Linear transceiver architectures

Digitally Assisted RF Architectures: Two Illustrative Designs

“…The total number of LUT entries was 1024, and each entry was the result of 32 separate measurements that were averaged in order to reduce the effects of thermal noise. The total training time required was thus 6.55 s. 8 The only way this experiment would have failed would have been if nonlinear memory effects were strong enough to dominate the distortion products. (a) How the system linearizes a 40-MHz-wide channel using single-carrier 16-QAM modulation.…”

“…14.1 acts as two independent feedback loops: one for the I channel and one for the Q channel. However, these systems are vulnerable to an apparent phase difference between the local oscillator (LO) sources, and the associated problems are mentioned in practically all literature on the subject [4][5][6][7][8][9][10][11][12][13][14]. This phase difference is represented as φ in the figure.…”

Highly integrated RF-IC's for GSM and DECT systems-A status review

“…We find solutions on the market with a one-chip transceiver [6] and additional external discrete components. Also, two IC's splitted horizontally into a receiver and transmitter [9] or splitted vertically into a front-end RF part for up/down conversion and back-end IF part for modulation/ demodulation were published. Still, solutions with a high level of discrete transistors and passive components were produced.…”

“…Here RF-VCO modules do not have such a high market share than in the cellular application. The DECT system bandwith is only 1) zero IF /or very low IF concept with additional baseband filtering and variable gain baseband amplifier in front of the A/D converters: one company has now started production with this concept; 2) dual conversion receiver with an IF 110 MHz and a second IF of 5-6 MHz, with additional passive filtering followed by IF limiter amplifier and demodulator: the receiver part of the first generation was dominated by dual conversion receiver design, and now production is more and more being replaced by a single conversion concept; 3) heterodyn receiver with an IF of 110 MHz and a limiter amplifier and demodulator at this frequency: this concept gets more and more market share, because of its high sensitivity and simple and low-cost application [9], [14]. If the zero-IF or very low concept is used, additional analog baseband gain control, filtering, and processing is required or two additional baseband A/D converters are needed.…”

“…8): 1) low IF frequency-modulation (100-300 MHz) followed by upconversion mixing and passive image filters; this was published only in the very beginning, but is not in volume production now; 2) open-loop modulation with a local oscillator running on half the transmit frequency; this concept has highest market share [9], [18]. The low IF modulation and upconversion mixing according to concept 1 has the advantage that there are no frequency drift problems during TX time slot.…”