SeeedStudio - Software Defined Radio Antenna - DIY Maker Open Source BOOOLE

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. 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.

Features:

- Band coverage:
- Well-matched (dB20(|S11|) < -10 dB, VSWR < 1.9) frequency bands are the 700 MHz, 866 MHz (ISM), 900 MHz, 1227 MHz (GPS L2), 1800 MHz, 1900 MHz, and 2100 MHz band. For the cellular bands, the full TX band, the duplex gap, and the full RX band are covered, allowing contiguous and non-contiguous intra-band CA with an instantaneous bandwidth up to 100 MHz, if applicable.
- Poorly-matched (dB20(|S11|) < -6 dB, VSWR < 3) frequency bands are the 433 MHz (ISM) and 450 MHz band for the Seeed version.
- The presence of the test hardware affects the return loss, as any efficient antenna is sensitive to its surrounding. Return loss measurements were done with the tunable antenna plugged into an Arduino Due and a Seeeduino Lotus micro-controller board, and the results can differ by as much as 100 MHz for the same bias settings. At the edges of the tunable frequency range - i.e. at 400 - 433 MHz ,which can not be compensated anymore by biasing the RF varactor diodes differently.
- Efficiency: TBD. The bandwidth and efficiency of electrically-small antennas with sufficient instantaneous bandwidth are bounded by the Chu-Harrington limit.

Specification:

- Seeed version - Test hardware influencing the antenna match: Seeeduino Lotus micro-controller board and 10 cm U.FL to SMA adapter.
- 2. 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.?