A pin diode switch can switch much more quickly e g 1 microsecond although at lower rf frequencies it isn t reasonable to expect switching times in the same order of magnitude as the rf period.
Pin diode switch schematic.
Along this cable there are two t connections separated by one quarter wavelength.
Schematic diagram of high power pin diode switch.
Connecting the switch driver control circuit to a pin diode such that it can turn diodes on and off by applying a forward or reverse bias is a challenging task.
The pin diode makes an ideal rf switch.
References 1 2 provide a fuller treatment of this subject and can be used as a basis for rf switch switch driver.
The pin diode switch can be used for antennas with impedances of from 50 ω up to 75 ω.
It is really very straight forward.
The intrinsic layer between the p and n regions increases the distance between them.
It is primarily a function of the thickness of the i region and thicker diodes can operate down to 1 mhz while thinner ones can function into.
The operated diodes block the disconnected antennas by about 30 db.
Figure 5 shows a single pole double throw spdt rf switch and its bias circuit.
There are many unique market applications such as the wireless communications market where new.
This high impedance coax has an inner conductor with a diameter of 3 mm.
The signal to noise ration of the receiver deteriorates somewhat up to 1 db.
For example the capacitance of an off state discrete pin diode might be 1 pf.
At 320 mhz the capacitive reactance of 1 pf is 497 ohms.
The circuit uses back to back pin diodes in the paths from antenna to transmitter and again from antenna to receiver.
The bias circuit typically uses a low pass filter between the rf circuit and the switch driver.
At each t a high impedance quarter wave coax cable is connected.
One pair is biased to conduct in pin diode mode with forward current while the other is reverse biased with high voltage to the off or blocking condition.
Figure d 1 is a typical circuit and figure d 2 is the same circuit with.
There is a 50 ohm coax from tx to antenna.
Applying both rf and dc bias at the same time as can be seen in the diagram the rf is fed into and out of the diode through 0 01uf blocking capacitors.
These biasing conditions are swapped to switch between transmit and receive.
Driver circuits for high power pin diode switches the information in this chapter is presented as a guide for the rf switch switch driver interface.
Thus a pin diode is a dc controlled high frequency resistor and if no dc current is present the diode is just like an open circuit.
Chapter 2 the common pin diode switch configurations are presented followed by sections comparing those features of pin diode switch designs for unique to high power microwave switches and high power lower frequency rf band switches.
Take a look at the diagram below which is a schematic of a simple single pole single throw rf switch using a pin diode.
The pin diode can be used as a high voltage rectifier.
What is the frequency range of the pin diode as an rf switch.
