Pin Diode Switch Schematic

There are many unique market applications such as the wireless communications market where new.

Pin diode switch schematic.

The pin diode makes an ideal rf switch. 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. 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. There is a 50 ohm coax from tx to antenna.

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 pin diode switch can be used for antennas with impedances of from 50 ω up to 75 ω. The signal to noise ration of the receiver deteriorates somewhat up to 1 db. 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.

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. This high impedance coax has an inner conductor with a diameter of 3 mm. Signal losses at the closed diode is negligible. References 1 2 provide a fuller treatment of this subject and can be used as a basis for rf switch switch driver.

The circuit uses back to back pin diodes in the paths from antenna to transmitter and again from antenna to receiver. For example the capacitance of an off state discrete pin diode might be 1 pf. Along this cable there are two t connections separated by one quarter wavelength. 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.

Schematic diagram of high power pin diode switch. The bias circuit typically uses a low pass filter between the rf circuit and the switch driver. The pin diode can be used as a high voltage rectifier. These biasing conditions are swapped to switch between transmit and receive.

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. At each t a high impedance quarter wave coax cable is connected. The intrinsic region provides a greater separation between the pn and n regions allowing higher reverse voltages to be tolerated.

It is really very straight forward. Figure 5 shows a single pole double throw spdt rf switch and its bias circuit. At 320 mhz the capacitive reactance of 1 pf is 497 ohms. 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 operated diodes block the disconnected antennas by about 30 db. The intrinsic layer between the p and n regions increases the distance between them.