ELECTRONIC AND AUTOMATIC SELECTOR DEVICE CONNECTED TO AN ANTENNA ARRAY FORMED BY TWO OR MORE ANTENNAS

• US 3,670,275 A
• Filed: 04/14/1970
• Issued: 06/13/1972
• Est. Priority Date: 03/20/1970
• Status: Expired due to Term

• Current Assignee: Kalevi Juhani Kalliomaki, Martti Eelis Tiuri, Seppo Matti Vakkila
• Original Assignee: Kalevi Juhani Kalliomaki, Martti Eelis Tiuri, Seppo Matti Vakkila
• Inventors: Kalliomaki, Kalevi Juhani, Tiuri, Martti Eelis, Vakkila, Seppo Matti
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/028,408
• Time in Patent Office: 791 Days
• Field of Search: 325/56,303,304,306,366,370,372 328/137 343/205,206
• US Class Current: 455/132
• CPC Class Codes: H04B 7/0808 comparing all antennas before reception

Abstract

An electronic automatic selecting device has an antenna array consisting of two or more antennas pointing in different directions for the purpose of selecting and connecting to a service receiver that antenna from which the desired radio signal is best obtained. The selection is carried out by a selecting device and a search receiver having a low frequency output, from which, when receiving a frequency modulated emission, a noise signal is obtained proportional to the S/N ratio of the signal received by the receiver. This signal steers the selecting device. In accordance with the present invention the selecting device includes a noise handling unit the input of which receives the noise voltage from the search receiver and the output of which is large when the search receiver receives a signal with a poor S/N ratio and small when the search receiver receives a signal with a good S/N ratio. There is a voltage-to-frequency converter the operating frequency of which is determined by the output voltage of the noise handling circuit, whereby the output frequency is high when the output voltage is large and is low when the output voltage is small, a pulse oscillator which oscillates at a constant frequency and which gives the search command, an electronic change-over switch which upon receiving the search command from the pulse oscillator, sequentially connects, steered by the voltage-to-frequency converter, the antennas of the antenna array to the search receiver, and which after sampling all antennas returns to zero. There is also a circuit for comparing the signals obtained from the various antennas to the input of which are fed the pulses from the voltage-to-frequency converter and the output of which produces a pulse when during a search cycle an antenna giving a signal with a better S/N ratio than any other antenna previously sampled during the search cycle is connected to the search receiver, and a memory circuit to the input of which is fed from a dividing circuit constituting a part of said electronic change-over switch, the number in binary form of each of the antennas connected to said search receiver during the search cycle. This binary number moves to the output of the memory circuit only when an output pulse is obtained from the signals comparing circuit. Finally there is an electronic switch controlled by said memory circuit and connecting the service receiver to that antenna of the antenna array from which the search receiver during the search cycle has received the signal with the best S/N ratio.

Claims

1. An electronic automatic selecting device for selecting an antenna with the best desired radio signal from an antenna array comprising a plurality of antennas pointing in different directions, two diode switch arrays connected with the antenna array, a search receiver connected with one of said diode switch arrays and having a low-frequency output producing a noise signal proportional to the S/N ratio of the received signal, and a selecting device comprising a noise handling unit having an input connected with the output of said search receiver, the output of said noise handling unit being large when said search receiver receives a signal with a poor S/N ratio and being small when said search receiver receives a signal with a good S/N ratio, a voltage-to-frequency converter connected with the output of said noise handling unit, the operating frequency of said converter being determined by the output voltage of said noise handling unit in that the output frequency is high when the output voltage is large and is low when the output voltage is small, a pulse oscillator connected in parallel with said voltage-to-frequency converter, said pulse oscillator oscillating at a constant frequency and giving the search command, a gate connected with said voltage-to-frequency converter, an electronic change-over switch connected with said gate and said one diode switch array, said change-over switch including a decade counter, means connecting said pulse oscillator to said decade counter, said change-over switch sequentially connecting the antennas of the antenna array to said search receiver and sampling the antennas, a signal comparator connected to the outlet of said voltage-tofrequency converter for comparing signals obtained from different antennas, a memory device connected with said decade counter, another gate connected with said signal comparator and said memory device, another electronic change-over switch connected with the other one of said diode switch arrays and said memory device, the output of said voltage-to-frequency converter producing a pulse when an antenna giving the best signal is connected to said search receiver, said memory device receiving a binary number from each of the antennas connected to said search receiver, the binary number moving to the output of said memory device only when an output pulse is obtained from said signal comparator, and a service receiver connected with said other diode switch array.

2. An electronic and automatic selecting device according to claim 1, characterized by the fact that the noise handling unit comprises a high-pass filter, the lower cutoff frequency of which is the highest modulation frequency, an amplifier, a linear rectifier, and a low-pass filter, the time constant of which is large for small changes of the noise voltage and small for large changes of the noise voltage, the time constant depending nonlinearly on the voltage.

3. An electronic and automatic selecting device according to claim 1, characterized by the fact that the first-mentioned electronic change-over switch is formed by said decade counter, a corresponding binary-to-decimal converter and, amplifiers.

