The European GSM system
is by far the most popular standard for portable phones. It has enabled
the spread of dual-band devices using both the 900MHz and 1,800MHz
frequency bands (Figure 2). A triple-band device using the
1,900MHz band (PCS in the U.S.) has also been developed. Manufacturers
of these terminals are pushing for parts that are both smaller and
more complex.
Hitachi Metals is already working to meet these needs, offering 2.0mm
x 1.25mm distribution transformers, RF transformers and couplers.
Recently developed products include a 2.0mm x 1.25mm low pass filter,
diplexer and directional coupler with LPF.
Figure 2. Inside a portable phone
1. Low Pass Filter
The low pass filter, connected to the output side of a power amplifier,
is used to attenuate the harmonics included in signals generated
at double and triple frequencies (Figures 2 and 3). We market
two types, for 900MHz and 1,800MHz frequency bands.
Figure 3: Electrical Characteristics of Low Pass Filter
2. Diplexer
The diplexer is used to separate high and low frequency radio waves
in dual-band portable phones. A low pass filter and high pass filter
are embedded within the circuit. We have commercialized four types
(Figure 4).
Figure 4: Electrical Characteristics of Diplexer
3. Directional Coupler with LPF
This device, usually connected to the output side of the power amplifier,
is used to monitor levels of electrical power transmitted and received
and increase and decrease the level in the amplifier through feedback.
This product combines with the low pass filter in the coupler to
bring size down to 2.0mm x 1.25mm. We are working to reduce these
dimensions further to 1.6mm x 0.8mm.
Inquiries
Information System Components Company
Tel.: +81-3-5765-4429 Inquiry Form
