LO System
LO synthesizer 1
- Block Diagram
- VCO 1 and VCO 2
- Block Diagram
- Voltage Controlled Oscillator 1
The Voltage Controlled Oscillator 1 (VCO1) is used in the D46 PIU and is a part of the LO Synthesizer 1.
The range of working for oscillator is predefined and is 100MHz to 200MHz with a step size of 1MHz. There is a "guaranteed range of operation" for the oscillator typically from 10% to 90% of the range of oscillator specified. For VCO 1 the range of operation is from 95MHz to 208MHz without any hitch.
The DC supply given to the oscillator is given through MCM-controlled Relays. The DC power to the oscillator is switched off when not in use to eliminate any chance of system produced spurious signal affecting the receiver performance.
- Voltage Controlled Oscillator 2
The Voltage Controlled Oscillator 2 (VCO2) is used in D46 PIU and is a part of LO Synthesizer 1.
The range of working for oscillator is predefined and is 200MHz to 400MHz with a step size of 1MHz. There is a "guaranteed range of operation" for the oscillator typically from 10% to 90% of the range of oscillator specified. For VCO 1 the range of operation is from 190MHz to 420MHz without any hitch.
The DC supply given to the oscillator is given through MCM-controlled Relays. The DC power to the oscillator is switched off when not in use to eliminate any chance of system produced spurious signal affecting the receiver performance.
- 200 MHz Low Pass Filter
The 200 MHz Low Pass Filter acts as a frequency selective network which passes all the frequencies below its high cut off level. Some of the important characteristics are enlisted below.
- 410 MHz Low Pass Filter
The 410 MHz Low Pass Filter acts as a frequency selective network which passes all the frequencies below its high cut off level. Some of the important characteristics are enlisted below.
- Current Monitor
The PCB for the Current Monitor has 8 stages of amplifier and is used for:
- Amplification of the voltage drop in the (typically 100mV) dropping resistor in the series between a 3-pin regulator and a load and
- Amplification of the detector voltage for the LO power and VCO Power, from SP2T and DISET units respectively
- Monitor Multiplexer
The Monitor Multiplexer acts as a 32:2 multiplexer.
- Power Supply
The power supply is made up of an AC distribution panel and a DC distribution panel and both are employed for different purposes.
- VCO 3
- Voltage Controlled Oscillator 3
The Voltage Controlled Oscillator 3 (VCO3) is used in the D47 PIU and is a part of the LO Synthesizer 1.
The range of working for oscillator is predefined and is 400MHz to 600MHz with a step size of 5MHz.
There is a "guaranteed range of operation" for the oscillator typically from 10% to 90% of the range of oscillator specified. For VCO 1 the range of operation is from 325MHz to 680MHz without any hitch.
The DC supply given to the oscillator is given through MCM-controlled Relays. The DC power to the oscillator is switched off when not in use to eliminate any chance of system produced spurious signal affecting the receiver performance.
The VCO 3 is favored to VCO 2 for synthesizing the frequencies in the range 320 to 400 MHz as the prior operates at lesser control voltage than VCO 2.
- 650 MHz Low Pass Filter
The 650 MHz Low Pass Filter acts as a frequency selective network which passes all the frequencies below its high cut off level. Some of the important characteristics are enlisted below.
- Monitor Multiplexer
The Monitor Multiplexer acts as a 32:2 multiplexer.
- Single Pole Four Throw (SP4T)
The single pole four throw chassis is used in D47 PIU. The chassis is designed by using three broad band RF switch. The RF switch uses SW239 to realize the function.
This is used to select any one of the four active oscillator for further amplification in the power amplifier in D48 PIU
- Power Supply
The power supply is made up of an AC distribution panel and a DC distribution panel and both are employed for different purposes.
- D48 - Synthesizer
- Block Diagram
- Overall Lock Indicator
The Overall Lock Indicator is used to recognize the phase locking of the signal. The AD9696(U1 and U2) convert ECL output of reference and VCO-divided signals from the prescalar and the PFD module( at a frequency equal to step size, under lock) into TTL levels.
The monostable 74LS123 helps in a visual indication of the presence of these signals and helps in easy fault diagnosis.
- Temperature Monitor
The circuit is designed around Analog Device which provides an analog voltage of 5mV/degree K. It has got set of points, which could be used for WARN and SHUT purposes. Hysteresis has been provided in the IC to avoid jitter conditions at the set points.
Some important components used in Temperature Monitor are enlised below:
- Peregrine Prescalar
Peregrine's PE3236 is a high performance integer-N PLL capable of frequency synthesis up to 2.2 GHz. The superior phase noise performance of the PE3236 is ideal for applications such as LMDS / MMDS / WLL basestations and demanding terrestrial systems. The PE3236 features a 10/11 dual modulus prescaler, counters and a phase comparator . Counter values are programmable through either a serial or parallel interface and can also be directly hard wired. This programming flexibility, combined with the dual latch architecture enabling ping-pong loading of the main divide counter, makes these PLLs well suited as the core for fractional-N or sigma-delta implementation. The PE3236 is optimized for terrestrial applications. It is manufactured on Peregrine's UltraCMOS process, a patented variation of silicon-on-insulator (SOI) technology on a sapphire substrate, offering the performance of GaAs with the economy and integration of conventional CMOS.
- Isolated Amplifier
The Isolated Amplifier is kept into a single chassis along with a power divider and a Detector. The Isolation Amplifier is a stage of Avantek MSA 0520 (Cascadable Silicon Bipolar Amplifier) modamp preceded by suitable attenuators. The Circuit initially divides the power coming from the Power Amplifier in D48 PIU into three parts. One of them acts as a First LO Signal to the mixer in the IF system.The other ones are to be given to the Isolated Amplifier stage and the output of the Isolated Amplifier stage is given to to the dual modulus prescalar.
The Isolation Amplifier stage helps in reducing the reverse leakage components from a prescalar to the first LO port to the acceptable level.
- Single Pole Double Throw (SP2T)
The single pole Double throw chassis is used in D47 PIU. The chassis is designed by using single broad band RF switch. The RF switch uses SW239 to realize the function.
This is used to select any one of the four active oscillator for further amplification in the power amplifier in D48 PIU.
- Power Supply
The power supply is made up of an AC distribution panel and a DC distribution panel and both are employed for different purposes.
- Control
- Block Diagram
- Monitor Card
The Monitor Card is used to monitor the parameters of the Synthesizer System. Some important details are given below:
- Control Card
The Control Card is used for the control of the Synthesizer
- MCM Card
The total 16 MCMs can be supported at each antenna with address line from 0 to 15 and can be uniquely addressed by a software. The address of an MCM is selected through a DIP switch.
The MCM card provides 16 standard digital output bits for control purposes.
- WNG Card
The WNG card or Walsh and Noise Generation Control PCB is used in the D49 PIU. It is a part of the Monitoring scheme of the synthesizer as well as it controls a few parameters of the front end at the antenna. - Power Supply
The power supply is made up of an AC distribution panel and a DC distribution panel and both are employed for different purposes.
