Antena

Telah dilakukan  percobaan Analisa Antena Patch dengan Pola Radiasi Antena dengan tujuan untuk menentukan pola radiasi antenna patch dalam skala logaritmit dan linier, memahami sifat-sifat dan prinsip dari antenna dan memahami jenis-jenis pola radiasi antenna. Untuk melakukan percobaan ini, erlebih dahulu dirangkai alat seperti antena CPWF patch, network analyzer, kabel port, dan papan lingkaran penunjuk sudut. Lalu, dilakukan pengamatan dari 0o dengan 360o dengan selisih 5o setiap variasi sudut. Dari asil percobaan ini, diperleh frekuensi dan intensitas radian. Dari hasil percobaan ini dapat ditentukan grafik hubungan sudut dengan intensitas linier dimana  pola radiasi yang pada percobaan ini adalah omnidirectional yaitu gelombangnya bergerak kesegala arah yang ditujukkan pada grafik hubungan sudut dengan intensitas radian sedangkan  unidirectional mensinyalkan ke suatu daerah saja, yang ditunjukkan hubungan sudut dengan intensitas linier. Dari percobaan ini diketahui bahwa antenna dapat menerima dan memancarkan sinyal. Prinsip yang digunakan adalah prinsip gelombang elektromagnetik yang diubah menjadi energy listrik dan sebaliknya.

This paper discusses a new implementation of a Gaussian minimum-shift keying (GMSK) modulator and demodulator on the European Space Agency (ESA)'s common deep-space receiver-the Intermediate Frequency Modem System (IFMS), which is a software radio based platform. The GMSK demodulator is needed for ESA's deep-space and near-Earth missions, starting with the Herschel-Planck satellites in 2008. The implementation requirements and hardware restrictions from the IFMS lead to the need for a significant simplification versus the optimum demodulation approach. In part, this can be achieved by using a demodulator based on the Laurent decomposition, yet further simplifications and changes to obtain a feasible implementation were necessary. The presented GMSK demodulator was directly implemented on the existing IFMS receiver without requiring any hardware changes. Measurements with the demodulator showed only a marginal technical degradation in the order of 0.1-0.3 dB for the chosen approach. Furthermore, for testing purposes, a GMSK modulator was implemented on the same platform.

A technique for array diagnosis using a small number of measured data acquired by a near-field system is proposed. The technique, inspired by some recent results in the field of compressed sensing, requires the preliminary measurement of a failure-free reference array. The linear system relating the differ- ence between the field measured using the reference array and the field radiated

We present a closed-form expression for the the input impedance of a microstrip probe in a rectangular waveguide. The probe extends only part way across the waveguide and is therefore compatible with RF components that require an open circuit at low frequencies. Our analysis is based on the spectral-domain method and is able to take into account the orientation of the antenna with respect to the direction of propagation. We have examined the validity of our model by carrying out extensive impedance measurements at 5GHz. In those cases where the probe did not extend more than half way across the waveguide, excellent agreement was obtained. We show that the bandwidth of a probe that stretches only part way cross the waveguide is very much greater than the bandwidth of a probe that stretches all of the way across the waveguide and that is earthed at both ends. Moreover, the input resistance is lower and more suited to submillimetre-wave detectors such as SIS tunnel junctions. Our expression suggests that it should be possible to develop low-impedance, wideband probes for nearlydouble-height waveguide, and this implies that the upper frequency limit to which probes and waveguides can be manufactured can be extended well into the THz frequency range. A related, and often neglected consideration, is that the ohmic loss associated with an oversized waveguide is very much smaller than the ohmic loss associated with a reduced-height waveguide.

