HFA3101BZ Intersil, HFA3101BZ Datasheet - Page 6

• Manufacturer Part Number: HFA3101BZ
• Description: IC TRANSISTOR ARRAY UHF 8-SOIC
• Manufacturer: Intersil

Specifications of HFA3101BZ

• Frequency: 0Hz ~ 10GHz
• Number Of Mixers: 1
• Noise Figure: 1.7dB
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Voltage - Supply: -
• Rf Type: -
• Gain: -
• Secondary Attributes: -

The use of the HFA3101 as modulators has several
advantages when compared to its counterpart, the diode
doublebalanced mixer, in which it is required to receive
enough energy to drive the diodes into a switching mode and
has also some requirements depending on the frequency
range desired, of different transformers to suit specific
frequency responses. The HFA3101 requires very low
driving capabilities for its carrier input and its frequency
response is limited by the f
the layout techniques being utilized.
Up conversion uses, for UHF transmitters for example, can be
performed by injecting a modulating input in the range of
45MHz to 130MHz that carries the information often called IF
(Intermediate frequency) for up conversion (The IF signal has
been previously modulated by some modulation scheme from a
baseband signal of audio or digital information) and by injecting
the signal of a local oscillator of a much higher frequency range
from 600MHz to 1.2GHz into the carrier input. Using the
example of a 850MHz carrier input and a 70MHz IF, the output
spectrum will contain a upper side band of 920MHz, a lower
side band of 780MHz and some of the carrier (850MHz) and IF
(70MHz) feedthrough. A Band pass filter at the output can
attenuate the undesirable signals and the 920MHz signal can
be routed to a transmitter RF power amplifier.
Down conversion, as the name implies, is the process used
to translate a higher frequency signal to a lower frequency
range conserving the modulation information contained in
the higher frequency signal. One very common typical down
conversion use for example, is for superheterodyne radio
receivers where a translated lower frequency often referred
as intermediate frequency (IF) is used for detection or
demodulation of the baseband signal. Other application uses
include down conversion for special filtering using frequency
translation methods.
An oscillator referred as the local oscillator (LO) drives the
upper quad transistors of the cell with a frequency called
ω
ω
the IF output will contain the sum and difference of the
frequencies
become negative when the frequency of the local oscillator is
lower than the incoming frequency and the signal is folded
back as in Figure 2.
NOTE: The acronyms R F , IF and LO are often interchanged in the
industry depending on the application of the cell as mixers or
modulators. The output of the cell also contains multiples of the
frequency of the signal being fed to the upper quad pair of transistors
because of the switching action equivalent to a square wave
multiplication. In practice, however, not only the odd multiples in the
case of a symmetrical square wave but some of the even multiples
will also appear at the output spectrum due to the nature of the actual
switching waveform and high frequency performance. By-products of
the form M*
integers are also expected to be present at the output and their levels
are carefully examined and minimized by the design. This distortion
is considered one of the figures of merit for a mixer application.
C
M
. The lower pair is driven by the RF signal of frequency
to be translated to a lower frequency IF . The spectrum of
ω
ω
C
C
+ N*
and
ω
ω
M
M
with M and N being positive or negative
. Notice that the difference can
T
of the devices, the design and
6
HFA3101
The process of frequency doubling is also understood by
having the same signal being fed to both modulating and
carrier ports. The output frequency will be the sum of
and
frequency by 2 and a zero Hz or DC frequency equivalent to
the difference of
technique in use today where a process of down conversion
named zero IF is made by using a local oscillator with a very
pure signal frequency equal to the incoming RF frequency
signal that contains a baseband (audio or digital signal)
modulation. Although complex, the extraction or detection of
the signal is straightforward.
Another useful application of the HFA3101 is its use as a high
frequency phase detector where the two signals are fed to the
carrier and modulation ports and the DC information is
extracted from its output. In this case, both ports are utilized in a
switching mode or overdrive, such that the process of
multiplication takes place in a quasi digital form (2 square
waves). One application of a phase detector is frequency or
phase demodulation where the FM signal is split before the
modulating and carrier ports. The lower input port is always 90
degrees apart from the carrier input signal through a high Q
tuned phase shift network. The network, being tuned for a
precise 90 degrees shift at a nominal frequency, will set the two
signals 90 degrees apart and a quiescent output DC level will
be present at the output. When the input signal is frequency
modulated, the phase shift of the signal coming from the
network will deviate from 90 degrees proportional to the
frequency deviation of the FM signal and a DC variation at the
output will take place, resembling the demodulated FM signal.
The HFA3101 could also be used for quadrature detection,
(I/Q demodulation), AGC control with limited range, low level
multiplication to name a few other applications.
Biasing
Various biasing schemes can be employed for use with the
HFA3101. Figure 3 shows the most common schemes. The
biasing method is a choice of the designer when cost,
thermal dependence, voltage overheads and DC balancing
properties are taken into consideration.
Figure 3A shows the simplest form of biasing the HFA3101.
The current source required for the lower pair is set by the
voltage across the resistor R
lower transistor. To increase the overhead, collector resistors
are substituted by an RF choke as the upper pair functions
as a current source for AC signals. The bases of the upper
and lower transistors are biased by R
respectively. The voltage drop across the resistor R
be higher than a V
that the collector to base junctions of the lower pair are
always reverse biased. Notice that this same voltage also
sets the V
for the optimization of gain. Resistors R
zero for applications where the input signals are well below
25mV peak. Resistors R
ω
M
which is equivalent to the product of the input
CE
of operation of the lower pair which is important
ω
C
BE
and
with an increase sufficient to assure
EE
ω
M
are used to increase the linearity
. Figure 2 also shows one
BIAS
less a V
B1
EE
and R
BE
are nominally
drop of the
B2
2
must
ω
C