Because the Device is under nonlinear operation state.So there is homonic.
I suggest you use the lpf behavior match circuit ot Band pass circuit type.
That is a ref:
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 52, NO. 3, MARCH 2004 927
Amplifier Linearization Using Compact Microstrip
Resonant Cell—Theory and Experiment
Tsz Yin Yum, Student Member, IEEE, Quan Xue, Member, IEEE, and Chi Hou Chan, Fellow, IEEE
Abstract—This paper presents a novel technique for reducing
the intermodulation distortions (IMDs) in power amplifiers. In this
method, both second- and third-harmonic components generated
by the transistor are reflected back simultaneously by the compact
microstrip resonant cell (CMRC) at the input port with proper
phases to mix with the fundamental signal for the reduction of
IMDs. A rigorous mathematical analysis on the effectiveness of
multiharmonic reflections has been formulated and derived using
the Volterra series. Moreover, the delay mismatch factor of the
proposed method is analytically studied and the result shows that
a better tolerance to the delay error can be achieved by using
CMRC circuitry. Standard two-tone test measurements reveal 32-
and 22-dB reductions for the third-order IMD and fifth-order
IMD, respectively, without affecting the fundamental signal at
2.45 GHz. Meanwhile, the proposed approach gives a peak power
added efficiency of 53% with 11.5 dB transducer gain and 15 dBm
output power for a single-stage SiGe bipolar junction transistor.
The adjacent channel power ratio (ACPR) is 55 dBc for a data
rate of 384-kb/s quadrature phase shift keyed modulated signal
with 2-MHz spanning bandwidth, and this ACPR is maintained
for a broad range of output power level.
Index Terms—Amplifiers, compact microstrip resonant cell
(CMRC), harmonics suppression, intermodulation, linearization.