Wireless Communication: Spectrum Transmission, Mixers, and Systems

This report delves into the realm of wireless communication, analyzing spectrum transmission techniques such as Direct Sequence Spread Spectrum (DSSS) and Frequency Hopped Spread Spectrum (FHSS), contrasting their operational characteristics, and highlighting their respective advantages and disadvantages. The report further dissects the components of a radio system, encompassing radio transmitters and receivers, alongside an exploration of different mixer types, including active and passive RF mixers, and their configurations (unbalanced, single balanced, and double balanced). The report also provides a brief overview of the reasons for using spread spectrum transmission, such as a wide range of bandwidth, elimination of crosstalk, cost effectiveness, high signal strength, and multiple-user support on a single bandwidth. The report concludes with references to relevant academic sources to support the analysis.

Running head: WIRELESS COMMUNICATION
WIRELESS COMMUNICATION
Name of the Student:
Name of the University:
Author Note:

1WIRELESS COMMUNICATION
The reason of using Spread Spectrum Transmission:
 Wide range of bandwidth.
 It can eliminate crosstalk.
 Cost effective to use.
 The strength of power signal is high.
 Single bandwidth of spectrum can be used by the multiple users.
Comparison and contrast of two methods of spectrum transmission:
The two types of spectrum transmission is Direct Sequence Spread Spectrum (DSSS),
Frequency Hopped Spread Spectrum (FHSS)
Contrast between FHSS and DSSS:
FHSS DSSS
Use of multiple frequencies is done. Use of single frequency is done.
At one instant of the time the user’s frequency is
hard to find out.
The user’s frequency remains same after the
allocation.
Reuse of frequency is permitted (Zou et al.,2015). Reuse of frequency is not permitted.
Strength of the power signal is high Strength of the power signal is low.
It is never affected by any interface. It can be affected by the interfaces.
The use of FHSS is cheaper. Use of DSSS is expensive.
This technique is commonly used. This is not a frequently used technique.

2WIRELESS COMMUNICATION
Similarities between FHSS and DSSS:
 The security issues for both FHSS and DSSS are same.
 Both FHSS and DSSS are the spread spectrum.
Different components of radio system:
Radio transmitter:
Power supply, Amplifier, Oscillator, Antenna, Modulator
Radio receiver:
Antenna, RF amplifier, Detector, Audio Amplifier, Tuner
Different mixers:
There are two types of radio frequency mixer- active (using FET or BJT) and passive ( using
diode). Further, according to the configuration the mixer can be classified into three categories-
unbalanced, single balanced and double balanced.
Active RF mixer:
To increase the strength of the resulting signal the amplifying devices are used in the active RF
mixer(Kaplun et al.,2017). It improves the isolation between several ports. However the power
consumption is high in this technique.

3WIRELESS COMMUNICATION
Figure 1: Active Mixer
(Source: Seo, Lee & Yun,2015).
Passive RF mixer:
In passive mixer one or more diode is used. The non-linear relation of diode between the voltage
and current produces the lower power signal.
Figure 2: Passive Mixer
(Source: Atalla et al.,2017)

4WIRELESS COMMUNICATION
Unbalanced mixer: It uses a single non linear diode. To achieve the best performance LO node
needs to be short circuit (SC).
Single balance mixer: In single balance mixer two diodes are used, it provides isolation between
RF and LO inputs.
Double balanced mixer: There are two types of double balance mixer-star mixer and ring mixer.
It acts as a 2-diode mixer circuit.
Unbalanced, single balanced and double balanced mixers are type of passive mixer.

5WIRELESS COMMUNICATION
References
Atalla, E. S., Zhang, F., Balsara, P. T., Bellaouar, A., Ba, S., & Kiasaleh, K. (2017). Time-
domain analysis of passive mixer impedance: a switched-capacitor approach. IEEE
Transactions on Circuits and Systems I: Regular Papers, 64(2), 347-359.
Kaplun, D. I., Klionskiy, D. M., Gulvanskiy, V. V., Bogaevskiy, D. V., & Kupriyanov, M. S.
(2017, May). Development and study of demodulators for frequency-hopping spread
spectrum signals. In Progress In Electromagnetics Research Symposium-Spring (PIERS),
2017 (pp. 445-448). IEEE.
Seo, D. H., Lee, J. Y., & Yun, T. Y. (2015). Active and passive combined mixer for low flicker
noise and low dc offset. IEEE Microwave and Wireless Components Letters, 25(7), 463-
465.
Zou, Y., Zhu, J., Yang, L., Liang, Y. C., & Yao, Y. D. (2015). Securing physical-layer
communications for cognitive radio networks. IEEE Communications Magazine, 53(9),
48-54.