesign therefore proposes to implement PA power combining, as well as highly-selective duplex filtering, in the acoustic energy domain, using integrated tunable piezoelectric transducers (see BE patent application 20140066). PA power combining in the acoustic energy domain allows for a footprint and loss reduction4, because reactive components implemented in the acoustic energy domain are smaller and have higher Q factors. In addition, tunable filter stages can be added to suppress noise and spurs, most notably in the RX band. The tunability of the duplex filter stages will furthermore reduce the BOM, as well as the complexity of the antenna switch module, which is to be inserted between the duplexer and the antenna matching tuner.

Contact us for the Verilog IP cores of the digital building blocks and the Verilog-A models for the RF building blocks.

IoT Development Board

The term internet of things (IoT) initially referred to networks of RFID tagged objects in order to ease identification and tracking of these objects. Over the years, though, the meaning of the term has evolved to include countless devices connected wirelessly to the internet. These connections can be sensor-to-machine, machine-to-people (M2P), or machine-to-machine (M2M).

Preliminary specifications:

Footnotes

1. The tunable antenna can be used in conjunction with software defined radios (SDRs) such as for example the Ettus/NI USRP, the FlexRadio, the FUNcube Dongle, the HackRF and the RTL-SDR.

2. UWB antennas, such as the log-periodic and the Archimedean spiral antenna, are electrically-large and therefore do not allow for MIMO on the handset, and offer no selectivity.

3. 3.3 V mbed micro-controller boards will require 3.3 V to 5 V level shifters to be inserted to bias the varactors up to 5 V and cover the entire tunable frequency range of the tunable antenna.

4. Efficiency-enhancing techniques such active load modulation (outphasing and Doherty) or supply modulation (envelope tracking and envelope elimination and restauration) could be used. The implementation of these efficiency-enhancing techniques itself however is also based on power combiners and dividers.