In recent years, there are some new research results about signal injection including the improvement of the fundamental signal power of TWT by harmonic injection [4, 12], the harmonic and intermodulation distortions associated with two-tone modulation , the suppression of IMD3
by harmonic injection , and the particle swarm optimization algorithm (PSO) which are applied to suppress IMD [15,16].
where [a.sub.1] and [a.sub.3] represents the amplitude at fundamental frequency and IMD3
produced by the PA, respectively while [b.sub.3] is the IMD3
amplitude produced by the pre-distorter.
Work Frequency Efficiency  2.3 GHz Max PAE: 32.1%  2.14 GHz PAE: 46% 6 dB-BOP  2.5 GHz PAE: 43% 8 dB-BOP  2.01 GHz Max PAE: 43.6% This work 3.4-3.5 GHz DE: 40.1% (6 dB) CRLH-TL 30% (9 dB) This work 3.4-3.5 GHz DE :46% (6 dB) Traditional 31.8% (9 dB) Work Max [P.sub.out] Linearity  31 dBm Max IMD3
: -47 dBc  44.5 dBm ACPR: -30 dBc @ 38 dBm  47 dBm ACPR: -35 dBc @ 39 dBm  42.5 dBm IMD3
: -40 dBc @ 38 dBm This work 46 dBm ACPR (With DPD): CRLH-TL -49.6 dBc @ 37 dBm This work 46 dBm ACPR (With DPD): Traditional -42.9 dBc @ 37 dBm Work Signal  CW  W-CDMA  UMTS-LTE (10 MHz)  Two Tone Signal This work 16 QAM CRLH-TL (40 MHz) This work 16 QAM Traditional (40 MHz)
(dBc) Gain (dB) Pout (dBm) PAE (%) Simulated data 29.3 12.38 37.28 49.3 Measured data 28.5 12.4 37.4 50 Table 7.
The figure shows that IMD3
increases with the increase in m.
The obtained improvement in P1dB, PAE, IMD3
and IMD5 obtained were 0.45 dB, 9.1 percent, 4.4 dB and 4.5 dB, respectively.
At around -40 dBc IMD3
, the output power increases by 2 dB, while the efficiency also improves by 4 percent.
Figure 5 shows the IMD3
performance of the TGA4905, 40 dBc at 20 dBm [P.sub.out].
The approach to obtain a correct answer is to measure the gain at an IMD3
frequency of 1 MHz for G(1 MHz) = 95 dB.
TABLE I TWO CATEGORIES OF NOISE SOURCES IN RF RECEIVERS FOR WIRELESS COMMUNICATIONS Intrinsic Noise Sources Extrinsic Noise Sources Tx noise leakage in Rx band Intermodulation distortion (IMD2, IMD3
) Reciprocal mixing product Thermal noise (NF) Cross-modulation product Image signal Imperfectly filtered interferers References
The fundamental and third-order intermodulation power (IMD3
) calculated under bias A and B are shown in Figure 8,.
Third-order inter-modulation distortion (IMD3
), fifth-order intermodulation distortion (IMD5) and PAE for the Doherty-I and class B amplifiers, and for the Doherty-II and class AB amplifiers versus average output power are compared in Figures 9 and 10, respectively.