4. An electronic and automatic selecting device according to claim 1, characterized by the fact that the signal comparator comprises an integrating circuit which integrates a constant voltage over the period time of the voltage-to-frequency converter, a peak rectifier working as a sequential comparator, an amplifier, and a pulse shaper.

5. An electronic and automatic selecting device according to claim 3, characterized by the fact that between the decade counter and the binary-to-decimal converter is inserted a change-over switch, which connects the decade counter directly to the binary-to-decimal converter during the search cycle, but which during the quiet period between search cycles connects the binary number, contained in the output of the memory circuit, to the first-mentioned electronic change-over switch of the search receiver, so that the search receiver is also connected to the corresponding antenna, which gives the strongest signal.

6. An electronic and automatic selecting device according to claim 5, characterized by the fact that the selecting device has been provided with an auxiliary logic, making it possible to use several service receivers (5), tuned to different frequencies, and one common search receiver (4), which for each service receiver in turn, seeks out that antenna which, at the respective frequency, gives the best signal, the auxiliary logic then comprises memory circuits (11) and electronic switches (14, 15, 3) for each of the service receivers (5), the decade counter (7) controlling all memory circuits (11) simultaneously, a first auxiliary change-over switch between the signal comparison unit (10) and the memory circuits (11), a second auxiliary change-over switch between the memory circuits (11) and the change-over switch (16) between the decade counter (7) and the binary-to-decimal converter (8), the operation of both of these auxiliary change-over switches being synchronized to the change-over switch changing the frequency of the search receiver (4), in such a manner that the memory pulse possibly received during each search cycle from the signal comparison unit (10) is fed to that memory (11), which controls that service receiver, which is tuned to the same frequency as the search receiver, it being then necesSary for the second auxiliary change-over switch to connect, for a short time prior to the search cycle, the number contained in the corresponding memory (11) to the electronic switch (8, 13, 2), so that the search receiver receives the strongest signal found at the frequency in question during the previous search cycle.

7. An electronic and automatic selecting device according to patent claim 5, characterized by the fact that the search receiver (4) is also used as the service receiver (5), the electronic switch (14, 15, 3) will then not be needed, but the pulse oscillator (POs) is replaced with another voltage-to-frequency converter (VFC2), which is controlled by the noide handling circuit (6) in such manner that when the receiver (4) receives a signal with a good S/N-ratio, the second voltage-to-frequency converter (VFC2) does not oscillate, and the receiver stays connected to the corresponding antenna, avoiding needless interruptions of the signal, but when the signal deteriorates the second voltage-to-frequency converter (VFC2) oscillates at a relatively small frequency, giving search commands to the electronic change-over switch (7, 8, 13, 2).

8. An electronic and automatic selecting device according to claim 7, characterized by the fact that, in order to increase the noise immunity of the selecting device, the memory circuit (11) has been augmented by a circuit, which ensures that the memory (11) changes its state only when the pulse from the signal comparison unit (10) has indicated the same antenna as being the best one during, e.g., two or three search cycles.

9. An electronic and automatic selecting device which, in connection with reception of a frequency modulated transmission, from an antenna array formed by two or more antennas pointing in different directions selects, and connects to the actual service receiver (5), that antenna from which the desired radio signal is best obtained, while to the same antenna array is further connected, for the purpose of selecting the correct antenna, with the aid of a selecting device, a search receiver (4), this selecting device comprising a. first switching means (VFC1, POs, 9, 7, 16, 8, 13, 2), which connect different antennas to the search receiver (4), one at a time;

b. a noise handling unit (6), the input of which is connected to the output of the search receiver (4) and which filters off the signal and of the noise remaining outside the information band forms a control voltage proportional to the signal/noise ratio of the signal received;

c. a memory and sequential comparison unit (VEC1,

     10), to the input of which the said control voltage is supplied and from the output of which an order pulse is obtained whenever the control voltage, while a given antenna is connected to the search receiver (4), presents a signal/noise ratio which is superior to those of the antennas previously sampled;

d. a memory circuit (11), to the input of which the information specifying the position of the first switching means is supplied, and to the output of which said information is always transferred when the sequential comparison unit gives the order pulse;

e. second switching means (11, 14, 15,

     3), which connect the service receiver (5) to the antenna specified by the output of the memory circuit (11), whereby the service receiver (5) will always be connected to the antenna giving the best signal/noise ratio.

10. An electronic and automatic selecting device according to claim 9, in which the first switching means (VFC1, POs, 7, 8, 13, 2, 9, 16) are formed by a decade counter (7), a corresponding binary-to-decimal converter (8), amplifiers (13), a diode switch array (2), a voltage-to-frequency converter (VFC1), a pulse oscillator (POs), a gate (9) and a selector switch (16).

11. An electronic and automatic selecting device according to claim 9, in which the memory and sequential comparison unit (VEC1, 10) comprises a voltage-to-frequency converter (VEC1), a peak rectifier (10b) operating as a sequential comparator, an amplifier (10c), and a pulse shaper (10d).