| Summary: | 碩士 === 逢甲大學 === 資訊電機工程碩士在職專班 === 94 === Nowadays, in the powerful and arrogant wireless communication
market, there are lots of wireless communication technologies, such as
Bluetooth, 802.11 series and so on. The above-mentioned technologies
used ISM band frequency, therefore, each user must comply the standard
with each system, which will prevent the interference of communication.
In order to know the system whether comply with the standard or not, we
can use spectrum analyzer to measure the circuit. Therefore, we would
like to design and implement a computerize spectrum analyzer by
referring the related technologies of spectrum analyzer. The advantages of
the computerize spectrum analyzer are convenient, mobility,
practicability and also can reduce the size and cost of the whole structure.
The baseband controlled module of the computerize spectrum
analyzer is mainly comprised by several integrated circuits (IC) and
microcontroller (PIC18F452). Then we can use the baseband module
interface as the data transmission interface of the computerize spectrum
analyzer. The main structure of the baseband module interface is
comprised by the controlled circuits of radio frequency (RF), intermediate
frequency (IF) and the data transmission interface. Therefore, our
research will focus on the design and implementation of the half wave
envelope detection circuit and the USB transmission interface.
As for the circuit-controlled part, we will compose the software
programming to control the 18F452 microprocessor, which is produced
by Microchip Company. Then the microprocessor will control the phase
locked loop (PLL), RF, IF, A/D sampling rate and the USB interface
circuit.
We utilize the MB15E03SL/07SL as our PLL controlled circuit,
which is made by Fujitsu Company (03SL is used for 870.3 MHz PLL
circuit; 07SL is used for 0.75~1.5 GHz and 2119 MHz PLL circuit). The
main part pf the PLL circuit is the IC, which includes 2 groups of divider
and RF unit circuits (VCO, phase detector, low-pass filter and amplifier).
We utilize the AD 9283 IC as our A/D converter, which is made by
Analog Device Company. The advantages of this IC are low noise, 8-bit
parallel output and so on. We utilize the SA 626 IC as our signal strength
detection circuit, which is made by Philips Company and this circuit will
not effect the amplitude of the input signal.
As for the data transmission part, the RF signal will pass through the
mixer at the front end for down conversion. After that we can obtain the
10.7 MHz signal, then by using the envelope detection circuit, we can
obtain the amplitude value of the voltage and this amplitude will operate
with the A/D converter and 18F452. Then by using the USB interface, the
A/D converted signal will transmit to PC and the user can use the
software, which will recover the amplitude of the RF signal and finally
display at the screen of the PC.
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