Operator telepon seluler saat ini memisahkan pemakaian antena 2G (GSM) Dual Band dan
antena 3G (WCDMA) yang ditempatkan pada site yang sama. Hal ini jelas tidak ekonomis
karena harus membangun sistem kabel feeder dan antena terpisah dari dua sistem tersebut.
Walaupun menggunakan tower yang sama, investasi yang dibutuhkan tetap besar. Dalam
studi ini akan dibahas penggunaan antena Triple Band yang digunakan secara bersama
antara sistem 2G dan 3G pada suatu site guna menekan biaya investasi pembangunan tower
kedua sistem tersebut. Antena Triple Band adalah antena yang range frekuensinya antara
800 MHz – 2200 MHz (Kathrein, 2006). Dari range frekuensinya ini antena Triple Band
dapat bekerja pada sistem 2G maupun 3G. Membangun sistem 3G yang ditempatkan pada
suatu site yang sama dengan sistem 2G dengan memanfaatkan antena Triple Band, maka
pelanggan yang menggunakan sistem 2G maupun sistem 3G pada area tersebut dapat
dilayani sekaligus dengan satu antena tersebut. Bila operator ingin menambahkan sistem 3G
pada suatu site/tower BTS 2G, maka operator tidak perlu lagi membangun antena 3G, karena
harus memasang line kabel feeder baru dan memasang antena 3G. Dengan menggunakan
antena Triple Band, cukup menggantikan antena GSM yang ada pada site/tower tersebut
dengan antena Triple Band kemudian mengkonekneksikan RBS 2G yang telah ada
sebelumnya dengan RBS 3G yang baru dipasang dengan menggunakan line kabel feeder yang
sebelumnya untuk antena GSM. Bila satu RBS 2G dan RBS 3G dibangun secara terpisah
pada suatu site, setiap sistem tersebut optimal masing-masing memerlukan 3 antena. Maka
untuk satu site/tower diperlukan minimal 6 antena. Dengan menggunakan antena Triple Band
kedua sistem tersebut akan diintegrasikan pada antena yang sama. Sehingga pada satu
site/tower antena yang diperlukan untuk kedua sistem tersebut adalah 3 antena.

It is shown that internal clutter motion, aircraft crabbing, scattering from near-field obstacles, and channel mismatch can limit the effectiveness of space-time processing in eliminating airborne clutter. An analytical expression is developed to show how each of these effects produces a deterioration in the signal-to-clutter-plus-noise ratio achievable. By studying the spectral decomposition of the covariance matrix, it is found that the effects of both internal clutter motion and crabbing can either be compensated by artificially adding noise or by processing more pulses. A near-field obstacle produces a spread of the clutter into all of sine azimuth-Doppler space. It is shown that the space-time processor attempts to compensate for this effect by placing a near-field null on the obstacle. Thus, adding more elements is much more effective in eliminating this effect than is processing more pulses. Channel mismatch can be alleviated by controlling the dispersive errors more tightly and by increasing the number of receive elements

This work investigates the effect of limiting source signals to finite-alphabet on the secrecy rate of a multi-antenna wiretap system. Existing works have characterized maximum achievable secrecy rate or secrecy capacity for single- and multi-antenna systems based on Gaussian source signals and secrecy code. Despite the impracticality of Gaussian source, its compact closed-form expression of mutual information motivated broad use of Gaussian input assumption. For practical consideration, we study the effect of finite discrete-constellation on instantaneous and ergodic secrecy rate of multiple-antenna wire-tap channels. Our results demonstrate substantial difference between systems involving finite-alphabet inputs and systems with Gaussian inputs. Results from Gaussian inputs serve as upper-bound of secrecy rate for practical systems with finite alphabet inputs.

The current distribution and radiation patterns of a printed thin-wire circular loop antenna are computed rigorously using an entire-domain moment method analysis. A computationally efficient algorithm using the FFT is implemented. The input impedance of the loop and the far-zone radiation pattern are computed as a function of the substrate dielectric constant and thickness and as a function of the loop circumference. The space-wave launching efficiency and z-directed power gain of the antenna are also computed as a function of the substrate thickness.