Design of a multimode tunable low noise amplifier for software defined radios

Abstract

This Letter presents the design and analysis of a tunable low noise amplifier (LNA) capable of achieving single band, dual band and wideband operations. The circuit features a modified tunable open stub matching to achieve a reconfigurable multiband response. The LNA adopts a varactor diode in the input matching stage to achieve reconfigurable modes. Two bias conditions for the varactor diode are analysed. The forward bias condition yields a wideband mode (1.6 to 2.5 GHz) and zero bias results in a concurrent dual band mode (0.9 and 1.7-2.5 GHz). In reverse bias condition, the bias voltage of varactor diode (V d−rb) can be tuned to achieve one single band mode (1 GHz), and a tunable concurrent dual band mode, where the first band is fixed at 1 GHz and the second band is continuously tunable from 1.7 to 2.5 GHz. The LNA is fabricated in microwave integrated circuit process on an FR-4 board. The measured power gain is 7-15 dB and noise figure is 1.2-2.2 dB across all bands. The measured 1 dB compression (P 1 dB) is −4, −3 and −6 dBm at 0.9, 1 and 2.4 GHz, respectively.

Design of compact highly matched broadband balanced low‐noise amplifier at X‐band using CRLH transmission lines

“…As can be seen from Equation (5), by properly adjusting the seriesÀparallel resonance frequencies as well as the transformer's characteristic impedance, and using impedances marked in Figure 4, the input impedance theoretically can be set to any favorable value; however, there is a limitation to this procedure. Band-width, matching quality, and complexity of the matching are closely related to each other according to the Bode-Fano criteria.…”

“…Designing wideband matching networks is an intricate and sophisticated process, and may be either carried out by synthesis method or computer optimizations. 1 According to the literature, there are three major solutions to realize wideband matching networks 2,3 : (1) gain (S 21 ) compensation by creating mismatch in the input-output, [4][5][6][7][8][9][10][11][12] (2) balanced amplifier method, [13][14][15][16] and (3) negative feed-back. [17][18][19][20][21][22][23] Each of these methods has advantages and disadvantages over one another, and microwave engineer should carefully consider the consistency between performance and application before design process.…”

“…According to the literature, there are three major solutions to realize wideband matching networks 2,3 : (1) gain ( S 21 ) compensation by creating mismatch in the input–output, 4–12 (2) balanced amplifier method, 13–16 and (3) negative feed‐back 17–23 . Each of these methods has advantages and disadvantages over one another, and microwave engineer should carefully consider the consistency between performance and application before design process.…”

“…K‐band LNA proposed in Reference 4 uses substrate integrated suspended line (SISL) technology and achieves 1 dB NF, 27.7 dB peak gain, and 6.1 dBm compression point at output; however, due to the use of multiple substrate layers, fabrication process is not straight‐forward. In Reference 5, tunable LNA capable of achieving dual and wideband operation based on open‐stub matching networks and low‐cost substrate is proposed for software defined radio. Proposed structure achieves 7.5–14 dB gain, 2 dB NF, and an input return loss better than −8 dB throughout the band; while 10 dB S 11 bandwidth is limited to 800 MHz.…”

Design of a compact multifunctional power divider loaded with short‐ended stub

“…Current and future communication systems necessitate reconfigurable structures and extended features, which are taken into account in the development of microwave devices such as: filters, 1 antennas, 2 and amplifiers. 3 This holds true for power dividers as well, as reconfigurable power dividers for 5G Cellular networks have recently been proposed. [4][5][6][7][8] Reconfigurability refers to the ability to adjust or control a power divider's features dynamically while still maintaining acceptable overall performance.…”