## Analysis of the Tuggle Front End – Part IIIAs a first approximation, the 3dB bandwidth of
the antenna-ground-lossy tuner system under matched load conditions can be
computed assuming that the L A precise model for accurate bandwidth computation
is shown in Fig.1.a below. R
## Simulation resultsFigures 2.a through 2.f illustrate simulation
results for circuit of Fig.1.a at resonance frequencies of 530kHz, 1MHz and
1.7MHz. Assumed values for r and Ca are 30 ohms and 200pF, respectively. The
values for R Figures 3.a through 3.f show simulation results
for circuit of Fig.1.b at resonance frequencies also of 530kHz, 1MHz and
1.7MHz. Again, r = 30 ohms and Ca = 200pF. Re = 2Rs
The Y axis on the graphics represents voltage
across Re in decibels, with Ea being a 1 volt-amplitude unmodulated carrier.
We shall now proceed to calculate the 3dB
bandwidth of circuit of Fig.1.b. Mesh current is given by: where: The amplitude-frequency relationship for I is
determined by: At the -3dB points: The corresponding frequencies must satisfy the
equation: or:
Let w with the following approximations:
Then: or: which simplifies to: Now, if w this is:
From part II of our study we can obtain the
following expression for R Then, the 3dB bandwidth is given by: in radians per second. Next, we shall compute the bandwidths at three
frequencies: 530kHz, 1MHz and 1.7MHz. Results are tabulated below.
Results for BW are very close to those obtained
from simulation of circuit of Fig.1.b.
Ramon Vargas Patron
Lima-Peru, South America
April
11 |