active phased antenna array
receiving and transmitting module
X-band power amplifier
V. А. Kolomejcev, А. V. Ezopov, A. E. Semenov
The article describes four basic problems of creating transceiver modules of active phased antenna arrays for X-band:
1. mutual influence of microwave components in a limited volume at an extra-dense installation;
2. control of the temperature of the active element;
3. stabilization of the thermal regime of the module during the measurement, adjustement, and calibration.
4. intensification of heat removal from the active element to the outer surface of the device.
The solution of the marked tasks will improve the performances of transmitting and receiving modules of X- band active phased antenna arrays.
Development of transceiver modules is complicated by severe restriction of dimensions. In active phased antenna arrays positions of emitters are determined by the wavelength. To minimize side lobes in the radiation pattern the distance between the radiators should be equal to half the wavelength. For X-band frequencies the lattice spacing is about 15 mm.
To solve the problem of electromagnetic compatibility it is proposed to use pulse-mode power supply not only for the transmitting channel, but also for the receiver. Supplying with the LNA is removed just before turning on the transmitter, and is served immediately after it is turned off. Interim clearances are about 40 – 50 ns. Also, in a pause formed, the amplitude and phase distribution of transmission and reception is changed. This study shows that at the small sizes of transceiver modules and technological difficulties of placing transmitting and receiving channels in separate radio-hermetical compartments, the introduction of the pulse operation of the receive channel allows one to eliminate the parasitic feedback and solve the problem of excitation of the transmitting channel.
The problem of non-contact temperature monitoring in the area of greatest heat load can be solved by using the temperature dependence of the mobility of charge carriers. The proposed approach allows one to control the temperature of the crystal amplifier without introducing any additional items, carry out adjustment of a gain, and when achieving the critical temperature, turn off the power amplifier before it fails due to overheating.
To solve the problem of module temperature stabilization for configuring and calibrating authors propose to use an adaptive algorithm for stabilization, taking into account the rate of temperature change. Derivative control allows you to choose such fan speed at which the challenged cooling heat flow is equal to the heat flow released by the module, regardless of its value. This method allows one to stabilize the temperature of measuring unit regardless of the operation mode, and the heat, because cooling system take as much heat as module allocates.
Remains open the problem of intensification of heat removal from the active region of the power amplifier output to the external surface of the module. Currently, the authors conducted a mathematical simulation of designs using thin plates of high thermal conductivity. This design should transform a point heat source to the surface one. Thus one is able to increase the effective cross section of the heat flow, which in turn significantly reduces the thermal resistance between the active region and the outer surface of the module.